Somatostatin receptors

BIM 23014, Lanreotide, 100 nM; 0-48 h) increased the apoptosis caused by radiation[1]. GH3 cell colony forming units decrease in a dose-dependent manner after taking lanreotide. Cell survival rates are 75, 56, 39, and 27% at doses of 1, 10, 100, and 1000 nM of lanreotide, respectively. 57 nM is the IC50[1]. In vitro, lenreotide suppresses the growth and hormone release of pituitary adenoma cells that secrete growth hormone[2].

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Dose–responses of GH3 cells to Lanreotide and γ radiation [1]
As shown in Fig. 1A, treatment with Lanreotide resulted in a dose-dependent decrease in GH3 cell colony forming units. Lanreotide at doses of 1, 10, 100, and 1000 nM resulted in cell survival rates of 75, 56, 39 and 27% respectively. The IC50 (50% inhibition of cell growth) was 57 nM. The radiation survival curves are shown in Fig. 1B. GH3 cells had a typical radiation dose–response survival curve with an initial shoulder at doses below 5 Gy and a straight line at high dose. The SF at 2 Gy (SF2, a dose commonly used in daily fractionated radiotherapy) was 40%.

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Effect of Lanreotide on radiation response of GH3 cells [1]
GH3 cells were plated in tissue culture dishes overnight. The radiation survival curves are shown in Fig. 2. Treatment with Lanreotide alone at doses of either 100 or 1000 nM for 48 h without radiation reduced clonogenic survival compared with untreated controls by 5–10%. Radiation alone without lanreotide produced a dose-dependent survival curve with a SF2 of 48–55%. Treatment with lanreotide at a dose of 100 nM for 48 h either before (48 h prelanreotide and 24 h prelanreotide) or at the time of radiation (0 h prelanreotide) produced survival curves that were slightly shifted downward and separated at doses of 7–10 Gy from the survival curve produced by radiation alone without lanreotide (Fig. 2A) indicating that the radiation response of GH3 cells was enhanced by lanreotide. The SF at 10 Gy was 0.0006, 0.00022, 0.00040, and 0.00042 respectively, for radiation alone, 48 h pre-, 24 h pre- and 0 h pre-exposure to lanreotide (Fig. 2C). However, treatment with 1000 nM lanreotide did not alter the shape and slopes of the radiation survival curves, indicating there was no radioprotection (or radiosensitization) effect under these experimental conditions (Fig. 2B).

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Effect of Lanreotide and radiation on apoptosis and cells cycle distribution [1]
The percentage of cells in sub-G1, G1, S, and G2/M phases at 48 h was 1.4±0.2, 73.2±1.0, 8.4±1.0, and 16.9±1.8% respectively. Treatment with 100 nM Lanreotide alone resulted in the sub-G1, G1, S, and G2/M phase distribution of 2.28±0.3, 73.8±1.1, 7.72±0.8, and 16.2±0.5% respectively, indicating that the cell cycle profile was not significantly affected by treatment with lanreotide compared with the untreated control, except for a moderate increase in apoptotic sub-G1 cells from 1.4 to 2.28%. Treatment with 10 Gy radiation resulted in a decrease in the proportion of cells in G1 phase from 73.2 to 51.5% at 48 h. Meanwhile, the G2/M phase cells increased from 16.9% before radiation to 35.7% at 48 h after irradiation, and cells were arrested at G2/M phase for up to 168 h without release. The subdiploid cell population, representing apoptotic cells, increased steadily following radiation from a baseline of 1.4% to a peak of ∼12% at 168 h (Fig. 3). Combined treatment of GH3 cells with radiation and lanreotide produced a cell cycle profile that was similar to that seen in irradiated cells without lanreotide, except for the increase in apoptotic sub-G1 proportion. As shown in Fig. 3, at 48 h after irradiation, the apoptotic sub-G1 cells increased from 4.9% for radiation alone to 8.6, 9.3, and 13.4% for the combination of radiation with 48, 24, and 0 h pre-exposure of lanreotide respectively, representing an increase of 77–173% compared with radiation alone (P<0.01). At 168 h after radiation, the sub-G1 cell fraction was 12% for radiation alone and 20–22% for radiation plus lanreotide, representing an increase of 67–83% (P<0.01).

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All the adenomas analysed expressed at least one somatostatin receptor subtype mRNA. SSTR2 mRNA was identified in 77% of the adenomas, SSTR1 and SSTR3 in 69% and SSTR5 in 60%. Somatostatin and Lanreotide inhibited cell proliferation in phorbol ester (PMA)-stimulated conditions (10/13 adenomas), as well as after fetal calf serum (3/3 adenomas) or IGF-I stimulation (2/2 adenomas). Conversely, GHRH or forskolin treatments did not significantly affect DNA synthesis in adenoma cells in the presence or absence of somatostatin (2/2 and 4/4 adenomas, respectively). Vanadate pretreatment reversed somatostatin inhibition of PMA-induced DNA synthesis suggesting an involvement of tyrosine phosphatase in this effect (2/2 adenomas); this was confirmed by the direct induction of tyrosine phosphatase activity in two adenomas after somatostatin treatment. Somatostatin and also lanreotide caused significant inhibition of phorbol ester, forskolin, GHRH and KCl-dependent increase of GH secretion in the culture medium. Moreover, voltage-sensitive calcium channel activity induced by 40 mm KCl depolarization in microfluorimetric analysis, was significantly reduced (5/5 adenomas).
Conclusions: These data show that somatostatin and Lanreotide inhibit human GH-secreting pituitary adenoma cell proliferation and hormone release in vitro, and suggest that the activation of tyrosine phosphatases may represent intracellular signals mediating the antiproliferative effects and that the inhibition of the voltage-dependent calcium channels and adenylyl cyclase activities may control GH secretion [2].

Tumor growth inhibition occurs when Lanreotide (2.5–10 mg/kg; sc; daily for 5 days) is administered[1].

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Dose–responses of GH3 tumors to Lanreotide [1]
Groups of nude mice with established GH3 xenograft tumors were treated subcutaneously with 2.5, 5, 10, 20, or 50 mg/kg Lanreotide daily for 5 days. Doses were based on prior studies utilizing lanreotide administration in vivo (Prevost et al. 1994, Melen-Mucha et al. 2004). As shown in Fig. 4, there was a bell-shaped dose dependent effect of lanreotide on GH3 tumor growth, with a narrow range of optimal doses. The maximum tumor growth inhibition (i.e. the longest TGD time of 13.1±4.7 days) occurred with a daily lanreotide dose of 10 mg/kg. When the daily lanreotide dose was either higher (i.e. 20 and 50 mg/kg) or lower (2.5 and 5 mg/kg) than 10 mg/kg, the effects of lanreotide on GH3 tumor growth were diminished.

In these studies, Lanreotide at all doses tested did not cause significant decrease in body weight compared with untreated control mice (data not shown). Also, there was no notable change in the general appearance and daily activity of tumor-bearing mice treated with lanreotide.

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Comparison of Lanreotide dose regimen of once daily versus twice daily [1]
To determine the importance of lanreotide dose regimen on tumor growth, we compared tumor size after single daily dose (qd) and two doses daily (bid). GH3 tumor-bearing nude mice were injected s.c. with lanreotide at doses of 2.5, 5 or 10 mg/kg for 5 days either once daily or twice daily (8 h interval). As shown in Fig. 5, there were no statistically significant differences between groups treated either once daily or twice daily at the same dose (P=0.3–0.9). However, lanreotide at 10 mg/kg once daily produced the longest TGD time (4.9±2.1 days) of all dose regimens studied (P<0.05). Notably, this was longer than that (1.1±3.1 days) following 5 mg/kg twice daily. Analogously, a single daily dose of 5 mg/kg qd produced a longer TGD time than did 2.5 mg/kg bid. These data suggest that a single dose of Lanreotide produced at least as much tumor growth inhibition than a fractionated dose regimen at the same total daily dose. Therefore, further studies utilized the single daily dosing regimen.

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Combination therapy of Lanreotide and fractionated radiation [1]
To study the effect of lanreotide on tumor responses to radiation therapy, nude mice with established GH3 tumors were treated with: 1) 10 mg/kg lanreotide daily for 5 days; 2) local tumor radiation daily for 5 consecutive days at doses of 250, 200, or 150 cGy/fraction per day; 3) a combination of Lanreotide and local tumor radiation as above; or 4) a s.c. injection of normal saline (0.005 ml/g body weight) daily as an untreated control. In combination therapy, lanreotide was injected 20 min before radiation. Data are shown in Fig. 6 (tumor growth curves). Lanreotide alone at a dose of 10 mg/kg moderately inhibited the growth of GH3 tumors, with a 4× TGD time that ranged from 4.5 to 8.3 days (P=0.3–0.06, compared with the relevant control groups). Fractionated local tumor radiation alone significantly inhibited tumor growth and produced TGD times of 35.1±5.7 days for 250 cGy fractions, 21.7±5.5 days for 200 cGy fractions, and 16.7±1.7 days for 150 cGy fractions respectively. The combination of lanreotide with radiation of 250, 200, or 150 cGy/fraction for 5 days inhibited tumor growth and produced the TGD times that were similar to radiation alone (P>0.05). Also, the combined treatment of lanreotide and fractionated radiation did not cause any further decrease in animal body weight compared with fractionated radiation therapy alone.

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Preadministration of Lanreotide in combination with radiation therapy [1]
To study whether preadministration of Lanreotide could modulate radiation effects on tumor growth, nude mice with GH3 xenograft tumors were treated with: 1) 10 mg/kg lanreotide daily for 10 days; 2) 150 cGy local tumor radiation daily for 5 consecutive days; and 3) 10 mg/kg lanreotide for 5 days followed by combined administration of lanreotide and 150 cGy radiation daily for 5 days. A group of tumor-bearing mice that was injected s.c. with normal saline daily for 10 days was also included as an untreated control. As shown in Fig. 7, lanreotide at a dose of 10 mg/kg for 10 days moderately inhibited tumor growth (4× TGD, 8.3±8.3 days, P=0.06 versus control). Local tumor radiation of 150 cGy inhibited tumor growth and gave a TGD time of 15.5.0±8.8 days (P<0.05 versus control and lanreotide alone). The combination therapy of preadministration of lanreotide and radiation in this treatment regimen resulted in a TGD time of 15.1±8.6 days, similar to that produced by radiation therapy alone (15.5±8.8 days; P>0.05). There were two mice with complete regression of tumors in both radiation alone and combination therapy groups, without tumor regrowth when the study was terminated after 60 days. Furthermore, lanreotide alone and in combination with radiation did not produce any obvious signs of systemic toxicity in terms of the loss of body weight, general appearance, skin reaction or activity level of the mice (data not shown).

Apoptosis Analysis[1]
Cell Types: GH3
Tested Concentrations: 100 nM
Incubation Duration: 48 h, 24 h, or immediately (0 h) before radiation
Experimental Results: Increased apoptotic sub-G1 proportion compared with radiation alone.

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In vitro clonogenic assay [1]
The dose–response of GH3 cells to the treatment of both Lanreotide and radiation was characterized using a clonogenic assay. GH3 cells were detached with 0.05% trypsin-EDTA solution, counted and plated in 60 mm Petri dishes at appropriate dilutions of 100–100 000 cells/dish in triplicate in fresh growth media. Lanreotide was added to the plates at final concentrations of 0–1000 nM. Cells were irradiated with 0–10 Gy at room temperature using a 137Cs source with a dose rate of 300 cGy/min. Following exposure to lanreotide or γ radiation, the media was removed, and dishes were washed twice with PBS solution and filled with fresh growth media. After incubation at 37 °C for 21 days, cells were stained with 0.25% crystal violet. Colonies containing ≥50 cells were counted under a dissecting microscope and survival curves were generated. The plating efficiency (PE) was calculated as the percentage of cells plated that grew into colonies. The surviving fraction (SF) was defined as the fraction of cells surviving an intervention, i.e. number of colonies/(number of colonies plated×PE). [1]
For the irradiation experiments, Lanreotide at final concentrations of 100 or 1000 nM (determined by experiments shown in Fig. 1) was added at 48, 24, or 0 h before radiation. Cells were irradiated with 0–10 Gy in the presence of lanreotide at room temperature with a Cs-137 γ irradiator. Following radiation, cells with 24 h or 0 h pre-exposure to lanreotide were incubated in lanreotide-containing media for an additional 24 or 48 h respectively. After a total of 48 h exposure, lanreotide-containing media was removed, and dishes were washed twice with PBS solution and then filled with fresh growth media. Dishes that were irradiated without lanreotide exposure were also washed twice with PBS and refilled with fresh media. Cells were incubated for 21 days for colony formation.

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Apoptosis and cell cycle analysis [1]
GH3 cells were placed in 60 mm Petri dishes (500 000 cells/dish) and grown overnight. Lanreotide at 100 nM was added at 48 h, 24 h, or immediately (0 h) before radiation. Cells were irradiated with 10 Gy γ radiation at room temperature. Cells were collected 48, 72, 96, and 168 h after irradiation, and washed with cold PBS plus 5 mM EDTA. Cells were resuspended in cold PBS–EDTA solution and fixed with cold 100% ethanol. After incubation for 30 min at room temperature, cells were pelleted and treated with 100 μg/ml of RNase A in PBS-EDTA solution for 30 min at room temperature. Propidium iodide (PI) was added to a final concentration of 50 μg/ml. The DNA content was analyzed with a FACScan flow cytometer. The percentage of cells in the sub-G1 (apoptotic), G1, S, and G2/M phases was calculated. Control cells without any treatment showed a consistent cell cycle distribution within 168 h (data not shown).

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Cell treatment [2]
GH-secreting adenoma cells were plated at the density of 1 × 105 in 24-well plates. After 24 h, cells were serum- and growth factor-starved for 24 h. Subsequently, cells were treated with the test substances for 16 h. At the end of the incubation time, in some cases when a small amount of cells were available, an aliquot of the medium was removed for GH determination and then 2 µCi/ml of [3H]-thymidine were added for 4 h before the proliferation assay. However, when possible independent treatments for cell proliferation and GH release were performed.

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Proliferation assay [2]
DNA synthesis activity was measured by means of the [3H]-thymidine uptake assay as previously reported (Florio et al., 1992). Briefly, cells, treated as indicated, were trypsinized (15 min at 37 °C), extracted in 10% trichloroacetic acid (TCA) and filtered under vacuum through fibreglass filters. The filters were then washed sequentially, under vacuum with 10% and 5% TCA and 95% ethanol. The TCA insoluble fraction was then counted in a scintillation counter.

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In vitro GH release measurement [2]
GH was measured by commercial immunoradiometric assay as previously reported (Giusti et al., 2002). Media from cell cultures were diluted from 1 : 10 to 1 : 100 in phosphate-buffered saline (PBS) buffer to allow better evaluation of GH content. All samples from the same experiment were measured in the same assay. The results are expressed as µg/well. Absolute and percent variation from control data are reported as mean ± SEM.

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PTP assay [2]
Cells, plated at 50% confluence in 6-cm Petri dishes, were preincubated with the test substances for 1 h in FCS-free medium at 37 °C in a CO2 incubator. Then the cells were washed with PBS and mechanically scraped in a buffer containing 0·32 m sucrose, 10 mm Tris, pH 7·5, 5 mm EGTA, 1 mmol/l EDTA and sonicated. Cell lysate was then centrifuged at 15 000 g at 4 °C for 60 min, resuspended in a buffer containing 250 mm HEPES, pH 7·2, 140 mm NaCl, 1% NP40 and phenylmethylsulphonyl fluoride (PMSF) and leupeptin as protease inhibitors, and assayed for protein content using the method of Bradford (1976) with bovine serum albumin as standard and the Bio-Rad reagent. Twenty micrograms of control or treated membranes were used in the PTP assay. PTP assay was performed using the synthetic substrate para-nitro-phenylphosphate (p-Npp) in a spectrophotometric assay. p-Npp is a general phosphatase substrate that in presence of inhibitors of Ser/Thr phosphatases is specific for PTPs (Pan et al., 1992). Membranes were preincubated for 5 min at 30 °C in 80 µl volume containing 20 µl of a 5× reaction buffer [250 mm HEPES, pH 7·2, 50 mm dithiothreitol (DTT), 25 mm EDTA, and 500 nm microcystin–leucine–arginine, Alamone Laboratories, Jerusalem Israel, as a Ser/Thr phosphatases inhibitor]. The reaction was started by adding 20 µl of 50 mmp-Npp, carried out for 30 min at 30 °C and stopped by adding 900 µl of 0·2 N NaOH. The absorbance of the sample, directly proportional to the amount of dephosphorylated substrate, was measured at 410 nm. The extinction coefficient for p-Npp, at this wavelength is 1·78 × 104m/cm.

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Measurement of intracellular calcium concentrations at single-cell level [2]
Cells were plated on 25-mm clean glass coverslips, previously coated with poly-l-lysine (10 µg/ml) and transferred to a 35-mm Petri dishes. After 24–48 h cells were serum-starved for further 24 h. On the day of the experiment the cells were washed for 10 min with a balanced salt solution (HEPES 10 mm, pH 7·4; NaCl 150 mm; KCl 5·5 mm; CaCl2 1·5 mm; MgSO4 1·2 mm; glucose 10 mm). Then adenomatous cells were loaded with Fura-2 penta-acetoxymethyl ester (4 µm) for 60 min at room temperature. Fluorescence measurements were performed as previously reported (Florio et al., 1999b). Briefly, coverslips were mounted on a coverslip chamber and fura-2 fluorescence was imaged with an inverted Nikon diaphot microscope using a Nikon 40X/1·3 NA Fluor DL objected lens. Cells were illuminated with a Xenon lamp with quartz collector lenses. A shutter and a filter wheel containing the two different excitation filters (340 nm and 380 nm) were controlled by computer. Emitted light was passed through a 400-nm dichroic mirror, filtered at 490 nm and collected by CCD camera connected with a light intensifier. Images were digitalized and averaged in an image processor connected to a computer equipped with the Quanticell software. For the calibration of fluorescence signals, we used cells loaded with Fura-2; Rmax and Rmin are ratios at saturating and zero [Ca2+]i, respectively, and were obtained perfusing the cells with a salt solution containing CaCl2 (10 mm), digitonin (2·5 µm) and ionomycin (2 µm) and subsequently with a Ca2+-free salt solution containing EGTA (10 mm). The values of obtained Rmax and Rmin, expressed as grey level mean, were used to calculate the intracellular Ca2+ concentration ([Ca2+]i), using the Quanticell software, according to the equation of Grynkiewicz et al. (1985).

Animal/Disease Models: Male nude mice, 8 weeks old and 20–25 g in body weight (GH3 tumor-bearing nude mice) [1]
Doses: 2.5, 5, 10 mg/kg
Route of Administration: Subcutaneous; daily for 5 days
Experimental Results: Produced tumor growth inhibition.

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Mouse xenograft tumor model and therapy [1]
Male nude mice, 8 weeks old and 20–25 g in body weight were tested and found to be negative for specific pathogens. The mice were normally bred and maintained under specific pathogen-free conditions, and sterilized food and water were available ad libitum. Mice were injected subcutaneously in the right flank with 5×106 tumor cells in 100 μl of a Hank's solution and Matrigel 1:1 mixture. One tumor per mouse was inoculated. When tumors reached an average size of 120 mm3 (80–200 mm3), mice were randomly assigned to the different treatment groups. Five to eight mice were used in each group. Lanreotide was injected s.c. at doses specified in each experiment. For radiation, the unanesthetized tumor-bearing mice were placed in individual lead boxes with tumors protruding through a cutout window at the rear of each box. The radiation was delivered using a Philips RT-250 200 kVp X-ray unit (12.5 mA; half value Layer, 1.0-mm Cu) at a dose rate of 138 cGy/min. Tumors were locally irradiated with a dose of 150–250 cGy per fraction daily for 5 consecutive days as specified in each experiment. The length and width of the tumors were measured with calipers before treatment by the same investigator, and three times a week thereafter until the tumor volume reached at least four times (4×) the pretreatment volume. The tumor volume was calculated using the formula: tumor volume (mm3)=π/6×length×width2. The tumor volume quadrupling (4×) time was determined by a best-fit regression analysis. The tumor growth delay (TGD) time (in days) is the difference between the tumor volume quadrupling time of treated tumors compared with that of untreated control tumors. Both the tumor volume quadrupling time and TGD time were calculated for each individual animal and then averaged for each group. In some experiments, a complete regression of tumors was recorded if a tumor completely shrunk to the point that it was not palpable at the end of the experiment. Body weight was measured twice a week.

Absorption, Distribution and Excretion
Lanreitide forms a drug reservoir at the injection site; therefore, lanreitide absorption occurs in two phases: 1. During the first few days of treatment, the drug is rapidly released subcutaneously, and unprecipitated drug is quickly absorbed. 2. The drug is slowly released from the reservoir via passive diffusion. Absorption is independent of body weight, sex, and dosage.
5% of lanreitide is excreted in the urine, and less than 0.5% is excreted unchanged in the feces, suggesting bile excretion is involved.
Estimated volume of distribution = 15.1 L
Estimated clearance = 23.1 L/h
Biological half-life The half-life is approximately 22 days.

Hepatotoxicity
In the pre-registration studies of lanreotide, no significant changes in serum enzyme levels were observed, and no clinically significant acute liver injury was reported. Pooled analyses showed no overall changes in serum ALT, AST, or alkaline phosphatase levels during treatment, and no clinically significant elevations were observed. As with other somatostatin analogs, long-term treatment with lanreotide is associated with a higher incidence of biliary sludge and gallstones, likely due to inhibition of gallbladder contraction and reduced bile secretion. In long-term studies, gallstones occurred in 20% to 33% of patients treated with lanreotide. In some cases, symptomatic cholecystitis occurred, possibly accompanied by mild to moderate elevations in serum enzymes and bilirubin. However, most lanreotide-related gallstones are asymptomatic. Unlike octreotide, lanreotide and other long-acting somatostatin analogs have not been reported to be associated with clinically significant liver injury cases, regardless of the presence of gallstones or biliary sludge. Although their use is more limited and not in many clinical conditions where octreotide has been used to treat (e.g., portal hypertension, esophageal variceal bleeding, and children with congenital hyperinsulinemia). Probability Score: E (Unproven, but suspected as a rare cause of clinically significant hepatobiliary damage). Pregnancy and Lactation Effects ◉ Overview of Lactation Use Lanreotide has not been studied for excretion into breast milk. However, due to its high molecular weight of 1096 Daltons, it may be difficult to excrete into breast milk, and as a peptide drug, it is likely to be digested in the infant's gastrointestinal tract, making it unlikely to reach clinically significant concentrations in infant serum. Lanreotide has been used by injection to treat newborns with congenital hyperinsulinemia; some infants have experienced reversible, mild elevations in liver enzymes. The manufacturer notes that women should not breastfeed during treatment with long-acting lanreotide and for 6 months after the last dose.
◉ Effects on Breastfed Infants
A woman with acromegaly received lanreotide sustained-release gel 120 mg monthly, cabergoline 2 mg weekly, and pevisolemon 80 mg weekly. She breastfed her infant (feeding extent not specified) and followed him for 12 years. Her child's growth and development were normal.
◉ Effects on Lactation and Breast Milk
As of the revision date, no relevant published information was found.

[1]. Lanreotide promotes apoptosis and is not radioprotective in GH3 cells.Endocr Relat Cancer. 2009 Sep;16(3):1045-55.

[2]. Characterization of the intracellular mechanisms mediating somatostatin and lanreotide inhibition of DNA synthesis and growth hormone release from dispersed human GH-secreting pituitary adenoma cells in vitro.Clin Endocrinol (Oxf). 2003 Jul;59(1):115-28.

Lanreotide acetate is the acetate of a cyclic octapeptide analog of somatostatin. Lanreotide binds to the somatostatin receptor (SSTR), particularly SSTR-2, and also to SSTR-5, but with lower affinity. However, compared to octreotide, it has a weaker ability to inhibit the release of growth hormone from the pituitary gland. Furthermore, lanreotide rapidly reduces the levels of both total and free insulin-like growth factor 1 (IGF-I) in circulation. It is typically administered in the form of extended-release microparticles or Autogel formulations for the treatment of acromegaly and the relief of symptoms from neuroendocrine tumors.
See also: Lanreotide (note moved to) Lanreotide acetate (note moved to).

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Lanreotide is a drug used to treat acromegaly, a hormonal disorder caused by excessive growth hormone, and symptoms from neuroendocrine tumors, particularly carcinoid syndromes. It is a long-acting analog of the growth hormone inhibitor, somatostatin. Lanreotide, manufactured by Ipsen Pharmaceuticals, is marketed under the brand name Lanreotide Acetate and also under the brand name Somatuline. It has been approved in several countries worldwide, including the UK, Australia, and Canada. Lanreotide was first approved by the US Food and Drug Administration (FDA) on August 30, 2007. Lanreotide is a synthetic somatostatin peptide analog that inhibits the levels and activity of growth hormone, insulin, glucagon, and many other gastrointestinal peptides with similar ability to natural hormones. Due to its longer half-life than somatostatin, lanreotide is clinically used to treat neuroendocrine tumors that secrete excessive growth hormone (acromegaly) or other active hormones or neuropeptides. Lanreotide has several side effects, including inhibition of gallbladder contraction and bile secretion; maintenance therapy may lead to gallstones and pancreatitis, accompanied by liver damage. Lanreotide is a synthetic cyclic octapeptide analog of somatostatin. Lanreotide binds to the somatostatin receptor (SSTR), particularly SSTR-2, and also to SSTR-5, but with lower affinity. However, compared to octreotide, lanreotide has a weaker ability to inhibit the release of growth hormone from the pituitary gland. Furthermore, lanreotide can rapidly reduce the levels of both total and free insulin-like growth factor 1 (IGF-I) in circulation. This drug is typically administered in the form of sustained-release microparticles or Autogel formulations for the treatment of acromegaly and the relief of symptoms from neuroendocrine tumors. Lanreotide acetate is the acetate of a somatostatin synthetic cyclic octapeptide analog. Lanreotide binds to somatostatin receptors (SSTRs), particularly SSTR-2, and also to SSTR-5, but with lower affinity. However, compared to octreotide, this drug has a weaker ability to inhibit the release of growth hormone from the pituitary gland. Furthermore, lanreotide can rapidly reduce the levels of both total and free insulin-like growth factor 1 (IGF-I) in circulation. This drug is typically administered in the form of sustained-release microparticles or Autogel formulations for the treatment of acromegaly and the relief of symptoms from neuroendocrine tumors. See also: Lanreotide acetate (in salt form).

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Drug Indications
Lanreotide is indicated for the long-term treatment of acromegaly in patients who have not responded well to or are ineligible for surgery and/or radiation therapy. It is also indicated for the treatment of adult patients with unresectable, well-differentiated or moderately differentiated, locally advanced or metastatic gastropancreatic neuroendocrine tumors (GEP-NETs) to improve their progression-free survival. Lanreotide is also indicated for the treatment of adult cancer syndromes—using this drug can reduce the frequency of short-acting somatostatin analogue salvage therapy.
FDA Label
Treatment of acromegaly, treatment of gastrointestinal fistulas, treatment of peritoneal metastases, treatment of pituitary gigantism, treatment of pituitary tumors

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Mechanism of Action
Lanreotide is a somatostatin analogue (SSA) that exerts its inhibitory effect primarily through somatostatin receptors (SSTRs) 2 and 5, including the inhibition of growth hormone release in the brain. Tumor SSTR activation can induce downstream cell cycle arrest and/or apoptosis, leading to a reduction in the production of substances supporting tumor growth and angiogenesis. This explains the antiproliferative effect of lanreotide. Somatostatin analogues are the main drugs for treating growth hormone (GH)-secreting human pituitary tumors, and studies have shown that somatostatin analogues may have radioprotective effects. We used GH-secreting rat GH3 cells to investigate whether somatostatin analogues could limit the effects of radiation on cell proliferation and apoptosis in vitro and on tumor growth in vivo. Treatment with lanreotide alone (at doses of 100 nM or 1000 nM) for 48 hours reduced colony formation survival by 5-10%. Irradiation alone produced dose-dependent survival curves, with SF2 showing 48-55%, while lanreotide had no effect on this curve. After the addition of lanreotide, the proportion of apoptotic sub-G1 phase cells increased by 23% after irradiation (P<0.01). In a mouse xenograft model of GH3 tumors, lanreotide 10 mg/kg moderately inhibited the growth of GH3 tumors, with a tumor growth delay (TGD) of 4 times in the range of 4.5 to 8.3 days. Local fractionated radiotherapy alone significantly inhibited tumor growth, with a TGD of 35.1 ± 5.7 days at 250 cGy/fraction. Lanreotide combined with radiotherapy at 250, 200, or 150 cGy/fraction for 5 consecutive days (whether before or during radiotherapy) inhibited tumor growth, and the TGD was similar to that of radiotherapy alone (P>0.05). Lanreotide pretreatment had the most significant radiosensitizing effect. These studies indicate that the somatostatin analog lanreotide has no radioprotective effect on GH3 cells, and further research is needed to determine the effect of lanreotide on apoptosis. [1] In summary, we demonstrated using a mouse xenograft model that the somatostatin analog lanreotide does not protect pituitary tumor cells from ionizing radiation, but it can promote radiation-induced apoptosis of rat GH3 cells. Further in vitro and in vivo studies are needed to determine the potential clinical implications of these findings for the treatment of patients with neuroendocrine tumors such as acromegaly, and whether somatostatin analogues should be used concurrently with radiotherapy. These preliminary results also suggest that lanreotide may enhance radiation-induced apoptosis, warranting further investigation. In addition, further studies are needed to elucidate the potential synergistic mechanism of lanreotide and radiation in inducing apoptosis. [1] Objective: Somatostatin is an inhibitor of endogenous hormone secretion and cell proliferation. In humans, treatment with somatostatin analogues reduces the volume and secretory activity of endocrine tumors, including growth hormone-secreting pituitary adenomas. This study aims to elucidate the intracellular mechanism of the in vitro antiproliferative and antisecretive effects of somatostatin and its analogue lanreotide on primary cultured cells of growth hormone (GH)-secreting pituitary adenomas. Design: The expression of somatostatin receptor (SSTR) mRNA in 13 postoperative specimens of GH-secreting pituitary adenomas was analyzed, and a subset of these specimens were analyzed in vitro to assess the effects of somatostatin on cell proliferation (assessed by [3H]-thymidine uptake) and GH release (assessed by immunoradioassay). In addition, intracellular signaling pathways involved in these effects were investigated. [2] In summary, our data suggest that in vitro activation of SSTR by somatostatin or lanreotide in GH-secreting adenoma cells leads to a reduction in both DNA synthesis and GH secretion. This effect is associated with an increase in phosphotyrosine phosphatase (PTP) activity, resulting in an antiproliferative effect, and with an inhibition of voltage-dependent calcium channel activity, resulting in an antihormonal effect. These effects may be intracellular effector factors activated by SSTR in pituitary adenoma cells. [2]

C54H69N11O10S2.C2H4O2

1156.37532

1155.488

127984-74-1

108736-35-2;127984-74-1 (acetate);

71349

{d-2nal}-Cys-Tyr-{d-Trp}-Lys-Val-Cys-Thr-NH2 (Disulfide bridge: Cys2-Cys7); H-DL-2Nal-DL-Cys(1)-DL-Tyr-DL-Trp-DL-Lys-DL-Val-DL-Cys(1)-DL-xiThr-NH2; 3-(2-naphthyl)-DL-alanyl-DL-cysteinyl-DL-tyrosyl-DL-tryptophyl-DL-lysyl-DL-valyl-DL-cysteinyl-DL-threoninamide (2->7)-disulfide

XCYWKVCX; {d-2nal}-CY-{d-Trp}-KVCT-NH2 (Disulfide bridge: Cys2-Cys7)

White to off-white solid powder

2.5

13

14

17

77

2000

0

CC([C@H]1C(N[C@H](C(N[C@H](C(N)=O)[C@H](O)C)=O)CSSC[C@H](NC([C@H](N)CC2=CC3=CC=CC=C3C=C2)=O)C(N[C@H](C(N[C@@H](C(N[C@H](C(N1)=O)CCCCN)=O)CC4=CNC5=CC=CC=C45)=O)CC6=CC=C(O)C=C6)=O)=O)C.CC(O)=O

LKOFLENOEWIRAG-NSBHJRQQSA-N

InChI=1S/C56H71N11O11S2/c1-30(2)47-56(77)65-46(55(76)67-48(31(3)68)49(59)70)29-80-79-28-45(64-50(71)40(58)24-34-16-19-35-11-5-6-12-36(35)23-34)54(75)62-43(25-33-17-20-38(21-18-33)78-32(4)69)52(73)63-44(26-37-27-60-41-14-8-7-13-39(37)41)53(74)61-42(51(72)66-47)15-9-10-22-57/h5-8,11-14,16-21,23,27,30-31,40,42-48,60,68H,9-10,15,22,24-26,28-29,57-58H2,1-4H3,(H2,59,70)(H,61,74)(H,62,75)(H,63,73)(H,64,71)(H,65,77)(H,66,72)(H,67,76)/t31-,40-,42+,43+,44-,45-,46-,47+,48+/m1/s1

(4S,7S,10S,13R,16S,19S)-13-((1H-indol-3-yl)methyl)-19-((R)-2-amino-3-(naphthalen-2-yl)propanamido)-N-((2S,3R)-1-amino-3-hydroxy-1-oxobutan-2-yl)-10-(4-aminobutyl)-16-(4-hydroxybenzyl)-7-isopropyl-6,9,12,15,18-pentaoxo-1,2-dithia-5,8,11,14,17-pentaazacycloicosane-4-carboxamide acetate

trade name: Somatuline; Lanreotide; Lanreotide acetate; 127984-74-1; 10-(4-Aminobutyl)-19-[(2-amino-3-naphthalen-2-yl-propanoyl)amino]-N-(1 -carbamoyl-2-hydroxy-propyl)-16-[(4-hydroxyphenyl)methyl]-13-(1H-indol -3-ylmethyl)-6,9,12,15,18-pentaoxo-7-propan-2-yl-1,2-dithia-5,8,11,14, 17-pentazacycloicosane-4-carboxamide; 10-(4-aminobutyl)-N-(1-amino-3-hydroxy-1-oxobutan-2-yl)-19-[(2-amino-3-naphthalen-2-ylpropanoyl)amino]-16-[(4-hydroxyphenyl)methyl]-13-(1H-indol-3-ylmethyl)-6,9,12,15,18-pentaoxo-7-propan-2-yl-1,2-dithia-5,8,11,14,17-pentazacycloicosane-4-carboxamide; Angiopeptin acetate; Ipstyl; BIM 23014; Somatulin; Lanreotide Autogel; Lanreotide acetate.

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

May dissolve in DMSO (in most cases), if not, try other solvents such as H2O, Ethanol, or DMF with a minute amount of products to avoid loss of samples

Note: Listed below are some common formulations that may be used to formulate products with low water solubility (e.g. < 1 mg/mL), you may test these formulations using a minute amount of products to avoid loss of samples.

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Injection Formulation 1: DMSO : Tween 80： Saline = 10 : 5 : 85 (i.e. 100 μL DMSO stock solution → 50 μL Tween 80 → 850 μL Saline)
*Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH ₂ O to obtain a clear solution.
Injection Formulation 2: DMSO : PEG300 ：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL DMSO → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)
Injection Formulation 3: DMSO : Corn oil = 10 : 90 (i.e. 100 μL DMSO → 900 μL Corn oil)
Example: Take the Injection Formulation 3 (DMSO : Corn oil = 10 : 90) as an example, if 1 mL of 2.5 mg/mL working solution is to be prepared, you can take 100 μL 25 mg/mL DMSO stock solution and add to 900 μL corn oil, mix well to obtain a clear or suspension solution (2.5 mg/mL, ready for use in animals).

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Injection Formulation 4: DMSO : 20% SBE-β-CD in saline = 10 : 90 [i.e. 100 μL DMSO → 900 μL (20% SBE-β-CD in saline)]
*Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.
Injection Formulation 5: 2-Hydroxypropyl-β-cyclodextrin : Saline = 50 : 50 (i.e. 500 μL 2-Hydroxypropyl-β-cyclodextrin → 500 μL Saline)
Injection Formulation 6: DMSO : PEG300 : castor oil : Saline = 5 : 10 : 20 : 65 (i.e. 50 μL DMSO → 100 μLPEG300 → 200 μL castor oil → 650 μL Saline)
Injection Formulation 7: Ethanol : Cremophor : Saline = 10： 10 : 80 (i.e. 100 μL Ethanol → 100 μL Cremophor → 800 μL Saline)
Injection Formulation 8: Dissolve in Cremophor/Ethanol (50 : 50), then diluted by Saline
Injection Formulation 9: EtOH : Corn oil = 10 : 90 (i.e. 100 μL EtOH → 900 μL Corn oil)
Injection Formulation 10: EtOH : PEG300：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL EtOH → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)

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Oral Formulation 1: Suspend in 0.5% CMC Na (carboxymethylcellulose sodium)
Oral Formulation 2: Suspend in 0.5% Carboxymethyl cellulose
Example: Take the Oral Formulation 1 (Suspend in 0.5% CMC Na) as an example, if 100 mL of 2.5 mg/mL working solution is to be prepared, you can first prepare 0.5% CMC Na solution by measuring 0.5 g CMC Na and dissolve it in 100 mL ddH2O to obtain a clear solution; then add 250 mg of the product to 100 mL 0.5% CMC Na solution, to make the suspension solution (2.5 mg/mL, ready for use in animals).

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Oral Formulation 3: Dissolved in PEG400
Oral Formulation 4: Suspend in 0.2% Carboxymethyl cellulose
Oral Formulation 5: Dissolve in 0.25% Tween 80 and 0.5% Carboxymethyl cellulose
Oral Formulation 6: Mixing with food powders

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Note: Please be aware that the above formulations are for reference only. InvivoChem strongly recommends customers to read literature methods/protocols carefully before determining which formulation you should use for in vivo studies, as different compounds have different solubility properties and have to be formulated differently.

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 (Please use freshly prepared in vivo formulations for optimal results.)