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European Journal of Nuclear Medicine Apr 1994We have evaluated the potential usefulness of indium-111 labelled [DTPA-D-Phe1]RC-160, derived from the octapeptide somatostatin analogue RC-160, as a... (Comparative Study)
Comparative Study
A new radiolabelled somatostatin analogue [111In-DTPA-D-Phe1]RC-160: preparation, biological activity, receptor scintigraphy in rats and comparison with [111In-DTPA-D-Phe1]octreotide.
We have evaluated the potential usefulness of indium-111 labelled [DTPA-D-Phe1]RC-160, derived from the octapeptide somatostatin analogue RC-160, as a radiopharmaceutical for the in vivo detection of somatostatin receptor-positive tumours. For this purpose 111In-and 115In-labelled [DTPA-D-Phe1]RC-160 was tested for its biological activity, and applied for somatostatin receptor scintigraphy in vivo to rats bearing the transplantable rat pancreatic tumour CA20948, which expresses somatostatin receptors. We previously described the development of the 111In-labelled somatostatin analogue [DTPA-D-Phe1]octreotide and its use in the in vivo visualization of somatostatin receptor-positive tumours in rats and in humans. Like [111In-DTPA-D-Phe1]octreotide, [111In-DTPA-D-Phe1]RC-160 showed uptake in and specific binding in vivo to somatostatin receptor-positive organs and tumours, and the tumours were clearly visualized by gamma camera scintigraphy. However, as compared to [111In-DTPA-D-Phe1]octreotide, blood radioactivity (background) was higher, resulting in a lower tumour to blood (background) ratio. Using this animal model we therefore conclude that [111In-DTPA-D-Phe1]RC-160 has no advantage over [111In-DTPA-D-Phe1]octreotide as a radiopharmaceutical in the visualization of somatostatin receptors which bind both analogues. However, recent reports suggest the existence of different somatostatin receptor subtypes on some human cancers, which differentially bind RC-160 and not octreotide. These tumours include cancers of the breast, ovary, exocrine pancreas, prostate and colon. [111In-DTPA-D-Phe1]RC-160 might be of interest for future use in such cancer patients as a radiopharmaceutical for imaging somatostatin receptor-positive tumours, which do not bind octreotide.
Topics: Animals; Indium Radioisotopes; Male; Octreotide; Pancreatic Neoplasms; Pentetic Acid; Radionuclide Imaging; Rats; Rats, Inbred Lew; Receptors, Somatostatin; Somatostatin; Tissue Distribution
PubMed: 7911760
DOI: No ID Found -
Proceedings of the National Academy of... Feb 1987Pancreatic ductal adenocarcinoma was induced in female Syrian golden hamsters by injecting N-nitrosobis(2-oxopropyl)amine (BOP) once a week at a dose of 10 mg per kg of...
Pancreatic ductal adenocarcinoma was induced in female Syrian golden hamsters by injecting N-nitrosobis(2-oxopropyl)amine (BOP) once a week at a dose of 10 mg per kg of body weight for 18 weeks. Hamsters were then treated with somatostatin analog D-Phe-Cys-Tyr-D-Trp-Lys-Val-Cys-Trp-NH2 (RC-160) or with [6-D-tryptophan]luteinizing hormone-releasing hormone [( D-Trp6]LH-RH) delayed delivery systems. Microcapsules of somatostatin analog RC-160, designed to release a dose of 5 micrograms/day, were injected twice a month and microcapsules of [D-Trp6]LH-RH, calculated to liberate 25 micrograms per day, once a month. After 18 weeks of BOP administration, the hamsters were divided into three groups of 10-20 animals each. Group I consisted of untreated controls, group II was injected with RC-160, and group III was injected with [D-Trp6]LH-RH. A striking decrease in tumor weight and volume was obtained in animals treated with [D-Trp6]LH-RH or with the somatostatin analog RC-160. After 45 days of treatment with either analog, the survival rate was significantly higher in groups II and III (70%), as compared with the control group (35%). The studies, done by light microscopy, high-resolution microscopy, and electron microscopy, showed a decrease in the total number of cancer cells and changes in the epithelium, connective tissue, and cellular organelles in groups II and III treated with the hypothalamic analogs as compared to controls. These results in female hamsters with induced ductal pancreatic tumors confirm and extend our findings, obtained in male animals with transplanted tumors, that [D-Trp6]LH-RH and somatostatin analogs inhibit the growth of pancreatic cancers.
Topics: Adenocarcinoma; Animals; Cricetinae; Female; Gonadotropin-Releasing Hormone; Mesocricetus; Microscopy, Electron; Mortality; Nitrosamines; Pancreatic Neoplasms; Somatostatin; Triptorelin Pamoate
PubMed: 2881296
DOI: 10.1073/pnas.84.4.1112 -
British Journal of Pharmacology Jan 2000The therapeutic potential of the somatostatin analogue RC-160 having antiproliferative activity, is limited by its short serum half life. To overcome this limitation,...
The therapeutic potential of the somatostatin analogue RC-160 having antiproliferative activity, is limited by its short serum half life. To overcome this limitation, fatty acids namely butanoic acid and myristic acid were conjugated to the N-terminal residue of RC-160. The lipophilized derivatives of RC-160 were synthesized, purified by reverse phase HPLC and characterized by ES-mass spectroscopy. The antiproliferative activity of lipophilized derivatives of RC-160 on the growth of MIA-PaCa2 (human pancreatic carcinoma), DU145 (human prostate carcinoma), ECV304 (human umbilical chord endothelioma), as well as their antiangiogenic activity was evaluated in vitro. The relative stability of myristoyl-RC-160 towards degradation by proteases and serum was also determined. Myristoyl-RC-160 exhibited significantly higher antiproliferative efficacy than RC-160, on the above cell lines (P<0.01). Receptor binding assays, demonstrated that the affinity of RC-160 towards somatostatin receptors remains unaltered by myristoylation. Unlike RC-160, the myristoylated derivative was found to have significantly greater resistance to protease and serum degradation (P<0.01). Myristoyl-RC-160 exhibited significantly greater antiproliferative activity on ECV304, than RC-160 (P<0.01). Myristoyl RC-160 could also inhibit capillary tube formation more efficiently than RC-160 in a dose dependent manner, suggesting that it possessed enhanced antiangiogenic activity in vitro (P<0.001). Lipophilization of RC-160 with long chain fatty acids like myristic acid endows it with improved antiproliferative and antiangiogenic activity, stability and therapeutic index. British Journal of Pharmacology (2000) 109, 101 - 109
Topics: Angiogenesis Inhibitors; Antineoplastic Agents, Hormonal; Capillary Action; Cell Division; Endopeptidases; Endothelium, Vascular; Fatty Acids; Half-Life; Hormone Antagonists; Humans; Hydrolysis; Receptors, Somatostatin; Somatostatin; Structure-Activity Relationship; Tumor Cells, Cultured
PubMed: 10694208
DOI: 10.1038/sj.bjp.0702990 -
Proceedings of the National Academy of... Mar 1991Pancreatic cancers overexpress tyrosine kinase and luteinizing hormone-releasing hormone (LH-RH) receptor (LH-RHR)-mediated tyrosine phosphatase. LH-RHR is a 60-kDa...
Pancreatic cancers overexpress tyrosine kinase and luteinizing hormone-releasing hormone (LH-RH) receptor (LH-RHR)-mediated tyrosine phosphatase. LH-RHR is a 60-kDa protein. One of the substrates of epidermal growth factor (EGF)-stimulated tyrosine kinase activity and LH-RH- and somatostatin-stimulated tyrosine phosphatase activity is also a 60-kDa protein. This suggests the possibility that LH-RHR regulation by tyrosine phosphatase and tyrosine kinase is mediated by (de)phosphorylation of existing LH-RHR. To test this hypothesis, membranes of MIA PaCa-2 cells, a human dedifferentiated pancreatic cancer cell line, were incubated without hormone (control) or with 0.1 microM EGF or somatostatin analogue RC-160 for 1 hr at 4 degrees C to phosphorylate the 60-kDa protein. Competition binding experiments with I125-labeled [D-Trp6]LH-RH by displacement with a nonradioactive ligand showed that the LH-RH binding in 69% of the points was increased by EGF and 85% was decreased by RC-160 compared with controls (n = 61; both significant, P less than 0.001). The specific binding was altered, increasing 50-150% after preincubation with EGF and decreasing 60-70% after RC-160. No change was seen in the binding affinity constant after pretreatment with EGF or RC-160. This shows that phosphorylation regulates binding of LH-RH and may explain the up-regulation by EGF and down-regulation by RC-160 and by LH-RH of the LH-RH response.
Topics: Cell Line; Gonadotropin-Releasing Hormone; Humans; Kinetics; Pancreatic Neoplasms; Phosphorylation; Protein-Tyrosine Kinases; Receptors, LHRH; Somatostatin; Triptorelin Pamoate
PubMed: 1672452
DOI: 10.1073/pnas.88.6.2244 -
Proceedings of the National Academy of... Feb 1988Membrane receptors for luteinizing hormone-releasing hormone (LH-RH), somatostatin, and prolactin (PRL) were investigated in the Dunning R-3327H rat prostate...
Receptors for prolactin, somatostatin, and luteinizing hormone-releasing hormone in experimental prostate cancer after treatment with analogs of luteinizing hormone-releasing hormone and somatostatin.
Membrane receptors for luteinizing hormone-releasing hormone (LH-RH), somatostatin, and prolactin (PRL) were investigated in the Dunning R-3327H rat prostate adenocarcinoma specimens after in vivo treatment with microcapsules of the agonist [D-Trp6]LH-RH and the somatostatin analog RC-160. The LH-RH receptors showed a low-binding affinity (Kd = 54 nM) and high capacity (Bmax = 12.0 pmol/mg). Treatment with the [D-Trp6]LH-RH decreased the binding affinity (Kd = 0.52 microM). Specific somatostatin receptors, with Kd = 1.3 nM and Bmax = 543 fmol/mg, were also found. Treatment with [D-Trp6]LH-RH lowered Bmax to 44 fmol/mg, and administration of RC-160 reduced Kd to 30 nM. After the combined treatment with the two analogs, Kd and Bmax were decreased. Specific PRL receptors (Kd = 0.72 nM; Bmax = 161 fmol/mg) were also detected. Treatment with either analog reduced Bmax by 50%, but a much greater reduction of PRL binding capacity was revealed after in vitro dissociation of the bound endogenous PRL by MgCl2. The dramatic fall in the total number of PRL receptors after combination treatment with both analogs could be partially responsible for the decrease in the weight and volume of prostate tumors. The findings support the concept that analogs of LH-RH and somatostatin can inhibit tumors directly through their own respective receptors. One of several mechanisms of the antineoplastic activity of these analogs could be the elimination of tumor growth-promoting effect of PRL by the reduction of the total number of PRL receptors.
Topics: Adenocarcinoma; Animals; Antineoplastic Agents; Drug Synergism; Gonadotropin-Releasing Hormone; Male; Prostatic Neoplasms; Rats; Receptors, LHRH; Receptors, Neurotransmitter; Receptors, Prolactin; Receptors, Somatostatin; Somatostatin; Triptorelin Pamoate
PubMed: 2893378
DOI: 10.1073/pnas.85.3.890 -
Proceedings of the National Academy of... Oct 1987The combination of a long-acting delivery system for the agonist [D-Trp6]luteinizing hormone-releasing hormone ([D-Trp6]LH-RH) with modern somatostatin analogs was...
The combination of a long-acting delivery system for the agonist [D-Trp6]luteinizing hormone-releasing hormone ([D-Trp6]LH-RH) with modern somatostatin analogs was studied in the Dunning R-3327H rat prostate cancer model. Microcapsules of [D-Trp6]LH-RH releasing 25 micrograms/day were injected once a month. In the first experiment the adjunct was the somatostatin analog D-Phe-Cys-Tyr-D-Trp-Lys-Val-Cys-Thr-NH2 (RC-121), administered at a dose of 2.5 micrograms twice a day, and the therapy was continued for 70 days. Tumor volume was significantly decreased by [D-Trp6]LH-RH microcapsules or RC-121 given alone. The combination of microcapsules and analog RC-121 caused a greater inhibition of tumor growth than the single agents. Similar effects were seen when the percent increase in the tumor volume was examined. The inhibition of tumor growth caused by the [D-Trp6]LH-RH microcapsules was greater than that caused by RC-121. The combination of the two agents was again the most effective, resulting in the smallest increase in tumor volume. Tumor weights were much lower in the groups treated with microcapsules or RC-121 alone than in controls. The lowest tumor weights were obtained in the group that received the combination of [D-Trp6]LH-RH microcapsules and RC-121. Similar results were obtained in the second experiment, in which the animals were treated for a period of 83 days with microcapsules containing the somatostatin analog D-Phe-Cys-Tyr-D-Trp-Lys-Val-Cys-Trp-NH2 (RC-160) that released 5 micrograms/day and were injected twice a month alone or in combination with microcapsules of [D-Trp6]LH-RH. Microcapsules of analog RC-160 given alone significantly decreased tumor growth as measured by the final tumor volume, the percentage change from the initial tumor volume, and the reduction in tumor weight. The inhibition of tumor growth induced by [D-Trp6]LH-RH microcapsules was greater than that caused by RC-160. The most striking decrease in tumor weight and volume was obtained in animals treated with microcapsules of [D-Trp6]LH-RH combined with the delayed delivery system for RC-160. The overall response to the combination therapy could reflect the inhibition by somatostatin analogs of the proliferation of prostate cancer cells through a decrease in growth hormone and prolactin release and interference with endogenous growth factors, in addition to the main effect, which is the suppression by [D-Trp6]LH-RH of the growth of androgen-dependent tumor cells. Our results indicate that somatostatin analogs enhance the inhibitory effects of [D-Trp6]LH-RH on the growth of prostate tumors. The administration of somatostatin analogs in combination with microcapsules of [D-Trp6]LH-RH might improve clinical response in patients with advanced prostate carcinoma.
Topics: Adenocarcinoma; Animals; Antineoplastic Agents; Capsules; Drug Compounding; Drug Synergism; Gonadotropin-Releasing Hormone; Male; Octreotide; Organ Size; Prostate; Prostatic Neoplasms; Rats; Somatostatin; Triptorelin Pamoate
PubMed: 2890164
DOI: 10.1073/pnas.84.20.7275 -
Proceedings of the National Academy of... Aug 1988The development of a long-acting delivery system for D-Phe-Cys-Tyr-D-Trp-Lys-Val-Cys-Trp-NH2 (RC-160), an octapeptide analog of somatostatin, required the establishment...
The development of a long-acting delivery system for D-Phe-Cys-Tyr-D-Trp-Lys-Val-Cys-Trp-NH2 (RC-160), an octapeptide analog of somatostatin, required the establishment of a method for determining the concentration of this analog in serum during treatment. A sensitive and specific radioimmunoassay (RIA) for RC-160 was developed and used for following the rate of liberation of this peptide from microcapsules of poly(DL-lactide-coglycolide). Antibodies were generated in a rabbit against RC-160 conjugated to bovine serum albumin with glutaraldehyde. At an antiserum dilution of 1:100,000, the antibodies bound approximately 25% of added radiolabeled RC-160. Somatostatin octapeptide analogs that had a disulfide bridge showed crossreactivity with the antiserum, but analogs without the disulfide bridge and other peptides tested did not crossreact. The minimum detectable dose of RC-160 was 10 pg. Intra- and interassay coefficients of variation ranged from 9.1% to 12.8% and from 14% to 30%, respectively. The RIA was suitable for direct determination of RC-160 in serum. Eleven prototype batches of microcapsules were tested in rats, and the rate of release of the analog from the microcapsules was followed. An improved batch of microcapsules made from RC-160 pamoate maintained high serum levels of RC-160 for more than 30 days after intramuscular injection. The RIA should be of value for monitoring levels of this analog in serum during long-term therapy.
Topics: Animals; Antineoplastic Agents; Capsules; Cross Reactions; Delayed-Action Preparations; Injections, Intramuscular; Male; Predictive Value of Tests; Radioimmunoassay; Rats; Rats, Inbred Strains; Somatostatin
PubMed: 2899894
DOI: 10.1073/pnas.85.15.5688 -
Proceedings of the National Academy of... Mar 1989Female Syrian golden hamsters with N-nitrosobis(2-oxopropyl)amine (BOP)-induced ductal pancreatic cancers were treated with long-acting microcapsular preparations of the...
Female Syrian golden hamsters with N-nitrosobis(2-oxopropyl)amine (BOP)-induced ductal pancreatic cancers were treated with long-acting microcapsular preparations of the 6-D-tryptophan analog of luteinizing hormone-releasing hormone [( D-Trp6]LH-RH), releasing 25 micrograms/day; the somatostatin analog D-Phe-Cys-Tyr-D-Trp-Lys-Val-Cys-Trp-NH2 (RC-160), liberating 15 micrograms/day; and the combination of these two peptides. Therapy with analogs was initiated 24 weeks after initial administration of BOP. These treatments resulted in significantly better survival of all animals as compared to BOP controls; body weights of surviving peptide-treated animals were significantly higher than those of the BOP controls. All 15 BOP-control animals had pancreatic cancers. In the group treated with RC-160 four hamsters were free of tumors, whereas therapy with [D-Trp6]LH-RH resulted in seven tumor-free animals, and combination of RC-160 and [D-Trp6]LH-RH resulted in eight tumor-free animals from groups of 15. Only preblastomatous lesions were found in these animals. Average tumor weight of animals in all peptide-treated groups, sacrificed 60 days after beginning the peptide treatment, was significantly lower than that of BOP controls. No significant differences were seen between the various peptide-treated groups. Histologically, analog-treated tumors of hamsters showed striking regressive changes characteristic of programmed cell death (apoptosis). This apoptosis presumably resulted from hormonal effects on tumor cells from prolonged treatment with these analogs of hypothalamic hormones. Our present data confirm the beneficial effect of long-acting microcapsules of [D-Trp6]LH-RH and RC-160 on pancreatic carcinoma and suggest a mode of action for these peptides. The feasibility of applying this treatment with analogs of hypothalamic hormones to human pancreatic carcinoma can be envisioned from these studies.
Topics: Animals; Antineoplastic Agents; Antineoplastic Combined Chemotherapy Protocols; Cell Survival; Cricetinae; Female; Gonadotropin-Releasing Hormone; Mesocricetus; Pancreatic Neoplasms; Somatostatin; Triptorelin Pamoate
PubMed: 2564204
DOI: 10.1073/pnas.86.5.1643 -
The Journal of Biological Chemistry Apr 1994The solution conformations of RC-160, cyclic D-Phe1-Cys2-Tyr3-D-Trp4-Lys5-Val6-Cys7+ ++-Trp8-NH2, an analog of the tumor antiproliferatory neuropeptide somatostatin, and...
The solution conformations of RC-160, cyclic D-Phe1-Cys2-Tyr3-D-Trp4-Lys5-Val6-Cys7+ ++-Trp8-NH2, an analog of the tumor antiproliferatory neuropeptide somatostatin, and RC-160 labeled with rhenium (Re-RC-160), have been determined by using two-dimensional 1H NMR spectroscopy (600 MHz) and restrained molecular dynamics simulations. Re-RC-160 yields the same average solution conformation as does the apo form with an antiparallel beta-sheet fold and a type II' beta-turn centered at D-Trp4-Lys5. These results indicate that the spatial topography of the side chains essential for somatostatin receptor binding is maintained in Re-RC-160.
Topics: Amino Acid Sequence; Antineoplastic Agents; Computer Simulation; Magnetic Resonance Spectroscopy; Models, Molecular; Molecular Sequence Data; Rhenium; Somatostatin
PubMed: 7909804
DOI: No ID Found -
British Journal of Cancer Sep 1992The in vivo administration of somatostatin (SS) or its analogues is capable of suppressing the growth of pancreatic cancer in experimental animals. We examined the...
The in vivo administration of somatostatin (SS) or its analogues is capable of suppressing the growth of pancreatic cancer in experimental animals. We examined the effects of SS-14 and its analogue RC-160 on the in vitro growth of two human pancreatic cancer cell lines MiaPaCa-2 and Panc-1 stimulated with epidermal growth factor (EGF) or insulin-like growth factor 1 (IGF-1). Neither SS-14 nor RC-160 inhibited the growth of either cell line. In contrast RC-160 did inhibit the EGF-stimulated growth of a rat pancreatic cancer cell line AR42J. Binding studies with 125I-Tyr11 somatostatin revealed the presence of a single class of high affinity binding sites with a Kd of 0.20 +/- 0.05 nM and a Bmax of 2.1 +/- 0.26 pmoles mg-1 protein on AR42J but not displaceable binding was observed on MiaPaCa-2 or Panc-1. We conclude that lack of receptors accounts for the failure of SS-14 and RC-160 to influence the growth of human pancreatic cancer in vitro. These results, taken together with other findings, lead us to question the therapeutic efficacy of somatostatin and its analogues as mono-therapy in the treatment of human pancreatic cancer.
Topics: Animals; Carcinoma, Intraductal, Noninfiltrating; Epidermal Growth Factor; Humans; Insulin-Like Growth Factor I; Pancreatic Neoplasms; Rats; Receptors, Neurotransmitter; Receptors, Somatostatin; Somatostatin; Tumor Cells, Cultured
PubMed: 1355659
DOI: 10.1038/bjc.1992.300