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ABSTRACT: The involvement of IGF-I in mammary carcinogenesis is well established, but the role of GH, as an autocrine growth factor for breast cancers is poorly understood. The goal of our study was to investigate whether antagonists of GHRH can interfere with the effects of GH and IGF-I in MXT mouse mammary cancers. GHRH antagonists JV-1-36 and JV-1-38 inhibited growth of estrogen-independent MXT mouse mammary cancers in vivo, producing about 50% reduction in tumor volume (P < 0.05). This growth inhibition was associated with a decrease in cell proliferation and an increase in apoptosis in MXT cancers. RIA and RT- PCR analyses showed that the concentrations of GH and IGF-I and the levels of mRNA for GH and IGF-I in MXT tumors were reduced by the therapy with GHRH antagonists. Messenger RNA for GH receptors was also decreased. In vitro, the proliferation of MXT cancer cells was strongly stimulated by GH and less effectively by IGF-I, indicating that both GH and IGF-I may act as growth factors for this mammary carcinoma. GHRH antagonist JV-1-38 inhibited the autonomous growth of MXT cells and the proliferation induced by IGF-I or GH and diminished (3)H-thymidine-incorporation stimulated by IGF-I and GH. These findings and a sustained increase in cyclin B2 concentrations in the cells shown by immunoblotting indicate that JV-1-38 causes a block at the end of the G(2) phase of cell cycle. Our results demonstrate that GHRH antagonists decrease the local production of both GH and IGF-I in MXT mouse mammary cancers, the resulting growth inhibition being the consequence of reduced cell proliferation and increased apoptosis.
Endocrinology 10/2001; 142(10):4371-8. · 4.46 Impact Factor
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ABSTRACT: We evaluated the effects of the bombesin/gastrin-releasing peptide (GRP) antagonist RC-3095, and the luteinizing hormone-releasing hormone (LH-RH) antagonist Cetrorelix, administered singly or in combination, on the growth of human ovarian carcinoma cell line ES-2, xenografted into nude mice. RC-3095 at a dose of 20 microg/day and Cetrorelix (100 microg/day), significantly reduced the volume of ES-2 tumors by 63.0% (P<0.01) and 38.0% (P<0.05) respectively, after 44 days of treatment, as compared with controls. The combination of RC-3095 with Cetrorelix inhibited the growth of ES-2 tumors by 66.2% (P<0.01). Serum levels of LH were significantly decreased in the groups treated with Cetrorelix alone and/or in combination with RC-3095. RT-PCR analyses revealed that the expression of mRNA for receptors of GRP (GRPR/BRS-1) and Neuromedin B (NMBR/BRS-2) on tumors was significantly decreased in all the treated groups. The expression of mRNA for epidermal growth factor receptors (EGFR) on tumors was reduced by 36.5 % (P<0.05) in the animals treated with Cetrorelix and by 72.5% (P<0.05) in the group that received the combination of RC-3095 with Cetrorelix. Our results indicate that the bombesin antagonist RC-3095 and the LH-RH antagonist Cetrorelix inhibit effectively the growth of ES-2 ovarian cancers in nude mice. These antagonists and their combination could be considered for the therapy of patients with ovarian cancer.
Cancer Letters 10/2001; 171(1):37-45. · 4.24 Impact Factor
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ABSTRACT: The expression of somatostatin receptors (SSTRs) allows the localization and treatment of some tumors with radiolabeled SST analogues. We investigated whether SSTRs on human pancreatic cancer lines xenografted into nude mice can be used for targeting of cytotoxic somatostatin analogue AN-238, consisting of 2-pyrrolinodoxorubicin (AN-201) linked to octapeptide carrier RC-121.
AN-238 and AN-201 were administered i.v. to nude mice bearing SW-1990 pancreatic cancers. Tumor growth reduction and survival were analyzed, and cell proliferation and apoptosis were determined with histological methods. The effects of repeated administration of AN-238 and AN-201 were also evaluated on xenografted Panc-1, MiaPaCa-2, CFPAC-1, Capan-1, and Capan-2 pancreatic cancers. The expression of mRNA for SSTR subtypes 2A, 3, and 5 in tumors was analyzed by reverse transcription-PCR, and binding assays were performed.
All of the cancer models except MiaPaCa-2 displayed functional receptors for SST. SW-1990 expressed mRNA for SSTR subtypes 3 and 5, whereas various patterns of subtypes 2A, 3, and 5 were found in other pancreatic cancers. Repeated administration of AN-238 at 150 nmol/kg significantly inhibited growth of SW-1990 cancers (93% after 45 days; P = 0.016) and other tumors but not MiaPaCa-2. AN-201 was toxic and less effective. The efficacy of AN-238 was consistent with SSTR expression.
Growth of experimental human pancreatic cancers that express SSTRs can be inhibited by cytotoxic somatostatin analogue AN-238.
Clinical Cancer Research 10/2001; 7(9):2854-61. · 7.74 Impact Factor
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ABSTRACT: Recently, we developed a cytotoxic analogue of somatostatin (SST), AN-238, in which the SST carrier peptide RC-121 was linked to 2-pyrrolinodoxorubicin (2-pyrrolino-DOX) (AN-201), a potent derivative of doxorubicin. AN-238 can be targeted to SST receptors (SSTRs) on tumours. In the present study, we evaluated the effects of AN-238 on the growth of H-69 small-cell lung carcinoma (SCLC) and H-157 non-SCLC xenografted into nude mice. High affinity binding sites for SST are present in H-69 SCLC and were now detected in H-157 non-SCLC xenografts, but not in H-157 cells. A strong expression of the human SSTR subtype 2 (hSSTR-2) and a weaker expression of subtype 5 (hSSTR-5) was found in H-69 SCLC cells, but not in H-157 non-SCLC cells. However, a strong expression of mRNA for mouse (m)SSTR-2 could be detected in H-157 xenografts. AN-238 effectively inhibited the growth of H-69 SCLC tumours in nude mice. Twenty-six days after a single injection of AN-238 at 200 nmol/kg, the volume of H-69 tumours was decreased by approximately 55% (P<0.05) compared with the controls, while AN-201 at the same dose was highly toxic and produced only a minor tumour inhibition. To evaluate the potency of multiple doses of AN-238, nude mice bearing H-69 SCLC received three injections of AN-238 at 150 nmol/kg on days 1, 12 and 28. In the period of 42 days after the first injection, the growth rate of H-69 tumours was approximately 50% lower than that of controls. In nude mice bearing H-157 non-SCLC tumours, a single i.v. administration of AN-238 at 200 nmol/kg inhibited tumour volume by 91% after 28 days (P<0.01 compared with controls). AN-201 was toxic and ineffective at the same dose. Two injections of AN-238 at 150 nmol/kg given on days 1 and 18 produced 83% inhibition of H-157 tumour growth (P<0.01 versus controls). AN-238 given as a single dose of 200 nmol/kg induced necrosis, while two injections of 150 nmol/kg induced apoptosis in the tumour tissue. Our results indicate that targeted cytotoxic SST analogue AN-238 could be considered for therapy of both SCLC and non-SCLC.
European Journal of Cancer 03/2001; 37(5):620-8. · 5.54 Impact Factor
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ABSTRACT: Characteristics of receptors for somatostatin (SST) analog RC-160 on 17 surgical specimens of human epithelial ovarian cancer and two human ovarian cancer lines were determined by ligand competition assays. The expression of mRNA for four SST receptor subtypes (sst1, sst2A, sst3 and sst5) was investigated by RT-PCR. Thirteen of 17 specimens (76%) exhibited high affinity binding sites for RC-160 with Kd = 6.55 nmol/L and a Bmax = 575.4 fmol/mg membrane protein. Specific receptors for RC-160 were also found in xenografts of OV-1063 and UCI-107 human ovarian cancer lines. The mRNA for sst1 was detected in 65% of the ovarian cancer specimens, while the incidence of sst2A, sst3 and sst5 was 65%, 41% and 24%, respectively. Both ovarian cancer cell lines also expressed mRNA for these four subtypes. The presence of these SST receptor subtypes in human ovarian cancers allows the use of SST analogs and their radionuclide and cytotoxic derivatives for the diagnosis and treatment of this malignancy.
Journal of Clinical Endocrinology & Metabolism 11/2000; 85(10):3509-12. · 6.50 Impact Factor
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ABSTRACT: In view of the involvement of various neuropeptides and growth factors in the progression of androgen-independent prostate cancer, we investigated the effects of antagonists of growth hormone-releasing hormone (GHRH) alone or in combination with an antagonist of bombesin/gastrin-releasing peptide (BN/GRP) on PC-3 human prostate cancers.
Nude mice implanted with PC-3 tumors received GHRH antagonists MZ-5-156 or JV-1-38, each at 20 microgram/day s.c. In experiment 2, treatment consisted of daily injections of JV-1-38 (20 microgram), BN/GRP antagonist RC-3940-II (10 microgram), or a combination of JV-1-38 and RC-3940-II. Serum IGF-I levels, expression of mRNA for IGF-II, and characteristics of BN/GRP and EGF receptors in tumor tissue were investigated.
JV-1-38 induced a greater inhibition of tumor growth and suppression of IGF-II mRNA than MZ-5-156, both compounds causing a similar decrease in serum IGF-I. In experiment 2, JV-1-38 and RC-3940-II produced a comparable reduction in tumor volume (65% and 61%, respectively), but a combination of both antagonists augmented tumor inhibition to 75%. Combined treatment with JV-1-38 and RC-3940-II also led to a greater suppression of IGF-II mRNA (92%), as compared with JV-1-38 (72%) or RC-3940-II (77%). Serum IGF-I concentration was lowered only in mice treated with JV-1-38, while the downregulation of BN/GRP and EGF receptors was specific for groups receiving RC-3940-II.
The inhibitory effects of GHRH antagonists on PC-3 human androgen-independent prostate cancer can be potentiated by concomitant use of BN/GRP antagonists. The combination of both types of analogs apparently interferes with both IGF and bombesin/EGF pathways, and might be clinically useful for the management of androgen-independent prostate cancer.
The Prostate 08/2000; 44(2):172-80. · 3.48 Impact Factor
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ABSTRACT: The effectiveness of chemotherapy targeted to somatostatin (SST) receptors based on cytotoxic SST analogue AN-238, consisting of 2-pyrrolinodoxorubicin (AN-201) linked to SST carrier octapeptide, was investigated in human renal cell carcinomas (RCCs). SST receptors, which showed high-affinity binding for AN-238, were found in the SW-839 RCC line with sst2A subtype and in the 786-0 RCC line, which expressed the sst5 subtype. CAKI-1 RCC, which does not express sst2A or sst5, was used as a negative control for testing the specificity of SST receptor targeting. Using microsatellite analysis, AN-238 was shown to selectively inhibit the proliferation of 786-0 line, but not the CAKI-1 RCC line in vitro. The effects of three i.v. injections of 150 nmol/kg of AN-238 or AN-201, given on days 1, 8, and 21, were evaluated in groups of nude mice bearing s.c. xenografts of SW-839 and 786-0 RCC. After 5 weeks, the volumes of SW-839 and 786-0 RCC tumors were decreased by 67.2 (P < 0.05) and 78.3% (P < 0.01), respectively, whereas AN-201 had no significant effect on tumor growth. The inhibition of SST receptor-negative CAKI-1 tumors by AN-238 was only marginal. To investigate the efficacy of SST receptor-targeted chemotherapy in metastatic RCC, three i.v. injections of AN-238 or AN-201 at 150 nmol/kg were given at biweekly intervals to nude mice implanted with 786-0 tumors under the renal capsule. After 6 weeks, the weight of orthotopic tumors treated with AN-238 (55.3 +/- 44.3 mg) was significantly lower (87% reduction; P < 0.001) than that in the control group (414.2 +/- 41.0 mg) or in animals given AN-201 (270.2 +/- 603 mg; P < 0.05). Five of six animals (83%), both in the control and the AN-201 group, developed metastases to lymph nodes, but only one of seven mice (14%) given AN-238 showed lymphatic spread. Lung metastases were found in 83% of controls and 50% of AN-201 treated animals, but none occurred in mice treated with AN-238. This study demonstrates that targeted cytotoxic SST analogue AN-238 provides an effective therapy for chemoresistant neoplasms such as RCC. Because most clinical RCCs express SST receptors, this treatment modality might be beneficial to patients with metastatic disease.
Cancer Research 06/2000; 60(11):2996-3001. · 7.86 Impact Factor
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ABSTRACT: Insulin-like growth factors (IGF-I and IGF-II) are implicated in the pathogenesis of pancreatic carcinoma. Antagonists of growth hormone-releasing hormone (GH-RH) suppress the GH-RH-GH-IGF-I axis and also act directly on tumours to reduce production of IGF-I or II. The aim of this study was to investigate the effects of two potent GH-RH antagonists in two experimental models of pancreatic cancer. Syrian golden hamsters with nitrosamine-induced pancreatic tumours were treated with 10 micrograms/day of GH-RH antagonist MZ-4-71 for 60 days. The therapy reduced the number of tumorous animals, decreased the weight of tumorous pancreata by 55%, and lowered AgNOR numbers in tumour cells. In two other experiments, GH-RH antagonists MZ-4-71 and MZ-5-156 significantly inhibited growth of SW-1990 human pancreatic cancers xenografted into nude mice, as shown by a reduction in tumour volume and tumour weights, and a decrease in AgNORs in cancer cells. IGF-I levels in serum and in pancreatic cancer tissue remained unchanged after therapy, suggesting that an effect on IGF-I is not involved in tumour inhibition. In contrast, IGF-II concentrations in tumours were significantly reduced by 50-60% after treatment with the GH-RH antagonists as compared with controls. In vitro studies showed that the concentration of IGF-II in the culture medium was increased after seeding of SW-1990 cells, indicating that this pancreatic cancer cell line produced and released IGF-II. This finding was also supported by the expression of IGF-II mRNA in the SW-1990 cells. Addition of 3 x 10(-6) M of GH-RH antagonist MZ-5-156 to the reduced-serum medium decreased cell proliferation, IGF-II mRNA expression in the cells and IGF-II concentration in the medium. Our findings indicate that inhibitory effects of GH-RH antagonists on the growth of experimental pancreatic cancers, may result from a decrease in the production and concentration of IGF-II in the tumours.
European Journal of Cancer 02/2000; 36(1):128-36. · 5.54 Impact Factor
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ABSTRACT: Since somatostatin (sst) receptors are expressed in a high percentage of human breast cancers, we studied the effects of a targeted cytotoxic somatostatin analog (AN-238) formed by linking the highly active doxorubicin (DOX) derivative 2-pyrrolino-DOX (AN-201) to octapeptide RC-121 (D-Phe-Cys-Tyr-D-Trp-Lys-Val-Cys-Thr-NH(2)) in 3 human breast cancer models. The models included estrogen-independent MDA-MB-231 and MX-1 and estrogen-sensitive MCF-7-MIII tumors. Nude mice bearing xenografts of these cancers were injected i.v. with 250 nmol/kg doses of cytotoxic radical AN-201, cytotoxic analog AN-238 or the unconjugated mixture of AN-201 and sst analog RC-121. Significant inhibition of growth of MDA-MB-231, MX-1 and MCF-7-MIII tumors was observed 1 week after injection of a single dose of cytotoxic analog AN-238. The volume of MDA-MB-231 tumors remained significantly decreased 3 weeks after treatment. The volumes and weights of MCF-7-MIII tumors continued to be significantly reduced 60 days after therapy with AN-238. AN-238 also caused complete regression of MX-1 tumors in 5 of 10 animals, which remained tumor-free 60 days after treatment. In contrast, after treatment with cytotoxic radical AN-201, MDA-MB-231 and MCF-7-MIII tumors grew steadily and the regression of MX-1 tumors was only transitory in most animals. Toxicity of AN-201 was much greater than that of AN-238, as measured by animal deaths, loss of body weight and leukopenia. High-affinity sst receptors and mRNA for both sst(2) and sst(5) subtypes were found in all 3 tumor lines. Expression of sst receptors was not significantly affected by treatment with AN-238. Our results indicate that the cytotoxic somatostatin analog AN-238 efficaciously inhibits growth of human breast cancers expressing sst receptor subtypes 2 and 5.
International Journal of Cancer 09/1999; 82(4):592-8. · 5.44 Impact Factor
