Biomedical subjects

J Viallet

Publications and source records attributed to J Viallet.

At least 19 recordsLinked to original sources

PubMed2000

Tirapazamine plus cisplatin versus cisplatin in advanced non-small-cell lung cancer: A report of the international CATAPULT I study group. Cisplatin and Tirapazamine in Subjects with Advanced Previously Untreated Non-Small-Cell Lung Tumors.

PURPOSE: A phase III trial, Cisplatin and Tirapazamine in Subjects with Advanced Previously Untreated Non-Small-Cell Lung Tumors (CATAPULT I), was designed to determine the efficacy and safety of tirapazamine plus cisplatin for the treatment of non-small-cell lung cancer (NSCLC). PATIENTS AND METHODS: Patients with previously untreated NSCLC were randomized to receive either tirapazamine (390 mg/m(2) infused over 2 hours) followed 1 hour later by cisplatin (75 mg/m(2) over 1 hour) or 75 mg/m(2) of cisplatin alone, every 3 weeks for a maximum of eight cycles. RESULTS: A total of 446 patients with NSCLC (17% with stage IIIB disease and pleural effusions; 83% with stage IV disease) were entered onto the study. Karnofsky performance status (KPS) was >/= 60 for all patients (for 10%, KPS = 60; for 90%, KPS = 70 to 100). Sixty patients (14%) had clinically stable brain metastases. The median survival was significantly longer (34.6 v 27. 7 weeks; P =.0078) and the response rate was significantly greater (27.5% v 13.7%; P <.001) for patients who received tirapazamine plus cisplatin (n = 218) than for those who received cisplatin alone (n = 219). The tirapazamine-plus-cisplatin regimen was associated with mild to moderate adverse events, including acute, reversible hearing loss, reversible, intermittent muscle cramping, diarrhea, skin rash, nausea, and vomiting. There were no incremental increases in myelosuppression, peripheral neuropathy, or renal, hepatic, or cardiac toxicity and no deaths related to tirapazamine. CONCLUSION: The CATAPULT I study shows that tirapazamine enhances the activity of cisplatin in patients with advanced NSCLC and confirms that hypoxia is an exploitable therapeutic target in human malignancies.

Adult↗

PubMed2000

[Pituitary gland MRI and Cushing disease: report of 14 operated patients].

PURPOSE: Evaluate the MR sensibility for detection and localisation of ACTH-secreting microadenomas of the pituitary gland. PATIENTS: and method. The MRI studies of the pituitary gland, performed before transsphenoidal surgical exploration, about 14 patients who present clinical and biological signs of Cushing disease, were reviewed retrospectively. We have always used unenhanced sagittal and coronal spin-echo T1 sequences, and coronal T1 after injection of gadolinium (1 Tesla). RESULTS: The global sensibility for detection of an adenoma was 100% (84 to 92% when the lesional localisation was considered). The injection of gadolinium increased the sensibility of 38 to 42% according the readers. 7 to 14% of the lesions were isointense after injection. The estimation of lesional size after injection was the nearer to the surgical results. The indirect sign most frequently seen (35.7 to 64.3%) was focal bulging of the sellar diaphragm. The only differences between the different radiologists, statistically significant, concerned the lesional size before injection and location of the lesion in the sagittal plane. CONCLUSION: This study confirmed the good sensibility of contrast-enhanced MRI in detection of ACTH-secreting microadenomas. The anatomo-radiological correlations are nevertheless incomplete.

Adult↗

PubMed1999

A phase I/II trial of neoadjuvant chemotherapy with cisplatin and vinorelbine followed by accelerated irradiation for patients with inoperable nonsmall cell lung carcinoma.

BACKGROUND: Both locoregional and distant disease control remains poor in the treatment of Stage III nonsmall cell lung carcinoma (NSCLC). This trial was conducted to evaluate the tolerance and responses of patients with NSCLC given a neoadjuvant regimen of cisplatin and vinorelbine chemotherapy followed by accelerated thoracic radiotherapy. METHODS: Forty-two patients with Stage IIIA and IIIB NSCLC were entered into the study. Treatment consisted of cisplatin 100 mg/m2 given on Days 1 and 29 and vinorelbine 30 mg/m2 given weekly for 5 weeks, with a planned 50% dose reduction to 15 mg/m2 planned for Week 2. This was followed by thoracic irradiation of 60 gray (Gy) in 30 fractions of 2 Gy over 4 weeks (once daily during Weeks 1 and 2 and twice daily during Weeks 3 and 4). RESULTS: With a median follow-up time of 12.2 months (27-65 months for survivors), the median survival was 12.2 months (16.6 months for patients with no prior weight loss and 7.8 months for those with prior weight loss). The response rate after induction chemotherapy was 46.1%, increasing to 74.4% after radiation therapy (8 complete responses and 21 partial responses). The rate of progression was 13 of 18 (72%) for those who responded to chemotherapy (4 distant, 9 local) and 18 of 21 (86%) for those who did not respond to chemotherapy (14 distant, 7 local). The most frequent acute Grade 3 toxicity was nausea (21.4%). CONCLUSIONS: Accelerated thoracic irradiation after induction chemotherapy is well tolerated and yields therapeutic results that compare favorably with those reported for other regimens of chemotherapy and standard fractionated radiotherapy. The data from this study suggest that the responses of patients with clinically apparent disease to induction chemotherapy might indicate a likelihood of controlling microscopic distant metastases.

Adult↗

PubMed1999

Phase II trial of escalated dose of tirapazamine combined with cisplatin in advanced malignant melanoma.

A phase II study was undertaken to determine the efficacy of tirapazamine combined with cisplatin in patients with metastatic melanoma between April 1996 and April 1997. Tirapazamine 390 mg/m2, administered i.v. over 2 h, followed in 1 h by cisplatin 75 mg/m2 over 1 h, were used every 21 days to treat chemotherapy-naive patients with metastatic melanoma. Objective tumor measurements were used to assess efficacy of the regimen. NCI common toxicity criteria were used to grade toxicities. Forty-eight patients with metastatic melanoma of cutaneous or mucosal origin, none with symptomatic brain metastasis, were treated. Nine patients had a partial response, with an overall response rate of 20% (95% confidence interval: 9-33%). The median duration of response was 6 months. Grade 3 nausea, vomiting, anorexia, muscle cramps and fatigue occurred in fewer than 10% of patients. Neutropenia and thrombocytopenia were rare. This outpatient single-day administered tirapazamine-cisplatin regimen has definite activity in chemotherapy-naive patients with metastatic melanoma. Further studies in combination with other agents active against this disease are warranted.

Adult↗

PubMed1998

Differential expression of Met/hepatocyte growth factor receptor in subtypes of non-small cell lung cancers.

Hepatocyte growth factor (HGF)/scatter factor (SF) is a multifunctional factor that stimulates epithelial cell motility, invasion and morphogenesis. Its receptor is a transmembrane tyrosine kinase encoded by the Met proto-oncogene. Several studies have suggested a possible role for HGF/Met in tumor development and progression. To investigate the potential roles of Met in human lung cancer biology, we have studied the mRNA and protein expression of Met in normal lung tissue, primary non-small cell lung carcinoma (NSCLC), and NSCLC cell lines. The results indicated a differential pattern of Met expression among various subtypes of NSCLC. The majority of squamous cell carcinoma (SQCC), either in vivo or in vitro, expressed Met mRNA and its protein product at levels much lower than or similar to normal lung tissue or bronchial epithelium. Moreover, SQCC characteristically over-expressed a variant Met mRNA which corresponds to a 5' partially deleted transcript produced by alternative splicing. In contrast, the expression of Met mRNA and its protein product in adenocarcinoma (ADC) and large cell undifferentiated carcinoma were more heterogeneous. Overexpression was demonstrated in approximately 35% and 20% of these subtypes of NSCLC, respectively. Among ADC, intermediate to high levels of Met immunoreactivity correlated with greater degree of tumor differentiation. Furthermore, an accentuation of Met immunoreactivity was often noted in cancer cells at the advancing edge of tumors. These findings support a role for Met in lung cancer cell invasion and differentiation in vivo, but its expression and functions may be modified by the differentiation phenotype of the tumor cells.

Adenocarcinoma↗

PubMed1998

Paracrine effects of hepatocyte growth factor/scatter factor on non-small-cell lung carcinoma cell lines.

We have studied the mitogenic, motogenic and morphogenic effects of hepatocyte growth factor (HGF), also known as scatter factor (SF), on 15 non-small-cell lung carcinoma (NSCLC) cell lines that have had their ras genotype determined. HGF/SF stimulated proliferation in only three cell lines and exerted no mitogenic activity on six lines. The growth of the remaining six lines was inhibited. The mitogenic effects were not related to the ras genotype of these cell lines, but the inhibitory effect was more commonly observed in cell lines with relatively high levels of Met/HGF receptor (HGFR) expression. HGF/SF induced or enhanced both scatter activity on monolayer culture and single-cell invasion in collagen gels in approximately half of these cell lines. Although the ras genotype of tumour cells did not influence the HGF/SF-induced motogenic activity, cell lines with the mutant ras genotype more commonly demonstrated a spontaneous motogenic activity than those with the wild-type ras genotype. When tumour cells were grown in collagen gels, HGF/SF induced irregular branching extensions of cell aggregates formed by five out of eight adenocarcinoma cell lines, but significant lumen morphogenesis was distinctly absent. The presence of autocrine HGF/SF loop in these tumour cell lines did not influence their spontaneous or HGF/SF-induced mitogenic, motogenic or morphogenic activities. Overall, our data suggest that stimulation of cell motility, rather than proliferation or differentiation, is the predominant paracrine effect of HGF/SF on NSCLC cells in vitro.

Carcinoma, Non-Small-Cell Lung↗

PubMed1998

Tirapazamine-cisplatin: the synergy.

Tirapazamine is a novel bioreductive agent with selective cytotoxicity against hypoxic tumour cells. Synergy with cisplatin and other chemotherapeutic agents has been shown in preclinical trials. Pharmacokinetic studies of tirapazamine have revealed that exposure increases with dose over the range of 18-450 mg m(-2) for a single dose and of 9-390 mg m(-2) for multiple doses. Plasma clearance is high. Tirapazamine has been clinically tested in combination with cisplatin at escalating doses in a phase I trial and at therapeutic doses in three separate phase II trials in patients with advanced non-small-cell lung cancer (NSCLC) in 11 study centres. Limiting toxicity for tirapazamine at an intravenous dose of 390 mg m(-2) was acute, reversible hearing loss. Other frequently observed side-effects included muscle cramping and gastrointestinal symptoms. Tirapazamine did not cause myelosuppression, and no toxic deaths were reported in these trials. The anti-tumour efficacy against previously untreated, advanced NSCLC was evaluated by cumulative intent-to-treat analysis of 132 patients. The objective response rate (confirmed by two independent measurements) was 25% [confidence interval (CI) 17.8-33.33], with a median survival of 38.9 weeks (CI 29.4-49.9). The efficacy of tirapazamine plus cisplatin shown in these trials was better than that of historical controls with cisplatin monotherapy. Two large-scale international trials have been conducted, involving more than 70 centres, to confirm these results. The CATAPULT I trial compares tirapazamine plus cisplatin with cisplatin and has finished accrual with 446 patients. The CATAPULT II trial, which is comparing tirapazamine plus cisplatin with etoposide plus cisplatin, had enrolled 550 patients by June 1997. Follow-up is ongoing. Tirapazamine is the promising first drug from a new class of cytotoxic agents with a novel mechanism of action. It can be effectively combined with cisplatin, and possibly with other agents, because of its safety profile and lack of overlapping dose-limiting toxicity, such as myelosuppression. The combination of tirapazamine and cisplatin appears to be safe and effective in the treatment of NSCLC.

Antineoplastic Agents↗

PubMed1998

Tirapazamine with cisplatin in patients with advanced non-small-cell lung cancer: a phase II study.

PURPOSE: A phase II study was conducted to evaluate the safety and efficacy of tirapazamine combined with cisplatin for the treatment of patients with advanced non-small-cell lung cancer (NSCLC). PATIENTS AND METHODS: Forty-four patients with stage IIIB/IV NSCLC were treated with a combination of tirapazamine and cisplatin. Patients received tirapazamine 260 mg/m2 administered intravenously over 2 hours, followed 1 hour later by cisplatin 75 mg/m2 administered over an additional hour, repeated every 21 days. The duration of therapy was meant to be limited to four cycles for nonresponders and eight cycles for responders. RESULTS: Ten of 44 patients (23%) showed a partial response. The estimated median survival for all patients was 37 weeks. Toxicities were treatable and included grade 3 nausea or vomiting (25%), fatigue (27.3%), and muscle cramps (4.5%). No dose reductions were necessary. CONCLUSION: The results show that tirapazamine can safely be added to cisplatin. Both the median survival and response rate observed strongly suggest that tirapazamine with cisplatin is more active than cisplatin alone.

Adult↗

PubMed1997

Cholera toxin triggers apoptosis in human lung cancer cell lines.

Cholera toxin (ChT) inhibits signals generated by multiple growth factors in human lung cancer cells, resulting in cell growth inhibition. We now report that ChT triggers apoptosis as shown by DNA fragmentation and activation of caspases cleaving poly(ADP-ribose) polymerase and lamin B. Apoptosis induced by ChT in a small cell lung cancer cell line is not affected by manipulations of intracellular cAMP through preincubation with isobutylmethylxanthine but can be modestly increased through inhibition of protein kinase C with chelerythrine. Thus, apoptosis is actively suppressed in lung cancer cells by a ChT-sensitive-growth regulatory pathway, and these observations may have significant implications in the development of novel strategies for lung cancer treatment.

1-Methyl-3-isobutylxanthine↗

PubMed1997

Characterization of intracellular calcium mobilization by bombesin-related neuropeptides in PC-3 human prostate cancer cells.

BACKGROUND: The objective of this study was to characterize the calcium mobilizing activity of bombesin-related neuropeptides in PC-3 cells. METHODS: Intracellular free Ca2+ concentration ([Ca2+]i) was measured following the administration of bombesin-related neuropeptides using spectrofluorometric monitoring of PC-3 cells loaded with Fura2/AM. RESULTS: Individual neuropeptides induced a rapid rise in [Ca2+]i immediately after stimulation in similar fashion. When two different peptides were administered simultaneously, the [Ca2+]i changes were similar to that produced by each peptide alone. However, simultaneous addition of tyr4-bombesin 100 nM and 2% serum resulted in [Ca2+]i increase greater than either alone. Sequential stimulation by same or different peptides, was not able to induce another response. However, 6 hrs after the first stimulus, a second stimulus was able to induce a similar response. CONCLUSIONS: The data indicate that all members of the bombesin-related family of neuropeptides are capable of triggering calcium mobilization in PC-3 cells via a similar signalling pathway. PC-3 cells become acutely desensitized to additional stimulation of neuropeptide. This desensitization is selective and reversible, requiring approximately 6 hrs for recovery.

Bombesin↗

PubMed1997

Angiogenesis correlates with vascular endothelial growth factor expression but not with Ki-ras oncogene activation in non-small cell lung carcinoma.

A total of 195 non-small cell lung carcinoma (NSCLC) specimens were studied for the presence of mutations in their ras family genes, for tumor vascularity, and for their immunostaining pattern with an antibody to vascular endothelial growth factor (VEGF). ras mutation was found in 37 of 104 (34.6%) adenocarcinoma specimens, in 0 of 64 squamous cell carcinomas, and in 2 of 27 (7.4%) large cell undifferentiated carcinomas. All mutations were found on the Ki-ras gene, with 37 (95%) of them on codon 12 and the remaining 2 on codon 13. Thirty (77%) of the mutations were G to T transversions. There was a correlation between increasing tumor vascularity and VEGF immunostaining score, but there was no correlation between either of them with the activation of the ras oncogene. A study of VEGF mRNA expression in 14 NSCLC cell lines also demonstrated a lack of correlation between the constitutive expression levels of VEGF and the presence or absence of ras mutation in these cell lines. The results suggest that VEGF is a major angiogenesis factor in NSCLC but that other factors beside ras mutations may influence tumor vascularity in these tumors. The two parameters may potentially serve as independent prognostic factors in NSCLC.

Alleles↗

PubMed1996

Autocrine growth loop of the epidermal growth factor receptor in normal and immortalized human bronchial epithelial cells.

Epidermal growth factor (EGF) is a potent growth factor for human normal bronchial epithelial (HBE) cells and lung cancer cells, which often demonstrate an EGF receptor (EGFR) autocrine loop. We have found that HBE cells are capable of proliferating in basal medium without EGF supplementation, and this suggests the probable presence of an active EGFR autocrine loop in non-neoplastic HBE cells. Northern blot hybridization shows that the parental and immortalized HBE cells express comparable and high levels of mRNA for EGFR, transforming growth factor-alpha (TGF-alpha), and amphiregulin (AR), but not EGF. Incubation with neutralizing monoclonal antibodies (mAb) against EGFR partially inhibits the growth of these cells. Immunohistochemistry shows that HBE cells express the TGF-alpha peptide in vitro and in vivo, however, neutralizing mAbs against TGF-alpha fail to inhibit their proliferation. In contrast, AR stimulates the growth of HBE cells. Thus, several EGF-family ligands appear to be involved functionally in the EGFR autocrine growth loop in HBE cells.

Amphiregulin↗

PubMed1996

Involvement of signal transduction pathways in lung cancer biology.

Pathways involved in the transduction of biological signals within cells overlap with those involved in oncogenesis. Previous studies have identified a number of discrete disturbances of some elements of these pathways in human lung cancer cells, by virtue of the overexpression or the mutation of certain key molecules. The sequence of biochemical events triggered by a mitogenic stimulus such as the exposure to bombesin-like peptides are being unravelled. The opportunity exists to identify additional changes involving regulatory proteins which may contribute to the regulation of these systems and which may function as suppressors of the malignant phenotype. Furthermore, the understanding of these pathways may identify targets for the pharmacological regulation of tumor cell response to mitogens which may be usable in the clinic.

Bombesin↗

PubMed1996

Bombesin receptor structure and expression in human lung carcinoma cell lines.

Mammalian bombesin-like peptides gastrin-releasing peptide (GRP) and neuromedin B (NMB) are regulatory neuropeptides involved in numerous physiologic processes, and have been implicated as autocrine and/or paracrine growth factors in human lung carcinoma. Three structurally and pharmacologically distinct bombesin receptor subtypes have been isolated and characterized: the gastrin releasing peptide receptor (GRP-R), the neuromedin B receptor (NMB-R), and bombesin receptor subtype-3 (BRS-3). The three receptors are structurally related, sharing about 50% amino acid identity. They are members of the G-protein coupled receptor superfamily with a seven predicted transmembrane segment topology characteristic of receptors in this family. The signal transduction pathway for GRP-R and NMB-R involves coupling to a pertussis-toxin insensitive G-protein, activation of phospholipase C (PLC), generation of inositol trisphosphate (IP3), release of intracellular calcium, and activation of protein kinase C. While all three bombesin receptors are activated by bombesin agonists, GRP-R, NMB-R, and BRS-3 have very different affinities for the mammalian bombesin-like peptides GRP and NMB, as well as bombesin receptor antagonists. The three bombesin receptor subtypes are expressed in an overlapping subset of human lung carcinoma cell lines. Any therapeutic strategy based on modulation of bombesin growth responses in human lung carcinoma would be well served to take into account the pharmacologic heterogeneity of the relevant receptors.

3T3 Cells↗

PubMed1996

Tallimustine is inactive in patients with previously treated small cell lung cancer. A phase II trial of the National Cancer Institute of Canada Clinical Trials Group.

Tallimustine binds to the minor groove of DNA where it alkylates the N3 position of adenine and may interfere with gene transcription. We conducted a phase II trial of Tallimustine given at a dose of 750 micrograms/m2 intravenously every 4 weeks in patients with small cell lung cancer progressing or relapsing following cisplatin or carboplatin-based chemotherapy. We treated 14 eligible patients with a performance status 0, 1 or 2, bi-dimensionally measurable disease and adequate end-organ function. The main toxicity was neutropenia with a median granulocyte count of 0.1 x 10(9) per liter (range 0-3.9) and four patients (27%) developing febrile neutropenia. In addition, most patients (93%) experienced lethargy. No objective responses were seen. A mixed response was seen in one patient and three others had stable disease for a median of 3.7 months. We conclude that Tallimustine is an ineffective agent in previously treated small cell lung cancer.

Aged↗

PubMed1996

Etoposide and doxorubicin antagonize the in vitro activity of paclitaxel in human non-small cell lung cancer cell lines.

GOAL: To explore in vitro interactions of paclitaxel with other agents also active against non-small cell lung cancer in the hope of identifying promising combinations for clinical evaluation. METHODS: We measured the cytotoxic effects of paclitaxel when used alone or in combination with vinblastine, cisplatin, etoposide or doxorubicin in final concentrations covering 3-4 Logs in up to five cell lines using a 96-well plate MTT assay. Drug interactions were analyzed with the isobologram method of Steel and Peckham and bidimensional plots. RESULTS: We detected no interactions between paclitaxel and cisplatin in two cell lines. Despite sharing a molecular site of action, there were no interactions between paclitaxel and vinblastine in two cell lines. In contrast, significant antagonism was detected between paclitaxel and etoposide or doxorubicin in 4/5 cell lines tested. CONCLUSIONS: We failed to identify potentially synergistic paclitaxel-based combinations for the treatment of non-small cell lung cancer. Whether the observed in vitro antagonism between paclitaxel and etoposide or doxorubicin predicts for similar interaction in the clinical use of these drugs in combination is unknown.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed1996

A 60-kilodalton protein in rat hepatoma cells overexpressing insulin receptor was tyrosine phosphorylated and associated with Syp, phophatidylinositol 3-kinase, and Grb2 in an insulin-dependent manner.

Tyrosine phosphorylation of cellular proteins is an early and key step after activation of the insulin receptor kinase (IRK). The study of the properties of these proteins should contribute to our understanding of insulin action. In rat hepatoma cells overexpressing human insulin receptors (HTC-IR), insulin treatment resulted in rapid tyrosine phosphorylation of proteins of 180, 94, 68, and 60 kDa. When lysates from insulin-treated cells were immunoprecipitated with anti-Syp antibody, subsequent immunoblotting identified p65 and p68, which reacted with anti-Syp, and p6O and p68, which reacted with antiphosphotyrosine antibody. Thus, insulin treatment yielded tyrosine phosphorylation of both Syp and a Syp-associated p6O molecule. When lysates from insulin-treated cells were adsorbed with a glutathione S-transferase (GST)-Syp-Src homology-2 (SH2) fusion protein, tyrosine- phosphorylated p6O was sequestered. After subjecting lysates to SDS-PAGE, the GST-SypSH2 fusion protein was found to bind to p18O, p94, and p6O. Thus, Syp associates directly with a 60-kDa IRK substrate via its SH2 domains. Syp-associated p6O differed from the 60- to 62-kDa proteins, associating with ras guanosine triphosphatase-activating protein, which also underwent modest tyrosine phosphorylation in response to insulin. Preadsorption of cell lystates with antibody against the 85-kDa subunit (p85) of phosphatidylinositol 3-kinase substantially reduced the amount of p60 subsequently immunoprecipitated by anti-Syp. Thus, p60 associates with both Syp and p85. The amount of tyrosine-phosphorylated p60 exceeded that of p180 in anti-Syp immunoprecipitates, whereas their proportion was comparable in anti-p85 immunoprecipitates. Grb2 was also observed in the anti-Syp immunoprecipitates. When lysates from insulin-treated cells were adsorbed with GST-p85SH2 domains or GST-Grb2, the subsequent eluates contained tyrosine-phosphorylated p60, as determined by immunoblotting with antiphosphotyrosine. Membrane binding assays using GST fusion proteins showed that these associations were direct. Studies in rat liver, muscle, and adipose tissue identified insulin-dependent association of Syp, Grb2, and p85 with tyrosine-phosphorylated p60 in adipose tissue only. We conclude that insulin treatment of HTC-IR cells and rat adipose tissue results in the tyrosine phosphorylation of p60, which might participate in the recruitment of downstream effectors involved in insulin signal transduction.

Adaptor Proteins, Signal Transducing↗

PubMed1996

Bombesin specifically induces intracellular calcium mobilization via gastrin-releasing peptide receptors in human prostate cancer cells.

Bombesin and gastrin-releasing peptide (GRP) are potent neuropeptides expressed by prostate cancer neuroendocrine cells and are related to the progression of this malignancy. This study characterizes bombesin receptors in human prostate cancer cell lines (PC-3, DU-145, LNCaP) and assesses the in vitro effect of bombesin on signal transduction and cell proliferation. [125I]Tyr4-bombesin binding assays (37 degrees C) and Scatchard analyses revealed the presence of a single class of high-affinity receptors with similar Kd values (1.5, 1.1 and 3.6 x 10(-10) M in PC-3, DU-145 and LNCaP cells respectively) but with significant differences in the number of binding sites per cell (47.6, 1.5 and 0.1 x 10(3) in PC-3, DU-145 and LNCaP cells respectively). Molecular characterization of the binding sites performed in PC-3 cells by cross-linking experiments and SDS/PAGE revealed a single radioactive band of 85 kDa. To determine which of the three known bombesin receptor subtypes (GRP receptor (GRP-R), neuromedin B receptor, bombesin receptor subtype-3) were expressed in the cell lines, reverse transcription/PCR analysis of cellular RNA followed by hybridization with receptor-specific cDNA was performed. This revealed the presence of GRP-R transcript in all cell lines, while neither of the other two receptor transcripts were expressed. When intracellular calcium mobilization was measured by Fura-2/AM cell labeling and spectrofluorometric monitoring, bombesin (100 nM) induced rapid calcium mobilization in both PC-3 (> 200% of baseline) and DU-145 (> 100% of baseline) cells, but not in LNCaP cells. However, as measured by 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide assay and [3H]thymidine incorporation, no growth modulation was observed with bombesin or bombesin receptor antagonist at various concentrations (0-500 nM). Our data indicate that bombesin is a potent inducer of signal transduction via GRP-R receptors in androgen-insensitive PC-3 and DU-145 prostate cancer cells. This suggests that the bombesin/GRP family of neuropeptides may play a regulatory role in the biology of androgen-independent prostate cancer.

3T3 Cells↗