ZD1839对胰腺癌细胞的生长抑制作用及机理

目的 探讨ZD1839对胰腺癌细胞的生长抑制作用机理.方法 应用MTT方法检测ZD1839对胰腺癌细胞的生长抑制作用、应用不同的生长因子刺激胰腺癌细胞的生长刺激,并检测ZD1839对不同生长因子作用的影响.应用western blot检测不同生长因子对EGF酪氨酸激酶受体的磷酸化作用,以及ZD1839对EGFR受体磷酸化的影响,并检测ZD1839对EGFR信号的下游MAPK磷酸化的影响.结果 ZD1839呈剂量依赖性抑制胰腺癌细胞的生长,ZD1839阻断EGF对胰腺癌细胞的生长刺激作用,但不阻断对IGF-1的作用.ZD1839抑制了基础的与EGF诱导的EGF受体磷酸化水平与MAPK的磷酸化水平.结论 结果表明,EGF对胰腺癌细胞有生长刺激作用,ZD1839对胰腺癌细胞的生长抑制作用是通过对抑制EGF受体磷酸化而特异性起作用的.     

Synergistic antiproliferative and apoptotic effects induced by mixed epidermal growth factor receptor inhibitor ZD1839 and nitric oxide donor in human prostatic cancer cell lines

BACKGROUND: The specific inhibitor of epidermal growth factor receptor (EGFR) tyrosine kinase, ZD1839 induces potent antitumoral effects on several advanced cancer types. The present study was undertaken to determine whether the combination of ZD1839 with an agent donating nitric oxide (NO(*)), sodium nitroprusside (SNP) results in a synergy of anticarcinogenic responses on metastatic prostate cancer (PC) cells. METHODS: The antiproliferative and apoptotic/necrotic effects of ZD1839 and SNP alone or in combination were estimated on EGF- and serum-stimulated LNCaP, DU145, and PC3 cells by MTT growth tests, trypan blue dye exclusion method, and flow cytometric analyses. Moreover, the cellular ceramide levels were evaluated by the diacylglycerol kinase enzymatic method and the amounts of cytosolic cytochrome c by ELISA assays. RESULTS: ZD1839 and SNP alone or in combination at lower concentrations induced an inhibition of EGF- and serum-stimulated growth of LNCaP, DU145, and PC3 concomitant with an arrest in the G1 phase of cellular cycle. Interestingly, the mixed ZD1839 and SNP also caused a more substantial apoptotic/necrotic death of these PC cells as compared to drugs alone. Moreover, we have observed that an inhibition of acidic sphingomyelinase, hydrogen peroxide (H(2)O(2)) accumulation and caspase cascades results in a significant reduction of apoptotic/necrotic death induced by mixed ZD1839 and SNP in EGF-stimulated PC3 cells. In addition, the combined ZD1839 plus SNP also induced a higher cellular ceramide and reactive oxygen species (ROS) production, mitochondrial transmembrane potential decrease, and cytochrome c amount released into cytosol as compared to drugs alone. CONCLUSIONS: The simultaneous use of EGFR inhibitor and compound releasing NO(*) might lead to a synergy in the ceramide and ROS production which might cause cellular membrane damages resulting in a massive apoptotic/necrotic death of metastatic PC cells.     

Inhibition of the epidermal growth factor receptor enhances castration-induced prostate involution and reduces testosterone-stimulated prostate growth in adult rats

BACKGROUND: The epidermal growth factor receptor (EGFR) mediates regulatory signals in the normal prostate, but the functional importance of this is unclear. METHODS: Adult male rats were castrated, or castrated + treated with gefitinib (Iressa, ZD1839), an EGFR tyrosine kinase inhibitor, for 3 days. Seven-day castrated rats were treated with testosterone, or testosterone + gefitinib, for 3 days. RESULTS: Both castration alone and testosterone treatment in castrated animals increased the mRNA and protein levels of EGFR and phospho-EGFR in the ventral prostate. Inhibition of EGFR during castration and during testosterone-stimulated prostate growth resulted in a decrease in total epithelial weight, epithelial cell proliferation, endothelial cell proliferation, and increased epithelial cell apoptosis. CONCLUSIONS: This study suggests that increased EGFR signaling during castration mediates stimulatory effects balancing castration-induced prostate regression, and that EGFR signaling is a necessary component in testosterone-stimulated prostate growth.     

Antiangiogenic effect of ZD1839 against murine renal cell carcinoma (RENCA) in an orthotopic mouse model

INTRODUCTION: ZD1839 (Iressa) is a selective epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI). We evaluated the antitumor and antiangiogenesis activities of ZD1839 in a murine renal cell carcinoma (RENCA) model. MATERIALS AND METHODS: The effect of ZD1839 on the cellular proliferation of RENCA cells in vitro was measured by colorimetric assay. For the in vivo studies, RENCA cells were adsorbed in Gelfoam and implanted into BALB/cJ mouse parenchyma with an agarose bar. Mice were treated with ZD1839 (40 mg/kg/day s.c.), genistein or saline for 14 days. Western blot analysis was performed to observe EGFR expression in RENCA cells and tumor tissues. Microvessel density (MVD) was quantified by immunostaining for factor VIII-related antigens and VEGF level was assayed by ELISA. RESULTS: ZD1839 showed a dose-dependent inhibition of RENCA cellular proliferation. ZD1839 treatment resulted in a marked decrease in tumor growth compared with saline treatment. The MVD and VEGF in the RENCA tumors were decreased significantly by ZD1839 (p<0.01 and p>0.05, respectively). Genistein also suppressed tumor growth and decreased MVD and VEGF level, but the efficacies were less than with ZD1839. CONCLUSION: The suppressive activity of ZD1839 on RENCA tumor growth was accompanied by decreases in the MVD and VEGF production. These results suggest that the antitumor effect of ZD1839 in a RENCA model is mediated partially by the inhibition of tumor angiogenesis.     

Molecular target-based cancer therapy: epidermal growth factor receptor inhibitors

Based on recent progress in cancer biology, numerous molecules that contribute to proliferation, invasion, and metastasis of cancer cells have been identified. The epidermal growth factor receptor (EGFR), a member of cell membrane receptors, is overexpressed by many tumors, and EGFR overexpression correlates with poor prognosis and disease progression. The EGFR is an attractive target for novel anticancer therapy. ZD1839 and OSI-774, highly specific EGFR tyrosine kinase inhibitors, have shown promising antitumor activity against cisplatin-resistant non-small cell lung cancer in phase I and phase II trials. IMC-C225, a monoclonal antibody against EGFR, has achieved significant disease control in head and neck cancer and colorectal cancer in combination with anticancer agents. These agents are under evaluation in phase III trials. In conclusion, it is expected that EGFR-directed therapies will soon be established as an effective novel treatment for many cancer patients.     

Results of the Southwest Oncology Group phase II evaluation (study S0031) of ZD1839 for advanced transitional cell carcinoma of the urothelium

Study Type – Prognosis (inception cohort)
Level of Evidence 1b

OBJECTIVE

To evaluate the epidermal growth factor receptor (EGFR)‐targeted agent ZD1839 in patients who failed one previous chemotherapeutic regimen for metastatic transitional cell carcinoma (TCC), and to correlate patterns of response with the expression of EGFR.

PATIENTS AND METHODS

Thirty‐one patients with metastatic TCC of the urothelial tract were treated with ZD1839 500 mg oral daily. Patients were required to have a pretreatment biopsy to assess EGF expression.

RESULTS

The median progression‐free survival was 2 months, with only two patients (6.5%) surviving past 6 months with no disease progression. Thirty patients were evaluable for toxicity; there was grade 4 cerebrovascular ischaemia and an increase in creatinine level. All patients were evaluable for response, with one confirmed partial response (3%; 95% confidence interval, CI, 0–17%) in a patient with pulmonary metastases. All patients have died, and the estimated median (95% CI) survival is 3 (2–7) months.

CONCLUSIONS

ZD1839 is ineffective as a second‐line agent for urothelial carcinoma.     

Immune-enhancing enteral diet selectively augments ileal blood flow in the rat

BACKGROUND: Prior indirect studies have suggested that a functional epidermal growth factor receptor (EGFR) appears to be indispensable for the adaptive response of the remnant intestine to massive small bowel resection (SBR). The recent availability of a specific pharmacologic EGFR inhibitor enabled us to more directly test the hypothesis that EGFR signaling is required for postresection intestinal adaptation. METHODS: Mice (C57B1/6, n = 26) underwent a 50% SBR or sham operation and were then given orogastric EGFR inhibitor (ZD1839, 50 mg/kg/day) or vehicle. After 3 days, indices of adaptation (wet weight, crypt depth, and villus height) and apoptotic index (number of apoptotic bodies per crypt) were calculated in the ileum. The expression of proliferating cell nuclear antigen (PCNA) and activated EGFR was measured by Western blotting. RESULTS: ZD1839 prevented EGFR activation and the normal postresection increases in ileal wet weight, villus height, and crypt depth. Enterocyte proliferation was reduced twofold in the SBR group by ZD1839. Although not statistically significant, rates of enterocyte apoptosis were the highest in the inhibitor-treated mice. CONCLUSION: Following massive SBR, pharmacologic inhibition of the EGFR attenuates proliferation and the normal adaptive response of the intestine. These results more directly confirm the requirement of a functional EGFR as a mediator of the postresection adaptation response. This study demonstrates an in vivo application of a novel selective EGFR inhibitor and offers a unique experimental model to gain mechanistic insight into understanding postresection intestinal adaptation.     

Blockade of growth factor receptors in ductal carcinoma in situ inhibits epithelial proliferation

BACKGROUND: Ductal carcinoma in situ (DCIS) expresses c-erbB-2 receptor and epidermal growth factor receptor (EGFR). The aim of this study was to determine whether blocking of c-erbB-2 receptor with a humanized monoclonal antibody, 4D5 (HerceptinTM), or of EGFR with an epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI), ZD1839 (IressaTM), would decrease epithelial proliferation in DCIS. METHODS: DCIS tissue from 18 women undergoing surgery was implanted into 16 to 20 athymic nude mice per experiment (eight xenografts per mouse). Treatment commenced 2 weeks after implantation and consisted either of twice-weekly intraperitoneal injections of 4D5 10 mg/kg or of daily gavage with ZD1839 at 100-200 mg/kg for 14 days; appropriate controls were included. Xenografts were removed on days 14, 21 and 28. Proliferation was assessed by counting 1000 epithelial cells after Ki67 immuno- staining. RESULTS: ZD1839 inhibited proliferation compared with that in controls after 14 days (P < 0.01), whereas 4D5 did not. CONCLUSION: Proliferation in DCIS was decreased by EGFR tyrosine kinase inhibition but not by c-erbB-2 receptor blockade. ZD1839, an orally active and selective EGFR-TKI, has potential as adjuvant therapy in DCIS.     

Looking to the Future: Advances in the Management of Hormone-Refractory Prostate Cancer

At present there are no effective treatment options for patients with hormone-refractory prostate cancer (HRPC) and current medical management is largely palliative. Therefore, there is a need for novel, non-cytotoxic treatment approaches in HRPC. Cancer development is a multistep process, involving initiation, proliferation, angiogenesis, invasion, and metastasis, each of which present potential targets for anticancer therapy. A number of agents exploiting each of these cellular targets are in clinical development and are reviewed in this article, particularly: inhibitors of the epidermal growth factor signalling cascade (e.g. cetuximab, trastuzumab, and ZD1839 [‘Iressa’]); endothelin-A receptor antagonists (e.g. atrasentan); and angiogenesis inhibitors (e.g. ZD6474 and PTK 787). Other potential approaches include novel uses of existing compounds, inhibition of invasion/metastasis, induction of apoptosis, and gene therapy. These novel approaches and agents have the potential to be used in sequence or combination with established therapies, but also in combination with other new treatments. New, targeted biological therapies should lead to many more therapeutic options and better outcomes for patients with prostate cancer, particularly those with HRPC.     

Evidence in Advanced Disease: The Challenge for New Therapies

Prostate cancer mortality rates have recently begun to decline, however, the large number of people with advanced prostate cancer continues to make this disease an important healthcare problem. A range of new agents are in development, resulting in the need for new methods of rapid evaluation. The use of surrogate markers for survival has been proposed as a means of gaining an early indication of the effectiveness of treatment. Prostate-specific antigen (PSA) is a strong candidate for a marker of activity in advanced prostate cancer. However, PSA alone has not yet complied with the strict criteria for surrogacy, which requires evidence that a significant difference between treatments in a randomised trial correlates with a significant difference in the potential surrogate marker. Despite preclinical studies showing that PSA response is not always associated with a reduction in tumour size, and reports that a proportion of men with prostate cancer will progress clinically without a rise in PSA level, emerging evidence indicates that changes in PSA levels predict survival in advanced disease. An algorithm has been developed involving confirmation of activity in an experimental animal model in parallel with clinical studies, in order to gain a full picture of the potential of new treatments for prostate cancer. This algorithm is currently being used in a Phase II study of the orally active, selective, epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) ZD1839 (‘Iressa’)¹ in patients with prostate cancer experiencing rising PSA levels while undergoing endocrine treatment. Results from this and other PSA-based trials are awaited with interest, as they may clarify the role of PSA change as a surrogate marker for survival in patients with advanced prostate cancer.     

Hedgehog signalling in androgen independent prostate cancer

Objectives

Androgen-deprivation therapy effectively shrinks hormone-naïve prostate cancer, both in the prostate and at sites of distant metastasis. However prolonged androgen deprivation generally results in relapse and androgen-independent tumour growth, which is inevitably fatal. The molecular events that enable prostate cancer cells to proliferate in reduced androgen conditions are poorly understood. Here we investigate the role of Hedgehog signalling in androgen-independent prostate cancer (AIPC).

Methods

Activity of the Hedgehog signalling pathway was analysed in cultured prostate cancer cells, and circulating prostate tumour cells were isolated from blood samples of patients with AIPC.

Results

AIPC cells were derived through prolonged culture in reduced androgen conditions, modelling hormone therapy in patients, and expressed increased levels of Hedgehog signalling proteins. Exposure of cultured AIPC cells to cyclopamine, which inhibits Hedgehog signalling, resulted in inhibition of cancer cell growth. The expression of the Hedgehog receptor PTCH and the highly prostate cancer–specific gene DD3^PCA3 was significantly higher in circulating prostate cancer cells isolated from patients with AIPC compared with samples prepared from normal individuals. There was an association between PTCH and DD3^PCA3 expression and the length of androgen-ablation therapy.

Conclusions

Our data are consistent with reports implicating overactivity of Hedgehog signalling in prostate cancer and suggest that Hedgehog signalling contributes to the androgen-independent growth of prostate cancer cells. As systemic anti-Hedgehog medicines are developed, the Hedgehog pathway will become a potential new therapeutic target in advanced prostate cancer.     

Targeting the EGF/VEGF-R system by tyrosine-kinase inhibitors—a novel antiproliferative/antiangiogenic strategy in thyroid cancer

Aim In thyroid cancer (TC), endothelial growth factor (EGF) has been associated with dedifferentiation, tumor cell proliferation, and angiogenesis. Vascular endothelial growth factor (VEGF) has been documented to be the main stimulator of angiogenesis in the thyroid gland. Patients with undifferentiated thyroid cancer are in desperate need of new therapeutic strategies because common protocols of therapy usually fail. The aim of this study, therefore, was to evaluate two tyrosine-kinase inhibitors (TKI, ZD 1839 gefitinib and ZD 6474 vandetanib), directed against the EGF/VEGF receptor for possible antitumor therapy in thyroid cancer.Methods EGF/VEGF-R was documented in anaplastic (Hth74, C643), follicular (FTC133), and papillary (TPC1) thyroid cancer cell lines by Western blot analysis. The antiproliferative effect of two TKI (0.1–10 μM) on thyroid cancer cell lines in vitro was quantified by MTT assay, the antiangiogenic effect by assessing secretion of VEGF by enzyme-linked immunosorbent assay (R&D Systems). ZD 1839 is mainly directed against EGF-R and ZD 6474 against VEGF-R (AstraZeneca, UK), single applications and combinations of compounds were evaluated.Results EGF-R and VEGF-R as well as the phosphorylated receptor were documented in all of the cell lines. Administration of ZD1839 led to an up to 90% reduction of cell number in Hth74, 80% in C643, 50% in FTC133, and 90% in TPC1 (p < 0.05). ZD1839 induced a decrease of VEGF secretion between 30% in C643 and 90% in Hth74. Administration of ZD6474 led to an up to 95% reduction of cell number in Hth74, 85% in C643, 90% in FTC133, and 90% in TPC1 (p < 0.05). The ZD6474 induced decrease of VEGF secretion ranged between 20% (FTC133) and 60% (TPC1). Combinations of IC50 concentrations of TKI showed synergistic effects, resulting in additional inhibition of proliferation between 50 and 90% compared to single drug administration.Conclusion The EGF/EGF-R system resembles a powerful VEGF-stimulating pathway in all histiotypes of TC and can be inhibited by TKI. TKI directed against EGF-R as well as VEGF-R inhibit tumor cell proliferation and VEGF secretion in vitro. Combinations of TKI are more effective than strategies using single agents. It is suggested that targeting EGF-R/VEGF-R-mediated pathways may have therapeutic potential in some undifferentiated thyroid cancers.Presented at the 2nd Biennal Congress of the ESES, May 2006, Krakow, Poland.     

A serum factor after intestinal resection stimulates epidermal growth factor receptor signaling and proliferation in intestinal epithelial cells

BACKGROUND: In vivo, intestinal adaptation after massive small bowel resection (SBR) requires a functional epidermal growth factor (EGF) receptor (EGFR). In vitro studies have shown that serum from mice after SBR induces rat intestinal epithelial cells to proliferate. This study tested the hypothesis that the proliferative response to SBR serum is mediated by EGFR signaling. METHODS: Serum was collected from male Sprague-Dawley rats 7 days after 75% SBR or sham operation. Rat intestinal epithelial cells were incubated in the presence of sham or SBR serum. Total EGFR expression and phosphorylation of several EGFR downstream pathways were determined by Western blotting. In other experiments, a specific EGFR inhibitor (ZD1839) was added and cell growth determined over 5 days. RESULTS: SBR serum significantly increased total EGFR expression (3-fold) over sham operation and consistently activated the phosphatidylinositol 3-kinase pathway. Furthermore, SBR serum markedly augmented rat intestinal epithelial cell growth, an effect that was abolished by EGFR inhibition. CONCLUSIONS: SBR serum contains a factor or factors that stimulates proliferation of intestinal epithelial cells by an EGFR and phosphatidylinositol 3-kinase signaling mechanism. These data recapitulate in vivo studies supporting the hypothesis that EGFR is a central mediator of postresection intestinal adaptation. This in vitro model may provide a novel means to gain insight into the pathophysiology of intestinal adaptation.     

The Role of the Epidermal Growth Factor Receptor in Breast Cancer

Recent trials of drug therapy targeting the erbB receptor HER2 have met with success in breast cancer. The epidermal growth factor receptor or EGFR is a closely related receptor from this same family that is involved in cellular signal transduction and tumor cell growth and survival. Emerging evidence indicates that EGFR is implicated in the development of hormone-resistant breast cancer, and that its activity is intertwined with estrogen receptor. Here, the role of EGFR in breast cancer is reviewed, and data from selected clinical trials of signal transduction inhibition of this cellular target are summarized.     

The Specific Endothelin A Receptor Antagonist ZD4054: Preclinical and Clinical Results

ContextZD4054 is a specific endothelin A (ET_A) receptor antagonist being investigated for the treatment of hormone-resistant prostate cancer (HRPC). ZD4054 binds specifically to the ET_A receptor, with no detectable activity at the ET_B receptor. In preclinical studies, ZD4054 inhibited endothelin (ET-1)-mediated changes in cellular invasiveness in vitro, and inhibited angiogenesis and growth of tumour xenografts in vivo. Consistent with its specific binding profile, ZD4054 inhibited ET_A-receptor-mediated antiapoptotic events while allowing ET_B-receptor-mediated proapoptotic signalling.Evidence acquisitionThe preclinical and clinical activity of ZD4054 is reviewed.Evidence synthesisIn the clinical setting, stable levels of circulating ET-1 following single ZD4054 doses up to 240 mg demonstrated the absence of ZD4054 activity at the ET_B receptor. ZD4054 is cleared principally via the urine, with a terminal elimination half-life of approximately 8–12 hours and with little accumulation after once-daily oral dosing.In a Phase 2 trial, patients with metastatic HRPC who were pain free or mildly symptomatic for pain were randomized to once-daily oral tablets of ZD4054 10 mg (n = 107), or 15 mg (n = 98), or matched placebo (n = 107). ZD4054 was generally well tolerated in this population, with an adverse effect profile consistent with its known pharmacological activity. The most common adverse effects were headache, peripheral oedema and nasal congestion. At the primary analysis there was no statistically significant difference in time to progression between the ZD4054-treated groups and placebo (hazard ratio [HR]: ZD4054 10 mg, 0.88 [80% CI 0.71, 1.09]; ZD4054 15 mg, 0.83 [0.66, 1.03]). However, a promising signal for prolonged overall survival was observed, which was sustained at a subsequent analysis (HR versus placebo: ZD4054 10 mg, 0.55 [80% CI 0.41, 0.73]; ZD4054 15 mg, 0.65 [0.49, 0.86]).ConclusionsThese results support the strategy of targeting the ET_A receptor in prostate cancer, and mandate further investigation of ZD4054 in Phase 3 clinical trials.     

Increase in amphiregulin and epiregulin in prostate cancer xenograft after androgen deprivation-impact of specific HER1 inhibition

BACKGROUND: We investigated the expression of the epidermal growth factor (EGF) network before and after castration in the prostate cancer xenograft CWR22 implanted in nude mice, and examined the effects of gefitinib (Iresssa, ZD1839), a new drug directed towards the EGF tyrosine kinase receptor (HER1) of the EGF network. METHODS: CWR22 prostate cancer xenografts were propagated in immunodeficient male mice. The expression of the growth factors and receptors in the EGF network was examined by real-time PCR analysis and ELISA at 0, 7, 14, and 30 days after castration, and the tumor growth was examined after treatment with gefitinib or placebo. RESULTS: A fraction of growth factors showed a steady increase in the mRNA expression reaching between fourfold and eightfold 30 days after castration, including amphiregulin (P < 0.005) and epiregulin (P < 0.001). ELISA for amphiregulin showed a fivefold increase 30 days after castration. Tumor bearing mice were castrated and treated with or without the HER1 tyrosine kinase inhibitor gefitinib. Tumor involution was significantly increased by castration plus gefitinib as compared to castration alone. CONCLUSIONS: Castration leads to adaptive increase in the concentrations of a subset of growth factors from the EGF network in the androgen sensitive CWR22 prostate cancer xenograft. Specific inhibition of the HER1 tyrosine kinase receptor significantly increases the tumor involution, and suggests that HER1 targeted drugs could be of therapeutic relevance in the treatment of advanced prostate cancer.     

Flutamide in hormone-resistant prostatic cancer.

Flutamide (250 mg. orally 3 times daily) yielded a subjective response in 5 of 25 fully evaluable patients with hormone-resistant prostatic cancer. Four additional patients had early progression. A 40% or greater decrease in the pre-treatment prostate specific antigen level was observed in 7 of 24 patients and this finding was correlated with improved survival. Toxicity was mainly gastrointestinal and resulted in permanent discontinuation of flutamide in 5 patients. Flutamide or similar antiandrogens may have a role in the management of hormone-resistant prostatic cancer when relief of subjective symptoms should be an important treatment goal together with improvement of survival. However, before the drug should be used routinely in the management of hormone-resistant prostatic cancer phase 3 studies must confirm its effectiveness, especially in comparison to less expensive drugs.     

Androgen receptor and prostate cancer invasion

Evidence indicates that androgen-sensitive prostate cancer cells have a lower malignant potential. We previously demonstrated that expression of androgen receptor (AR) by transfection of the androgen-independent prostate cancer cell line PC3 decreases invasion and adhesion of these cells through modulation of alpha6beta4 expression. Treatment with the androgen further reduced adhesion and invasion of the cells without, however, modifying alpha6beta4. Here we investigated whether the androgen has a direct effect on alpha6beta4-EGF receptor (EGFR) interaction and signalling leading to invasion of these cells. Immunoconfocal microscopy demonstrated that in control cells (PC3-Neo), alpha6beta4 and EGFR colocalize and redistribute in response to epidermal growth factor (EGF). In PC3-AR cells colocalization and redistribution between the two molecules was reduced and abolished by pre-treatment with R1881. Co-immunoprecipitation studies demonstrated that tyrosine phosphorylation of beta4 in response to EGF was reduced in PC3-AR cells compared to PC3-Neo. Immunoconfocal and co-immunoprecipitation studies demonstrated colocalization at membrane level and co-immunoprecipitation of EGFR and AR, indicating an interaction between the two proteins. PI3K activity, a key signalling pathway for invasion of these cells, was decreased in PC3-AR cells in response to EGF and further reduced by treatment with R1881. EGFR internalization was strongly reduced in PC3-AR compared with PC3-Neo cells and was reduced by treatment with R1881. In conclusion, the expression of AR by transfection in PC3 cells confers a less malignant phenotype by interfering with EGFR--alpha6beta4 interaction and signalling leading to invasion through a mechanism involving an interaction between the classic AR and EGFR.     

Influence of linomide on local tumor growth and metastasis of the human hormone-resistant prostate cancer cell line PC3 in an orthotopic model

OBJECTIVE:It has been demonstrated that quinoline-3-carboxamide, linomide, inhibited angiogenesis and reduced the volume of tumors grown from human hormone-resistant prostate cancer cell lines after subcutaneous implantation in mice. However, subcutaneous xenograft models may not mimic human conditions due to the absence of prostatic stromal cells at the ectopic site. Therefore, we investigated the influence of linomide on local tumor growth and metastasis of the human hormone-resistant prostate cancer cell line PC-3 in an orthotopic model. METHODS: In 30 athymic nude mice, 5x10(5) PC-3 cells were injected into the dorsal prostate after surgical exposure. After 7 days, group 1 (n = 15 mice) received linomide 100 mg/kg/day in the drinking water (per os). The other 15 mice (group 2) served as controls. All mice were sacrificed after 38 days followed by macroscopical and histological evaluation of local tumor growth and metastasis. Microvessel density was determined by immunohistochemical staining for von Willebrand factor as well as silver staining followed by morphometric analysis in an area of highest vessel density. RESULTS: In the control group, local tumorigenicity and locoregional lymph node metastasis was 100%. The mean weight of the local tumor was 894 mg (395- 1,261 mg). The mean transversal diameter of the lymph node metastases was 4.0 mm (1.5-5. 4 mm). In the treatment group, local tumor growth and lymph node metastasis was 100% with a mean local tumor weight of 869 mg (232-1, 131 mg) and a mean lymph node metastasis diameter of 4.6 mm (1.3-5.9 mm). Microvessel density of the local tumor in the control and treatment group did not differ significantly. CONCLUSION: Contrary to the results reported in subcutaneous animal models, linomide per os has no effect on net tumor growth and metastasis after orthotopic implantation of the human hormone-resistant prostate cancer cell line PC-3 in nude mice.     

Dual epidermal growth factor receptor and vascular endothelial growth factor receptor inhibition with vandetanib sensitizes bladder cancer cells to cisplatin in a dose‐ and sequence‐dependent manner

OBJECTIVE

To investigate the activity of the combination of vandetanib and cytotoxic agents using in vitro models of bladder cancer, as modern chemotherapy regimens are built around cisplatin, with gemcitabine or a taxane such as docetaxel also commonly added in combination for the treatment of advanced bladder cancer.

MATERIALS AND METHODS

Human bladder cancer cells HTB3, HT1376, J82, RT4, CRL1749, T24, SUP and HTB9 were cultured. The activity of gefitinib (ZD1839) and vandetanib (ZD6474) was assessed in these eight bladder cancer cell lines with a tetrazolium‐based assay of cell viability. RT4 bladder cancer cells, determined to have moderate cisplatin resistance and also moderate sensitivity to vandetanib, were treated with vandetanib and cisplatin. RT4 and T24 cells were treated with six different regimens. The apoptosis and cell‐cycle analysis were studied by flow cytometry. Expression of p21 and p27 was detected by Western blotting. Fluorescence in situ hybridization (FISH) analysis of epidermal growth factor receptor (EGFR) and human epidermal growth factor receptor 2 was performed for all cell lines.

RESULTS

At equal concentrations, vandetanib was a more potent inhibitor of cell viability, compared to gefitinib. At vandetanib concentrations of ≤2 µM, the combination with cisplatin was synergistic, especially in the treatment sequence of cisplatin followed by vandetanib, and additive with vandetanib followed by cisplatin. An analysis of the cell‐cycle distribution showed that vandetanib treatment induced G1 arrest at high concentrations, but not at lower concentrations. High‐concentration treatment was associated with increased levels of the cyclin‐dependent kinase p27. FISH analysis showed that there was a low level of genomic gain, and no gene amplification. Mutational analysis of exons 18, 19, and 21 of EGFR in each cell line revealed no mutation.

CONCLUSION

Vandetanib has synergistic activity when given at low concentration with cytotoxic chemotherapy. The addition of vandetanib to cisplatin‐based chemotherapy regimens merits further study.