Observations on EGFR gene amplification and polymorphism in prostatic diseases

Functional and mutational analysis after radiation and cetuximab treatment on prostate carcinoma cell line DU145

Background

Epidermal Growth Factor Receptor is often overexpressed in advanced prostate carcinoma. In-vitro-studies in prostate carcinoma cell line DU145 have demonstrated increased sensibility to radiation after cetuximab treatment, but clinical data are not sufficient to date.

Methods

We analyzed effects of radiation and cetuximab in DU145 and A431 using proliferation, colony-forming-unit- and annexin-V-apoptosis-assays. Changes in protein expression of pEGFR and pERK1/2 after radiation and cetuximab treatment were analyzed. Using NGS we also investigated the impact of cetuximab long-term treatment.

Results

Cell counts in DU145 were reduced by 44% after 4 Gy (p = 0.006) and 55% after 4 Gy and cetuximab (p < 0.001). The surviving fraction (SF) was 0.69 after 2 Gy, 0.41 after 4 Gy and 0.15 after 6 Gy (each p < 0.001). Cetuximab treatment did not alter significantly growth reduction in 4 Gy radiated DU145 cells, p > 0.05 or SF, p > 0.05, but minor effects on apoptotic cell fraction in DU145 were detected. Using western blot, there were no detectable pEGFR and pERK1/2 protein signals after cetuximab treatment. No RAS mutation or HER2 amplification was detected, however a TP53 gen-mutation c.820G > T was found.

Conclusions

Radiation inhibits cell-proliferation and colony-growth and induces apoptosis in DU145. Despite blocking MAP-Kinase-pathway using cetuximab, no significant radiation-sensitizing-effect was detected. Cetuximab treatment did not induce resistance-mutations. Further research must clarify which combination of anti-EGFR treatment strategies can increase radiation-sensitizing-effects.

EGF promotes the shedding of soluble E-cadherin in an ADAM10-dependent manner in prostate epithelial cells

During the progression of prostate cancer, the epithelial adhesion molecule E-cadherin is cleaved from the cell surface by ADAM15 proteolytic processing, generating an extracellular 80kDa fragment referred to as soluble E-cadherin (sE-cad). Contrary to observations in cancer, the generation of sE-cad appears to correlate with ADAM10 activity in benign prostatic epithelium. The ADAM10-specific inhibitor INCB8765 and the ADAM10 prodomain inhibit the generation of sE-cad, as well as downstream signaling and cell proliferation. Addition of EGF or amphiregulin (AREG) to these untransformed cell lines increases the amount of sE-cad shed into the conditioned media, as well as sE-cad bound to EGFR. EGF-associated shedding appears to be mediated by ADAM10 as shRNA knockdown of ADAM10 results in reduced shedding of sE-cad. To examine the physiologic role of sE-cad on benign prostatic epithelium, we treated BPH-1 and large T immortalized prostate epithelial cells (PrEC) with an sE-cad chimera comprised of the human Fc domain of IgG(1), fused to the extracellular domains of E-cadherin (Fc-Ecad). The treatment of untransformed prostate epithelial cells with Fc-Ecad resulted in phosphorylation of EGFR and downstream signaling through ERK and increased cell proliferation. Pre-treating BPH-1 and PrEC cells with cetuximab, a therapeutic monoclonal antibody against EGFR, decreased the ability of Fc-Ecad to induce EGFR phosphorylation, downstream signaling, and proliferation. These data suggest that ADAM10-generated sE-cad may have a role in EGFR signaling independent of traditional EGFR ligands.

The EGFR polymorphism rs884419 is associated with freedom from recurrence in patients with resected prostate cancer

PURPOSE

Prognostic biomarkers are needed to optimize treatment decisions for prostate cancer. Single nucleotide polymorphisms participate in the individual genetic background modulating risk and clinical outcomes of cancer. We tested whether EGFR polymorphisms are associated with prostate cancer clinical outcomes.

MATERIALS AND METHODS

The study population consisted of 212 patients with clinically localized prostate cancer treated with radical prostatectomy from 1997 to 1999. Resected prostatic tissues were genotyped with allele specific probes for 9 haplotype tagging single nucleotide polymorphisms, which were located in intronic, exonic and flanking regions of linkage disequilibrium in the EGFR gene. Correlations between alleles, and recurrence and survival data were investigated using univariate and multivariate genetic analysis models.

RESULTS

There was a statistically significant association between the single nucleotide polymorphism rs884419 and prostate cancer recurrence, as defined in the study by at least prostate specific antigen biochemical recurrence (log rank test p <0.001). The incidence of the recurrence risk enhancing genotype A/A was 3.1% vs 17.4% and 80% for the risk decreasing genotypes A/G G/G, respectively. Based on Cox proportional hazard regression modeling patients carrying G/G and A/G genotypes were associated with a decreased risk of prostate cancer recurrence compared to those with the A/A genotype (HR 0.10, 95% CI 0.02-0.41 and 0.13, 95% CI 0.04-0.46, respectively, p <0.002).

CONCLUSIONS

These data suggest that a polymorphism flanking the EGFR gene is an independent prognostic genetic biomarker that predicts prostate cancer biochemical recurrence after radical prostatectomy.

Multicenter phase II study of erlotinib, an oral epidermal growth factor receptor tyrosine kinase inhibitor, in patients with recurrent or metastatic squamous cell cancer of the head and neck

PURPOSE

To determine the efficacy and safety profiles of erlotinib in patients with advanced recurrent and/or metastatic squamous cell cancer of the head and neck (HNSCC).

PATIENTS AND METHODS

Patients with locally recurrent and/or metastatic HNSCC, regardless of their HER1/EGFR status, were treated with erlotinib at an initial dose of 150 mg daily. Dose reductions or escalations were allowed based on tolerability of erlotinib.

RESULTS

One-hundred fifteen patients were enrolled onto this study. Forty-seven percent of patients received erlotinib at 150 mg daily throughout the entire study, 6% had dose escalations, and 46% required dose reductions and/or interruptions. Five patients achieved partial responses on study, for an overall objective response rate of 4.3% (95% CI, 1.4% to 9.9%). Disease stabilization was maintained in 44 patients (38.3%) for a median duration of 16.1 weeks. The median progression-free survival was 9.6 weeks (95% CI, 8.1 to 12.1 weeks), and the median overall survival was 6.0 months (95% CI, 4.8 to 7.0 months). Subgroup analyses revealed a significant difference in overall survival favoring patients who developed at least grade 2 skin rashes versus those who did not (P =.045), whereas no difference was detected based on HER1/EGFR expression. Rash and diarrhea were the most common drug-related toxicities, encountered in 79% and 37% of patients, respectively, though the severity was mild to moderate in most cases.

CONCLUSION

Erlotinib was well tolerated in this heavily pretreated HNSCC population and produced prolonged disease stabilization; hence, further evaluation of its role in this tumor type is warranted.

Study on the mechanism of epidermal growth factor-induced proliferation of hepatoma cells

AIM: Many growth factors, such as epidermal growth factor (EGF), are associated with the carcinogenesis. EGF plays its role in the proliferation of hepatoma cells through binding with EGF receptor (EGFR) and a series of signal transduction. But the postreceptor pathway is still not clear. In the present experiment, we studied the effect of tyrosine kinase, protein kinase C, Na⁺/H⁺ exchange, calmodulin and voltage-dependent Ca²⁺ channel on EGF-induced hepatoma cell proliferation.

METHODS: Hepatoma cell line SMMC7721 was cultured in RPMI1640 serum-free medium. In order to study the effect of thyrosine kinase, protein kinase C, Na⁺/H⁺ exchange, calmodulin and voltage-dependent Ca²⁺ channel on human heptoma cell proliferation induced by epidermal growth factor (EGF), DNA synthesis rate of hepatoma cells was measured by the method of ³H-TdR incorporation.

RESULTS: EGF (10^-9 M) stimulated the proliferation of heptoma cells significantly (³H-TdR incorporation was 1880 ± 281 cpm/well, P < 0.05), and this effect was significantly inhibited by tyrosine kinase inhibitor genistein (³H-TdR incorporation was 808 ± 209 cpm/well, P < 0.001). Calmodulin inhibitor W-7, protein kinase C inhibitor H-7 and Na⁺/H⁺ exchange inhibitor amiloride individually had significant inhibiting effect on EGF-induced proliferation of hepatoma cells (³H-TdR incorporation was 978 ± 87.3 cpm/well, 1241 ± 147 cpm/well, 1380 ± 189 cpm/well, respectivly, P < 0.001, P < 0.01, P < 0.05), but they all had no effect on the basal level proliferation of cultured hepatoma cells (³H-TdR incorporation was 1284 ± 260 cpm/well, 1179 ± 150 cpm/well, 1392 ± 152 cpm/well, respectivly, ³H-TdR incorporation of the control was 1353 ± 175 cpm/well, P > 0.05). Voltage-dependent Ca²⁺ channel inhibitor verapamil had no inhibition on EGF-induced proliferation of hepatoma cells (³H-TdR incorporation was 1637 ± 133 cpm/well, P > 0.05), it also had no effect on the basal level proliferation of cultured hepatoma cells (³H-TdR incorporation was 1196 ± 12 cpm/well, P > 0.05).

CONCLUSION: Our data suggest that tyrosine kinase, Ca²⁺-calmodulin-dependent pathway, protein kinase C and Na⁺/H⁺ exchange play a critical role in EGF-induced proliferation of hepatoma cells and that the effect of EGF is independent of voltage-dependent Ca²⁺ channel.

Transition to androgen-independence in prostate cancer

Prostate carcinoma is the most frequently diagnosed malignancy and the second leading cause of death as a result of cancer in men in the western countries. Withdrawal of androgens or the peripheral blockage of androgen action remain the critical therapeutic options for the treatment of advanced prostate cancer. However, after initial regression, most of the prostate cancers become androgen-independent and progress further, with eventual fatal outcome. Understanding the mechanisms of transition to androgen independence and tumor progression in prostate cancer is critical to finding new ways to treat aged patients that are ineligible for conventional chemotherapy. A large number of different molecular mechanisms might be responsible for the transition to androgen-independence. Many of these involve the androgen receptor (AR) and its signalling pathways, but they might also include genetic changes that affect several genes, which results in the activation of oncogenes or the inactivation of tumor suppressor genes. Here, we discuss the most recent and relevant findings on androgen resistance in prostate cancer in order provide a comprehensive interpretation of the clinical behaviour of tumors at molecular levels.