Chronic nitric oxide exposure induces prostate cell carcinogenesis, involving genetic instability and a pro-tumorigenic secretory phenotype.

Prostate cancer is a leading cause of cancer death in men. Inflammation and overexpression of inducible nitric oxide synthase (NOS2) have been implicated in prostate carcinogenesis. We aimed to explore the hypothesis that nitric oxide NO exerts pro-tumorigenic effects on prostate cells at physiologically relevant levels contributing to carcinogenesis. We investigated the impact of acute exposure of normal immortalised prostate cells (RWPE-1) to NO on cell proliferation and activation of DNA damage repair pathways. Furthermore we investigated the long term effects of chronic NO exposure on RWPE-1 cell migration and invasion potential and hallmarks of transformation. Our results demonstrate that NO induces DNA damage as indicated by γH2AX foci and p53 activation resulting in a G1/S phase block and activation of 53BP1 DNA damage repair protein. Long term adaption to NO results in increased migration and invasion potential, acquisition of anchorage independent growth and increased resistance to chemotherapy. This was recapitulated in PC3 and DU145 prostate cancer cells which upon chronic exposure to NO displayed increased cell migration, colony formation and increased resistance to chemotherapeutics. These findings indicate that NO may play a key role in the development of prostate cancer and the acquisition of an aggressive metastatic phenotype.

Secreted factors from metastatic prostate cancer cells stimulate mesenchymal stem cell transition to a pro-tumourigenic 'activated' state that enhances prostate cancer cell migration.

Mesenchymal stem cells (MSCs) are a heterogeneous population of multipotent cells that are capable of differentiating into osteocytes, chondrocytes and adipocytes. Recently, MSCs have been found to home to the tumour site and engraft in the tumour stroma. However, it is not yet known whether they have a tumour promoting or suppressive function. We investigated the interaction between prostate cancer cell lines 22Rv1, DU145 and PC3, and bone marrow-derived MSCs. MSCs were 'educated' for extended periods in prostate cancer cell conditioned media and PC3-educated MSCs were found to be the most responsive with a secretory profile rich in pro-inflammatory cytokines. PC3-educated MSCs secreted increased osteopontin (OPN), interleukin-8 (IL-8) and fibroblast growth factor-2 (FGF-2) and decreased soluble fms-like tyrosine kinase-1 (sFlt-1) compared to untreated MSCs. PC3-educated MSCs showed a reduced migration and proliferation capacity that was dependent on exposure to PC3-conditioned medium. Vimentin and α-smooth muscle actin (αSMA) expression was decreased in PC3-educated MSCs compared to untreated MSCs. PC3 and DU145 education of healthy donor and prostate cancer patient-derived MSCs led to a reduced proportion of FAP+ αSMA+ cells contrary to characteristics commonly associated with cancer associated fibroblasts (CAFs). The migration of PC3 cells was increased toward both PC3-educated and DU145-educated MSCs compared to untreated MSCs, while DU145 migration was only enhanced toward patient-derived MSCs. In summary, MSCs developed an altered phenotype in response to prostate cancer conditioned medium which resulted in increased secretion of pro-inflammatory cytokines, modified functional activity and the chemoattraction of prostate cancer cells.

Inflammation and Nitrosative Stress Effects in Ovarian and Prostate Pathology and Carcinogenesis.

SIGNIFICANCE: Prostate and ovarian cancers are major contributors to cancer-related deaths worldwide. Recently, inflammation and nitrosative stress have been implicated in carcinogenesis, with the overexpression of NOS2 and concomitant release of nitric oxide (NO) associated with cancer initiation and progression. Recent Advances: An increasing body of evidence indicates an association between NOS2 expression and aggressive ovarian cancer. Research also indicates a role for NO in prostate disease pathology and prostate cancer. A therapeutic role for NOS2 inhibition and/or NO drugs exists for the treatment of both ovarian and prostate tumors. CRITICAL ISSUES: Herein, we review the key molecular effects associated with NOS2 in ovarian and prostate cancer. NOS2 increases angiogenesis and tumor proliferation and correlates with aggressive type II ovarian tumors. NOS2 expressing tumors are sensitive to cisplatin chemotherapy, and NO may be used to sensitize cisplatin-resistant tumors to chemotherapy. NOS2 is highly expressed in prostate tumors compared to non-neoplastic prostate pathologies. NO may play a role in the development of androgen-independent prostate cancer via s-nitrosylation of the androgen receptor. Moreover, NOS2 inhibitors and NO donor drugs show therapeutic potential in ovarian and prostate cancer as single agents or dual drugs, by either inhibiting the effects of NOS2 or increasing NO levels to induce cytotoxic effects. FUTURE DIRECTIONS: NOS2 and NO present new targets for the treatment of ovarian and prostate tumors. Furthermore, understanding NO-related tumor biology in these cancers presents a new means for improved patient stratification to the appropriate treatment regimen. Antioxid. Redox Signal. 26, 1078-1090.

Sensitivity Profiles of Human Prostate Cancer Cell Lines to an 80 Kinase Inhibitor Panel.

BACKGROUND: Taxanes and anti-androgen therapies are routinely used for the treatment of metastatic prostate cancer, however the majority of patients eventually develop resistance. MATERIALS AND METHODS: Eighty kinase inhibitors were screened regarding their ability to inhibit cell viability in CWR22, 22Rv1, PC-3 and DU145 prostate cancer cells using automated toxicity assays. Four kinase inhibitors were selected for further investigation. RESULTS: No significant difference in sensitivity patterns was found between the androgen receptor wild-type CWR22 and its androgen receptor mutant variant 22Rv1, indicating that androgen receptor mutation did not impact on kinase inhibitor sensitivity in this model. Metastatic PC-3 and DU145 prostate cancer cell lines were less sensitive to kinase inhibitors than the non-metastatic CWR22 and 22Rv1. All four cell lines responded to GSK-3 inhibitor BIO, and MEK inhibitor PD198306. DU145 cells were resistant to p75NTR/TrkA and CHK4 inhibitors, RO-082750 and Ryuvidine. CONCLUSION: Kinase inhibition may be an appropriate strategy for the treatment of prostate cancer.

The yin and yang of nitric oxide in cancer progression.

Nitric oxide (NO) is a short-lived, pleiotropic molecule that affects numerous critical functions in the body. Presently, there are markedly conflicting findings in the literature regarding NO and its role in carcinogenesis and tumor progression. NO has been shown to have dichotomous effects on cellular proliferation, apoptosis, migration, invasion, angiogenesis and many other important processes in cancer biology. It has been shown to be both pro- and antitumorigenic, depending on the concentration and the tumor microenvironment in question. NO is generated by three isoforms of NO synthase (NOS) that are widely expressed and sometimes upregulated in human tumors. Due to its vast array of physiological functions, it presents a huge challenge to researchers to discover its true potential in cancer biology and consequently, its use in anticancer therapies. In this study, we review the current knowledge in this area, with an emphasis placed on NO modulation as an anticancer therapy, focusing on NO-donating drugs and NOS inhibitors.