Superoxide induced inhibition of death receptor signaling is mediated via induced expression of apoptosis inhibitory protein cFLIP.

The death inhibitory proteins, cFLIP and Bcl-2, canonically act at different steps to regulate receptor-mediated apoptosis in cancer cells. Here we report that pharmacological or genetic means to effect an increase in intracellular superoxide result in cFLIP upregulation. Interestingly, Bcl-2 overexpression is associated with a concomitant increase in cFLIP, and reducing superoxide sensitizes Bcl-2 overexpressing cancer cells to receptor-mediated apoptosis via downregulation of cFLIP. Moreover, inhibiting glycolytic flux overcomes apoptosis resistance by superoxide-dependent downregulation of cFLIP. Superoxide-induced upregulation of cFLIP is a function of enhanced transcription, as evidenced by increases in cFLIP promoter activity and mRNA abundance. The positive effect of superoxide on cFLIP is mediated through its reaction with nitric oxide to generate peroxynitrite. Corroborating these findings in cell lines, subjecting primary cells derived from lymphoma patients to glucose deprivation ex vivo, as a means to decrease superoxide, not only reduced cFLIP expression but also significantly enhanced death receptor sensitivity. Based on this novel mechanistic insight into the redox regulation of cancer cell fate, modulation of intracellular superoxide could have potential therapeutic implications in cancers in which these two death inhibitory proteins present a therapeutic challenge.

Simvastatin-induced breast cancer cell death and deactivation of PI3K/Akt and MAPK/ERK signalling are reversed by metabolic products of the mevalonate pathway.

Statins purportedly exert anti-tumoral effects on breast cancer. However, the biologic mechanisms for these actions are not fully elucidated. The aims of this study were 1) to explore the effects of simvastatin on apoptosis, proliferation as well as PI3K/Akt/mTOR and MAPK/ERK pathway in a window-of-opportunity breast cancer trial; 2) to further confirm findings from the clinical trial by functional studies; 3) to explore the regulatory role of mevalonate pathway on the anti-tumoral effects of simvastatin. In clinical samples, simvastatin led to increase in cleaved caspase-3 (p = 0.002) and decreased trend for Ki67 (p = 0.245). Simvastatin markedly suppressed PI3K/Akt/mTOR signalling by activating PTEN (p = 0.005) and by dephosphorylating Akt (p = 0.002) and S6RP (p = 0.033); it also inhibited MAPK/ERK pathway by dephosphorylating c-Raf (p = 0.018) and ERK1/2 (p = 0.002). In ER-positive (MCF-7, T47D) and ER-negative (MDA-MB-231, BT-549) breast cancer cells, simvastatin treatment consistently induced apoptosis and inhibited proliferation by deregulating caspase cascades and cell cycle proteins in a dose dependent manner. Concordantly, simvastatin strongly suppressed PI3K/Akt/mTOR pathway by enhancing PTEN expression and by further sequentially dephosphorylating downstream cascades including Akt, mTOR, p70S6K, S6RP and 4E-BP1. Furthermore, simvastatin significantly inhibited MAPK/ERK pathway by dephosphorylating sequential cascades such as c-Raf, MEK1/2 and ERK1/2. These simvastatin anti-tumoral effects were reversed by metabolic products of the mevalonate pathway, including mevalonate, farnesyl pyrophosphate and geranylgeranyl pyrophosphate. These findings shed light on the biological and potential anti-tumoral effects of simvastatin in breast cancer.

Evidence for disease control with erlotinib after gefitinib failure in typical gefitinib-sensitive Asian patients with non-small cell lung cancer.

INTRODUCTION: The epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) gefitinib and erlotinib are gaining an increasing role in the management of advanced non-small cell lung cancer (NSCLC). There is mounting interest in the benefit of administering a second TKI after failure of the first TKI, especially in Asian patients, in whom they are expected to be more efficacious. METHODS: We did a retrospective analysis of patients receiving both gefitinib and erlotinib in our institution during a 2-year period. Patients were to have received the second TKI after progressive disease on the first TKI. EGFR gene mutation analysis was done on patient tumor samples. RESULTS: Fourteen patients were included in the analysis, all of whom received erlotinib after progression on gefitinib. Chinese race, females, never-smokers, and adenocarcinoma subtype were predominant in their respective categories. Disease control rate was 64.3% (9 of 14) for gefitinib. Disease control rate for erlotinib administered after progression on gefitinib was 35.7% (5 of 14). All patients who achieved disease control with erlotinib after progression on gefitinib were never-smokers with adenocarcinoma subtype, who had prior disease control on gefitinib. Presence of EGFR mutations predicted for disease control with gefitinib, and for disease control with erlotinib after gefitinib failure. CONCLUSION: A significant proportion of typical gefitinib-sensitive Asian NSCLC patients can have disease control with erlotinib after gefitinib failure. The role of subsequent administration of a second EGFR TKI after failure of the first TKI in advanced NSCLC should be further pursued.