Cav-1 immunoreactivity in lung carcinoma is histotype-dependent and acquired de novo in brain metastases, suggesting a site-specific phenotypic shift in secondary lesions.
NAD is an essential coenzyme involved in numerous metabolic pathways. Its principal role is in redox reactions, and as such it is not heavily "consumed" by cells. Yet a number of signaling pathways that bring about its consumption have recently emerged. This has brought about the hypothesis that the enzymes that lead to its biosynthesis may be targets for anticancer therapy. In particular, inhibition of the enzyme nicotinamide phosphoribosyl transferase has been shown to be an effective treatment in a number of preclinical studies, and two lead molecules [N-[4-(1-benzoyl-4-piperidinyl)butyl]-3-(3-pyridinyl)-2E-propenamide (FK866) and (E)-1-[6-(4-chlorophenoxy)hexyl]-2-cyano-3-(pyridin-4-yl)guanidine (CHS 828)] have now entered preclinical trials. Yet, the full potential of these drugs is still unclear. In the present study we have investigated the role of FK866 in neuroblastoma cell lines. We now confirm that FK866 alone in neuroblastoma cells induces autophagy, and its effects are potentiated by chloroquine and antagonized by 3-methyladenine or by down-regulating autophagy-related protein 7. Autophagy, in this model, seems to be crucial for FK866-induced cell death. On the other hand, a striking potentiation of the effects of cisplatin and etoposide is given by cotreatment of cells with ineffective concentrations of FK866 (1 nM). The effect of etoposide on DNA damage is potentiated by FK866 treatment, whereas the effect of FK866 on cytosolic NAD depletion is potentiated by etoposide. Even more strikingly, cotreatment with etoposide/cisplatin and FK866 unmasks an effect on mitochondrial NAD depletion.
Our model aimed at studying the main nongenetic risk factor for ovarian cancer, providing an alternative interpretation for the role of menstruation in increasing risk of this pathology. This in vitro model mimics several features of the precursor lesions and opens new scenarios for further investigations regarding the correlation between damages produced by repeated retrograde menstruation carcinogenic stimuli.
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