Nitroprusside induces melanoma ferroptosis with serum supplementation and prolongs survival under serum depletion or hypoxia.

Background: When proliferating tumor cells expand to areas distant from vascular sites, poor diffusion of oxygen and nutrients occur, generating a restrictive hypoxic gradient in which susceptible tumor cells die. The heterogeneous population surviving hypoxia and metabolic starvation include de-differentiated cancer stem cells (CSC), capable of self-renewing tumor-initiating cells (TICs), or those that divide asymmetrically to produce non-tumor-initiating differentiated (NTI-D) cell progeny. Under such restrictive conditions, both populations slowly proliferate, entering quiescence or senescence, when exiting from cell cycle progression.

DNA Damage Induces a Secretory Program in the Quiescent TME that Fosters Adverse Cancer Phenotypes.

Carcinomas develop in complex environments that include a diverse spectrum of cell types that influence tumor cell behavior. These microenvironments represent dynamic systems that contribute to pathologic processes. Damage to DNA is a notable inducer of both transient and permanent alterations in cellular phenotypes.

DNA damage induces GDNF secretion in the tumor microenvironment with paracrine effects promoting prostate cancer treatment resistance.

Though metastatic cancers often initially respond to genotoxic therapeutics, acquired resistance is common. In addition to cytotoxic effects on tumor cells, DNA damaging agents such as ionizing radiation and chemotherapy induce injury in benign cells of the tumor microenvironment resulting in the production of paracrine-acting factors capable of promoting tumor resistance phenotypes. In studies designed to characterize the responses of prostate and bone stromal cells to genotoxic stress, we found that transcripts encoding glial cell line-derived neurotrophic factor (GDNF) increased several fold following exposures to cytotoxic agents including radiation, the topoisomerase inhibitor mitoxantrone and the microtubule poison docetaxel.

H(2)O(2) preferentially synergizes with nitroprusside to induce apoptosis associated with superoxide dismutase dysregulation in human melanoma irrespective of p53 status: Antagonism by o-phenanthroline.

The pro-oxidant hydrogen peroxide (H(2)O(2)) is converted to a reactive oxygen species by transition metals like iron. Since mutations in the p53 tumor suppressor gene contribute to drug resistance, we used genetically-matched human C8161 melanoma harbouring wt or DN-R175H mutant p53, to investigate the influence of p53 status on the potentiation of H(2)O(2) toxicity by: (a) intact sodium nitroprusside or nitroferricyanide (SNP), (b) its light-exhausted NO-depleted form (lex-SNP), (c) potassium ferricyanide, or (d) ferric ammonium sulphate. Whereas single treatments with SNP or H(2)O(2) were partly cytotoxic, preferentially potentiation of H(2)O(2) toxicity was evidenced with intact or lex-SNP.

ERK activation increases nitroprusside induced apoptosis in human melanoma cells irrespective of p53 status: role of superoxide dismutases.

Constitutive ERK activation, superoxide dismutases (SOD) and p53 mutations are implicated in modulating tumor apoptotic response. We now investigated whether human melanoma survival in response to sodium nitroprusside (SNP) is modulated by: (a) stable introduction of a DN-mutant p53; (b) pharmacologically inhibiting ERK activation with UO126; (c) addition of exogenous SOD. Nitroprusside releases nitric oxide (NO) when intact, or acts in a NO-independent manner via iron and residual cyanide after light exposure (lex-SNP).

Hydrogen peroxide increases a 55-kDa tyrosinase concomitantly with induction of p53-dependent p21 waf1 expression and a greater Bax/Bcl-2 ratio in pigmented melanoma.

Differentiated melanocytic cells produce melanin, through several redox reactions including tyrosinase-catalyzed DOPA oxidation to DOPA quinone. We now developed a method based on DOPA oxidase in-gel detection and Sypro Ruby fluorometric normalization to investigate induction of specific DOPA oxidase isoforms in response to hydrogen peroxide-mediated stress, and to ask whether this is associated with p53-dependent adaptive responses. This report shows that hydrogen peroxide leads to comparable induction of 60 and 55 kDa DOPA oxidases in poorly pigmented B16 melanoma, in contrast to sole induction of a major 55 kDa DOPA oxidase in their highly pigmented counterparts.