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

Abstract

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. This may drive chemoresistance and tumor recurrence, since most anti-cancer treatments target rapidly proliferating cells.

PURPOSE:

Since persistent or additional stress may increase NTI-D cells conversion to TICs, we investigated whether nutrient depletion or hypoxia influence expression of tyrosinase, a crucial enzyme for melanin synthesis, and B16 melanoma survival, when exposed to iron-dependent cell death oxidative stress produced by the Fenton reaction, resembling ferroptosis.

RESULTS:

-a) proliferating B16 melanoma with 10% serum-supplementation (10%S) normoxically express hypoxia inducible factor 1α (HIF1α) but lose tyrosinase, in contrast to those transiently exposed to (SF) serum-free medium, in which both HIF1α and tyrosinase are co-expressed; b) in contrast to the resistance to SNP toxicity in (SF) cells with higher tyrosinase expression, those in (10%S) are killed by iron from nitroprusside/ferricyanide (SNP) irrespective of exogenous H2O2, in a reaction antagonized by the anti-oxidant and MEK inhibitor UO126; c) Moreover, under transient serum depletion, SNP cooperates with hypoxia (1.5% oxygen), prolonging B16 melanoma (SF) survival; d) the hypoxia mimetic CoCl2 inhibits proliferation-associated cyclin A, irrespective of SNP, in (10%S) cells or in transiently serum-depleted (SF) cells. However, only in the latter cells, CoCl2 but not SNP, induce loss of HIF1α and apoptosis-associated PARP cleavage; e) longer term adaptation to survive serum depletion, generates (SS) cells resistant to SNP toxicity, which aerobically co-express HIF1α and tyrosinase. In SS B16 melanoma, exogenous non-toxic 100 μM H2O2 super-induces the ratio of tyrosinase to HIF1α. However, co-treatment of SS-B16 cells with SNP plus exogenous H2O2, partly increases PARP cleavage by reciprocally decreasing tyrosinase expression.

SIGNIFICANCE:

- These results suggest that a phenotypic plasticity in response to depletion of nutrients and/or oxygen, helps decide whether melanoma cells undergo either death by ferroptosis, or resistance to it, when challenged by the same exogenous oxidative stress (iron ± H2O2).

• Authors: Manuel Rieber, Luis A Gomez-Sarosi, Mary Strasberg Rieber
• Journal: Biochemical and biophysical research communications (Biochem Biophys Res Commun) Vol. 525 Issue 3 Pg. 626-632 (05 07 2020) ISSN: 1090-2104 [Electronic] United States
• PMID: 32122653 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2020 Elsevier Inc. All rights reserved.

Chemical References

• Butadienes
• Culture Media, Serum-Free
• Cyclin A
• Hypoxia-Inducible Factor 1, alpha Subunit
• Nitriles
• Transferrin
• U 0126
• Nitroprusside
• Cobalt
• Hydrogen Peroxide
• Monophenol Monooxygenase
• Poly(ADP-ribose) Polymerases
• cobaltous chloride

Topics

• Animals
• Butadienes (pharmacology)
• Cell Hypoxia (drug effects)
• Cell Survival (drug effects)
• Cobalt (pharmacology)
• Culture Media, Serum-Free
• Cyclin A (metabolism)
• Ferroptosis (drug effects)
• Hydrogen Peroxide (pharmacology)
• Hypoxia-Inducible Factor 1, alpha Subunit (metabolism)
• Melanoma, Experimental (pathology)
• Mice
• Monophenol Monooxygenase (metabolism)
• Nitriles (pharmacology)
• Nitroprusside (pharmacology)
• Poly(ADP-ribose) Polymerases (metabolism)
• Serum (metabolism)
• Transferrin (deficiency, metabolism)