Loss of the cystine/glutamate antiporter in melanoma abrogates tumor metastasis and markedly increases survival rates of mice

The cystine/glutamate antiporter, system x_c ^- , is essential for the efficient uptake of cystine into cells. Interest in the mechanisms of system x_c ^- function soared with the recognition that system x_c ^- presents the most upstream node of ferroptosis, a recently described form of regulated necrosis relevant for degenerative diseases and cancer. Since targeting system x_c ^- hold the great potential to efficiently combat tumor growth and metastasis of certain tumors, we disrupted the substrate-specific subunit of system x_c ^- , xCT (SLC7A11) in the highly metastatic mouse B16F10 melanoma cell line and assessed the impact on tumor growth and metastasis. Subcutaneous injection of tumor cells into the syngeneic B16F10 mouse melanoma model uncovered a marked decrease in the tumor-forming ability and growth of KO cells compared to control cell lines. Strikingly, the metastatic potential of KO cells was markedly reduced as shown in several in vivo models of experimental and spontaneous metastasis. Accordingly, survival rates of KO tumor-bearing mice were significantly prolonged in contrast to those transplanted with control cells. Analyzing the in vitro ability of KO and control B16F10 cells in terms of endothelial cell adhesion and spheroid formation revealed that xCT expression indeed plays an important role during metastasis. Hence, system x_c ^- emerges to be essential for tumor metastasis in mice, thus qualifying as a highly attractive anticancer drug target, particularly in light of its dispensable role for normal life in mice.

Keywords: melanoma; metastasis; system xc−; tumor growth.