Cystine/cysteine metabolism regulates the progression and response to treatment of triple‑negative breast cancer (Review).

Breast cancer is the most prevalent neoplasm affecting women globally, of which a notable proportion of cases are triple-negative breast cancer (TNBC). However, there are limited curative treatment options for patients with TNBC, despite advancements in the field. Amino acids and amino acid transporters serve vital roles in the regulation of tumor metabolism. Notably, cystine and cysteine can interconvert via a redox reaction, with cysteine exerting control on cell survival and growth and exogenous cystine serving a crucial role in the proliferation of numerous types of cancers. Breast cancer has been reported to disrupt the cystine/cysteine metabolism pathway, as cystine and cysteine transporters affect the development and growth of tumors. The present review aims to provide a comprehensive overview of the metabolic pathways involving cystine and cysteine in normal and TNBC cells. Furthermore, the roles of cystine and cysteine transporters in TNBC progression and metastasis and their potential as therapeutic targets for treatment of TNBC are evaluated.