Identification of SLC7A5 and transferrin as key ferroptosis modulators in triple‑negative breast cancer

Triple‑negative breast cancer (TNBC) lacks effective targeted therapies; however, ferroptosis represents a promising therapeutic vulnerability. The present study aimed to identify and functionally characterize ferroptosis‑related genes that influence TNBC progression and prognosis. RNA‑sequencing data and clinical information for TNBC were obtained from The Cancer Genome Atlas and FerrDB V2 databases. Subsequently, differential expression analysis, Cox regression and functional enrichment analyses were performed. The core genes solute carrier family 7 member 5 (SLC7A5) and transferrin (TF) were selected and validated in TNBC clinical samples by western blot analysis and reverse transcription‑quantitative PCR in four paired tissues and 20 paired tissues, respectively. Functional assays (Cell Counting Kit‑8 and Transwell assays), and the detection of ferroptosis markers [including glutathione (GSH), malondialdehyde (MDA), reactive oxygen species (ROS)] and core ferroptosis proteins [GSH peroxidase 4 (GPX4), solute carrier family 7 member 11 (SLC7A11), TF receptor 1 (TFRC), ferritin heavy chain 1 (FTH1), acyl‑CoA synthetase long‑chain family member 4 (ACSL4) and 4‑hydroxy‑2‑nonenal (4‑HNE)] were conducted in both MCF‑7 [estrogen receptor (ER)‑positive] and MDA‑MB‑231 (TNBC) cells following SLC7A5 knockdown or TF overexpression. The involvement of ferroptosis was confirmed using the specific inhibitor ferrostatin‑1 (Fer‑1). A total of 93 ferroptosis‑associated differentially expressed genes were identified in TNBC. In addition, SLC7A5 and TF were established as independent prognostic factors. High SLC7A5 mRNA expression was associated with poor prognosis [hazard ratio (HR)=1.73; P<0.001 for overall survival (OS)] and advanced pathological stage, whereas high TF mRNA expression predicted favorable outcomes (HR=0.61; P=0.003 for OS) and showed notable diagnostic power (area under the curve=0.935). In both MCF‑7 and MDA‑MB‑231 cells, SLC7A5 knockdown and TF overexpression inhibited cell proliferation and migration while inducing ferroptosis, as evidenced by increased ROS/MDA, depleted GSH, decreased GPX4 and SLC7A11, increased TFRC and FTH1, and upregulated ACSL4/4‑HNE; notably, all of these effects were reversed by Fer‑1 treatment. In conclusion, the present study established SLC7A5 as a ferroptosis suppressor and oncogenic driver, and TF as a ferroptosis inducer and tumor suppressor in TNBC. This was validated in both ER‑positive and TNBC cell lines; therefore, the present findings provide novel mechanistic insights and identify both genes as promising diagnostic biomarkers and therapeutic targets for ferroptosis‑based TNBC therapy.