The ZNF354C–TBC1D24 Axis Promotes Triple-Negative Breast Cancer Progression via PI3K/Akt-Dependent G1/S Activation

Background: Triple-negative breast cancer (TNBC) is an aggressive subtype characterized by rapid proliferation and limited targeted therapies. While aberrant activation of proliferative signaling pathways is common in TNBC, the upstream regulators sustaining these oncogenic circuits remain poorly defined. TBC1D24, a Tre-2/Bub2/Cdc16 (TBC) domain–containing protein involved in vesicular trafficking, has not been previously characterized in breast cancer. Methods: Transcriptomic and correlation analyses were performed using TCGA and CCLE datasets. Gene Set Enrichment Analysis (GSEA) and KEGG pathway enrichment were applied to identify associated biological processes. Functional roles of TBC1D24 were assessed using siRNA-mediated knockdown and overexpression in breast cancer cell lines, followed by proliferation, colony formation, and xenograft tumor assays. Mechanistic investigations included western blotting, luciferase reporter assays, ChIP–qPCR, and immunohistochemistry to evaluate downstream signaling and transcriptional regulation. Results: TBC1D24 expression was significantly associated with cell cycle–related signatures, particularly G1/S transition pathways. TBC1D24 positively correlated with CDK2, CDK4, CDK6, CCND1, and MYC in the TCGA cohort. Functional depletion of TBC1D24 suppressed proliferation and tumor growth, reduced CDK4/6 expression, increased P21 and P27 levels, and promoted apoptosis. Mechanistically, TBC1D24 activated the PI3K–Akt signaling pathway, enhancing phosphorylation of PI3K, Akt, and GSK3β and upregulating c-Myc and Cyclin D1. Upstream analyses identified ZNF354C as a direct transcriptional activator of TBC1D24, with promoter binding confirmed by ChIP–qPCR and luciferase assays. Conclusion: The ZNF354C–TBC1D24–PI3K/Akt axis promotes G1/S progression and breast cancer growth, representing a potential therapeutic target in aggressive TNBC.