High GINS2 transcript level predicts poor prognosis and correlates with high histological grade and endocrine therapy resistance through mammary cancer stem cells in breast cancer patients.

GINS2, a subunit of the GINS complex, is overexpressed in lung adenocarcinoma and metastatic breast tumor; however, its prognostic power and possible molecular mechanisms in breast cancer (BC) remain unclear. In this study, we aimed to explore the function of GINS2 in BC. The association between GINS2 transcript level and the clinical outcome of BC patients were estimated using Kaplan-Meier plots, multivariate cox regression analysis, forest plots, and receiver operating characteristics curves. Gene set enrichment analysis (GSEA) was performed to explore the mechanisms underlying the effects of the GINS2 transcript. High GINS2 transcript level was correlated with poor relapse free survival (log-rank P ≤ 0.001 in six cohorts; forest plot: total n = 1,420, total RR = 1.72, 95% CI 1.45-2.03; multivariate cox regression analysis: n = 906, HR 2.36, 95% CI 1.88-2.97), and distant metastasis free survival (log-rank P < 0.01 in 3 cohorts; forest plot: total n = 691, total RR 1.91, 95% CI 1.36-2.67; multivariate cox regression analysis: n = 442, HR 2.43, 95% CI 1.70-3.47). BC patients with higher GINS2 transcript levels showed poorer tamoxifen efficacy in a dose-dependent manner. GINS2 expression was significantly downregulated under mutated p53-depleted condition in MDA-468 and MDA-MB-231 cells, upregulated in mammary cancer stem cells (MaCSCs) (P = 0.003), and correlated with upregulated genes in mammary stem cells (GSEA: P < 0.01). Our study, for the first time, demonstrates that GINS2 is an independent prognostic marker and is associated with lung metastasis, histological grade, and endocrine therapy resistance in BC patients, which may attribute to mutant p53 and MaCSCs.