Clinical trials testing Janus kinase-1 (JAK1) inhibitors in cancers are under way. Whether the JAK1 mRNA levels in breast tumors correlates with outcome has not been evaluated. JAK1 expression was analyzed via the Oncomine database and Tumor IMmune Estimation Resource site. Tumor tissues from 57 breast cancer patients were used for qRT-PCR and immune infiltration assessment. JAK1 expression was significantly lower in breast invasive carcinoma compared with adjacent normal tissues. Public databases (Kaplan-Meier plotter and PrognoScan) showed that low JAK1 expression was associated with poorer survival. Data from The Cancer Genome Atlas (TCGA) showed that high JAK1 expression was associated with increased survival in both TNM I-II and TNM III-IV patients. JAK1 was inversely correlated with tumor size status, lymph node status, and TNM of breast cancer patients. JAK1 levels were correlated with the T cell transcript-enriched LYM metagene signature and was significantly lower in the low tumor infiltrating lymphocytes (TILs) group. JAK1 expression levels had significant positive correlations with infiltrating levels of CD8+ T cells, CD4+ T cells, macrophages, neutrophils, and dendritic cells in breast cancer and not with other B cells. In conclusion, JAK1 mRNA levels were correlated with prognosis and immune infiltrating levels in breast cancer.

PARPBP (PARP1 binding protein) is an important suppressor of homologous recombination during DNA repair, but the expression and function of PARPBP in breast cancer remain unclear. PARPBP expression was analyzed in breast cancer patient samples and public datasets for its correlation with clinical outcome. The function of PARPBP in breast cancer cell proliferation and anthracycline treatment response were studied both in vitro and in vivo. PARPBP was upregulated significantly at both mRNA and protein levels in breast cancer tissues compared with normal breast tissues. PARPBP high expression group had poorer overall survival (OS) than the PARPBP low expression group. Knockdown of PARPBP suppressed breast cancer cell proliferation and colony formation while overexpression of PARPBP did the opposite. We found that transcription factor forkhead box M1 (FOXM1) could activate PARPBP expression by directly binding to the promoter of PARPBP. In addition, high expression of PARPBP related with anthracycline resistance in breast cancer. Depletion of PARPBP increased breast cancer cell apoptosis and DNA damage caused by epirubicin. Moreover, tumor xenograft experiments further demonstrated that PARPBP was involved in breast cancer anthracycline resistance. Taken together, our results highlight that PARPBP is a prognostic marker and confers anthracycline resistance on breast cancer.

Purpose: Somatic alteration of phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA) is a crucial therapeutic target in breast cancer (BC) and PI3Kα-specific inhibitor Alpelisib has been used in clinics. This study investigates the PIK3CA alterations in Chinese and Caucasians BC patients for the purpose of selecting anti-PI3K therapy. Methods: The molecular profile of the PIK3CA gene was analyzed in 412 Chinese patients with untreated invasive BC using a 540 gene next-generation sequencing panel. The results were compared with data of the Caucasian BC patients in The Cancer Genome Atlas (TCGA-white). Results: PIK3CA alterations were frequently found in BC of estrogen receptor (ER) positive (49.3%, p = 0.024), low ki67 proliferation index (58.3%, p = 0.007) and low pathological grade (grade I/II/III 80%, 53.4%, 35.9%, p < 0.001). Compared to TCGA-white, Chinese BC patients had a higher alteration frequency (45.6% vs. 34.7%, p < 0.001) with larger proportion of p.H1047R mutation among three common mutation sites (p.E545K, p.E542K and p.H1047R) (66.1% vs. 43.7%, p = 0.01). Across four molecular subtypes, ER + /human epidermal growth factor receptor 2 positive (HER2 +) tumors harbored the most PIK3CA alterations (51.6%), while ER-/HER2- harbored the least alteration (30.0%) but the most copy number amplification (19.05%). Conclusion: PIK3CA alterations prevail in Chinese BC patients and have different molecular features compared to that of Caucasians. The results provide precise annotations of PIK3CA genomic alterations of Chinese in the context of application of PIK3CA inhibitor.