JAK2 expression is correlated with the molecular and clinical features of breast cancer as a favorable prognostic factor

• We characterize the role of JAK2 at transcriptome level and its relationship with the clinical outcome of breast cancer. • JAK2 was correlated with American Joint Committee on Cancer (AJCC) stage and tumor malignancies of breast cancer. • We highlight the association between JAK2 and immune modulators in pan-cancer. • Higher expression of JAK2 was an independent indicator of favorable prognosis in breast cancer patients. • The expression of JAK2 is tightly related to the pathology and molecular pathology of breast cancer, and synergistic with other checkpoint members. Janus kinases are a family of non-receptor tyrosine kinases involved in autoimmune diseases and malignancies. In breast cancer, the immune related role of JAK2 remains unclear. We aimed to investigate its role at transcriptome level and its relationship with the clinical outcome of breast cancer. This study enrolled a total of 2994 breast cancer samples with transcriptome data, including 1090 samples from The Cancer Genome Atlas (TCGA) and 1904 from the Molecular Taxonomy of Breast Cancer International Consortium (METABRIC). JAK2 expression was significantly upregulated in both PR positive group (P < 0.01) and HER2 negative group (P < 0.01), and was correlated with American Joint Committee on Cancer (AJCC) stage and tumor malignancies of breast cancer. Functional enrichment analysis revealed that genes correlated with JAK2 were mainly involved in essential functions associated with immune response. Intriguingly, we investigated the association between JAK2 and immune modulators in pan-cancer, JAK2 expression was positively correlated with most of these immune modulators. In clinical aspect, higher expression of JAK2 was an independent indicator of favorable prognosis in breast cancer patients. The expression of JAK2 is tightly related to the pathology and molecular pathology of breast cancer, and synergistic with other checkpoint members thereby playing a specific role in regulating tumor immune microenvironment. To our knowledge, this is the largest and most comprehensive study characterizing the expression pattern of JAK2 and its special immune functions together with its prognostic values in breast cancer. These findings might shed novel sights for future research in cancer immunotherapy by targeting immune checkpoint molecules.