Most breast cancer patients are diagnosed at an advanced stage and have a poor prognosis. Recurrence of breast cancer and tumor metastasis are major obstacles to clinical treatment. It is imperative to explore new diagnostic and prognostic markers to improve the early diagnosis and outcomes of breast cancer. Recently, metastatic breast cancers transcriptional signature reveals Serum amyloid A1 (SAA1), a major acute-phase apolipoprotein reactant, is associated with breast cancer in expression and clinicopathological features. However, its regulatory function in breast cancer remains elusive, and its contribution to breast cancer metastasis remains uncertain. In this research, we downloaded the mRNA-sequencing data from the Gene Expression Omnibus (GEO) database (GSE102818, GSE28785, GSE134591) to comprehensively investigate the relationship between the expression of SAA1 and its impact on the metastatic implications, and further unveiled the connection of SAA1-mediated immunoregulation in breast cancer. We found that SAA1 is implicated in cell migration and regulation of immune cells by modulating cytokine-cytokine receptor interaction. Meanwhile, SAA1 released by tumor cells was demonstrated to contribute to tumor metastasis by inducing adipocytes reprogramming. Several current viewpoints propose that reprogramming of the molecular phenotype of immune cells is a major driver of cancer cell invasion and metastasis in tumor microenvironment. Based on previous studies and our findings, we hypothesized that SAA1-mediated cellular reprogramming may also apply to immune cells in the tumor microenvironment, and the interaction between tumor cells and immune cells through the release of SAA1 is relevant to the aggressiveness of breast cancer, which help patient decision-making for immunotherapy.
