It is increasingly recognized that cancer progression induces systemic immune changes in the host. Alterations in number and function of immune cells have been identified in cancer patients’ peripheral blood and lymphoid organs. Recently, we found dysregulated cytokine signaling in peripheral blood T cells from breast cancer (BC) patients, even those with localized disease.
We used phosphoflow cytometry to determine the clinical significance of cytokine signaling responsiveness in peripheral blood monocytes from non-metastatic BC patients at diagnosis. We also examined the correlation between cytokine signaling in peripheral monocytes and the number of tumor-infiltrating macrophages in paired breast tumors.
Our results show that cytokine (IFNγ) signaling may also be dysregulated in peripheral blood monocytes at diagnosis, specifically in BC patients who later relapsed. Some patients exhibited concurrent cytokine signaling defects in monocytes and lymphocytes at diagnosis, which predict the risk of future relapse in two independent cohorts of BC patients. Moreover, IFNγ signaling negatively correlates with expression of CSF1R on monocytes, thus modulating their ability to infiltrate into tumors.
Our results demonstrate that tumor-induced systemic immune changes are evident in peripheral blood immune cells for both myeloid and lymphoid lineages, and point to cytokine signaling responsiveness as important biomarkers to evaluate the overall immune status of BC patients.