Monocytes and Macrophage-derived mediators influence the behavior of squamous cell carcinoma cell lines

Immune cells play diverse roles in cancer development. Myeloid cells are key drivers of tumor-escape mechanisms as they suppress immune responses, facilitate metastasis, and contribute to therapy resistance. In particular, macrophages can be polarized into an inflammatory M1 (anti-tumor) or anti-inflammatory M2 (pro-tumor) phenotype. M2 macrophages are associated with tumor progression, as they secrete factors that promote tumor angiogenesis, suppress T-cell activity, and correlate with poor clinical outcomes in squamous cell carcinoma (SCC). Given this context, this study aims to demonstrate the biological effects of monocytes and both M1 and M2 macrophages in squamous cell carcinoma. Our data indicate higher CD163 immunoreactivity in biopsies from SCC patients. Furthermore, we found that a conditioned medium (CM) containing bioactive compound generated by M2 macrophages enhances the proliferation and invasion of the SCC-25 cell line in vitro. Surprisingly, CM derived from blood CD14+ monocytes increased SCC-25 proliferation at the same rate of M2 macrophages-CM. M1 macrophages conditioned medium significantly enhanced the motility and decreased proliferation in Detroit 562 cells. The analysis of tumor-associated transcripts showed that both M1 and M2 conditioned medium induced high levels of EPCAM mRNA and significantly decreased the expression of MYC, an epithelial-to-mesenchymal transition marker, in SCC cell lines. Detroit cells exposed to conditioned medium from monocytes and macrophage also showed elevated SOX2 mRNA levels. The findings suggest that monocytes and macrophage mediators exert distinct biological effects on SCC cell lines.