TIPE2 regulates tumor-associated macrophages in skin squamous cell carcinoma.

Tumor-associated macrophages (TAMs) play an essential role in the immunology, growth, invasion, and metastases of skin squamous cell carcinoma (SCC). However, the molecular mechanisms underlying the activation and regulation of TAMs by SCC are not completely understood. Here, in a Transwell co-culture system, we found that SCC cells induced polarization of macrophages to a M2 phenotype, evident by expression of surface markers CD163, CD206, and CD301, as well as reduction of cellular iNOS levels and augmentation of cellular arginase levels. Moreover, tumor necrosis factor (TNF)-alpha-induced protein 8-like 2 (TIPE2) was induced in macrophages by co-culturing with SCC cells. Depletion of TIPE2 in macrophages abolished the effects of co-cultured SCC cells on phenotypic modification of macrophages. Furthermore, patients with SCC were divided into two groups based on TIPE2 levels in TAMs at the time of tumor resection. We found that patients with high-TIPE2 TAMs had an overall poor 5-year survival. Together, our data suggest a previously unappreciated role of TIPE2 in the crosstalk between skin SCC and TAMs and highlight TIPE2 as a promising novel target for skin SCC treatment.