Tumor-associated macrophages in the cutaneous SCC microenvironment are heterogeneously activated.

Tumor-associated macrophages (TAMs) may have an important role in tumor immunity. We studied the activation state of TAMs in cutaneous SCC, the second most common human cancer. CD163 was identified as a more abundant, sensitive, and accurate marker of TAMs when compared with CD68.

Myeloid dendritic cells from human cutaneous squamous cell carcinoma are poor stimulators of T-cell proliferation.

To determine the phenotype and function of myeloid dendritic cells (DCs) from human cutaneous squamous-cell carcinoma (SCC), we studied their surface marker expression and allo-stimulatory potential ex vivo. There were abundant CD11c(+) myeloid DCs, as well as TNF and inducible nitric oxide synthase (iNOS)-producing DCs, in and around SCC tumor nests. Although myeloid DCs from SCC, adjacent non-tumor-bearing skin, and normal skin, were phenotypically similar by flow cytometry, and there was a pronounced genomic signature of mature DCs in SCC, they showed different T-cell stimulatory potential in an allogeneic mixed leukocyte reaction.