Multiplexed Immunofluorescent Characterization of T-Cell and Myeloid Cell Populations Reveals Histologic Subtype Differences Within the Immunosuppressive Landscape of Human Basal Cell Carcinoma.

BACKGROUND

Basal cell carcinomas (BCCs) are thought to reside within an immunosuppressed tumor microenvironment, but a detailed characterization of BCC-associated immune cells was lacking.

METHODS

Utilizing multiplex immunohistochemistry (IHC) (Vectra Polaris, Akoya Biosciences), we designed two staining panels, targeting either T cells (CD3, CD4, CD8, FoxP3, PD1) or myeloid cells (neutrophil elastase, CD68, CD163, HLADR, CD1c). Formalin-fixed paraffin-embedded (FFPE) BCC tumor specimens (n = 30) were analyzed using the panels. The majority of immune cells reside at the peritumoral margin; therefore, a boundary zone of 150 μm around tumor nests was used to capture them.

RESULTS

A CD8/T-reg ratio and M1/M2 macrophage ratio of < 0.5 was observed across all BCC specimens, confirming an overall immunosuppressive phenotype. Among different histologic subtypes, infiltrative BCC had significantly lower CD8 T cells (p = 0.038), T-regulatory cells (p = 0.039), and CD8/T-reg ratio (p = 0.048), as well as lower M1/M2 ratio (p = 0.034) compared to non-infiltrative BCC subtypes.

CONCLUSIONS

The association of infiltrative BCC with a more immunosuppressed microenvironment may contribute to more aggressive biological behavior. Overall, these data demonstrate a method to determine T cell and myeloid profiles in fixed FFPE skin tumor tissues that can identify subtle immune profile differences.