Multiplex Immunofluorescence Captures Progressive Immune Exhaustion with Advancing Penile Squamous Cell Cancer Stage

Simple Summary Penile cancer is a rare and aggressive disease. Current treatment options when the cancer is locally advanced are suboptimal and potentially mutilating. Insight into the immune dysregulation necessary for the emergence of penile cancer could suggest innovative ways to manipulate the immune system which have already demonstrated efficacy in other, more common malignancies. In this paper, we use multiplex immunofluorescence, a novel technology, to investigate the immune microenvironment of penile cancer for the first time. We describe a pattern of immune exhaustion as cancer becomes more advanced and identify tumor-associated macrophages as a potential key player in regulating this process.Abstract Penile squamous cell carcinoma (PSCC) is a rare and deadly malignancy. Therapeutic advances have been stifled by a poor understanding of disease biology. Specifically, the immune microenvironment is an underexplored component in PSCC and the activity of immune checkpoint inhibitors observed in a subset of patients suggests immune escape may play an important role in tumorigenesis. Herein, we explored for the first time the immune microenvironment of 57 men with PSCC and how it varies with the presence of human papillomavirus (HPV) infection and across tumor stages using multiplex immunofluorescence of key immune cell markers. We observed an increase in the density of immune effector cells in node-negative tumors and a progressive rise in inhibitory immune players such as type 2 macrophages and upregulation of the PD-L1 checkpoint in men with N1 and N2-3 disease. There were no differences in immune cell densities with HPV status.