Cytotoxic T-cells (CTL) can mediate an anti-tumour response, but are 1) inhibited by regulatory T-cells (Tregs), 2) mislead by aberrant Human Leukocyte Antigen (HLA) expression on the tumour cells and 3) deactivated by Programmed Death Ligand 1 (PD-L1) on tumour cells or on tumour infiltrating macrophages (TIM). We aimed to gain insight in immunological factors in penile cancer, and their correlations with lymph node metastasis and disease specific survival.
Histological sections from a cohort of 213 penile cancer patients treated between 2000 and 2009 were used for immunohistochemical analysis. Human Papilloma Virus (HPV) status and different levels of HLA class I-expression were known from previous studies. Sections were stained for PD-L1, M2 macrophage-marker CD163, CTL-marker CD8, and Treg-marker FoxP3. PD-L1 was scored on TIM, tumour cells (percentage positive cells) and as tumour staining pattern (diffuse or predominantly at the tumour-stroma margin). Macrophages were scored as present/absent in tumour and stroma. The prognostic value of these parameters for lymph node metastasis (LN+ or LN-) and disease specific survival (DSS) was tested in univariable and multivariable regression models.
Upon univariable analysis, strong intratumoural CD163 expression, non-classical HLA upregulation and diffuse tumour PD-L1 positivity were predictive for LN+, while high numbers of CD8+ T-cells in the stroma was associated with LN-. Regarding survival, HPV-positivity was significantly associated with improved DSS. Partial downregulation of classical HLA and a diffuse PD-L1 positivity in the tumour, with worse DSS.
Multivariable analysis determined HPV as a predictor for better DSS but not for lymph node status. Strong CD163 expression and a diffuse PD-L1 positivity in the tumour were both associated with LN+ and worse DSS. Other predictors included high CD8+ numbers in the stroma, associated with LN-, and partial downregulation of classical HLA, associated with worse survival.
When multivariably tested against clinicopathological predictors for lymph node status (lymfangioinvasion, grade of differentiation) and DSS (grade of differentiation, tumour size and lymph node status), HPV status (better DSS) and a diffuse PD-L1 expression of the tumour (LN+ and worse DSS) were the only immune factors that remained significantly outcome correlated.
In penile cancer, various immune factors show correlations with lymph node status and ultimately, patient survival. These factors should be taken into account in future immunotherapy trials. The specific dissection of the tumour microenvironment characteristics will assist in patient tailored treatment.