Background:
Systemic immunotherapy is a promising therapy for cutaneous squamous cell carcinoma of the head and neck (cSCCHN) patients. However, many cSCCHN patients are affected by chronic immunosuppression (IS), which contraindicates the use of this highly effective therapy due to the inherent risks of systemic immunomodulation in this vulnerable population. Innovative immunotherapy approaches, such as local drug administration, could potentially offer lower risks for these IS patients. However, it is currently unknown whether the tumor microenvironment (TME) of IS cSCCHN individuals differs from immunocompetent (IC) ones and whether they would benefit from such therapy. Here we aimed to specify how the TME of IS cSCCHN patients differs from IC ones and what is the dynamics of TME through the tumorigenesis stages of cSCCHN IS patients.

Methods: To investigated the TME of IS and IC cSCCHN patients we build tissue microarrays (TMA) with primary tumor, keratinocytic intraepithelial neoplasia (KIN) and normal tissue of cSCCHN patients treated and MD Anderson and MOFFITT Cancer Centers. The TMAs were subjected to immunofluorescence staining using the Opal 7-color Multiplex Staining Kit and primary antibodies against cytokeratin, CD68, CD8, CD4, CD20, PD-L1, Lag3 and FoxP3. The stained slides were scanned in a Vectra Polaris Multispectral scanner, and the images were annotated with the Phenochart software and analyzed with the Akoya inForm software. Cell counts obtained for each cell phenotype were normalized by the tissue area according to their distribution along the tumor parenchyma and stroma.

Results: This study revealed a statistically significant lower density of CD68+ cells within the tumor (CK+) and stroma (CK-) of the IS patients when compared to the IC patients. In addition, CD68+PDL+ was found to have a higher density within the IS tumor when compared to the stroma. A statistically significant increase in CD68+PD-L1 was seen in the IS population with progression from KIN to invasive SCC. This study identified a strong correlation between stromal and tumoral immune cells within IS cohort which was not seen within the IC cohort. Stroma was not found to mirror tumoral compartments. Overall, analyzing the etiology of immunosuppression revealed lower amounts of CD8+/LAG3+ T-cells in lymphoma and leukemia patients. Within the organ transplantation population included within this study, a broad reduction of effector T cells was identified. Patients with IS had poorer clinical outcomes when compared to their matched controls. The number of CD68+ and CD8+LAG3+ in the tumor microenvironment were found to be predictors of disease specific survival and disease free survival.

Conclusions: This study surprisingly found that the most significant difference in the development of squamous cell carcinoma between immunosuppressed and immunocompetent hosts is a reduced innate immune response.