Investigating the Molecular Mechanisms of Transplantation-Associated Cutaneous Squamous Cell Carcinomas

Abstract

Cutaneous squamous cell carcinoma (cSCC), a keratinocyte carcinoma, is the most common malignancy in the US, with over 800,000 cases diagnosed each year. Notably, cSCC burdens solid organ transplant recipients and leads to significant morbidity upon disease progression. Chronic UV exposure is the most critical etiologic risk factor; however, age of patient, fair-skinned individuals (Fitzpatrick types I and II), and long-term immunosuppression constitute other major risk factors. Calcineurin inhibitors such as tacrolimus (TAC) are commonly administered to suppress the immune system and prevent donor organ rejection. Previous studies have elucidated the off-target effects of immunosuppressives such as azathioprine (AZA) and cyclosporin A (CSA). We hypothesized that TAC might potentiate cSCC tumorigenesis by exerting pro-tumoral effects on keratinocytes. Hence, we examined cell proliferation, survival, and invasion in human keratinocytes, primary dermal fibroblasts and cSCC cells using BrdU incorporation, crystal violet staining, western blotting, and 3D spheroids, respectively. Preliminary results show that TAC promotes cell survival in a dose-dependent manner in A431 cells. Additionally, cell invasion is significantly enhanced at increasing concentrations, especially in the presence of a fibroblast coculture. However, it is unclear whether cell proliferation is affected due to cyclical dose-response effects. p-ERK 1/2 and p-RB expression levels increase with distinct drug concentrations. Concerning ROS, NQO1 levels increase concurrently with increasing TAC doses, suggesting its role in ROS activation in cSCC cells. Altogether, our findings illuminate the interaction between tumor and stromal cells in cell invasion and support the carcinogenic role of TAC in non-immune mediated cSCC pathogenesis.