Targeting FGFR Attenuates Tumor Growth in an Anal Squamous Cell Carcinoma Patient Derived Xenograft Model.

Anal squamous cell carcinoma (ASCC) is a rare malignancy with a rising incidence and limited treatment options. To identify actionable therapeutic targets, we developed a patient-derived xenograft (PDX) model using a metastatic ASCC sample and performed single-cell RNA sequencing. Our analysis confirmed previously reported genetic mutations highly expressed in the sample, along with copy number alterations, and revealed epithelial cancer cell heterogeneity. Notably, epithelial cells exhibited a low hybrid epithelial-mesenchymal transition (hEMT) signature compared to stromal cells. Among epithelial subpopulations, the most abundant cluster displayed high expression of FGFR1-2 and FGF ligands. Treatment with AZD4547, an FGFR1-3 inhibitor, resulted in a significant reduction in tumor volume over time (p = 0.0036). Immunohistochemistry staining for proliferative Ki67 and cleaved caspase 3 suggested ongoing proliferation in residual cells. Fourier-transform infrared (FTIR) spectroscopy of post-treatment residual tumors revealed significant differences in the Amide I and Amide II regions between AZD4547-treated and control groups. These findings demonstrate that FGFR inhibition effectively attenuates ASCC tumor growth and highlights the promise of precision medicine in managing this rare cancer.