PDPN and squamous cell carcinoma: In human medicine, PDPN has been reported to be overexpressed in various types of tumors, including squamous cell carcinoma [5], astrocytoma [6], malignant mesothelioma [7], hemangiosarcoma [8], osteosarcoma [9], germinoma [10], and cancer-associated fibroblasts (CAFs) [11,12,13].