PCNA and head and neck squamous cell carcinoma: Of note, PCNA forms a complex with Hsp90 in HCT-116 (human colon cancer cell line), HT-29 (human colorectal adenocarcinoma), and in HNSCC-1483 (human head and neck cancer cell line), the treatment with geldanamycin resulting in the degradation of both PCNA and Hsp90 [189].