HSP90AB1 and malignant colon neoplasm: Importantly, stable expression of Hsp90/S595A in two K-Ras MT colon cancer cell lines decreases endogenous K-Ras expression as compared to the WT Hsp90 transfection and confers a resistance to 17-AAG-induced inhibition of colony formation and cell growth (Supporting information, Figure S3A-C).