KRT5 (A) and KRT6C (B) expression in chemotherapy resistant primary serous ovarian cancer cells (n = 10) compared to chemotherapy sensitive cells (n = 9) and OVCAR5 CBPR made resistant to carboplatin (CBP). KRT5 but not KRT6C was significantly increased in chemotherapy resistant cells (n = 10) compared to chemotherapy sensitive cells (n = 9, *P = 0.0006, Mann Whitney U test). Both KRT5 (*P < 0.0001, Mann Whitney U test) and KRT6C (*P = 0.0004, Mann Whitney U test) were significantly increased in CBP resistant OVCAR-5 CBPR cells compared to parental OVCAR-5 cells. Data for the primary cells is expressed as the mean fold change from 3-6 RNA samples from 2 independent experiments. Data for OVCAR5 cells is expressed as the mean fold change ± SEM from 10 individual RNA samples from 3 independent experiments. (C) K5 immunocytochemistry in serous ovarian cancer cells (OVCAR-5, OAW28, OVCAR-3 & COV362) ± 48 hr treatment with CBP IC50 and in parental OVCAR5 and CBP resistant OVCAR5 cells (OVCAR5 CBPR). (D) K5+ cells are increased following 48 hr treatment with an IC50 dose of CBP and the development of chemoresistance. *P < 0.05 (unpaired student t test), data is expressed as mean % positive cells ± SEM from 3-4 independent experiments.