Knockdown of Keratin 6 Within Arsenite-Transformed Human Urothelial Cells Decreases Basal/Squamous Expression, Inhibits Growth, and Increases Cisplatin Sensitivity

Urothelial carcinoma (UC) is prevalent, especially in elderly males. The high rate of recurrence, treatment regime, and follow-up monitoring make UC a global health and economic burden. Arsenic is a ubiquitous toxicant that can be found in drinking water, and it is known that exposure to arsenic is associated with UC development. Around 25% of diagnosed UC cases are muscle-invasive (MIUC) which have poor prognosis and develop chemoresistance, especially if tumors are associated with squamous differentiation (SD). The immortalized UROtsa cell line is derived from normal human urothelium and our lab has malignantly transformed these cells using arsenite (As³⁺). These cells represent a basal subtype model of MIUC and the tumors derived from the As³⁺-transformed cells histologically and molecularly resemble clinical cases of the basal subtype of MIUC that have focal areas SD and expression of the basal keratins (KRT1, 5, 6, 14, and 16). Our previous data demonstrate that KRT6 protein expression correlates to areas of SD within the tumors. For this study, we performed a lentiviral knockdown of KRT6 in As³⁺-transformed UROtsa cells to evaluate the effects on morphology, gene/protein expression, growth, colony formation, and cisplatin sensitivity. The knockdown of KRT6 resulted in decreased expression of the basal keratins, decreased growth, decreased colony formation, and increased sensitivity to cisplatin, the standard treatment for MIUC. The results of this study suggest that KRT6 plays a role in UC cell growth and is an exploitable target to increase cisplatin sensitivity for MIUC tumors that may have developed resistance to cisplatin treatment.