Bexarotene – a novel modulator of AURKA and the primary cilium in VHL-deficient cells

Loss of von Hippel Lindau ( VHL ) is associated with loss of primary cilia and is causally linked to elevated Aurora Kinase A (AURKA). We developed an image-based HTS assay using a dual-labelling image analysis strategy that identifies both the cilium and the basal body. Using this strategy, we screened small molecule compounds for the targeted rescue of cilia defects associated with VHL -deficiency with high accuracy and reproducibility. Bexarotene was identified and validated as a positive regulator of the primary cilium. Importantly, the inability of an alternate retinoid X receptor (RXR) agonist to rescue ciliogenesis, in contrast to bexarotene, suggested the existence of multiple bexarotene driven mechanisms. We found that bexarotene decreased AURKA expression in VHL -deficient cells, thereby restoring the ability of these cells to ciliate in the absence of VHL . Finally, bexarotene treatment reduced the propensity of subcutaneous lesions to develop into tumors in a mouse xenograft model of RCC, with a concomitant decrease in activated AURKA, highlighting the potential of bexarotene as an intervention strategy in the clinic to manage renal cystogenesis associated with VHL -deficiency and elevated AURKA expression.