Paclitaxel resistance in ovarian cancer increases oncolytic adenovirus efficacy via upregulated CAR expression and dysfunctional cell cycle control

The microtubule-stabilising drug paclitaxel has activity in relapsed ovarian cancer. However, resistance frequently develops. Oncolytic adenoviruses are a novel cancer therapy, and replicate selectively within and lyse malignant cells, leading to productive infection of neighbouring cells. We found increased efficacy of adenoviruses of multiple subtypes in paclitaxel-resistant ovarian cancer cells. There was increased expression of a key adenovirus receptor, CAR (coxsackie adenovirus receptor), due to increased transcription that resulted from histone modification. Moreover, CAR transcription increased in intraperitoneal xenografts with acquired paclitaxel resistance and in tumours from patients with paclitaxel-resistant ovarian cancer. Finally, we identified dysregulated cell cycle control as a second mechanism of increased adenovirus efficacy in paclitaxel-resistant ovarian cancer and that inhibition of CDK4/6 using PD-0332991 was able both to reverse paclitaxel resistance and reduce adenovirus efficacy. Thus, paclitaxel resistance increases oncolytic adenovirus efficacy via at least two separate mechanisms. Parental SKOV3 and paclitaxel-resistant SKOV3-TR cells were analysed in duplicate