Temozolomide renders murine cancer cells susceptible to oncolytic adenovirus replication and oncolysis.

The preclinical evaluation of oncolytic adenoviruses (OAds) has been limited to cancer xenograft mouse models because OAds replicate poorly in murine cancer cells. The alkylating agent temozolomide (TMZ) has been shown to enhance oncolytic virotherapy in human cancer cells; therefore, we investigated whether TMZ could increase OAd replication and oncolysis in murine cancer cells. To test our hypothesis, three murine cancer cells were infected with OAd (E1b-deleted) alone or in combination with TMZ. TMZ increased OAd-mediated oncolysis in all three murine cancer cells tested. This increased oncolysis was, at least in part, due to productive virus replication, apoptosis, and autophagy induction. Most importantly, murine lung non-cancerous cells were not affected by OAd+TMZ. Moreover, TMZ increased Ad transduction efficiency. However, TMZ did not increase coxsackievirus and adenovirus receptor; therefore, other mechanism could be implicated on the transduction efficiency. These results showed, for the first time, that TMZ could render murine tumor cells more susceptible to oncolytic virotherapy. The proposed combination of OAds with TMZ presents an attractive approach towards the evaluation of OAd potency and safety in syngeneic mouse models using these murine cancer cell-lines in vivo.