Oncolytic Adenovirus With Temozolomide Induces Autophagy and Antitumor Immune Responses in Cancer Patients

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Oncolytic adenoviruses and certain chemotherapeutics can induce autophagy and immunogenic cancer cell death. We hypothesized that the combination of oncolytic adenovirus with low-dose temozolomide (TMZ) is safe, effective, and capable of inducing antitumor immune responses. Metronomic low-dose cyclophosphamide (CP) was added to selectively reduce regulatory T-cells. Preclinically, combination therapy inhibited tumor growth, increased autophagy, and triggered immunogenic cell death as indicated by elevated calreticulin, adenosine triphosphate (ATP) release, and nuclear protein high-mobility group box-1 (HMGB1) secretion. A total of 41 combination treatments given to 17 chemotherapy-refractory cancer patients were well tolerated. We observed anti- and proinflammatory cytokine release, evidence of virus replication, and induction of neutralizing antibodies. Tumor cells showed increased autophagy post-treatment. Release of HMGB1 into serum--a possible indicator of immune response--increased in 60% of treatments, and seemed to correlate with tumor-specific T-cell responses, observed in 10/15 cases overall (P = 0.0833). Evidence of antitumor efficacy was seen in 67% of evaluable treatments with a trend for increased survival over matched controls treated with virus only. In summary, the combination of oncolytic adenovirus with low-dose TMZ and metronomic CP increased tumor cell autophagy, elicited antitumor immune responses, and showed promising safety and efficacy.