The present invention relates to a pharmaceutical composition for an anticancer adjuvant comprising a receptor-interacting protein kinase-3 (RIP3) protein expression promotor or activator as an active ingredient. In addition, the present invention provides a method of promoting cancer cell apoptosis, characterized by co-administering an anticancer agent and a RIP3 protein expression promotor or activator to cancer cells. Also, the present invention relates to a method for screening an anticancer adjuvant which promotes RIP3 expression and enhances sensitivity of an anticancer agent, and a method for monitoring sensitivity of an anticancer agent depending on the RIP3 expression. Accordingly, in the case of a patient lacking the expression of RIP3, it is expected to be an effective treatment strategy to pre-treat a demethylating agent to induce the expression of RIP3 and then to use a conventional chemotherapeutic agent. In addition, in chemotherapy, it is anticipated that the present invention may be an effective strategy in screening an anticancer adjuvant which monitors and enhances sensitivity of an anticancer agent.