The present invention relates to a pharmaceutical composition for preventing or treating cancer containing pleiotropic regulator 1 (PLRG1) inhibitor as an active ingredient, a method for treating cancer including administering the composition to a subject, a composition for diagnosing cancer containing an agent for measuring the expression level of PLRG1, a method for providing information for diagnosing cancer including measuring the expression level of PLRG1, and a method for screening agents for preventing or treating cancer.Pleiotropic regulator 1 (PLRG1) is overexpressed in cancer cells, and the inhibition of the expression of PLRG1 can induce cancer cell-specific apoptosis. Accordingly, the PLRG1 inhibitor of the present invention has an excellent effect as an anticancer agent without side effects, and additionally, the PLRG1 inhibitor can be used for cancer diagnosis, screening of anticancer agents, etc. by measuring the expression levels of PLRG1.
