This is the first time, to the best of our knowledge, that a comparison has been made in one study of the effects of TMZ in a TMZ-responsive tumor model, i.e., U87MG and GL261 cells, and of non-responsive models related to their MGMT promotor methylation status, i.e., U118MG and U138MG cells. The gene discussed is MGMT; the disease is neoplasm.