HINT1 and neoplasm: HINT1 overexpression reduces the growth rate of several cancer cells, such as melanoma, colon cancer, gastric cancer, and lung cancer, or induces apoptosis in SW480 and MCF7 cells6,8–10, whereas Hint1 deficiency enhances the growth and spontaneous immortalization of mouse embryonic fibroblasts4, supporting the claim that HINT1 might act as a tumor suppressor in some types of cancer.