TMEM97 and cancer: As we have recently published a more comprehensive review of the literature and perspective on Sigma1 biology and Sigma1 pharmacology in the context of cancer elsewhere (Kim and Maher, 2017), in the present review article, we will focus on and expand our discussion of Sigma1 and Sigma2/TMEM97 ligands and their actions in cancer-relevant physiological processes, including cancer cell proliferation, growth, motility, migration, survival, and death (by apoptotic and non-apoptotic mechanisms), as well as protein homeostasis, lipid metabolism, and immune modulation.