Disclosed are lysine specific histone demethylase-1 (LSD1) inhibitors in methods and compositions for immune checkpoint inhibition. The invention also relates to proteinaceous molecules and their use in altering at least one of (i) formation, (ii) 5 proliferation, (iii) maintenance, (iv) epithelial to mesenchymal cell transition (EMT), or (v) mesenchymal to epithelial cell transition (MET) of an LSD1 overexpressing cell.