NOS1 and neoplasm: In contrast, NOS2 is inducible, becomes increasingly expressed in response to inflammation, and produces high levels of NO in a calcium-independent manner.7 Thus, the existing evidence suggests that NOS1 and NOS3 mainly function in promoting tumor development, while depending on the state of a cell, NOS2 might also play an additional role in tumor progression, However, it remains unknown whether distinct NOS isoforms play different roles in regulating autophagy, and which signaling pathways are involved.