GDF15 and neoplasm: Since other hormones such as growth differentiation factor 15 (GDF15) can also be released from autophagy-deficient hepatocytes (Kim et al., unpublished results) and GDF15 can act as either tumor-promoting or tumor-suppressive hormone, several hormones or factors from autophagy-deficient cells or tumors might be able to affect the growth of autophagy-deficient tumors and host metabolism (18, 40, 41).