GDF15 and cancer: Previously, elevated levels of GDF-15 have been linked to several pathological conditions, such as atherosclerosis [18,19], chronic heart failure [20,21,22], chronic kidney disease [24], diabetes mellitus and insulin resistance [14,15], type 1 diabetes [25], several autoimmune disorders [26,27], several different types of cancer [28,29], cancer cachexia [30,31], severe primary mitochondrial diseases [32,33], pulmonary diseases [34,35,36], and neurodegenerative disorders (Alzheimer’s disease, cerebral stroke, and Parkinson’s disease) [37,38].