Thus, we cannot rule out the possibility that SM-GDF15 (being an immature form) is not proportionally connected with the levels of c-GDF15 (therefore accounting for the missing association between the two forms), however, it is known that many other organs and tissues produce this protein, including prostate, kidney, lung, but also senescent cells and many types of cancers (13, 26, 58–60). This evidence concerns the gene GDF15 and cancer.