IL-24 appears to control cell survival and proliferation by inducing rapid activation of particular transcription factors called STAT1 and STAT3.

This cytokine is predominantly released by activated monocytes, macrophages and T helper 2 (Th2) cells[5] and acts on skin, lung, and reproductive tissues.

The structure revealed that there is a lack of disulfides, which is present in most cytokines, and is likely the reason why IL-24 is unstable compared to other interleukins.

[12] IL-24 is a secreted protein that is highly conserved throughout evolution with sequence homology between species including yeast, dog, cat, monkey and cow.

The cDNA of IL-24 is 1,718 base pairs in length and encodes a protein of 206 amino acid with a predicted molecular size of ˜24 kDa.

[13] The signal peptide in IL-24 is two times the length as in other related human cytokines (51 amino acids), and the predicted molecular mass of IL-24 monomer is 18.3 kDa.

Its normal physiological role is connected with wound healing (In normal skin cells, it suppress keratinocyte proliferation during wound healing[15]), and protection against diseases caused by bacteria (for example Mycobacterim tuberculosis, Salmonella typhimurium, Pseudomonas aeruginosa).

The tumor suppressor activities of IL-24 include inhibition of angiogenesis, sensitization to chemotherapy, and induction of cancer-specific apoptosis.

Secreted IL-24 protein induces a robust expression of endogenous IL-24 and subsequent induction of tumor-specific killing through an ER stress-mediated pathway as well as by ROS production.

One possible reason for this differential killing effect involves inherent biochemical differences between normal and cancer cells (ER stress, ROS production and ceramide), another possibility is that IL-24 is able to target a molecule that only triggers apoptosis in cancer cells.