Interleukin 32 (IL32) is proinflammatory cytokine that in humans is encoded by the IL32gene.[3] Interleukin 32 can be found in higher mammals but not in rodents. It is mainly expressed intracellularly and the protein has nine different isoforms, because the pre-mRNA can be alternatively spliced.[4][5] The most active and studied isoform is IL-32γ. It was first reported in 2005,[6] although the IL-32 gene was first described in 1992.[7] It does not belong to any cytokine family because there is almost no homology with other cytokines.[5]
mRNA of IL-32 is mostly expressed in immune cells but also can be expressed in other tissues such as spleen, thymus, lung, small intestine, colon, prostate, heart, placenta, liver, muscle, kidney, pancreas and brain.[4][5]
Interleukin 32 is connected with several diseases, including cancer.
Function
This gene encodes a member of the cytokine family. The protein contains a tyrosine sulfation site, 3 potential N-myristoylation sites, multiple putative phosphorylation sites, and an RGD cell-attachment sequence. Expression of this protein is increased after the activation of T-cells by mitogens or the activation of NK cells by IL-2. This protein induces the production of TNF-alpha from macrophage cells. Alternate transcriptional splice variants, encoding different isoforms, have been characterized.[3]
IL-32 can be mainly found in cytoplasm of cancer cells. In various cancer tissues, IL32 is highly expressed and presently, the most common isoform of IL-32 found in cancer cells is IL-32β.[10][11]
Function of IL-32 can be very different, depending on its isoform (different isoforms can interact with each other and influence their activities)[5] and type of cell, where it is expressed.
IL-32 supports the tumor progression by cytokines expressed after activation of transcription factor NF-κB (nuclear factor-kB) and by metalloproteinase production. In addition, IL-32 stimulates differentiation into immunosuppressive cell types in some cancer types. These effects of IL-32 support tumor growth. On the other hand, in other cancer types it can also induce tumor cell apoptosis and enhance NK a cytotoxic T cell sensitivity which suppress tumor growth.[10]
