Keratoacanthomas have an immunosuppressive cytokine environment of increased IL-10 and decreased GM-CSF compared to squamous cell carcinomas

To investigate the relationship between keratoacanthoma (KA) and squamous c ell carcinoma (SCC), cytokine mRNA in 12 KA and eight SCC were compared. No rmal skin was also studied. Reverse transcription polymerase chain reaction (RT-PCR) was used to quantitate mRNA in each sample utilizing DNA standard s. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was used as an internal control, and CD3 delta as an indication of the T-cell infiltrate. KAs show ed a significant increase in interleukin (IL)-10, and a decrease in granulo cyte macrophage colony-stimulating factor (GM-CSF) mRNA compared to SCCs. C D3 delta mRNA was also increased in the KAs. There was no difference betwee n KAs and SCCs in expression of lymphotoxin-alpha, IL-2, interferon-gamma ( IFN-gamma), IL-13, transforming growth factor-beta (TGF-beta), or the pro-i nflammatory cytokines IL-8 or tumour necrosis factor-alpha (TNF-alpha). The se results indicate that KAs spontaneously resolve in an immunosuppressive environment. KAs grow rapidly over a period of weeks and then involute. It is possible that a suppressed immune response enables unimpeded growth and that the KA cells rapidly undergo the finite number of cell divisions of wh ich they are capable, and then die without reaching immortality.