TH17 is involved in the remarkable regression of metastatic malignant melanoma to topical diphencyprone.

The authors provide an update on a previously reported patient with in-transit metastatic melanoma of the scalp treated with topical diphencyprone (DPCP). Molecular studies implicate the thymus-derived TH17 lymphocyte subset in a remarkable immunotherapeutic regression. The authors performed RT-PCR of total RNA from paraffin-embedded tissue before and after treatment with DPCP. Before treatment with DPCP, the authors found elevated expression of IL 17C/D/E/F; after treatment there was no detectable expression. Conversely, increased expression of PLZF/CD27 and CTLA4 was seen after treatment with no expression before treatment. No expression of IL17A/B, CD7, RORgTand FoxP3 were before or after treatment. Conclusions are limited to only the time samples were obtained. Remarkable regression of an in-transit metastatic melanoma treated with the immunomodulatory agent DPCP showed gain and loss of gene expression of the TH17 pathway. Further study of this pathway from NK to NK-T to TH7 and TH1 cells both with and without accessory or dendritic cells will improve understanding of contact sensitizers as topical immunomodulators.