462 Reticular dermis is more conductive to invasion of squamous cell carcinoma than papillary dermis in human fibroblast derived skin models emulating skin aging

Abstract

Lesional skin in mycosis fungoides (MF) is populated primarily by benign and neoplastic T-cells. PUVA is an effective therapy for MF but its effects on these two populations are uncharacterized. We studied skin biopsies from 8 MF patients before and after 12-16 weeks of PUVA using high throughput TCR sequencing and nanostring-based gene expression profiling. Patients had an average mSWAT score of 19.7 before therapy and experienced an average 88% improvement in mSWAT scores after therapy. The total number of T-cells in skin decreased by 50% after therapy, from a mean 150,435 T-cells/100ng DNA to 76,200. However, the percentage of malignant clones was not significantly different despite evident clinical improvement. Clonal malignant T-cells made up 44% of the total T-cell population before therapy and 40% after. Effective PUVA therapy was associated with large shifts in the benign T-cell population. 49% of benign clones in skin present before therapy were eliminated by PUVA, and large numbers of new benign T-cells not previously present in skin were recruited into skin following therapy. After therapy, newly recruited benign T-cell clones made up 52% of the total T-cell population and clones present before therapy made up only 8%. A linear regression analysis demonstrated that clinical improvement correlated with turnover of benign T-cell clones (R¼0.8, p¼0.01) but not with reduction of malignant T-cells (R¼0.13, p¼0.4). Nanostring analyses demonstrated reduction in STAT6, suggesting reduced Th2 responses, and increases in genes associated with cytotoxicity, innate cell and NK cell activation. These studies suggest that PUVA may induce a shift in benign T-cell populations away from a phenotype that supports malignant T-cell activation and towards a phenotype that restrains it. In summary, PUVA exerts its effects by modulating benign T-cell populations, in a way that may deprive malignant T-cells of necessary activation signals.