De-Methylation of the TSDR Is a Marker of Squamous Cell Carcinoma in Kidney Transplant Recipients.

Abstract

Malignancy remains a significant cause of morbidity in the transplant population, and is rapidly becoming the leading cause of death. Cutaneous squamous cell carcinoma (cSCC) is extremely common in transplant recipients, with 30% developing cSCC within 10 years of transplantation. Our previous investigations have shown that high numbers of regulatory T cells are associated with the development of cSCC in kidney transplant recipients (KTRs). Here we explore the stability of immune phenotype in KTRs over time ( ≥3 years). In addition we analysed the methylation analysis of the regulatory T cell (Treg) specific demethylated region (TSDR) which provides a more accurate measure of true Treg numbers. KTRs matched for Age, gender and duration of immunosuppression with (n=32) and without (n=27) cSCC, were analysed for putative clinical and immunological markers of cancer risk. Major lymphocyte subsets remained stable over time; although B cell, CD8 and CD4 subpopulations demonstrated age related changes. The proportion of FOXP3+ CD4+ cells remained higher in KTRs with a previous cSCC. Use of TSDR methylation analysis allowed for clarification of true Treg numbers, enhancing the association of high Treg levels in KTRs with cSCC compared to the cSCC free cohort(p=0.03; Figure 1).Figure 1.: Box plot showing the percentage of CD4+ lymphocytes that are TSDR-demethylated in KTRs who have (open box) or have not (cross-hatch box) developed an SCC post transplant. KTRs who have never developed an NMSC are shown in the vertical striped box.* = p = 0.03 ** = p = 0.008 These data validate and expand on previous findings in a population of long-term KTRs, and show that immune markers remain stable despite the chronic use of immunosuppression. TSDR demthylation analysis provides a more accurate biomarker of cancer post-transplantation.