High intragenic methylation of SERPINB9, a regulator of cytotoxicity, in T cells as a marker for skin cancer after kidney transplantation
F.S. Peters, J. van de Wetering, M.G.H. Betjes, C.C. Baan, K. Boer
Thursday 15 march 2018
15:20 - 15:25h
at Willem Burger Foyer
Categories: Basic, Session (poster)
Parallel session: Poster session 4: Basic/translational research
Background
Cutaneous squamous cell carcinoma (cSCC) occurs 65-200 times more in organ transplant recipients than in the general population. T cells, which are targeted by immunosuppressive drugs, are involved in anti-tumor immune surveillance and their function is regulated by DNA methylation. Our previous study demonstrated higher DNA methylation of an intragenic region of SERPINB9 when comparing T cells from kidney transplant recipients before the occurrence of cSCC with T cells from recipients without cSCC. SERPINB9 codes for a serine protease inhibitor that inhibits Granzyme B and is actively transcribed in T cells. We hypothesized that high methylation of SERPINB9 is a stable trait and may affect the cytotoxic activity of T cells towards cSCC cells, thereby facilitating the development of cSCC.
Methods
A cohort of kidney transplant recipients was included containing recipients with a recurrent cSCC matched to recipients without cSCC. The recipients were included 13 years (±9 years) after transplantation and the cSCC patients developed their first cSCC 7 years (±6 years) after transplantation. PBMCs were collected and T cells were isolated from 30 recipients with cSCC and 26 recipients without cSCC. DNA methylation of 12 CpG sites within SERPINB9, including 5 sites that were analyzed in the previous study, were measured using pyrosequencing analysis with two sequence primers.
Results
Patient characteristics were not significantly different between the two groups, neither was T cell phenotype after cell sorting. DNA methylation was pooled per pyrosequencing reaction. Average DNA methylation of the first region within SERPINB9 containing 6 CpG sites, was 59%(±14%) for the cSCC patients and 51%(±13%) for the non-cSCC patients (p=0.03). The second region containing also 6 CpG sites showed an average DNA methylation of 55%(±14%) for the cSCC patients and 48%(±13%) for the non-cSCC patients (p=0.03).
Conclusion
Our results demonstrate that high intragenic methylation of SERPINB9 in T cells, previously found before the clinical onset of cSCC, can be validated in a different cohort of kidney transplant recipients during recurrent cSCC. This suggests a functional role for SERPINB9 methylation in cSCC development, possibly impairing T cells in exerting their cytotoxic activity towards cSCC cells. We conclude that high SERPINB9 methylation is stable throughout cSCC development which is a novel insight in the pathogenesis of cSCC in kidney transplant recipients.
