Disrupted regulation of serpinB9 in circulating T cells is associated with an increased risk for post-transplant skin cancer

K. Boer, F.S. Peters, A.M.A. Peeters, J. van de Wetering, M.G.H. Betjes, C.C. Baan

Thursday 14 march 2019

11:00 - 11:10h at Tropentheater

Categories: Best abstracts, Parallelsessie

Parallel session: Parallelsessie XII – Best abstracts III

Background: Non-melanoma skin cancer such as cutaneous squamous cell carcinoma (cSCC) is a serious complication after organ transplantation and patients would benefit from an early risk assessment. We hypothesized that functional differences in circulating T cells may represent risk factors for post-transplant cSCC development.

Methods: In a first cohort of 19 kidney transplant recipients with a future cSCC and 19 matched kidney transplant recipients without cSCC, genome-wide DNA methylation was measured by Illumina’s 450k arrays. Differentially methylated regions (DMRs) were identified and the most significant region was validated with pyrosequencing in a second cohort of 45 kidney transplant recipients during recurrent cSCC. Downstream effect on RNA and protein expression was measured with RT-qPCR and flow cytometry.

Results: Before the clinical onset of cSCC, the most significant DMR identified was located in the SERPINB9gene. SERPINB9, an intracellular inhibitor of granzyme B (an inducer of apoptosis), was significantly higher methylated in cSCC patients compared to non-cSCC patients (p=1.1·10-13). Also in the second cohort during recurrent cSCC, median DNA methylation of SERPINB9was higher in the cSCC patients compared to the non-cSCC patients (58.7% (32.5%-81.3%) and 50.2% (21.8%-77.5%); p=0.004). RNA expression was significantly correlated to DNA methylation only in the non-cSCC patients (r=-0.64, p=0.0003), indicating a disrupted transcription of SERPINB9in the cSCC patients. After poly-clonal stimulation, serpinB9 expression increased both in cSCC and non-cSCC patients but expression levels were significantly lower in cSCC patients compared to the non-cSCC patients (98.2% (93.0%-99.0%) vs 99.1% (97.2%-99.7%); p=0.006).

Conclusions: DNA methylation, transcriptionalregulation and protein expression of serpinB9 in circulating T cells differs between cSCC and non-cSCC patients. This disturbed regulation of serpinB9 represents a novel risk factor for the development of cSCC after kidney transplantation.