Transcriptomic profiling of peripheral blood mononuclear cells in patients with multiple primary melanoma.

Abstract

e21558 Background: Patients (PTs) with cutaneous melanoma (MEL) are at increased risk of developing subsequent MEL. The primary objective of the present study was to determine whether the peripheral blood gene expression profile (GEP) of PTs with multiple primary melanoma (MPM) differs from that of patients with single primary melanoma (SPM) and healthy controls (HCs). A secondary objective is to assess if the peripheral blood immune transcriptional profile varies in relation with clinical and immunopathological characteristics of MEL. Methods: Cases with MPM, SPM and HCs were retrieved from the University of Pittsburgh Human Biological Sample and Nevus Image Banking and Analysis Repository. NanoString PanCancer Immune Profiling of 770-immune related genes was used to define GEP in peripheral blood mononuclear cells (PBMCs). Quality control (QC), data normalization, and differential expression analyses were performed using the ROSALIND Analysis System. Genes with fold change ≥1.5 and p-value < 0.05 were considered as differentially-expressed between cohorts. Results: In total, 47 PTs including 10 with SPM, 40 with MPM, and 10 HCs, were included. GEP data from 3 cases did not meet QC requirements and were discarded. The majority of PTs had stage I/II disease (87.2%). The median Breslow thickness was 1 mm, ulceration was present in 6 (12.2%) MELs. Tumor-infiltrating lymphocytes (TILs) were absent, non-brisk, and brisk in 20%, 65%, 15% of cases, respectively. The expression of IFIT1, MX1, ISG15 was decreased in PTs with MPM in comparison to HCs. In comparison to SPMs, PTs with MPM demonstrated downregulation of B-cell receptor signaling pathway genes (CD19, CD22, CD79A, BLK). 14 genes involved in TNF-alpha effects on cytokine activity, cell motility, and apoptosis, and 12 genes in the IL18 signaling pathway were differentially expressed in PTs with Breslow thickness of >1mm vs ≤1mm. The top downregulated genes in >1mm thick MELs were CD83, VEGFA and CXCL3. Ulcerated MEL had decreased expression of CCL2, CCL3, CCL3L1, CCL4. Stage III MEL had decreased expression of GZMH, MHC Class II genes HLA-DMB, HLA-DRB3, lectin receptor family genes KLRC2 and KLRD1, as well as Type-1 immune-associated biomarkers IRF1, SYK, TBX21 in comparison to Stage I/II cases. Tumors deficient in TILs exhibited decreased expression of Granzyme A and B, T-box 21, and IL18RAP (enhances IL18R-mediated signaling) in peripheral blood. Tumors with brisk TILs had increased expression of the B-cell associated transcripts CD19, CD22, CD79A in peripheral blood. Conclusions: The GEP of PBMC's from PTs with MPM was similar overall to that of PTs with SPM/HC, with only a subset of genes exhibiting differentially expression in PTs with MPM vs. PTs with SPM and HCs. GEP varied in relation to Breslow thickness, stage, ulceration, and TIL content in MELs.