Plasma circulating cell free messenger RNA as a potential biomarker of melanoma

Background: Blood borne cell free nucleic acids are increasingly emerging as significant non-invasive adjuncts to current methods of disease status evaluation in cancer patients. In this study, we sought to examine whether significant differences exist in the plasma transcriptomic profile of advanced melanoma patients with a high disease burden compared to patients with a low disease burden or therapeutic response. Methods: Pathway focussed gene expression analysis was performed using cDNA derived from the plasma circulating cell free messenger ribonucleic acid (ccfmRNA) samples of twenty-two patients with advanced melanoma. Patients were assessed with paired blood sample collection and CT scan assessments at baseline and at 3 months follow up. Results: We identified several genes which were significantly over-expressed in patients with a low disease burden or therapeutic response; BCL2L1, CXCL9, IDO1, IL13, MIF, MYD88 and TLR4 (p ≤ 0.001, versus high disease burden). There was an increase in the magnitude of fold change (2^ (-dd CT)) of BCL2L1 (p = 0.031), CCL4 (p = 0.001), CCL5 (p = 0.043), CXCL9 (p = 0.012), GZMB (p = 0.023) and TNFSF10 (p = 0.039) genes in patients with therapeutic response at 3 months follow up assessment relative to baseline assessment. Moreover, in stage IV melanoma patients with brain metastases, CCL18, CCR1, CCR4, CD274, CSF2, EGF, and PTGS2 genes were significantly over-expressed (p < 0.001, versus patients without melanoma brain metastasis). Conclusion: Significant differences were observed in the plasma transcriptomic profile between the various melanoma patient groups, and we postulate that these differences may be exploited to identify novel therapeutic targets or biomarkers relevant to melanoma.