Clinical utility of serum epigenetics in cutaneous melanoma
Cutaneous melanoma is an aggressive malignancy with a poor prognosis once metastatic. New anti-melanoma agents have impressively improved clinical outcomes in patients with advanced melanoma. However, the disease relapses within months and the prognosis for patients with high volume metastatic melanoma remains very poor. New strategies for early diagnosis of metastatic melanoma are urgently needed. Cancer-associated gene promoter methylation is an important mechanism in tumour progression. Cancer-specific methylation markers identified in patients’ tissues and blood may help reveal the mechanisms underlying melanoma progression, and offer promise as biomarkers for early diagnosis of metastasis and prediction of patient outcome.
This study has included 19 melanoma cell lines, 120 patient tissues (primary and metastatic melanoma and benign melanocytic naevi) and 41 serum samples. We have explored pyrosequencing, bisulfite sequencing and methylation specific PCR to investigate methylation status of candidate genes, and qPCR to evaluate their mRNA expression. Statistical analyses including Mann-Whitney U test, student t test, and receiver operating characteristic (ROC) analysis have been performed.
We have detected TFPI2, NT5E and several other candidate genes methylated in melanoma cell lines and in patient materials. TFPI2 hypermethylation in 11/17 (65%) melanoma cell lines was associated with low mRNA levels and correlated significantly with metastatic disease in tumour samples (p<0.05). Analysis of patients’ sera identified methylated TFPI2 as a promising epigenetic biomarker of metastasis with high sensitivity (85%) and specificity (87%). In contrast, NT5E methylation appears to be a good prognostic biomarker for both primary and metastatic melanoma.
TFPI2 and NT5E are epigenetically dysregulated in melanoma, with NT5E and TFPI2 promoter methylation predicting good and bad prognosis, respectively. Hypermethylated TFPI2 and other novel candidates show great promise as serum epigenetic biomarkers with clinical utility for early detection of metastasis.
This work was funded by The Leng Charitable Trust, The Tayside Dermatology Research Fund and Cancer Research UK.
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