Abstract
BackgroundSilencing of tumor suppressor genes (TSGs) or activation of oncogenes by, e.g., aberrant promoter methylation, may be early events during carcinogenesis. The methylation status of such genes can be used for early detection of cancer. We are pursuing this approach in our efforts to develop markers for early detection and follow-up of nasopharyngeal carcinoma (NPC). We set out to develop this approach to allow identification of NPC from Morocco and then also compared with NPC samples from different geographical locations and different ethnicity with different NPC incidences, Epstein-Barr virus (EBV) prevalence, and environments.ResultsBy multiplex methylation-specific PCR (MMSP), multiple relevant genes can be detected simultaneously, to achieve high sensitivity and specificity. The strong association of EBV with NPC is also very useful in such an approach. We have initially screened for 12 potential marker genes including EBV genes coding for EBV nuclear antigen 1 (EBNA1) and latent membrane protein-1 (LMP1) and ten potential TSGs obtained from previously published data. The resulting assay included EBNA1, LMP1, and three cellular TSGs: ITGA9, RASSF1A, and P16. We evaluated this assay on 64 NPC patient biopsies from Morocco, Italy, and China compared to deoxyribonucleic acid (DNA) from 20 nasopharyngeal control tissues. In the Moroccan NPC cohort (n = 44), prevalence of the EBNA1 gene showed the highest sensitivity (36/44; 82 %) with 94 % specificity. Out of eight (18 %) EBNA1 negative Moroccan samples, only three were positive for at least one methylated cellular gene. By detection of cellular marker genes, the sensitivity increased from 82 to 89 % (39/44). In the whole material of 64 biopsies from three geographical locations, at least any one marker (viral or cellular) could be detected in 91 % of biopsies with 90 % specificity. In a pilot evaluating assay performance on serum DNA from NPC and controls including samples from Italy (n = 11) and China (n = 5), at least any one marker from the MMSP assay could be detected in 88 %, but the specificity was only 50 %.ConclusionsAn MMSP assay has the potential for detection of NPC by screening in high-risk populations. Serum-derived DNA seems not as good as earlier published NPC swab DNA for screening purpose.
Highlights
Silencing of tumor suppressor genes (TSGs) or activation of oncogenes by, e.g., aberrant promoter methylation, may be early events during carcinogenesis
Identification of additional candidate methylated markers for nasopharyngeal carcinoma (NPC) using methylation-specific PCR (MSP) All the deoxyribonucleic acid (DNA) from the NPC and normal biopsy samples from Morocco were screened using MSP for 12 markers
A combination of methylation-regulated TSGs including Ras association domain family member 1 (RASSF1A), cyclin-dependent kinase inhibitor 2A (P16), and Epstein-Barr virus (EBV)-based markers could serve as a complementary test for the early detection of NPC [47, 61]
Summary
Silencing of tumor suppressor genes (TSGs) or activation of oncogenes by, e.g., aberrant promoter methylation, may be early events during carcinogenesis. NPC has been reported to be the most common neoplasia of the nasopharynx and respiratory tract in children in Morocco and Tunisia accounting for 5–20 % of childhood malignancies [10, 11, 9]. This is even higher than its incidence in the high endemic NPC areas in China, where it is 0.1 % in children [12, 13]. Chromosomal abnormalities and aberrant promoter hypermethylation show a similar pattern in different geographical regions according to one study so far, supporting a common carcinogenic pathway to NPC irrespective of region [21]
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