sodium-bisulfite and Nasopharyngeal-Neoplasms

Gene-specific methylation is common in primary undifferentiated nasopharyngeal carcinoma (NPC). DNA released from apoptotic or necrotic cell death including those aberrantly methylated promoter DNA of cancer cells is absorbed into the circulation as cell-free plasma DNA of the patient. This study aims at evaluation of the potential use of methylated gene promoter DNA as a serological tumor marker of primary and potentially salvageable local or nodal recurrent NPC.. The quantity of plasma hypermethylated gene promoters of CDH1, DAPK1, p15, p16, RASSF1A, and MLH1 of 41 NPC patients before treatment and 43 normal individuals were studied using real-time quantitative PCR. The post-treatment plasma hypermethylated CDH1, DAPK1,and p16 were also measured in 13 NPC patients with locoregional recurrence and 17 patients in remission.. Concentrations of cell-free circulating DNA were significantly higher in NPC patients than normal controls (28.79 ng/ml versus 16.57 ng/ml, respectively). There was no significant difference in plasma DNA concentration of EBV-positive and -negative normal individuals. Methylated DNA was detectable in plasma of NPC patients before treatment including 46% for CDH1,42% for p16,20% for DAPK1,20% for p15,and 5% for RASSF1A. Hypermethylated MLH1 was not detected in plasma of all of the NPC patients and normal individuals. Aberrantly hypermethylated promoter DNA of at least one of the five genes was detectable in 29 of 41 (71%) plasma of NPC patients before treatment. Hypermethylated promoter DNA of at least one of the three genes (CDH1, DAPK1, and p16) was detectable in post-treatment plasma of 5 of 13 (38%) recurrent NPC patients and none of the patients in remission.. Our results suggested that cell-free circulating methylated gene promoter DNA is a possibly useful serological marker in assisting in screening of primary and potentially salvageable local or regional recurrent NPC.

Topics: Adult; Aged; Biomarkers, Tumor; Carcinoma; Cell Differentiation; Cell-Free System; Disease-Free Survival; DNA; DNA Methylation; Female; Genetic Markers; Herpesvirus 4, Human; Humans; Immunoglobulin A; Male; Middle Aged; Nasopharyngeal Neoplasms; Promoter Regions, Genetic; Recurrence; Reverse Transcriptase Polymerase Chain Reaction; Sulfites; Time Factors

Nonrandom allelic loss on chromosome 3p is a common event in nasopharyngeal carcinoma (NPC) with the implication that certain tumor suppressor gene(s) in this region are involved in the pathogenesis of these tumors. The BLU gene, located at 3p21.3, has recently been identified as a candidate tumor suppressor gene due to the occurrence of missense mutations and loss of its expression in lung cancer. To investigate the involvement of BLU gene in NPC, we examined both genetic and epigenetic changes of BLU in NPC primary tumors and cell lines. No pathogenic mutations were detected in the entire coding region of this gene in 45 primary NPC tumors and 5 NPC cell lines. While BLU was expressed in 100% (15 of 15) of noncancerous nasopharyngeal epithelia, its transcripts were missing in all 5 NPC cell lines, and absent or reduced mRNA levels were observed in 78% (28 of 36) of the primary tumors. In the NPC cell lines, loss of BLU expression correlated with hypermethylation of the CpG island promoter sequence, and expression was restored after treatment with 5'-aza-2'-deoxycytidine. Methylation specific PCR analysis revealed that the BLU promoter was highly methylated in 74% (17 of 23) of primary tumors in which BLU was downregulated, whereas only 2 of 9 non-neoplastic nasopharyngeal epithelia exhibited hypermethylation in the BLU promoter region. The high incidence of BLU alterations suggests that it may be one of the critical tumor suppressor genes on chromosome 3p21.3 involved in the development of NPC.

Topics: Adult; Aged; Azacitidine; Base Sequence; Carcinoma; Chromosomes, Human, Pair 3; CpG Islands; Cytoskeletal Proteins; Decitabine; DNA Methylation; DNA Primers; Enzyme Inhibitors; Genes, Tumor Suppressor; Humans; Middle Aged; Molecular Sequence Data; Mutagens; Mutation; Nasopharyngeal Neoplasms; Polymerase Chain Reaction; Promoter Regions, Genetic; Protein Biosynthesis; Proteins; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Sequence Analysis, DNA; Sulfites; Tumor Cells, Cultured; Tumor Suppressor Proteins