Modulation of human telomerase reverse transcriptase in hepatocellular carcinoma

AIM:Most cancer cells acquire immortal capability by telornerase activation. The human telornerase reverse transcriptase gene (hTERT) is considered to be the major determinant of the enzymatic activity of human telomerase,and the hTERTpromoter contains several c-lylyc binding sites that mediate hTERTtranscriptional activation. Few studies have examined the role of hTERTin hepatocarcinogenesis,and the relationship between c-Myc and telomerase in human hepatocellular carcinoma tissue is unknown.METHODS:We measured hTERTmRNA levels and c-Myc oncoprotein expression in 57 patients with hepatocellular carcinoma using in situhybridization and immunohistochemistry,respectively. The transcription regulation of hTERT was evaluated by transient transfection of pGL3-1375 into the human hepatocellular carcinoma cell line J5. To determine the relationship between c-Myc and the hTERTpromoter, a 1375-bp DNA fragment encompassing the promoter was placed upstream of the luciferase reporter gene and transiently transfected into the cell line. Two additional hTERT promoter constructs (-776 and -100 bp region) and an hTERT promoter-LUC construct containing 2 c-Myc mutations (pGL3-181 MycMT) were also used for luciferase assays.RESULTS:In 30 of 57 cases (52%), hTERTmRNA expression was associated with c-Myc protein expression. However,16 of 57 cases (28%) showed strong hTERTmRNA detection without c-Myc protein expression, and 11 cases (19%) showed weak hTERTmRNA expression and strong c-Myc expression.Although luciferase activity was decreased between upstream 1375 bp and 776 bp, there was no significant difference between upstream 776 bp and 100 bp. Finally, there was no significant decrease in activity after transfection of the hTERT promoter-LUC construct.CONCLUSION:The results indicate that c-Myc does not play a major role in gene regulation of the catalytic subunit of telomerase (hTERT) in human hepatocellular carcinoma.Other regulatory elements or epigenetic phenomena should be further investigated to understand hTERTgene regulation in human hepatocellular carcinoma.

Copy number changes of target genes in chromosome 3q25.3-qter of esophageal squamous cell carcinoma: TP63is amplified in early carcinogenesis but down-regulated as disease progressed

AIM: By using comparative genomic hybridization, gain of 3q was found in 45-86% cases of esophageal squamous cell carcinoma (EC-SCC). Chromosome 3q25.3-qter is the minimal common region with several oncogenes found within this region. However, amplification patterns of these genes in EC-SCC have never been reported. The possible association of copy number changes of these genes with pathologic characteristics is still not clear. METHODS: Real-time quantitative PCR (Q-PCR) was performed to analyze the copy number changes of 13 candidate genes within this region in 60 primary tumors of EC-SCC, and possible association of copy number changes with pathologic characteristics was analyzed by statistics. Immunohistochemistry (IHC) study was also performed on another set of 111 primary tumors of EC-SCC to verify the association between TP63 expression change and lymph node metastasis status. RESULTS: The average copy numbers (±SE) per haploid genome of individual genes in 60 samples were (from centromere to telomere): SSR3: 4.19 (±0.69); CCNL1: 5.24 (±0.67); SMC4L1: 2.01 (±0.16); EVI1: 2.02 (±0.12); hTERC. 5.28 (±0.54); SKIL 2.71 (±0.14); EIF5A2. 1.95 (±0.12); ECT2: 9.18 (±1.68); PIK3CA: 8.13 (±1.17); EIF4G1: 1.07 (±0.05); 557: 3.07 (±0.25); TP63: 2.51 (±0.22); TFRC. 2.42 (±0.19). Four clusters of amplification were found: SSR3 and CCLN1 at 3q25.31; hTERC and SKIL at 3q26.2; ECT2 and PIK3CA at 3q26.31-q26.32; and 55T, TP63 and TFRC at 3q27.3-q29. Patients with lymph node metastasis had significantly lower copy number of TP63 in the primary tumor than those without lymph node metastasis. IHC study on tissue arrays also showed that patients with lymph node metastasis have significantly lower TP63 staining score in the primary tumor than those without lymph node metastasis. CONCLUSION: This study showed that different amplification patterns were seen among different genes within 3q25.3-qter in EC-SCC, and several novel candidate oncogenes (SSR3, SMC4L1, ECT2, and SST) were identified. TP63 is amplified in early stage of EC-SCC carcinogenesis but down-regulated in advanced stage of disease.