Expression of telomerase activity and oxidative stress in human hepatocellular carcinoma with cirrhosis

AIM: To study the expression and significance of telomerase activity and oxidative stress in hepatocellular carcinoma (HCC) with cirrhosis.METHODS: In this study, TRAP-ELISA assay was used to determine telomerase activity in 21 cases of HCC as well as in 23 cases of hepatic cirrhosis. Malondialdehyde(MDA),glutathione S-transferase (GST) and total anti-oxidative capacity (T-AOC) were also examined in the same samples with human MDA, GST and T-AOC kits.RESULTS: Eighteen of 21 cases of HCC were found to have increased telomerase activity, whereas only three of the 23non-cancerous cirrhotic samples were found to have weak telomerase activity, and the difference was significant (P＜0.001). No significant difference in telomerase activity was detected according to different tumor size, tumor stage,histological grade, HBsAg, contents of albumin, bilirubin,ALT, AFP, r-GT and platelet. There were significant differences between HCC and cirrhosis in the expression of MDA, GST and T-AOC respectively. Telomerase activity correlated positively with the content of MDA (P＜0.05).CONCLUSION: Telomerase activation is the early event of carcinogenesis, which is not correlated with clinicopathological factors of HCC. The dysfunction of the anti-oxidative system is closely correlated with the progression from cirrhosis to hepatocellular carcinoma. Oxidative stress may contribute partly to telomerase activation.

Loss of heterozygosity on hromosome 1 in sporadic colorectal carcinoma

AIM: Loss of heterozygosity (LOH) on tumor suppressor genes is believed to play a key role in carcinogenesis of colorectal cancer. When it occurs at a tumor suppressor gene locus with abnormal allele, neoplastic transformation happens. In this study, we analyzed the LOH at 21 loci on chromosome 1 in sporadic colorectal cancer to identify additional loci involved in colorectal tumorigenesis.METHODS: Twenty-one polymorphic micro-satellite DNA markers were analyzed with PCR both in 83 cases of colorectal cancer and in normal tissues. PCR products were eletrophoresed on an ABI 377 DNA sequencer. Genescan 3.1 and Genotype 2.1 software were used for LOH scanning and analysis. X^2 test was used to compare LOH frequency with clinicopathological data. P<0.05 was considered as statistically significant.RESULTS: The average LOH frequency of chromosome 1,short arm and long arm was 19.83%, 18.00% and 21.66%,respectively. The 2 highest LOH loci with a frequency of 36.54% and 32.50% were identified on DIS468 (1p36.33-p36.31) and DIS413 (1q31.3), respectively. On DIS2726 locus, LOH frequency of rectal cancer was 28.57% (6/21),which was higher than that of colon cancer (0.00%, 0/33) (P=0.002), suggesting that the mechanism of carcinogenisis was different in both groups.CONCLUSION: Putative tumor suppressor genes on chromosome 1 may relate to sporadic colorectal carcinomas.Tumor-suppressor-genes might locate on 1p36.33-36.31and/or 1q31.3.

Detailed deletion mapping of loss of heterozygosity on 22q13 in sporadic colorectal cancer

AIM: Both development and progression of malignancies occur as a multistep process, requiring the activation of oncogenes and the inactivation of several tumor suppressor genes. The loss of heterozygosity (LOH) of tumor suppressor genes is believed to play a key role in carcinogenesis of colorectal cancer (CRC). In this study, we analyzed the LOH of seven loci on chromosome 22q13 in an effort to identify candidate tumor suppressor genes involved in colorectal carcinogenesis. METHODS: Matched tumor and normal tissue DNA were analyzed by PCR using fluorescence-labeled polymorphic microsatellite markers in 83 CRC patients. PCR products were eletrophoresed and LOH was determined by calculating the peak height acquired through computer software. Comparisons between LOH frequency and clinicopathological features were performed by x2 test. P<0.05 was considered as statistical significance. RESULTS: The average LOH frequency of chromosome 22q13 was 28.38%. The highest LOH frequency was 64.71% on D22S1160 locus, and the lowest was 21.43% on D22S1141 locus. We detected two obvious minimal deletion regions: one between markers D22S1171 and D22S274, the other flanked by markers D22S1160 and D22S1149, each about 2.7 and 1.8 cm, respectively. None had lost in all informative loci. LOH frequency on D22S1171 is 50% on distal colon, which was higher than that on proximal one (P= 0.020); on D22S114 locus, none LOH event occurred in patients with liver metastasis, whilst 46.94% occurred in patients without liver metastasis (P= 0.008); on D22S1160 locus, LOH frequency in lymph nodes metastasis patients was 83.33%, which was much higher than 43.75% without lymph nodes metastasis ones (P= 0.016). There was no statistical significance between clinicopathological features and other loci. CONCLUSION: This study provides evidence of two minimal deletion regions, which may harbor putative tumor suppressor genes related to progression and metastasis in sporadic colorectal carcinoma on chromosome 22q13.