Down-regulation of tyrosine aminotransferase at a frequently deleted region 16q22 contributes to the pathogenesis of hepatocellular carcinoma.

UNLABELLED: Loss of 16q is one of the most frequent alterations in many malignancies including hepatocellular carcinomas (HCC), suggesting the existence of a tumor suppressor gene (TSG) within the frequently deleted region. In this report we describe the identification and characterization of one candidate TSG, tyrosine aminotransferase gene (TAT), at 16q22.1. Loss of one TAT allele was detected in 27/50 (54%) of primary HCCs by quantitative real-time polymerase chain reaction. In addition, homo-deletion of TAT alleles was detected in two cases. Down-regulation of TAT was detected in 28/50 (56%) of HCCs, which was significantly associated with the loss of TAT allele and hypermethylation of TAT 5' CpG island (CGI) region (P < 0.001). Functional studies found that TAT has a strong tumor suppressive ability. Introduction of the TAT gene into HCC cell lines could effectively inhibit colony formation in soft agar, foci formation, and tumor formation in nude mice. Further study found that the tumor suppressive mechanism of TAT was associated with its proapoptotic role in a mitochondrial-dependent manner by promoting cytochrome-c release and activating caspase-9 and PARP. CONCLUSION: Taken together, our findings suggest that TAT plays an important suppressive role in the development and progression of HCC.

1p31, 7q21 and 18q21 chromosomal aberrations and candidate genes in acquired vinblastine resistance of human cervical carcinoma KB cells.

Vinblastine (VBL) is used to treat certain kinds of cancer including Hodgkin's lymphoma, lung cancer, breast cancer, testicular cancer and cervical carcinoma. However, the rapid development of resistance during therapy remains a major clinical challenge. In order to reverse cancer cell resistance, the goal of this study was to find differentially expressed genes and chromosomal alterations in multidrug resistant (MDR) KB-v1 cells, further to probe the relationship between drug resistance and differential genes, and chromosomal changes in MDR cancer cells. Comparative genomic hybridization (CGH) analysis of MDR KB-v1 and their parental KB-3-1 cells revealed chromosomal changes; microarray-based expression profiling was carried out by comparing the gene expressions of MDR KB-v1 cells and KB-3-1 cells. We have identified 3 chromosomal gains in regions of 1p31, 7q21 and 18q21 in MDR cells and 10 genes (CYR61, UGTREL7, MBD1, NARS, ATP5A1, ABCB1, ABCB4, PEG10, MCM7, SERPINE1) contained in these regions were also up-regulated in MDR KB-v1 cells. Forty-nine genes were down-regulated when KB-v1 cells were subjected to lower dose or depletion of the drug. We have confirmed some gene expression changes by reverse transcription-polymerase chain reaction and Northern blots. These are the first data describing the relationship of 1p31 and 18q21 chromosomal aberrations and candidate genes in acquired vinblastine-resistance. This study also demonstrates that the combination of CGH and cDNA microarray is a very useful tool to detect drug resistant targets in cancer treatment.

Amplification and overexpression of epidermal growth factor receptor gene in glioblastomas of Chinese patients correlates with patient's age but not with tumor's clinicopathological pathway.

It is believed that there are two distinct pathological pathways leading to the development of human glioblastomas (GBM) in Caucasian populations. Primary (de novo) GBM most often occurs in older individuals, and is characterized by the overexpression/amplification of epidermal growth factor receptor gene (EGFR), whereas secondary GBM, which progresses from a low-grade astrocytoma, often affects younger individuals and frequently contains the TP53 mutation. We and others have previously found that the age of onset of GBM in Chinese patients tends to be younger than that in Caucasian patients. To identify whether GBMs from Chinese patients share this common pattern of genetic alterations, expression levels of EGFR and TP53 and TP53 mutation were analyzed in 56 randomly selected Chinese GBMs (30 primary and 26 secondary), including 47 adult-onset and 9 pediatric GBMs. Consistent with other studies, overexpression/mutation of TP53 and aneuploid DNA content were more frequently detected in secondary GBMs of Chinese adult patients. In contrast to that observed in Caucasian patients, no significant difference was observed in the age distribution and the frequency of EGFR overexpression/amplification between primary and secondary GBMs in adult Chinese patients. Furthermore, the overexpression of EGFR was much higher in late-onset (age >45 years) GBMs (73%) than that in both early-onset (age 18-45 years) (17%) and pediatric (age <18 years) GBMs (11%), suggesting that overexpression of EGFR in Chinese GBMs may be associated closely with the patients age but not with the tumors' pathological pathway.

Oncogenic role of eIF-5A2 in the development of ovarian cancer.

Amplification of 3q26 is one of the most frequent chromosomal alterations in many solid tumors, including ovarian, lung, esophageal, prostate, breast, and nasopharyngeal cancers. A candidate oncogene to eukaryotic initiation factor 5A2 (eIF-5A2), a member of eukaryotic initiation factor 5A subfamily, has been isolated from a frequently amplified region at 3q26.2. In this work, the tumorigenic ability of eIF-5A2 was demonstrated by anchorage-independent growth in soft agar and tumor formation in nude mice. Furthermore, antisense DNA against eIF-5A2 could inhibit cell growth in ovarian cancer cell line UACC-1598 with amplification of eIF-5A2 in form of double minutes. Cell growth rate in UACC-1598 was also inhibited when the expression level of EIF-5A2 was decreased by the reduction of the copy number of double minutes. The correlation of EIF-5A2 overexpression and clinical features of ovarian cancer was investigated using tissue microarray, and the result showed that eIF-5A2 overexpression was significantly associated with the advanced stage of ovarian cancer. These findings suggest that eIF-5A2 plays important roles in ovarian pathogenesis.

Evidence for another tumor suppressor gene at 17p13.3 distal to TP53 in hepatocellular carcinoma.

Loss of 17p is one of the most frequent chromosomal alterations in primary hepatocellular carcinoma (HCC). In the present study, the association between loss of 17p and TP53 mutation was analyzed in 94 primary HCC of Chinese patients. Loss of one allele at 17p13.3 distal to the TP53 gene was observed in 48 of 94 HCC (51%), whereas loss of heterozygosity (LOH) at 17p13.1 near the TP53 gene was detected in 30 of 94 HCC (32%) and TP53 mutation was detected in only 22 of 94 HCC (23%). High frequency of LOH at 17p13.3 and relatively low frequency of TP53 mutation in the present study indicate that loss of function of a putative tumor suppressor gene at 17p13.3 may play a more important role than TP53 in HCC development.

Different expression of hepatitis B surface antigen between hepatocellular carcinoma and its surrounding liver tissue, studied using a tissue microarray.

Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide and is highly associated with chronic liver disease, including hepatitis B viral infection. In order to study the association between hepatitis B virus (HBV) infection and HCC development, tissue microarrays were used to detect the expression of hepatitis B surface antigen (HBsAg) in 194 HCCs and their surrounding liver tissues, using anti-HBsAg monoclonal antibody. The results showed that the expression of HBsAg is significantly lower in tumour tissue than in non-tumour tissue. Among the 138 cases with positive serum HBsAg, expression of HBsAg was more frequently detected in non-tumour tissue (103 cases, 75%) than in tumour tissue (11 cases, 8%). RT-PCR and Southern blot analysis were performed to explore the mechanism of the decreased expression of HBsAg in tumour cells. The RT-PCR results showed that absence or decreased expression of the HBV S gene was detected in 3/15 (20%) and 6/15 (40%) HCCs, respectively. Integration of HBV in 23 pairs of HCCs and their matched non-tumour liver tissues was studied by Southern blot. The results showed that the integrated HBV S gene sequence was detected in 19/23 tumours (83%) and 1/23 non-tumour tissues (4%), whereas the free replicative virus form was observed in 3/23 tumours (13%) and 14/23 non-tumour tissues (61%). These findings suggest that HBsAg-negative results in tumour tissues were directly related to HBV DNA insertion and provide new insights into the involvement of HBsAg in hepatocarcinogenesis.

Identify metastasis-associated genes in hepatocellular carcinoma through clonality delineation for multinodular tumor.

Disease recurrence and metastasis are frequently observed in many successfullytreated localized cancers, including hepatocellular carcinoma in which intrahepatic and extrahepatic recurrence (metastasis) are frequently observed after curative resection. The present study aimed at identifying metastasis-associated genes through delineation of the clonality for multinodular liver cancer. The clonal relationship of 22 tumor foci from six patients was investigated by the genome-wide expression profile via cDNA microarray consisting of 23,000 genes. Tumor molecular properties including p53 protein overexpression and gene mutation, hepatitis B virus integration pattern, and genetic alteration examined by comparative genomic hybridization were compared. Results indicated that gene expression patterns could serve as the molecular fingerprint for clonality identification. Together with the molecular data from p53, hepatitis B virus integration and comparative genomic hybridization profiles, tumor nodules from five patients were confirmed with clonal relationship, and the expression profiles of the primary nodules were compared with their corresponding intrahepatic metastatic nodules. A total of 90 clones were found to be correlated with intrahepatic metastasis by Student's t test (P < 0.05). With reference to the primary tumor, 63 clones (39 known genes and 24 express sequence tags) were down-regulated whereas 27 clones (14 known genes and 13 express sequence tags) were up-regulated in the metastatic nodules. These metastasis-associated genes may provide clues to reveal patients with increased risk of developing metastasis, and to identify novel therapeutic targets for the treatment of metastasis.