[Evolutive characters of oval cells in experimental hepatocarcinogenesis]

BACKGROUND & OBJECTIVE

The role of oval cells in hepatocarcinogenesis is unclear yet. This study was to explore the correlation of oval cells to hepatocarcinoma through dynamic observation on evolutive characters of oval cells in experimental hepatocarcinogenesis.

METHODS

Male SD rats were fed with 3o-me-DAB to establish an animal model of experimental hepatocarcinoma. Evolutive characters of oval cells in liver tissue during experimental hepatocarcinogenesis was dynamically observed with routine HE staining, Alcian blue staining, and immunohistochemistry.

RESULTS

Oval cells (OV-6-positive) appeared sparsely around the portal tract in the 4th week of tumor-induction. In the 8th and the 14th weeks, OV-6-positive cells were increased gradually and expanded into hepatic lobules; the hepatic tissue was divided as pseudo-lobule-like. Till the 17th and the 24th weeks, carcinoma foci were formed, meanwhile, the total amount of oval cells were decreased, and OV-6-positive cells were observed in carcinoma foci. On Alcian blue-stained preparations, two distinct histologocal types of carcinoma foci could be seen: cholangioepithelial carcinoma foci were positive and hepatocellular carcinoma foci were negative.

CONCLUSION

Oval cells, as intrahepatic stem cells, might play an important role in hepatocarcinogenesis.

Correlation of AIB1 overexpression with advanced clinical stage of human colorectal carcinoma

AIB1, a member of the steroid receptor coactivator 1 family, has been cloned on 20q12 and is a candidate oncogene in human breast cancer. It is commonly amplified and overexpressed in several types of human cancers. In this study, we examined the expression of AIB1, as related to clinicopathologic features, in 85 human colorectal cancers (CRCs). The status of the number of AIB1 copies, p53 expression, and DNA ploidy was also analyzed. The overexpression of AIB1 was detected in 35% of CRCs. Amplification of AIB1 was observed in 10% of CRCs. In addition, the overexpression of AIB1 was observed more frequently in CRCs in later clinical stages (T3 N1 M0/T3 N0 2M1), compared with that in T3 N0 M0 stage (P < .05). These results suggest that overexpression of AIB1 might provide a selective advantage for the developmental growth and/or progression of subsets of CRCs. In addition, a significant correlation (P < .05) of overexpression of AIB1 with p53 overexpression as well as with aneuploid DNA content was observed in these CRCs. The overexpression of p53 was also correlated significantly with CRC DNA ploidy (P < .05). Furthermore, there was a substantial population of CRCs showing overexpression of both AIB1 and p53 protein and all had aneuploid DNA content; most of these were in the later clinical stage. These findings suggest a possible convergence of AIB1 with a pathway involving p53, which might induce chromosomal instability and affect the clinical phenotype of a subset of CRCs.

Oncogenic role of clusterin overexpression in multistage colorectal tumorigenesis and progression

AIM: To investigate the expression pattern of clusterin in colorectal adenoma-carcinoma-metastasis series, and to explore the potential role of clusterin in multistage colorectal tumorigenesis and progression.

METHODS: A colorectal carcinoma (CRC)-tissue microarray (TMA), which contained 85 advanced CRCs including 43 cases of Dukes B, 21 of Dukes C and 21 of Dukes D tumors, were used for assessing the expression of clusterin (clone 41D) and tumor cell apoptotic index (AI) by immunohist-ochemistry and TUNEL assay, respectively. Moreover the potential correlation of clusterin expression with the patient’s clinical-pathological features were also examined.

RESULTS: The positive staining of clusterin in different colorectal tissues was primarily a cytoplasmic pattern. Cytoplasmic overexpression of clusterin was detected in none of the normal colorectal mucosa, 17% of the adenomas, 46% of the primary CRCs, and 57% of the CRC metastatic lesions. In addition, a significant positive correlation between overexpression of clusterin and advanced clinical (Dukes) stage was observed (P<0.01). Overexpression of cytoplasmic clusterin in CRCs was inversely correlated with tumor apoptotic index (P<0.01), indicating the anti-apoptotic function of cytoplasmic clusterin in CRCs.

CONCLUSION: These data suggests that overexpression of cytoplasmic clusterin might be involved in the tumorigenesis and/or progression of CRCs. The anti-apoptotic function of cytoplasmic clusterin may be responsible, at least in part, for the development and biologically aggressive behavior of CRC.

Up-regulated expression of cytoplasmic clusterin in human ovarian carcinoma

BACKGROUND

Recently, tumorigenic roles of the clusterin gene in several human malignancies have been suggested, but its potential role in the development and progression of ovarian carcinoma is unclear.

METHODS

In the current study, immunohistochemistry was used to examine the expression status of clusterin in 10 normal ovaries, 20 ovarian cystadenomas, 15 borderline ovarian tumors, and 240 ovarian carcinomas (nonmetastatic and metastatic) by tissue microarray. In addition, the apoptotic index of each tumor was assessed with a terminal deoxyuridine triphosphate nick-end labeling assay.

RESULTS

Positive staining for clusterin in different ovarian tissues was observed primarily a cytoplasmic pattern. Cytoplasmic overexpression of clusterin was detected in none of the normal ovaries, in 17% of cystadenomas, in 38% of borderline tumors, and in 58% of invasive ovarian carcinomas. A significant association was observed (P < 0.001) between the overexpression of clusterin and late clinical stage according to the International Federation of Gynecology and Obstetrics staging system. In addition, the overexpression of clusterin was detected more frequently in metastatic lesions than that in their matched primary tumors. The current results also provided evidence that the overexpression of cytoplasmic clusterin in carcinomas was correlated inversely with the tumors' apoptotic index, demonstrating an antiapoptotic function of cytoplasmic clusterin in ovarian carcinomas.

CONCLUSIONS

The current results suggested that the overexpression of cytoplasmic clusterin may represent an acquired malignant phenotypic feature of ovarian carcinoma and may be one of the important factors in determining the aggressive nature of ovarian carcinoma.

Effect of oncogenes on differentiation and transformation of rat oval cells

AIM: To study the effects of oncogenes on differentiation and transformation of oval cells by detecting and characterizing the expression of AFP and Ha-ras, c-myc genes of rat oval cells in vitro.

METHODS: Proliferation of rat oval cells was induced by chemical carcinogen, 3'-Me-DAB. By using Percoll density gradient centrifugation method, oval cells were isolated,followed by continous cultivation in vitro. The expression of Ha-ras and c-mycgenes and AFP in the oval cells from cultures was dynamically observed by RNA-DNA slot blot hybridization and flow cytometry.

RESULTS: The expression of AFP and Ha-ras, c-myc genes in the cultured oval cells from different phases was synchronous: At the beginning of oval cell cultivation in vitro, both of AFP and oncogenes displayed a higher level expression and then declined. Up to 20th passage, the expression of AFP and oncogenes went up again and then kept a lower level. To 65th passage, the oval cells not only presented a growth rate increased, population doubling time shortened, adiploid chromosomes and growing on soft agar, but also the expression of oncogenes and AFP went up again.

CONCLUSION: Oncogenes and their products participate not only in the regulation of cellular transformation, but also in the process of cell differentiation.

Heterogeneous expression and association of beta-catenin, p16 and c-myc in multistage colorectal tumorigenesis and progression detected by tissue microarray

Most colorectal carcinomas (CRCs) arise from adenomas through an archetypal pathogenic pathway, the adenoma-carcinoma-metastasis sequence. Aberrant expression of beta-catenin, p16, E-cadherin and c-myc appears to have played important roles in the development and/or progression of CRC, but their precise distribution pattern and associations in different pathologic loci along CRC's pathogenic pathway have not been thoroughly examined. In this study, a tissue microarray (TMA) containing 85 advanced CRCs in different Dukes stages was constructed. In each of 85 cases, tissue specimens from normal mucosa and primary carcinomas in different layers of the bowel wall were included in the TMA. Tissue specimens from matched adenoma, lymph node metastases and distant metastases were obtained from 22, 21 and 21 cases, respectively. Expression patterns of beta-catenin, p16, E-cadherin and c-myc were evaluated by immunohistochemistry. The results revealed that nuclear expression of beta-catenin, p16 and c-myc was quantitatively increased from normal mucosa to premalignant adenoma, primary carcinoma and lymph node metastatic carcinoma; the frequency of nuclear overexpression of beta-catenin and p16 in lymph node metastases was significantly higher than that in distant metastases (p < 0.05). These results suggest an association between nuclear overexpression of beta-catenin and/or p16 and CRC lymph node metastasis but not distant metastasis. The results also showed that correlative high nuclear expression of beta-catenin and c-myc was observed in primary carcinomas involving the serosa and lymph node metastases (p < 0.05) but not in other pathologic regions of CRCs, suggesting that the tumor microenvironment in different pathologic loci of colorectal tumorigenesis and progression may influence c-myc responsiveness to beta-catenin/Tcf activation.

Expressive characteristic and biological significance of oncogenes during rat hepatocarcinogenesis

AIM

To explore the expressive characteristic and biological significance of oncogenes during experimental hepatocarcinogenesis in rat.

METHODS

A rat model of liver carcinoma was induced with carcinogen 3-Me-DAB. The hepatic expressive characteristic of Ha-ras, c-myc and Ki-ras rats in varied stages in induction of cancer were examined with in situ hybridization and RNA slot blot hybridization.

RESULTS

The hepatic expression and distribution of Ha-ras and c-myc were similar in different periods of cancer induction. In early stage of carcinoma induction, there were more positive cells of Ha-ras and c-myc but little Ki-ras positive cells. In late stage of carcinoma induced, the number of positive cells of three oncogenes was decreased; On the 17th week of induction of cancer, the signals of three oncogenes in all the cancer nodules were negative or weak but stronger in hepatic peri-cancer tissues.

CONCLUSION

Oncogenes Ha-ras and c-myc were activated and had synergistic effect on the malignant transformation of cells in early stage of hepatocarcinogenesis. Ki-ras might be activated in late stage of hepatocarcinogenesis and associated with malignant transformation of hepatocytes.