p53 accumulation in colorectal cancer with hepatic metastasis

Chromosomal Numerical Abnormality Profiles of Gastrointestinal Stromal Tumors

BACKGROUND

Biological variations in and the heterogeneity of gastrointestinal stromal tumors (GISTs) are well known, but chromosomal numerical abnormality (CNA) has not been fully examined especially in this context. The aim of this study is to test CNA as a possible biological predictor of biological behavior of GISTs.

METHOD

We applied microwave-assisted FISH protocol to pathological archives of GIST tumors displaying different clinical features to characterize the CNA profile of these tumors. A panel of 18 centromere enumeration probes (CEP) and 24 bacterial artificial chromosome (BAC) or P1-derived artificial chromosome (PAC) probes containing genes like Aurora kinases (AURKs) and other candidate genes involved in human carcinogenesis were used. CNA profiles, histopathological risk categorization and Ki-67 labeling indexes of 23 primary and/or metastatic GIST tumors of 12 subjects (both primary and metastatic in 7 subjects) were compared between primary GIST with and without metastases, and between metastatic and primary portions in 7 individuals.

RESULTS

CNA in the primary sites was more extensive in the GISTs with recurrence and metastasis than in those without, especially as to the loss of chromosome 20 and genomic imbalance of AURKA-containing BAC probe on 20q in the cases with metastasis. The consistent loss of one allele of chromosome 14q was also noted. Interestingly, both primary and metastatic tumors in identical individuals had similar CNA profiles.

CONCLUSION

The extent of CNA differed between GISTS with and without recurrence or metastasis; thus, FISH analysis of specimens from the primary sites may predict the biological behavior of this tumor.

Orthotopic implantation of a colon cancer xenograft induces high expression of cyclooxygenase-2

The aim of the present study is to investigate the relation of cyclooxygenase (COX)-2 with liver metastasis. Pieces of human colon cancer xenograft were implanted orthotopically (CI), as well as intraperitoneally, and subcutaneously. Liver metastasis developed most frequently, and the COX-2 expression of both mRNA and protein of the tumors was the most dominant in the CI group. In contrast, the expression of COX-1 or vascular endothelial cell growth factor mRNAs had no significant differences among the groups. The intensity of COX-2 mRNA was negatively correlated with the apoptotic index. In conclusion, COX-2 plays an important role in organ-specific metastasis of the colon cancer.

Single alteration of p53 or E-cadherin genes can alter the surgical resection benefit in an experimental model of colon cancer

PURPOSE

p53 and E-cadherin mutations are associated with a high risk of metastatic potential and local recurrence after colorectal surgery. LoVo, a human colon cancer cell line expressing a wild-type p53 and a normal E-cadherin, was studied. Clone LoVo-XC17 was obtained from LoVo cells transfected with a vector bearing a p53 273his mutation. Clone LoVo-92R4 was obtained from LoVo by culture cells with an E-cadherin down-regulation. LoVo, LoVo-XC17, and LoVo-92R4 were studied for in vivo behavior in a surgical intracolonic graft model.

METHODS

Ten nude mice were used per cell line. A colonic tumor was obtained by tumor implantation into the cecal wall. The cecal tumor was resected at Day 15; at this time the volumes of the different tumors were similar.

RESULTS

Surgical resection of the LoVo tumor led to 100 percent disease-free animals at one month. Surgical resection of mice grafted with the LoVo-XC17 line did not cure any mice (0/10; P = 0.001). Mice had local recurrences (10/10), mesenteric lymph node metastases (9/10), liver metastases (2/10), and peritoneal carcinomatosis (8/10). Surgical resection of LoVo-92R4 tumors led to cures in 30 percent (3/10), whereas 70 percent had isolated mesenteric lymph node metastases (7/10; P = 0.003).

CONCLUSION

In this model surgical tumor resection was consistently effective for colonic tumors with functional p53 and E-cadherin, it was consistently ineffective with tumors displaying a mutated p53, and it was partially effective with E-cadherin-deficient tumors. This study shows that the alteration of a single gene can be associated with a profound alteration of surgical resection benefit.

Heterogeneity of p53 mutational status in intramucosal carcinoma of the colorectum

The aim of this study was to elucidate whether or not p53 genetic heterogeneity would occur while colorectal carcinoma was limited to the mucosa. Eight cases of endoscopically resected colorectal intramucosal carcinomas were analyzed to determine the p53 gene sequence (exons 5 to 8). Six out of 8 cases showed p53 gene mutations, and in all of them, the mutational status was heterogeneous. In 4 cases, mutated codons were heterogeneous as well. These data indicate that p53 gene alterations in colorectal carcinomas occur and diverge at the stage of intramucosal carcinoma, supporting our previously proposed hypothesis that colorectal carcinomas can be composed of various subclones as regards p53 gene mutation, while the carcinoma is limited to the mucosa, and one of these subclones commences invasion to the submucosa after clonal selection, thus generating a monoclonal invasive carcinoma.

Proliferation of hepatic metastases of colorectal carcinoma: relationship to primary tumours and prognosis after hepatic resection

In this study, we determined the proliferation indices of liver metastatic tumours originating from colorectal carcinomas using Ki67 and argyrophil nucleolar organizer region associated proteins (AgNOR) stain. We examined the primary and metastatic tumours in 27 patients with liver metastasis and eight cases with non-metastatic colorectal carcinoma as a control.The number of AgNOR dots in metastatic tumours was significantly higher than in the respective primary tumours of the metastasis group or in non-metastatic colorectal carcinomas. The Ki67 labelling index was similar in all groups. The Ki67 labelling index and AgNOR counts did not correlate with each other. There was no significant relationship between proliferation indices and the duration of the disease-free period following hepatic resection for metastases or with prognosis after hepatectomy. We conclude that Ki67 and AgNOR are not useful indicators of prognosis in patients who undergo operation for liver metastasis of colorectal carcinomas.

p53 exon 7 mutations as a predictor of poor prognosis in patients with colorectal cancer

We have studied 61 resected colorectal adenocarcinomas in order to investigate p53 mutations as a prognostic factor for this pathology. Mutations in exons 5-9 of the p53 gene were analyzed by the polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) technique followed by sequencing. Our data indicate that p53 exon 7 mutations were prevalent in the latest stages of colorectal carcinogenesis and patients bearing this alteration had the worst prognosis. Therefore, according to our results, mutations affecting exon 7 of the p53 gene could be considered as a useful marker of biological aggressiveness for colorectal cancer.

Immunophenotyping of human HT29 colon cancer cell primary tumours and their metastases in severe combined immunodeficient mice

The immunophenotype of HT29 human colon cancer cells implanted into severe combined immunodeficient mice was assessed in primary tumours and their metastases in the lungs using an indirect immunohistochemical method. After primary tumours were surgically removed, the metastases were given time to develop, thus paralleling the clinical situation. While vimentin was negative in both primary and secondary tumours, E-cadherin was present as membrane-bound labelling in the primary tumours only. Whereas the markers p53, MIB1, PCNA and CEA were consistently positive in both primary and metastatic tumours, CD44 variant 6 and CA125 were negative in metastases but positive in the primary tumours. There was a significant increase in the percentage of cells labelled for p53 in the primary tumours compared with the metastases. For the proliferation markers, there was no significant difference in labelling between primary tumours and metastases for MIB1. Of the cytokeratins examined, CK 20 gave the strongest and most consistent reaction in both primary and secondary tumours. The results indicate that, for certain immunohistochemical markers, results are the same in both primary tumours and metastases. Hence, in these cases, antigens that are expressed on the primary tumour as well as on the metastases can serve as target molecules for immunologically based forms of treatment of metastases.