Gastroenterology

Gastroenterology

Volume 125, Issue 3, September 2003, Pages 708-715
Gastroenterology

On the cover
Inactivating mutations of caspase-8 gene in colorectal carcinomas

https://doi.org/10.1016/S0016-5085(03)01059-XGet rights and content

Abstract

Background & Aims: There has been evidence that dysregulation of apoptosis is involved in the pathogenesis of cancer development. Caspase-8 is an initiation caspase that activates the caspase cascade during apoptosis. The aim of this study was to explore the possibility that mutation of the caspase-8 gene might be involved in the development of colorectal cancer. Methods: We analyzed the entire coding region of the caspase-8 gene for the detection of somatic mutations in 180 colorectal tumors (98 invasive carcinomas and 82 adenomas) by polymerase chain reaction, single-strand conformation polymorphism, and DNA sequencing. Results: Overall, we detected a total of 5 somatic mutations in 98 invasive carcinomas (5.1%), but no mutations were detected in 82 adenomas (0%). The frequency of caspase-8 mutation in the carcinomas was significantly higher than that in adenomas (P < 0.05). The 5 mutations consisted of 1 frameshift, 1 nonsense mutation, and 3 missense mutations. We expressed the 5 tumor-derived caspase-8 mutants and found that 3 of the 5 mutations markedly decreased apoptosis activity of caspase-8. Furthermore, expression of the inactivating caspase-8 mutants interfered with apoptosis by death receptor overexpression, indicating that these mutants have dominant-negative inhibition of the death receptor-induced apoptosis. Conclusions: The presence of caspase-8 mutation in colon carcinomas suggests that caspase-8 gene mutation might lead to the loss of its apoptotic function and contribute to the pathogenesis of colorectal carcinomas, especially at the late stage of colorectal carcinogenesis.

Section snippets

Tissue samples, microdissection, and plasmids

Paraffin-embedded histological sections of 82 colorectal adenomas (40 low-grade dysplasias and 42 high-grade dysplasias) and 98 invasive colorectal carcinomas were obtained from the Catholic University of Korea-affiliated hospitals (Seoul, Korea). The term invasive carcinoma means, strictly, a cancer that has invaded beyond the muscularis mucosa. The carcinomas originated from cecum (n = 2), ascending colon (n = 18), transverse colon (n = 6), descending colon (n = 3), sigmoid colon (n = 27),

Mutations and allelic status of the caspase-8 gene

Through the microdissection technique, we selectively procured tumor cells and normal cells from histological sections of 180 colon tumors. Genomic DNA was isolated and analyzed for the potential mutations in the coding region of the caspase-8 gene by PCR-SSCP analysis. Enrichment and direct DNA sequence analysis of aberrantly migrating bands led to the identification of 5 mutations in 98 invasive carcinomas (5.1%) (Table 1; Figure 1) but none in 82 adenomas (0%). None of the corresponding

Discussion

The aim of this study was to address whether human colon carcinoma has caspase-8 gene mutation. If so, the next aim was to address whether these mutations inactivated the proapoptotic activity of caspase-8. We found that in colon carcinoma, but not in colon adenoma, the caspase-8 gene is somatically mutated. Moreover, the functional study showed that the cancer-derived caspase-8 mutants showed losses of apoptotic function. These data, together with the earlier reports on the inactivating

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    Supported by funding from the Molecular Medicine Research Group program from the Ministry of Science and Technology of Korea (Grant M10106000075-02B1700-01810) and by funds from POSCO (Grant 20027045).

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