| Budget Amount *help |
¥3,700,000 (Direct Cost: ¥3,700,000)
Fiscal Year 2002: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 2001: ¥300,000 (Direct Cost: ¥300,000)
Fiscal Year 2000: ¥3,000,000 (Direct Cost: ¥3,000,000)
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| Research Abstract |
We previously have reported that the putative tumor suppressor gene, APC (adenomatous polyposis coli gene), is mutated and/or deleted in primary oral squamous cell carcinomas (OSCCs). The aim of the present studywas to further examine the expression level of protein, mRNA, and also DMA methylation status on the CpG islands of the APCgene in human OSCCs. Thirty-five primary OSCCs and matched normal oral tissues were investigated by immuno-histochemical staining.A mean percentage of positivetumor cells was determined at least 5 fields at 400X magnification in each section. RT-PCR was performed using total RNAof 23 tumors to generate CDNA.These cDNAwere amplified by PCR with primers for exon1A and 2 of APC. Methylation specific PCR assay was performed in bisulfite-modified DMA samples derived from 8OSCC-derived cell lines.we have comfirmed that APCis expressed at high levels in the cytoplasm of normal oral epithelial cells. In contrast, among the tumors examined, 8 (23%) significant down-regulation of APC protein. Similar to the results of RT-PCR, reduced APC mRNA expression was detected in 13 (57%) cases. Aberrant APC methylation occurred in 3 OSCCs (38%). In addition, the CpG methylation state of E-cadhehn gene promoter in OSCCs was found in 9 (17%) of52 primary OSCCs. In particular, 8 of the 9 methylated casesshowed reduced expression of E-cadherin and histologically diffuse invasion type of tumor. Our data suggest that down-regulation of APC expression is an important event in the development of human OSCC, and that hypermethylation of the gene may be another potential mechanism for inactivation of the APC gene in oral carcinogenesis, and reduction of E-cadherin expression is associated with the progression of human OSCCs, and CpG methylation of E-cadherin gene promoter causes reduction of E-cadherin expression in the tumor, resulting in acquisition of the invasive pfenotype.
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