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  • Title: Expression of transcription factor AP-2 in colorectal adenomas and adenocarcinomas; comparison of immunohistochemistry and in situ hybridisation.
    Author: Ropponen KM, Kellokoski JK, Pirinen RT, Moisio KI, Eskelinen MJ, Alhava EM, Kosma VM.
    Journal: J Clin Pathol; 2001 Jul; 54(7):533-8. PubMed ID: 11429425.
    Abstract:
    AIMS: To investigate whether the three different AP-2 isoforms are expressed differently in colorectal adenomas and carcinomas. METHODS: The study comprised 43 randomly selected patients diagnosed and treated at Kuopio University Hospital in 1996 for colorectal adenocarcinoma (n = 30) and colorectal adenoma (n = 13). The expression of AP-2alpha, AP-2beta, and AP-2gamma was analysed by immunohistochemistry (IHC) and the mRNA status of AP-2alpha was determined by in situ hybridisation (ISH) and confirmed by reverse transcription polymerase chain reaction (RT-PCR). AP-2 expression patterns were correlated with clinicopathological variables. RESULTS: In adenomas and carcinomas, AP-2beta cytoplasmic positivity was higher than that of AP-2alpha or AP-2gamma. AP-2alpha expression was reduced in advanced Dukes's stage carcinomas. In high grade carcinomas, both AP-2alpha and AP-2gamma expression was reduced. ISH demonstrated increased AP-2alpha values in high grade carcinomas. Seven of 30 carcinoma specimens displayed a moderate or strong mRNA signal, despite being negative for AP-2alpha protein. RT-PCR from AP-2alpha mRNA and protein positive tumours confirmed that the positive signal in ISH originated from the exon 2 of TFAP2A. CONCLUSIONS: AP-2alpha was reduced in advanced Dukes's stage adenocarcinomas. Together with reduced AP-2gamma expression in high grade carcinomas, this might contribute to tumour progression. The discrepancy between mRNA and protein expression suggests that post-transcriptional regulatory mechanisms might modify the availability of functional AP-2alpha protein in colorectal carcinoma.
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