1Department of Surgery, Hallym University, Seoul, Korea. 2UCSF GI Research Lab., CA, USA.
ABSTRACT
PURPOSE: In normal tissue, MUC2 mucin gene is expressed predominantly in goblet cells, while MUC3 is expressed in both goblet cells and columnar absorptive cells of small intestine and colon. MUC5 mucin genes are expressed predominantly in the surface epithelial cells, while MUC6 is expressed mainly in the mucus neck cells of gastric glands and pyloric glands of stomach. In this paper, we determined any changes of mucin in drug-resistant cell lines from those parental cells, and we evaluated the altered regulation of mucin production in drug-resistant cells.
MATERIALS AND METHODS: In the study of 17 day postconfluent parental HT29 (HT29) and methotrexate-resistant HT29 (HT29-MTX) colon cancer cell lines were examined for the expression of MUC2, 3, 5 and 6 mucin polypeptide (apomucin) by Northern blot and slot blot analysis, and also by immunoblot analysis.
RESULTS: The level of MUC2 expression was unchanged, while there was increase in MUC3 expression in HT29-MTX compared to HT29. Interestingly there was a marked increase in the expression of MUC5 mRNA in HT29-MTX. The densitometric readings expressed as HT29-MTX/HT29 at 17th day after the cells were confluent are MUC2 (1.1), MUC3 (1.3), MUC5 (>70), MUC6 (1.0) with RNA slot blot. Immunoblot analysis was consistent with these data.
CONCLUSION: Marked induction in MUC5 but not MUC6 gastric mucin gene was found in MTX resistance in HT29 colon cancer cells. The possible biological consequences of altered regulation of mucin genes in drug resistant colon cancer cells require further investigation.
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