Study of in vitro conditions modulating expression of MN/CA IX protein in human cell lines derived from cervical carcinoma

: In an effort to better understand the biological significance of MN/CA IX human tumor-associated protein, we have investigated its expression in human cervical carcinoma cell lines in vitro. SiHa cells that naturally express MN/CA IX were used as a model for expression study at the protein level. In addition, we have transfected MN/CA9 gene-negative but transcription-competent C33A cells with a plasmid carrying CAT reporter gene under a control of MN/CA9 promoter. By this way, we have generated a stable cell line C33A/MNP-CAT that was employed in analysis of MN/CA9 regulation at the level of promoter activity as estimated by CAT protein abundance. For the purpose of our study, we have chosen experimental conditions relevant to growth characteristics and phenotypic features of malignantly transformed cells. Both the level of MN/CA IX protein and the gene promoter activity were found to be substantially elevated either in culture of high density or when the adherent carcinoma cells grew in suspension, but were not markedly affected by diminished serum concentration and in the cell cycle progression. These observations support the involvement of MN/CA IX protein in aberrant cell-cell and cell-matrix interactions that facilitate loss of contact inhibition and anchorage independence of cancer cells.