Quantification of caveolin isoforms using quantitative real-time RT-PCR, and analysis of promoter CpG methylation of caveolin-1α in human T cell leukemia cell lines

Caveolin-1, an essential structural component of caveolae, functions as a negative regulator for signal transduction and has been suggested to be a candidate tumor suppressor. Lack of caveolin-1 expression has been implicated in the pathogenesis of oncogenic cell transformation and tumorigenesis in many cancers. On the other hand, over-expression has also been associated with tumor progression and metastasis in prostate cancers. Hence, alteration of caveolin-1 expression has been proposed as a clinical marker for diagnosis and prognosis in various cancers. For precise analyses of the caveolin expression in human T cell leukemia cell lines, we measured the mRNA levels of caveolin isoforms, caveolin-1α, -1β, -2, and -3 with real-time RT-PCR using external standards for each isoform. In the panel of human T cell leukemia cell lines tested, four cell lines expressed caveolin-1α, -1β and -2, but not -3, which was consistent with the protein levels. The expression profiles in most cell lines are caveolin-1α > caveolin-1β > caveolin-2. Two cell lines did not express either of the caveolin mRNAs. Methylation analyses for the CpG sites in the promoter region of a positive and a negative cell line did not show a clear correlation with the expression status, suggesting that mechanisms other than CpG methylation are involved in the regulation of caveolin-1α expression in human T cell leukemia cell lines.