Activation of the MN/CA9 gene is associated with hypomethylation in human renal cell carcinoma cell lines

The MN/CA9 (G250) gene expressed in the normal alimentary tract in a tissue‐specific manner is often activated in renal cell carcinomas. To cast light on the activation mechanism, we examined the methylation status of this gene in seven human renal cell carcinoma cell lines (SKRC‐01, ‐06, ‐10, ‐12, ‐14, ‐44, and ‐59) and three normal kidney tissue samples by using the bisulfite genomic sequencing protocol. CpG methylation was measured at seven locations in the MN/CA9 5′ region. MN/CA9 transcripts were detected by reverse transcription–polymerase chain reaction in five of the renal cell carcinoma cell lines (SKRC‐01, ‐06, ‐10, ‐44, and ‐59). These MN/CA9 positive cell lines showed hypomethylation, whereas the remaining two cell lines (SKRC‐12, and ‐14), and three normal kidney tissue samples without transcripts demonstrated hypermethylation. Treatment with the demethylating agent 5‐aza‐2′‐deoxycytidine resulted in activation of the MN/CA9 gene in the negative cell lines (SKRC‐12 and ‐14). These data suggest that hypomethylation in the 5′ region may have a major role in expression of the MN/CA9 gene in renal cell carcinoma cells. Mol. Carcinog. 27:184–189, 2000. © 2000 Wiley‐Liss, Inc.