ABSTRACT
The goal of this study was to define Na,K-ATPase α and ß subunit isoform expression and isozyme composition in colorectal cancer cells and liver metastases. The α1, α3, and ß1 isoforms were the most highly expressed in tumor cells and metastases; in the plasma membrane of non-neoplastic cells and mainly in a cytoplasmic location in tumor cells. α1ß1 and α3ß1 isozymes found in tumor and metastatic cells exhibit the highest and lowest Na(+) affinity respectively and the highest K(+) affinity. Mesenchymal cell isozymes possess an intermediate Na(+) affinity and a low K(+) affinity. In cancer, these ions are likely to favor optimal conditions for the function of nuclear enzymes involved in mitosis, especially a high intra-nuclear K(+) concentration. A major and striking finding of this study was that in liver, metastasized CRC cells express the α3ß1 isozyme. Thus, the α3ß1 isozyme could potentially serve as a novel exploratory biomarker of CRC metastatic cells in liver.
