Plasma membrane calcium ATPase 4 and the remodeling of calcium homeostasis in human colon cancer cells

A remodeling of calcium homeostasis has been identified as a characterizing feature of some cancers. Possible consequences of this include alterations in many pivotal physiological responses including apoptosis, proliferation and gene transcription. An alteration in calcium homeostasis can occur via changes in the expression of proteins that transport calcium and examples of cancers where this is seen includes the prostate and breast. A specific isoform of the calcium efflux pump, plasma membrane Ca2+-ATPase (PMCA) 4, is significantly upregulated during differentiation of the HT-29 colon cancer cell line suggesting that it may also be altered in colon cancer. We now report that differentiated HT-29 colon cancer cells have pronounced plasma membrane PMCA4 localization, consistent with augmented calcium efflux. Assessment of PMCA4 transcription in human colon cancer samples suggests that PMCA4 is significantly (P