Abstract
A hallmark of malignant solid tumor is extracellular acidification coupled with metabolic switch to aerobic glycolysis. Using the human MCF10A progression model of breast cancer, we show that glycolytic switch and extracellular acidosis in aggressive cancer cells correlate with increased expression of tissue inhibitor of metalloproteinase-1 (TIMP-1), known to induce intracellular signal transduction through the interaction with its cell surface receptor CD63, independent of its metalloproteinase inhibitory function. We found that, in aggressive breast carcinoma, the TIMP-1-CD63 signaling axis induced a metabolic switch by upregulating the rate of aerobic glycolysis, lowering mitochondrial respiration, preventing intracellular acidification, and inducing extracellular acidosis. Carbonic anhydrase IX (CAIX), a regulator of cellular pH through the hydration of metabolically released pericellular CO(2), was identified as a downstream mediator of the TIMP-1-CD63 signaling axis responsible for extracellular acidosis. Consistently with our previous study, the TIMP-1-CD63 signaling promoted survival of breast cancer cells. Interestingly, breast carcinoma cell survival was drastically reduced upon shRNA-mediated knockdown of CAIX expression, demonstrating the significance of CAIX-regulated pH in the TIMP-1-CD63-mediated cancer cell survival. Taken together, the present study demonstrates the functional significance of TIMP-1-CD63-CAXI signaling axis in the regulation of tumor metabolism, extracellular acidosis, and survival of breast carcinoma. We propose that this axis may serve as a novel therapeutic target.