Amplified Ca2+ dynamics and accelerated cell proliferation in breast cancer tissue during purinergic stimulation. Issue 7 (17th June 2022) - Henningsen, Mikkel B.
Abstract: Intracellular Ca 2+ dynamics shape malignant behaviors of cancer cells. Whereas previous studies focused on cultured cancer cells, we here used breast organoids and colonic crypts freshly isolated from human and murine surgical biopsies. We performed fluorescence microscopy to evaluate intracellular Ca 2+ concentrations in breast and colon cancer tissue with preferential focus on intracellular Ca 2+ release in response to purinergic and cholinergic stimuli. Inhibition of the sarco‐/endoplasmic reticulum Ca 2+ ATPase with cyclopiazonic acid elicited larger Ca 2+ responses in breast cancer tissue, but not in colon cancer tissue, relative to respective normal tissue. The resting intracellular Ca 2+ concentration was elevated, and ATP, UTP and acetylcholine induced strongly augmented intracellular Ca 2+ responses in breast cancer tissue compared with normal breast tissue. In contrast, resting intracellular Ca 2+ levels and acetylcholine‐induced increases in intracellular Ca 2+ concentrations were unaffected and ATP‐ and UTP‐induced Ca 2+ responses were smaller in colon cancer tissue compared with normal colon tissue. In accordance with the amplified Ca 2+ responses, ATP and UTP substantially increased proliferative activity—evaluated by bromodeoxyuridine incorporation—in breast cancer tissue, whereas the effect was minimal in normal breast tissue. ATP caused cell death—identified with ethidium homodimer‐1 staining—in breast cancer tissue only at concentrations above the expected pathophysiological range. We conclude that intracellular Ca 2+ responses are amplified in breast cancer tissue, but not in colon cancer tissue, and that nucleotide signaling stimulates breast cancer cell proliferation within the extracellular concentration range typical for solid cancer tissue. Abstract : What's new? Molecular mechanisms influencing intracellular Ca 2+ dynamics are deregulated in cancer cell lines. However, many implications of deregulated Ca 2+ signaling during carcinogenesis remain unclear. Using fresh human and murine tissue biopsies, here the authors show that resting intracellular Ca 2+ levels, organellar Ca 2+ storage and intracellular Ca 2+ responses to nucleotides and cholinergic stimuli are elevated during breast, but not colon, carcinogenesis. Nucleotides stimulate proliferation in breast cancer tissue within the elevated nucleotide concentration range observed in the tumor microenvironment, whereas cell death is induced only at higher concentrations. The authors propose that amplified Ca 2+ signals facilitate breast malignancy.