Elevation of Cytoplasmic Calcium Suppresses Microtentacle Formation and Function in Breast Tumor Cells

Katarina T Chang; Keyata N Thompson; Stephen J P Pratt; Julia A Ju; Rachel M Lee; Trevor J Mathias; Makenzy L Mull; David A Annis; Eleanor C Ory; Megan B Stemberger; Michele I Vitolo; Stuart S Martin

doi:10.3390/cancers15030884

Elevation of Cytoplasmic Calcium Suppresses Microtentacle Formation and Function in Breast Tumor Cells

Cancers (Basel). 2023 Jan 31;15(3):884. doi: 10.3390/cancers15030884.

Authors

Katarina T Chang^{1

2}, Keyata N Thompson², Stephen J P Pratt^{2

3}, Julia A Ju^{1

2}, Rachel M Lee², Trevor J Mathias^{1

2}, Makenzy L Mull^{1

2}, David A Annis^{2

4}, Eleanor C Ory², Megan B Stemberger^{2

3}, Michele I Vitolo^{2

5}, Stuart S Martin^{2

5

6}

Affiliations

¹ Graduate Program in Molecular Medicine, University of Maryland School of Medicine, 800 W. Baltimore St., Baltimore, MD 21201, USA.
² Marlene and Stewart Greenebaum NCI Comprehensive Cancer Center, University of Maryland School of Medicine, 655 W. Baltimore St., Baltimore, MD 21201, USA.
³ Graduate Program in Biochemistry & Molecular Biology, University of Maryland School of Medicine, 108 N. Greene St., Baltimore, MD 21201, USA.
⁴ Graduate Program in Epidemiology and Human Genetics, University of Maryland School of Medicine, 800 W. Baltimore St., Baltimore, MD 21201, USA.
⁵ Department of Pharmacology and Physiology, University of Maryland School of Medicine, 655 W. Baltimore St., Baltimore, MD 21201, USA.
⁶ United States Department of Veterans Affairs, VA Maryland Health Care System, Baltimore, MD 21201, USA.

Abstract

Cytoskeletal remodeling in circulating tumor cells (CTCs) facilitates metastatic spread. Previous oncology studies examine sustained aberrant calcium (Ca²⁺) signaling and cytoskeletal remodeling scrutinizing long-term phenotypes such as tumorigenesis and metastasis. The significance of acute Ca²⁺ signaling in tumor cells that occur within seconds to minutes is overlooked. This study investigates rapid cytoplasmic Ca²⁺ elevation in suspended cells on actin and tubulin cytoskeletal rearrangements and the metastatic microtentacle (McTN) phenotype. The compounds Ionomycin and Thapsigargin acutely increase cytoplasmic Ca²⁺, suppressing McTNs in the metastatic breast cancer cell lines MDA-MB-231 and MDA-MB-436. Functional decreases in McTN-mediated reattachment and cell clustering during the first 24 h of treatment are not attributed to cytotoxicity. Rapid cytoplasmic Ca²⁺ elevation was correlated to Ca²⁺-induced actin cortex contraction and rearrangement via myosin light chain 2 and cofilin activity, while the inhibition of actin polymerization with Latrunculin A reversed Ca²⁺-mediated McTN suppression. Preclinical and phase 1 and 2 clinical trial data have established Thapsigargin derivatives as cytotoxic anticancer agents. The results from this study suggest an alternative molecular mechanism by which these compounds act, and proof-of-principle Ca²⁺-modulating compounds can rapidly induce morphological changes in free-floating tumor cells to reduce metastatic phenotypes.

Keywords: Ionomycin (Iono); Thapsigargin (Tg); breast cancer; calcium (Ca2+); metastasis; microtentacle (McTN).

Abstract

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