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

Area of Science:

• Cell Biology
• Oncology
• Biochemistry

Background:

• Circulating tumor cells (CTCs) use cytoskeletal remodeling for metastasis.
• Sustained calcium (Ca²⁺) signaling is linked to cancer, but rapid Ca²⁺ effects are understudied.
• Microtentacles (McTNs) are cell surface protrusions involved in CTC adhesion and metastasis.

Purpose of the Study:

• Investigate the impact of acute cytoplasmic Ca²⁺ elevation on cytoskeletal rearrangements and McTN phenotype in suspended tumor cells.
• Determine if Ca²⁺ modulation can reduce the metastatic potential of breast cancer cells.
• Explore the molecular mechanisms linking Ca²⁺ signaling to cytoskeletal dynamics and McTN formation.

Main Methods:

• Utilized breast cancer cell lines (MDA-MB-231, MDA-MB-436).
• Administered Ca²⁺-elevating agents (Ionomycin, Thapsigargin) and actin polymerization inhibitor (Latrunculin A).
• Assessed McTN formation, cell reattachment, clustering, and cytotoxicity.
• Analyzed actin and tubulin rearrangements, myosin light chain 2, and cofilin activity.

Main Results:

• Acute Ca²⁺ elevation by Ionomycin and Thapsigargin suppressed McTNs in MDA-MB-231 and MDA-MB-436 cells.
• Reduced cell reattachment and clustering were observed within 24 hours, without cytotoxicity.
• Ca²⁺-induced actin cortex contraction and rearrangement were linked to myosin light chain 2 and cofilin.
• Inhibition of actin polymerization reversed Ca²⁺-mediated McTN suppression.

Conclusions:

• Rapid Ca²⁺ signaling can rapidly alter CTC morphology and reduce metastatic phenotypes.
• Ca²⁺-modulating compounds may offer a novel approach to target cancer metastasis.
• This study reveals an alternative mechanism for Thapsigargin derivatives beyond cytotoxicity.