STIM1-dependent Ca²⁺ signaling regulates podosome formation to facilitate cancer cell invasion

The clinical significance of STIM proteins and Orai Ca²⁺ channels in tumor progression has been demonstrated in different types of cancers. Podosomes are dynamic actin-rich cellular protrusions that facilitate cancer cell invasiveness by degrading extracellular matrix. Whether STIM1-dependent Ca²⁺ signaling facilitates cancer cell invasion through affecting podosome formation remains unclear. Here we show that the invasive fronts of cancer tissues overexpress STIM1, accompanied by active store-operated Ca²⁺ entry (SOCE). Interfering SOCE activity by SOCE inhibitors and STIM1 or Orai1 knockdown remarkably affects podosome rosettes formation. Mechanistically, STIM1-silencing significantly alters the podosome rosettes dynamics, shortens the maintenance phase of podosome rosettes and reduces cell invasiveness. The subsequently transient expression of STIM1 cDNA in STIM1-null (STIM1^-/-) mouse embryo fibroblasts rescues the suppression of podosome formation, suggesting that STIM1-mediated SOCE activation directly regulates podosome formation. This study uncovers SOCE-mediated Ca²⁺ microdomain that is the molecular basis for Ca²⁺ sensitivity controlling podosome formation.