Abstract
Cisplatin (CDDP) is one of the principal chemotherapeutic agents used for the first-line treatment of many malignancies, including non-small cell lung carcinoma (NSCLC). Despite its use for over 40 years, its mechanism of action is not yet fully understood. Store-operated calcium entry (SOCE), the main pathway allowing Ca2+ entry in non-excitable cells, is involved in tumorogenesis, cancer progression and chemoresistance. It has become an attractive target in cancer treatment. In this study, we showed that siRNA-mediated depletion of stromal interaction molecule 1 (STIM1) and transient receptor potential channel 1 (TRPC1), two players of the store-operated calcium entry, dramatically reduced CDDP cytotoxicity in NSCLC cells. This was associated with an inhibition of the DNA damage response (DDR) triggered by CDDP. Moreover, STIM1 depletion also reduced CDDP-dependent oxidative stress. In parallel, SOCE activation induced Ca2+ entry into the mitochondria, a major source of reactive oxygen species (ROS) within the cell. This effect was highly decreased in STIM1-depleted cells. We then conclude that mitochondrial Ca2+ peak associated to the SOCE contributes to CDDP-induced ROS production, DDR and subsequent apoptosis. To the best of our knowledge, this is the first time that it is shown that Ca2+ signalling constitutes an initial step in CDDP-induced apoptosis.