Browsing by Subject "Cell-death"

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    Targeting LINC00152 activates cAMP/Ca²⁺/ferroptosis axis and overcomes tamoxifen resistance in ER+ breast cancer
    (Nature Publishing Group, 2024-06-15) Saatçi, Özge; Alam, Rashedul; Huynh-Dam, Kim-Tuyen; Işık, Aynur; Üner, Meral; Belder, Nevin; Ersan, Pelin Gülizar; Tokat, Ünal Metin; Ulukan, Bürge; Çetin, Metin; Çalışır, Kübra; Gedik, Mustafa Emre; Bal, Hilal; Şener Şahin, Özlem; Riazalhosseini, Yasser; Thieffry, Denis; Gautheret, Daniel; Ogretmen, Besim; Aksoy, Sercan; Üner, Ayşegül; Akyol, Aytekin; Şahin, Özgür
    Tamoxifen has been the mainstay therapy to treat early, locally advanced, and metastatic estrogen receptor-positive (ER + ) breast cancer, constituting around 75% of all cases. However, the emergence of resistance is common, necessitating the identification of novel therapeutic targets. Here, we demonstrated that long-noncoding RNA LINC00152 confers tamoxifen resistance by blocking tamoxifen-induced ferroptosis, an iron-mediated cell death. Mechanistically, inhibiting LINC00152 reduces the mRNA stability of phosphodiesterase 4D (PDE4D), leading to activation of the cAMP/PKA/CREB axis and increased expression of the TRPC1 Ca²⁺ channel. This causes cytosolic Ca²⁺ overload and generation of reactive oxygen species (ROS) that is, on the one hand, accompanied by downregulation of FTH1, a member of the iron sequestration unit, thus increasing intracellular Fe²⁺ levels; and on the other hand, inhibition of the peroxidase activity upon reduced GPX4 and xCT levels, in part by cAMP/CREB. These ultimately restore tamoxifen-dependent lipid peroxidation and ferroptotic cell death, which are reversed upon chelating Ca²⁺ or overexpressing GPX4 or xCT. Overexpressing PDE4D reverses LINC00152 inhibition-mediated tamoxifen sensitization by de-activating the cAMP/Ca²⁺/ferroptosis axis. Importantly, high LINC00152 expression is significantly correlated with high PDE4D/low ferroptosis and worse survival in multiple cohorts of tamoxifen- or tamoxifen-containing endocrine therapy-treated ER+ breast cancer patients. Overall, we identified LINC00152 inhibition as a novel mechanism of tamoxifen sensitization via restoring tamoxifen-dependent ferroptosis upon destabilizing PDE4D, increasing cAMP and Ca²⁺ levels, thus leading to ROS generation and lipid peroxidation. Our findings reveal LINC00152 and its effectors as actionable therapeutic targets to improve clinical outcome in refractory ER+ breast cancer.