ER-phagy mediates the anti-tumoral synergism between HDAC inhibition and chemotherapy
摘要
Histone deacetylase inhibitors (HDACi) are clinically approved drugs for the treatment of hematological malignancies synergizing with chemotherapy. However, despite the long history of HDACi, the mechanistic underpinnings of this synergism have remained unclear.
MethodsUsing transmission electron microscopy, we identified autophagy and ER-stress in HDACi-treated cells. We quantified ER-phagy and ER-stress with reporter systems by using 3D-deconvolution microscopy and flow cytometry. We complemented these data with qPCR and Western blot results. Apoptosis rates were assessed using a caspase assay and flow cytometry, and large public datasets were utilized.
ResultsHDAC blockade results in specific upregulation of the selective autophagy receptor FAM134B (RETREG1) and the induction of ER-phagy. Combined with the chemotherapeutic drug Gemcitabine, this results in subsequent elevated ER-stress levels and apoptosis. Inhibiting the distinct ER-stress branches fully rescues this process. Broadening the scope of these findings, certain non-HDAC-inhibitory and clinically approved compounds like Loperamide and Nelfinavir are able to induce FAM134B and could hence constitute novel Gemcitabine-synergizing molecules. Additionally, pancreatic cancer patients with high FAM134B expression have significantly longer survival rates under chemotherapy.
ConclusionIn summary, we provide mechanistic evidence for ER-phagy playing a hitherto unknown central role in the clinical synergy between HDACi and chemotherapy.