Abstract 2619: DNA damage agents promote TFEB function and induce pro-survival autophagy signals

The transcription factor EB (TFEB) was identified as a master regulator of autophagy and lysosomal biogenesis. We recently demonstrated that TFEB is aberrantly regulated in pancreatic cancer (PDAC) cells. Interference with TFEB impairs PDAC cell growth supporting an important role for TFEB in maintaining PDAC cell phenotype. Given the limited impact of chemotherapeutic drugs in the context of PDAC, we aimed at testing whether the aberrantly regulated TFEB in PDAC cells could confer resistance to DNA damage agents, commonly used in PDAC therapeutic regimens. Methods: Experiments were performed in PDAC cells (MIA PaCa2, PANC1). The DNA damage agents gemcitabine, 5-FU, cisplatin and doxorubicin were used. Autophagic flux was measured upon 4-hours treatment with bafilomycin A1. Results: Treatment with DNA damage agents 1) increased the autophagic flux in PDAC cells. This autophagic signal was associated with 2) the dephosphorylation and nuclear accumulation of TFEB. The mTORC1 pathway is well-known to regulate TFEB phosphorylation and nuclear localization of TFEB. 3) However, the impact of the DNA damage agents on TFEB appeared independent of the mTORC1 pathway since no modulation in the phosphorylation of the mTORC1 target S6K1 was observed. To delineate whether TFEB influenced the response to DNA damage agents, we generated stable populations of PDAC cells expressing a non-targeting or shRNA targeting TFEB. Interfering with TFEB function 4) prevented the autophagic response upon treatment with DNA damage agents. This correlated with 5) increased accumulation of DNA damage and 6) increased sensitivity to the DNA damage agents. Conclusion: Our results suggest that DNA damage agents can induce a pro-survival autophagic response involving TFEB. Interfering with TFEB function limits the autophagic response and leads to increased sensitivity to DNA damage agents. Altogether, our results suggest that the aberrantly expressed TFEB in PDAC cells could confer resistance to DNA damage agents by, among others, promoting autophagy and limiting DNA damage accumulation. Citation Format: Benoit Marchand, Marie-Josee Boucher. DNA damage agents promote TFEB function and induce pro-survival autophagy signals [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2619.