Canonical autophagy remains inactive in induced pluripotent stem cells and neuronal progenitor cells following DNA damage induced by BPDE or etoposide

(Macro-)Autophagy is a key cellular stress response mediating the recycling of long-lived or damaged proteins and organelles. In stem cells, autophagy is essential for the decision between quiescence, self-renewal and differentiation. We observed that induced pluripotent stem cells (iPSCs) and thereof derived neural progenitor cells (NPCs) have a functional autophagy machinery, as shown by starvation-induced autophagic flux and ULK1 activation. Using the human iPSC lines iPS11 and iPS12 and thereof derived NPCs (niPS11 and niPS12), we investigated whether genotoxic stress induced by low doses (IC₂₀) of benzo[a]pyrene diolepoxide (BPDE) or etoposide can similarly activate autophagy, as previously reported for cancer cell lines. While both BPDE and etoposide induced the DNA damage markers phospho-p53 Ser15 and γH2AX and slightly altered the expression of DNA repair proteins such as XPC, they did not trigger autophagic flux in either iPSCs or NPCs. After genotoxin treatment, ULK1 activation was only observed in NPCs, but this was not sufficient to trigger a significant downstream autophagic response. Mass spectrometry revealed minimal proteomic changes in iPSCs and moderate changes in NPCs, mainly involving mitotic regulators. In summary, no significant activation of canonical autophagy was detectable in iPSCs and NPCs within the tested time frame and under low-dose genotoxic conditions, although both cell types retain a functional autophagic machinery.