LAUSR

Simple Summary We exposed LUHMES cells, differentiated into mature neurons, to bortezomib (BTZ) in two treatment cycles and analyzed the methylomes of these cells after each cycle, controlling the analysis for the methylation changes potentially induced by the long-term culture. Our results show that BTZ induces methylation changes that may affect cell morphogenesis, neurogenesis, and neurotransmission. These changes are specifically enriched within transcription factor binding sites of EBF, PAX, DLX, LHX, and HNF family members, which have been shown to regulate neurogenesis and neuronal differentiation. We further show that the observed methylation changes are not present in the SH-SY5Y cells that we used to study mechanisms of development of BTZ resistance. Altogether, our results show that BTZ treatment induces very specific changes in the methylomes of neuronal cells. Abstract Bortezomib (BTZ) is proteasome inhibitor, effectively used in the treatment of multiple myeloma, but frequently discontinued due to peripheral neuropathy, which develops in patients after consecutive treatment cycles. The molecular mechanisms affected by BTZ in neuronal cells, which result in neuropathy, remain unknown. However, BTZ is unlikely to lead to permanent morphological nerve damage, because neuropathy reverses after discontinuation of treatment, and nerve cells have very limited renewal capacity. We have previously shown that BTZ induces methylation changes in SH-SY5Y cells, which take part in the development of treatment resistance. Here, we hypothesized that BTZ affects the methylomes of mature neurons, and these changes are associated with BTZ neurotoxicity. Thus, we studied methylomes of neuronal cells, differentiated from the LUHMES cell line, after cycles of treatment with BTZ. Our results show that BTZ induces specific methylation changes in mature neurons, which are not present in SH-SY5Y cells after BTZ treatment. These changes appear to affect genes involved in morphogenesis, neurogenesis, and neurotransmission. Furthermore, identified methylation changes are significantly enriched within binding sites of transcription factors previously linked to neuron physiology, including EBF, PAX, DLX, LHX, and HNF family members. Altogether, our results indicate that methylation changes are likely to be involved in BTZ neurotoxicity.