Transiently enhanced multi-drug resistance by epigenetic mechanism from reprogrammed cancer cell model

Background: Drug resistance by epigenetic modulation in cancer cells has been suggested, and the epigenetic-driven heterogeneity has been suggested as an important mechanism. To elucidate the epigenetic mechanism further, epigenetically reprogrammed cancer (R-cancer) cells were established and their resistance during differentiation was analyzed. Methods: R-cancer cells for H460 (R-H460) were established by transient introduction of reprogramming factors. Then, differentiated R-H460 (dR-H460) cells were prepared by withdrawal of stem cell media (SCM) for various durations, and the changes in drug resistance were tested. Results: dR-H460 cells with SCM-withdrawal for about 2 weeks (mdR-H460 cells) formed significantly more drug-resistant colonies to both cisplatin and paclitaxel. The resistant phenotype of the cisplatin resistant colonies from mdR-H460 cells, however, was lost after long-term (about 70-90 days) cisplatin-withdrawal, suggesting a transient epigenetic mechanism. In another R-cancer cell model with N87, the increased drug-resistance was also observed for both cisplatin and paclitaxel after SCM-withdrawal. In single cell analyses, heterogeneity did not increase significantly in mdR-H460, although relatively higher fraction of mdR-H460 cells was observed in several clusters of parent H460 cells. Conclusion: Based on R-cancer model, increased cancer cell population under epigenetic transition, rather than heterogeneity from epigenetic changes, may confer the epigenetic-driven drug resistance, which can provide a new strategy to fight cancers by control of cancer cells under epigenetic transition. Single cell RNA sequencing was performed on H460, mdR-H460, and ldR-H460 cells. After quality filtration and integration of parent H460 and two epigenetic H460 variants of mdR-H460 and ldR-H460, we obtained an integrated single cell transcriptome for 14,638 cells.