Fig 2: Graphical summary. (A) The concept of cancer development arising from the bypass of cellular senescence. Normal cells under oxidative stress accumulate genomic and epigenomic damage (8-oxo-dG ? and m5C ?) that leads to cellular senescence. Cancer cells treated with chemotherapy can also produce senescent cells, which are essentially dormant tumor cells. It is poorly understood how senescent cells can re-enter the cell-cycle to produce cancer stem cells with senescence traits. Ultimately, cancer cells that are produced from this process contribute to tumor relapse and progression. (B) Data arising from this study show that SCM activates cellular senescence in MRC5 and WI-38 fibroblasts. Histone demethylases, Utx and Jmjd3, facilitate a developmental process, overlapping with senescence reprogramming. In comparison to normal cells, A549 and 293T cancer cells cultured in SCM are converted to cancer stem cells with senescence traits.

Fig 3: shRNA knockdown of H3K27 demethylases reduces senescence-associated biomarkers. (A) Representative fluorescence microscopy images of MRC5 cell lines grown in SCM and expressing shRNAs targeting Jmjd3 and Utx. The addition of doxycycline (Dox) at 2 µg/mL activated each shRNA, as indicated by turbo red fluorescent protein (tRFP) reporter expression. Representative images show SA-ß-gal staining at 48 h. (B) Quantification for SA-ß-gal staining shown in A. (C) RT-qPCR analysis for the expression levels of H3K27 demethylases and SASP genes in control, Jmjd3, and Utx shRNA cell lines at 72 h. (B,C) Student’s t-test; bars represent standard deviation and asterisks indicate statistical significance (n.s., not significant; *, p = 0.05; **, p = 0.01; ***, p = 0.001; n = 3).