Further, subclones from both cancer cell lines that have developed resistance to MNNG by loss of MMR, undergo even less senescence (< 0.01%) at equitoxic concentrations of MNNG; however, repeated exposure of MCF12A cells to 8 μM MNNG did not alter the rate of ≥ 75% senescence, after four sequential treatments (results not shown). Here, MRC1 is linked to cancer.