MRC1 and mismatch repair cancer syndrome 1: LN229TR2 cells were selected from their parental LN229 cell line through long-term treatment with TMZ; these cells have lost their MMR function, as indicated by low expression of MMR proteins MSH2 and MSH6 (Figure 1B), along with the emergence of microsatellite instability (Figure 1C), a characteristic marker of MMR deficiency.