Feed-forward miR-181d degradation modulates population variance of methyl-guanine methyl transferase (MGMT) and temozolomide resistance

To characterize the changes in miRNA expression in response to TMZ therapy, two patient-derived glioblastoma cell lines BT-83 and CMK3 were treated with 500 μM TMZ or vehicle for 6 h. These cell lines were selected because their gene expression profile suggests they capture the two key glioblastoma cell states: BT-83 exhibits an expression pattern suggestive of the mesenchymal-like state, while CMK3 exhibits an expression pattern suggestive of the neural progenitor-like state45. RNA was extracted and profiled by RNA sequencing. In both cell lines, the TMZ treatment did not significantly alter the expression of >95% of the miRNAs.miRNAs exhibiting a >2-fold change in expression following TMZ treatment in both lines were individually assessed to determine whether their expression differed in matched pre- and post-TMZ-treated clinical glioblastoma specimens.Among the miRNAs evaluated, miR-181d was the only one consistently showing lowered levels in the post-TMZ specimens. This finding recapitulated our prior profiling experiment, where miR-181d was downregulated in post-TMZ-treated clinical glioblastoma specimens.