GSE163013
CRISPR/Cas9 Genome Editing of the Human Topoisomerase IIa Intron-19 5' Splice Site Circumvents Etoposide Resistance in Human Leukemia K562 Cells
Results indicate that CRISPR/Cas9 gene editing of a suboptimal E19/I19 5' splice site in the TOP2a gene results in circumvention of acquired drug resistance to etoposide and other TOP2-targeted drugs in a clonal K562 cell line by enhancing removal of intron 19 thereby decreasing formation of a truncated TOP2a/90 isoform and increasing expression of full-length TOP2a/170 in these resistant cells. Overall design: An etoposide-resistant K562 clonal subline, K/VP.5, with reduced levels of TOP2a/170, expresses high levels of a novel C-terminal truncated TOP2a isoform (90 kDa, TOP2a/90). TOP2a/90, the translation product of a TOP2a mRNA that retains a processed intron 19 (I19), heterodimerizes with TOP2a/170 and is a resistance determinant through a dominant negative effect on drug activity. We hypothesized that genome editing to enhance I19 removal would provide a tractable strategy to circumvent acquired TOP2a-mediated drug resistance. To enhance I19 removal in K/VP.5 cells, CRISPR/Cas9 was utilized to make changes (GAG//GTAAAC?GAG//GTAAGT) in the TOP2a gene's suboptimal exon 19/intron 19 5' splice site (E19/I19 5' SS).