title: Synthetic genetic array screen identifies PP2A as a therapeutic target in Mad2-overexpressing tumors.
abstract: The spindle checkpoint is essential to ensure proper chromosome segregation and thereby maintain genomic stability. Mitotic arrest deficiency 2 (Mad2), a critical component of the spindle checkpoint, is overexpressed in many cancer cells. Thus, we hypothesized that Mad2 overexpression could specifically make cancer cells susceptible to death by inducing a synthetic dosage lethality defect. Because the spindle checkpoint pathway is highly conserved between yeast and humans, we performed a synthetic genetic array analysis in yeast, which revealed that Mad2 overexpression induced lethality in 13 gene deletions. Among the human homologs of candidate genes, knockdown of PPP2R1A, a gene encoding a constant regulatory subunit of protein phosphatase 2, significantly inhibited the growth of Mad2-overexpressing tumor cells. PPP2R1A inhibition induced Mad2 phosphorylation and suppressed Mad2 protein levels. Depletion of PPP2R1A inhibited colony formation of Mad2-overexpressing HeLa cells but not of unphosphorylated Mad2 mutant-overexpressing cells, suggesting that the lethality induced by PP2A depletion in Mad2-overexpressing cells is dependent on Mad2 phosphorylation. Also, the PP2A inhibitor cantharidin induced Mad2 phosphorylation and inhibited the growth of Mad2-overexpressing cancer cells. Aurora B knockdown inhibited Mad2 phosphorylation in mitosis, resulting in the blocking of PPP2R1A inhibition-induced cell death. Taken together, our results strongly suggest that PP2A is a good therapeutic target in Mad2-overexpressing tumors.
authors.affiliation: Center for Childhood Cancer and Blood Diseases, The Research Institute at Nationwide Children's Hospital, Columbus, OH 43205.
authors.forename: Yang
authors.initials: Y
authors.lastname: Bian
authors.forename: Risa
authors.initials: R
authors.lastname: Kitagawa
authors.forename: Parmil K
authors.initials: PK
authors.lastname: Bansal
authors.forename: Yo
authors.initials: Y
authors.lastname: Fujii
authors.forename: Alexander
authors.initials: A
authors.lastname: Stepanov
authors.forename: Katsumi
authors.initials: K
authors.lastname: Kitagawa
mesh_terms: D001483:Base Sequence; D002193:Cantharidin / Q000494:pharmacology; D017931:DNA Primers; D004791:Enzyme Inhibitors / Q000494:pharmacology; D055785:Gene Knockdown Techniques; D006367:HeLa Cells; D006801:Humans; D064246:Mad2 Proteins / Q000235:genetics / Q000378:metabolism*; D009369:Neoplasms / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D054648:Protein Phosphatase 2 / Q000037:antagonists & inhibitors* / Q000235:genetics; D034741:RNA, Small Interfering
chemical_list: D017931:DNA Primers; D004791:Enzyme Inhibitors; C577697:MAD2L1 protein, human; D064246:Mad2 Proteins; D034741:RNA, Small Interfering; D054648:Protein Phosphatase 2; D002193:Cantharidin
keywords: aneuploidy; anticancer drug; cancer therapy target; yeast genetics