Dataset Information

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.

SUBMITTER: Bian Y

PROVIDER: S-EPMC3910639 | biostudies-literature | 2014 Jan

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Synthetic genetic array screen identifies PP2A as a therapeutic target in Mad2-overexpressing tumors.

Bian Yang Y Kitagawa Risa R Bansal Parmil K PK Fujii Yo Y Stepanov Alexander A Kitagawa Katsumi K

Proceedings of the National Academy of Sciences of the United States of America 20140114 4

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 synthet ...[more]

PMID: 24425774

Similar Datasets

Project description:The human SEC62 gene is located on chromosome 3q, was characterized as a tumor driver gene and is found to be overexpressed in an ever-growing number of tumors, particularly those with 3q26 amplification. Where analyzed, SEC62 overexpression was associated with poor prognosis. Sec62 protein is a membrane protein of the endoplasmic reticulum (ER) and has functions in endoplasmic reticulum protein import, endoplasmic reticulum-phagy and -in cooperation with the cytosolic protein calmodulin- the maintenance of cellular calcium homeostasis. Various human tumors show SEC62 overexpression in immunohistochemistry and corresponding cell lines confirm this phenomenon in western blots and immunofluorescence. Furthermore, these tumor cells are characterized by increased stress tolerance and migratory as well as invasive potential, three hallmarks of cancer cells. Strikingly, plasmid-driven overexpression of SEC62 in non-SEC62 overexpressing cells introduces the same three hallmarks of cancer into the transfected cells. Depletion of Sec62 from either type of SEC62 overexpressing tumor cells by treatment with SEC62-targeting siRNAs leads to reduced stress tolerance and reduced migratory as well as invasive potential. Where tested, treatment of SEC62 overexpressing tumor cells with the small molecule/calmodulin antagonist trifluoperazine (TFP) phenocopied the effect of SEC62-targeting siRNAs. Recently, first phase II clinical trials with the prodrug mipsagargin/G202, which targets cellular calcium homeostasis in prostate cells as well as neovascular tissue in various tumors were started. According to experiments with tumor cell lines, however, SEC62 overexpressing tumor cells may be less responsive or resistant against such treatment. Therefore, murine tumor models for tumor growth or metastasis were evaluated with respect to their responsiveness to treatment with a mipsagargin analog (thapsigargin), or trifluoperazine, which had previously been in clinical use for the treatment of schizophrenia, or with the combination of both drugs. So far, no additive effect of the two drugs was observed but trifluoperazine had an inhibitory effect on tumor growth and metastatic potential in the models. Here, we review the state of affairs.

Project description:Epigenetic pathways regulate gene expression by controlling and interpreting chromatin modifications. Cancer cells are characterized by altered epigenetic landscapes and commonly exploit the chromatin regulatory machinery to enforce oncogenic gene expression programs. While chromatin alterations are, in principle, reversible and often amendable to drug intervention, the promise of targeting such pathways therapeutically has been hampered by our limited understanding of cancer-specific epigenetic dependencies. Here we describe a non-biased approach to probe epigenetic vulnerabilities in acute myeloid leukemia (AML) – an aggressive hematopoietic malignancy often associated with aberrant chromatin states. By screening a custom shRNA library targeting known chromatin regulators in a genetically defined AML mouse model, we identify the bromodomain-containing protein Brd4 as a critical requirement for disease maintenance. Suppression of Brd4 using shRNAs or the small-molecule inhibitor JQ1 led to robust anti-leukemic effects in vitro and in vivo, accompanied by terminal myeloid differentiation. Extensive evaluation of JQ1-sensitivity in primary human leukemia samples and in established cell lines revealed a broad activity of this compound against diverse AML subtypes. These effects are, at least in part, due to a requirement for Brd4 in maintaining Myc expression and promoting aberrant self-renewal. Together, our results indicate that Brd4 is a promising therapeutic target in AML and identify a small molecule that efficiently targets Myc. These findings also highlight the utility of RNAi screening as a discovery platform for revealing epigenetic vulnerabilities for direct pharmacologic intervention in cancer. In order to understand downstream targets of Brd4, we performed array in murine or human MLL-AF9/NrasG12D cell line under the condition that Brd4 was suppressed by using shRNAs or the small molecule inhibitor JQ1. To test the hypothesis that Myc might be an important target of Brd4, we performed arrary on murine ectopic Myc overexpression MLL-AF9/NrasG12D cell under JQ1 treatment.

Dataset Information

Synthetic genetic array screen identifies PP2A as a therapeutic target in Mad2-overexpressing tumors.

Publications

Synthetic genetic array screen identifies PP2A as a therapeutic target in Mad2-overexpressing tumors.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets