p53 and Adhesion

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    p53

    Ability to prevent undue cell proliferation

    Plays a critical role in the host and tumor

    response to radiation and chemotherapy

    It seems that p53 can be selectively

    reactivated in tumor cells target for gene

    therapy

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    In vivo activation of the p53 pathway by small-molecule antagonists of MDM2

    Vassilev LT, Vu BT, Graves B, Carvajal D, Podlaski F, Filipovic Z, KongN, Kammlott U, Lukacs C, Klein C, Fotouhi N, Liu E

    Science (2004)303: 844-848

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    3 mechanisms to repress p53 by activation of MDM2-expression:

    1. MDM2 binds p52 at transactivation domain and blocks its ability toacitvate transcription

    2. MDM2 is involved in the nuclear export of p533. MDM2 serves as a ubiquitin ligase that promotes p53 degradation

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    3 mechanisms to repress p53 by activation of MDM2-expression:

    1. MDM2 binds p52 at transactivatin domain and blocks its ability toacitvate transcription

    2. MDM2 is involved in the nuclear export of p533. MDM2 serves as a ubiquitin ligase that promotes p53 degradation

    Mdm2gene is amplified or overexpressed in many human cancers

    Activation of p53 pathway through inhibition of MDM2 has beenproposed as a novel therapeutic strategy

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    Series of cis-imidazolineanalogs that were named

    Nutlins (for Nutley inhibitor)

    Mode of binding of Nutlin in

    MDM2-p53 complex

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    The treatment of cells with an inhibitor of MDM2-p53 binding shouldresult in

    1. Stabilization and accumulation of p532. Activation of MDM2 expression3. Activation of other p53-regulated genes and p53 pathway

    At cellular level: cell cycle arrest in G1 and G2 phases and/orapoptosis

    Effect of MDM2 inhibitors on the cellular levelsof p53, MDM2 and p21

    Mut p53 wt p53

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    Nutlin-1 treatment induces theexpression of p21 gene but not the p53gene

    Nutlins up-regulate p53 by meansof a posttranslational mechanism

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    Cell cycle arrest of wt p53 cancer cell linesin G1 and G2 due to Nutlin-1

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    Effect of Nutlin-1 on growth and viability of

    cultured cancer cells

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    Effect of Nutlin-3a and Nutlin-3b on expression of p21, MDM2 andp53 in wt p53 and mut p53-cells

    Only Nutlin-3a activates expression of p21 and MDM2

    Confirmation of the protein level by

    Western blotting

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    Effect of Nutlin-3a and -3b on growth and viability of wt p53 andmut53 cells

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    Ability of Nutlin-3 to induce apoptosis in cancer cells withwt p53

    After 48 hours Nutlin-3a incubation 45% of cell population showed

    apoptosis

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    In vivo antitumor activity of Nutlin-3

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    SUMMARY

    Nutlins are a class of stuctures with high potency andselectivity for reactivating p53 by inhibition of p53-MDM3

    interaction Activity of Nutlins is dependent on p53 status There are two enantiomers of Nutlin-3. Activation of p53 and

    apoptosis induction by Nutlin-3 is enantiomer specific

    The data strengthen the notion that activation of p53 byinhibition of MDM2 binding is a potentially valuable strategyfor treating cancer