Reactivation of p53 by a specific MDM2 antagonist (MI-43) leads to p21-mediated cell cycle arrest and selective cell death in colon cancer.
MDM2 oncoprotein binds directly to the p53 tumor suppressor and inhibits its function in cancers retaining wild-type p53. Blocking this interaction using small molecules is a promising approach to reactivate p53 function and is being pursued as a new anticancer strategy. The spiro-oxindole MI-43, a small-molecule inhibitor of the MDM2-p53 interaction, was designed and examined for its cellular mechanism of action and therapeutic potential in colon cancer. MI-43 binds to MDM2 protein with a K(i) value of 18 nmol/L and is 300 times more potent than a native p53 peptide. MI-43 blocks the intracellular MDM2-p53 interaction and induces p53 accumulation in both normal and cancer cells, with wild-type p53 without causing p53 phosphorylation. Induction of p53 leads to modulation of the expression of p53 target genes, including up-regulation of p21 and MDM2 in normal primary human cells and in colon cancer cells with wild-type p53. Using HCT-116 isogenic colon cancer cell lines differing only in p53 status or RNA interference to knockdown expression of p53 in the RKO colon cancer cell line, we show that the cell growth inhibition and cell death induction by MI-43 is p53 dependent. Furthermore, induction of cell cycle arrest by MI-43 is dependent on p53 and p21. In normal cells, MI-43 induces cell cycle arrest but not apoptosis. This study suggests that p53 activation by a potent and specific spiro-oxindole MDM2 antagonist may represent a promising therapeutic strategy for the treatment of colon cancer and should be further evaluated in vivo and in the clinic.
Comprehensive Cancer Center, University of Michigan, 1500 East Medical Center Drive, Ann Arbor, MI 48109, USA.
Sanjeev
S
Shangary
Ke
K
Ding
Su
S
Qiu
Zaneta
Z
Nikolovska-Coleska
Joshua A
JA
Bauer
Meilan
M
Liu
Guoping
G
Wang
Yipin
Y
Lu
Donna
D
McEachern
Denzil
D
Bernard
Carol R
CR
Bradford
Thomas E
TE
Carey
Shaomeng
S
Wang
D000970:Antineoplastic Agents / Q000737:chemistry / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D051017:Apoptosis Regulatory Proteins; D020169:Caspases / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D003110:Colonic Neoplasms / Q000201:enzymology / Q000473:pathology*; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism*; D045304:Cytochromes c / Q000378:metabolism; D015195:Drug Design; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D007211:Indoles / Q000737:chemistry / Q000494:pharmacology*; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000378:metabolism; D010768:Phosphoserine / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D051736:Proto-Oncogene Proteins c-mdm2 / Q000037:antagonists & inhibitors*; D013141:Spiro Compounds / Q000737:chemistry / Q000494:pharmacology*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
D000970:Antineoplastic Agents; D051017:Apoptosis Regulatory Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; C412403:DIABLO protein, human; D007211:Indoles; D047908:Intracellular Signaling Peptides and Proteins; C530788:MI 43 compound; D024101:Mitochondrial Proteins; D013141:Spiro Compounds; D016159:Tumor Suppressor Protein p53; D010768:Phosphoserine; D045304:Cytochromes c; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2; D020169:Caspases