MI-63: a novel small-molecule inhibitor targets MDM2 and induces apoptosis in embryonal and alveolar rhabdomyosarcoma cells with wild-type p53.
BACKGROUND
Interruption of the role of p53s as a tumour suppressor by MDM2 may be one of the mechanisms by which cancer cells evade current therapy. Blocking the inhibition of wild-type p53 by MDM2 in cancer cells should reactivate p53's tumour suppressor functions and enhance current cancer treatments. MI-63 is a novel non-peptide small molecule that has shown strong binding affinity (K(i)=3 nM) for MDM2; however, its effects on paediatric cancer cells and the specific mechanism of tumour suppressor reactivation have not been evaluated.


METHODS
Rhabdomyosarcoma (RMS), the most common childhood soft tissue sarcoma, expresses either wild-type or mutant p53 protein. We examined the inhibitory effects of MI-63 in embryonal RMS (ERMS) and alveolar RMS (ARMS) cell lines expressing wild-type or mutated p53.


RESULTS
Treatment with MI-63 reduced cell viability by 13.4% and by <1%, respectively, at 72 h in both RH36 and RH18 cell lines expressing wild-type p53. In contrast, RH30 and RD2 cells expressing p53 mutants are resistant to MI-63 treatment. An increased expression of p53, p21(WAF1), and Bax protein was observed after treatment with MI-63 in RMS cells with wild-type p53, and apoptosis was confirmed by cleaved PARP and caspase-3 expression. However, RD2 and RH30 RMS cells, as well as human normal skeletal muscle cells, showed a minimal increase in p53 signalling and no induction of cleaved PARP and caspase-3. MI-63 was compared with Nutlin-3, a known MDM2 inhibitor, and was found to be more potent in the inhibition of cell proliferation/viability. Further, synergy was observed when MI-63 was used in combination with doxorubicin.


CONCLUSIONS
These results indicate that MI-63 is a potent therapeutic agent for RMS cells expressing wild-type p53 protein.
Canner
J A
JA
Department of Pediatrics, Nationwide Children's Hospital, Columbus, OH, USA.
Sobo
M
M
Ball
S
S
Hutzen
B
B
DeAngelis
S
S
Willis
W
W
Studebaker
A W
AW
Ding
K
K
Wang
S
S
Yang
D
D
Lin
J
J
D000970:Antineoplastic Agents / Q000737:chemistry / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3 / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004317:Doxorubicin / Q000494:pharmacology; D004354:Drug Screening Assays, Antitumor; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D007211:Indoles / Q000737:chemistry / Q000494:pharmacology*; D008970:Molecular Weight; D010879:Piperazines / Q000494:pharmacology; D051736:Proto-Oncogene Proteins c-mdm2 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D018232:Rhabdomyosarcoma, Alveolar / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology*; D018233:Rhabdomyosarcoma, Embryonal / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology*; D015398:Signal Transduction / Q000187:drug effects; D013141:Spiro Compounds / Q000737:chemistry / Q000494:pharmacology*; D013329:Structure-Activity Relationship; D016159:Tumor Suppressor Protein p53 / Q000187:drug effects / Q000378:metabolism*
D000970:Antineoplastic Agents; D007093:Imidazoles; D007211:Indoles; C543589:MI-63 compound; D010879:Piperazines; D013141:Spiro Compounds; D016159:Tumor Suppressor Protein p53; C482205:nutlin 3; D004317:Doxorubicin; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2; D053148:Caspase 3
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