Chemosensitization by antisense oligonucleotides targeting MDM2.

The MDM2 oncogene is overexpressed in many human cancers, including sarcomas, certain hematologic malignancies, and breast, colon and prostate cancers. The p53-MDM2 interaction pathway has been suggested as a novel target for cancer therapy. To that end, several strategies have been explored, including the use of small polypeptides targeted to the MDM2-p53 binding domain, anti-MDM2 antisense oligonucleotides, and natural agents. Different generations of anti-human-MDM2 oligonucleotides have been tested in in vitro and in vivo human cancer models, revealing specific inhibition of MDM2 expression and significant antitumor activity. Use of antisense oligos potentiated the effects of growth inhibition, p53 activation and p21 induction by several chemotherapeutic agents. Increased therapeutic effectiveness of chemotherapeutic drugs in human cancer cell lines carrying p53 mutations or deletions have shown the ability of MDM2 inhibitors to act as chemosensitizers in various types of tumors through both p53-dependent and p53-independent mechanisms. Inhibiting MDM2 appears to also have a role in radiation therapy for human cancer, regardless of p53 status, providing a rationale for the development of a new class of radiosensitizers. Moreover, MDM2 antisense oligonucleotides potentiate the effect of epidermal growth factor receptor (EGFR) inhibitors by affecting in vitro and in vivo proliferation, apoptosis and protein expression in hormone-refractory and hormone-dependent human prostate cancer cells. These data support the development, among other MDM2 inhibitors, of anti-MDM2 antisense oligonucleotides as a novel class of anticancer agents, and suggest a potentially relevant role for the oligonucleotides when integrated with conventional treatments and/or other signaling inhibitors in novel therapeutic strategies.