Antisense MDM2 oligonucleotides restore the apoptotic response of prostate cancer cells to androgen deprivation

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Abstract
BACKGROUND Early in the malignant transformation of prostate epithelial cells, the apoptotic response to androgen deprivation (AD) is lost and the principle response is a slowing of cell growth. In this study, we tested whether interruption of MDM2 function using antisense MDM2 oligonucleotide (AS) affects the apoptotic response of prostate cancer cells to AD. METHODS Wild type LNCaP cells and MDM2-overexpressing (LNCaP-MST) cells were treated with AS alone or in combination with AD. Protein levels of MDM2, p53, and p21 were determined by Western blotting. Cell viability was measure by trypan blue staining. Apoptotic cell death was confirmed by cell morphological changes, annexin V/propidium iodide staining and caspase-3 + 7 activity. Overall cell survival was quantified by clonogenic assay. RESULTS AS inhibited MDM2 expression to a greater extent in LNCaP cells, as compared to LNCaP-MST cells. AS enhanced the expression of p53 and p21 in both cell lines. The growth inhibitory and cell death effects of AS + AD were generally greater than AS alone in LNCaP cells. Treatment of LNCaP cells with AS + AD for 72 hr caused a significant increase in cell death (66%) over AD alone (13%), AS alone (33%), or AD + AS + R1881 (34% with synthetic androgen replacement) that was attributable mainly to apoptosis. Clonogenic survival reflected the same pattern. CONCLUSIONS Our results suggest that the apoptotic response of prostate cancer to AD is strongly influenced by MDM2 expression. Antisense MDM2 has broad potential as a therapeutic agent to sensitize prostate cancer cells to AD therapy by enhancing apoptotic cell death.