Inhibition of ornithine decarboxylase and S-adenosylmethionine decarboxylase synthesis by antisense oligodeoxynucleotides

Effects of antisense RNA targeting of ODC and AdoMetDC on the synthesis of polyamine synthesis and cell growth in prostate cancer cells using a prostatic androgen-dependent promoter in adenovirus

PURPOSE

This study was designed to investigate the use of a prostatic androgen-dependent promoter to mediate antisense targeting of ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase (AdoMetDC) and its effects on the synthesis of polyamine. We also examined the potential of this construct for prostate cancer therapy.

METHODS

pADxsi-PSES-AdoMetDC-ODC-PolyA AV was constructed and used to infect various cancer cell lines, including LNCaP, HT-29, H1299, HepG2. The effects of pADxsi-PSES-AdoMetDC-ODC-PolyA AV on the expression of ODC and AdoMetDC, in addition to the cell cycle, apoptosis and p21 levels, were analyzed through Western blotting and cytometry. A Matrigel invasion assay was used to analyze the effects of the recombinant virus on tumor cell invasion. The effect on polyamine content was also determined, and the relationship between inhibition of cellular ODC and AdoMetDC and decreases in polyamine were also investigated using a polyamine recovery assay.

RESULTS

Treatment with pADxsi-PSES-AdoMetDC-ODC-PolyA at an MOI of 90 significantly inhibited the proliferation of LNCaP cells, which could not be recovered through the addition of exogenous putrescine. The expression of ODC and AdoMetDC was also reduced, as was the polyamine content. The G1 phase of LNCaP cells was delayed, but no increase in apoptosis was detected. The down-regulation of ODC and AdoMetDC led to increased p21 expression.

CONCLUSIONS

The pADxsi-PSES-AdoMetDC-ODC-PolyA AV specifically inhibited the expression of ODC and AdoMetDC and the synthesis of polyamine, while it induced p21 expression, resulting in cell growth arrest in the G1 phase in prostate cancer cells but not in other cells.

Gene expression of ornithine decarboxylase in lung cancers and its clinical significance

Lung cancer is one of the most lethal cancers in China because of its high incidence and high mortality. Ornithine decarboxylase (ODC), an important enzyme in polyamine biosynthesis, is increased in cancer cells. Some chemotherapeutic agents aimed at reducing ODC expression show inhibitory effects on cancer cell growth, so ODC can be useful in gene diagnosis and gene therapy of cancers. In this study, we examined the effect of antisense ODC on lung cancer cells. A-549 cells were infected with rAd-ODC/Ex3as, a recombinant adenovirus containing the cytomegalovirus promoter, green fluorescent protein gene and 120 bp antisense ODC. The cell cycle was evaluated by flow cytometry. A nude mouse xenograft model was used in the tumorigenicity test. Reverse transcription-polymerase chain reaction, Western blot and immunohistochemistry were used to study the expressions of ODC on lung cancers. It was found that the growth of cells infected with rAd-ODC/Ex3as was substantially inhibited and cells were arrested at G1 phase. Cells infected with rAd-ODC/Ex3as can suppress tumor formation in a nude mouse xenograft model. The expression of ODC mRNA and ODC protein levels in lung cancer tissues was significantly higher than that in normal tissues (P<0.05), which correlated significantly with the stage of lung cancer (P<0.05). This study suggested that rAd-ODC/Ex3as has antitumor activity in human lung cancer cells. The ODC gene might play an important role in lung cancer and the overexpression of ODC might be related to the occurrence and development of lung cancer.

Antitumor effect of antisense ODC adenovirus on human prostate cancer cells

Ornithine decarboxylase (ODC), the first enzyme of polyamine biosynthesis, was found to increase in cancer cells, especially prostate cancers. Some chemotherapeutic agents aimed to decrease ODC expression showed inhibitory effects on cancer cells. In this study, we examined the effect of adenoviral-transduced antisense ODC on prostate cancer cells. An adenovirus carrying antisense ODC (rAd-ODC/Ex3as) was infected to prostate cancer cells PC-3 and LNCap. Expression of ODC and concentration of polyamines in cells were determined by Western blotting and HPLC. MTT (3-(4,5-methylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide) assay was used to analyze the effect on cell growth. Cell cycle was evaluated by FCM and cellular invasion by Matrigel invasion assay. A nude mouse xenograft model was used to examine tumorigenicity. Expression of ODC in PC-3 and LNCap cells were reduced to 45 and 59%, and three polyamines were also decreased by the rAd-ODC/Ex3as treatment. Consequently, cell growth was substantially inhibited and cell cycle arrested at G1 phase. Matrigel invasion assay showed relatively low invasion. Marked suppression of tumor formation was observed in the xenograft model. This study suggests that rAd-ODC/Ex3as has the antitumor effect on the human prostate cancer cells.