Adenovirus-mediated expression of both antisense ODC and AdoMetDC inhibited colorectal cancer cell growth in vitro

Extracellular polyamines-induced proliferation and migration of cancer cells by ODC, SSAT, and Akt1-mediated pathway

High levels of polyamines were observed and were related to a poor prognosis in cancer patients. However, the mechanism is not obvious. The aim of this study is to mimic the extracellular polyamines in a tumor microenviroment and to explore the role of extracellular polyamines in the proliferation and migration of cancer cells. Three different concentrations of polyamines composed of putrescine, spermidine, and spermine were used. Colony formation assay, wound healing assay, and transwell migration assay were performed. Akt1-overexpression cells were constructed. The related protein expression was examined using a western blot. In this study, polyamines promoted colony formation and cell migration in a concentration-dependent and time-dependent manner. Polyamines upregulated the expression of ornithine decarboxylase (ODC), SSAT, Akt1, Akt, hypoxia-inducible factors-1α, vascular endothelial growth factor, and matrix metalloproteinases, and downregulated p27 expression. The effects of combination of polyamines and Akt1 overexpression on colony formation and migration were more obvious than the effects of Akt1 overexpression alone. In Akt1-overexpression cells, polyamines also upregulated the expression of ODC, SSAT, hypoxia-inducible factors-1α, vascular endothelial growth factor, and matrix metalloproteinases and downregulated p27 expression. In conclusion, extracellular polyamines induced proliferation and cancer cell migration by inducing ODC and SSAT expression, and the Akt1-mediated pathway.

Adenovirus vector-mediated upregulation of spermidine /spermine N1-acetyltransferase impairs human gastric cancer growth in vitro and in vivo

Spermidine/spermine N(1)-acetyltransferase (SSAT) is the rate-limiting step in polyamine catabolism. In a previous study, we constructed a recombinant adenovirus, Ad-SSAT, which can express human SSAT. In the present study, we investigated the effect of upregulated and downregulated SSAT on gastric cancer cells. We found that upregulated SSAT could inhibit the growth of MGC803 and SGC7901 cells, whereas adverse results were found with downregulated SSAT. We further analyzed cell cycle profiles and the expression levels of the major cell cycle regulatory proteins of S phase. The results showed that the growth inhibition was caused by S phase arrest. Ad-SSAT suppressed the expression of cyclin A and nuclear factor E2F1 in MGC803 and SGC7901 cells. We observed the E2F promoter activity caused by Ad-SSAT using a reporter gene assay. We also investigated the antitumorigenicity of upregulated SSAT by Ad-SSAT using a SGC7901 xenograft model in nude mice. Our results suggest that the upregulation of SSAT by Ad-SSAT infection inhibited the growth of gastric cancer in vitro and in vivo. Ad-SSAT arrested gastric cancer cells in S phase, which was mediated through downregulation of the cyclin A-E2F signaling pathway.

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.

Adenovirus-mediated expression of SSAT inhibits colorectal cancer cell growth in vitro

AIM

To construct a recombinant adenovirus that can express human spermidine/ spermine N1-acetyltransferase (SSAT) and detect its inhibitory effect on colorectal cancer cell growth in vitro.

METHODS

A 516 bp cDNA of SSAT was amplified and cloned into a pGL3-hTERT plasmid. The pGL3-hTERT-SSAT recombinant was digested, and the small fragment was cloned into the shuttle vector pAdTrack. The pAdTrack-hTERT-SSAT plasmids were recombined with pAdEasy-1 vectors in AdEasy-1 cells. Positive clones were selected and transfected into the HEK293 packaging cells (transformed human embryonic kidney cells) after they were linearized by PacI. The process of adenovirus packaging and amplification was monitored by green fluorescent protein (GFP) expression. The SSAT protein levels were determined by Western blotting, and the intracellular polyamine content was detected by reverse-phase high performance liquid chromatography. The MTS (3-(4, 5-dimethylthiaol-2-yl)-5-(3-carboxy-methoxyphenyl)-2-(-4- sulfophenyl)-2H-tetrazolium, inner salt) and colony-forming assays were used to analyze the gene transduction efficiency and effect on the growth of HT-29 and LoVo cells. A viable cell count was used to determine the cell growth with or without exogenous polyamines.

RESULTS

The GFP expression in 293 cells during virus packing and amplification was observed by fluorescence microscopy. Western blotting results demonstrated that Ad-hTERT-SSAT could increase the expression of SSAT, and consequently, spermidine and spermine were reduced to low levels. The MTS and colony-forming assay results showed that HT-29 and LoVo cell growth were significantly inhibited, and the inhibitory effect could be partially reversed by exogenous spermidine and spermine.

CONCLUSION

The successfully constructed recombinant adenovirus Ad-hTERT-SSAT could accelerate polyamine catabolism and inhibit the colorectal cell growth in vitro. It also has therapeutic potential in the treatment of colorectal cancer.

Role of ornithine decarboxylase in breast cancer

Ornithine decarboxylase (ODC), the rate-limiting enzyme in polyamine biosynthesis that decarboxylates ornithine to putrescine, has become a promising target for cancer research. The aim of this study is to investigate the role of ODC in breast cancer. We detected expression of ODC in breast cancer tissues and four breast cancer cell lines, and transfected breast cancer cells with an adenoviral vector carrying antisense ODC (rAd-ODC/Ex3as) and examined their growth and migration. ODC was overexpressed in breast cancer tissues and cell lines compared with non-tumor tissues and normal breast epithelial cells, and there was a positive correlation between the level of ODC mRNA and the staging of tumors. The expression of ODC correlated with cyclin D1, a cell cycle protein, in synchronized breast cancer MDA-MB-231 cells. Gene transfection of rAd-ODC/Ex3as markedly down-regulated expression of ODC and cyclin D1, resulting in suppression of proliferation and cell cycle arrest at G0-G1 phase, and the inhibition of colony formation, an anchorage-independent growth pattern, and the migratory ability of MDA-MB-231 cells. rAd-ODC/Ex3as also markedly reduced the concentration of putrescine, but not spermidine or spermine, in MDA-MB-231 cells. The results suggested that the ODC gene might act as a prognostic factor for breast cancer and it could be a promising therapeutic target.

Recent developments in the use of adenoviruses and immunotoxins in cancer gene therapy

Despite setbacks in the past and apparent hurdles ahead, gene therapy is advancing toward reality. The past several years have witnessed this new field of biomedicine developing rapidly both in breadth and depth, especially for the treatment of cancer, thanks largely to the better understanding of molecular and genetic basis of oncogenesis and the development of new and improved vectors and technologies for gene delivery and targeting. This article is intended to provide a brief review of recent advances in cancer gene therapy using adenoviruses, both as vectors and as oncolytic agents, and some of the recent progress in the development of immunotoxins for use in cancer gene therapy.

Adenovirus-mediated expression of both antisense ornithine decarboxylase and s-adenosylmethionine decarboxylase induces G1 arrest in HT-29 cells

To evaluated the effect of recombinant adenovirus Ad-ODC-AdoMetDCas which can simultaneously express both antisense ornithine decarboxylase (ODC) and Sadenosylmethionine decarboxylase (AdoMetDC) on cell cycle distribution in colorectal cancer cell and investigated underlying regulatory responses, human colorectal cancer cells HT-29 were cultured in RPMI 1640 medium and infected with Ad-ODC-AdoMetDCas. Cell cycle progression was detected by flow cytometry analysis. The expression levels of cell cycle regulated proteins were measured by Western blot analysis. The mRNA level of cyclin D1 was measured by RT-PCR. And a luciferase reporter plasmid of cyclin D1 promoter was constructed to observe the effect of Ad-ODC-AdoMetDCas on cyclin D1 promoter activity. The results showed that recombinant adenovirus Ad-ODC-AdoMetDCas significantly induced G1 arrest, decreased levels of cyclin D1 protein and mRNA and suppressed the promoter activity. Ad-ODC-AdoMetDCas also inhibited nuclear translocation of beta-catenin. In conclusion, downregulation of ODC and AdoMetDC mediated by Ad-ODC-AdoMetDCas transfection induces G(1) arrest in HT-29 cells and the arrest was associated with suppression of cyclin D1 expression and inhibition of beta-catenin nuclear translocation. As a new anticancer reagent, the recombinant adenovirus Ad-ODC-AdoMetDCas holds promising hope for the therapy of colorectal cancers.