PT  - JOURNAL ARTICLE
AU  - Randal W. Berg
AU  - Melanie Werner
AU  - Peter J. Ferguson
AU  - Carl Postenka
AU  - Mark Vincent
AU  - D. James Koropatnick
AU  - Elke Behrend
TI  - Tumor Growth Inhibition in Vivo and G<sub>2</sub>/M Cell Cycle Arrest Induced by Antisense Oligodeoxynucleotide Targeting Thymidylate Synthase
DP  - 2001 Aug 01
TA  - Journal of Pharmacology and Experimental Therapeutics
PG  - 477--484
VI  - 298
IP  - 2
4099  - http://jpet.aspetjournals.org/content/298/2/477.short
4100  - http://jpet.aspetjournals.org/content/298/2/477.full
SO  - J Pharmacol Exp Ther2001 Aug 01; 298
AB  - Chemotherapeutic agents targeting thymidylate synthase (TS) are effective against human tumors. Efficacy is limited by drug resistance, often mediated by TS overexpression. Treatment of HeLa cells in vitro with an antisense oligodeoxynucleotide (ODN 83) targeting human TS mRNA reduces TS mRNA and protein levels, inhibits cell proliferation, and sensitizes cells to TS-targeting drugs (Ferguson et al., 1999). The present study investigates the mechanism by which ODN 83 inhibits cell proliferation and examines its antitumor efficacy in vivo. ODN 83 treatment did not induce apoptosis in HeLa cells in vitro but caused accumulation of cells at G2/M. In contrast, TS-targeting chemotherapeutics arrest at G1 or S. Antisense down-regulation reduced TS mRNA levels in human colon cancer (HT29) cells by 40% in vitro, resulted in G2/M arrest, and reduced proliferation without enhanced cell death. Growth of HT29 tumors in immunocompromised mice was significantly inhibited when antisense ODN 83 treatment began promptly after tumor implantation and was accompanied by a 40% reduction in TS protein levels. Growth of tumors allowed to reach 400 mm3 prior to ODN administration was unaffected by antisense ODN 83. Radiolabeled ODNs were localized to the tumor periphery but evenly distributed in normal tissue. Thus, down-regulation of TS mRNA and protein by antisense ODN treatment exerts a novel G2/M cell cycle block without increasing cell death and inhibits HT29 tumor cell growth in vivo. Antisense ODN 83 may be an effective therapy for colon carcinoma, alone or in combination with TS-targeting cytotoxic drugs. The American Society for Pharmacology and Experimental Therapeutics