Inhibition of cell growth by NB1011 requires high thymidylate synthase levels and correlates with p53, p21, bax, and GADD45 induction.

Abstract	NB1011, a phosphoramidate derivative of (E)-5-(2-bromovinyl)-2'-deoxyuridine, is a novel small molecule anticancer agent. NB1011 is selectively active against tumor cells expressing high levels of thymidylate synthase (TS), a critical enzyme in DNA biosynthesis. NB1011 is different from the current TS-targeted drugs, which require inhibition of TS to be effective, because NB1011 cytotoxicity depends upon activation by TS. Here we report a dose-dependent, antitumor activity of NB1011 against established Tomudex-resistant breast cancer (MCF7TDX) xenografts in athymic mice. Against 5-fluorouracil-resistant colon carcinoma (H630R10) xenografts, NB1011 was as efficacious as irinotecan, a drug recently approved for the treatment of 5-fluorouracil-resistant colon cancer. To gain insight into the mechanisms NB1011 uses to suppress cellular growth, we analyzed the downstream molecular events in the high TS-expressing MCF7TDX and RKOTDX cell lines upon NB1011 treatment. NB1011 treatment increased the mRNA levels of p21, Bax, and GADD45. Furthermore, NB1011 induced p53, p21, and Bax proteins specifically in high TS-expressing tumor cells, whereas no induction was observed in low TS-expressing tumor cells (MCF7) or normal cells (WI38). Cell cycle analysis demonstrated that NB1011 treatment of MCF7TDX and RKOTDX cells resulted in an accumulation of cells in the G2-M phase of the cell cycle. Altogether, our data indicate that the induction of the p53 target genes p21, bax, and GADD45, with a concomitant deregulation of the cell cycle, may represent one of the mechanisms by which NB1011 exerts its growth-suppressive effects.
Authors	Saskia T C Neuteboom, Patricia L Karjian, Christopher R Boyer, Malgorzhata Beryt, Mark Pegram, Geoffrey M Wahl, H Michael Shepard
Journal	Molecular cancer therapeutics (Mol Cancer Ther) Vol. 1 Issue 6 Pg. 377-84 (Apr 2002) ISSN: 1535-7163 [Print] United States
PMID	12477050 (Publication Type: Journal Article)
Chemical References	Annexin A5 Antimetabolites, Antineoplastic BAX protein, human Bax protein, mouse CDKN1A protein, human Cdkn1a protein, mouse Cyclin-Dependent Kinase Inhibitor p21 Cyclins GADD45 protein Intracellular Signaling Peptides and Proteins NB1011 Proteins Proto-Oncogene Proteins Proto-Oncogene Proteins c-bcl-2 RNA, Messenger Tumor Suppressor Protein p53 bcl-2-Associated X Protein Thymidylate Synthase Oncogene Protein p21(ras) Bromodeoxyuridine
Topics	Animals Annexin A5 (metabolism) Antimetabolites, Antineoplastic (pharmacology) Apoptosis (drug effects) Breast Neoplasms (enzymology, pathology) Bromodeoxyuridine (analogs & derivatives, pharmacology) Cell Cycle (drug effects) Cell Division (drug effects) Colonic Neoplasms (enzymology, pathology) Cyclin-Dependent Kinase Inhibitor p21 Cyclins (biosynthesis, genetics) Epithelial Cells (enzymology) Female Fibroblasts (enzymology) Humans Intracellular Signaling Peptides and Proteins Mice Mice, Nude Oncogene Protein p21(ras) (biosynthesis, genetics) Protein Biosynthesis Proteins (genetics) Proto-Oncogene Proteins (biosynthesis, genetics) Proto-Oncogene Proteins c-bcl-2 RNA, Messenger (biosynthesis) Thymidylate Synthase (metabolism) Tumor Cells, Cultured Tumor Suppressor Protein p53 (biosynthesis, genetics) bcl-2-Associated X Protein

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