Molecular basis for the induction of an angiogenesis inhibitor, thrombospondin-1, by 5-fluorouracil.

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Zhao HY, Ooyama A, Yamamoto M, Ikeda R, Haraguchi M, Tabata S, Furukawa T, Che XF, Zhang S, Oka T, Fukushima M, Nakagawa M, Ono M, Kuwano M, Akiyama S

Molecular basis for the induction of an angiogenesis inhibitor, thrombospondin-1, by 5-fluorouracil.

Cancer Res. 2008 Sep 1;68(17):7035-41. doi: 10.1158/0008-5472.CAN-07-6496.

PubMed ID

18757417 [ View in PubMed

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Abstract

5-Fluorouracil (5-FU) is one of the most commonly used anticancer drugs in chemotherapy against various solid tumors. 5-FU dose-dependently increased the expression levels of intrinsic antiangiogenic factor thrombospondin-1 (TSP-1) in human colon carcinoma KM12C cells and human breast cancer MCF7 cells. We investigated the molecular basis for the induction of TSP-1 by 5-FU in KM12C cells. Promoter assays showed that the region with the Egr-1 binding site is critical for the induction of TSP-1 promoter activity by 5-FU. The binding of Egr-1 to the TSP-1 promoter was increased in KM12C cells treated with 5-FU. Immunofluorescence staining revealed that 5-FU significantly increased the level of Egr-1 in the nuclei of KM12C cells. The suppression of Egr-1 expression by small interfering RNA decreased the expression level of TSP-1. Furthermore, 5-FU induced the phosphorylation of p38 mitogen-activated protein kinase (MAPK) and heat shock protein 27 (HSP27). Blockade of the p38 MAPK pathway by SB203580 remarkably inhibited the phosphorylation of HSP27 induced by 5-FU and decreased the induction of Egr-1 and TSP-1 by 5-FU in KM12C cells. These findings suggest that the p38 MAPK pathway plays a crucial role in the induction of Egr-1 by 5-FU and that induced Egr-1 augments TSP-1 promoter activity, with the subsequent production of TSP-1 mRNA and protein.