Abstract
Genistein has been shown to inhibit human prostate cancer (PCa) cell motility. Endoglin has been identified as an important suppressor of PCa cell motility, and its expression is lost during PCa progression. It is therefore important to determine whether endoglin loss affects genistein's efficacy and, if so, by what mechanism. In the current study, genistein was shown to induce reversion of endoglin-deficient cells to a low motility, endoglin-replete phenotype. Because endoglin suppresses PCa cell motility in an activin-like kinase receptor-2 (ALK2)- and Smad1-dependent manner, we sought to determine whether genistein was activating the ALK2-Smad1 pathway. Although treatment with genistein or overexpression of Smad1 or ALK2 all increased Smad1-responsive promoter activity and decreased cell motility, genistein's efficacy was abrogated by either Smad1 or ALK2 knockdown. Furthermore, transfection of cells with a kinase dead mutant of ALK2 abrogated genistein's efficacy. Together, these findings demonstrate that genistein therapeutically induces reversion to a low-motility phenotype in aggressive endoglin-deficient PCa cells. It does so by activating ALK2-Smad1 endoglin-associated signaling. These findings support the notion that individuals with low endoglin-expressing PCa will benefit from genistein treatment.
Footnotes
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This work was funded by a merit review award from the Veterans Administration to R.C.B. C.S.C. was funded by National Institutes of Health training grant T32-CA09560, a Malkin scholarship, and an award from the Chicago Baseball Cancer Charities. D.R. and R.C.B. were funded by the Maine Cancer Foundation.
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ABBREVIATIONS: PCa, prostate cancer; ALK, activin-like kinase receptor; β-gal, β-galactosidase; ENG, endoglin; HA, hemaglutinin; KD, kinase dead; PC3, parental prostate cancer cell line; PC3-M, metastatic prostate cancer cell line; siRNA, small interfering RNA; siNeg, small interfering RNA negative control; TGFβ, transforming growth factor β; RI, type I transforming growth factor β superfamily receptor; qRT/PCR, quantitative reverse transcription/polymerase chain reaction; VC, empty vector; siENG, small interfering RNA-targeting endoglin; FACS, fluorescence-activated cell sorting; BRE2-Luc, BRE2-Luciferase; Sd1, Smad1; siSd1, small interfering RNA-targeting Smad1; siA2, small interfering RNA-targeting ALK2; WT, wild type; MAP, mitogen-activated protein.
- Received June 10, 2007.
- Accepted October 18, 2007.
- The American Society for Pharmacology and Experimental Therapeutics
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