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AIM: To examine whether trans-W,cis-12 CLA (t10c12) or cis-9,trans-11 CLA (c9t11) inhibits heregulin (HRG)-β-stimulated cell growth and HRG-β-ErbB3 signaling in HT-29 cells. METHODS: We cultured HT-29 cells in the absence or presence of the CLA isomers and/or the ErbB3 ligand HRG-p. MTT assay, [3H]thymidine incorporation, Annexin V staining, RT-PCR, Western blotting, immunoprecipitation, and in vitro kinase assay were performed. RESULTS: HRG-p increased cell growth, but did not prevent t10c12-induced growth inhibition. T10c12 inhibited DNA synthesis and induced apoptosis of HT-29 cells, whereas c9t11 had no effect. T10c12 decreased the levels of ErbB1, ErbB2, and ErbB3 proteins and transcripts in a dose-dependent manner, whereas c9t11 had no effect. Immunoprecipitation/ Western blot studies revealed that t10c12 inhibited HRG-β-stimulated phosphorylation of ErbB3, recruitment of the p85 subunit of phosphoinositide 3-kinase (PI3K) to ErbB3, ErbB3-associated PI3K activities, and phosphorylation of Akt. However, c9t11 had no effect on phospho Akt levels. Neither t10c12 nor c9t11 had any effect on HRG-β-induced phosphorylation of ERK-1/2. CONCLUSION: These results indicate that the inhibition of HT-29 cell growth by t10c12 may be induced via its modulation of ErbB3 signaling leading to inhibition of Akt activation.
AIM: To examine whether trans-W, cis-12 CLA (t10c12) or cis-9, trans-11 CLA (c9t11) inhibits heregulin (HRG) -β-stimulated cell growth and HRG-β-ErbB3 signaling in HT-29 METHODS. We cultured HT-29 cells in the absence or presence of the CLA isomers and / or the ErbB3 ligand HRG-p. MTT assay, [3H] thymidine incorporation, Annexin V staining, RT-PCR, Western blotting, immunoprecipitation , and in vitro kinase assay were performed. T10c12 inhibited DNA synthesis and induced apoptosis of HT-29 cells, but c9t11 had no effect. T10c12 decreased the levels of ErbB1, ErbB2, and ErbB3 proteins and transcripts in a dose-dependent manner, but c9t11 had no effect. Immunoprecipitation / Western blot studies revealed that t10c12 inhibited HRG-β-stimulated phosphorylation of ErbB3, recruitment of the p85 subunit of phosphoinositide 3 -kinase (PI3K) to ErbB3, ErbB3-associated PI3K activities, and phosph orylation of Akt. However, c9t11 had no effect on phospho Akt levels. Neither t10c12 nor c9t11 had any effect on HRG-β-induced phosphorylation of ERK-1/2. CONCLUSION: These results that the inhibition that HT-29 cell growth by t10c12 may be induced via its modulation of ErbB3 signaling leading to inhibition of Akt activation.