phytoestrogens and Carcinoma--Non-Small-Cell-Lung

Epidermal growth factor receptor (EGFR) activating mutations play crucial roles in the tumorigenesis of human non-small cell lung cancer (NSCLC). The mechanism regarding how EGFR signaling regulates myeloid cell leukemia sequence 1 (Mcl-1) protein stability and ubiquitination remains undefined.. MTS assay was used for natural product library screening. The effect of formononetin (Formo) on NSCLC cells was determined by MTS assay and soft agar assay. Molecular modeling was performed to analyze the potential different binding modes between Formo and EGFR WT or mutants. Mcl-1 protein level and the inhibitory effect of Formo on EGFR signaling were examined by immunoblot, in vitro kinase assay, in vitro pulldown and ATP competition assays, co-immunoprecipitation assay, ubiquitination analysis, in vivo xenograft model, and immunohistochemical staining.. Formo was identified as an EGFR inhibitor by a 98 commercially available natural product screening. Formo suppresses WT and mutant EGFR kinases activity in vitro, ex vivo, and in vivo. Molecular modeling indicates that Formo docks into the ATP-binding pocket of both WT and mutant EGFR. Formo inhibits EGFR-Akt signaling, which in turn activates GSK3β and promotes Mcl-1 phosphorylation in NSCLC cells. Treatment with Formo enhances the interaction between Mcl-1 and SCF. This study highlights the importance of promoting ubiquitination-dependent Mcl-1 turnover might be an alternative strategy to enhance the anti-tumor efficacy of EGFR-TKI.

Topics: Animals; Carcinoma, Non-Small-Cell Lung; Cell Line, Tumor; ErbB Receptors; Female; Humans; Isoflavones; Lung Neoplasms; Mice; Mice, Nude; Models, Molecular; Myeloid Cell Leukemia Sequence 1 Protein; Phytoestrogens

This study investigated the effects of a phytoestrogen-containing standardized soy extract (SSE) on the growth of nonsmall cell lung cancer (NSCLC; A549) xenografts in female athymic mice. Tumor-bearing mice received either sterile water or SSE [50 or 100 mg/(kg x d), per os], 5 d/wk, until the mean tumor weight in each group was at least 900 mg. Treatment with SSE reduced tumor growth in the high-dose group compared with control (P < 0.01); tumors in both treated groups had reduced proliferation and greater apoptosis compared with controls (P < 0.05). SSE treatment also induced diffuse central necrosis, reducing the viable tissue mass within the tumor. Whereas tumor levels of epidermal growth factor receptor were comparable in control and treated mice, the expression of phosphorylated protein kinase B (p-Akt) was lower in tumors of mice treated with 100 mg SSE/(kg x d) than in controls (P < 0.01). The protein level of phosphorylated mitogen-activated protein kinase also tended to be lower (P = 0.07) in this group than in controls. Estrogen receptor (ER)alpha and ERbeta were present in tumors, but their expression levels did not differ among groups. Serum insulin-like growth factor-1 concentrations also were not affected by the treatments. In conclusion, we found that soy phytochemicals slow the in vivo growth of NSCLC xenografts; the modulation of the Akt-signaling pathway observed in tumors of SSE-treated mice may have a role in the activity observed. Our research provides further support for the concept that consumption of phytoestrogens may be effective in delaying lung cancer progression.

Topics: Animals; Apoptosis; Carcinoma, Non-Small-Cell Lung; Cell Line, Tumor; Female; Glycine max; Humans; Ki-67 Antigen; Lung Neoplasms; MAP Kinase Signaling System; Mice; Mice, Nude; Neoplasm Transplantation; Phytoestrogens; Plant Extracts; Receptors, Estrogen; Transplantation, Heterologous