Pongamol Inhibits Epithelial to Mesenchymal Transition Through Suppression of FAK/Akt-mTOR Signaling.

BACKGROUND/AIM: Cancer metastasis is the main cause of mortality in cancer patients. As lung cancer patients are mostly detected at metastatic stages, strategies that inhibit cancer metastasis may offer effective therapies. Activation of FAK and Akt/mTOR pathways promotes the highly metastatic phenotypes of epithelial to mesenchymal transition (EMT). We unraveled EMT inhibitory action of pongamol and the mechanism controlling cell dissemination in lung cancer cells. MATERIALS AND METHODS: Cytotoxic and antiproliferative effects of pongamol were determined by the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay. Apoptosis and necrosis induction in response to pongamol treatment was observed and visualized by nuclei staining assay. Wound healing migration, invasion, and anchorage-dependent growth assay were conducted to evaluate metastatic behaviors. EMT protein expression and FAK pathway were detected by western blot analysis. RESULTS: Pongamol at 0-100 µM exhibited significant inhibition on migration, and invasion of cancer cells. Regarding anoikis resistance potential, the compound significantly inhibited survival and growth of cancer cells in an anchorage-independent manner, as indicated by the depletion of growing colonies in pongamol-pretreated cells. Protein level analysis further showed that pongamol exerted its anti-metastasis effect by inhibiting EMT, as indicated by a decrease of several mesenchymal proteins (N-cadherin, vimentin, Snail, and Slug). Regarding the up-stream mechanisms, we found that pongamol inhibited activation of FAK and Akt/mTOR signaling pathways. CONCLUSION: Pongamol exhibits potent anti-metastatic activity through suppressing key potentiating factors of cancer metastasis EMT and FAK.

DS-1 Inhibits Migration and Invasion of Non-small-cell Lung Cancer Cells Through Suppression of Epithelial to Mesenchymal Transition and Integrin ß1/FAK Signaling.

BACKGROUND/AIM: Epithelial to mesenchymal transition (EMT), and focal adhesion kinase (FAK) facilitate lung cancer cell motility and survival. We, therefore, investigated the antimigratory effect of 3,4-dihydroxy-5,4'-dimethoxybibenzyl (DS-1) on human lung cancer cells. MATERIALS AND METHODS: Cell viability and proliferation were examined by the 3-[4,5-dimethylthiazole-2-yl]-2,5-diphenyltetrazolium bromide assay. Filopodia formation, migration, and anchorage-independent growth assays were performed to assess metastatic behaviors while EMT-related proteins, integrins, and FAK-RhoA pathway were evaluated by western blot analysis. RESULTS: We found that DS-1 significantly inhibited the proliferation of lung cancer cells compared to the control. The aggressive behavior of cancer cells, including migration and invasion, was significantly reduced by DS-1. Anchorage-independent growth analysis provided evidence that DS-1 suppressed the growth and survival of cancer cells in detached conditions as indicated by the significant reduction in size and number of colonies. With regard to the mechanisms involved, we found that DS-1-suppressed EMT, as indicated by the reduction of EMT markers, namely N-cadherin, SNAIL and SLUG, and increased levels of the epithelial marker, E-cadherin. In addition, DS-1 was shown to reduce the level of integrin ß1 protein and FAK activation. CONCLUSION: DS-1 suppressed lung cancer metastasis via suppressing EMT, integrin ß1 expression and FAK-related signaling.

Bibenzyl analogue DS-1 inhibits MDM2-mediated p53 degradation and sensitizes apoptosis in lung cancer cells.

BACKGROUND: Lung cancer is a leading fatal malignancy due to the high incidence of treatment failure. Dysfunction of the tumor suppressor p53 contributes to cancer initiation, progression, and therapeutic resistance. Targeting MDM2, a negative regulator of p53, has recently attracted interest in cancer drug research as it may restore tumor suppressive function. PURPOSE: The present study aimed to investigate the effect of 3,4-dihydroxy-5,4'-dimethoxybibenzyl (DS-1) on targeting MDM2 and restoring p53 function in lung cancer cells. METHODS: The efficacy of DS-1 alone or in combination with cisplatin in lung cancer cells was determined by MTT, nuclear staining, and annexin V/PI assay. The expression of apoptosis-related proteins was determined by western blot analysis. To evaluate the role of DS-1 on the stabilization and degradation of p53, cycloheximide chasing assay and immunoprecipitation were conducted, and the active form of p53 was investigated by immunofluorescent staining assay. To confirm and demonstrate the site interaction between DS-1 and the MDM2 protein, in silico computational analysis was performed. RESULTS: DS-1 exhibited a cytotoxic effect and sensitized lung cancer cells to cisplatin-induced apoptosis. DS-1 caused a significant increase in the cellular level of p53 protein, while the active form of p53 (phosphorylation at Ser15) was unaltered. DS-1 treatment in combination with cisplatin could enhance activated p-p53 (Ser15) and p53 downstream signaling (Bax, Bcl-2, and Akt), leading to a higher level of apoptosis. Immunoprecipitation analysis revealed that DS-1 decreased the p53-ubiquitin complex, a prerequisite step in p53 proteasomal degradation. Molecular docking simulation further evidenced that DS-1 interacts with MDM2 within the p53-binding domain by carbon-hydrogen bond interaction at Lys27, π-alkyl interactions at Ile37 and Leu30, and van der Waals interactions at Ile75, Val51, Val69, Phe67, Met38, Tyr43, Gly34, and Phe31. Treatment by DS-1 and cisplatin in patient-derivated primary lung cancer cells showed consistent effects by increasing cisplatin sensitivity. CONCLUSIONS: Our findings provide evidence that DS-1 is an MDM2 inhibitor and its underlying mechanism involves MDM2 binding and p53 induction, which may benefit the development of this compound for lung cancer treatment.