Luteolin enhances drug chemosensitivity by downregulating the FAK/PI3K/AKT pathway in paclitaxel­resistant esophageal squamous cell carcinoma.

Drug resistance is a key factor underlying the failure of tumor chemotherapy. It enhances the stem­like cell properties of cancer cells, tumor metastasis and relapse. Luteolin is a natural flavonoid with strong anti­tumor effects. However, the mechanism(s) by which luteolin protects against paclitaxel (PTX)­resistant cancer cell remains to be elucidated. The inhibitory effect of luteolin on the proliferation of EC1/PTX and EC1 cells was detected by cell counting kit­8 assay. Colony formation and flow cytometry assays were used to assess clonogenic capacity, cell cycle and apoptosis. Wound healing and Transwell invasion tests were used to investigate the effects of luteolin on the migration and invasion of EC1/PTX cells. Western blotting was used to detect the protein levels of EMT­related proteins and stem cell markers after sphere formation. Parental cells and drug­resistant cells were screened by high­throughput sequencing to detect the differential expression of RNA and differential genes. ELISA and western blotting were used to verify the screened PI3K/Akt signaling pathway, key proteins of which were explored by molecular docking. Hematoxylin and eosin staining and TUNEL staining were used to observe tumor xenografts on morphology and apoptosis in nude mice. The present study found that luteolin inhibited tumor resistance (inhibited proliferation, induced cell cycle arrest and apoptosis and hindered migration invasion, EMT and stem cell spherification) in vitro in PTX­resistant esophageal squamous cell carcinoma (ESCC) cells. In addition, luteolin enhanced drug sensitivity and promoted the apoptosis of drug­resistant ESCC cells in combination with PTX. Mechanistically, luteolin may inhibit the PI3K/AKT signaling pathway by binding to the active sites of focal adhesion kinase (FAK), Src and AKT. Notably, luteolin lowered the tumorigenic potential of PTX­resistant ESCC cells but did not show significant toxicity in vivo. Luteolin enhanced drug chemosensitivity by downregulating the FAK/PI3K/AKT pathway in PTX­resistant ESCC and could be a promising agent for the treatment of PTX­resistant ESCC cancers.

Development of a Novel Highly Spontaneous Metastatic Model of Esophageal Squamous Cell Carcinoma Using Renal Capsule Technology.

PURPOSE: Increasing evidence has demonstrated that animal models are imperative to investigate the potential molecular mechanism of metastasis and discover anti-metastasis drugs; however, efficient animal models to unveil the underlying mechanisms of metastasis in esophageal squamous cell carcinoma (ESCC) are limited. METHODS: ESCC cell EC9706 with high invasiveness was screened by repeated Transwell assays. Its biological characteristics were identified by flow cytometry as well as by the wound healing and CCK-8 assays. Besides, the levels of epithelial-mesenchymal transition-related markers were examined using Western blotting. Parental (EC9706-I0) and subpopulation (EC9706-I3) cells were employed to establish the renal capsule model. Next, the tumor growth was detected by a live animal imaging system, and hematoxylin and eosin staining was applied to evaluate the metastatic status in ESCC. RESULTS: EC9706-I3 cells showed rapid proliferation ability, S phase abundance, and high invasive ability; obvious upregulation in N-cadherin, Snail, Vimentin, and Bit1; and downregulation in E-cadherin. EC9706-I3 cells were less sensitive to the chemotherapy drug 5-fluorouracil than EC9706-I0 cells; however, both cell lines reached a tumorigenesis rate of 100% in the renal capsule model. The live animal imaging system revealed that the tumors derived from EC9706-I0 cells grew more slowly than those from EC9706-I3 cells at weeks 3-14. The EC9706-I3 xenograft model displayed a spontaneous metastatic site, including kidney, heart, liver, lung, pancreas, and spleen, with a distant metastatic rate of 80%. CONCLUSION: Our data suggested that the metastatic model was successfully established, providing a novel platform for further exploring the molecular mechanisms of metastasis in ESCC patients.

Preliminary evaluation for Bit1 as a potential biomarker for squamous cell carcinoma and adenocarcinoma of esophagus.

Mounting evidence has demonstrated that Bit1 has been investigated as an etiological factor for certain cancers, including esophageal squamous cell carcinoma reported in our previous study, but data regarding possible roles of Bit1 in esophageal squamous cell carcinoma and esophageal adenocarcinoma remain to be elucidated. The purpose of this study was to examine whether Bit1 can be a novel diagnostic marker for the patients with esophageal squamous cell carcinoma and esophageal adenocarcinoma. The results revealed that Bit1 level in esophageal squamous cell carcinoma was significantly higher than that in esophageal adenocarcinoma tissues ( p < 0.05); notably, Bit1 level in esophageal adenocarcinoma tissues was lower than that in paired normal tissues but no difference was found ( p > 0.05). Bit1 expression patterns were completely in accordance with matrix metalloproteinase 2 and Bcl-2 in esophageal squamous cell carcinoma and esophageal adenocarcinoma. In addition, Bit1, Bcl-2, and matrix metalloproteinase 2 expression patterns in different differentiated esophageal squamous cell carcinoma were higher than those in corresponding normal esophageal tissues. Bit1 expression in poorly differentiated esophageal squamous cell carcinoma was significantly higher than that in normal esophageal tissues ( p < 0.05) but not in moderately and well-differentiated esophageal squamous cell carcinoma. Matrix metalloproteinase 2 expression patterns in poorly and moderately differentiated esophageal squamous cell carcinoma were significantly higher than those in corresponding normal esophageal tissues ( p < 0.01) but not in well-differentiated esophageal squamous cell carcinoma tissue ( p > 0.05). Bcl-2 expression patterns in various differentiated esophageal squamous cell carcinoma were higher than those in corresponding normal esophageal tissues with no statistical differences ( p > 0.05). Importantly, Bit1 expression was positively correlated with both matrix metalloproteinase 2 and Bcl-2 expression in esophageal squamous cell carcinoma and esophageal adenocarcinoma tissues ( p < 0.05). Collectively, these preliminary data support further investigation of Bit1 as an important diagnostic factor for esophageal squamous cell carcinoma and esophageal adenocarcinoma.

Bit1 knockdown contributes to growth suppression as well as the decreases of migration and invasion abilities in esophageal squamous cell carcinoma via suppressing FAK-paxillin pathway.

BACKGROUND: There is growing evidence that Bit1 exerts different roles in the development and progression of human cancers. Although Bit1 was highly exhibited in ESCC tissues in our previous study, its roles and molecular mechanisms implicated in development and progression of ESCC remain unknown. METHODS: Bit1 protein expression in ESCC cell lines and normal esophageal epithelial cell was detected by Western blotting. Bit1 protein expression mediated by Bit1 shRNA was investigated by Western blotting. MTT, migration assay, invasion experiment, ELISA and Flow cytometry were utilized to determine the effects of Bit1 knockdown on cell proliferation, migration, invasion and apoptosis, respectively. A xenograft model was used to examine in vivo tumourigenicity, and immunohistochemistry and TUNEL were utilized to evaluate the related protein expression and apoptosis. Gene microarray was determined by Agilent SurePrint G3 Human GE 8 × 60 K Microarray, the interaction of Bit1 and FAK proteins were detected by Immunoprecipitation and the key protein expressions of FAK-paxillin pathway were detected by Western blotting. RESULTS: We found Bit1 expression in all human ESCC cell lines tested was significantly higher than that in normal esophageal epithelial cell Het-1A (P < 0.05), in which EC9706 presented the highest Bit1 level. Bit1 protein level was significantly downregulated at day 1 after transfection with specific shRNA against Bit1 (P < 0.05). At days 2 and 3, Bit1 level reached the lowest value after transfection with Bit1 shRNA. Moreover, Bit1 depletion contributed to growth inhibition in vitro and in vivo, reduced cell migration and invasion abilities, and induced cell apoptosis in EC9706 and TE1 cells. More importantly, Bit1 downregulation significantly lowered Bcl-2 and MMP-2 levels in EC9706 xenografted tumor tissues, meanwhile triggered apoptosis after treatment with different doses of Bit1 shRNA. Further gene microarray revealed that 23 genes in Bit1-RNAi group were markedly downregulated, whereas 16 genes were obviously upregulated. Notably, Bit1 intrinsically interacted with FAK protein in EC9706 cells. Moreover, paxillin was downregulated at mRNA and protein levels in Bit1 shRNA group, coupled with the decreases of FAK mRNA and protein expressions. CONCLUSION: Bit1 may be an important regulator in cell growth, apoptosis, migration and invasion of ESCC via targeting FAK-paxillin pathway, and thereby combinative manipulation of Bit1 and FAK-paxillin pathway may be the novel and promising therapeutic targets for the patients with ESCC.