miR-106a* inhibits the proliferation of esophageal carcinoma cells by targeting CDK2-associated Cullin 1 (CACUL1).

Previous studies suggest that aberrant microRNA expression is common in plenty of cancers. The expression of miR-106a* was decreased in follicular lymphoma, but the expression and functions of miR-106a* in esophageal carcinoma (EC) remain unclear. In this study, we explored the expression and anti-oncogenic roles of miR-106a* in human EC. The expression of miR-106a* is significantly decreased in EC tissues and EC cell lines. Overexpression of miR-106a* suppressed EC cell proliferation, clonogenicity, G1/S transition, and induced apoptosis in vitro, but inhibition of miR-106a* facilitated cell proliferation, clonogenicity, G1/S transition. Luciferase reporter assay results showed that CDK2-associated Cullin 1 (CACUL1) was a direct target of miR-106a* in EC cells. Moreover, silencing CACUL1 resulted in the same biologic effects of miR-106a* overexpression in EC cells, which included suppressed EC cell proliferation, clonogenicity, and blocked G1/S transition through CDK2 pathway by inhibiting cell cycle regulators (Cyclin A, Cyclin E). Our data indicate that miR-106a* might play an anti-oncogenic role in EC by regulating CACUL1 expression, which suggest miR-106a* as a new potential diagnostic and therapeutic target for EC.

Inhibition of microRNA-21 increases radiosensitivity of esophageal cancer cells through phosphatase and tensin homolog deleted on chromosome 10 activation.

The radioresistance of esophageal squamous cell carcinoma is a great obstacle to treatment. Although it has been demonstrated that microRNA-21 (miR-21) can act as an 'oncogene' in esophageal squamous cell carcinoma, its role in radioresistance remains unexplored. The aims of this study were to investigate the role of miR-21 in esophageal squamous carcinoma cells' radioresistance and to identify the possible mechanism. The relatively radioresistant esophageal squamous cancer TE-1 cells (TE-R60) was established by fractionated irradiation. By lentiviral transduction with miRZip-21, the miR-21 expression in TE-1 cells was stably downregulated, which was renamed as 'anti-miR-21 TE-1 cells.' The phosphatase and tensin homolog deleted on chromosome 10 (PTEN) was knocked down in anti-miR-21 TE-1 cells through short interfering RNA. The expression level of miR-21 and PTEN messenger RNA were measured by quantitative real-time reverse transcription polymerase chain reaction or reverse transcription polymerase chain reaction. The expression level of PTEN, phospho-Akt, and Akt protein were detected by Western blot. Clongenic assay was used to analyze the cells' radiosensitivity. miR-21 was overexpressed, and PTEN was suppressed in established radioresistant TE-R60 cells compared with the parent cells (1.3-fold and 70.83%). The inhibition of miR-21 significantly increased the cells' radiosensitivity (P < 0.05) and the PTEN protein expression (2.3-fold) in TE-1 cells. In addition, phospho-Akt protein, downstream target of PTEN, reduced significantly in anti-miR-21 TE-1 cells. Knockdown of PTEN in anti-miR-21 TE-1 cells could abrogate the miR-21 inhibition-induced radiosensitization (P < 0.05). Inhibition of miR-21 increased radiosensitivity of esophageal cancer TE-1 cells, and this effect was possibly through the activation of PTEN. Inhibition of miR-21 may form a novel therapeutic strategy to increase the radiosensitivity of esophageal cancer.

The radiosensitization effect of NS398 on esophageal cancer stem cell-like radioresistant cells.

This study aimed to investigate the cancer stem cell (CSC) properties of radioresistant esophageal cancer cells and the radiosensitization effect of NS398, a cyclooxygenase (COX)-2 inhibitor, on them. Fractionated irradiation was applied to acquire radioresistant esophageal cancer cells. Clone formation assay was employed to detect cell radiosensitivity and cloning formation ability. Cell viability was determined by methyl tetrazolium colorimetry assay. Cell cycle distribution and apoptosis were detected by flow cytometry. Tumorigenicity was investigated by xenograft tumorigenicity assay. Expression levels of ß-catenin were detected by reverse transcription polymerase chain reaction or Western blot. As results, radioresistant Eca109R50Gy cells were obtained through fractional irradiation from Eca109 cells; Eca109R50Gy cells displayed higher ability of proliferation, colony-formation, and 40 times tumorigenic ability as high as that of the Eca109 cells in vivo. Meantime stem cell marker ß-catenin was elevated in Eca109R50Gy cells. All of the above implied that Eca109R50Gy cells have some properties of CSCs. NS398 enhanced the radiosensitivity of Eca109R50Gy cells accompanied by down-regulating the expression of ß-catenin. In conclusion, radioresistant Eca109R50Gy cells carried some CSC-like properties; NS398 enhanced the radiosensitivity of CSC-like Eca109R50Gy cells and this function may partly through down-regulating the expression of ß-catenin. These findings both stress the important role of CSCs in esophageal cancer radioresistance and provide new insight on possible application of COX-2 inhibitors on CSCs.