RESUMEN
OBJECTIVES: Rapamycin inhibits products of molecular pathways in esophageal squamous cell carcinoma and limits tumor cell growth by targeting 4E-BP1- and eIF4E-dependent gene translation. In this study, we investigate the influence of 4E-BP1-to-eIF4E ratio on rapamycin response in esophageal squamous cell carcinoma cells, and the underlying mechanism is discussed. METHODS: The response to rapamycin treatment was examined in 6 esophageal cancer cell lines. Adjustment of the 4E-BP1/eIF4E ratio was carried out by knockdown or overexpression of 4E-BP1 and eIF4E. The relationship between Egr-1 and 4E-BP1 expression in esophageal cancer cells was also studied. RESULTS: The 4E-BP1/eIF4E ratio was adjusted to evaluate the response to rapamycin treatment in TE1 and TE2 esophageal cancer cells. TE2 cells are sensitized to rapamycin treatment after overexpression of 4E-BP1 or knockdown of eIF4E; TE1 cells become resistant to rapamycin after knockdown of 4E-BP1 or overexpression of eIF4E. These data suggest that the 4E-BP1/eIF4E ratio is a determinant for the response of TE1 and TE2 cells to rapamycin treatment. Egr-1 expression was higher in TE2 cells compared with other esophageal cancer cell lines, and its knockdown increased 4E-BP1 expression in TE2 cells, which became sensitive to rapamycin treatment. CONCLUSIONS: The 4E-BP1/eIF4E ratio is a determinant of the response of rapamycin treatment in esophageal cancer cells. Egr-1 can reduce 4E-BP1 gene expression and render esophageal squamous cell carcinoma cells resistant to rapamycin with a relatively low 4E-BP1/eIF4E ratio. Thus, the 4E-BP1/eIF4E ratio may represent a therapeutic index for the prediction of clinical outcome of rapamycin treatment in patients with esophageal squamous cell carcinoma.
Asunto(s)
Proteínas Adaptadoras Transductoras de Señales/metabolismo , Antineoplásicos/farmacología , Biomarcadores de Tumor/metabolismo , Carcinoma de Células Escamosas/metabolismo , Neoplasias Esofágicas/metabolismo , Factor 4F Eucariótico de Iniciación/metabolismo , Fosfoproteínas/metabolismo , Sirolimus/farmacología , Proteínas Adaptadoras Transductoras de Señales/genética , Biomarcadores de Tumor/genética , Carcinoma de Células Escamosas/genética , Carcinoma de Células Escamosas/patología , Proteínas de Ciclo Celular , Línea Celular Tumoral , Relación Dosis-Respuesta a Droga , Proteína 1 de la Respuesta de Crecimiento Precoz/genética , Proteína 1 de la Respuesta de Crecimiento Precoz/metabolismo , Neoplasias Esofágicas/genética , Neoplasias Esofágicas/patología , Carcinoma de Células Escamosas de Esófago , Factor 4F Eucariótico de Iniciación/genética , Regulación Neoplásica de la Expresión Génica , Humanos , Fosfoproteínas/genética , Interferencia de ARN , Transducción de Señal/efectos de los fármacos , TransfecciónRESUMEN
Norcantharidin (NCTD) is a small-molecule metastasis inhibitor without renal toxicity derived from a renal toxic compound cantharidin, which is found in blister beetles (Mylabris phalerata Pall.), commonly used in traditional Chinese medicine. The anti-metastatic capacity of NCTD is apparently through the downexpression of matrix metalloproteinase-9 (MMP-9) activity. The aim of this study was to clarify the transcriptional regulation of MMP-9 gene by NCTD in colorectal cancer CT-26 cells. NCTD not only downregulated MMP-9 mRNA and protein expression, but also inhibited gelatinase activity in a concentration- and time-dependent manner. In CT26 cells with transfection of cis-element reporter plasmids, NCTD treatment decreased reporter luciferase activity from a Sp1 construct, augmented with a NF-kappaB construct, but this did not occur with an AP-1 construct. Further transfecting with constructs containing wild-type or various mutant MMP-9 promoters in CT26 cells indicated that Sp1, but not the others, was required for NCTD-inhibition of MMP-9 promoter transactivation. More evidence by electrophoretic mobility shift assay demonstrated that NCTD inhibited the DNA-binding activity of Sp1. In addition, the increase effect of NF-kappaB-luciferase activity by NCTD may include the upexpression of nuclear STAT1 and result in competitive suppression of NF-kappaB-binding activity in MMP-9 promoter. In conclusion, the metastasis inhibitor NCTD downregulates MMP-9 expression by inhibiting Sp1 transcriptional activity in colorectal cancer CT26 cells.
