Gap junction composed of connexin43 modulates 5­fluorouracil, oxaliplatin and irinotecan resistance on colorectal cancers.

Chemotherapy is one of the most commonly used therapeutic strategies for metastatic colon cancer. However, the development of resistance to chemotherapeutic agents limits their application in clinical use. The underlying mechanisms of this resistance development require further elucidation. The current study investigated the effects of connexin43 (Cx43) gap junctions on 5­fluorouracil (5­FU), oxaliplatin and irinotecan in colon cancer cells. Three different methods were used to manipulate Cx43 gap junction function: i) Cell culture at different densities; ii) pretreatment with a Cx43 specific inhibitor or enhancer; and iii) Cx43 gene knock­down. Results indicated that the cell toxicity of 5­FU, oxaliplatin and irinotecan was cell density­dependent, which was mediated by gap junctions. Downregulation of Cx43 gap junction functioning attenuated 5­FU, oxaliplatin and irinotecan toxicity in colon cancer cells, which was increased in cells treated with a Cx43 gap junction function enhancer. Thus, the results of the present study suggest that resistance to 5­FU, oxaliplatin and irinotecan in colon cancer cells was relative to Cx43 expression loss as cancer developed, which may indicate a novel basis for therapeutic strategy development to combat drug resistance in numerous cell types, in addition to colon cancer cells.

[Expression of Rictor and mTOR in colorectal cancer and their clinical significance].

OBJECTIVE: To explore the expression of Rictor and mTOR in the colorectal cancer and their clinical significance. METHODS: The expression levels of Rictor and mTOR in HCT116, SW480, LoVo and HCoEpiC cells were detected by indirect immunofluorescence and Western blotting. Sixty-two paraffin-embedded surgical specimens of colorectal cancer tissue and adjacent tissues were examined for Rictor expression using immunohistochemistry. The association of the expression levels of Rictor protein with the clinicopathologic features and the overall survival of the patients was analyzed. RESULTS: The expression level of Rictor was significantly higher in colorectal cancer tissues than in the adjacent tissues (P<0.05). The expression levels of Rictor and mTOR in the colon cancer cell lines were higher than those in human normal colon epithelial cell line HCoEpiC. The expression of Rictor was correlated with Dukes stage and lymphatic metastasis of the tumors but not with other clinicopathological parameter (P>0.05). Patients with Rictor expression had a lower overall survival rate than those without Rictor expression. CONCLUSION: Rictor overexpression is associated with the carcinogenesis and progression of colorectal cancer and can be an independent indicator for evaluating the prognosis of colorectal cancer patients.

[Clinical application of 64-slice computed tomographic angiography-based virtual colonoscopy in the diagnosis of colonic tumors].

OBJECTIVE: To investigate the clinical value of 64-slice computed tomographic angiography (CTA)-based virtual colonoscopy in the diagnosis of colonic tumors. METHODS: Philips/Brilliance 64 CT volumetric scanning was performed in 8 patients with colonic cancer and 2 with colonic polypi identified by postoperative pathological examination. Mimics software was used for surface rendering of the intestine with the Marching Cubes algorithm for 3-dimensional (3D) virtual endoscope (VE) reconstruction and CTA-based 3D reconstruction of the large intestine and the surrounding structures. The location, volume and appearance of the lesions displayed by the virtual techniques were compared with the pathological results. RESULTS: The 3D reconstruction was successfully completed in all the 10 cases, and the imaging diagnoses showed a total match with the pathological diagnoses. No significant differences were found between virtual endoscopy and CT virtual endoscopy. Virtual colonoscopy combined with digital model reconstruction provided valuable information for accurate identification of the position of the lesions and the complex adjacent anatomical structures. CONCLUSION: Virtual colonoscopy based on 64-slice CTA, when combined with 3D reconstruction technique, allows accurate display of the colonic lesions and potential metastasis, which can be crucial for clinical staging and surgical planning of colonic cancer.