The anaphase-promoting complex (APC) is a multiprotein complex with E3 ubiquitin ligase activity and is required for ubiquitination of securin and cyclin-B. Several APC-targeting molecules are reported to be oncogenes. Dysregulation of APC may be associated with tumorigenesis. This study examines the relationship between APC expression and clinicopathological factors and evaluates the possibility of an aberrant APC function in colorectal carcinomas (CRCs).
To determine whether the loss of APC7 expression is related to tumorigenesis, we used tissue micro-arrays in 114 resected CRCs to scrutinize the expressions of APC7 and Ki-67 immunohistochemistry and to find relations with clinocopathologic parameters. The expression of APC7 was defined as positive for summed scores of staining intensities from 0 to 3+.
Forty-four cases (67.7%) of colon cancer and 38 cases (77.6%) of rectal cancer showed immunopositive reactions to APC. The grade of APC expression was not statistically correlated with tumor location, age, T or TNM stage, or differentiation. However, the expression of APC did correlate with the expression of Ki-67 and to the tumor recurrent. Higher APC expression showed the better 5-year overall survival rate in 74% of grades 2, 3 groups (high expression) than 57% of grades 0, 1 groups (lower expression) respectively (P = 0.042).
Positive APC expression may be a good prognostic factor for patients with CRC, and the loss of APC expression in tumor tissue may be related with the risk for recurrence and a poor survival rate compared to high APC expression. Further study of APC in controlling the cell cycle as aberrant function in CRC is needed.
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Oral capecitabine has been used as adjuvant therapy for colorectal cancer patients since the 1990s. Patient-initiated cessation or reduced use of capecitabine occurs widely for various reasons, yet the consequences of these actions are unclear. The present study sought to clarify treatment outcomes in such patients.
The study included 173 patients who had been diagnosed with stage II or III colon cancer according to the pathologic report after radical surgery at Samsung Medical Center from May 2005 to June 2007 and who had received capecitabine as adjuvant therapy. The patients were divided into groups according to whether the dose was reduced (I, dose maintenance; II, dose reduction) or stopped (A, cycle completion; B, cycle cessation). Recurrence and disease-free survival rates between the two groups each were analyzed.
Of the 173 patients, 128 (74.6%) experienced complications, most frequently hand-foot syndrome (n = 114). Reduction (n = 35) or cessation (n = 18) of medication was most commonly due to complications. Concerning reduced dosage, both groups displayed no statistically significant differences in recurrence rate and 3-year disease-free survival rate. Concerning discontinued medication use, the cycle completion group showed an improved recurrence rate (P = 0.048) and 3-year disease-free survival rate (P = 0.028).
The results demonstrate that maintaining compliance with capecitabine as an adjuvant treatment for colon cancer to preventing complications positively affects patient prognosis.
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Evidence that indicates bile acid is a promoter of colon cancer exists. Deoxycholic acid (DCA) modifies apoptosis or proliferation by affecting intracellular signaling and gene expression. However, because previous studies have been based on studies on colon cancer cell lines, the effect of DCA on normal colonocytes is unknown.
Normal colonocytes and Caco-2 and HCT116 cells were treated with 20 µM and 250 µM of DCA, and the effect of different concentrations of DCA was measured based on the expression of cell-cycle-related proteins by using Western blots.
The expressions of CDK2 and cyclin D1 for different concentrations of DCA in normal colonocytes and colon cancer cells were similar, but the expressions of cyclin E and A were significantly different. In HCT116 colon cancer cells, the expression of cyclin E increased regardless of the DCA concentration, but in normal colonocytes and Caco-2 cells, the expression of cyclin E was not changed or decreased. In HCT116 colon cancer cells, the expression of cyclin A was not changed or decreased regardless of the DCA concentration, but in normal colonocytes and Caco-2 cells, the expression of cyclin A was increased at a DCA concentration of 20 µM.
The effect of DCA on stimulating cell proliferation suggests that DNA synthesis is stimulated by an increased expression of cyclin E in colon cancer cells. Our results suggest that a low dose of DCA induces cellular proliferation through increased expression of cyclin A and that a high dose of DCA induces decreased expression of cyclin E and CDK2 in normal colonocytes.
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