Retinoblastoma binding protein 6 (RBBP6) plays an important role in chaperone-mediated ubiquitination and interacts with TP53 in carcinogenesis. However, the clinicopathologic significance of RBBP6 expression in colon cancer is unknown; in particular, the prognostic value of RBBP6 combined with TP53 expression has not been explored. Therefore, quantitative real-time PCR and western blot analyses were performed to detect RBBP6 expression in colon cancer tissues. RBBP6 and TP53 expression were assessed by immunohistochemistry in a tissue microarray format, in which the primary colon cancer tissue was paired with noncancerous tissue. Tissue specimens were obtained from 203 patients. We found that RBBP6 was overexpressed in colon tumorous tissues and was significantly associated with clinical stage, depth of tumor invasion, lymph node metastasis (LNM), distant metastasis, and histologic grade. Further studies revealed that a corresponding correlation between RBBP6 overexpression and mutant TP53 was evident in colon cancer (r = 0.450; P<0.001). RBBP6 expression was an independent prognostic factor for overall survival (OS) and disease free survival (DFS). Interestingly, patients with tumors that had both RBBP6 overexpression and mutant TP53 protein accumulation relapsed and died within a significantly short period after surgery (P<0.001). Multivariate analysis showed that patients with LNM and patients with both RBBP6- and TP53-positive tumors had extremely poor OS (HR 6.75; 95% CI 2.63–17.35; P<0.001) and DFS (HR 8.08; 95% CI 2.80–23.30; P<0.001). These clinical findings indicate that the assessment of both RBBP6 and mutant TP53 expression will be helpful in predicting colon cancer prognosis.

BackgroundKinesins play a key role in the development and progression of many human cancers. The present study investigated the expression and clinical significance of kinesin family member 26B (KIF26B) in colorectal cancer (CRC).MethodsUsing quantitative real-time PCR and Western blot analyses as well as immunohistochemical staining of a tissue microarray we examined KIF26B mRNA and protein levels in CRC tumor tissues and paired adjacent normal mucosa. Moreover, the effect of KIF26B knockdown on CRC cell proliferation was investigated using Cell Counting Kit-8 assays.ResultsExpression of KIF26B was found to be elevated in CRC. Suppression of KIF26B inhibited CRC cell proliferation. Furthermore, upregulated expression of KIF26B was significantly correlated with tumor size (P = 0.020), American Joint Committee on Cancer (AJCC) stage (P = 0.018), T stage (P = 0.026), N stage (P = 0.013), and differentiation histology (P = 0.047). KIF26B was also shown to be an independent prognostic indicator of overall survival for CRC patients (HR 5.621; 95% CI 2.302–13.730; P < 0.001).ConclusionOur data indicate that KIF26B plays an important role in colorectal carcinogenesis and functions as a novel prognostic indicator and a potential therapeutic target for CRC.

p21-Activated kinase 6 (PAK6) has been implicated in radiotherapy and docetaxel resistance. We have further evaluated PAK6 as a predictor of 5-fluorouracil (5-FU) treatment response in colon cancer. Here we report that in colon cancer PAK6 promotes tumor progression and chemoresistance both in vitro and in vivo. In the clinical analysis, PAK6 was overexpressed in 104 of 147 (70.75%) stage II and III patients who received 5-FU based chemotherapy after surgery. Multivariate Cox regression analysis indicated that PAK6 was an independent prognostic factor for overall survival (P < 0.001) and disease-free survival (P < 0.001). Colon cancer cell lines showed increased PAK6 expression upon 5-FU treatment. In PAK6-knockdown cells treated with 5-FU, cell viability and phosphorylation of BAD decreased, and the number of apoptotic cells, levels of cleaved caspase 3 and PARP increased compared to control cells. The opposite was observed in PAK6 overexpressing cells. Short hairpin RNA knockdown of PAK6 blocked cells in G2-M phase. Furthermore, Animal experiments results in vivo are consistent with outcomes in vitro. This study demonstrates that PAK6 is an independent prognostic factor for adjuvant 5-FU-based chemotherapy in patients with stage II and stage III colon cancer.

Zinc-α-2-glycoprotein (AZGP1) is a 41-kDa secreted glycoprotein, which has been detected in several malignancies. The diagnostic value of AZGP1 in serum of prostate and breast cancer patients has been reported. Analyzing “The Cancer Genome Atlas” data, we found that in colon cancer AZGP1 gene expression was upregulated at transcriptional level. We hypothesized that AZGP1 could be used as a diagnostic marker of colon cancer. First, we confirmed AZGP1 expression was higher in a set of 28 tumor tissues than in normal colonic mucosa tissues by real-time quantitative PCR and western blot in a Chinese population. We verified that serum concentration of AZGP1 was higher in 120 colon cancer patients compared with 40 healthy controls by ELISA (p < 0.001). Then receiver-operating characteristic (ROC) curve analysis was used to evaluate the predictive diagnostic value of AZGP1 in serum. The area under the curve (AUC) of AZGP1 was 0.742 (p < 0.001, 95% confidence interval (CI) = 0.656–0.827) in between the AUC of carcinoembryonic antigen (CEA) and the AUC of CA19-9, suggesting that predictive diagnostic value of AZGP1 is between CEA and Carbohydrate 19-9 (CA19-9). The combination of AZGP1 with traditional serum biomarkers, CEA and CA19-9, could result in better diagnostic results. To further validate the diagnostic value of AZGP1, a tissue microarray containing 190 samples of primary colon cancer tissue paired with normal colonic tissue was analysed and the result showed that AZGP1 was significantly upregulated in 68.4% (130 of 190) of the primary cancer lesions. In contrast, there was a weakly positive staining in 29.5% (56 of 190) of the normal colonic tissue samples (p < 0.001). Leave-one-out cross-validation was performed on the serum data, and showed that the diagnostic value of AZGP1 had 63.3% sensitivity and 65.0% specificity. Combination of AZGP1, CEA and CA19-9 had improved diagnosis value accuracy with 74.2% sensitivity and 72.5% specificity. These results suggest that AZGP1 is a useful diagnostic biomarker in tissues and serum from a Chinese population.