Abstract. Colon cancer is one of the most frequently diagnosed cancer and the third most fatal malignancy worldwide. HOTAIR, a cancer-associated long non-coding RNA (lncRNA), is a powerful biomarker of metastasis and poor prognosis in a diverse group of cancers. Nevertheless, an understanding of how HOTAIR is involved in colon cancer progression is limited. In the present study, we hypothesized that HOTAIR plays a crucial role in colon cancer development. We evaluated the expression of HOTAIR in 120 colon cancer samples, matched adjacent non-tumor mucosa and 32 lymph node metastasis tissues by real-time PCR. Increased HOTAIR expression was significantly correlated with the depth of tumor invasion, lymph node metastasis, organ metastasis, histological differentiation, vascular invasion and advanced tumor stage. Patients with high HOTAIR expression had higher recurrence rates and reduced metastasis-free and overall survival than patients with low HOTAIR expression. Moreover, our findings revealed that HOTAIR had a limited effect on cell proliferation but significantly promoted colon cancer cell migration and invasion in vitro. Depletion of HOTAIR increased the expression of E-cadherin while concomitantly decreasing expression of vimentin and MMP9. Hence, HOTAIR may be another pleiotropic modulator participating in epithelial-mesenchymal transition (EMT). These results indicate that HOTAIR may also be a valuable predictor for colon cancer management; furthermore, this lncRNA may be a potential target for cancer prevention and treatment.

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Previous studies have implicated autophagy in osteoclast differentiation. The aim of this study was to investigate the potential role of p62, a characterized adaptor protein for autophagy, in RANKL-induced osteoclastogenesis. Real-time quantitative PCR and western blot analyses were used to evaluate the expression levels of autophagy-related markers during RANKL-induced osteoclastogenesis in mouse macrophage-like RAW264.7 cells. Meanwhile, the potential relationship between p62/LC3 localization and F-actin ring formation was tested using double-labeling immunofluorescence. Then, the expression of p62 in RAW264.7 cells was knocked down using small-interfering RNA (siRNA), followed by detecting its influence on RANKL-induced autophagy activation, osteoclast differentiation, and F-actin ring formation. The data showed that several key autophagy-related markers including p62 were significantly altered during RANKL-induced osteoclast differentiation. In addition, the expression and localization of p62 showed negative correlation with LC3 accumulation and F-actin ring formation, as demonstrated by western blot and immunofluorescence analyses, respectively. Importantly, the knockdown of p62 obviously attenuated RANKL-induced expression of autophagy- and osteoclastogenesis-related genes, formation of TRAP-positive multinuclear cells, accumulation of LC3, as well as formation of F-actin ring. Our study indicates that p62 may play essential roles in RANKL-induced autophagy and osteoclastogenesis, which may help to develop a novel therapeutic strategy against osteoclastogenesis-related diseases.

Cullin 4B (CUL4B), a scaffold protein of the Cullin4B-RING E3 ligase complex, functions in proteolysis. The present study aims to investigate its expression pattern and evaluate whether CUL4B expression was associated with histopathological and prognosis in the patients with colon cancer. Real-time PCR and western blot were used to identify CUL4B expression in tumor tissue and the paired adjacent normal mucosa from patients with colon cancer. Immunohistochemistry on a tissue microarray containing 203 cases of colon cancer was performed to analyze the association between CUL4B expression and clinicopathological features. Results indicated that CUL4B mRNA and protein levels in tumor tissues were both higher than that in normal mucosae (P < 0.001). Immunohistochemical study displayed that high CUL4B expression was significantly associated with the depth of tumor invasion, lymph node metastasis, distant metastasis, histological differentiation, vascular invasion, and advanced tumor stage. Patients with CUL4B-positive tumors had a higher recurrence rate and poorer survival than patients with CUL4B-negative tumors. In multivariate analyses, CUL4B expression was an independent factor for determining colon cancer prognosis after surgery. In conclusion, CUL4B might promote the progression of colon cancer and can be served as a novel independent prognostic marker for the prediction of recurrence in colon cancer.