CCND1 As An Unfavorable Factor Mediates MiR-340 Suppression Of Chemotherapy Resistance For 5-Fu In Colon Adenocarcinoma

Background and Objection:Colorectal cancer (CRC), also known as colon cancer, rectal cancer or bowel cancer, is one of the most common malignant gastrointestinal carcinomas with a rising morbidity and mortality. CR C always occurs in the rectum and sigmoid colon junction, with a high-risk of age from 40 to 50 years old, and male vs female incidence ratio is 2 to 3:1. According to -A Cancer Journal for Clinicians, the highest impact factor Journal in the world, recently released 2015 China cancer statistics which indicated that colon cancer is one of the most common tumors of Chinese and became a serious threat to human health. According to histopathologic type, colon cancer is divided into adenocarcinoma (including papillary adenocarcinoma, mucinous adenocarcinoma, tubular adenocarcinoma), squamous carcinoma, squamous cell carcinoma and undifferentiated carcinoma. Early tumor is confined to mucosa or submucosa which is easy to cure and has more than 80% 5-year survival rate, while patients with advanced colon cancer because of organ involvement and lymph node metastasis, have less than 50% 5-year survival rate.Cyclin D1 (CCND1) belongs to the highly conserved cyclin family, whose members are characterized by a dramatic periodicity in protein abundance throughout the cell cycle. In the previous studies, increased CCND1 expression has been frequently found in a variety of tumors including epithelial liver cancer, ovarian cancer, nasopharyngeal carcinoma, gastric cancer, and lung cancer and may contribute to tumorigenesis. In previous study, CCND1 was observed to be co-existed with VEGF indicating poorer disease-free survival rates and overall survival rates in colorectal cancer. Furthermore, it was also found to be positive correlation with P-Stat5 expression, which was associated with shorter survival in patients with colorectal cancer. However, the expression pattern of CCND1 and its correlation with clinical features including prognosis were seldom reported in colon carcinoma alone.MicroRNAs (miRs) are a class of small noncoding RNAs involved in cell homeostasis and carcinogenesis. MicroRNA deregulation is frequent in human colorectal cancers, but little is known whether it represents a bystander event or actually drives tumor progression in vivo. miR-340 is a tumor-inhibitory miRNAs that has been documents in some tumors. Furthermore, it can reverse cisplatin resistance of hepatocellular carcinoma cell lines by targeting Nrf2-dependent antioxidant pathway. However, whether miR-340 induced chemotherapy sensitivity of 5-Fu to tumor cells was never been reported.In this study, we investigated the expression pattern of CCND1 in colon cancer tissues in mRNA and protein levels and evaluated the correlation of its nuclear expression with clinicopathologic features and patient survival. Our results hint CCND1 as an unfavorable prognostic factor promoting the pathogenesis of colon cancer patients.In this investigation, we explored the expression of CCND1 and its correlation between nuclear expression of CCND1 and clinicopathologic features including survival prognosis in colon adenocarcinoma (CRC). Further, we investigated CCND1 as a target of miR-340 participating miR-340-induced inhibition of chemotherapy resistance for 5-Fu in CRCMethods and materials:The mRNA and protein expression of CCND1 was examined by real-time PCR,western blot, and immunohistochemistry between CRC tissues and colon tissues. The relationship between the nuclear expression levels of CCND1 and clinical features including survival prognosis was analyzed. Further, siCCNDl or miR-340-induced chemotherapy sensitivity to CRC was respectively investigated. Finally, CCND1 as a direct target of miR-340 in CRC was examined.Results:The mRNA levels of CCND1 was markedly greater in CRC tissues than their pair colon tissues(P=0.0017). Further, elevated CCND1 protein expression was indicated in cell nucleus of CRC tissues compared to colon tissues. High levels of CCND1 nuclear protein were positively correlated with T stage (P<0.001) of CRC patients. Patients with higher CCND1 nuclear expression had a significantly shorter overall survival time than did patients with low CCND1 nuclear expression. Multivariate analysis indicated CCND1 nuclear expression as an independent prognostic indicator (P=0.004) for the survival of patients with CRC. Knocking down CCND1 could inhibit cell proliferation, invasion and migration in CRC cell lines. Furthermore, suppression of CCND1 or miR-340 significantly decreased chemotherapy sensitivity of 5-Fu to CRC cells. Finally, CCND1 was validated as a direct target of miR-340 in CRC.ConclusionCCND1 as an unfavorable factor mediates miR-340 suppression of chemotherapy resistance for 5-Fu in CRC.