MicroRNA expression in colorectal cancer

Colorectal cancer is a common disease entity with a multi-factorial aetiology which remains poorly understood. It is estimated that in 2008, colorectal cancer was responsible for 8% of all cancer deaths, making it the fourth most common cause of death from cancer [10]. Prognosis is heavily linked to stage at diagnosis. The major cause of death is development of metastasis in liver, abdominal lymph nodes,and lung, forwhich there is no cure [21]. According to the most recently defined American Joint Committee on Cancer (AJCC) system for colonic adenocarcinoma, 5-year stage-specific survivals were 93.2% for stage I disease compared with 8.1% for stage IV [34], highlighting a need for novel early detection strategies. Colorectal cancer, at least theoretically, is a disease entity which is amenable to early detection, since it exhibits a stepwise progression of carcinogenesis from benign polyps to adenocarcinoma, over a period of time. The majority of national screening programmes currently centre on the use of colonoscopy or faecal immunohistochemistry/occult blood testing. Colonoscopy is an expensive, invasive procedure which carries a significant risk of intestinal perforation (1:700). Faecal testing ismore cost effective and less invasive but sacrifices sensitivity and specificity. Carcinoembryonic antigen, the only blood test currently available, exhibits low sensitivity and specificity. Hence, there is great need for new biomarkers for early detection of CRC.