OBJECTIVES: The occurrence of abnormal expression patterns in different types of cancer suggests that micro RNAs (miRNAs) may play an important role in tumorigenesis. The aim of this study was to examine the expression levels of miRNAs known to be associated with the regulation of the expression levels of the APC and K-ras, which are important in the development of colorectal cancer (CRC). METHODS: The expression levels of miR-27, miR-663, miR-217, miR-181d, APC and K-ras in the serum, tumor and adjacent tumor-free (healthy) tissues of the patients and serum of the healthy controls were investigated with qRT-PCR. RESULTS: Expression levels of miR-217, mR-181d, miR-663, miR-27 and K-ras were found to be higher in CRC tissues than in adjacent tumor-free tissues of the patients. In patient serum samples, miR-663 levels were statistically more elevated than in controls. In patient tumor tissues, miR-217, miR-181d and miR-27 expressions were found to be higher. CONCLUSIONS: Increased miR-181d and miR-217 expression levels are associated with increased K-ras expression in the tumor tissues, and the expression of K-ras, which takes part as an oncogene in the CRC development, might be regulated by these miRNAs (Tab. 4, Ref. 33).

Despite advances in diagnostic and therapeutic methods, gastrointestinal (GI) cancers have both a high incidence and a high mortality rate. In addition to surgery, chemotherapy and radiotherapy, novel modalities such as immunotherapy are increasingly used in the treatment of these cancers. However, the prognosis in GI cancers remains poor despite the availability of these treatments, which prompted the search for new prognostic and predictive markers. High-mobility group box-1 (HMGB1) is a non-histone DNA protein which is known as a nuclear transcription factor. The search for new therapeutic targets has also gained importance. In this review, the prognostic and predictive role of HMGB1 in gastrointestinal cancers will be discussed in light of current literature.