Non-coding RNAs in colorectal cancer metastases

Colorectal cancer is one of the most common diagnosed human cancers. Surgery of the primary tumor is the treatment of choice in localized stages with the aim of curative chances. Although several patients are cured by this treatment modality, some of them develop metastatic disease or are diagnosed with metastatic colorectal cancer. Once metastasized, colorectal cancer represents an incurable disease in most patients. Therefore, the identification of the molecular mechanisms that drive and maintain metastatic disease might enable a better understanding of the pathogenesis of colorectal cancer, a better risk-stratification of patients with localized disease who are at high risk for the development of metastases and identification of novel drug targets for metastatic colorectal cancer. For three decades, alterations of protein-coding oncogenes and tumor suppressors genes have been considered as the causes of tumorigenesis. Recent advances proved without doubts that cancer is a complex genetic disease involving structural and expression abnormalities of both coding and non-coding genes. Recently, the idea that small non-coding RNAs (ncRNAs) named microRNAs (miRNAs) and other larger ncRNAs named ultraconserved genes (ncUCGs) are involved in human tumorigenesis was proven. The central hypothesis of this Max Kade proposal is that during the colorectal tumorigenesis, genome-wide abnormalities in both ncRNAs and EST messengers of protein coding genes (PCGs) occur in a correlated way and that the transcriptional or post- transcriptional down-regulation of targets levels by ncRNAs may have functional consequences by impairing cellular mechanisms including invasion and metastatic spread. The broad, long-term purpose of this application is to decipher the roles of ncRNAs during the development of metastases in colorectal cancer. To achieve this, we will use a three-aimed strategy. First, based on genome-wide microarray experiments involving miRNA and ncUCG profiling and on bioinformatics studies, we will produce data about miRNAs and ncUCGs expression in metatastic and non-metastatic CRC. Second, based on the negative correlations that we will found using bioinformatics tools, we will analyze the possible interactions between miRNAs and UCGs, as well as between miRNAs and predicted target messenger RNA of PCGs significant for metastatic process in CRC. Third, the proved interactor pairs will be tested in vivo in CRC cells and in vivo animal models for biological effects, including apoptosis, proliferation, invasion and metastatic spread. The final results of the described tasks will reveal new markers for molecular diagnosis and prognosis and new targets for miRNA-based drug therapy.

Non-coding RNAs are molecules of different size and recently published data are indicating that non-coding RNAs play a significant role in physiological and pathological processes including cancer. Per definition, non-coding RNAs can be subdivided according to their size: Short non-coding RNAs (<200 nucleotides) and long non-coding RNAs (>200 nucleotides). One of the most prominent functions of non-coding RNA is the regulation of protein-coding gene expression. Non-coding RNAs are influencing all hallmarks of cancer and are involved in all types of cancer. As a result of this project, I could identify novel functions of non-coding RNAs in colorectal cancer which shed new light on the underlying pathology of this type of cancer. In more detail, microRNA-200a has been identified as a factor regulating the epithelial- mesenchymal transition (EMT) in colorectal cancer. EMT is a well-known process in which cancer cells acquire the capability to migrate and invade to the surrounding tissue, with the final consequence of establishing distant metastases in different organs. In our work we demonstrated that microRNA-200a influences the EMT program in colorectal cancer and that low levels of microRNA-200a are associated poor patient survival. In addition, we identified and characterized a novel long non-coding RNA called N-BLR, which interacts with family members of microRNA-200 and regulate cancer cell migration, invasion and metastases. As shown by our group, also microRNA-96, another short non-coding RNA, influences cellular growth of colorectal cancer cells by influencing cell cycle relevant genes. We could also show that spinophilin, a protein-coding gene, regulates colorectal cancer cell proliferation and stem cell formation, and whose expression is associated with patients clinical outcome. These discoveries might be helpful in establishing novel prognostic biomarkers for better patient stratification and highlights some molecules as potential drug targets in colorectal cancer.