This work presents CoreKB, a Web platform for searching reliable facts over gene expression-cancer associations Knowledge Base (KB). It provides search capabilities over an RDF graph using natural language queries, structured facets, and autocomplete. CoreKB is designed to be intuitive and easy to use for healthcare professionals, medical researchers, and clinicians. The system offers the user a comprehensive overview of the scientific evidence supporting a medical fact. It provides a quantitative comparison between the possible gene-cancer associations a particular fact can reflect.