Micrornas in the malignant transformation process

Many cancers originate as benign neoplasms that transform into malignant cancerous tumors in a multistep progression that is regulated, in part, by microRNAs. Benign neoplasms, by defi nition, lack the ability to invade adjacent tissues or spread to distant sites through metastasis. The benign to malignant transition is a critical intervention stage as tumors diagnosed in subsequent nonlocalized and malignant stages are exponentially more diffi cult to treat successfully. This chapter explores the critical roles that microRNAs play in the transformation from benign to malignant in four representative cancers: colorectal cancer, pancreatic cancer, malignant peripheral nerve sheath tumor, and prostate cancer. Understanding how these microRNAs control this progression and transformation will lead to new therapeutic targets and diagnostic biomarkers, resulting in improved treatments and patient outcomes.