MicroRNA, epigenetic machinery and lung cancer

Lung cancer is the leading cause of cancer deaths worldwide and over 80% of lung cancer patients are classified as having non-small cell lung cancer. Although there have been technological advancements in the early detection and standard treatment of lung cancer, it is often diagnosed at an advanced stage and is chemoresistant to most available drugs. A number of studies have demonstrated that microRNA is able to modulate various tumorigenic processes, including progression and metastasis, in various mechanisms. In this review we examine the most recent achievements in microRNA and lung cancer treatment and summarize the research progress on the reciprocal regulation between microRNA and epigenetic modifications, as both have been intensively studied in lung cancer. Epigenetic modifications on the human genome regulate gene and microRNA expression at the transcriptional level; inversely, microRNA can also transcriptionally cleave and/or translationally repress the expression of several key enzymes involved in epigenetic processes such as DNA methylation and histone modification. Better understanding of reciprocal regulation between microRNA and epigenetic modifications will underlie the development of novel microRNA orientated diagnostic and therapeutic strategies relating to lung cancer in the near future.