Circular RNAs (CircRNAs) in cancer therapy response: Biological aspects

Biological functions of genes have been investigated in terms of regulating growth and metastasis of cancer cells. Although targeting genetic and epigenetic factors is a promising approach in oncology and tumor suppression, understanding the role of these factors in therapy response of cancer cells is also of interest, since increasing evidence reveals the development of drug resistance and radioresistance. Chemotherapy agents follow the process of cell cycle arrest and apoptosis induction in decreasing tumor progression, and radiotherapy mainly stimulates mitotic catastrophe and DNA damage in cancer therapy. With respect to the activation of factors responsible for DNA damage repair and increasing tumor proliferation, cancer cells have shown the ability to develop therapy resistance. Circular RNAs (circRNAs) are RNA transcripts that do not encode protein and possess regulatory functions in cells. The biological function of circRNAs in terms of regulating proliferation, migration, differentiation, and apoptosis has been understood, and dysregulation of these factors can lead to cancer initiation and development. Due to the role of circRNAs in affecting tumor growth and metastasis and their ability in regulating signaling networks in different cancers, this chapter is allocated to highlight the function of these epigenetic factors in regulating drug resistance and radioresistance in cancers.