Cyclophilin A (CypA) is a ubiquitous and highly conserved protein. CypA,
the intracellular target protein for the immunosuppressant cyclosporine A (CsA), plays
important cellular roles through peptidyl-prolyl cis-trans isomerase (PPIase). Increasing
evidence shows that CypA is up-regulated in a variety of human cancers. In addition to
being involved in the occurrence and development of multiple tumors, overexpression of
CypA has also been shown to be strongly associated with malignant transformation.
Surgery, chemotherapy and radiotherapy are the three main treatments for cancer. Chemotherapy
and radiotherapy are often used as direct or adjuvant treatments for cancer.
However, various side effects and resistance to both chemotherapy and radiotherapy
bring great challenges to these two forms of treatment. According to recent reports, CypA
can improve the chemosensitivity and/or radiosensitivity of cancers, possibly by affecting
the expression of drug-resistant related proteins, cell cycle arrest and activation of
the mitogen-activated protein kinase (MAPK) signaling pathways. In this review, we focus
on the role of CypA in cancer, its impact on cancer chemotherapeutic and radiotherapy
sensitivity, and the mechanism of action. It is suggested that CypA may be a novel potential
therapeutic target for cancer chemotherapy and/or radiotherapy.