The Emerging Role of the Cancerous Inhibitor of Protein Phosphatase 2A in Pulmonary Diseases

Promising protein targets are observed to play a role in multiple pathways across a variety of diseases, such as the regulation of immune responses, cell cycle, senescence, and DNA repair. The oncoprotein cancerous inhibitor of protein phosphatase 2A (CIP2A) can coordinate all these cell characteristics predominately by inhibiting the activity of the serine threonine protein phosphatase 2A (PP2A). CIP2A directly interacts with PP2A and other proteins, such as the DNA damage protein topoisomerase II-binding protein 1, to regulate signal transduction. CIP2A is overexpressed in many human cancers, including small and non-small cell lung cancers. High CIP2A expression in lung cancer correlates with poor prognosis, increased tumor proliferation, and resistance to targeted therapies or chemotherapy. Interestingly, CIP2A expression or signaling is also observed in several non-cancerous pulmonary diseases, such as chronic obstructive pulmonary disease. CIP2A can determine whether DNA-damaged cells enter mitosis and can mediate whether DNA repair occurs. CIP2A is also a regulator of inflammation and possibly fibrotic responses. Its functions are linked to altered NFκB activation and TNFα, IL-1β, IL-4, IL-6, IL-10, IL-13, and TGFβ signaling. This review outlines the possible impact of CIP2A-mediated signaling in pulmonary diseases, the processes that regulate CIP2A responses, CIP2A-dependent pathways, and potential therapeutic strategies targeting CIP2A. Substantial medicinal chemistry efforts are underway to develop therapeutics aimed at modulating CIP2A activity. The development of specific inhibitors of CIP2A that selectively target its expression or protein stability could improve our understanding of CIP2A’s function in pulmonary diseases.