Cancerous inhibitor of PP2A is targeted by natural compound celastrol for degradation in non-small-cell lung cancer

Abstract

Celastrol binds CIP2A and enhances CIP2A–CHIP interaction, leading to ubiquitination/degradation of CIP2A and inhibition of lung cancer cells in vitro and in vivo. Celastrol potentiates cisplatin’s efficacy by suppressing the CIP2A–Akt pathway, and therefore CIP2A inhibitors may represent novel therapeutics for cancer. Cancerous inhibitor of protein phosphatase 2A (CIP2A) is an oncoprotein overexpressed and inversely associated with prognosis in lung and many other human cancers. It modulates phospho-Akt and stabilizes c-Myc, and is required for cell proliferation and malignant transformation, indicating that CIP2A may play an important role in carcinogenesis. We reported here that a small compound celastrol could induce a rapid degradation of CIP2A, through the ubiquitin–proteasome pathway with the carboxyl terminus of Hsp70-interacting protein (CHIP) as the E3 ligase. Celastrol directly bound CIP2A protein and promoted CIP2A–CHIP interaction, leading to subsequent degradation of CIP2A in non-small-cell lung cancer cells. Furthermore, celastrol effectively inhibited cell proliferation and induced apoptosis in non-small-cell lung cancer cells, whereas CIP2A silencing enhanced these effects. Celastrol also suppressed tumor growth in xenograft murine models. In addition, celastrol potentiated the inhibitory effect of cytotoxic agent cisplatin on lung cancer cells in vitro and in vivo via inhibition of CIP2A–Akt pathway. These data indicate that celastrol is a CIP2A-targeting agent that may have therapeutic potentials in lung cancer.