CPYPP induces paraptosis in MDA-MB-231 and MDA-MB-435 melanoma cells

Background: Paraptosis is a programmed cell death characterized by cytoplasmic vacuolation, which has been used as an alternative cell death method for cancer treatment and is associated with cancer resistance. However, the mechanisms underlying the progression of paraptosis in cancer cells are largely unknown. Methods: Paraptosis-inducing agents, CPYPP, cyclosporin, and curcumin, were utilized to investigate the underlying mechanism of paraptosis. Next-generation sequencing and liquid chromatography-mass spectrometry analysis revealed significant changes in gene and protein expressions. Pharmacological and genetic approaches were employed to elucidate the transcriptional events related to paraptosis. The xenograft mouse models were employed to evaluate the potential of paraptosis as an anti-cancer strategy. Results: CPYPP, cyclosporin A, and curcumin induced cytoplasmic vacuolization and triggered paraptosis in cancer cells. The paraptotic program involved reactive oxygen species (ROS) provocation and the activation of proteostatic dynamics, leading to transcriptional activation associated with redox homeostasis and proteostasis. Both pharmacological and genetic approaches suggested that cyclin-dependent kinase (CDK) 7/9 drive paraptotic progression in a mutually-dependent manner with heat shock proteins (HSPs). Proteostatic stress, such as accumulated cysteine-thiols, HSPs, ubiquitin-proteasome system, endoplasmic reticulum stress, and unfolded protein response, as well as ROS provocation primarily within the nucleus, enforced CDK7/CDK9–Rpb1 (RNAPII subunit B1) activation by potentiating its interaction with HSPs and protein kinase R (PKR) in a forward loop, amplifying transcriptional regulation and thereby exacerbating proteotoxicity leading to initiate paraptosis. A xenograft mouse model with OECM-1 cells further confirmed the induction of paraptosis against tumor growth. Conclusions We propose a novel regulatory paradigm in which the activation of CDK7/CDK9–Rpb1 by nuclear proteostatic stress mediates transcriptional regulation to prime cancer cell paraptosis.