CDK7/CDK9 mediates transcriptional activation to prime paraptosis in cancer cells.

BACKGROUND: Paraptosis is a programmed cell death characterized by cytoplasmic vacuolation, which has been explored as an alternative method for cancer treatment and is associated with cancer resistance. However, the mechanisms underlying the progression of paraptosis in cancer cells remain largely unknown. METHODS: Paraptosis-inducing agents, CPYPP, cyclosporin A, 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. 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 in a forward loop, amplifying transcriptional regulation and thereby exacerbating proteotoxicity leading to initiate paraptosis. The xenograft mouse models of MDA-MB-231 breast cancer and docetaxel-resistant OECM-1 head and neck cancer 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.

[Corrigendum] Next­generation sequencing analysis reveals that MTH­3, a novel curcuminoid derivative, suppresses the invasion of MDA­MB­231 triple­negative breast adenocarcinoma cells.

Subsequently to the publication of the article, an interested reader drew to the authors' attention that, in Fig. 2A on p. 5, the 'Control  (24 h)' and 'MTH­3 (1 µM; 24 h)' data panels contained partially overlapping data, such that they appeared to have been derived from the same original source. The authors have examined their original data, and realized that this error arose inadvertently as a consequence of having compiled this figure incorrectly. The revised version of Fig. 2, featuring the data from one of the repeated experiments in Fig. 2A, is shown below. The revised data shown for this figure do not affect the overall conclusions reported in the paper. The authors apologize to the Editor of Oncology Reports and to the readership for any inconvenience caused. [Oncology Reports 46: 133, 2021; DOI: 10.3892/or.2021.8084].

MRCK as a Potential Target for Claudin-Low Subtype of Breast Cancer.

To find new molecular targets for triple negative breast cancer (TNBC), we analyzed a large-scale drug screening dataset based on breast cancer subtypes. We discovered that BDP-9066, a specific MRCK inhibitor (MRCKi), may be an effective drug against TNBC. After confirming the efficacy and specificity of BDP-9066 against TNBC in vitro and in vivo, we further analyzed the underlying mechanism of specific activity of BDP-9066 against TNBC. Comparing the transcriptome of BDP-9066-sensitive and -resistant cells, the activation of the focal adhesion and YAP/TAZ pathway were found to play an important role in the sensitive cells. Furthermore, YAP/TAZ is indeed repressed by BDP-9066 in the sensitive cells, and active form of YAP suppresses the effects of BDP-9066. YAP/TAZ expression and activity are high in TNBC, especially the Claudin-low subtype, consistent with the expression of focal adhesion-related genes. Interestingly, NF-κB functions downstream of YAP/TAZ in TNBC cells and is suppressed by BDP-9066. Furthermore, the PI3 kinase pathway adversely affected the effects of BDP-9066 and that alpelisib, a PI3 kinase inhibitor, synergistically increased the effects of BDP-9066, in PIK3CA mutant TNBC cells. Taken together, we have shown for the first time that MRCKi can be new drugs against TNBC, particularly the Claudin-low subtype.