Erratum: Targeting sphingosine kinase 2 suppresses cell growth and synergizes with BCL2/BCL-XL inhibitors through NOXA-mediated MCL1 degradation in cholangiocarcinoma.

[This corrects the article on p. 546 in vol. 9, PMID: 30949409.].

A Design Method of Traveling Wave Rotary Ultrasonic Motors Driving Circuit under High Voltage Using Single-Sided Hertzian Contact Forced Oscillator Model.

Traveling wave rotary ultrasonic motors (TRUMs) are widely used in various industrial processes due to their attractive features, such as compact structure, high accuracy, and fast response. However, the major limiting factors of the operational performance of TRUMs under high-voltage excitation are the nonlinear behavior caused by the nonlinearities of the piezoelectric materials and the friction between the stator and rotor of the motor. In this study, a nonlinear dynamics model and an identification method are presented to directly design the driver circuit for suppressing the nonlinear behavior under high voltage excitation. Firstly, by studying the time-frequency characteristics of the isolated electrode voltage, a single-sided Hertzian contact forced oscillator model of TRUMs is established, involving the nonlinearities of the piezoelectric material and friction. Secondly, a harmonic balance nonlinear identification is proposed in the time domain for TRUMs. The influence of the voltage and preload on the nonlinear phenomena is discussed. Lastly, a novel driver circuit is proposed to suppress the nonlinearities using feedback from the isolated electrode. Experiments showed that the total harmonic distortion decreased by 89.4% under 500 Vpp. The proposed drive circuit design method is used to find a high excitation voltage and preload to achieve greater motor output power.

Therapeutic Rationale to Target Highly Expressed Aurora kinase A Conferring Poor Prognosis in Cholangiocarcinoma.

Background: Cholangiocarcinoma is a highly lethal neoplasm for which the currently available chemotherapeutic agents are suboptimal. Numerous studies show that alterations in expression of genes related to mitotic spindle and mitotic checkpoint are involved in chromosomal instability and tumor progression in various malignancies. This study aimed to evaluate these genes in cholangiocarcinoma patients. Material and methods: Different public datasets were analyzed to examine the expression of 76 selected mitotic spindle checkpoint genes including Aurora Kinase A (AURKA) in cholangiocarcinoma. Afterwards, cell number counting, CCK-8 assay, and Caspase 3/7 assay were used to explore the antitumor effect of AURKA inhibitor Alisertib in vitro. In addition, xenograft model was used to evaluate the antitumor effect of Alisertib in vivo. Furthermore, siRNA mediated silencing of AURKA was used to verify the function of AURKA in cholangiocarcinoma. Results: Components of the mitotic spindle checkpoint, including AURKA, were broadly dysregulated in human cholangiocarcinoma. High AURKA mRNA expression was associated with poor survival in cholangiocarcinoma patients within different datasets. AURKA specific inhibitor Alisertib, inhibited cell growth, induced cell cycle arrest in G2/M phase, and promoted apoptosis in cholangiocarcinoma cell lines. Additionally, Alisertib also inhibited tumor growth in a cholangiocarcinoma xenograft mouse model. Furthermore, AURKA knockdown by siRNA recapitulated the antitumor effect of Alisertib. AURKA expression was also highly correlated with its interaction proteins Polo-like kinase 1(PLK1) and Targeting protein for xenopus kinesin-like protein2 (TPX2) in different cholangiocarcinoma datasets. Conclusions: Highly expressed AURKA confers poor outcomes in cholangiocarcinoma and may represent a rational therapeutic target.

CDK7 inhibitor THZ1 inhibits MCL1 synthesis and drives cholangiocarcinoma apoptosis in combination with BCL2/BCL-XL inhibitor ABT-263.

Cholangiocarcinoma (CCA) is a fatal disease without effective targeted therapy. We screened a small-molecule library of 116 inhibitors targeting different targets of the cell cycle and discovered several kinases, including Cyclin-dependent kinase 7 (CDK7) as vulnerabilities in CCA. Analysis of multiple CCA data sets demonstrated that CDK7 was overexpressed in CCA tissues. Further studies demonstrated that CDK7 inhibitor THZ1 inhibited cell viability and induced apoptosis in CCA cells. We also showed that THZ1 inhibited CCA cell growth in a xenograft model. RNA-sequencing followed by Gene ontology analysis showed a striking impact of THZ1 on DNA-templated transcriptional programs. THZ1 downregulated CDK7-mediated phosphorylation of RNA polymerase II, indicative of transcriptional inhibition. A number of oncogenic transcription factors and survival proteins, like MCL1, FOSL1, and RUNX1, were repressed by THZ1. MCL1, one of the antiapoptotic BCL2 family members, was significantly inhibited upon THZ1 treatment. Accordingly, combining THZ1 with a BCL2/BCL-XL inhibitor ABT-263 synergized in impairing cell growth and driving apoptosis. Our results demonstrate CDK7 as a potential target in treating CCA. Combinations of CDK7 inhibition and BCL2/BCL-XL inhibition may offer a novel therapeutic strategy for CCA.

BRD4 degrader ARV-825 produces long-lasting loss of BRD4 protein and exhibits potent efficacy against cholangiocarcinoma cells.

BRD4, a member of the bromodomain and extraterminal domain (BET) family and an important epigenetic reader, has emerged as an attractive oncology target. Cholangiocarcinoma is a lethal neoplasm without approved targeted therapies. BET bromodomain inhibitors have shown promising effects in certain cancers including cholangiocarcinoma. Recently developed BRD4 Proteolysis Targeting Chimera (PROTAC) compounds lead to fast and efficient degradation of BRD4 and provides longer-lasting effect than small molecule BRD4 inhibitors. In this study, we investigated the antitumor effect of a newly developed BRD4 degrader ARV-825 in cholangiocarcinoma. Immunohistochemistry and Western blotting were used to determine the expression level of BRD4. CCK-8 assay and BrdU ELISA assay were used to assess cell proliferation. Caspase 3/7 activity and Annexin V/PI staining were used to assess apoptosis. We demonstrated that BRD4 expression was elevated in cholangiocarcinoma tissues compared to normal bile duct or surrounding normal liver tissues. ARV-825 produced fast and long-lasting loss of BRD4 protein, resulting in more inhibition of CCA cell proliferation and induction of apoptosis than BRD4 inhibitors OTX-015 and JQ1. C-Myc is a well-known downstream target of BRD4. We found that ARV-825 suppressed c-Myc levels more effectively than BRD4 inhibitors. However, ARV-825 did not inhibit c-Myc expression in CCA cells with low basal c-Myc levels. Further analysis showed that ARV-825 significantly upregulated p21 expression and arrested cell cycle progression at G1 phase. In conclusion, BRD4 degrader ARV-825 leads to rapid and sustained degradation of BRD4 and is effective against cholangiocarcinoma.

Targeting sphingosine kinase 2 suppresses cell growth and synergizes with BCL2/BCL-XL inhibitors through NOXA-mediated MCL1 degradation in cholangiocarcinoma.

Sphingosine kinase 2 (SPHK2) is a key factor within sphingolipid metabolism, responsible for the conversion of pro-apoptotic sphingosine to the pro-survival sphingosine-1-phosphate. We have previously shown that ABC294640, a first-in-class SPHK2 inhibitor, inhibits growth of cholangiocarcinoma cells. In a Phase I study of ABC294640 in tumors, the best response was achieved in a cholangiocarcinoma patient. These data suggest SPHK2 as a novel therapeutic target of cholangiocarcinoma. However, the antitumor mechanism of ABC294640 in cholangiocarcinoma remains not clear. In the current study, we found that ABC294640 upregulated expression of pro-apoptotic NOXA. In cholangiocarcinoma patients, high NOXA mRNA expression was associated with better overall survival. Also, SPHK2 mRNA expression was negatively correlated with NOXA mRNA expression. NOXA is known to degrade MCL1, an anti-apoptotic BCL2 protein. We showed that ABC294640 directed MCL1 for proteasome degradation. Knockdown of NOXA prevented ABC294640-induced MCL1 degradation and apoptosis. In addition, ABC294640 had a synergistic effect with BCL2/BCL-XL inhibitors ABT-263 and Obatoclax in inhibiting cell growth. Combined treatment with ABC294640 and BCL2/BCL-XL inhibitors induced potent apoptosis. Silencing of MCL1 also potentiated ABT-263-induced cytotoxicity. Furthermore, we found that both SPHK2 and MCL1 protein expression were significantly higher in cholangiocarcinoma than that in nontumoral bile ducts. SPHK2 expression correlated significantly with MCL1 expression. Our study reveals that ABC294640 inhibits cholangiocarcinoma cell growth and sensitizes the antitumor effect of BCL2/BCL-XL inhibitors through NOXA-mediated MCL1 degradation. Combinations of ABC294640 with BCL2/BCL-XL inhibitors may provide novel strategies for the treatment of cholangiocarcinoma.