AMPKα2 Regulates Bladder Cancer Growth through SKP2-Mediated Degradation of p27

SIRT5-mediated PRKAA2 succinylation ameliorates apoptosis of human placental trophoblasts in hypertensive disorder complicating pregnancy

PURPOSE

Hypertensive disorder complicating pregnancy (HDCP) is a serious clinical disorder syndrome during pregnancy. This study aims at finding novel targets for HDCP therapy.

METHODS

HDCP-related mRNAs were firstly screened out and subjected to gene enrichment analysis. We chose protein kinase AMP-activated catalytic subunit alpha 2 (PRKAA2) as the research object. Thirty-nine HDCP patients at 32 to 40 weeks of gestation were selected as the HDCP group, and 39 normal controls who received cesarean section delivery at 37-42 weeks of pregnancy were enrolled in this study. Chorionic villi samples were collected within 30 min of delivery. The apoptosis of isolated placental trophoblasts was monitored to investigate the regulatory role of PRKAA2.

RESULTS

PRKAA2 expression was further proven to be enhanced in the placental tissues of HDCP patients compared with that of normal puerpera. Subsequently, the results of flow cytometry analysis and western blot indicated that PRKAA2 overexpression accelerated primary placental cell apoptosis, while its knockdown attenuated cell apoptosis. Mechanistically, we determined that the level of PRKAA2 succinylation was elevated in the placental tissue of HDCP patients. Through in vitro succinylation assay and mutagenesis, we confirmed that sirtuin 5 (SIRT5) interacts with PRKAA2 at K69 and K260 to induce PRKAA2 desuccinylation. SIRT5 regulated primary HDCP cell apoptosis through PRKAA2. Finally, the animal study revealed that PRKAA2 elevates the systolic blood pressure of HDCP rat model.

CONCLUSION

Our findings indicated that SIRT5-mediated PRKAA2 succinylation modulates placental cell apoptosis in HDCP, suggesting that PRKAA2 is a potential therapeutic target for HDCP treatment.

Oridonin inhibited epithelial-mesenchymal transition of laryngeal carcinoma by positively regulating LKB1/AMPK signaling

Oridonin is the main bioactive component of Rabdosia rubescens, and its anticancer activity has been reported in a variety of cancers. However, the molecular mechanism of oridonin in laryngeal carcinoma remains unclear. In the present study, the cytotoxic effect of oridonin on laryngeal carcinoma Hep-2 and TU212 cell lines were initially detected by modified MTT assay. The results showed that oridonin had a dose-dependent anti-proliferative effect on laryngeal carcinoma Hep-2 and TU212 cells. Next, we found that oridonin significantly inhibited the migration and invasion of human laryngeal carcinoma Hep-2 and TU212 cell lines by wound healing assay and transwell assay. Subsequently, the results of quantitative real-time PCR assay and western blotting assay confirmed that oridonin upregulated the expression of E-cadherin while downregulated the expression of N-cadherin in a concentration-dependent manner at mRNA and protein levels. In addition, phosphorylation levels of liver kinase B1 (p-LKB1) and AMP-activated protein kinase (p-AMPK) were also elevated upon oridonin treatment. To further verify the role of LKB1/AMPK signaling pathway in laryngeal carcinoma, overexpression of LKB1 was constructed by plasmid transfection. The data exhibited that overexpression of LKB1 could further reinforce the increase of E-cadherin level and decrease of N-cadherin level mediated by oridonin. Additionally, AMPK inhibitor compound C could reverse anti-metastatic effect of oridonin on laryngeal carcinoma, and antagonise EMT expression. In contrast, AMPK activator AICAR presented the opposite effect. In conclusion, our study revealed that oridonin could remarkably reverse the epithelial-mesenchymal transition of laryngeal carcinoma by positively regulating LKB1/AMPK signaling pathway, which suggested that oridonin may be a potential candidate for the treatment of laryngeal carcinoma in the future.

Loss of AMPKα2 promotes melanoma tumor growth and brain metastasis

AMP-activated protein kinase (AMPK) is a critical cellular energy sensor at the interface of metabolism and cancer. However, the role of AMPK in carcinogenesis remains unclear. Here, through analysis of the TCGA melanoma dataset, we found that PRKAA2 gene that encodes the α2 subunit of AMPK is mutated in ∼9% of cutaneous melanomas, and these mutations tend to co-occur with NF1 mutations. Knockout of AMPKα2 promoted anchorage-independent growth of NF1-mutant melanoma cells, whereas ectopic expression of AMPKα2 inhibited their growth in soft agar assays. Moreover, loss of AMPKα2 accelerated tumor growth of NF1-mutant melanoma and enhanced their brain metastasis in immune-deficient mice. Our findings support that AMPKα2 serves as a tumor suppressor in NF1-mutant melanoma and suggest that AMPK could be a therapeutic target for treating melanoma brain metastasis.

AMPK and the Challenge of Treating Hypoxic Pulmonary Hypertension

Hypoxic pulmonary hypertension (HPH) is characterized by sustained elevation of pulmonary artery pressure produced by vasoconstriction and hyperproliferative remodeling of the pulmonary artery and subsequent right ventricular hypertrophy (RVH). The search for therapeutic targets for cardiovascular pathophysiology has extended in many directions. However, studies focused on mitigating high-altitude pulmonary hypertension (HAPH) have been rare. Because AMP-activated protein kinase (AMPK) is involved in cardiovascular and metabolic pathology, AMPK is often studied as a potential therapeutic target. AMPK is best characterized as a sensor of cellular energy that can also restore cellular metabolic homeostasis. However, AMPK has been implicated in other pathways with vasculoprotective effects. Notably, cellular metabolic stress increases the intracellular ADP/ATP or AMP/ATP ratio, and AMPK activation restores ATP levels by activating energy-producing catabolic pathways and inhibiting energy-consuming anabolic pathways, such as cell growth and proliferation pathways, promoting cardiovascular protection. Thus, AMPK activation plays an important role in antiproliferative, antihypertrophic and antioxidant pathways in the pulmonary artery in HPH. However, AMPK plays contradictory roles in promoting HPH development. This review describes the main findings related to AMPK participation in HPH and its potential as a therapeutic target. It also extrapolates known AMPK functions to discuss the less-studied HAPH context.

CircCDC6 restrains tumor growth and glycolysis energy metabolism in colorectal cancer via regulating miR-3187-3p and downstream PRKAA2

The aberrant downregulation of circCDC6 in colorectal cancer (CRC) was previously identified by circRNA microarray analysis. However, the detailed role of circCDC6 in CRC is still lacking. We thus investigated the function of circCDC6 in CRC. The expression of circCDC6, miR-3187-3p and PRKAA2 mRNA was checked by real-time quantitative PCR (RT-qPCR). Cell growth was evaluated by MTT, EdU and colony formation assays. Cell apoptosis was evaluated by flow cytometry. Glycolysis was evaluated by glycolysis stress test and lactic acid level. The expression of PRKAA2, HK2 and LDHA proteins was checked by western blotting. The potential binding between miR-3187-3p and circCDC6 or PRKAA2 was confirmed by dual-luciferase reporter assay, RIP assay and pull-down assay. Xenograft model was established in nude mice. CircCDC6 showed poor expression in CRC tumor samples and cells. CircCDC6 ectopic expression repressed CRC cell proliferation, survival and glycolysis energy metabolism. MiR-3187-3p was targeted by circCDC6, and miR-3187-3p depletion also repressed CRC cell growth and glycolysis. PRKAA2 was a downstream target of circCDC6/miR-3187-3p pathway, and circCDC6 upregulated PRKAA2 expression via targeting miR-3187-3p. PRKAA2 knockdown rescued the functional effects of circCDC6 ectopic expression. CircCDC6 overexpression in vivo impeded tumor development in animal models. CircCDC6, acting as a tumor inhibitor, repressed tumor growth and glycolysis metabolism in CRC via targeting the miR-3187-3p/PRKAA2 axis, which partly clarified the role of circCDC6 in CRC.

Insights into the Role of microRNAs in Colorectal Cancer (CRC) Metabolism

Colorectal cancer (CRC) is one of the most frequently diagnosed cancers, with a high mortality rate globally. The pathophysiology of CRC is mainly initiated by alteration in gene expression, leading to dysregulation in multiple signalling pathways and cellular processes. Metabolic reprogramming is one of the important cancer hallmarks in CRC, which involves the adaptive changes in tumour cell metabolism to sustain the high energy requirements for rapid cell proliferation. There are several mechanisms in the metabolic reprogramming of cancer cells, such as aerobic glycolysis, oxidative phosphorylation, lactate and fatty acids metabolism. MicroRNAs (miRNAs) are a class of non-coding RNAs that are responsible for post-transcriptional regulation of gene expression. Differential expression of miRNAs has been shown to play an important role in different aspects of tumorigenesis, such as proliferation, apoptosis, and drug resistance, as well as metabolic reprogramming. Increasing evidence also reports that miRNAs could function as potential regulators of metabolic reprogramming in CRC cells. This review provides an insight into the role of different miRNAs in regulating the metabolism of CRC cells as well as to discuss the potential role of miRNAs as biomarkers or therapeutic targets in CRC tumour metabolism.

AMPKα2 deficiency exacerbates hypoxia-induced pulmonary hypertension by promoting pulmonary arterial smooth muscle cell proliferation

Increased evidence indicates that adenosine monophosphate-activated protein kinase (AMPK) plays a vital role in vascular homeostasis, especially under hypoxia, and protects against the progression of pulmonary hypertension (PH). However, the role of AMPK in the pathogenesis of PH remains to be clarified. In the present study, we confirmed that a loss of AMPKα2 exacerbated the development of PH by using hypoxia-induced PH model in AMPKα2 ^-/- mice. After a 4-week period of hypoxic exposure, AMPKα2 ^-/- mice exhibited more severe pulmonary vascular remodeling and pulmonary vascular smooth muscle cell (SMC) proliferation when compared with wild type (WT) mice. In vitro, AMPKα2 knockdown promoted the proliferation of pulmonary arterial smooth muscle cells (PASMCs) under hypoxia. This phenomenon was accompanied by upregulated Skp2 and downregulated p27^kip1 expression and was abolished by rapamycin, an inhibitor of mTOR. These results indicate that AMPKα2 deficiency exacerbates hypoxia-induced PH by promoting PASMC proliferation via the mTOR/Skp2/p27^kip1 signaling axis. Therefore, enhanced AMPKα2 activity might underlie a novel therapeutic strategy for the management of PH.

miR-4999-5p Predicts Colorectal Cancer Survival Outcome and Reprograms Glucose Metabolism by Targeting PRKAA2

Purpose

Colorectal cancer (CRC) is the third most common cancer, and the second leading cause of cancer death worldwide. Dysregulation of microRNAs has been shown to modulate glucose metabolic reprogramming in CRC. However, the functional role of miR-4999-5p in the CRC glucose metabolic shift has not been characterized.

Patients and Methods

The levels of miR-4999-5p and PRKAA2 were evaluated by RT-qPCR. Univariate and multivariate survival analyses were conducted to evaluate the prognostic value of miR-4999-5p. Cell proliferation was assessed using the CCK-8 and colony formation assays. Extracellular acidification rate, glucose uptake, cellular glucose-6-phosphate level, and lactate production were evaluated to assess the effects of miR-4999-5p on CRC glycolysis. Dual-luciferase reporter assay was conducted to investigate the direct interaction between miR-4999-5p and PRKAA2. Mouse xenograft models were established to assess the functions of miR-4999-5p in vivo.

Results

miR-4999-5p was highly expressed in CRC tissues and cell lines. In addition, miR-4999-5p was associated with tumor differentiation and TNM stage, and elevated expression of miR-4999-5p was an independent predictor of poorer overall survival. Furthermore, miR-4999-5p promoted cell proliferation and glycolysis in CRC. miR-4999-5p targeted PRKAA2 to exert its tumor-promoting functions, and PRKAA2 knockdown rescued decreased cell proliferation and glycolysis in miR-4999-5p-silenced CRC cells. In vivo experiments showed that miR-4999-5p promoted CRC growth.

Conclusion

miR-4999-5p facilitated cell growth and glucose metabolic reprogramming through direct targeting of PRKAA2. Our results showed that miR-4999-5p may be a novel prognostic marker and therapeutic target for CRC.

Metformin targets a YAP1-TEAD4 complex via AMPKα to regulate CCNE1/2 in bladder cancer cells

Background

Metformin has been reported to function as the anti-tumor inhibiting the growth of different types of cancers, including bladder cancer. But there are few reports on the roles of Yap1, the key molecule of Hippo pathway, in the metformin induced inhibition of bladder cancer (BLCA). We are wondering if the inhibitory effect of metformin on bladder cancer is fulfilled via Yap1 and exploring the related mechanism.

Methods

MTS and colony formation assays were used to explore the cellular viabilities and proliferation of BLCA cells challenged by metformin at different concentrations, in vitro. Flow Cytometry (FCM) was used to analyze the cell cycle and the cellular apoptosis of the BLCA cells. Western Blot was performed to detect the expressions of AMPKα, Yap1, CCND1, CCNE1/2 and CDK2/4/6 in the metformin-treated BLCA cell lines. RNAi method was used for the related genetic functional analysis. The relationships among Yap1, TEADs and CCNE1/2 were predicted and evaluated using bioinformatics, dual-luciferase reporter and co-immunoprecipitation (Co-IP) assays. For in vivo experiments, a xenograft model was used to investigate the effects of metformin on the proliferation of BLCA cells. And Immunohistochemistry (IHC) assay was performed to assess the expressions of CCNE1/2 and Yap1 proteins in the tumor tissues from the model.

Results

Metformin could inhibit the proliferation of the BLCA cells via inducing the G1 cell cycle arrest without apoptosis. And metformin upregulated the phosphorylated AMPKα and decreased the expressions of Yap1 and CCND1, CCNE1/2 and CDK4/6. AMPK inhibition by compound C (CC) restored the cell proliferation and the G1 cell cycle arrest induced by metformin, in vivo. Knockdown of YAP1 inhibited the proliferation of BLCA cells and caused the cell cycle arrest at G1 phase by decreasing the expressions of CCNE1/2 and other G1 phase related molecules, which has been restored by the Yap 5SA mutant. Bioinformatics analysis showed that trans-factor TEAD4 was highly expressed and positively associated with the expressions of CCNE1 and CCNE2 in BLCA and only TEAD4 was precipitated by Yap1 in the BLCA cells. Further studies demonstrated that Yap1 positively regulated both CCNE1 and CCNE2 expressions via forming complex with TEAD4. Furthermore, we observed that metformin inhibited the cell proliferation by decreasing the expressions of Yap1 and both CCNE1 and CCNE2 in xenograft model.

Conclusions

The results of our study reveal a new potential regulatory pathway in which metformin inhibits cell proliferation via AMPKα/Yap1/TEAD4/CCNE1/2 axis in BLCA cells, providing new insights into novel molecular therapeutic targets for BLCA.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1346-1) contains supplementary material, which is available to authorized users.

MAPKAPK2 plays a crucial role in the progression of head and neck squamous cell carcinoma by regulating transcript stability

Background

Head and neck squamous-cell carcinoma (HNSCC) ranks sixth among cancers worldwide. Though several molecular mechanisms of tumor initiation and progression of HNSCC are known, others remain unclear. Significance of p38/MAPKAPK2 (Mitogen-activated protein kinase-activated protein kinase-2) pathway in cell stress and inflammation is well established and its role in tumor development is being widely studied.

Methods

We have elucidated the role of MAPKAPK2 (MK2) in HNSCC pathogenesis using clinical tissue samples, MK2-knockdown (MK2_KD) cells and heterotropic xenograft mice model.

Results

In patient-derived tissue samples, we observed that MK2 is reproducibly overexpressed. Increased stability of cyclin-dependent kinase inhibitor 1B (p27), mitogen-activated protein kinase phosphatase-1 (MKP-1) transcripts and decreased half-life of tumor necrosis factor-alpha (TNF-α) and vascular endothelial growth factor (VEGF) transcripts in MK2_KD cells suggests that MK2 regulates their transcript stability. In vivo xenograft experiments established that knockdown of MK2 attenuates course of tumor progression in immunocompromised mice.

Conclusion

Altogether, MK2 is responsible for regulating the transcript stability and is functionally important to modulate HNSCC pathogenesis.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1167-2) contains supplementary material, which is available to authorized users.

Sequestosome 1 protects esophageal squamous carcinoma cells from apoptosis via stabilizing SKP2 under serum starvation condition

Esophageal squamous cell carcinoma (ESCC) is one of the malignancies in digestive system, with a low 5-year survival rate. We previously revealed that Sequestosome 1 (SQSTM1/p62) protein levels were upregulated in ESCC tissues. However, it is unclear about the function of p62 and the underlying mechanism. Here, we used immunofluorescence and immunohistochemistry to investigate the expression of p62 in ESCC. Western blotting, quantitative RT-PCR, colony formation assay, flow cytometry, immunoprecipitation and xenograft tumor assay were used to analyze the role of p62 in vitro and vivo. Here, we showed that p62 serves as a regulator of cell apoptosis under serum starvation condition in ESCC cells. Through activating the protein kinase C iota (PKCiota)-S-phase kinase-associated protein 2 (SKP2) signaling pathway, p62 enhances cell apoptosis resistance and colony formation in vitro and tumor growth in mouse models. Through interaction with the domains PB1, p62 upregulated the expression of PKCiota and then depressed the ubiquitin-mediated proteasomal degradation of SKP2. p62-silencing combined with a PKCiota inhibitor ATM significantly enhanced cell apoptosis and inhibited cell survival. Immunohistochemical analysis revealed a positive association between the expression of p62 and SKP2 in primary ESCC tissues. And importantly, p62 presented a markedly cytoplasmic translocation in cancerous cells, including in 16 (30.76%) tumors at stage T1, as compared with its nuclear location in normal esophageal epithelial cells. In summary, p62 plays an anti-apoptotic role in ESCC cells via stabilizing SKP2 under serum starvation condition. These data suggest that p62 might be an early biomarker and a candidate therapeutic target of ESCC.

Amentoflavone suppresses tumor growth in ovarian cancer by modulating Skp2

AIM

Ovarian cancer is one of most common malignancies in women and is associated with high reoccurrence rate and poor prognosis. This study is designed to investigate the anti-tumor effects of amentoflavone (AF), one of the major active ingredients of S. tamariscina, against ovarian cancer.

MATERIALS AND METHODS

Human ovarian cancer cell lines SKOV3 and OVCAR-3 were used in this study. The effect of AF on cell viability was examined by CCK-8 assay. Cell apoptosis and cell cycle distribution was determined by flow cytometry. ROS generation was detected using fluorescent staining. Expression of signaling molecules was determined by western blots. Xenograft model was established to evaluate the therapeutic efficacy of AF in vivo.

KEY FINDINGS

Our results showed that AF could significantly suppress cell proliferation, induce apoptosis and block cell cycle progression. Mechanistically, downregulation of S-phase kinase protein 2 (Skp2) by AF contributed to its anti-tumor effect against ovarian cancer. Furthermore, our results showed that AF repressed the expression of Skp2 through ROS/AMPK/mTOR signaling. The anti-tumor effect of AF against ovarian cancer was also confirmed in a xenograft animal model.

SIGNIFICANCE

Overall, our present findings highlighted the potential of AF in the treatment of ovarian cancer. Moreover, our study also provided a new elucidation regarding the anti-tumor mechanisms of AF.

HDAC inhibition as a treatment concept to combat temsirolimus-resistant bladder cancer cells

Introduction

Although the mechanistic target of rapamycin (mTOR) might be a promising molecular target to treat advanced bladder cancer, resistance develops under chronic exposure to an mTOR inhibitor (everolimus, temsirolimus). Based on earlier studies, we proposed that histone deacetylase (HDAC) blockade might circumvent resistance and investigated whether HDAC inhibition has an impact on growth of bladder cancer cells with acquired resistance towards temsirolimus.

Results

The HDAC inhibitor valproic acid (VPA) significantly inhibited growth, proliferation and caused G0/G1 phase arrest in RT112^res and UMUC-3^res. cdk1, cyclin B, cdk2, cyclin A and Skp1 p19 were down-regulated, p27 was elevated. Akt-mTOR signaling was deactivated, whereas acetylation of histone H3 and H4 in RT112^res and UMUC-3^res increased in the presence of VPA. Knocking down cdk2 or cyclin A resulted in a significant growth blockade of RT112^res and UMUC-3^res.

Materials And Methods

Parental (par) and resistant (res) RT112 and UMUC-3 cells were exposed to the HDAC inhibitor VPA. Tumor cell growth, proliferation, cell cycling and expression of cell cycle regulating proteins were then evaluated. siRNA blockade was used to investigate the functional impact of the proteins.

Conclusions

HDAC inhibition induced a strong response of temsirolimus-resistant bladder cancer cells. Therefore, the temsirolimus-VPA-combination might be an innovative strategy for bladder cancer treatment.

RETRACTED: Physcion 8-O-β-glucopyranosideregulates cell cycle, apoptosis, and invasion in glioblastoma cells through modulating Skp2

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief, following the initial request of the corresponding author. The journal has further requested the author to provide explanations for the figure similarities with papers previously published by different authors. However, the author was not able to fulfil the request. The panels U251/PG+Skp2 cDNA from Figure 4E and U251/Vehicle from Figure 6D appear similar to the panels SOX2 shRNA from Figure 3D and CoCl2 from Figure 6B of the article previously published by Yan-tao Han, Xue-hong Chen, Hui Gao, Jun-li Ye and Chun-bo Wang in Acta Pharmacologica Sinica 37(2) (2016) 264–275 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4753366/. The panel U251/PG from Figure 6B appears similar to the panel KYSE30/miR-370 mimic + PIM1 vector from Figure 5D of the article previously published by Yantao Han, Xiuwei Yang, Ning Zhao, Jianjun Peng, Hui Gao and Xia Qiu in the American Journal of Cancer Research 6(12) (2016) 2755–2771 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5199752/.

Long noncoding RNA linc00346 promotes the malignant phenotypes of bladder cancer

BACKGROUND

More and more reports have demonstrated that long noncoding RNAs (lncRNAs) play an important role in the development of a variety of carcinomas, including bladder cancer. However, only a small fraction of them have been characterized. Linc00346 have been found to be upregulated in bladder cancer tissues compared to normal tissues in a microarray-based lncRNA profiling study. In this study, we would like to explore the expression pattern and functional role of linc00346 in bladder cancer.

METHODS

We determined the expression of linc00346 in a cohort of bladder cancer tissues with matched normal tissues as well as human bladder cancer cell lines. We investigated the biological function of linc00346 with CCK-8 assay, colony formation assay, flow cytometry analysis, transwell assay and tumor xenografts mice model.

RESULTS

We found that linc00346 was upregulated in bladder cancer tissues compared to normal tissues. Knockdown of linc00346 inhibited bladder cancer cell proliferation and migration, induced cell cycle arrest and cell apoptosis.

CONCLUSION

Our study demonstrates that linc00346 could be a potential oncogene and a therapeutic target in bladder cancer.