PDK1 is a potential therapeutic target against angiosarcoma cells

A rare case report of breast sarcoma and synchronous thymoma in a 60-year-old woman

This case report aims to describe the clinical presentation, imaging findings, histopathological features and therapeutic approach of a patient diagnosed with coexisting breast sarcoma and thymoma. A 64-year-old woman presented with a palpable lump in her left breast, and subsequent imaging studies (ultrasound, mammography, and MRI) revealed breast sarcoma, a rare and aggressive subtype of breast cancer. At the same time, the MRI revealed the presence of a thymoma. A multidisciplinary approach involving surgeon, breast specialist and oncologist is essential for optimal management and favorable outcomes in patients with this rare diagnosis.

New molecular targets in canine hemangiosarcoma-Comparative review and future of the precision medicine

Human angiosarcoma and canine hemangiosarcoma reveal similarities not only in their aggressive clinical behaviour, but especially in molecular landscape and genetic alterations involved in tumorigenesis and metastasis formation. Currently, no satisfying treatment that allows for achieving long overall survival or even prolonged time to progression does not exist. Due to the progress that has been made in targeted therapies and precision medicine the basis for a new treatment design is to uncover mutations and their functions as possible targets to provide tailored drugs for individual cases. Whole exome or genome sequencing studies and immunohistochemistry brought in the last few years important discoveries and identified the most common mutations with probably crucial role in this tumour development. Also, despite a lack of mutation in some of the culprit genes, the cancerogenesis cause may be buried in main cellular pathways connected with proteins encoded by those genes and involving, for example, pathological angiogenesis. The aim of this review is to highlight the most promising molecular targets for precision oncology treatment from the veterinary perspective aided by the principles of comparative science. Some of the drugs are only undergoing laboratory in vitro studies and others entered the clinic in the management of other cancer types in humans, but those used in dogs with promising responses have been mentioned as priorities.

Angiosarcoma of the Breast: Overview of Current Data and Multimodal Imaging Findings

Angiosarcoma of the breast is a rare breast cancer, which can arise de novo (primary breast angiosarcoma, PBA) or as a secondary malignancy (secondary breast angiosarcoma, SBA) as a result of a biological insult. In the latter case, it is usually diagnosed in patients with a previous history of radiation therapy following a conserving treatment for breast cancer. Over the years, the advances in early diagnosis and treatment of breast cancer, with increasing use of breast-conserving surgery and radiation therapy (instead of radical mastectomy), brought about an increased incidence of the secondary type. PBA and SBA have different clinical presentations and often represent a diagnostic challenge due to the nonspecific imaging findings. The purpose of this paper is to review and describe the radiological features of breast angiosarcoma, both in conventional and advanced imaging to guide radiologists in the diagnosis and management of this rare tumor.

Differences in potential key genes and pathways between primary and radiation-associated angiosarcoma of the breast

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Angiosarcoma of the breast is a high-grade malignant soft tissue tumor, it can be divided into primary and secondary.

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The differences between primary and secondary angiosarcomas in terms of pathogenesis, clinical behavior, early diagnosis biomarkers, genetic abnormalities, and therapeutic targets remain to be fully elucidated.

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Due to its rarity, most of the current information relating to angiosarcoma is provided by case reports and single-institution retrospective cohort studies and the research with large-scale genomic studies published to date are very limited.

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We identified the differentially expressed genes (DEGs) between primary and second breast angiosarcomas and identified the hub genes as well as predicted novel biomarkers, pathways, and potential therapeutic targets for primary and secondary breast angiosarcomas.

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We aimed to identify novel biomarkers, pathways, and potential therapeutic targets for primary and secondary breast angiosarcomas to facilitate future research.

Background

Angiosarcoma of the breast is a high-grade malignant soft tissue tumor, it can be divided into primary and radiation-associated angiosarcoma(secondary). However, the differences between primary and secondary angiosarcomas in terms of pathogenesis, clinical behavior, early diagnosis biomarkers, genetic abnormalities, and therapeutic targets remain to be fully elucidated. At the same time, due to its rarity, most of current information relating to angiosarcoma is provided by case reports. Therefore, exploring the mechanisms of primary and secondary breast angiosarcoma have important value for the discovery of new biomarkers and research into potential therapeutic targets.

Methods

The differentially expressed genes (DEGs) between 36 cases of primary angiosarcoma and 54 cases of secondary angiosarcoma were screened. Then, the DEGs were used to gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis. Then, a protein-protein interaction (PPI) network was constructed using the STRING database.

Results

A total of 18 DEGs were identified, of which 13 were upregulated and 5 were downregulated in secondary breast angiosarcoma. The GO enrichment analysis showed that the DEGs were most enriched in metabolism, energy pathways, and protein metabolism in biological processes. The enriched signaling pathways of DEGs were the transforming growth factor-β (TGF-β), Wnt, Hippo and PI3K-Akt signaling pathways. Then, the PPI network was conducted and hub genes were identified and they were involved in thyroid hormone, Hippo and other signaling pathways.

Conclusion

This study lay the foundation for the discovery of effective and reliable molecular biomarkers and essential therapeutic targets for these malignancies.

Development and validation of a prognostic nomogram model in primary cutaneous and subcutaneous soft tissue angiosarcoma

OBJECTIVE

The current study aimed to investigate the prognosis and treatment of primary cutaneous angiosarcoma (PCA) and primary subcutaneous angiosarcoma (PSCA), and tried to develop a prognostic nomogram model of them.

METHODS

A total of 1763 cases retrieved from the Surveillance, Epidemiology, and End Results (SEER) database were retrospectively analyzed. Survival analyses were performed to explore the prognosis of patients and the effects of different treatment methods. All data were randomly allocated into a training set and a testing set to develop and validate the nomogram model.

RESULTS

The findings showed that age, sex, grade, tumor size, multiple primary malignant tumors, stage, primary site surgery (PSS), radiotherapy (RT), and chemotherapy (CT) were correlated with prognosis (p < .05). The nomogram achieved good accuracy in predicting the prognosis. PSS + RT + CT showed the best prognosis for patients in stages I, II, and III (p < .05).

CONCLUSION

PCA and PSCA are rare with poor prognoses. Patients undergoing PSS may not gain survival benefits from combining with RT or (and) CT, whereas PSS + RT + CT should be actively performed in earlier stages to improve the prognosis of patients. The nomogram model can be used to predict the overall survival rate and guide better treatment.

Aberrant PTEN, PIK3CA, pMAPK, and TP53 expression in human scalp and face angiosarcoma

Angiosarcoma is a rare, highly aggressive malignant tumor originating from endothelial cells that line the lumen of blood or lymphatic vessels. The molecular mechanisms of scalp and face angiosarcoma still need to be elucidated. This study aimed to investigate the expression of phosphatase and tensin homolog (PTEN), phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA), phosphorylated mitogen-activated kinase-like protein (pMAPK), and tumor protein p53 (TP53) in scalp and face angiosarcoma and to assess tumor tissue apoptosis.The expression and intracellular distribution of PTEN, PIK3CA, pMAPK, and TP53 proteins in 21 specimens of human scalp and face angiosarcoma and 16 specimens of human benign hemangioma were evaluated using immunohistochemistry. Tumor cell apoptosis was assessed by terminal deoxyribonucleotide transferase-mediated dUTP nick end-labeling staining.Significantly lower PTEN but higher PIK3CA, pMAPK, and TP53 immunostaining were detected in the angiosarcoma specimens than in the benign hemangioma specimens(P < .01). The angiosarcoma tissues exhibited significantly higher apoptosis indices than the benign hemangioma tissues (P < .01). The positive expression rates of PIK3CA, pMAPK, and TP53 were correlated with the degree of tumor differentiation in the human scalp and face angiosarcoma.The PI3K, MAPK, and TP53 pathways might be involved in angiosarcoma tumorigenesis in humans and may serve as therapeutic targets for the effective treatment of this malignancy.

PDK1 Inhibitor GSK-470 Exhibits Potent Anticancer Activity in a Pheochromocytoma PC12 Cell Tumor Model via Akt/mTOR Pathway

BACKGROUND

Phosphoinositide-Dependent Kinase 1 (PDK1) is now widely studied in malignant solid tumors. Researchers have previously revealed that targeting PDK1 is thought of as a promising anticancer treatment strategy. The aim of this study was designed to evaluate the anticancer activity of GSK-470, a novel and highly specific inhibitor of PDK1, in Pheochromocytoma (PCC) tumor model.

METHODS

PC12 cells were xenografted into nude mice to build PCC tumor model. Animals were treated with GSK-470 vs vehicle. Mean tumor volume was calculated and compared across groups. TUNEL was used to detect apoptosis. The effects of PDK1 inhibitor GSK-470 on activation of the Akt signaling and its downstream Akt/mTOR pathway in xenotransplant tumor tissues were examined by western bolt.

RESULTS

The mean tumor volume in GSK-470 group was significantly less than that in control group. TUNEL results found that cell apoptosis was markedly increased in GSK-470 group compared with the control group. The western bolt analysis showed that the phosphorylation of Akt at threonine 308 was significantly reduced in GSK-470 group. Also, GSK-470 strongly inhibited phosphorylation of mTOR on Ser2448, a marker for mTORC1 activity, as well as phosphorylation of p70S6K, best characterized targets of mTOR.

CONCLUSION

Our results showed that GSK-470 exhibited potent anticancer activity in PC12 tumor-bearing mice. Also, we found that this effect appeared to be mediated by the inhibition of the Akt/mTOR pathway. The present study once again provides new insights into the therapeutic effects of inhibiting PDK1 in the treatment of malignant PCC. Therefore, we propose that GSK-470 might be an effective therapeutic agent for the treatment of malignant PCC.

The Effectiveness of Different Treatment Modalities of Cutaneous Angiosarcoma: Results From Meta-Analysis and Observational Data From SEER Database

Introduction

Cutaneous angiosarcoma (cAS) is an aggressive vascular tumor that originates from vascular or lymphatic epithelial cells. To date, the cAS literature has been limited in a small number with single-center experiences or reports due to its rarity and the optimal treatment strategy is still in dispute. This study aimed to conduct a systematic review and compare the effect of available treatments retrieved from observational studies and Surveillance, Epidemiology, and End Results (SEER) program.

Methods

The authors performed a systematic review in the PubMed, Embase and MEDLINE database identifying the researches assessing the treatment for cAS patients. Clinical and treatment information of patients who had been diagnosed with a primary cAS were also obtained from the SEER program.

Results

Thirty-two studies were eligible but only 5 of which with 276 patients were included in meta-analysis since the unclear or unavailable information. The risk ratio of 5-year death for surgery, surgery with radiotherapy and surgery with chemotherapy were 0.84, 0.96, and 0.69. Meanwhile, in SEER database, there are 291 metastatic and 437 localized patients with cAS. The localized patients receiving surgery showed a significantly worse overall survival result when compared with the surgery combined with RT: hazard ratio: 1.6, 95% confidential interval: 1.05, 2.42, P = 0.03.

Conclusion

In conclusion, our study provided a detailed picture of the effectiveness of present treatments for localized and metastatic cAS patients. The CT could be inappropriate in localized patients. For metastatic patients, the surgery combined RT was recommended compared with surgery alone since its enhanced OS prognosis. Yet, more novel-designed clinical trials with specific targeted populations and rigorous conducting are needed for a solid conclusion on which would be a better treatment strategy.

MicroRNA-451a prevents cutaneous squamous cell carcinoma progression via the 3-phosphoinositide-dependent protein kinase-1-mediated PI3K/AKT signaling pathway

The role of microRNAs (miRNAs/miRs) in governing the progression of cutaneous squamous cell carcinoma (cSCC) has been the focus of recent studies. However, the functional role of miR-451a in cSCC growth remains poorly understood. Therefore, the present study aimed to determine the expression levels of miR-451a in cSCC cell lines and the involvement of miR-451a in cSCC progression. The results revealed that the expression levels of miR-451a were downregulated in cSCC tissues and cell lines, and that this subsequently upregulated 3-phosphoinositide-dependent protein kinase-1 (PDPK1) expression levels. PDPK1 was validated as a direct target of miR-451a in cSCC using bioinformatics software Starbase, dual-luciferase reporter gene assays and western blotting. Additionally, CCK-8, EdU and Transwell assays, as well as flow cytometry and Hoechst 3325 staining, were performed to assess the malignant aggressiveness of cSCC cells. Overexpression of miR-451a was demonstrated to impair the proliferation, migration, invasion and epithelial-mesenchymal transition (EMT), and promoted apoptosis in cSCC cells by interacting with PDPK1, possibly by direct targeting. Furthermore, the western blotting results indicated that miR-451a overexpression may block the PI3K/AKT signaling pathway by interacting with PDPK1. In conclusion, the findings of the present study suggested that miR-451a may prevent the proliferation, migration, invasion and EMT of cSCC cells through the PDPK1-mediated PI3K/AKT signaling pathway, which may offer potential therapeutic targets for the treatment of cSCC.

Primary mammary angiosarcomas harbor frequent mutations in KDR and PIK3CA and show evidence of distinct pathogenesis

Angiosarcoma (AS) is the most frequent primary sarcoma of the breast but nevertheless remains uncommon, accounting for <0.05% of breast malignancies. Secondary mammary AS arise following radiation therapy for breast cancer, in contrast to primary AS which occur sporadically. Essentially all show aggressive clinical behavior independent of histologic grade and most are treated by mastectomy. MYC amplification is frequently identified in radiation-induced AS but only rarely in primary mammary AS (PMAS). As a heterogeneous group, AS from various anatomic sites have been shown to harbor recurrent alterations in TP53, MAP kinase pathway genes, and genes involved in angiogenic signaling including KDR (VEGFR2) and PTPRB. In part due to its rarity, the pathogenesis of PMAS has not been fully characterized. In this study, we examined the clinical, pathologic, and genomic features of ten cases of PMAS, including one patient with bilateral disease. Recurrent genomic alterations were identified in KDR (70%), PIK3CA/PIK3R1 (70%), and PTPRB (30%), each at higher frequencies than reported in AS across all sites. Six tumors harbored a KDR p.T771R hotspot mutation, and all seven KDR-mutant cases showed evidence suggestive of biallelism (four with loss of heterozygosity and three with two aberrations). Of the seven tumors with PI3K alterations, six harbored pathogenic mutations other than in the canonical PIK3CA residues which are most frequent in breast cancer. Three AS were hypermutated (≥10 mutations/megabase (Mb)); hypermutation was seen concurrent with KDR or PIK3CA mutations. The patient with bilateral disease demonstrated shared alterations, indicative of contralateral metastasis. No MYC or TP53 aberrations were detected in this series. Immunohistochemistry for VEGFR2 was unable to discriminate between KDR-mutant tumors and benign vascular lesions of the breast. These findings highlight the underrecognized frequency of KDR and PIK3CA mutation in PMAS, and a significant subset with hypermutation, suggesting a pathogenesis distinct from other AS.

Inhibition of pyruvate dehydrogenase kinase‑1 by dicoumarol enhances the sensitivity of hepatocellular carcinoma cells to oxaliplatin via metabolic reprogramming

The Warburg effect is a unique metabolic feature of the majority of tumor cells and is closely related to chemotherapeutic resistance. Pyruvate dehydrogenase kinase 1 (PDK1) is considered a 'switch' that controls the fate of pyruvate in glucose metabolism. However, to date, to the best of our knowledge, there are only a few studies to available which had studied the reduction of chemotherapeutic resistance via the metabolic reprogramming of tumor cells with PDK1 as a target. In the present study, it was found dicoumarol (DIC) reduced the phosphorylation of pyruvate dehydrogenase (PDH) by inhibiting the activity of PDK1, which converted the metabolism of human hepatocellular carcinoma (HCC) cells to oxidative phosphorylation, leading to an increase in mitochondrial reactive oxygen species ROS (mtROS) and a decrease in mitochondrial membrane potential (MMP), thereby increasing the apoptosis induced by oxaliplatin (OXA). Furthermore, the present study elucidated that the targeting of PDK1 may be a potential strategy for targeting metabolism in the chemotherapy of HCC. In addition, DIC as an 'old drug' exhibits novel efficacy, bringing new hope for antitumor therapy.

Phospho-inositide-dependent kinase 1 regulates signal dependent translation in megakaryocytes and platelets

BACKGROUND

Regulated protein synthesis is essential for megakaryocyte (MK) and platelet functions, including platelet production and activation. PDK1 (phosphoinositide-dependent kinase 1) regulates platelet functional responses and has been associated with circulating platelet counts. Whether PDK1 also directly regulates protein synthetic responses in MKs and platelets, and platelet production by MKs, remains unknown.

OBJECTIVE

To determine if PDK1 regulates protein synthesis in MKs and platelets.

METHODS

Pharmacologic PDK1 inhibitors (BX-795) and mice where PDK1 was selectively ablated in MKs and platelets (PDK1-/- ) were used. PDK1 signaling in MKs and platelets (human and murine) were assessed by immunoblots. Activation-dependent translation initiation and protein synthesis in MKs and platelets was assessed by probing for dissociation of eIF4E from 4EBP1, and using m7-GTP pulldowns and S35 methionine incorporation assays. Proplatelet formation by MKs, synthesis of Bcl-3 and MARCKs protein, and clot retraction were employed for functional assays.

RESULTS

Inhibiting or ablating PDK1 in MKs and platelets abolished the phosphorylation of 4EBP1 and eIF4E by preventing activation of the PI3K and MAPK pathways. Inhibiting PDK1 also prevented dissociation of eIF4E from 4EBP1, decreased binding of eIF4E to m7GTP (required for translation initiation), and significantly reduced de novo protein synthesis. Inhibiting PDK1 reduced proplatelet formation by human MKs and blocked MARCKs protein synthesis. In both human and murine platelets, PDK1 controlled Bcl-3 synthesis. Inhibition of PDK1 led to complete failure of clot retraction in vitro.

CONCLUSIONS

PDK1 is a previously unidentified translational regulator in MKs and platelets, controlling protein synthetic responses, proplatelet formation, and clot retraction.

Inhibition of Endoglin Exerts Antitumor Effects through the Regulation of Non-Smad TGF-β Signaling in Angiosarcoma

Angiosarcoma is a rare malignant tumor derived from endothelial cells, and its prognosis is poor because advanced angiosarcoma is often resistant to taxane therapy. Endoglin (CD105) acts as a coreceptor for TGF-β signaling and is overexpressed in tumor-associated endothelial cells and enhances tumor angiogenesis. Numerous clinical trials are testing the effectiveness of anti-endoglin antibodies in various types of malignancies. Here, we investigated the role of endoglin in the pathogenesis of angiosarcoma and whether endoglin inhibition results in antitumor activity. Endoglin was overexpressed in angiosarcoma, and its inhibition was effective in promoting apoptosis and the suppression of migration, invasion, tube formation, and Warburg effect in angiosarcoma cells. Knockdown of endoglin activated caspase 3/7 that is essential for apoptosis, reduced survivin levels, and decreased paxillin and vascular endothelial cadherin phosphorylation and matrix metalloproteinase 2 and matrix metalloproteinase 9 activities in angiosarcoma cells. Although endoglin is a coreceptor that regulates TGF-β signaling, the antitumor effect of endoglin in angiosarcoma was not based on Smad signaling regulation but on non-Smad TGF-β signaling. Taken together, these results indicated that endoglin could be a novel therapeutic target for angiosarcoma.

Genome-wide profiling of prognosis-related alternative splicing signatures in sarcoma

BACKGROUND

Sarcomas (SARCs) are rare malignant tumors with poor prognosis. Increasing evidence has suggested that aberrant alternative splicing (AS) is strongly associated with tumor initiation and progression. We considered whether survival-related AS events might serve as prognosis predictors and underlying targeted molecules in SARC treatment.

METHODS

RNA-Seq data of the SARC cohort were downloaded from The Cancer Genome Atlas (TCGA) database. Survival-related AS events were selected by univariate and multivariate Cox regression analyses. Metascape was used for constructing a gene interaction network and performing functional enrichment analysis. Then, prognosis predictors were established based on statistically significant survival-related AS events and evaluated by receiver operator characteristic (ROC) curve analysis. Finally, the potential regulatory network was analyzed via Pearson's correlation between survival-related AS events and splicing factors (SFs).

RESULTS

A total of 3,610 AS events and 2,291 genes were found to be prognosis-related in 261 SARC samples. The focal adhesion pathway was identified as the most critical molecular mechanism corresponding to poor prognosis. Notably, several prognosis predictors based on survival-related AS events showed excellent performance in prognosis prediction. The area under the curve of the ROC of the risk score was 0.85 in the integrated predictor. The splicing network proved complicated regulation between prognosis-related SFs and AS events. Also, driver gene mutations were significantly associated with AS in SARC patients.

CONCLUSIONS

Survival-related AS events may become ideal indictors for the prognosis prediction of SARCs. Corresponding splicing regulatory mechanisms are worth further exploration.

Clinical outcomes in primary scalp angiosarcoma

Scalp angiosarcoma is a rare, extremely aggressive cutaneous malignancy with poor patient prognosis. The present study reviewed the cases of 42 patients who presented scalp angiosarcoma and were treated at the Zhongshan Hospital of Fudan University between January 2002 and December 2013. The clinical characteristics, demographics, treatment regimens and outcomes of patients were analyzed, and the overall survival (OS) and recurrence-free survival (RFS) rates were calculated. A total of 42 patients were examined in this study. Surgery was the most common therapeutic measure, and was performed in 39 patients, alone (12 patients), in combination with chemotherapy (14 patients), radiotherapy (6 patients) or 3-modality-therapy (7 patients). The median follow-up time of patients was 28.5 months. The 5-year OS rate was 19%, and the 5-year RFS rate was 10%. Taken together, the results of the present study suggested that patients whose tumor presented a nodular localized lesion had a significantly improved OS rate (P=0.0078). Patients aged ≥70 years were associated with a lower 5-year OS (P=0.0071) and RFS rates (P=0.0095) vs. patients aged <70 years. Different treatments were not identified to be significantly associated with an improved OS or RFS. The present results also indicated that if the tumor presented nodular localized lesions, the patients exhibited a better prognosis than those with a diffuse lesion. Although younger patients had better clinical outcomes, the likelihood of recurrence and mortality remained high for all patients.

miR‑16‑2‑3p inhibits cell proliferation and migration and induces apoptosis by targeting PDPK1 in maxillary primordium mesenchymal cells

MicroRNAs (miRNAs) post-transcriptionally regulate gene expression by targeting the 3′ untranslated region (UTR) of target genes, and serve diverse roles in cell proliferation, differentiation and apoptosis. However, the association between miR-16-2-3p and 3-phosphoinositide-dependent protein kinase-1 (PDPK1) in nonsyndromic cleft lip (NSCL) remains unclear. In the present study, a luciferase activity assay indicated that miR-16-2-3p negatively regulated PDPK1 in maxillary primordium mesenchymal cells (MPMCs). In addition, it was confirmed that the expression levels of miR-16-2-3p was markedly increased in cleft lip tissues compared with those in adjacent normal lip tissues. A negative correlation between miR-16-2-3p and PDPK1 in cleft lip tissues was observed. Furthermore, miR-16-2-3p inhibited cell proliferation and migration, and induced apoptosis of MPMCs via repressing PDPK1. Finally, miR-16-2-3p exerted its suppressive role in MPMCs by inhibiting the PDPK1/protein kinase B signaling pathway. These results indicate that miR-16-2-3p may inhibit cell proliferation and migration, and promote apoptosis in MPMCs through repression of PDPK1 and may be a potential target for future clinical prevention and treatment of NSCL.

PDK1 inhibitor GSK2334470 exerts antitumor activity in multiple myeloma and forms a novel multitargeted combination with dual mTORC1/C2 inhibitor PP242

A deeper understanding of the complex pathogenesis of multiple myeloma (MM) continues to lead to novel therapeutic approaches. Prior studies suggest that 3-phosphoinositide-dependent kinase 1 (PDK1) is expressed and active, acting as a crucial regulator of molecules that are essential for myelomagenesis. In the present study, we show that GSK2334470 (GSK-470), a novel and highly specific inhibitor of PDK1, induces potent cytotoxicity in MM cell lines including Dexamethasone-resistant cell line, but not in human normal cells. Insulin-like growth factor-1 could not rescue GSK-470-induced cell death. Moreover, GSK-470 down-modulates phosphor-PDK1, thereby inhibiting downstream phosphor-AKT at Thr308 and mTOR complex 1 (mTORC1) activity. However, GSK-470 could not affect mTORC2 activity and phosphor-AKT at Ser473. RPMI 8226 and OPM-2 cells with low expression of PTEN show relative resistant to GSK-470. Knockout of PTEN by shRNA resulted in a partial reversion of GSK-470-mediated growth inhibition, whereas overexpression of PTEN enhanced myeloma cell sensitivity to GSK-470, suggesting that the sensitivity to GSK-470 is correlated with PTEN expression statue in MM cells. Combining PP242, a dual mTORC1/C2 inhibitor, with GSK-470, had greater antimyeloma activity than either one alone in vitro and in MM xenograft model established in immunodeficient mice. In particular, this combination was able to result in a complete inhibition of mTORC1/C2 and full activity of AKT. Together, these findings raise the possibility that combining PDK1 antagonist GSK-470 with mTORC1/C2 inhibitors may represent a novel strategy against MM including drug-resistant myeloma, regardless of PTEN expression status.

PDK1 governs thromboxane generation and thrombosis in platelets by regulating activation of Raf1 in the MAPK pathway

Essentials Phosphoinositide 3-kinase and MAPK pathways crosstalk via PDK1. PDK1 is required for adenosine diphosphate-induced platelet activation and thromboxane generation. PDK1 regulates RAF proto-oncogene Ser/Thr kinase (Raf1) activation in the MAPK pathway. Genetic ablation of PDK1 protects against platelet-dependent thrombosis in vivo.

SUMMARY

Background Platelets are dynamic effector cells with functions that span hemostatic, thrombotic and inflammatory continua. Phosphoinositide-dependent protein kinase 1 (PDK1) regulates protease-activated receptor 4-induced platelet activation and thrombus formation through glycogen synthase kinase3β. However, whether PDK1 also signals through the ADP receptor and its functional importance in vivo remain unknown. Objective To establish the mechanism of PDK1 in ADP-induced platelet activation and thrombosis. Methods We assessed the role of PDK1 on 2MeSADP-induced platelet activation by measuring aggregation, thromboxane generation and phosphorylation events in the presence of BX-795, which inhibits PDK1, or by using platelet-specific PDK1 knockout mice and performing western blot analysis. PDK1 function in thrombus formation was assessed with an in vivo pulmonary embolism model. Results PDK1 inhibition with BX-795 reduced 2-methylthio-ADP (2MeSADP)-induced aggregation of human and murine platelets by abolishing thromboxane generation. Similar results were observed in pdk1-/- mice. PDK1 was also necessary for the phosphorylation of mitogen-activated protein kinase kinase 1/2 (MEK1/2), extracellular signal-regulated kinase 1/2, and cytosolic phospholipase A2, indicating that PDK1 regulates an upstream kinase in the mitogen-activated protein kinase (MAPK) pathway. We next determined that this upstream kinase is Raf-1, a serine/threonine kinase that is necessary for the phosphorylation of MEK1/2, as pharmacological inhibition and genetic ablation of PDK1 were sufficient to prevent Raf1 phosphorylation. Furthermore, in vivo inhibition or genetic ablation of PDK1 protected mice from collagen/epinephrine-induced pulmonary embolism. Conclusion PDK1 governs thromboxane generation and thrombosis in platelets that are stimulated with 2MeSADP by regulating activation of the MAPK pathway.

PDK1-WNK1 signaling is affected by HBx and involved in the viability and metastasis of hepatic cells

Hepatitis B virus (HBV)-encoded X antigen (HBx) contributes to the development of hepatocellular carcinoma (HCC). Although HBx has been implicated in the progression of HCC, its precise function in HBV-associated HCC remains unclear. In the present study, HBx affected 3-phosphoinositide-dependent protein kinase-1 (PDK1) and with-no-lysine (K) kinase (WNK1) signaling, which was identified to be involved in the viability and metastasis of hepatic cells. The phosphorylation of WNK1 was decreased when the hepatic cells were treated with a PDK1 inhibitor. The inhibition of PDK1 activity inhibited the viability and migration of hepatic cells. To the best of our knowledge, the present study is the first to identify the activation of PDK1 in HCC tissues, confirmed using western blot analysis. PDK1-WNK1 signaling may be a potential therapeutic target in HBV-associated liver cancer.

microRNA-145-3p inhibits non-small cell lung cancer cell migration and invasion by targeting PDK1 via the mTOR signaling pathway

The mammalian target of rapamycin (mTOR) pathway is dysregulated in more than 50% of all human malignancies and is a major target in cancer treatment. In this study, we explored the underlying mechanism involving microRNA-145-3p (miR-145-3p) in the development and progression of non-small cell lung cancer (NSCLC) by targeting PDK1 via the mTOR signaling pathway. NSCLC tissues and adjacent normal tissues were obtained from 83 NSCLC patients. miR-145-3p, PDK1, and mTOR levels were determined by quantitative real-time polymerase chain reaction (qRT-PCR) and immunohistochemistry. Human NSCLC cell lines A549 and H1299 were transfected with miR-145-3p and siPDK1 to confirm the effect of miR-145-3p and PDK1 on NSCLC cells in vitro. Cell growth was evaluated by a CCK8 assay. Cell motility and chemotaxis analysis were determined by the scratch test and chemotaxis assay, respectively. The protein levels of PDK1 and mTOR were measured using the western blotting. Results showed lower level of miR-145-3p and higher levels of PDK1 and mTOR in NSCLC tissues compared to the adjacent normal tissues. In vitro results showed that cell growth, cell motility, and chemotaxis were all inhibited in cells transfected with miR-145-3p and those transfected with siPDK. Additionally, dual luciferase reporter gene assay helped confirmed that PDK1 is a target of miR-145. Finally, levels of PDK1, mTOR, and phosphorylated-mTOR were lower in cells transfected with miR-145-3p as well as those with siPDK1. These findings indicate that miR-145-3p may inhibit cell growth, motility, and chemotaxis in NSCLC by targeting PDK1 through suppressing the mTOR pathway.

Enantiomerically pure β-dipeptide derivative induces anticancer activity against human hormone-refractory prostate cancer through both PI3K/Akt-dependent and -independent pathways

The use of peptides that target cancer cells and induce anticancer activities through various mechanisms is developing as a potential anticancer strategy. KUD983, an enantiomerically pure β-dipeptide derivative, displays potent activity against hormone-refractory prostate cancer (HRPC) PC-3 and DU145 cells with submicromolar IC₅₀. KUD983 induced G1 arrest of the cell cycle and subsequent apoptosis associated with down-regulation of several related proteins including cyclin D1, cyclin E and Cdk4, and the de-phosphorylation of RB. The levels of nuclear and total c-Myc protein, which could increase the expression of both cyclin D1 and cyclin E, were profoundly inhibited by KUD983. Furthermore, it inhibited PI3K/Akt and mTOR/p70S6K/4E-BP1 pathways, the key signaling in multiple cellular functions. The transient transfection of constitutively active myristylated Akt (myr-Akt) cDNA significantly rescued KUD983-induced caspase activation but did not blunt the inhibition of mTOR/p70S6K/4E-BP1 signaling cascade suggesting the presence of both Akt-dependent and -independent pathways. Moreover, KUD983-induced effect was enhanced with the down-regulation of anti-apoptotic Bcl-2 members (e.g., Bcl-2, and Mcl-1) and IAP family members (e.g., survivin). Notably, KUD983 induced autophagic cell death using confocal microscopic examination, tracking the level of conversion of LC3-I to LC3-II and flow cytometric detection of acidic vesicular organelles-positive cells. In conclusion, the data suggest that KUD983 is an anticancer β-dipeptide against HRPCs through the inhibition of cell proliferation and induction of apoptotic and autophagic cell death. The suppression of signaling pathways regulated by c-Myc, PI3K/Akt and mTOR/p70S6K/4E-BP1 and the collaboration with down-regulation of Mcl-1 and survivin may explain KUD983-induced anti-HRPC mechanism.

MiR-454 inhibited cell proliferation of human glioblastoma cells by suppressing PDK1 expression

It has been well documented that aberrant expression of microRNAs is associated with carcinogenesis of glioblastoma (GBM), however the underlying mechanisms are not clear. In this present study, we aimed to clarify the biological function of miR-454 in GBM. MiR-454 was identified to be significantly down-regulated in GBM primary tumors and cell lines. Overexpression of miR-454 in GBM cells resulted in arresting cells at G0/G1 phase and thus inhibiting cell proliferation. Bioinformatic analysis predicted 3-phosphoinositide-dependent protein kinase-1 (PDK1) as a target of miR-454 which acted as a tumor promoter gene. Increased miR-454 significantly repressed PDK1 expression, and then regulating cell proliferation and cell cycle regulators, down-regulation of Cyclin D1 and p-pRb and p21 was up-regulated. Taken together, our study has revealed miR-454 as a tumor suppressor in GBM.