Frequent overexpression of PDK1 in primary nasopharyngeal carcinoma is associated with poor prognosis

Relationship between transcriptional expression of pyruvate dehydrogenase and local control of disease in patients with oral cavity carcinomas

BACKGROUND

The altered cellular metabolism is one of the hallmarks of the cancer cells, favoring the process of aerobic glycolysis, known as the Warburg effect. The pyruvate dehydrogenase (PDH) complex is one of the elements involved in this metabolic process. The present study aims to evaluate the relationship between the transcriptional expression of PDHB and the risk of local recurrence in patients with oral cavity carcinomas.

METHODS

We determined the transcriptional expression of PDHB in biopsies from 41 patients with oral cavity carcinomas treated with surgery. The PDHB expression was categorized according to the local control of the disease with a recursive partitioning analysis.

RESULTS

During the follow-up period 13 patients (31.7%) had a local recurrence of the tumor. Considering local disease control as the dependent variable, the recursive partitioning analysis classified the patients in two categories according to high (n=16, 39.0%) or low (n=25, 61.0%) PDHB expression. Five-year local recurrence-free survival for patients with high PDHB expression was 84.8% (95% CI: 65.2-100%), and for patients with low expression it was 54.3% (95% CI: 34.3-74.2 %) (P=0.034). The results of multivariate analysis showed that patients with a low PDHB expression had a 4.90 times higher risk of local recurrence of the tumor (95% CI: 1.02-22.68, P=0.042).

CONCLUSION

There is a relationship between the metabolic characteristics of the tumor and its aggressiveness. According to our results, patients with oral cavity carcinomas with low transcriptional expression levels of PDHB have a significantly higher risk of local tumor recurrence.

Metabolic reprogramming in nasopharyngeal carcinoma: Mechanisms and therapeutic opportunities

The high prevalence of metabolic reprogramming in nasopharyngeal carcinoma (NPC) offers an abundance of potential therapeutic targets. This review delves into the distinct mechanisms underlying metabolic reprogramming in NPC, including enhanced glycolysis, nucleotide synthesis, and lipid metabolism. All of these changes are modulated by Epstein-Barr virus (EBV) infection, hypoxia, and tumor microenvironment. We highlight the role of metabolic reprogramming in the development of NPC resistance to standard therapies, which represents a challenging barrier in treating this malignancy. Furthermore, we dissect the state of the art in therapeutic strategies that target these metabolic changes, evaluating the successes and failures of clinical trials and the strategies to tackle resistance mechanisms. By providing a comprehensive overview of the current knowledge and future directions in this field, this review sets the stage for new therapeutic avenues in NPC.

Metabolic Reprogramming and Immune Evasion in Nasopharyngeal Carcinoma

Nasopharyngeal carcinoma (NPC) is a malignant tumor of the nasopharynx mainly characterized by geographic distribution and EBV infection. Metabolic reprogramming, one of the cancer hallmarks, has been frequently reported in NPCs to adapt to internal energy demands and external environmental pressures. Inevitably, the metabolic reprogramming within the tumor cell will lead to a decreased pH value and diverse nutritional supplements in the tumor-infiltrating micro-environment incorporating immune cells, fibroblasts, and endothelial cells. Accumulated evidence indicates that metabolic reprogramming derived from NPC cells may facilitate cancer progression and immunosuppression by cell-cell communications with their surrounding immune cells. This review presents the dysregulated metabolism processes, including glucose, fatty acid, amino acid, nucleotide metabolism, and their mutual interactions in NPC. Moreover, the potential connections between reprogrammed metabolism, tumor immunity, and associated therapy would be discussed in this review. Accordingly, the development of targets on the interactions between metabolic reprogramming and immune cells may provide assistances to overcome the current treatment resistance in NPC patients.

The oncogenic and prognostic role of PDK1 in the progression and metastasis of ovarian cancer

Ovarian cancer (OC) is the most lethal of gynecological tumors in women. Tumor metabolism has become a new opportunity in the treatment of tumors. Pyruvate dehydrogenase kinase 1 (PDK1), as a key regulatory enzyme implicated in metabolic reprogramming of tumors, abnormally high expressed in various tumors and involved in the regulation of tumor cell biological behavior. However, the role of PDK1 in the occurrence and development of ovarian cancer remains unclear. Our team identified the expression of PDK1 in ovarian cancer cell lines and tissues through RT-PCR and immunohistochemical staining and evaluated the correlation of PDK1 expression with clinicopathologic features of patients and survival analyses. We used a variety of in vitro experiments to explore the influence of PDK1 on proliferation, invasion, migration, colony formation, apoptosis and the cell cycle of ovarian cancer cell lines CAOV3 and SKOV3. PDK1 was highly expressed in ovarian cancer cell lines and OC tissues. High expression of PDK1 was closely correlated to tumor size, FIGO stage, extraovarian metastases status and distribution. Univariate and multivariate Cox regression analysis identified that PDK1 was an independent prognostic factor for overall survival. Moreover, PDK1 was a superior predictor in prognosis of ovarian cancer and the incorporation of CA125 into PDK1 generated a predictive combination that displayed better predictive accuracy for overall survival. Downregulation of PDK1 suppressed the biological behavior of ovarian cancer cells due to S phase arrest and cellular apoptosis. PDK1 may serve as a novel prognostic biomarker, even a promising antineoplastic target of ovarian cancer.

Transcriptome profiling reveals an integrated mRNA-lncRNA signature with predictive value for long-term survival in diffuse large B-cell lymphoma

For patients with diffuse large B-cell lymphoma (DLBCL), survival at 24 months is a milestone for long-term survival. The purpose of this study was to develop a multigene risk score (MGRS) to refine the International Prognostic Index (IPI) model to identify patients with DLBCL at high risk of death within 24 months. Using a robust statistical strategy, we built a MGRS incorporating nine mRNAs and two lncRNAs. Stratification and multivariable Cox regression analysis confirmed the MGRS as an independent risk factor. A nomogram based on IPI+MGRS model was constructed and its calibration plot showed close agreement between predicted 2-year survival rate and observed rate. The 2-year AUC was bigger with the IPI+MGRS model (ΔAUC=0.162; 95%CI 0.1295–0.1903) than with the IPI model, and the IPI+MGRS model more accurately predicted the prognostic risk of DLBCL. The 2-year survival decision curve revealed the IPI+MGRS model was more useful clinically than the IPI model. Functional enrichment analysis showed that the MGRS correlated with cell cycle, DNA replication and repair. The results were validated using an independent external dataset. In conclusion, we successfully developed an integrated mRNA–lncRNA signature to refine the IPI model for predicting long-term survival of patients with DLBCL.

Suppression of G6PD induces the expression and bisecting GlcNAc-branched N-glycosylation of E-Cadherin to block epithelial-mesenchymal transition and lymphatic metastasis

Background

As the rate-limit enzyme of the pentose phosphate pathway, glucose-6-phosphate dehydrogenase (G6PD) plays important roles in tumour progression, but the exact mechanism through which G6PD controls cancer metastasis remains unclear.

Methods

G6PD expression in resected oral squamous cell carcinoma (OSCC) samples was analysed by immunohistochemistry. The effects and mechanism of G6PD suppression on OSCC cell lines were measured by transwell assay, wound healing assay, western and lectin blot, mass spectrometer analysis, ChIP-PCR, and luciferase reporter assay. BALB/c-nude mice were used to establish orthotopic xenograft model.

Results

G6PD expression in the tumours of 105 OSCC patients was associated with lymphatic metastasis and prognosis. In vitro cellular study suggested that G6PD suppression impaired cell migration, invasion, and epithelial-mesenchymal transition. Furtherly, G6PD knockdown activated the JNK pathway, which then blocked the AKT/GSK-3β/Snail axis to induce E-Cadherin expression and transcriptionally regulated MGAT3 expression to promote bisecting GlcNAc-branched N-glycosylation of E-Cadherin. An orthotopic xenograft model further confirmed that dehydroepiandrosterone reduced lymphatic metastatic rate of OSCC, which was partially reversed by JNK inhibition.

Conclusions

Suppression of G6PD promoted the expression and bisecting GlcNAc-branched N-glycosylation of E-Cadherin via activating the JNK pathway, which thus acted on OSCC metastasis.

Glycine metabolomic changes induced by anticancer agents in A549 cells

Glycine plays a key role in rapidly proliferating cancer cells such as A549 cells. Targeting glycine metabolism is considered as a potential means for cancer treatment. However, the drug-induced alterations in glycine metabolism have not yet been investigated. Herein, a total of 34 glycine metabolites were examined in A549 cells with or without anticancer drug treatment. This work showed all tested anticancer agents could alter glycine metabolism in A549 cells including inhibition of pyruvate metabolism and down-regulation of betaine aldehyde and 5'-phosphoribosylglycinamide. Principal component analysis and orthogonal partial least-squares discrimination analysis exhibited the difference between control and each drug-treated group. In general, cisplatin, camptothecin, and SAHA could induce the significant down-regulation of more metabolites, compared with afatinib, gefitinib, and targretin. Both glycine, serine and threonine metabolism, and purine metabolism were significantly disturbed by the treatment with afatinib, gefitinib, and targretin. However, the treatment using cisplatin, camptothecin, and SAHA was considered to be highly responsible for the perturbation of glycine, serine and threonine metabolism, and cysteine and methionine metabolism. Finally, multivariate analysis for control and all drug-treated groups revealed 11 altered metabolites with a significant difference. It implies anti-cancer agents with different mechanisms of action might induce different comprehensive changes of glycine metabolomics. The current study provides fundamental insights into the acquisition of the role of anti-cancer agents in glycine metabolism while suppressing cancer cell proliferation, and may aid the development of cancer treatment targeting glycine metabolism.

Nucleus-located PDK1 regulates growth, invasion and migration of breast cancer cells

AIMS

It is well known that pyruvate dehydrogenase kinase 1 (PDK1) is highly expressed in breast cancer (BC) tissues and promotes tumor growth, but the underlying mechanisms of this process are unclear. Here, we investigated the effects of nuclear PDK1 on growth, migration and invasion in human BC cells.

MAIN METHODS

The sub-cellular localization of PDK1 in BC cells was performed with subcellular fractionation followed by Western blot and immunofluorescence. The localization of PDK1 in breast normal tissue and breast duct carcinoma was detected by Immunohistochemistry. Then the protein-protein interaction between PDK1 and Importin β was verified by co-immunoprecipitation assay. Finally, the effects of nuclear PDK1 on cell proliferation, apoptosis, migration and invasion of BC cells were assessed.

KEY FINDINGS

In addition to its well-known sub-cellular localization, PDK1 was present in the nucleus of BC cells, and EGF treatment increased nucleus distribution of PDK1. Moreover, the level of nuclear PDK1 accumulation facilitated the growth of BC cells. We also found that the entry of PDK1 into nucleus mainly relied on the nuclear localization signal (NLS), and NLS mutation inhibited the entry of PDK1 into nucleus; as a result, the migration and invasion abilities of BC cells were impaired, and the number of apoptotic cells was significantly increased.

SIGNIFICANCE

Our findings provided a new supplement to the sub-cellular localization of PDK1 in BC cells and uncovered the function of nuclear PDK1 in facilitating BC cells growth, migration and invasion.

miR-375 Inhibits the Proliferation and Invasion of Nasopharyngeal Carcinoma Cells by Suppressing PDK1

Purpose

In patients with nasopharyngeal carcinoma (NPC), the expression of PDK1 is remarkably improved in NPC tissue and correlated with the clinicopathological severity of NPC. We expressed miR-375 in NPC cells to study the effects on PDK1 gene expression. We also investigated the mechanism by which miR-375 affects the biological behavior of NPC cells through effects on PDK1.

Methods

qRT-PCR was carried out to analyze miR-375 and PDK1 levels in NPC cells. NPC cells were transfected with miR-375 inhibitor or miR-375 mimic. CCK-8 testing, colony formation testing, transwell testing, and flow cytometry analysis were carried out to quantify the cells' biological behavior. Rescue experiments demonstrated that the recovery of PDK1 expression was able to reverse the influence of miR-375 inhibition on NPC diffusion and intrusion. The interaction between miR-375 and PDK1 was verified by dual-luciferase reporter gene testing.

Results

The results revealed that miR-375 has a negative regulatory effect on PDK1 expression in NPC cells. Furthermore, PDK1 is a target gene for miR-375. The empirical results obtained demonstrated a negative correlation between tumor development and the level of miR-375 expression in NPC tissues. The excessive expression of miR-375 and the downregulation of PDK1 facilitated the diffusion and invasion of NPC cells.

Conclusion

The diffusion and incursion of NPC cells may be inhibited by direct targeting of PDK1 and decreasing the expression of miR-375. Our study highlights efforts to target PDK1 and miR-375 as potential therapeutic strategies for use in the treatment of NPC.

MicroRNA-503 Inhibits Non-Small Cell Lung Cancer Progression By Targeting PDK1/PI3K/AKT Pathway

OBJECTIVES

The aim of the study was to study the role of dysregulated expression of a microRNA (miRNA), miR-503, in non-small-cell lung cancer (NSCLC) and investigate the underlying mechanism.

METHODS

Quantitative real-time PCR (qRT-PCR) and in situ hybridization staining (ISH) were used to evaluate the expression level of miR-503 in NSCLC tissues and paired adjacent tissues. CCK-8, colony formation and flow cytometry were performed to explore the effects of miR-503 overexpression on cell proliferation, colony formation and apoptosis. Cells with miR-503 overexpression were used to initiate xenograft models. Dual luciferase reporter assay, qRT-PCR, immunohistochemistry and Western blotting were conducted to investigate the interaction of miR-503 and its potential target.

RESULTS

Significantly downregulated miR-503 was found in NSCLC tumor tissues and cell lines. miR-503 overexpression significantly inhibited NSCLC cell proliferation, migration and invasion. PDK1 was predicted as the direct targets of miR-503. PDK1 overexpression reversed the inhibitory effects of miR-503 on biological functions, while PDK1 silencing significantly counteracted miR-503 inhibitor-induced pro-tumor effects in A549 cells. Mechanistically, upregulation of miR-503 inhibited PDK1 expression and subsequently caused the inactivation of PI3K/AKT pathway.

CONCLUSION

Our results suggest that miR-503 inhibits NSCLC progression by targeting PDK1/PI3K/AKT pathway, potentiating the use of miR-503 as a biomarker and therapeutic target for NSCLC.

Microenvironmental control of glucose metabolism in tumors by regulation of pyruvate dehydrogenase

During malignant progression cancer cells undergo a series of changes, which promote their survival, invasiveness and metastatic process. One of them is a change in glucose metabolism. Unlike normal cells, which mostly rely on the tricarboxylic acid cycle (TCA), many cancer types rely on glycolysis. Pyruvate dehydrogenase complex (PDC) is the gatekeeper enzyme between these two pathways and is responsible for converting pyruvate to acetyl-CoA, which can then be processed further in the TCA cycle. Its activity is regulated by PDP (pyruvate dehydrogenase phosphatases) and PDHK (pyruvate dehydrogenase kinases). Pyruvate dehydrogenase kinase exists in 4 tissue specific isoforms (PDHK1-4), the activities of which are regulated by different factors, including hormones, hypoxia and nutrients. PDHK1 and PDHK3 are active in the hypoxic tumor microenvironment and inhibit PDC, resulting in a decrease of mitochondrial function and activation of the glycolytic pathway. High PDHK1/3 expression is associated with worse prognosis in patients, which makes them a promising target for cancer therapy. However, a better understanding of PDC's enzymatic regulation in vivo and of the mechanisms of PDHK-mediated malignant progression is necessary for the design of better PDHK inhibitors and the selection of patients most likely to benefit from such inhibitors.

The role of long non-coding RNA AFAP1-AS1 in human malignant tumors

OBJECTIVES

Long non-coding RNAs (lncRNAs) are a type Table of endogenous RNA longer than 200 nucleotides in length, and this kind of RNAs lack or possess limited ability of coding proteins. A large number of studies have demonstrated that lncRNAs could take part in massive biological processes, such as transcriptional activation and interference, cellular differentiation, proliferation, migration, invasion and apoptosis. The abnormal expression of lncRNAs has been clarified to play extremely important roles in various diseases, especially in human cancers. LncRNA actin filament-associated protein 1 antisense RNA 1 (AFAP1-AS1) is a newly recognized cancer-related lncRNA deriving from the antisense strand of DNA at the AFAP1 coding gene locus. A slew of new studies suggest that AFAP1-AS1 is involved in many kinds of malignant tumors. Moreover, in recent years, the dysregulated expression of AFAP1-AS1 has been confirmed to be associated with oncogenesis and tumor progression. Evidence has increasingly shown that AFAP1-AS1 could probably serve as a novel potential molecular biomarker in tumor diagnosis and therapeutic target in tumor treatment. In this review, we sum up present stage new hottest research issues in respect of the biological functions and molecular mechanisms of AFAP1-AS1 in occurrence and progression of human tumors.

MATERIALS AND METHODS

In this review, we summarize the recent researches about the expression and molecular biological mechanisms of lncRNA AFAP1-AS1 in tumor development. Existing relevant studies are acquired and analyzed by searching Pubmed, BioMedNet, GEO database and Academic Search Elit systematically.

RESULTS

Long non-coding RNA AFAP1-AS1 is an important tumor-associated lncRNA and its aberrant expression has been found in many malignancies so far, including pancreatic ductal adenocarcinoma, cholangiocarcinoma, gallbladder cancer, hepatocellular carcinoma, gastric cancer, colorectal cancer, esophageal cancer, nasopharyngeal carcinoma, lung cancer, ovarian cancer, breast cancer, retinoblastoma, laryngeal cancer, tongue squamous cell carcinoma and thyroid cancer. In addition, the dysregulated expression of AFAP1-AS1 is related to carcinogensis, overall survival (OS), disease-free survival (DFS), progression-free survival (PFS) and tumor progression containing lymph node metastasis, distant metastasis, histological grade, tumor size and tumor stage.

CONCLUSIONS

A series of studies provide detailed information to understand lncRNA AFAP1-AS1 role in various human cancers. LncRNA AFAP1-AS1 is an oncogene in tumors that have been studied so far, and it may act as a useful tumor biomarker and therapeutic target.

MiR-613 suppressed the laryngeal squamous cell carcinoma progression through regulating PDK1

MicroRNAs (miRNAs) are aberrantly expressed in several tumors and play important role in tumorigenesis. However, little is known about the role of miR-613 in laryngeal squamous cell carcinoma (LSCC). We determined the expression of miR-613 in a panel of 30 LSCC specimens. Compared with the adjacent normal samples, 20 cases of LSCC tissues exhibited decreased expression of miR-613. The average expression of miR-613 in LSCC tissues was lower than in normal samples. Moreover, we demonstrated that exogenous expression of miR-613 suppressed LSCC cell proliferation, invasion, and blocked G1/S phase transition. We identified that 3-phosphoinositide-dependent protein kinase-1 (PDK1) was a direct target gene of miR-613 in LSCC cell. Overexpression of miR-613 suppressed PDK1 expression in LSCC cell. Furthermore, we demonstrated that PDK1 was upregulated in LSCC tissues. MiR-613 expression was inversely correlated with the expression of PDK1 in LSCC tissues. Moreover, we showed that PDK1 was involved in the miR-613-mediated cancer suppression of LSCC cell. These results suggested that miR-613 played as a tumor suppressor gene in LSCC partly by inhibiting PDK1 expression.