Pyruvate kinase M2 (PKM2) expression correlates with prognosis in solid cancers: a meta-analysis

Targeted suppression of oral squamous cell carcinoma by pyrimidine-tethered quinoxaline derivatives

Oral cancer (OC) stands as a prominent cause of global mortality. Despite numerous efforts in recent decades, the efficacy of novel therapies to extend the lifespan of OC patients remains disappointingly low. Consequently, the demand for innovative therapeutic agents has become all the more pressing. In this context, we present our work on the design and synthesis of twenty-five novel quinoxaline-tethered imidazopyri(mi)dine derivatives. This was followed by comprehensive investigations into the impact of these molecules on the OC cell line. The in vitro cytotoxicity studies performed in CAL-27 and normal oral epithelial (NOE) cell lines revealed that some of the synthesized molecules like 12d have potent antiproliferative activity specifically towards OC cells with an IC50 of 0.79 μM and show negligible cytotoxicity over NOE cells. Further, 12d arrested cell growth in the S phase of the cell cycle and induced cell death by early apoptosis. The in silico studies validated that 12d binds to the activator binding site on pyruvate kinase M2 (PKM2) overexpressed in OC while the lactate dehydrogenase (LDH)-coupled enzyme assay established 12d as a potent PKM2 activator with an AC50 of 0.6 nM. Hence, this study provides fruitful evidence for the designed compounds as anticancer agents against OC.

PKM2 promotes glioma progression by mediating CTNNB1 expression

BACKGROUND

Glioma is a common intracranial tumor, exhibiting a high degree of aggressiveness and invasiveness. Pyruvate kinase M2 (PKM2) is overexpressed in glioma tissues. However, the biological role of PKM2 in glioma is unclear.

METHODS

The qRT-PCR, CCK-8, Transwell, flow cytometry detection, western blot assays, ELISA assay, and pyruvate kinase activity assays were performed in glioma cells transfected with PKM2 shRNA to explore the function of PKM2 in glioma progression. Then, STRING website was used to predict the proteins that interacted with PKM2, and Co-IP assay was conducted to further validate their interaction. Subsequently, the above experiments were performed again to find the effect of catenin beta 1 (CTNNB1) overexpression on PKM2-deficient glioma cells. The transplanted tumor models were also established to further validate our findings.

RESULTS

PKM2 was up-regulated in glioma cells and tissues. After inhibiting PKM2, the proliferation, migration, glycolysis, and EMT of glioma cells were significantly decreased, and the proportion of apoptosis was increased. The prediction results of STRING website showed that CTNNB1 and PKM2 had the highest interaction score. The correlation between CTNNB1 and PKM2 was further confirmed by Co-IP test. PKM2 knockdown suppressed glioma cell proliferation, migration, glycolysis, and EMT, while CTNNB1 overexpression rescued these inhibitory effects. Correspondingly, PKM2 knockdown inhibited glioma growth in vivo.

CONCLUSION

In summary, these findings indicated that PKM2 promotes glioma progression by mediating CTNNB1 expression, providing a possible molecular marker for the clinical management of gliomas.

Apoptin Inhibits Glycolysis and Regulates Autophagy by Targeting Pyruvate Kinase M2 (PKM2) in Lung Cancer A549 Cells

BACKGROUND

Pyruvate kinase M2 (PKM2) is a key enzyme in aerobic glycolysis and plays an important role in tumor energy metabolism and tumor growth. Ad-apoptin, a recombinant oncolytic adenovirus, can stably express apoptin in tumor cells and selectively causes cell death in tumor cells.

OBJECTIVE

The relationship between the anti-tumor function of apoptin, including apoptosis and autophagy activation, and the energy metabolism of tumor cells has not been clarified.

METHODS

In this study, we used the A549 lung cancer cell line to analyze the mechanism of PKM2 involvement in apoptin-mediated cell death in tumor cells. PKM2 expression in lung cancer cells was detected by Western blot and qRT-PCR. In the PKM2 knockdown and over-expression experiments, A549 lung cancer cells were treated with Ad-apoptin, and cell viability was determined by the CCK-8 assay and crystal violet staining. Glycolysis was investigated using glucose consumption and lactate production experiments. Moreover, the effects of Ad-apoptin on autophagy and apoptosis were analyzed by immunofluorescence using the Annexin v-mCherry staining and by western blot for c-PARP, p62, and LC3-II proteins. Immunoprecipitation analysis was used to investigate the interaction between apoptin and PKM2. In addition, following PKM2 knockdown and overexpression, the expression levels of p-AMPK, p-mTOR, p-ULK1, and p-4E-BP1 proteins in Ad-apoptin treated tumor cells were analyzed by western blot to investigate the mechanism of apoptin effect on the energy metabolism of tumor cells. The in vivo antitumor mechanism of apoptin was analyzed by xenograft tumor inhibition experiment in nude mice and immunohistochemistry of tumors' tissue.

RESULTS

As a result, apoptin could target PKM2, inhibit glycolysis and cell proliferation in A549 cells, and promote autophagy and apoptosis in A549 cells by regulating the PKM2/AMPK/mTOR pathway.

CONCLUSION

This study confirmed the necessary role of Ad-apoptin in the energy metabolism of A549 cells.

Pyruvate kinase M2 (PKM-2) expression and prognostic significance in glioblastoma patients

PURPOSE

Pyruvate kinase M2 (PKM2) is a key enzyme that catalyzes the irreversible and final step of glycolysis. It is closely associated with cancer development and progression. The relationship between PKM2 and prognosis in glioblastoma (GB) patients is unknown. The aim of this study was to measure PKM2 expression and evaluate its effect on prognosis in GB patients.

METHODS

Patients who underwent radiotherapy (RT) for glioblastoma between 2010 and 2021 were evaluated immunohistochemically. A single pathologist evaluated pathology specimens of all patients. The intensity and extent of staining of tumor cells were scored. Patients were categorized as low and high PKM2.

RESULTS

A total of 119 patients were evaluated. While 80.7% of the cases had a low score, 19.3% had a high PKM2 score. It was observed that the group with high PKM2 expression had lower performance, received more hypofractionated RT and received adjuvant chemotherapy (CT) less frequently. Median overall survival (OS) was 15.77 months in the low PKM2 expression group and 6.50 months in the high PKM2 group. In univariate analyses, PKM2 expression, age, performance status, type of surgery, RT scheme, and concurrent and adjuvant CT were prognostic factors in predicting OS. In multivariate analyses, PKM2 expression, type of surgery, RT scheme and receiving adjuvant CT were prognostic factors for OS.

CONCLUSION

PKM2 is an independent prognostic factor for survival and is associated with poor prognosis in GBM patients treated with radiotherapy. It may be a potential therapeutic target for anticancer therapy.

MicroRNA regulation of the serine synthesis pathway in endocrine-resistant breast cancer cells

Despite the successful combination of therapies improving survival of estrogen receptor α (ER+) breast cancer patients with metastatic disease, mechanisms for acquired endocrine resistance remain to be fully elucidated. The RNA binding protein HNRNPA2B1 (A2B1), a reader of N(6)-methyladenosine (m6A) in transcribed RNA, is upregulated in endocrine-resistant, ER+ LCC9 and LY2 cells compared to parental MCF-7 endocrine-sensitive luminal A breast cancer cells. The miRNA-seq transcriptome of MCF-7 cells overexpressing A2B1 identified the serine metabolic processes pathway. Increased expression of two key enzymes in the serine synthesis pathway (SSP), phosphoserine aminotransferase 1 (PSAT1) and phosphoglycerate dehydrogenase (PHGDH), correlates with poor outcomes in ER+ breast patients who received tamoxifen (TAM). We reported that PSAT1 and PHGDH were higher in LCC9 and LY2 cells compared to MCF-7 cells and their knockdown enhanced TAM sensitivity in these-resistant cells. Here we demonstrate that stable, modest overexpression of A2B1 in MCF-7 cells increased PSAT1 and PHGDH and endocrine resistance. We identified four miRNAs downregulated in MCF-7-A2B1 cells that directly target the PSAT1 3'UTR (miR-145-5p and miR-424-5p), and the PHGDH 3'UTR (miR-34b-5p and miR-876-5p) in dual luciferase assays. Lower expression of miR-145-5p and miR-424-5p in LCC9 and ZR-75-1-4-OHT cells correlated with increased PSAT1 and lower expression of miR-34b-5p and miR-876-5p in LCC9 and ZR-75-1-4-OHT cells correlated with increased PHGDH. Transient transfection of these miRNAs restored endocrine-therapy sensitivity in LCC9 and ZR-75-1-4-OHT cells. Overall, our data suggest a role for decreased A2B1-regulated miRNAs in endocrine resistance and upregulation of the SSP to promote tumor progression in ER+ breast cancer.

Role of Glucose Metabolic Reprogramming in Breast Cancer Progression and Drug Resistance

The involvement of glucose metabolic reprogramming in breast cancer progression, metastasis, and therapy resistance has been increasingly appreciated. Studies in recent years have revealed molecular mechanisms by which glucose metabolic reprogramming regulates breast cancer. To date, despite a few metabolism-based drugs being tested in or en route to clinical trials, no drugs targeting glucose metabolism pathways have yet been approved to treat breast cancer. Here, we review the roles and mechanisms of action of glucose metabolic reprogramming in breast cancer progression and drug resistance. In addition, we summarize the currently available metabolic inhibitors targeting glucose metabolism and discuss the challenges and opportunities in targeting this pathway for breast cancer treatment.

Non-coding regions of nuclear-DNA-encoded mitochondrial genes and intergenic sequences are targeted by autoantibodies in breast cancer

Autoantibodies against mitochondrial-derived antigens play a key role in chronic tissue inflammation in autoimmune disorders and cancers. Here, we identify autoreactive nuclear genomic DNA (nDNA)-encoded mitochondrial gene products (GAPDH, PKM2, GSTP1, SPATA5, MFF, TSPOAP1, PHB2, COA4, and HAGH) recognized by breast cancer (BC) patients’ sera as nonself, supporting a direct relationship of mitochondrial autoimmunity to breast carcinogenesis. Autoreactivity of multiple nDNA-encoded mitochondrial gene products was mapped to protein-coding regions, 3’ untranslated regions (UTRs), as well as introns. In addition, autoantibodies in BC sera targeted intergenic sequences that may be parts of long non-coding RNA (lncRNA) genes, including LINC02381 and other putative lncRNA neighbors of the protein-coding genes ERCC4, CXCL13, SOX3, PCDH1, EDDM3B, and GRB2. Increasing evidence indicates that lncRNAs play a key role in carcinogenesis. Consistent with this, our findings suggest that lncRNAs, as well as mRNAs of nDNA-encoded mitochondrial genes, mechanistically contribute to BC progression. This work supports a new paradigm of breast carcinogenesis based on a globally dysfunctional genome with altered function of multiple mitochondrial and non-mitochondrial oncogenic pathways caused by the effects of autoreactivity-induced dysregulation of multiple genes and their products. This autoimmunity-based model of carcinogenesis will open novel avenues for BC treatment.

Modulating Glycolysis to Improve Cancer Therapy

Cancer cells undergo metabolic reprogramming and switch to a 'glycolysis-dominant' metabolic profile to promote their survival and meet their requirements for energy and macromolecules. This phenomenon, also known as the 'Warburg effect,' provides a survival advantage to the cancer cells and make the tumor environment more pro-cancerous. Additionally, the increased glycolytic dependence also promotes chemo/radio resistance. A similar switch to a glycolytic metabolic profile is also shown by the immune cells in the tumor microenvironment, inducing a competition between the cancer cells and the tumor-infiltrating cells over nutrients. Several recent studies have shown that targeting the enhanced glycolysis in cancer cells is a promising strategy to make them more susceptible to treatment with other conventional treatment modalities, including chemotherapy, radiotherapy, hormonal therapy, immunotherapy, and photodynamic therapy. Although several targeting strategies have been developed and several of them are in different stages of pre-clinical and clinical evaluation, there is still a lack of effective strategies to specifically target cancer cell glycolysis to improve treatment efficacy. Herein, we have reviewed our current understanding of the role of metabolic reprogramming in cancer cells and how targeting this phenomenon could be a potential strategy to improve the efficacy of conventional cancer therapy.

Aberrant splicing in human cancer: An RNA structural code point of view

Alternative splicing represents an essential process that occurs widely in eukaryotes. In humans, most genes undergo alternative splicing to ensure transcriptome and proteome diversity reflecting their functional complexity. Over the last decade, aberrantly spliced transcripts due to mutations in cis- or trans-acting splicing regulators have been tightly associated with cancer development, largely drawing scientific attention. Although a plethora of single proteins, ribonucleoproteins, complexed RNAs, and short RNA sequences have emerged as nodal contributors to the splicing cascade, the role of RNA secondary structures in warranting splicing fidelity has been underestimated. Recent studies have leveraged the establishment of novel high-throughput methodologies and bioinformatic tools to shed light on an additional layer of splicing regulation in the context of RNA structural elements. This short review focuses on the most recent available data on splicing mechanism regulation on the basis of RNA secondary structure, emphasizing the importance of the complex RNA G-quadruplex structures (rG4s), and other specific RNA motifs identified as splicing silencers or enhancers. Moreover, it intends to provide knowledge on newly established techniques that allow the identification of RNA structural elements and highlight the potential to develop new RNA-oriented therapeutic strategies against cancer.

The role of autophagy in colorectal cancer: Impact on pathogenesis and implications in therapy

Colorectal cancer (CRC) is considered as a global major cause of cancer death. Surgical resection is the main line of treatment; however, chemo-, radiotherapy and other adjuvant agents are crucial to achieve good outcomes. The tumor microenvironment (TME) is a well-recognized key player in CRC progression, yet the processes linking the cancer cells to its TME are not fully delineated. Autophagy is one of such processes, with a controversial role in the pathogenesis of CRC, with its intricate links to many pathological factors and processes. Autophagy may apparently play conflicting roles in carcinogenesis, but the precise mechanisms determining the overall direction of the process seem to depend on the context. Additionally, it has been established that autophagy has a remarkable effect on the endothelial cells in the TME, the key substrate for angiogenesis that supports tumor metastasis. Favorable response to immunotherapy occurs only in a specific subpopulation of CRC patients, namely the microsatellite instability-high (MSI-H). In view of such limitations of immunotherapy in CRC, modulation of autophagy represents a potential adjuvant strategy to enhance the effect of those relatively safe agents on wider CRC molecular subtypes. In this review, we discussed the molecular control of autophagy in CRC and how autophagy affects different processes and mechanisms that shape the TME. We explored how autophagy contributes to CRC initiation and progression, and how it interacts with tumor immunity, hypoxia, and oxidative stress. The crosstalk between autophagy and the TME in CRC was extensively dissected. Finally, we reported the clinical efforts and challenges in combining autophagy modulators with various cancer-targeted agents to improve CRC patients’ survival and restrain cancer growth.

LncCCAT1 interaction protein PKM2 upregulates SREBP2 phosphorylation to promote osteosarcoma tumorigenesis by enhancing the Warburg effect and lipogenesis

Pyruvate kinase M2 (PKM2) plays an important role in the consumption of glucose and the production of lactic acid, the striking feature of cancer metabolism. The association of PKM2 with osteosarcoma (OS) has been reported but its role in OS has yet to be elucidated. To study this, PKM2‑bound RNAs in HeLa cells, a type of cancer cells widely used in the study of molecular function and mechanism, were obtained. Peak calling analysis revealed that PKM2 binds to long noncoding RNAs (lncRNAs), which are associated with cancer pathogenesis and development. Validation of the PKM2‑lncRNA interaction in the human OS cell line revealed that lncRNA colon cancer associated transcript‑1 (lncCCAT1) interacted with PKM2, which upregulated the phosphorylation of sterol regulatory element‑binding protein 2 (SREBP2). These factors promoted the Warburg effect, lipogenesis, and OS cell growth. PKM2 appears to be a key regulator in OS by binding to lncCCAT1. This further extends the biological functions of PKM2 in tumorigenesis and makes it a novel potential therapeutic for OS.

Metformin overcomes metabolic reprogramming-induced resistance of skin squamous cell carcinoma to photodynamic therapy

Objective

Cancer metabolic reprogramming promotes resistance to therapies. In this study, we addressed the role of the Warburg effect in the resistance to photodynamic therapy (PDT) in skin squamous cell carcinoma (sSCC). Furthermore, we assessed the effect of metformin treatment, an antidiabetic type II drug that modulates metabolism, as adjuvant to PDT.

Methods

For that, we have used two human SCC cell lines: SCC13 and A431, called parental (P) and from these cell lines we have generated the corresponding PDT resistant cells (10GT).

Results

Here, we show that 10GT cells induced metabolic reprogramming to an enhanced aerobic glycolysis and reduced activity of oxidative phosphorylation, which could influence the response to PDT. This result was also confirmed in P and 10GT SCC13 tumors developed in mice. The treatment with metformin caused a reduction in aerobic glycolysis and an increase in oxidative phosphorylation in 10GT sSCC cells. Finally, the combination of metformin with PDT improved the cytotoxic effects on P and 10GT cells. The combined treatment induced an increase in the protoporphyrin IX production, in the reactive oxygen species generation and in the AMPK expression and produced the inhibition of AKT/mTOR pathway. The greater efficacy of combined treatments was also seen in vivo, in xenografts of P and 10GT SCC13 cells.

Conclusions

Altogether, our results reveal that PDT resistance implies, at least partially, a metabolic reprogramming towards aerobic glycolysis that is prevented by metformin treatment. Therefore, metformin may constitute an excellent adjuvant for PDT in sSCC.

•

Cell resistant to Photodynamic therapy (PDT) is due to the metabolic reprogramming.

•

Metformin modulates energetic metabolism in PDT-resistant cells, sensitizing to PDT.

•

Metformin increases protoporphyrin IX and reactive oxygen species generation.

•

Metformin+PDT is proposed as potential therapy against skin squamous cell carcinoma.

PKM2 Is Overexpressed in Glioma Tissues, and Its Inhibition Highly Increases Late Apoptosis in U87MG Cells With Low-density Specificity

BACKGROUND/AIM

Pyruvate kinase M2 (PKM2) functions as an important rate-limiting enzyme in aerobic glycolysis and is involved in tumor initiation and progression. However, there are few studies on the correlation between PKM2 expression and its role in glioma.

MATERIALS AND METHODS

PKM2 expression was immunohistochemically examined in human brain tumor samples. Furthermore, we studied the effects of two PKM2 inhibitors (shikonin and compound 3K) on the U87MG glioma cell line.

RESULTS

PKM2 was overexpressed in most glioma tissues when compared to controls. Interestingly, glioma-adjacent tissues from showed slight PKM2 overexpression. This suggests that PKM2 overexpression maybe an important trigger factor for glioma tumorigenesis. We found that the PKM2 inhibitor shikonin was effective against U87MG cells at a relatively low dose and was largely dependent on low cellular density compared to the effects of the anticancer drug vincristine. Shikonin highly increased late-apoptosis of U87MG cells. We also demonstrated that autophagy was involved in the increase in late-apoptosis levels caused by shikonin. Although vincristine treatment led to a high level of G2-phase arrest in U87MG cells, shikonin did not increase G2 arrest. Co-treatment with two PKM2 inhibitors, shikonin and compound 3K, increased the inhibitory effects.

CONCLUSION

Combination therapy with PKM2 inhibitors together might be more effective than combination therapy with anticancer drugs. Our findings encourage the application of PKM2-targeting in gliomas, and lay the foundation for the development of PKM2 inhibitors as promising antitumor agents for glioma.

Glycolysis in the progression of pancreatic cancer

Metabolic reprogramming, as a key hallmark of cancers, leads to the malignant behavior of pancreatic cancer, which is closely related to tumor development and progression, as well as the supportive tumor microenvironments. Although cells produce adenosine triphosphate (ATP) from glucose by glycolysis when lacking oxygen, pancreatic cancer cells elicit metabolic conversion from oxide phosphorylation to glycolysis, which is well-known as "Warburg effect". Glycolysis is critical for cancer cells to maintain their robust biosynthesis and energy requirement, and it could promote tumor initiation, invasion, angiogenesis, and metastasis to distant organs. Multiple pathways are involved in the alternation of glycolysis for pancreatic cancer cells, including UHRF1/SIRT4 axis, PRMT5/FBW7/cMyc axis, JWA/AMPK/FOXO3a/FAK axis, KRAS/TP53/TIGAR axis, etc. These signaling pathways play an important role in glycolysis and are potential targets for the treatment of pancreatic cancer. Mutations in glycolytic enzymes (such as LDH, PKM2, and PGK1) also contribute to the early diagnosis and monitoring of pancreatic cancer. In this review, we summarized the recent advances on the mechanisms for glycolysis in pancreatic cancer and the function of glycolysis in the progression of pancreatic cancer, which suggested new targets for cancer diagnosis and treatment.

PKM2 Regulates HSP90-Mediated Stability of the IGF-1R Precursor Protein and Promotes Cancer Cell Survival during Hypoxia

Simple Summary

Generally, IGF-1R is overexpressed in most solid tumors, and its expression is significantly associated with poor prognosis in cancer patients. However, IGF-1R gene amplification events are extremely rare in tumors. It is, therefore, necessary to define the mechanism underlying IGR-1R overexpression to elucidate potential therapeutic targets. Our study, specifically, aimed to define the potential mechanisms associated with PKM2 function in regulating IGF-1R protein expression. PKM2 was found to be a non-metabolic protein that regulates HSP90 binding to and stabilizing the precursor IGF-1R protein, thereby promoting the basal level of mature IGF-1R protein. Consequently, PKM2 knockdown inhibits the activation of AKT, a downstream effector of IGF-1R signaling, and increases apoptosis during hypoxia. Our findings reveal a novel mechanism for regulating IGF-1R protein expression, thus suggesting PKM2 as a potential therapeutic target in cancers associated with aberrant IGF signaling.

Abstract

Insulin-like growth factor-1 receptor (IGF-1R), an important factor in promoting cancer cell growth and survival, is commonly upregulated in cancer cells. However, amplification of the IGF1R gene is extremely rare in tumors. Here, we have provided insights into the mechanisms underlying the regulation of IGF-1R protein expression. We found that PKM2 serves as a non-metabolic protein that binds to and increases IGF-1R protein expression by promoting the interaction between IGF-1R and heat-shock protein 90 (HSP90). PKM2 depletion decreases HSP90 binding to IGF-1R precursor, thereby reducing IGF-1R precursor stability and the basal level of mature IGF-1R. Consequently, PKM2 knockdown inhibits the activation of AKT, the key downstream effector of IGF-1R signaling, and increases apoptotic cancer cell death during hypoxia. Notably, we clinically verified the PKM2-regulated expression of IGF-1R through immunohistochemical staining in a tissue microarray of 112 lung cancer patients, demonstrating a significant positive correlation (r = 0.5208, p < 0.0001) between PKM2 and IGF-1R expression. Together, the results of a previous report demonstrated that AKT mediates PKM2 phosphorylation at serine-202; these results suggest that IGF-1R signaling and PKM2 mutually regulate each other to facilitate cell growth and survival, particularly under hypoxic conditions, in solid tumors with dysregulated IGF-1R expression.

Prognostic significance of pyruvate kinase M2 expression in esophageal squamous cell carcinoma and its meta-analysis

BACKGROUND

Pyruvate kinase 2 (PKM2) is a key enzyme in the glycolysis pathway and has been reported to be associated with the development of esophageal squamous cell carcinoma (ESCC). However, the prognostic value of PKM2 in ESCC remains undetermined.

METHODS

This study aimed to investigate the clinicopathological significance of PKM2 expression in ESCC. A comprehensive and systematic literature search was conducted using the PubMed, Embase, Medline, and Cochrane library databases. The quality of studies and potential for bias were appraised, and meta-analysis was performed to assess the prognostic impact of PKM2 on overall survival (OS).

RESULTS

A total of 5 studies with 781 participants were eligible and enrolled. Patients with high PKM2 expression were associated with poor prognosis in ESCC [hazard ratio (HR) =1.72, 95% confidence interval (CI): 1.41-2.09; P<0.01]. Furthermore, upregulated PKM2 was significantly associated with lymph node metastasis [odds ratio (OR) =2.38, 95% CI: 1.68-3.35; P<0.01], clinical stage (OR =3.29, 95% CI: 2.27-4.77; P<0.01), and tumor (T) classification (OR =2.92, 95% CI: 2.05-4.16, P<0.01).

DISCUSSION

High PKM2 expression denotes worse OS in ESCC patients, and correlates with the lymph node metastasis, clinical stage, and T classification. However, further studies are warranted to assess how PKM2 can be implemented as a reliable staging element in clinical practice and whether it could provide a new target for therapeutic intervention.

Expression and clinical significance of pyruvate kinase M2 in breast cancer: A protocol for meta-analysis and bioinformatics validation analysis

BACKGROUND

Breast cancer is a common malignant tumor in women. In recent years, its incidence is increasing year by year, and its morbidity and mortality rank the first place among female malignant tumors. Some key enzymes and intermediates in glycolysis are closely related to tumor development. Pyruvate kinase M2 (PKM2) is an important rate-limiting enzyme in glycolysis pathway. Meanwhile, it is highly expressed in proliferative cells, especially in tumor cells, and plays an important role in the formation of Warburg effect and tumorigenesis. Previous studies have explored the effects of PKM2 expression on the prognosis and clinical significance of breast cancer patients, while the results are contradictory and uncertain. This study uses controversial data for meta-analysis to accurately evaluate the problem. We collected relevant Oncomine and The Cancer Genome Atlas (TCGA) data to further verify the results. Through bioinformatics analysis, the mechanism and related pathways of PKM2 in breast cancer are explored.

METHODS

We searched Wanfang, Chinese Biomedical Literature Database, Chinese National Knowledge Infrastructure, the Chongqing VIP Chinese Science and Technology Periodical Database, PubMed, Embase, and Web of Science databases from inception to March 2021. The language restrictions are Chinese and English. The published literatures on PKM2 expression and prognosis or clinicopathological characteristics of breast cancer patients were statistically analyzed. Combined hazard ratios (HRs), odds ratios (ORs), and 95% confidence intervals (95% CIs) were used to evaluate the effects of PKM2 on the prognosis and clinicopathological features of breast cancer. Stata 14.0 software was applied for meta-analysis. Oncomine and TCGA databases were used to meta-analyze the differences of PKM2 mRNA expression between breast cancer and normal breast tissues. The expression of PKM2 protein was verified by Human Protein Atlas (HPA) database. The relationship between the gene and the survival of breast cancer patients was analyzed by Gene Expression Profiling Interactive Analysis (GEPIA). The relationship between PKM2 gene and clinicopathological characteristics was analyzed by using LinkedOmics, and the Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment pathway analysis was performed by using Metascape. Protein-protein interaction (PPI) network was constructed by String website.

RESULTS

The results of this meta-analysis will be submitted to a peer-reviewed journal for publication.

CONCLUSION

This study provides high-quality medical evidence for the correlation between the expression of PKM2 and the prognosis and clinicopathological features of breast cancer. Through bioinformatics analysis, this study further deepens the understanding of the mechanism and related pathways of PKM2 in breast cancer.

ETHICS AND DISSEMINATION

The private information from individuals will not be published. This systematic review also should not damage participants' rights. Ethical approval is not available. The results may be published in a peer-reviewed journal or disseminated in relevant conferences.

OSF REGISTRATION NUMBER

DOI 10.17605/OSF.IO/W52HB.

Specific Pyruvate Kinase M2 Inhibitor, Compound 3K, Induces Autophagic Cell Death through Disruption of the Glycolysis Pathway in Ovarian Cancer Cells

Ovarian cancer is a common cause of death among gynecological cancers. Although ovarian cancer initially responds to chemotherapy, frequent recurrence in patients remains a therapeutic challenge. Pyruvate kinase M2 (PKM2) plays a pivotal role in regulating cancer cell survival. However, its therapeutic role remains unclear. Here, we investigated the anticancer effects of compound 3K, a specific PKM2 inhibitor, on the regulation of autophagic and apoptotic pathways in SK-OV-3 (PKM2-overexpressing human ovarian adenocarcinoma cell line). The anticancer effect of compound 3K was examined using MTT and colony formation assays in SK-OV-3 cells. PKM2 expression was positively correlated with the severity of the tumor, and expression of pro-apoptotic proteins increased in SK-OV-3 cells following compound 3K treatment. Compound 3K induced AMPK activation, which was accompanied by mTOR inhibition. Additionally, this compound inhibited glycolysis, resulting in reduced proliferation of SK-OV-3 cells. Compound 3K treatment suppressed tumor progression in an in vivo xenograft model. Our findings suggest that the inhibition of PKM2 by compound 3K affected the Warburg effect and induced autophagic cell death. Therefore, use of specific PKM2 inhibitors to block the glycolytic pathway and target cancer cell metabolism represents a promising therapeutic approach for treating PKM2-overexpressing ovarian cancer.

The Glycolytic Pathway as a Target for Novel Onco-Immunology Therapies in Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDA) is one of the most lethal forms of human cancer, characterized by unrestrained progression, invasiveness and treatment resistance. To date, there are limited curative options, with surgical resection as the only effective strategy, hence the urgent need to discover novel therapies. A platform of onco-immunology targets is represented by molecules that play a role in the reprogrammed cellular metabolism as one hallmark of cancer. Due to the hypoxic tumor microenvironment (TME), PDA cells display an altered glucose metabolism-resulting in its increased uptake-and a higher glycolytic rate, which leads to lactate accumulation and them acting as fuel for cancer cells. The consequent acidification of the TME results in immunosuppression, which impairs the antitumor immunity. This review analyzes the genetic background and the emerging glycolytic enzymes that are involved in tumor progression, development and metastasis, and how this represents feasible therapeutic targets to counteract PDA. In particular, as the overexpressed or mutated glycolytic enzymes stimulate both humoral and cellular immune responses, we will discuss their possible exploitation as immunological targets in anti-PDA therapeutic strategies.

Tumor treating fields (TTFields) impairs aberrant glycolysis in glioblastoma as evaluated by [18F]DASA-23, a non-invasive probe of pyruvate kinase M2 (PKM2) expression

Despite the anti-proliferative and survival benefits from tumor treating fields (TTFields) in human glioblastoma (hGBM), little is known about the effects of this form of alternating electric fields therapy on the aberrant glycolysis of hGBM. [18F]FDG is the most common radiotracer in cancer metabolic imaging, but its utility in hGBM is impaired due to high glucose uptake in normal brain tissue. With TTFields, radiochemistry, Western blot, and immunofluorescence microscopy, we identified pyruvate kinase M2 (PKM2) as a biomarker of hGBM response to therapeutic TTFields. We used [18F]DASA-23, a novel radiotracer that measures PKM2 expression and which has been shown to be safe in humans, to detect a shift away from hGBM aberrant glycolysis in response to TTFields. Compared to unexposed hGBM, [18F]DASA-23 uptake was reduced in hGBM exposed to TTFields (53%, P< 0.05) or temozolomide chemotherapy (33%, P > 0.05) for 3 d. A 6-d TTFields exposure resulted in a 31% reduction (P = 0.043) in 60-min uptake of [18F]DASA-23. [18F]DASA-23 was retained after a 10 but not 30-min wash-out period. Compared to [18F]FDG, [18F]DASA-23 demonstrated a 4- to 9-fold greater uptake, implying an improved tumor-to-background ratio. Furthermore, compared to no-TTFields exposure, a 6-d TTFields exposure caused a 35% reduction in [18F]DASA-23 30-min uptake compared to only an 8% reduction in [18F]FDG 30-min uptake. Quantitative Western blot analysis and qualitative immunofluorescence for PKM2 confirmed the TTFields-induced reduction in PKM2 expression. This is the first study to demonstrate that TTFields impairs hGBM aberrant glycolytic metabolism through reduced PKM2 expression, which can be non-invasively detected by the [18F]DASA-23 radiotracer.

Prognostic Biomarkers for Pancreatic Ductal Adenocarcinoma: An Umbrella Review

Background: Pancreatic ductal adenocarcinoma (PDAC) leads to the majority of cancer-related deaths due to its morbidity with similar mortality. Lack of effective prognostic biomarkers are the main reason for belated post-operative intervention of recurrence which causes high mortality. Numerous systematic reviews and meta-analyses have explored the prognostic value of biomarkers in PDAC so far. In this article, we performed an umbrella review analyzing these studies to provide an overview of associations between prognostic biomarkers and PDAC survival outcome and synthesized these results to guide better clinical practice.

Methods: Systematic reviews and meta-analyses investigating the associations between PDAC survival outcomes and prognostic biomarkers were acquired via the PubMed and Embase databases from inception till February 1, 2020. Associations supported by nominally statistically significant results were classified into strong, highly suggestive, suggestive, and weak based on several critical factors such as the statistical significance of summary estimates, the number of events, the estimate of the largest study included, interstudy heterogeneity, small-study effects, 95% predictive interval (PI), excess significance bias, and the results of credibility ceiling sensitivity analyses.

Results: We included 41 meta-analyses containing 63 associations between PDAC survival outcomes and prognostic biomarkers. Although, none was supported by strong evidence among these associations, an association between C-reactive protein to albumin ratio (CAR) and PDAC overall survival (OS) and an association between neutrophil-lymphocyte ratio (NLR) and PDAC OS were supported by highly suggestive evidence. Otherwise, the association between lactate dehydrogenase (LDH) and PDAC OS was supported by suggestive evidence. The remaining 60 associations were supported by weak or not suggestive evidence.

Conclusion: Associations between CAR or NLR and PDAC OS were supported by highly suggestive evidence. And the association between LDH and PDAC OS was supported by suggestive evidence. Although the methodological quality of the included systematic reviews and meta-analyses which were evaluated by AMSTAR2.0 is generally poor, the identification of the relatively robust prognostic biomarkers of PDAC may guide better post-operative intervention and follow-up to prolong patients' survival.

Benserazide is a novel inhibitor targeting PKM2 for melanoma treatment

The M2 splice isoform of pyruvate kinase (PKM2) is a key enzyme for generating pyruvate and ATP in the glycolytic pathway, whereas the role of PKM2 in tumorigenesis remains a subject of debate. In our study, we found PKM2 is highly expressed in melanoma patients and the malignance is positively correlated with high PKM2 activity and glycolytic capability in melanoma cells. Suppression of PKM2 expression by knocking down markedly attenuated malignant phenotype both in vitro and in vivo, and restoration of PKM2 expression in PKM2 depleted cells could rescue melanoma cells proliferation, invasion and metastasis. With the data indicating PKM2 as a potential therapeutic target, we performed screening for PKM2 inhibitors and identified benserazide (Ben), a drug currently in clinical use. We demonstrated that Ben directly binds to and blocks PKM2 enzyme activity, leading to inhibition of aerobic glycolysis concurrent up-regulation of OXPHOS. Of note, despite PKM2 is very similar to PKM1, Ben does not affect PKM1 enzyme activity. We showed that Ben significantly inhibits cell proliferation, colony formation, invasion and migration in vitro and in vivo. The specificity of Ben was demonstrated by the findings that, suppression of PKM2 expression diminishes the efficacy of Ben in inhibition of melanoma cell growth; ectopic PKM2 expression in normal cells sensitizes cells to Ben treatment. Interestingly, PKM2 activity and aerobic glycolysis are upregulated in BRAFi-resistant melanoma cells. As a result, BRAFi-resistant cells exhibit heightened sensitivity to suppression of PKM2 expression or treatment with Ben both in vitro and in vivo.

Phototherapy alters the oncogenic metabolic activity of breast cancer cells

BACKGROUND

Metabolic reprogramming in cancer cells is a strategy to attain a high proliferation rate, invasion, and metastasis. In this study, the effects of phototherapy at different wavelengths were investigated on the metabolic activity of breast cancer cells.

METHODS

The states of the MCF7 cells proliferation and viability were measured by the MTT assay. Glucose consumption and the lactate formation in the LED-irradiated cells culture were analyzed by biochemical assay kits. The Amino acid concentration in the culture media of the MCF7 cells was analyzed using HPLC. Moreover, the gene expression of some glycolytic, TCA cycle and pentose phosphate cycleenzymes were assessed by real time PCR.

RESULTS

Phototherapy at wavelength of 435 nm decreased the cell viability by 23 % when the energy dose was 17.5 J/cm2 compared to the control group. The expression of the LDHA and GLS was up-regulated in 629 nm-treated cells while the expression of these genes was down-regulated in the MCF7 cells irradiated at 435 nm in comparison with the control group. Consequently, the glucose consumption and the lactate formation were diminished respectively by 22 % and 15 % in the 435 nm-irradiated cells while the glucose consumption and the lactate formation were increased in the 629 nm-irradiated cells by 112 % and 107 % in comparison with the control group. In addition, the analysis of the glutamine concentration by the HPLC indicated that the blue light irradiation decreased the glutamine consumption while the red light increased it in comparison with the control group.

Upregulated expression of pyruvate kinase M2 mRNA predicts poor prognosis in lung adenocarcinoma

Background

Pyruvate kinase M2 (PKM2) is critical regulator contributing to Warburg effect. However, the expression pattern and prognostic value of PKM2 remain unknown in lung adenocarcinoma (LUAD). The aim of this study is to clarify the prognostic value of PKM2 via intergrated bioinformatics analysis.

Methods

Firstly, mRNA expression levels of PKM2 in LUAD were systematically analyzed using the ONCOMINE and TCGA databases. Then, the association between PKM2 expression and clinical parameters was investigated by UALCAN. The Kaplan-Meier Plotter was used to assess the prognostic significance of PKM2. Finally, the relationship between PKM2 expression and its genetic and epigenetic changes was evaluated with MEXPRESS and MethHC database.

Results

Pooled analysis showed that PKM2 is frequently upregulated expression in LUAD. Subsequently, PKM2 expression was identified to be positively associated with tumor stage and lymph node metastasis and also strongly correlated with worse OS (P = 2.80e-14), PPS (P = 0.022), FP (P = 1.30e-6) and RFS (P = 3.41e-8). Importantly, our results demonstrated that over-expressed PKM2 is associated with PKM2 hypomethylation and copy number variations (CNVs).

Conclusion

This study confirms that over-expressed PKM2 in LUAD is associated with poor prognosis, suggesting that PKM2 might act as a promising prognostic biomarker and novel therapeutic target for LUAD.

Cysteine catabolism and the serine biosynthesis pathway support pyruvate production during pyruvate kinase knockdown in pancreatic cancer cells

Background

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive cancer with limited treatment options. Pyruvate kinase, especially the M2 isoform (PKM2), is highly expressed in PDAC cells, but its role in pancreatic cancer remains controversial. To investigate the role of pyruvate kinase in pancreatic cancer, we knocked down PKM2 individually as well as both PKM1 and PKM2 concurrently (PKM1/2) in cell lines derived from a Kras^G12D/-; p53^-/- pancreatic mouse model.

Methods

We used liquid chromatography tandem mass spectrometry (LC-MS/MS) to determine metabolic profiles of wildtype and PKM1/2 knockdown PDAC cells. We further used stable isotope-labeled metabolic precursors and LC-MS/MS to determine metabolic pathways upregulated in PKM1/2 knockdown cells. We then targeted metabolic pathways upregulated in PKM1/2 knockdown cells using CRISPR/Cas9 gene editing technology.

Results

PDAC cells are able to proliferate and continue to produce pyruvate despite PKM1/2 knockdown. The serine biosynthesis pathway partially contributed to pyruvate production during PKM1/2 knockdown: knockout of phosphoglycerate dehydrogenase in this pathway decreased pyruvate production from glucose. In addition, cysteine catabolism generated ~ 20% of intracellular pyruvate in PDAC cells. Other potential sources of pyruvate include the sialic acid pathway and catabolism of glutamine, serine, tryptophan, and threonine. However, these sources did not provide significant levels of pyruvate in PKM1/2 knockdown cells.

Conclusion

PKM1/2 knockdown does not impact the proliferation of pancreatic cancer cells. The serine biosynthesis pathway supports conversion of glucose to pyruvate during pyruvate kinase knockdown. However, direct conversion of serine to pyruvate was not observed during PKM1/2 knockdown. Investigating several alternative sources of pyruvate identified cysteine catabolism for pyruvate production during PKM1/2 knockdown. Surprisingly, we find that a large percentage of intracellular pyruvate comes from cysteine. Our results highlight the ability of PDAC cells to adaptively rewire their metabolic pathways during knockdown of a key metabolic enzyme.

Primary prostate cancer educates bone stroma through exosomal pyruvate kinase M2 to promote bone metastasis

Prostate cancer (PCa) metastasizes selectively to bone through unknown mechanisms. In the current study, we identified exosome-mediated transfer of pyruvate kinase M2 (PKM2) from PCa cells into bone marrow stromal cells (BMSCs) as a novel mechanism through which primary tumor-derived exosomes promote premetastatic niche formation. We found that PKM2 up-regulates BMSC CXCL12 production in a HIF-1α-dependent fashion, which subsequently enhances PCa seeding and growth in the bone marrow. Furthermore, serum-derived exosomes from patients with either primary PCa or PCa metastasis, as opposed to healthy men, reveal that increased exosome PKM2 expression is associated with metastasis, suggesting clinical relevance of exosome PKM2 in PCa. Targeting the exosome-induced CXCL12 axis diminished exosome-mediated bone metastasis. In summary, primary PCa cells educate the bone marrow to create a premetastatic niche through primary PCa exosome-mediated transfer of PKM2 into BMSCs and subsequent up-regulation of CXCL12. This novel mechanism indicates the potential for exosome PKM2 as a biomarker and suggests therapeutic targets for PCa bone metastasis.

Gene expression association study in feline mammary carcinomas

Works on cancer-related genes expression using feline mammary carcinomas (FMCs) are scarce but crucial, not only to validate these tumours as models for human breast cancer studies but also to improve small animal practice. Here, the expression of the cancer-related genes TP53, CCND1, FUS, YBX1, PTBP1, c-MYC and PKM2 was evaluated by real-time RT-qPCR, in a population of FMCs clinically characterized and compared with the disease-free tissue of the same individual. In most of the FMCs analysed, RNA quantification revealed normal expression levels for TP53, c-MYC, YBX1 and FUS, but overexpression in the genes CCND1, PTBP1 and PKM2. The expression levels of these cancer-related genes are strongly correlated with each other, with exception of c-MYC and PKM2 genes. The integration of clinicopathological data with the transcriptional levels revealed several associations. The oral contraceptive administration showed to be positively related with the TP53, YBX1, CCND1, FUS and PTBP1 RNA levels. Positive associations were found between tumour size and YBX1 RNA, and lymph node metastasis with c-MYC RNA levels. This work allowed to verify that many of these cancer-related genes are associated but may also, indirectly, influence other genes, creating a complex molecular cancer network that in the future can provide new cancer biomarkers.

Multi-dimensional immunoproteomics coupled with in vitro recapitulation of oncogenic NRASQ61R identifies diagnostically relevant autoantibody biomarkers in thyroid neoplasia

Tumor-associated antigen (TAA)-specific autoantibodies have been widely implicated in cancer diagnosis. However, cancer cell lines that are typically exploited as candidate TAA sources in immunoproteomic studies may fail to accurately represent the autoantigen-ome of lower-grade neoplasms. Here, we established an integrated strategy for the identification of disease-relevant TAAs in thyroid neoplasia, which combined NRAS^Q61R oncogene expression in non-tumorous thyroid Nthy-ori 3-1 cells with a multi-dimensional proteomic technique DISER that consisted of profiling NRAS^Q61R-induced proteins using 2-dimensional difference gel electrophoresis (2D-DIGE) coupled with serological proteome analysis (SERPA) of the TAA repertoire of patients with thyroid encapsulated follicular-patterned/RAS-like phenotype (EFP/RLP) tumors. We identified several candidate cell-based (nicotinamide phosphoribosyltransferase NAMPT, glutamate dehydrogenase GLUD1, and glutathione S-transferase omega-1 GSTO1) and autoantibody (fumarate hydratase FH, calponin-3 CNN3, and pyruvate kinase PKM autoantibodies) biomarkers, including NRAS^Q61R-induced TAA phosphoglycerate kinase 1 PGK1. Meta-profiling of the reactivity of the identified autoantibodies across an independent SERPA series implicated the PKM autoantibody as a histological phenotype-independent biomarker of thyroid malignancy (11/38 (29%) patients with overtly malignant and uncertain malignant potential (UMP) tumors vs 0/22 (p = 0.0046) and 0/20 (p = 0.011) patients with non-invasive EFP/RLP tumors and healthy controls, respectively). PGK1 and CNN3 autoantibodies were identified as EFP/RLP-specific biomarkers, potentially suitable for further discriminating tumors with different malignant potential (PGK1: 7/22 (32%) patients with non-invasive EFP/RLP tumors vs 0/38 (p = 0.00044) and 0/20 (p = 0.0092) patients with other tumors and healthy controls, respectively; СNN3: 9/29 (31%) patients with malignant and borderline EFP/RLP tumors vs 0/31 (p = 0.00068) and 0/20 (p = 0.0067) patients with other tumors and healthy controls, respectively). The combined use of PKM, CNN3, and PGK1 autoantibodies allowed the reclassification of malignant/UMP tumor risk in 19/41 (46%) of EFP/RLP tumor patients. Taken together, we established an experimental pipeline DISER for the concurrent identification of cell-based and TAA biomarkers. The combination of DISER with in vitro oncogene expression allows further targeted identification of oncogene-induced TAAs. Using this integrated approach, we identified candidate autoantibody biomarkers that might be of value for differential diagnostic purposes in thyroid neoplasia.

Pyruvate kinase M2: A multifarious enzyme in non-canonical localization to promote cancer progression

Rewiring glucose metabolism, termed as Warburg effect or aerobic glycolysis, is a common signature of cancer cells to meet their high energetic and biosynthetic demands of rapid growth and proliferation. Pyruvate kinase M2 isoform (PKM2) is a key player in such metabolic reshuffle, which functions as a rate-limiting glycolytic enzyme in the cytosol of highly-proliferative cancer cells. During the recent decades, PKM2 has been extensively studied in non-canonical localizations such as nucleus, mitochondria, and extracellular secretion, and pertained to novel biological functions in tumor progression. Such functions of PKM2 open a new avenue for cancer researchers. This review summarizes up-to-date functions of PKM2 at various subcellular localizations of cancer cells and draws attention to the translocation of PKM2 from cytosol into the nucleus induced by posttranslational modifications. Moreover, PKM2 in tumor cells could have an important role in resistance acquisition processes against various chemotherapeutic drugs, which have raised a concern on PKM2 as a potential therapeutic target. Finally, we summarize the current status and future perspectives to improve the potential of PKM2 as a therapeutic target for the development of anticancer therapeutic strategies.

Tumor pyruvate kinase M2: A promising molecular target of gastrointestinal cancer

Gastrointestinal (GI) cancer is one of the most common causes of cancer-related deaths worldwide. Tumor markers are valuable in detecting post-surgical recurrence or in monitoring response to chemotherapy. Pyruvate kinase isoform M2 (PKM2), a glycolytic enzyme catalyzing conversion of phosphoenolpyruvate (PEP) to pyruvate, confers a growth advantage to the tumor cells and enables them to adapt to the tumor microenvironment. In this review, we have summarized current research on the expression and regulation of PKM2 in tumor cells, and its potential role in GI carcinogenesis and progression. Furthermore, we have also discussed the potential of PKM2 as a diagnostic and screening marker, and a therapeutic target in GI cancer.

PKM2 is not required for pancreatic ductal adenocarcinoma

BACKGROUND

While most cancer cells preferentially express the M2 isoform of the glycolytic enzyme pyruvate kinase (PKM2), PKM2 is dispensable for tumor development in several mouse cancer models. PKM2 is expressed in human pancreatic cancer, and there have been conflicting reports on the association of PKM2 expression and pancreatic cancer patient survival, but whether PKM2 is required for pancreatic cancer progression is unknown. To investigate the role of PKM2 in pancreatic cancer, we used a conditional allele to delete PKM2 in a mouse model of pancreatic ductal adenocarcinoma (PDAC).

RESULTS

PDAC tumors were initiated in LSL-Kras G12D/+ ;Trp53 flox/flox ;Pdx-1-Cre (KP-/-C) mice harboring a conditional Pkm2 allele. Immunohistochemical analysis showed PKM2 expression in wild-type tumors and loss of PKM2 expression in tumors from Pkm2 conditional mice. PKM2 deletion had no effect on overall survival or tumor size. Loss of PKM2 resulted in pyruvate kinase M1 (PKM1) expression, but did not affect the number of proliferating cells. These findings are consistent with results in other cancer models.

CONCLUSIONS

PKM2 is not required for initiation or growth of PDAC tumors arising in the KP-/-C pancreatic cancer model. These findings suggest that, in this mouse PDAC model, PKM2 expression is not required for pancreatic tumor formation or progression.

The multifaceted role of autophagy in cancer and the microenvironment

Autophagy is a crucial recycling process that is increasingly being recognized as an important factor in cancer initiation, cancer (stem) cell maintenance as well as the development of resistance to cancer therapy in both solid and hematological malignancies. Furthermore, it is being recognized that autophagy also plays a crucial and sometimes opposing role in the complex cancer microenvironment. For instance, autophagy in stromal cells such as fibroblasts contributes to tumorigenesis by generating and supplying nutrients to cancerous cells. Reversely, autophagy in immune cells appears to contribute to tumor‐localized immune responses and among others regulates antigen presentation to and by immune cells. Autophagy also directly regulates T and natural killer cell activity and is required for mounting T‐cell memory responses. Thus, within the tumor microenvironment autophagy has a multifaceted role that, depending on the context, may help drive tumorigenesis or may help to support anticancer immune responses. This multifaceted role should be taken into account when designing autophagy‐based cancer therapeutics. In this review, we provide an overview of the diverse facets of autophagy in cancer cells and nonmalignant cells in the cancer microenvironment. Second, we will attempt to integrate and provide a unified view of how these various aspects can be therapeutically exploited for cancer therapy.

PKM2, a potential target for regulating cancer

Aberrated glucose metabolism is a key future of cancer cells. Unlike normal cells, tumor cells favor glycolysis even in the presence of sufficient oxygen. Pyruvate kinase (PK), a key glucose metabolic enzyme, converts phosphoenolpyruvate (PEP) to pyruvate by transferring the high-energy phosphate group to adenosine diphosphate (ADP) to produce adenosine triphosphate (ATP). Pyruvate kinase M2 (PKM2), one of the four isozyme of PK, which universally expressed in rapidly proliferating cells such as embryonic cells and cancer cells. Recent years, more and more research suggested PKM2 plays a crucial role in cancer progression through both metabolic and non-metabolic pathways. On the one hand, the middle product of glycolysis, such as amino acids, nucleotides, lipids is necessary to rapid growth of cancer cells. On the other hand, PKM2 supports tumor growth through regulating the expression of gene that involved in cell proliferation, migration and apoptosis. In this article, we review the recent advances to further understand the regulation and function of PKM2 in tumorigenesis. Given its multiple effects on cancer, PKM2 may be a potential target for cancer diagnosis and treatment.

High PKM2 expression is independently correlated with decreased overall survival in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most lethal and malignant types of cancer that affects global human health. The present study aimed to investigate the effect of pyruvate kinase muscle isozyme M2 (PKM2) expression on the clinical features and prognosis of HCC. The present study employed univariate logistic regression to investigate the correlation between PKM2 expression and clinical features. Univariate and multivariate Cox regression analyses were performed to estimate the independent effect of PKM2 expression on survival status. The results revealed that patients in the high PKM2 group (≥11.25) exhibited significantly lower creatinine levels (P=0.043), higher fetoprotein levels (P<0.001), advanced stage (P<0.001) and higher grade (P=0.004) compared with patients with low PKM2 expression levels (<11.25). In addition, patients with high PKM2 expression exhibited poor prognosis compared with patients with low PKM2 expression. After correcting the covariates, PKM2 expression remains significantly associated with reduced overall survival (P<0.05). These findings suggested that PKM2 is an independent risk factor for HCC and provides valuable information for future studies on the pathogenesis of HCC and drug discovery.

PKM2 under hypoxic environment causes resistance to mTOR inhibitor in human castration resistant prostate cancer

The aim of this study was to explore the efficacy of mTOR inhibitor for castration-resistant prostate cancer (CRPC) under hypoxia. Although under normoxia C4-2AT6, it is a CRPC cell line, expressed elevated pAkt, pS6 and Pyruvate kinase M2 (PKM2) accompanied by elevated HIF-1a expression, 5% hypoxic condition further induced expression of these proteins. These results indicate hypoxic environment elevated PI3K/Akt/mTOR pathway in aggressive prostate cancer. However, C4-2AT6 cells treated with mTOR inhibitor under hypoxia less decreased compared to cells treated with the same dose drugs under normoxia. Western blot analysis showed mTOR inhibitor: RAD001 not only inhibited pS6, but also increased the expression of PKM2 in a dose and time dependent manner. Pyruvate kinase acts on glycolysis. PKM2, which is frequently express in tumor cells, is one isoform of pyruvate kinase. PKM2 is reported to act as a transcription factor. In the present study overexpression of PKM2 in C4-2AT6 induced resistance to RAD001 under normoxia. To evaluate the therapeutic effect of targeting PKM2, we inhibited PKM2 in C4-2AT6 under hypoxia using si-PKM2. The number of C4-2AT6 under chronic hypoxia exposed to siPKM2 significantly decreased compared to intact C4-2AT6 under chronic hypoxia. Furthermore, si-PKM2 improved resistance to mTOR inhibitor in C4-2AT6. When examined using clinical samples, high PKM2 expression was correlated with a high Gleason score and poor PSA free survival. These results suggested that up-regulation of PKM2 is one possibility of resistance to mTOR inhibitor in CRPC. And it is possible that PKM2 is a useful therapeutic target of CRPC.

Pyruvate kinase M2 fuels multiple aspects of cancer cells: from cellular metabolism, transcriptional regulation to extracellular signaling

Originally identified as a metabolic enzyme that catalyzes the transfer of a phosphate group from phosphoenolpyruvate (PEP) to ADP in the glycolytic pathway, pyruvate kinase M2-type (PKM2) has been shown to exhibit novel biological activities in the nucleus and outside the cells. Although cell-based studies reveal new non-canonical functions of PKM2 in gene transcription, epigenetic modulation and cell cycle progression, the importance of these non-canonical functions in PKM2-mediated tumorigenesis is still under debate because studies in genetically modified mice do not consistently echo the findings observed in cultured cancer cells. In addition to regulation of gene expression, the existence of PKM2 in exosomes opens a new venue to study the potential role of this glycolytic enzyme in cell-cell communication and extracellular signal initiation. In this review, we briefly summarize current understanding of PKM2 in metabolic switch and gene regulation. We will then emphasize recent progress of PKM2 in extracellular signaling and tumor microenvironment reprogramming. Finally, the discrepancy of some PKM2’s functions in vitro and in vivo, and the application of PKM2 in cancer detection and treatment will be discussed.

AKT-mediated phosphorylation of ATG4B impairs mitochondrial activity and enhances the Warburg effect in hepatocellular carcinoma cells

Phosphorylation is a major type of post-translational modification, which can influence the cellular physiological function. ATG4B, a key macroautophagy/autophagy-related protein, has a potential effect on the survival of tumor cells. However, the role of ATG4B phosphorylation in cancers is still unknown. In this study, we identified a novel phosphorylation site at Ser34 of ATG4B induced by AKT in HCC cells. The phosphorylation of ATG4B at Ser34 had little effect on autophagic flux, but promoted the Warburg effect including the increase of L-lactate production and glucose consumption, and the decrease of oxygen consumption in HCC cells. The Ser34 phosphorylation of ATG4B also contributed to the impairment of mitochondrial activity including the inhibition of F₁Fo-ATP synthase activity and the elevation of mitochondrial ROS in HCC cells. Moreover, the phosphorylation of ATG4B at Ser34 enhanced its mitochondrial location and the subsequent colocalization with F₁Fo-ATP synthase in HCC cells. Furthermore, recombinant human ATG4B protein suppressed the activity of F₁Fo-ATP synthase in MgATP submitochondrial particles from patient-derived HCC tissues in vitro. In brief, our results demonstrate for the first time that the phosphorylation of ATG4B at Ser34 participates in the metabolic reprogramming of HCC cells via repressing mitochondrial function, which possibly results from the Ser34 phosphorylation-induced mitochondrial enrichment of ATG4B and the subsequent inhibition of F₁Fo-ATP synthase activity. Our findings reveal a noncanonical working pattern of ATG4B under pathological conditions, which may provide a scientific basis for developing novel strategies for HCC treatment by targeting ATG4B and its Ser34 phosphorylation.

Pyruvate kinase isozyme M2 and glutaminase might be promising molecular targets for the treatment of gastric cancer

The aim of this study was to analyze the significance of glucose metabolism-related enzymes in the proliferation of gastric cancer under hypoxia. Four hypoxia-resistant gastric cancer cell lines and four parent cell lines were used. Reverse transcription-PCR was used to evaluate the mRNA expression levels of the following metabolism-related enzymes: pyruvate kinase isozyme M2 (PKM2), glutaminase (GLS), enolase 1 (ENO1), glucose-6-phosphate dehydrogenase (G6PDH), and PKM1. The effects of these enzymes on the proliferation of gastric cancer cells were examined using siRNAs, shikonin as a PKM2 inhibitor, or BPTES as a GLS inhibitor, in vitro and in vivo. Levels of both PKM2 and GLS mRNA were significantly high in all hypoxia-resistant cell lines, compared with those of their parent cells. Knockdown of PKM2 and GLS significantly decreased the proliferation of all hypoxia-resistant cells. The combination of siPKM2 and siGLS significantly decreased proliferation compared with treatment by siPKM2 or siGLS alone. The knockdown of ENO1, G6PDH, or PKM1 did not decrease the proliferation of all hypoxia-resistant cells. Combination treatment using shikonin and BPTES inhibited the proliferation of all hypoxia-resistant cancer cells more than that by either agent alone. The in vivo study indicated that the tumor size treated by the combination of shikonin and BPTES was significantly smaller than that of vehicle-treated group. These findings suggested that PKM2 and GLS might play important roles in the proliferation of hypoxic gastric cancer cells. A combination of PKM2 and GLS inhibitors could be therapeutically promising for the treatment of gastric cancer.

Prognostic significance of metabolic enzyme pyruvate kinase M2 in breast cancer: A meta-analysis

BACKGROUNDS

Numerous studies have reported that aberrant pyruvate kinase M2 isoform (PKM2) expressed in cancer, indicating that PKM2 plays a critical role in tumor initiation and progression. Nevertheless, its prognostic value in breast cancer tumor is yet contentious. Therefore, we performed this meta-analysis to evaluate the prognostic significance of PKM2 in breast cancer.

METHODS

Eligible relevant literatures were retrieved by searching PubMed, the Cochrane Library, Embase through December 2016. Articles that comparing different PKM2 expression levels in human breast cancer tissues and prognostic significance were included. Software RevMan 5.3 and STATA (Review Manager (RevMan): [Computer program]. Version 5.3. Copenhagen: The Nordic Cochrane Centre, The Cochrane Collaboration, 2014.

STATA

StataCorp. 2011. Stata Statistical Software: Release 12. College Station, TX: StataCorp LP) were applied to analyze the outcomes. Pooled results were presented in hazardous ratios (HRs) of 5-year overall survival (OS), progression-free survival (PFS), and odds ratios (ORs) of clinicopathological features with 95% confidence intervals.

RESULTS

Data from 6 involved studies with 895 patients were summarized. Breast cancer patients with high PKM2 had a worse OS (pooled HR = 1.65, 95% CI = 1.31-2.08, P < .001) and PFS (pooled HR = 2.49, 95% CI = 1.84-3.36, P < .00001). High PKM2 expression is related to lymph node metastasis (N1+N2+N3 vs N0, OR = 1.97, 95%CI = 1.39-2.80, P = .0001). The outcome stability was verified via sensitivity analysis. But elevated PKM2 expression was not correlated to tumor stage (T2+T3 vs T1, pooled OR = 0.80, 95% CI = 0.36-1.77, P = .58) and differential grade (G2+G3 vs G1, OR = 2.74, 95%CI = 0.76-9.84, P = .12). No publication bias was found in the included studies for OS (Begg test, P = .260; Egger test, P = .747).

CONCLUSIONS

High PKM2 expression denotes worse OS and PFS in breast cancer patients, and correlate with the lymph node metastasis. However, there is no evidence for the impact of PKM2 expression on T stage and tumor differentiation.

Overexpression of MPC1 inhibits the proliferation, migration, invasion, and stem cell-like properties of gastric cancer cells

Invasion and metastasis are major malignant characteristics of human gastric cancer (GC), but the molecular mechanisms underlying the invasion and metastasis of GC cells remain elusive. MPC1, a key factor that controls pyruvate transportation through the inner mitochondrial membrane, was reported to be downregulated and correlated with poor prognosis in several cancers. However, the effects of MPC1 on human GC have not been illustrated. In this study, we investigated the potential role of MPC1 in the proliferation, migration, invasion, and stem cell-like properties of human GC cells and evaluated its prognostic significance for patients with GC. We found that MPC1 protein and mRNA levels were significantly decreased in GC tissues and cell lines. Low MPC1 expression was associated with tumor T stage, N stage, and advanced tumor node metastasis stage. Decreased MPC1 expression was an independent prognostic marker and correlated with poor overall survival of patients with GC. Furthermore, overexpression of MPC1 inhibited the proliferation, migration, invasion, and stem cell-like properties of GC cells. These findings suggest that MPC1 may be a novel prognostic marker and a potential therapeutic target in human GC.

Correlation between estrogen receptor expression and prognosis in epithelial ovarian cancer: a meta-analysis

OBJECTIVE

Accumulated studies have investigated the prognostic significance of estrogen receptor expression in epithelial ovarian cancer, but results remain controversial. The aim of this study was to perform a meta-analysis to clarify the prognostic value of estrogen receptor expression in epithelial ovarian cancer.

METHODS

A systematic search was performed in PUBMED, EMBASE, and COCHRANE databases to identify relevant studies up to December 2016. The pooled hazard rates (HR) with 95% confidence intervals (CIs) for overall survival and time to tumor progression were calculated and then weighted and pooled in this meta-analysis with a random-effect model.

RESULTS

Thirty-five studies with a total of 5824 patients were included. In brief, the expression of estrogen receptor was associated with an improved overall survival (HR = 0.86, 95% CI = 0.76-0.97), whereas there was no significant difference between estrogen receptor and time to tumor progression among epithelial ovarian cancer patients. Subgroup analysis revealed that estrogen receptor expression was significantly correlated with overall survival in different subgroups, such as in unclassified epithelial ovarian cancer (HR= 0.80, 95% CI = 0.66-0.95), studies using immunohistochemistry detection method (HR= 0.85, 95% CI = 0.73-1.00), European population (HR= 0.75, 95% CI = 0.60-0.94) and estrogen receptor α subtype (HR= 0.78, 95% CI = 0.62-0.98).

CONCLUSIONS

Estrogen receptor, especially estrogen receptor α, was associated with an improved overall survival in epithelial ovarian cancer. Estrogen receptor expression may be a promising prognostic factor in epithelial ovarian cancer patients.

Knockdown of PKM2 and GLS1 expression can significantly reverse oxaliplatin-resistance in colorectal cancer cells

Clinical treatment for colorectal cancer (CRC) thus far encounters a huge challenge due to oxaliplatin-resistance. As crucial rate-limiting enzymes in aerobic glycolysis and glutaminolysis, pyruvate kinase M2 type (PKM2) and kidney-type glutaminase (GLS1) are proposed to carry important implications in colorectal carcinogenesis and drug-resistance. This study aimed to explore the possible association of oxaliplatin-resistance with aerobic glycolysis/glutaminolysis indexed by PKM2/GLS1 expression. PKM2 and GLS1 expression was quantified by polymerase chain reaction (PCR) and Western blot techniques in CRC cell lines. The abilities of cell formation, kinetics, migration, invasion, survival and apoptosis, as well as permeability glycoprotein (Pgp) expression were inspected before and after knocking-down PKM2/GLS1 expression. In addition, the influence of knocking-down PKM2/GLS1 expression was evaluated in vivo. Differentiated PKM2 and GLS1 expression in both THC8307 and THC8307/Oxa cell lines was identified. In the THC8307 cell line, PKM2 and GLS1 can accelerate malignant behaviors, increase oxaliplatin-resistance, upregulate Pgp expression, and inhibit cell apoptosis. Contrastingly in the THC8307/Oxa cell line, knockdown of PKM2/GLS1 expression can restrain malignant behaviors, reestablish oxaliplatin-sensitivity, downregulate Pgp expression, and induce cell apoptosis. In xenograft, knockdown of PKM2/GLS1 expression can significantly inhibit tumor growth, reduce Pgp expression, and increase tumor apoptosis. Taken together, the present findings enriched our knowledge by demonstrating a significant association of PKM2 and GLS1 with oxaliplatin-resistance in CRC. We further propose that knockdown of PKM2/GLS1 expression may constitute a novel therapeutic strategy toward effective treatment for CRC.

Prognostic value of progesterone receptor expression in ovarian cancer: a meta-analysis

OBJECTIVE

While a prognosis value of progesterone receptor (PR) in ovarian cancer has been reported in some publications, controversial data were presented by different reports. In order to address the disagreement of progesterone receptor in ovarian cancer survival, we conducted this meta-analysis.

METHODS

Relevant articles on progesterone receptor and ovarian cancer prognosis were identified via a thorough search of PubMed, Embase and Cochrane Central. Hazard ratios (HR) and 95% confidence interval (CI) were extracted from studies on overall survival (OS) and disease-free survival (DFS)/progress-free survival (PFS)/recurrence-free survival (RFS).

RESULT

A total of 28 eligible studies containing 5685 patients were collected for analysis. It was found that progesterone receptor positivity was significantly associated with favorable overall survival (OS) (HR = 0.86, 95% CI = 0.78 to 0.95, P = 0.002) and disease-free survival (DFS)/progress-free survival (PFS)/recurrence-free survival (RFS) (HR = 0.75, 95% CI = 0.61 to 0.93, P = 0.008) of ovarian cancer patients. Subgroup analysis showed that progesterone receptor expression was associated with a favorable prognosis of unclassified ovarian cancer, European origin, and immunohistochemical detection method.

CONCLUSION

Progesterone receptor expression can be used as a favorable prognostic predictor in ovarian cancer managements.