Changes in PKM2 associate with prostate cancer progression

The expression of PKM1 and PKM2 in developing, benign, and cancerous prostatic tissues

Background

Neuroendocrine prostate cancer (NEPCa) is the most aggressive type of prostate cancer (PCa). However, energy metabolism, one of the hallmarks of cancer, in NEPCa has not been well studied. Pyruvate kinase M (PKM), which catalyzes the final step of glycolysis, has two main splicing isoforms, PKM1 and PKM2. The expression pattern of PKM1 and PKM2 in NEPCa remains unknown.

Methods

In this study, we used immunohistochemistry, immunofluorescence staining, and bioinformatics analysis to examine the expression of PKM1 and PKM2 in mouse and human prostatic tissues.

Results

We found that PKM2 was the predominant isoform expressed throughout prostate development and PCa progression, with slightly reduced expression in murine NEPCa. PKM1 was mostly expressed in stromal cells but low-level PKM1 was also detected in prostate basal epithelial cells. Its expression was absent in the majority of prostate adenocarcinoma (AdPCa) specimens but present in a subset of NEPCa. Additionally, we evaluated the mRNA levels of ten PKM isoforms that express exon 9 (PKM1-like) or exon 10 (PKM2-like). Some of these isoforms showed notable expression levels in PCa cell lines and human PCa specimens.

Discussion

Our study characterized the expression pattern of PKM1 and PKM2 in prostatic tissues including developing, benign, and cancerous prostate. These findings lay the groundwork for understanding the metabolic changes in different PCa subtypes.

Dietary approaches for exploiting metabolic vulnerabilities in cancer

Renewed interest in tumor metabolism sparked an enthusiasm for dietary interventions to prevent and treat cancer. Changes in diet impact circulating nutrient levels in the plasma and the tumor microenvironment, and preclinical studies suggest that dietary approaches, including caloric and nutrient restrictions, can modulate tumor initiation, progression, and metastasis. Cancers are heterogeneous in their metabolic dependencies and preferred energy sources and can be addicted to glucose, fructose, amino acids, or lipids for survival and growth. This dependence is influenced by tumor type, anatomical location, tissue of origin, aberrant signaling, and the microenvironment. This review summarizes nutrient dependencies and the related signaling pathway activations that provide targets for nutritional interventions. We examine popular dietary approaches used as adjuvants to anticancer therapies, encompassing caloric restrictions, including time-restricted feeding, intermittent fasting, fasting-mimicking diets (FMDs), and nutrient restrictions, notably the ketogenic diet. Despite promising results, much of the knowledge on dietary restrictions comes from in vitro and animal studies, which may not accurately reflect real-life situations. Further research is needed to determine the optimal duration, timing, safety, and efficacy of dietary restrictions for different cancers and treatments. In addition, well-designed human trials are necessary to establish the link between specific metabolic vulnerabilities and targeted dietary interventions. However, low patient compliance in clinical trials remains a significant challenge.

The expression of PKM1 and PKM2 in developing, benign, and cancerous prostatic tissues

Neuroendocrine prostate cancer (NEPCa) is the most aggressive type of prostate cancer. However, energy metabolism, one of the hallmarks of cancer, in NEPCa has not been well studied. Pyruvate kinase M (PKM), which catalyzes the final step of glycolysis, has two main splicing isoforms, PKM1 and PKM2. PKM2 is known to be upregulated in various cancers, including prostate adenocarcinoma (AdPCa). In this study, we used immunohistochemistry, immunofluorescence staining, and bioinformatic analysis to examine the expression of PKM1 and PKM2 in mouse and human prostatic tissues, including developing, benign and cancerous prostate. We found that PKM2 was the predominant isoform expressed throughout prostate development and PCa progression, with slightly reduced expression in some NEPCa samples. PKM1 was mostly expressed in stromal cells but low-level PKM1 was also detected in prostate basal epithelial cells. Its expression was absent in the majority of PCa specimens but present in a subset of NEPCa. Additionally, we evaluated the mRNA levels of ten PKM isoforms that express exon 9 (PKM1-like) or exon 10 (PKM2-like). Some of these isoforms showed notable expression levels in PCa cell lines and human PCa specimens. These findings lay the groundwork for understanding PKMs' role in PCa carcinogenesis and NEPCa progression. The distinct expression pattern of PKM isoforms in different PCa subtypes may offer insights into potential therapeutic strategies for treating PCa.

Phytochemicals targeting glycolysis in colorectal cancer therapy: effects and mechanisms of action

Colorectal cancer (CRC) is the third most common malignant tumor in the world, and it is prone to recurrence and metastasis during treatment. Aerobic glycolysis is one of the main characteristics of tumor cell metabolism in CRC. Tumor cells rely on glycolysis to rapidly consume glucose and to obtain more lactate and intermediate macromolecular products so as to maintain growth and proliferation. The regulation of the CRC glycolysis pathway is closely associated with several signal transduction pathways and transcription factors including phosphatidylinositol 3-kinases/protein kinase B/mammalian target of rapamycin (PI3K/AKT/mTOR), adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK), hypoxia-inducible factor-1 (HIF-1), myc, and p53. Targeting the glycolytic pathway has become one of the key research aspects in CRC therapy. Many phytochemicals were shown to exert anti-CRC activity by targeting the glycolytic pathway. Here, we review the effects and mechanisms of phytochemicals on CRC glycolytic pathways, providing a new method of drug development.

A Practical and Analytical Comparative Study of Gel-Based Top-Down and Gel-Free Bottom-Up Proteomics Including Unbiased Proteoform Detection

Proteomics is an indispensable analytical technique to study the dynamic functioning of biological systems via different proteins and their proteoforms. In recent years, bottom-up shotgun has become more popular than gel-based top-down proteomics. The current study examined the qualitative and quantitative performance of these two fundamentally different methodologies by the parallel measurement of six technical and three biological replicates of the human prostate carcinoma cell line DU145 using its two most common standard techniques, label-free shotgun and two-dimensional differential gel electrophoresis (2D-DIGE). The analytical strengths and limitations were explored, finally focusing on the unbiased detection of proteoforms, exemplified by discovering a prostate cancer-related cleavage product of pyruvate kinase M2. Label-free shotgun proteomics quickly yields an annotated proteome but with reduced robustness, as determined by three times higher technical variation compared to 2D-DIGE. At a glance, only 2D-DIGE top-down analysis provided valuable, direct stoichiometric qualitative and quantitative information from proteins to their proteoforms, even with unexpected post-translational modifications, such as proteolytic cleavage and phosphorylation. However, the 2D-DIGE technology required almost 20 times as much time per protein/proteoform characterization with more manual work. Ultimately, this work should expose both techniques' orthogonality with their different contents of data output to elucidate biological questions.

Construction of Glycolytic Regulator Gene Signature to Predict the Prognosis and Tumor Immune Cell Infiltration Levels for Prostate Cancer

Prostate cancer (PCa) is the commonly generated noncutaneous neoplasm among men worldwide. Glycolysis had been validated to promote cancer progression. However, the clinical significance of glycolytic regulators in PCa was not well understood. Here, we discovered that glycolytic regulators were dysregulated in PCa samples using GSE8511, GSE6919, and GEPIA. By detecting the expression of these regulators in PCa samples, we found that SLC2A1, SLC2A3, HK2, PFKFB2, TPI1, PKM2, and LDHA had higher expression in PCa compared with normal tissues. Moreover, both higher expression of TPI1, ALDOA, ENO1, LDHA, and PKM and lower expression of LDHB and HK2 were significantly related to shorter progression-free survival time in PCa. Of note, an 8 gene-based risk score was further constructed and confirmed to have a good performance in predicting progression-free survival (PFS) time in PCa. The signature risk score significantly correlated with NK cell, neutrophil cell, macrophage M2 cell, and myeloid dendritic cell infiltration levels in PCa. After bioinformatics analysis, our data suggested glycolytic regulators participated in the regulation of multiple nonmetabolic biological processes, such as RNA transport, biosynthesis of antibiotics, and cell cycle. We recapitulate that the glycolytic regulator signature was a prospective indicator for prognosis and immune cell infiltration levels in PCa.

Reversal of the Warburg phenomenon in chemoprevention of prostate cancer by sulforaphane

Inhibition of metabolic re-programming represents an attractive approach for prevention of prostate cancer. Studies have implicated increased synthesis of fatty acids or glycolysis in pathogenesis of human prostate cancers. We have shown previously that prostate cancer prevention by sulforaphane (SFN) in Transgenic Adenocarcinoma of Mouse Prostate (TRAMP) model is associated with inhibition of fatty acid metabolism. This study utilized human prostate cancer cell lines (LNCaP, 22Rv1 and PC-3), two different transgenic mouse models (TRAMP and Hi-Myc) and plasma specimens from a clinical study to explore the glycolysis inhibition potential of SFN. We found that SFN treatment: (i) decreased real-time extracellular acidification rate in LNCaP, but not in PC-3 cell line; (ii) significantly downregulated expression of hexokinase II (HKII), pyruvate kinase M2 and/or lactate dehydrogenase A (LDHA) in vitro in cells and in vivo in neoplastic lesions in the prostate of TRAMP and Hi-Myc mice; and (iii) significantly suppressed glycolysis in prostate of Hi-Myc mice as measured by ex vivo1H magnetic resonance spectroscopy. SFN treatment did not decrease glucose uptake or expression of glucose transporters in cells. Overexpression of c-Myc, but not constitutively active Akt, conferred protection against SFN-mediated downregulation of HKII and LDHA protein expression and suppression of lactate levels. Examination of plasma lactate levels in prostate cancer patients following administration of an SFN-rich broccoli sprout extract failed to show declines in its levels. Additional clinical trials are needed to determine whether SFN treatment can decrease lactate production in human prostate tumors.

Overexpression of Pyruvate Kinase M2 in Tumor Tissues Is Associated with Poor Prognosis in Patients with Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the most common malignant tumors, with a high degree of malignancy and a poor prognosis. The aim of this study was to investigate the relationship between expression of pyruvate kinase M2 (PKM2) and prognosis in patients with HCC. The expression levels of PKM2 and PKM1 in 86 cases of HCC were detected by immunohistochemistry. An H score was used to evaluate the expression of PKM, and all patients were further divided into PKM high-expression and PKM low-expression groups. The relationship between PKM2 expression and the clinicopathological parameters and prognosis of patients were subsequently analyzed. Our data suggested that the expression level of PKM2 was significantly higher in HCC tissues than in adjacent tissues and the negatively expression of PKM1 in HCC tissues. Kaplan-Meier analysis revealed that PKM2 expression was strongly associated with survival in HCC patients (P = 0.001). The patients in the PKM2 high-expression group had significantly shorter survival times than the patients in the PKM2 low-expression group (hazard ratio for death, 2.358; 95% confidence interval [1.156, 4.812]; P = 0.018). In conclusion, these data indicate that PKM2 expression in HCC tissue samples can be used as a prognostic factor for patients with HCC and that high PKM2 expression is correlated with a poor prognosis in HCC patients.

Dysregulation of the splicing machinery is directly associated to aggressiveness of prostate cancer

BACKGROUND

Dysregulation of splicing variants (SVs) expression has recently emerged as a novel cancer hallmark. Although the generation of aberrant SVs (e.g. AR-v7/sst5TMD4/etc.) is associated to prostate-cancer (PCa) aggressiveness and/or castration-resistant PCa (CRPC) development, whether the molecular reason behind such phenomena might be linked to a dysregulation of the cellular machinery responsible for the splicing process [spliceosome-components (SCs) and splicing-factors (SFs)] has not been yet explored.

METHODS

Expression levels of 43 key SCs and SFs were measured in two cohorts of PCa-samples: 1) Clinically-localized formalin-fixed paraffin-embedded PCa-samples (n = 84), and 2) highly-aggressive freshly-obtained PCa-samples (n = 42).

FINDINGS

A profound dysregulation in the expression of multiple components of the splicing machinery (i.e. 7 SCs/19 SFs) were found in PCa compared to their non-tumor adjacent-regions. Notably, overexpression of SNRNP200, SRSF3 and SRRM1 (mRNA and/or protein) were associated with relevant clinical (e.g. Gleason score, T-Stage, metastasis, biochemical recurrence, etc.) and molecular (e.g. AR-v7 expression) parameters of aggressiveness in PCa-samples. Functional (cell-proliferation/migration) and mechanistic [gene-expression (qPCR) and protein-levels (western-blot)] assays were performed in normal prostate cells (PNT2) and PCa-cells (LNCaP/22Rv1/PC-3/DU145 cell-lines) in response to SNRNP200, SRSF3 and/or SRRM1 silencing (using specific siRNAs) revealed an overall decrease in proliferation/migration-rate in PCa-cells through the modulation of key oncogenic SVs expression levels (e.g. AR-v7/PKM2/XBP1s) and alteration of oncogenic signaling pathways (e.g. p-AKT/p-JNK).

INTERPRETATION

These results demonstrate that the spliceosome is drastically altered in PCa wherein SNRNP200, SRSF3 and SRRM1 could represent attractive novel diagnostic/prognostic and therapeutic targets for PCa and CRPC.

Shmt2: A Stat3 Signaling New Player in Prostate Cancer Energy Metabolism

Prostate cancer (PCa) is a multifactorial disease characterized by the aberrant activity of different regulatory pathways. STAT3 protein mediates some of these pathways and its activation is implicated in the modulation of several metabolic enzymes. A bioinformatic analysis indicated a STAT3 binding site in the upstream region of SHMT2 gene. We demonstrated that in LNCaP, PCa cells’ SHMT2 expression is upregulated by the JAK2/STAT3 canonical pathway upon IL-6 stimulation. Activation of SHTM2 leads to a decrease in serine levels, pushing PKM2 towards the nuclear compartment where it can activate STAT3 in a non-canonical fashion that in turn promotes a transient shift toward anaerobic metabolism. These results were also confirmed on FFPE prostate tissue sections at different Gleason scores. STAT3/SHMT2/PKM2 loop in LNCaP cells can modulate a metabolic shift in response to inflammation at early stages of cancer progression, whereas a non-canonical STAT3 activation involving the STAT3/HIF-1α/PKM2 loop is responsible for the maintenance of Warburg effect distinctive of more aggressive PCa cells. Chronic inflammation might thus prime the transition of PCa cells towards more advanced stages, and SHMT2 could represent a missing factor to further understand the molecular mechanisms responsible for the transition of prostate cancer towards a more aggressive phenotype.

PKM2-regulated STAT3 promotes esophageal squamous cell carcinoma progression via TGF-β1-induced EMT

Recent studies have demonstrated pleiotropic roles of pyruvate kinase isoenzyme type M2 (PKM2) in tumor progression. However, the precise mechanisms underlying the effects of PKM2 on esophageal squamous cell carcinoma (ESCC) metastasis and transforming growth factor β1 (TGF-β1)-induced epithelial-mesenchymal transition (EMT) remain to be established. In this study, we observed upregulation of PKM2 in ESCC tissues that was markedly associated with lymph node metastasis and poor prognosis. High PKM2 expression in tumor tissues frequently coincided with the high pSTAT3Tyr705 expression and low E-cadherin expression. Furthermore, altered PKM2 expression was significantly associated with proliferation, migration, and invasion of ESCC cells, in addition to expression patterns of EMT markers (Snail, E-cadherin, and vimentin) and pSTAT3^Tyr705 /STAT3 ratio. Overexpression of STAT3 significantly attenuated the effects of PKM2 knockdown on cell proliferation and motility as well as expression of pSTAT3 ^Tyr705 and EMT markers. Consistently, stable short hairpin RNA (shRNA)-mediated silencing of PKM2 reversed the effects of TGF-β1 treatment, specifically, upregulation of PKM2, phosphorylation of STAT3 at Tyr705, and increased EMT, migration, and invasion. We propose that PKM2 regulates cell proliferation, migration, and invasion via phosphorylation of STAT3 through TGF-β1-induced EMT. Our findings collectively provide mechanistic insights into the tumor-promoting role of PKM2, supporting its prognostic value and the therapeutic utility of PKM2 inhibitors as potential antitumor agents in ESCC.

Silencing of carbonic anhydrase I enhances the malignant potential of exosomes secreted by prostatic tumour cells

We report results showing that the silencing of carbonic anhydrase I (siCA1) in prostatic (PC3) tumour cells has a significant impact on exosome formation. An increased diameter, concentration and diversity of the produced exosomes were noticed as a consequence of this knock‐down. The protein composition of the exosomes' cargo was also altered. Liquid chromatography and mass spectrometry analyses identified 42 proteins significantly altered in PC3 siCA1 exosomes compared with controls. The affected proteins are mainly involved in metabolic processes, biogenesis, cell component organization and defense/immunity. Interestingly, almost all of them have been described as ‘enhancers' of tumour development through the promotion of cell proliferation, migration and invasion. Thus, our results indicate that the reduced expression of the CA1 protein enhances the malignant potential of PC3 cells.

Lactate modulates CD4+ T-cell polarization and induces an immunosuppressive environment, which sustains prostate carcinoma progression via TLR8/miR21 axis

Leukocyte infiltration plays an active role in controlling tumor development. In the early stages of carcinogenesis, T cells counteract tumor growth. However, in advanced stages, cancer cells and infiltrating stromal components interfere with the immune control and instruct immune cells to support, rather than counteract, tumor malignancy, via cell-cell contact or soluble mediators. In particular, metabolites are emerging as active players in driving immunosuppression. Here we demonstrate that in a prostate cancer model lactate released by glycolytic cancer-associated fibroblasts (CAFs) acts on CD4⁺ T cells, shaping T-cell polarization. In particular, CAFs exposure (i) reduces the percentage of the antitumoral Th1 subset, inducing a lactate-dependent, SIRT1-mediated deacetylation/degradation of T-bet transcription factor; (ii) increases T_reg cells, driving naive T cells polarization, through a lactate-based NF-kB activation and FoxP3 expression. In turn, this metabolic-based CAF-immunomodulated environment exerts a pro-invasive effect on prostate cancer cells, by activating a previously unexplored miR21/TLR8 axis that sustains cancer malignancy.

Prostate Cancer Energetics and Biosynthesis

Cancers must alter their metabolism to satisfy the increased demand for energy and to produce building blocks that are required to create a rapidly growing tumor. Further, for cancer cells to thrive, they must also adapt to an often changing tumor microenvironment, which can present new metabolic challenges (ex. hypoxia) that are unfavorable for most other cells. As such, altered metabolism is now considered an emerging hallmark of cancer. Like many other malignancies, the metabolism of prostate cancer is considerably different compared to matched benign tissue. However, prostate cancers exhibit distinct metabolic characteristics that set them apart from many other tumor types. In this chapter, we will describe the known alterations in prostate cancer metabolism that occur during initial tumorigenesis and throughout disease progression. In addition, we will highlight upstream regulators that control these metabolic changes. Finally, we will discuss how this new knowledge is being leveraged to improve patient care through the development of novel biomarkers and metabolically targeted therapies.

KDM8/JMJD5 as a dual coactivator of AR and PKM2 integrates AR/EZH2 network and tumor metabolism in CRPC

During the evolution into castration or therapy resistance, prostate cancer cells reprogram the androgen responses to cope with the diminishing level of androgens, and undergo metabolic adaption to the nutritionally deprived and hypoxia conditions. AR (androgen receptor) and PKM2 (pyruvate kinase M2) have key roles in these processes. We report in this study, KDM8/JMJD5, a histone lysine demethylase/dioxygnase, exhibits a novel property as a dual coactivator of AR and PKM2 and as such, it is a potent inducer of castration and therapy resistance. Previously, we showed that KDM8 is involved in the regulation of cell cycle and tumor metabolism in breast cancer cells. Its role in prostate cancer has not been explored. Here, we show that KDM8's oncogenic properties in prostate cancer come from its direct interaction (1) with AR to affect androgen response and (2) with PKM2 to regulate tumor metabolism. The interaction with AR leads to the elevated expression of androgen response genes in androgen-deprived conditions. They include ANCCA/ATAD2 and EZH2, which are directly targeted by KDM8 and involved in sustaining the survival of the cells under hormone-deprived conditions. Notably, in enzalutamide-resistant cells, the expressions of both KDM8 and EZH2 are further elevated, so are neuroendocrine markers. Consequently, EZH2 inhibitors or KDM8 knockdown both resensitize the cells toward enzalutamide. In the cytosol, KDM8 associates with PKM2, the gatekeeper of pyruvate flux and translocates PKM2 into the nucleus, where the KDM8/PKM2 complex serves as a coactivator of HIF-1α to upregulate glycolytic genes. Using shRNA knockdown, we validate KDM8's functions as a regulator for both androgen-responsive and metabolic genes. KDM8 thus presents itself as an ideal therapeutic target for metabolic adaptation and castration-resistance of prostate cancer cells.

PKM2 and HIF-1α regulation in prostate cancer cell lines

Prostate cancer (PCA) is one of the most common cancer types in men, with cancer progression being linked to hypoxia and the induction of hypoxia-inducible factor (HIF).We investigated the expression of pyruvate kinase M2 (PKM2), its regulation by HIF isoforms 1α and 2α, and its role in HIF stabilization. We additionally examined cell survival in the prostate cancer cell lines PC3 and LNCaP under severe hypoxic (0.1% O2) and normoxic (20% O2) conditions. qRT-PCR showed higher up-regulation of PKM2 mRNA expression in LNCaP cells than in PC3 cells, while western blotting showed that PKM2 protein levels were up-regulated only in LNCaP cells. Inhibition of HIF-1α and HIF-2α by small interfering RNA (si-RNA) demonstrated HIF-1α dependent up-regulation of PKM2 at the mRNA and protein levels in LNCaP cells. PKM2 inhibition by si-RNA significantly decreased hypoxia-response element (HRE) activation in a gene reporter assay and down-regulated HIF-1α target vascular endothelial growth factor (VEGF) mRNA expression in PC3 cells, whereas HIF-1α protein levels were not significantly reduced. Additionally, PKM2 inhibition significantly reduced clonogenic survival in both cell lines in a colony formation assay. Prolyl hydroxylase 3 (PHD3) mRNA expression was up-regulated in both cell lines. It has been shown that PKM2 expression is regulated by HIF-1α and that PKM2 favors HIF-1α transactivation under mild (1% O2) but not severe (0.1% O2) hypoxic conditions, and some of our findings are consistent with these previous results. However, this mechanism was not fully observed in our studied cell lines, as PKM2 regulation and HIF-1α stabilization at the transactivation level occurred under severe hypoxic conditions. This discrepancy suggests that tumor tissue origin and cell type influence this model. Our findings expand the current knowledge of the mechanisms of PCA regulation, and would be important in developing novel therapeutic strategies.

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.

LY294002 inhibits the Warburg effect in gastric cancer cells by downregulating pyruvate kinase M2

The ‘Warburg effect’ is considered a vital hallmark of cancer cells, characterized by an altered metabolism, in which cells rely on aerobic glycolysis. As a key enzyme of aerobic glycolysis, pyruvate kinase M2 (PKM2) serves a crucial role in tumorigenesis. Accumulating studies have indicated that PKM2 is a potential target for cancer therapy. The aim of the present study was to assess the anticancer effects of LY294002, a specific phosphatidylinositol-3-kinase inhibitor, on gastric cancer (GC) cells and further explore its possible mechanism in vitro. The present study revealed that LY294002 inhibited GC cell proliferation, induced early apoptosis and significantly decreased lactate dehydrogenase activity and lactate production, in part through inhibiting PKM2 expression. In summary, LY294002 exhibits anticancer effects on GC, partly via the downregulation of PKM2.

Effects of shRNA-Mediated Silencing of PKM2 Gene on Aerobic Glycolysis, Cell Migration, Cell Invasion, and Apoptosis in Colorectal Cancer Cells

This study aims to explore the effects of shRNA-mediated silencing on Pyruvate kinase type M2 (PKM2) gene during aerobic glycolysis in colorectal cancer (CRC) cells. CRC tissues and adjacent normal tissues were obtained from 136 patients diagnosed with qRT-PCR, Western blotting, and immunohistochemistry (IHC) were performed to detect mRNA and protein expressions of PKM2. CRC cells were divided into a blank, vector, and PKM2-shRNA groups. Hexokinase (HK) and PKM2 activity were both determined by glucose-6-phosphate dehydrogenase (G-6-PD) coupled colorimetric assay and enzyme coupling rate method. The extracellular lactate concentration was measured by ultraviolet spectrophotometer and caspase activity was measured using spectrophotometry. The proliferation, cell cycle, apoptosis, invasion, and migration of CRC cells were detected by cell counting kit-8 (CCK-8) assay, flow cytometry, transwell assay, and scratch test. Three groups of nude mice were injected with 0.2 mL single-cell suspension from the blank, vector, and PKM2-shRNA groups, respectively. PKM2 protein content in CRC tissues was higher than that in adjacent normal tissues. Results showed that the PKM2-shRNA group exhibited significantly lower mRNA and protein expressions of PKM2, decreased PKM2 activity, reduced lactate metabolism level, increased cell apoptosis rate, elevated caspase-3 and caspase-9 activity, weakened proliferation, and a reduction in cell invasion and migration ability compared to the vector and blank groups. The optical density (OD) value was lower in the PKM2-shRNA group than in the blank and vector groups. These findings indicate that shRNA-mediated silencing of PKM2 gene promotes apoptosis and inhibits aerobic glycolysis, proliferation, migration, and invasion in CRC cells. J. Cell. Biochem. 118: 4792-4803, 2017. © 2017 Wiley Periodicals, Inc.

Glyoxalase 2 Is Involved in Human Prostate Cancer Progression as Part of a Mechanism Driven By PTEN/PI3K/AKT/mTOR Signaling With Involvement of PKM2 and ERα

BACKGROUND

Glyoxalase 2 (Glo2), together with glyoxalase 1 (Glo1), forms the main scavenging system of methylglyoxal, a potent pro-apoptotic agent mainly generated by glycolysis. An increased rate of glycolysis is a well known signature of cancer cells. As a survival strategy, Glo1 is overexpressed in many human malignant cells, including prostate cancer (PCa), where it plays a crucial role in progression. No information is available on the role of Glo2 in the same ambit. PCa is the most common malignancy affecting men in the western world. Progression to a lethal hormone-refractory PCa represents the major concern in this pathology. Therefore, a deeper understanding of the molecular mechanisms underlying PCa invasiveness and metastasis is urgently needed in order to develop novel therapeutic targets for this incurable state of the malignancy.

METHODS

Glo2 and Glo1 expression was examined in clinical samples of PCa by immunohistochemistry and in different PCa cell models by western blotting and quantitative real-time polymerase chain reaction. Gene silencing/overexpression and scavenging/inhibitory agents were used for functional analyses.

RESULTS

We demonstrated that Glo2, together with Glo1, represents a novel mechanism in PCa progression as part of a pathway driven by PTEN/PI3K/AKT/mTOR signaling with involvement of PKM2 and ERα. Importantly, Glo1/Glo2 silencing did not alter the behavior of benign cells.

CONCLUSIONS

Targeting glyoxalases metabolic pathway may represent a strategy to selectively inhibit advanced PCa. Prostate 77:196-210, 2017. © 2016 Wiley Periodicals, Inc.

Overexpression of PKM2 promotes mitochondrial fusion through attenuated p53 stability

M2-type pyruvate kinase (PKM2) contributes to the Warburg effect. However, it remains unknown as to whether PKM2 has an inhibitory effect on mitochondrial function. We report in this work that PKM2 overexpression inhibits the expression of Drp1 and results in the mitochondrial fusion. The ATP production was found to be decreased, the mtDNA copy number elevated and the expression level of electron transport chain (ETC) complex I, III, V depressed in PKM2 overexpressed cells. PKM2 overexpression showed a decreased p53 protein level and a shorter p53 half-life. In contrast, PKM2 knockdown resulted in increased p53 expression and prolonged half-life of p53. PKM2 could directly bind with both p53 and MDM2 and promote MDM2-mediated p53 ubiquitination. The dimeric PKM2 significantly suppressed p53 expression compared with the other PKM2 mutants. The reverse relationship between PKM2 and Drp1 was further confirmed in a large number of clinical samples. Taken together, the present results highlight a new mechanism that link PKM2 to mitochondrial function, based on p53-Drp1 axis down regulation, revealing a novel therapeutic target in patients with abnormal mitochondria.

Oxidative stress in prostate hyperplasia and carcinogenesis

Prostatic hyperplasia (PH) is a common urologic disease that affects mostly elderly men. PH can be classified as benign prostatic hyperplasia (BPH), or prostate cancer (PCa) based on its severity. Oxidative stress (OS) is known to influence the activities of inflammatory mediators and other cellular processes involved in the initiation, promotion and progression of human neoplasms including prostate cancer. Scientific evidence also suggests that micronutrient supplementation may restore the antioxidant status and hence improve the clinical outcomes for patients with BPH and PCa. This review highlights the recent studies on prostate hyperplasia and carcinogenesis, and examines the role of OS on the molecular pathology of prostate cancer progression and treatment.

Pyruvate kinase M2 overexpression and poor prognosis in solid tumors of digestive system: evidence from 16 cohort studies

Purpose

The expression of pyruvate kinase M2 (PKM2) has been linked to tumor formation and invasion. Specifically, the relationship between high PKM2 expression and prognosis has been evaluated in solid tumors of digestive system. However, the prognostic value of PKM2 remains controversial.

Methods

A literature search of PubMed, Embase, and Cochrane databases was conducted until October 2015. The end point focused on overall survival (OS). The pooled hazard ratio (HR) or odds ratio and the 95% confidence intervals were calculated to correlate PKM2 overexpression with OS and clinicopathological characteristics by employing fixed- or random-effects models, depending on the heterogeneity of the included studies.

Results

We identified 18 cohorts in 16 studies involving 2,812 patients for this meta-analysis. Overall, the combined HR for OS in all tumor types was 1.74 (1.44–2.11; P<0.001). When stratified by tumor type, the influence of PKM2 expression on poor prognosis was also found in gastric cancer (HR =1.54 [1.08–2.21], P=0.018), esophageal squamous cell carcinoma (HR =1.71 [1.38–2.12], P<0.001), hepatocellular cancer (HR =1.92 [1.52–2.42], P<0.001), biliary cancer (HR =2.11 [1.50–2.95], P<0.001), and oral cancer (HR =3.49 [1.97–6.18], P<0.001), but not in pancreatic ductal adenocarcinoma (HR =1.03 [0.28–3.76], P=0.968). Furthermore, PKM2 overexpression had a negative effect on the late clinical stage of all tumor types except for pancreatic ductal adenocarcinoma. The high density of PKM2 overexpression was significantly associated with some clinical characteristics in different cancer types, such as tumor stage, modal metastasis, and tumor size.

Conclusion

Our findings revealed significant association of PKM2 overexpression with OS and certain clinicopathological features in solid tumors of digestive system, thereby suggesting that PKM2 might be an indicator of poor prognosis in digestive system cancers.

PKM2 and cancer: The function of PKM2 beyond glycolysis

Metabolic reprogramming is a hallmark of cancer cells and is used by cancer cells for growth and survival. Pyruvate kinase muscle isozyme M2 (PKM2) is a limiting glycolytic enzyme that catalyzes the final step in glycolysis, which is key in tumor metabolism and growth. The present review discusses the expression and regulation of PKM2, and reports the dominant role that PKM2 plays in glycolysis to achieve the nutrient demands of cancer cell proliferation. In addition, the present study discusses the non-metabolic function of PKM2, and its role as a coactivator and protein kinase, which contributes to tumorigenesis. Furthermore, conflicting studies concerning the role of PKM2 as a therapeutic target are reviewed. The improved understanding of PKM2 may provide a noval approach for cancer treatment.

Targeting stromal-induced pyruvate kinase M2 nuclear translocation impairs oxphos and prostate cancer metastatic spread

Cancer associated fibroblasts (CAFs) are key determinants of cancer progression. In prostate carcinoma (PCa), CAFs induce epithelial-mesenchymal transition (EMT) and metabolic reprogramming of PCa cells towards oxidative phosphorylation (OXPHOS), promoting tumor growth and metastatic dissemination. We herein establish a novel role for pyruvate kinase M2 (PKM2), an established effector of Warburg-like glycolytic behavior, in OXPHOS metabolism induced by CAFs. Indeed, CAFs promote PKM2 post-translational modifications, such as cysteine oxidation and Src-dependent tyrosine phosphorylation, allowing nuclear migration of PKM2 and the formation of a trimeric complex with hypoxia inducible factor-1α (HIF-1α) and the transcriptional repressor Differentially Expressed in Chondrocytes-1 (DEC1). DEC1 recruitment is mandatory for downregulating miR205 expression, thereby fostering EMT execution and metabolic switch toward OXPHOS. Furthermore, the analysis of a cohort of PCa patients reveals a significant positive correlation between PKM2 nuclear localization and cancer aggressiveness, thereby validating our in vitro observations. Crucially, in vitro and in vivo pharmacological targeting of PKM2 nuclear translocation using DASA-58, as well as metformin, impairs metastatic dissemination of PCa cells in SCID mice. Our study indicates that impairing the metabolic tumor:stroma interplay by targeting the PKM2/OXPHOS axis, may be a valuable novel therapeutic approach in aggressive prostate carcinoma.

Pyruvate kinase M2 prevents apoptosis via modulating Bim stability and associates with poor outcome in hepatocellular carcinoma

Pyruvate kinase M2 (PKM2) contributes to the Warburg effect, a hallmark of cancer. We showed that PKM2 levels were correlated with overall survival (hazard ration = 1.675, 95% confidence interval: 1.389-2.019, P < 0.001) and disease-free survival (hazard ration = 1.573, 95% confidence interval: 1.214-2.038, P < 0.001) in a cohort of 490 patients with HCC. The correlations were further validated in an independent cohort of 148 HCC patients. Multivariate analyses revealed that PKM2 was an independent indicator of poor outcome in HCC. The knockdown of PKM2 in HCC cells inhibited cell proliferation and induced apoptosis in vitro and in vivo. Bim siRNA markedly abolished the PKM2-depletion-induced apoptosis. PKM2 depletion decreased the degradation of Bim. In clinical samples, PKM2 expression was reversely correlated with Bim expression. Combination of PKM2 and Bim levels had the best prognostic significance. We suggest that PKM2 serves as a promising biomarker for poor prognosis of patients with HCC and its knockdown induces HCC apoptosis by stabilizing Bim.

The multifaceted regulation and functions of PKM2 in tumor progression

Tumor cells undergo metabolic rewiring from oxidative phosphorylation towards aerobic glycolysis to maintain the increased anabolic requirements for cell proliferation. It is widely accepted that specific expression of the M2 type pyruvate kinase (PKM2) in tumor cells contributes to this aerobic glycolysis phenotype. To date, researchers have uncovered myriad forms of functional regulation for PKM2, which confers a growth advantage on the tumor cells to enable them to adapt to various microenvironmental signals. Here the richness of our understanding on the modulations and functions of PKM2 in tumor progression is reviewed, and some new insights into the paradoxical expression and functional differences of PKM2 in distinct cancer types are offered.