A feedback loop between the androgen receptor and 6-phosphogluoconate dehydrogenase (6PGD) drives prostate cancer growth

6-Phosphogluconate dehydrogenase promotes glycolysis and fatty acid synthesis by inhibiting the AMPK pathway in lung adenocarcinoma cells

Abnormal metabolism has emerged as a prominent hallmark of cancer and plays a pivotal role in carcinogenesis and progression of lung adenocarcinoma (LUAD). In this study, single-cell sequencing revealed that the metabolic enzyme 6-phosphogluconate dehydrogenase (PGD), which is a critical regulator of the pentose phosphate pathway (PPP), is significantly upregulated in the malignant epithelial cell subpopulation during malignant progression. However, the precise functional significance of PGD in LUAD and its underlying mechanisms remain elusive. Through the integration of TCGA database analysis and LUAD tissue microarray data, it was found that PGD expression was significantly upregulated in LUAD and closely correlated with a poor prognosis in LUAD patients. Moreover, in vitro and in vivo analyses demonstrated that PGD knockout and inhibition of its activity mitigated the proliferation, migration, and invasion of LUAD cells. Mechanistically, immunoprecipitation-mass spectrometry (IP-MS) revealed for the first time that IQGAP1 is a robust novel interacting protein of PGD. PGD decreased p-AMPK levels by competitively interacting with the IQ domain of the known AMPKα binding partner IQGAP1, which promoted glycolysis and fatty acid synthesis in LUAD cells. Furthermore, we demonstrated that the combination of Physcion (a PGD-specific inhibitor) and metformin (an AMPK agonist) could inhibit tumor growth more effectively both in vivo and in vitro. Collectively, these findings suggest that PGD is a potential prognostic biomarker and therapeutic target for LUAD.

CDK9 inhibition inhibits multiple oncogenic transcriptional and epigenetic pathways in prostate cancer

BACKGROUND

Cyclin-dependent kinase 9 (CDK9) stimulates oncogenic transcriptional pathways in cancer and CDK9 inhibitors have emerged as promising therapeutic candidates.

METHODS

The activity of an orally bioavailable CDK9 inhibitor, CDKI-73, was evaluated in prostate cancer cell lines, a xenograft mouse model, and patient-derived tumor explants and organoids. Expression of CDK9 was evaluated in clinical specimens by mining public datasets and immunohistochemistry. Effects of CDKI-73 on prostate cancer cells were determined by cell-based assays, molecular profiling and transcriptomic/epigenomic approaches.

RESULTS

CDKI-73 inhibited proliferation and enhanced cell death in diverse in vitro and in vivo models of androgen receptor (AR)-driven and AR-independent models. Mechanistically, CDKI-73-mediated inhibition of RNA polymerase II serine 2 phosphorylation resulted in reduced expression of BCL-2 anti-apoptotic factors and transcriptional defects. Transcriptomic and epigenomic approaches revealed that CDKI-73 suppressed signaling pathways regulated by AR, MYC, and BRD4, key drivers of dysregulated transcription in prostate cancer, and reprogrammed cancer-associated super-enhancers. These latter findings prompted the evaluation of CDKI-73 with the BRD4 inhibitor AZD5153, a combination that was synergistic in patient-derived organoids and in vivo.

CONCLUSION

Our work demonstrates that CDK9 inhibition disrupts multiple oncogenic pathways and positions CDKI-73 as a promising therapeutic agent for prostate cancer, particularly aggressive, therapy-resistant subtypes.

ACSM1 and ACSM3 Regulate Fatty Acid Metabolism to Support Prostate Cancer Growth and Constrain Ferroptosis

Solid tumors are highly reliant on lipids for energy, growth, and survival. In prostate cancer, the activity of the androgen receptor (AR) is associated with reprogramming of lipid metabolic processes. Here, we identified acyl-CoA synthetase medium chain family members 1 and 3 (ACSM1 and ACSM3) as AR-regulated mediators of prostate cancer metabolism and growth. ACSM1 and ACSM3 were upregulated in prostate tumors compared with nonmalignant tissues and other cancer types. Both enzymes enhanced proliferation and protected prostate cancer cells from death in vitro, whereas silencing ACSM3 led to reduced tumor growth in an orthotopic xenograft model. ACSM1 and ACSM3 were major regulators of the prostate cancer lipidome and enhanced energy production via fatty acid oxidation. Metabolic dysregulation caused by loss of ACSM1/3 led to mitochondrial oxidative stress, lipid peroxidation, and cell death by ferroptosis. Conversely, elevated ACSM1/3 activity enabled prostate cancer cells to survive toxic levels of medium chain fatty acids and promoted resistance to ferroptosis-inducing drugs and AR antagonists. Collectively, this study reveals a tumor-promoting function of medium chain acyl-CoA synthetases and positions ACSM1 and ACSM3 as key players in prostate cancer progression and therapy resistance. Significance: Androgen receptor-induced ACSM1 and ACSM3 mediate a metabolic pathway in prostate cancer that enables the utilization of medium chain fatty acids for energy production, blocks ferroptosis, and drives resistance to clinically approved antiandrogens.

Metabolic adaptations in prostate cancer

Prostate cancer is one of the most commonly diagnosed cancers in men and is a major cause of cancer-related deaths worldwide. Among the molecular processes that contribute to this disease, the weight of metabolism has been placed under the limelight in recent years. Tumours exhibit metabolic adaptations to comply with their biosynthetic needs. However, metabolites also play an important role in supporting cell survival in challenging environments or remodelling the tumour microenvironment, thus being recognized as a hallmark in cancer. Prostate cancer is uniquely driven by androgen receptor signalling, and this knowledge has also influenced the paths of cancer metabolism research. This review provides a comprehensive perspective on the metabolic adaptations that support prostate cancer progression beyond androgen signalling, with a particular focus on tumour cell intrinsic and extrinsic pathways.

Malate, a natural inhibitor of 6PGD, improves the efficacy of chemotherapy in lung cancer

OBJECTIVE

Metabolic reprogramming is an important coordinator of tumor development and resistance to therapy, such as the tendency of tumor cells to utilize glycolytic energy rather than oxidative phosphorylation, even under conditions of sufficient oxygen. Therefore, targeting metabolic enzymes is an effective strategy to overcome therapeutic resistance.

MATERIALS AND METHODS

We explored the differential expression and growth-promoting function of MDH2 by immunohistochemistry and immunoblotting experiments in lung cancer patients and lung cancer cells. Pentose phosphate pathway-related phenotypes (including ROS levels, NADPH levels, and DNA synthesis) were detected intracellularly, and the interaction of malate and proteinase 6PGD was detected in vitro. In vivo experiments using implanted xenograft mouse models to explore the growth inhibitory effect and pro-chemotherapeutic function of dimethyl malate (DMM) on lung cancer.

RESULTS

We found that the expression of malate dehydrogenase (MDH2) in the tricarboxylic acid cycle (TCA cycle) was increased in lung cancer. Biological function enrichment analysis revealed that MDH2 not only promoted oxidative phosphorylation, but also promoted the pentose phosphate pathway (PPP pathway). Mechanistically, it was found that malate, the substrate of MDH2, can bind to the PPP pathway metabolic enzyme 6PGD, inhibit its activity, reduce the generation of NADPH, and block DNA synthesis. More importantly, DMM can improve the sensitivity of lung cancer to the clinical drug cisplatin.

CONCLUSION

We have identified malate as a natural inhibitor of 6PGD, which will provide new leads for the development of 6PGD inhibitors. In addition, the metabolic enzyme MDH2 and the metabolite malate may provide a backup option for cells to inhibit their own carcinogenesis, as the accumulated malate targets 6PGD to block the PPP pathway and inhibit cell cycle progression.

Fatty acid elongation regulates mitochondrial β-oxidation and cell viability in prostate cancer by controlling malonyl-CoA levels

Recently, the fatty acid elongation enzyme ELOVL5 was identified as a critical pro-metastatic factor in prostate cancer, required for cell growth and mitochondrial homeostasis. The fatty acid elongation reaction catalyzed by ELOVL5 utilizes malonyl-CoA as the carbon donor. Here, we demonstrate that ELOVL5 knockdown causes malonyl-CoA accumulation. Malonyl-CoA is a cellular substrate that can inhibit fatty acid β-oxidation in the mitochondria through allosteric inhibition of carnitine palmitoyltransferase 1A (CPT1A), the enzyme that controls the rate-limiting step of the long chain fatty acid β-oxidation cycle. We hypothesized that changes in malonyl-CoA abundance following ELOVL5 knockdown could influence mitochondrial β-oxidation rates in prostate cancer cells, and regulate cell viability. Accordingly, we find that ELOVL5 knockdown is associated with decreased mitochondrial β-oxidation in prostate cancer cells. Combining ELOVL5 knockdown with FASN inhibition to increase malonyl-CoA abundance endogenously enhances the effect of ELOVL5 knockdown on prostate cancer cell viability, while preventing malonyl-CoA production rescues the cells from the effect of ELOVL5 knockdown. Our findings indicate an additional role for fatty acid elongation, in the control of malonyl-CoA homeostasis, alongside its established role in the production of long-chain fatty acid species, to explain the importance of fatty acid elongation for cell viability.

Targeting hyaluronan-mediated motility receptor (HMMR) enhances response to androgen receptor signalling inhibitors in prostate cancer

BACKGROUND

Resistance to androgen receptor signalling inhibitors (ARSIs) represents a major clinical challenge in prostate cancer. We previously demonstrated that the ARSI enzalutamide inhibits only a subset of all AR-regulated genes, and hypothesise that the unaffected gene networks represent potential targets for therapeutic intervention. This study identified the hyaluronan-mediated motility receptor (HMMR) as a survival factor in prostate cancer and investigated its potential as a co-target for overcoming resistance to ARSIs.

METHODS

RNA-seq, RT-qPCR and Western Blot were used to evaluate the regulation of HMMR by AR and ARSIs. HMMR inhibition was achieved via siRNA knockdown or pharmacological inhibition using 4-methylumbelliferone (4-MU) in prostate cancer cell lines, a mouse xenograft model and patient-derived explants (PDEs).

RESULTS

HMMR was an AR-regulated factor that was unaffected by ARSIs. Genetic (siRNA) or pharmacological (4-MU) inhibition of HMMR significantly suppressed growth and induced apoptosis in hormone-sensitive and enzalutamide-resistant models of prostate cancer. Mechanistically, 4-MU inhibited AR nuclear translocation, AR protein expression and subsequent downstream AR signalling. 4-MU enhanced the growth-suppressive effects of 3 different ARSIs in vitro and, in combination with enzalutamide, restricted proliferation of prostate cancer cells in vivo and in PDEs.

CONCLUSION

Co-targeting HMMR and AR represents an effective strategy for improving response to ARSIs.

Critical role of antioxidant programs in enzalutamide-resistant prostate cancer

Therapy resistance to second-generation androgen receptor (AR) antagonists, such as enzalutamide, is common in patients with advanced prostate cancer (PCa). To understand the metabolic alterations involved in enzalutamide resistance, we performed metabolomic, transcriptomic, and cistromic analyses of enzalutamide-sensitive and -resistant PCa cells, xenografts, patient-derived organoids, patient-derived explants, and tumors. We noted dramatically higher basal and inducible levels of reactive oxygen species (ROS) in enzalutamide-resistant PCa and castration-resistant PCa (CRPC), in comparison to enzalutamide-sensitive PCa cells or primary therapy-naive tumors respectively. Unbiased metabolomic evaluation identified that glutamine metabolism was consistently upregulated in enzalutamide-resistant PCa cells and CRPC tumors. Stable isotope tracing studies suggest that this enhanced glutamine metabolism drives an antioxidant program that allows these cells to tolerate higher basal levels of ROS. Inhibition of glutamine metabolism with either a small-molecule glutaminase inhibitor or genetic knockout of glutaminase enhanced ROS levels, and blocked the growth of enzalutamide-resistant PCa. The critical role of compensatory antioxidant pathways in maintaining enzalutamide-resistant PCa cells was validated by targeting another antioxidant program driver, ferredoxin 1. Taken together, our data identify a metabolic need to maintain antioxidant programs and a potentially targetable metabolic vulnerability in enzalutamide-resistant PCa.

Inhibition of 6-Phosphogluconate Dehydrogenase Reverses Epirubicin Resistance Through Metabolic Reprograming in Triple-Negative Breast Cancer Cells

At present, chemotherapy is the most effective strategy for treating triple-negative breast cancer (TNBC), but its efficacy was limited by the development of chemo-resistance. The exact mechanism of chemoresistance still remains unclear. This study aims to examine whether 6-phosphogluconate dehydrogenase (6PGD), a key enzyme in the oxidative pentose phosphate pathway (PPP), could promote the resistance of TNBC cells to epirubicin. A TNBC epirubicin-resistant cell line was developed by increasing concentration and the effectiveness was tested. The expression and knockdown efficiency of 6PGD were further validated by performing quantitative real-time PCR (qPCR) and Western blot. The effects of 6PGD on parental and drug-resistant TNBC cell lines were verified based on proliferation and apoptosis experiments. Finally, nicotinamide adenine dinucleotide phosphate (NADPH) and lactate quantitative experiments were performed to examine the mechanism of 6PGD in promoting drug resistance. Epirubicin-resistant cancer cells exhibited a higher level of 6PGD in contrast to epirubicin-sensitive cells. In addition, 6PGD inhibited by genetic and pharmacological approaches significantly suppressed the growth and survival of both epirubicin-sensitive and epirubicin-resisteant TNBC cells. It should be noted that 6PGD inhibition sensitized epirubicin-resistant TNBC cells to epirubicin treatment. Moreover, it was also found that the levels of NADPH and lactate increased in epirubicin-resistant TNBC cells but decreased in response to 6PGD inhibition. The present results indicated that 6PGD inhibition disrupted metabolic reprogramming in epirubicin-resistant TNBC cells. Our work demonstrated that 6PGD inhibition reversed the resistance of TNBC cells to epirubicin, providing an alternative therapeutic choice to tackle the challenge of epirubicin resistance in TNBC treatment.

Androgen receptor signaling-mitochondrial DNA-oxidative phosphorylation: A critical triangle in early prostate cancer

Mitochondria are more than just the cellular powerhouse. They also play key roles in vital functions such as apoptosis, metabolism regulation, and other intracellular interactions. The mitochondrial DNA (mtDNA) encodes for 12 subunits of the oxidative phosphorylation (OXPHOS) system. Depletion of mtDNA in androgen-dependent prostate cancer (PCa) cell lines renders them androgen-independent and more aggressive. Paradoxically, pharmaceutical inhibition of OXPHOS is lethal for subsets of PCa cells, whereas others become dependent on androgen receptor (AR) signaling for survival. Given that the AR-mitochondria interaction is critical for early PCa, it is crucial to understand the details of this interaction. Technical hurdles have made mitochondria traditionally difficult to study, with many techniques used for isolation masking the properties of given individual mitochondria. Although the isolation of mitochondria enables us to study OXPHOS, we miss the context in which mitochondria interact with the rest of the cell. Both AR signaling and mtDNA affect apoptosis, metabolism regulation, cellular calcium storage and homeostasis, intracellular calcium signaling, and redox homeostasis. In this review, we will attempt to understand how the crosstalk between AR-mtDNA-OXPHOS is responsible for "life or death" decisions inside the cells. Our aim is to point toward potential vulnerabilities that can lead to the discovery of novel therapeutic targets.

Quantitative proteomics identified circulating biomarkers in lung adenocarcinoma diagnosis

BACKGROUND

Lung cancer (LC) is a common malignant tumor with a high incidence and poor prognosis. Early LC could be cured, but the 5-year-survival rate for patients advanced is extremely low. Early screening of tumor biomarkers through plasma could allow more LC to be detected at an early stage, leading to a earlier treatment and a better prognosis.

METHODS

This study was based on total proteomic analysis and parallel reaction monitoring validation of peripheral blood from 20 lung adenocarcinoma patients and 20 healthy individuals. Furthermore, differentially expressed proteins closely related to prognosis were analysed using Kaplan-Meier Plotter and receiver operating characteristic curve (ROC) curve analysis.

RESULTS

The candidate proteins GAPDH and RAC1 showed the highest connectivity with other differentially expressed proteins between the lung adenocarcinoma group and the healthy group using STRING. Kaplan-Meier Plotter analysis showed that lung adenocarcinoma patients with positive ATCR2, FHL1, RAB27B, and RAP1B expression had observably longer overall survival than patients with negative expression (P < 0.05). The high expression of ARPC2, PFKP, PNP, RAC1 was observably negatively correlated with prognosis (P < 0.05). 17 out of 27 proteins showed a high area under the curve (> 0.80) between the lung adenocarcinoma and healthy plasma groups. Among those proteins, UQCRC1 had an area under the curve of 0.960, and 5 proteins had an area under the curve from 0.90 to 0.95, suggesting that these hub proteins might have discriminatory potential in lung adenocarcinoma, P < 0.05.

CONCLUSIONS

These findings provide UQCRC1, GAPDH, RAC1, PFKP have potential as novel biomarkers for the early screening of lung adenocarcinoma.

Dual contribution of the mTOR pathway and of the metabolism of amino acids in prostate cancer

BACKGROUND

Prostate cancer is the leading cause of cancer in men, and its incidence increases with age. Among other risk factors, pre-existing metabolic diseases have been recently linked with prostate cancer, and our current knowledge recognizes prostate cancer as a condition with important metabolic anomalies as well. In malignancies, metabolic disorders are commonly associated with aberrations in mTOR, which is the master regulator of protein synthesis and energetic homeostasis. Although there are reports demonstrating the high dependency of prostate cancer cells for lipid derivatives and even for carbohydrates, the understanding regarding amino acids, and the relationship with the mTOR pathway ultimately resulting in metabolic aberrations, is still scarce.

CONCLUSIONS AND PERSPECTIVES

In this review, we briefly provide evidence supporting prostate cancer as a metabolic disease, and discuss what is known about mTOR signaling and prostate cancer. Next, we emphasized on the amino acids glutamine, leucine, serine, glycine, sarcosine, proline and arginine, commonly related to prostate cancer, to explore the alterations in their regulatory pathways and to link them with the associated metabolic reprogramming events seen in prostate cancer. Finally, we display potential therapeutic strategies for targeting mTOR and the referred amino acids, as experimental approaches to selectively attack prostate cancer cells.

The Integration of Metabolomics with Other Omics: Insights into Understanding Prostate Cancer

Our understanding of prostate cancer (PCa) has shifted from solely caused by a few genetic aberrations to a combination of complex biochemical dysregulations with the prostate metabolome at its core. The role of metabolomics in analyzing the pathophysiology of PCa is indispensable. However, to fully elucidate real-time complex dysregulation in prostate cells, an integrated approach based on metabolomics and other omics is warranted. Individually, genomics, transcriptomics, and proteomics are robust, but they are not enough to achieve a holistic view of PCa tumorigenesis. This review is the first of its kind to focus solely on the integration of metabolomics with multi-omic platforms in PCa research, including a detailed emphasis on the metabolomic profile of PCa. The authors intend to provide researchers in the field with a comprehensive knowledge base in PCa metabolomics and offer perspectives on overcoming limitations of the tool to guide future point-of-care applications.

Harnessing the Heterogeneity of Prostate Cancer for Target Discovery Using Patient-Derived Explants

Simple Summary

There is a widespread push toward more biologically relevant pre-clinical models of prostate cancer that can improve the discovery and translation of new drugs and biomarkers for this disease. Patient-derived explant culture is an innovative pre-clinical model that utilizes surgical prostate cancer specimens in a way that retains the architecture, microenvironment and heterogeneity of prostate tumors—factors that critically influence cell behavior and response to therapy. With increasing tissue complexity comes increasing complexity of analysis. The aim of this study was to provide critical information for the successful application and analysis of the patient-derived prostate cancer explant model.

Abstract

Prostate cancer is a complex and heterogeneous disease, but a small number of cell lines have dominated basic prostate cancer research, representing a major obstacle in the field of drug and biomarker discovery. A growing lack of confidence in cell lines has seen a shift toward more sophisticated pre-clinical cancer models that incorporate patient-derived tumors as xenografts or explants, to more accurately reflect clinical disease. Not only do these models retain critical features of the original tumor, and account for the molecular diversity and cellular heterogeneity of prostate cancer, but they provide a unique opportunity to conduct research in matched tumor samples. The challenge that accompanies these complex tissue models is increased complexity of analysis. With over 10 years of experience working with patient-derived explants (PDEs) of prostate cancer, this study provides guidance on the PDE method, its limitations, and considerations for addressing the heterogeneity of prostate cancer PDEs that are based on statistical modeling. Using inhibitors of the molecular chaperone heat shock protein 90 (Hsp90) as an example of a drug that induces robust proliferative response, we demonstrate how multi-omics analysis in prostate cancer PDEs is both feasible and essential for identification of key biological pathways, with significant potential for novel drug target and biomarker discovery.

The Impact of Metabolic Syndrome and Type 2 Diabetes Mellitus on Prostate Cancer

Prostate cancer (PCa) remains the second most common type of cancer in men worldwide in 2020. Despite its low death rate, the need for new therapies or prevention strategies is critical. The prostate carcinogenesis process is complex and multifactorial. PCa is caused by a variety of mutations and carcinogenic events that constitutes the disease's multifactorial focus, capable of not only remodeling cellular activity, but also modeling metabolic pathways to allow adaptation to the nutritional requirements of the tumor, creating a propitious microenvironment. Some risk factors have been linked to the development of PCa, including Metabolic Syndrome (MetS) and Type 2 Diabetes Mellitus (T2DM). MetS is intrinsically related to PCa carcinogenic development, increasing its aggressiveness. On the other hand, T2DM has the opposite impact, although in other carcinomas its effect is similar to the MetS. Although these two metabolic disorders may share some developmental processes, such as obesity, insulin resistance, and dyslipidemia, their influence on PCa prognosis appears to have an inverse effect, which makes this a paradox. Understanding the phenomena behind this paradoxical behavior may lead to new concepts into the comprehension of the diseases, as well as to evaluate new therapeutical targets. Thus, this review aimed to evaluate the impact of metabolic disorders in PCa's aggressiveness state and metabolism.

Personalized Medicine for Prostate Cancer: Is Targeting Metabolism a Reality?

Prostate cancer invokes major shifts in gene transcription and metabolic signaling to mediate alterations in nutrient acquisition and metabolic substrate selection when compared to normal tissues. Exploiting such metabolic reprogramming is proposed to enable the development of targeted therapies for prostate cancer, yet there are several challenges to overcome before this becomes a reality. Herein, we outline the role of several nutrients known to contribute to prostate tumorigenesis, including fatty acids, glucose, lactate and glutamine, and discuss the major factors contributing to variability in prostate cancer metabolism, including cellular heterogeneity, genetic drivers and mutations, as well as complexity in the tumor microenvironment. The review draws from original studies employing immortalized prostate cancer cells, as well as more complex experimental models, including animals and humans, that more accurately reflect the complexity of the in vivo tumor microenvironment. In synthesizing this information, we consider the feasibility and potential limitations of implementing metabolic therapies for prostate cancer management.

Periprostatic Adipose Tissue Microenvironment: Metabolic and Hormonal Pathways During Prostate Cancer Progression

The periprostatic adipose tissue (PPAT) is a site of invasion of prostate cancer (PCa) and is part of the microenvironment. It was shown that PPAT secretes factors and fatty acids (FAs) that alter the microenvironment of the PCa. The PPAT secretome of patients with PCa-T3 stage (PPAT-T3) has a metabolic profile enriched in several pathways related to energy production, indicating a greater energy requirement by the tumor, when compared to that of patients in the PCa-T2 stage (PPAT-T2). PPAT-T3 also shows enrichment in pathways related to hormone response, polyamine synthesis, and control of protein synthesis, through amino acid, RNA, and nucleotide metabolism. PPAT-T2 and PPAT-BPH secretomes have less complex metabolic profile, both related with energy balance, while PPAT-BPH has hormone response through insulin pathway. Undoubtedly, a deeper characterization of the human PPAT will lead to a better understanding of the disease and possibly allow new stratification factors and the design of a specific therapy that targets crucial components of the tumor microenvironment as another way to treat or control the disease.