Genetic amplification of PPME1 in gastric and lung cancer and its potential as a novel therapeutic target

The luciferase-based in vivo protein-protein interaction assay revealed that CHK1 promotes PP2A and PME-1 interaction

Protein phosphatase 2A (PP2A) is an essential serine/threonine protein phosphatase, and its dysfunction is involved in the onset of cancer and neurodegenerative disorders. PP2A functions as a trimeric holoenzyme whose composition is regulated by the methyl-esterification (methylation) of the PP2A catalytic subunit (PP2Ac). Protein phosphatase methylesterase-1 (PME-1) is the sole PP2Ac methylesterase, and the higher PME-1 expression is observed in various cancer and neurodegenerative diseases. Apart from serving as a methylesterase, PME-1 acts as a PP2A inhibitory protein, binding directly to PP2Ac and suppressing its activity. The intricate function of PME-1 hinders drug development by targeting the PME-1/PP2Ac axis. This study applied the NanoBiT system, a bioluminescence-based protein interaction assay, to elucidate the molecular mechanism that modulates unknown PME-1/PP2Ac protein-protein interaction (PPI). Compound screening identified that the CHK1 inhibitors inhibited PME-1/PP2Ac association without affecting PP2Ac methylation levels. CHK1 directly phosphorylates PP2Ac to promote PME-1 association. Phospho-mass spectrometry identified multiple phospho-sites on PP2Ac, including the Thr219, that affect PME-1 interaction. An anti-phospho-Thr219 PP2Ac antibody was generated and showed that CHK1 regulates the phosphorylation levels of this site in cells. On the contrary, in vitro phosphatase assay showed that CHK1 is the substrate of PP2A, and PME-1 hindered PP2A-mediated dephosphorylation of CHK1. Our data provides novel insights into the molecular mechanisms governing the PME-1/PP2Ac PPI and the triad relationship between PP2A, PME-1, and CHK1.

Circular RNAs-mediated angiogenesis in human cancers

Circular RNAs (circRNAs) as small non-coding RNAs with cell, tissue, or organ-specific expression accomplish a broad array of functions in physiological and pathological processes such as cancer development. Angiogenesis, a complicated multistep process driving a formation of new blood vessels, speeds up tumor progression by supplying nutrients as well as energy. Abnormal expression of circRNAs reported to affect tumor development through impressing angiogenesis. Such impacts are introduced as constant with different tumorigenic features known as "hallmarks of cancer". In addition, deregulated circRNAs show possibilities to prognosis and diagnosis both in the prophecy of prognosis in malignancies and also their prejudice from healthy individuals. In the present review article, we have evaluated the angiogenic impacts and anti-angiogenic managements of circRNAs in human cancers.

Protein Phosphatase 2A as a Therapeutic Target in Pulmonary Diseases

New disease targets and medicinal chemistry approaches are urgently needed to develop novel therapeutic strategies for treating pulmonary diseases. Emerging evidence suggests that reduced activity of protein phosphatase 2A (PP2A), a complex heterotrimeric enzyme that regulates dephosphorylation of serine and threonine residues from many proteins, is observed in multiple pulmonary diseases, including lung cancer, smoke-induced chronic obstructive pulmonary disease, alpha-1 antitrypsin deficiency, asthma, and idiopathic pulmonary fibrosis. Loss of PP2A responses is linked to many mechanisms associated with disease progressions, such as senescence, proliferation, inflammation, corticosteroid resistance, enhanced protease responses, and mRNA stability. Therefore, chemical restoration of PP2A may represent a novel treatment for these diseases. This review outlines the potential impact of reduced PP2A activity in pulmonary diseases, endogenous and exogenous inhibitors of PP2A, details the possible PP2A-dependent mechanisms observed in these conditions, and outlines potential therapeutic strategies for treatment. Substantial medicinal chemistry efforts are underway to develop therapeutics targeting PP2A activity. The development of specific activators of PP2A that selectively target PP2A holoenzymes could improve our understanding of the function of PP2A in pulmonary diseases. This may lead to the development of therapeutics for restoring normal PP2A responses within the lung.

PME-1 sensitizes glioblastoma cells to oxidative stress-induced cell death by attenuating PP2A-B55α-mediated inactivation of MAPKAPK2-RIPK1 signaling

Glioblastoma (GBM) is the most common primary brain tumor in adults. Current standard therapy is surgery followed by radiotherapy, with concurrent and adjuvant temozolomide chemotherapy. GBM is characterized by almost uniformly fatal outcomes, highlighting the unmet clinical need for more efficient, biomarker-guided treatments. Protein phosphatase methylesterase-1 (PME-1), a regulator of the tumor suppressive phosphatase PP2A, promotes PP2A demethylation and inactivation, and is overexpressed in 44% of GBM, associated with increased tumor grade and cellular proliferation. Here, we aimed to investigate how reactive oxygen species (ROS), a frequent by-product of radiotherapy and temozolomide chemotherapy, regulate PP2A function via its methylesterase PME-1, and how PME-1 overexpression impacts the response of GBM cells to oxidative stress. We found that in two glioblastoma cell lines, U87MG and U251MG, expression of PME-1 is positively correlated with the sensitivity of the cells to H₂O₂ or t-BHP-induced oxidative stress. Experiments using the irreversible pharmacologic PME-1 inhibitor, AMZ30, and different PME-1 mutants, revealed that the methylesterase function, the PP2A binding capacity, and the nuclear localization of PME-1 are all important for the sensitizing effect of PME-1 expression. Furthermore, we identified increased nuclear localization of the PP2A-B55α subunit, increased binding of PP2A-B55α to PME-1, and increased B55α-bound PP2A-C demethylation upon oxidative stress. Lastly, we uncovered increased stress-induced phosphorylation and activity of MAPKAPK2 and RIPK1 in PME-1 overexpressing U87MG cells, which caused the observed sensitization to t-BHP treatment. Our data reveal a novel role for PME-1 in oxidative stress-induced GBM cell death, regulating nuclear PP2A-B55α activity and MAPKAPK2-RIPK1 signaling. Patients with GBM tumors overexpressing PME-1, although having a worse prognosis due to increased cellular proliferation of the tumor, could actually be more responsive to oxidative stress-inducing therapies.

Circular MTHFD2L RNA-encoded CM-248aa inhibits gastric cancer progression by targeting the SET-PP2A interaction

The available targeted therapies for gastric cancer (GC) are still limited, so it is important to discover novel molecules as potential treatment options. Proteins or peptides encoded by circular RNAs (circRNAs) are increasingly reported to play essential roles in malignancies. The aim of the present study was to identify an undiscovered protein encoded by circRNA and explore its key role and molecular mechanism in GC progression. CircMTHFD2L (hsa_circ_0069982) was screened and validated as a downregulated circRNA with coding potential. The protein encoded by circMTHFD2L, named CM-248aa, was identified for the first time by immunoprecipitation and mass spectrometry. CM-248aa was significantly downregulated in GC, while its low expression was associated with advanced tumor-node-metastasis (TNM) stage and histopathological grade. Low expression of CM-248aa could be an independent risk factor for poor prognosis. Functionally, CM-248aa, instead of circMTHFD2L suppressed the proliferation and metastasis of GC in vitro and in vivo. Mechanistically, CM-248aa competitively targeted the acidic domain of SET nuclear oncogene (SET) and acted as an endogenous inhibitor of the SET-protein phosphatase 2A interaction to promote dephosphorylation of AKT, extracellular signal-regulated kinase, and P65. Our discovery revealed that CM-248aa could be a potential prognostic biomarker and endogenous therapeutic option for GC.

Proteome changes in autosomal recessive primary microcephaly

BACKGROUND/AIM

Autosomal recessive primary microcephaly (MCPH) is a rare and genetically heterogeneous group of disorders characterized by intellectual disability and microcephaly at birth, classically without further organ involvement. MCPH3 is caused by biallelic variants in the cyclin-dependent kinase 5 regulatory subunit-associated protein 2 gene CDK5RAP2. In the corresponding Cdk5rap2 mutant or Hertwig's anemia mouse model, congenital microcephaly as well as defects in the hematopoietic system, germ cells and eyes have been reported. The reduction in brain volume, particularly affecting gray matter, has been attributed mainly to disturbances in the proliferation and survival of early neuronal progenitors. In addition, defects in dendritic development and synaptogenesis exist that affect the excitation-inhibition balance. Here, we studied proteomic changes in cerebral cortices of Cdk5rap2 mutant mice.

MATERIAL AND METHODS

We used large-gel two-dimensional gel (2-DE) electrophoresis to separate cortical proteins. 2-DE gels were visualized by a trained observer on a light box. Spot changes were considered with respect to presence/absence, quantitative variation and altered mobility.

RESULT

We identified a reduction in more than 30 proteins that play a role in processes such as cell cytoskeleton dynamics, cell cycle progression, ciliary functions and apoptosis. These proteome changes in the MCPH3 model can be associated with various functional and morphological alterations of the developing brain.

CONCLUSION

Our results shed light on potential protein candidates for the disease-associated phenotype reported in MCPH3.

Hsa_circ_0050102 regulates the pancreatic cancer development via miR‐218‐5p/PPME1 axis

Background

Pancreatic cancer (PC) is a malignancy worldwide. Circular RNAs (circRNAs) affects the growth of PC, nonetheless the mechanism is blurry. Here, we reconnoitered the parts of hsa_circ_0050102 in PC.

Methods

Hsa_circ_0050102, microRNA‐218‐5p (miR‐218‐5p) and protein phosphatase methylesterase 1 (PPME1) abundances were indicated by quantitative RT‐PCR or Western blot. Moreover, the cell functions were uncovered. Additionally, the relation of miR‐218‐5p and hsa_circ_0050102 or PPME1 was identified by dual‐luciferase reporter assay. Ultimately, the mice teats were utilized to quantity the part of hsa_circ_0050102.

Results

Hsa_circ_0050102 and PPME1 contents were increased, and the miR‐218‐5p was dwindled in PC. Hsa_circ_0050102 lack subdued cell vitality, colony formation, cell migration and invasion, and angiogenesis, but endorsed cell apoptosis in PC cells. Furthermore, miR‐218‐5p was established to block the development of PC cells via PPME1. Hsa_circ_0050102 bound to miR‐218‐5p to adjust the content of PPME1.

Conclusion

Hsa_circ_0050102 expedited the expansion of PC through growing PPME1 abundance by adjusting miR‐218‐5p.

Long non-coding RNA HOTAIR/microRNA-761 sponge regulates PPME1 and further influences cell biological functions in thyroid carcinoma

BACKGROUND

Most well-differentiated thyroid carcinomas display good therapeutic outcomes, but there are still some patients who are not sensitive to the general treatments lose their treatment opportunities. Thus, it is important to understand the molecular mechanisms that cause thyroid carcinoma, so as to find effective diagnostic and therapeutic targets.

AIM OF THE STUDY

To explore the role of homeobox transcript antisense RNA (HOTAIR) in thyroid carcinoma through protein phosphatase methylesterase 1 (PPME1) by sponging microRNA 761 (miR-761).

METHODS

The regulation network amongst HOTAIR, miR-761 and PPME1 was predicted by online sources. RT-PCR was conducted to evaluate the expression of HOTAIR and miR-761 in tumor tissues. Clinical data was collected and analyzed by Chi-square test. Cell apoptosis and proliferation was evaluated using three types of cancer cells (HTh-7, CAL-62, BCPAP) after treated with si-HOTAIR and miR-761inhibitor. The binding site among HOTAIR, miR-761 and PPME1 was verified by dual luciferase reporter assay. PPME1 expression was measured after HOTAIR and miR-761 were suppressed by western blot. Survival time was measured in nude mice using log-rank test.

RESULTS

HOTAIR was expressed to a significantly greater extent than miR-761 in thyroid tumor tissues (P < .001). miR-761 and PPME1 were negatively correlated (coef = -1.91, P < .001). HOTAIR competitively binds to miR-761 and miR-761 directly targets PPME1. HOTAIR was highly correlated with TNM (χ 2 = 5.797, P = .016), tumor size (χ 2 = 7.955, P = .005) and lymphatic metastasis (χ 2 = 6.0, P = .014). HOTAIR promoted cell proliferation and inhibited cell apoptosis, whereas miR-761 did not. HOTAIR elevated and miR-761 suppressed PPME1 expression. HOTAIR expression appears to affect the survival time in vivo.

CONCLUSION

HOTAIR regulated thyroid cancer cells by binding to miR-761 through PPME1.

Disturbances in PP2A methylation and one-carbon metabolism compromise Fyn distribution, neuritogenesis, and APP regulation

The nonreceptor protein tyrosine kinase Fyn and protein Ser/Thr phosphatase 2A (PP2A) are major multifunctional signaling molecules. Deregulation of Fyn and altered PP2A methylation are implicated in cancer and Alzheimer's disease (AD). Here, we tested the hypothesis that the methylation state of PP2A catalytic subunit, which influences PP2A subunit composition and substrate specificity, can affect Fyn regulation and function. Using Neuro-2a (N2a) neuroblastoma cell models, we first show that methylated PP2A holoenzymes containing the Bα subunit coimmunoprecipitate and copurify with Fyn in membrane rafts. PP2A methylation status regulates Fyn distribution and Fyn-dependent neuritogenesis, likely in part by affecting actin dynamics. A methylation-incompetent PP2A mutant fails to interact with Fyn. It perturbs the normal partitioning of Fyn and amyloid precursor protein (APP) in membrane microdomains, which governs Fyn function and APP processing. This correlates with enhanced amyloidogenic cleavage of APP, a hallmark of AD pathogenesis. Conversely, enhanced PP2A methylation promotes the nonamyloidogenic cleavage of APP in a Fyn-dependent manner. Disturbances in one-carbon metabolic pathways that control cellular methylation are associated with AD and cancer. Notably, they induce a parallel loss of membrane-associated methylated PP2A and Fyn enzymes in N2a cells and acute mouse brain slices. One-carbon metabolism also modulates Fyn-dependent process outgrowth in N2a cells. Thus, our findings identify a novel methylation-dependent PP2A/Fyn signaling module. They highlight the underestimated importance of cross talks between essential metabolic pathways and signaling scaffolds that are involved in normal cell homeostasis and currently being targeted for cancer and AD treatment.

Expression Pattern and Prognostic Utility of PME-1 in Patients with Hepatocellular Carcinoma

Purpose

Hepatocellular carcinoma (HCC) remains one of the most common malignancies. While there is lack of markers capable of predicting which patients are at risk of aggressive course of the disease. Although a few protein phosphatase methyl-esterase-1 (PME-1) tumor-promoting mechanisms have been reported, the role of PME-1 in cancer including HCC occurrence and progression remains to be elucidated. The aim of this study was to explore the expression pattern and relationship between PME-1 with the pathological parameters in patients with HCC.

Methods

PME-1 expression was assessed from HCC tissue chips via immunohistochemistry. Chi-square test was used to identify the association between PME-1 staining and clinicopathological variables of HCC patients. Kaplan–Meier analysis and Cox regression analysis were performed to draw survival curves and verify the independent prognostic factors of HCC patients, respectively.

Results

We found that PME-1 expression was significantly higher in HCC tumor tissues compared with non-tumor tissues (P < 0.001). Furthermore, high expression level of PME-1 was significantly associated with differentiation (P = 0.047), tumor number (P = 0.001), intrahepatic or extrahepatic metastasis (P = 0.018), and recurrence (P = 0.001). Kaplan–Meier analysis revealed that high expression level of PME-1 was associated with shorter survival (P < 0.001). Univariate analysis with Log-rank test revealed that PME-1 expression status was significantly correlated with overall survival (P < 0.001). Furthermore, multivariate models with Cox proportional hazards analysis showed that high expression of PME-1 was a statistically independent predictive factor of poor prognosis in HCC patients (hazard ratio, 3.429; 95% confidence interval, 1.369–8.589; P = 0.009).

Conclusion

In conclusion, these findings indicated that PME-1 expression was associated with aggressive pathological features and worse oncological outcomes, suggesting its potential therapeutic value for patients with HCC.

DNAH17-AS1 promotes pancreatic carcinoma by increasing PPME1 expression via inhibition of miR-432-5p

BACKGROUND

The incidence and mortality rates of pancreatic carcinoma (PC) are rapidly increasing worldwide. Long noncoding RNAs (lncRNAs) play critical roles during PC initiation and progression. Since the lncRNA DNAH17-AS1 is highly expressed in PC, the regulation of DNAH17-AS1 in PC was investigated in this study.

AIM

To investigate the expression and molecular action of lncRNA DNAH17-AS1 in PC cells.

METHODS

The PC expression data for the lncRNA DNAH17-AS1 was downloaded from The Cancer Genome Atlas database and used to examine its profile. Western blot and reverse transcription-quantitative PCR were employed to assess protein and mRNA expression. A subcellular fractionation assay was used to determine the location of DNAH17-AS1 in cells. In addition, the regulatory effects of DNAH17-AS1 on miR-432-5p, PPME1, and tumor activity were investigated using luciferase reporter assay, MTT viability analysis, flow cytometry, and transwell migration analysis.

RESULTS

DNAH17-AS1 was upregulated in PC cells and was associated with aggressive tumor behavior and poor prognosis for patients. Silencing DNAH17-AS1 promoted the apoptosis and reduced the viability, invasion, and migration of PC cells. In addition, DNAH17-AS1 served as a PC oncogene by downregulating miR-432-5p which normally directly targeted PPME1 to downregulate its expression.

CONLUSION

DNAH17-AS1 functions in PC as a tumor promoter by regulating the miR-432-5p/PPME1 axis. This finding may provide new insights for PC prognosis and therapy.

Data mining analysis of the PP2A cell cycle axis in mesothelioma patients

Mesothelioma is an aggressive tumor that affects thousands of people every year. The therapeutic options for patients are limited; hence, a better understanding of mesothelioma biology is crucial to improve patient survival. To find new molecular targets and therapeutic strategies related to the protein phosphatase 2A (PP2A) network, we analyzed the gene expression of known PP2A inhibitors in mesothelioma patient samples. Our analysis disclosed a general overexpression of all PP2A-negative regulators in mesothelioma patients. Moreover, the expression of ANP32E and CIP2A genes, increased in 16% and 11% of cases, positively correlates with the ones of all the other PP2A regulators and the ones of the main cyclins and CDKs, suggesting the existence of a feed-forward loop that might contribute to the mesothelioma progression via PP2A inactivation. Overall, our study indicates the existence of a strategic and targetable axis between PP2A inhibitors (ANP32E and CIP2A) and cell cycle regulators (cyclin B2/CDK1) and provides a valuable rationale for using a personalized combinational therapy approach to improve mesothelioma patient survival.

WDR5 inhibition halts metastasis dissemination by repressing the mesenchymal phenotype of breast cancer cells

Background

Development of metastases and drug resistance are still a challenge for a successful systemic treatment in breast cancer (BC) patients. One of the mechanisms that confer metastatic properties to the cell relies in the epithelial-to-mesenchymal transition (EMT). Moreover, both EMT and metastasis are partly modulated through epigenetic mechanisms, by repression or induction of specific related genes.

Methods

We applied shRNAs and drug targeting approaches in BC cell lines and metastatic patient-derived xenograft (PDX) models to inhibit WDR5, the core subunit of histone H3 K4 methyltransferase complexes, and evaluate its role in metastasis regulation.

Result

We report that WDR5 is crucial in regulating tumorigenesis and metastasis spreading during BC progression. In particular, WDR5 loss reduces the metastatic properties of the cells by reverting the mesenchymal phenotype of triple negative- and luminal B-derived cells, thus inducing an epithelial trait. We also suggest that this regulation is mediated by TGFβ1, implying a prominent role of WDR5 in driving EMT through TGFβ1 activation. Moreover, such EMT reversion can be induced by drug targeting of WDR5 as well, leading to BC cell sensitization to chemotherapy and enhancement of paclitaxel-dependent effects.

Conclusions

We suggest that WDR5 inhibition could be a promising pharmacologic approach to reduce cell migration, revert EMT, and block metastasis formation in BC, thus overcoming resistance to standard treatments.

Protein phosphatase 2A (PP2A): a key phosphatase in the progression of chronic obstructive pulmonary disease (COPD) to lung cancer

Lung cancer (LC) has the highest relative risk of development as a comorbidity of chronic obstructive pulmonary disease (COPD). The molecular mechanisms that mediate chronic inflammation and lung function impairment in COPD have been identified in LC. This suggests the two diseases are more linked than once thought. Emerging data in relation to a key phosphatase, protein phosphatase 2A (PP2A), and its regulatory role in inflammatory and tumour suppression in both disease settings suggests that it may be critical in the progression of COPD to LC. In this review, we uncover the importance of the functional and active PP2A holoenzyme in the context of both diseases. We describe PP2A inactivation via direct and indirect means and explore the actions of two key PP2A endogenous inhibitors, cancerous inhibitor of PP2A (CIP2A) and inhibitor 2 of PP2A (SET), and the role they play in COPD and LC. We explain how dysregulation of PP2A in COPD creates a favourable inflammatory micro-environment and promotes the initiation and progression of tumour pathogenesis. Finally, we highlight PP2A as a druggable target in the treatment of COPD and LC and demonstrate the potential of PP2A re-activation as a strategy to halt COPD disease progression to LC. Although further studies are required to elucidate if PP2A activity in COPD is a causal link for LC progression, studies focused on the potential of PP2A reactivating agents to reduce the risk of LC formation in COPD patients will be pivotal in improving clinical outcomes for both COPD and LC patients in the future.

PME-1 is regulated by USP36 in ERK and Akt signaling pathways

Deubiquitinating enzymes (DUBs) play an important role in the ubiquitin-proteasome system (UPS) by eliminating ubiquitins from substrates and inhibiting proteasomal degradation. Protein phosphatase methylesterase 1 (PME-1) inactivates protein phosphatase 2A (PP2A) and enhances the ERK and Akt signaling pathways, which increase cell proliferation and malignant cell transformation. In this study, we demonstrate that USP36 regulates PME-1 through its deubiquitinating enzyme activity. USP36 increases PME-1 stability, and depletion of USP36 decreases the PME-1 expression level. Furthermore, we demonstrate that USP36 promotes the ERK and Akt signaling pathways. In summary, it is suggested that USP36 regulates PME-1 as a DUB and participates in the ERK and Akt signaling pathways.

Therapeutic targeting of PP2A

Protein phosphatase 2A (PP2A) is a major serine/threonine phosphatase that regulates many cellular processes. Given the central role of PP2A in regulating diverse biological functions and its dysregulation in many diseases, including cancer, PP2A directed therapeutics have become of great interest. The main approaches leveraged thus far can be categorized as follows: 1) inhibiting endogenous inhibitors of PP2A, 2) targeted disruption of post translational modifications on PP2A subunits, or 3) direct targeting of PP2A. Additional insight into the structural, molecular, and biological framework driving the efficacy of these therapeutic strategies will provide a foundation for the refinement and development of novel and clinically tractable PP2A targeted therapies.

Regulation of protein phosphatase 2A (PP2A) tumor suppressor function by PME-1

Protein phosphatase 2A (PP2A) plays a major role in maintaining cellular signaling homeostasis by dephosphorylation of a variety of signaling proteins and acts as a tumor suppressor. Protein phosphatase methylesterase-1 (PME-1) negatively regulates PP2A activity by highly complex mechanisms that are reviewed here. Importantly, recent studies have shown that PME-1 promotes oncogenic MAPK/ERK and AKT pathway activities in various cancer types. In human glioma, high PME-1 expression correlates with tumor progression and kinase inhibitor resistance. We discuss the emerging cancer-associated function of PME-1 and its potential clinical relevance.

Protein phosphatase methylesterase-1 (PME-1) expression predicts a favorable clinical outcome in colorectal cancer

Colorectal cancer (CRC) accounts for high mortality. So far, there is lack of markers capable of predicting which patients are at risk of aggressive course of the disease. Protein phosphatase-2A (PP2A) inhibitor proteins have recently gained interest as markers of more aggressive disease in certain cancers. Here, we report the role of PP2A inhibitor PME-1 in CRC. PME-1 expression was assessed from a rectal cancer patient cohort by immunohistochemistry, and correlations were performed for various clinicopathological variables and patient survival. Rectal cancer patients with higher cytoplasmic PME-1 protein expression (above median) had less recurrences (P = 0.003, n = 195) and better disease-free survival (DFS) than the patients with low cytoplasmic PME-1 protein expression (below median). Analysis of PPME-1 mRNA expression from TCGA dataset of colon and rectal adenocarcinoma (COADREAD) patient cohort confirmed high PPME1 expression as an independent protective factor predicting favorable overall survival (OS) (P = 0.005, n = 396) compared to patients with low PPME1 expression. CRC cell lines were used to study the effect of PME-1 knockdown by siRNA on cell survival. Contrary to other cancer types, PME-1 inhibition in CRC cell lines did not reduce the viability of cells or the expression of active phosphorylated AKT and ERK proteins. In conclusion, PME-1 expression predicts for a favorable outcome of CRC patients. The unexpected role of PME-1 in CRC in contrast with the oncogenic role of PP2A inhibitor proteins in other malignancies warrants further studies of cancer-specific function for each of these proteins.

Activity-Based Protein Profiling of Oncogene-Driven Changes in Metabolism Reveals Broad Dysregulation of PAFAH1B2 and 1B3 in Cancer

Targeting dysregulated metabolic pathways is a promising therapeutic strategy for eradicating cancer. Understanding how frequently altered oncogenes regulate metabolic enzyme targets would be useful in identifying both broad-spectrum and targeted metabolic therapies for cancer. Here, we used activity-based protein profiling to identify serine hydrolase activities that were consistently upregulated by various human oncogenes. Through this profiling effort, we found oncogenic regulatory mechanisms for several cancer-relevant serine hydrolases and discovered that platelet activating factor acetylhydrolase 1B2 and 1B3 (PAFAH1B2 and PAFAH1B3) activities were consistently upregulated by several oncogenes, alongside previously discovered cancer-relevant hydrolases fatty acid synthase and monoacylglycerol lipase. While we previously showed that PAFAH1B2 and 1B3 were important in breast cancer, our most recent profiling studies have revealed that these enzymes may be dysregulated broadly across many types of cancers. Here, we find that pharmacological blockade of both enzymes impairs cancer pathogenicity across multiple different types of cancer cells, including breast, ovarian, melanoma, and prostate cancer. We also show that pharmacological blockade of PAFAH1B2 and 1B3 causes unique changes in lipid metabolism, including heightened levels of tumor-suppressing lipids. Our results reveal oncogenic regulatory mechanisms of several cancer-relevant serine hydrolases using activity-based protein profiling, and we show that PAFAH1B2 and 1B3 are important in maintaining cancer pathogenicity across a wide spectrum of cancer types.