CIP2A regulates cancer metabolism and CREB phosphorylation in non-small cell lung cancer

Identification of a Novel Protein Phosphatase 2A Activator, PPA24, as a Potential Therapeutic for FOLFOX-Resistant Colorectal Cancer

A series of compounds were designed utilizing molecular modeling and fragment-based design based upon the known protein phosphatase 2A (PP2A) activators, NSC49L and iHAP1, and evaluated for their ability to inhibit the viability of colorectal cancer (CRC) and folinic acid, 5-fluorouracil, and oxaliplatin (FOLFOX)-resistant CRC cells. PPA24 (19a) was identified as the most cytotoxic compound with IC50 values in the range of 2.36-6.75 μM in CRC and FOLFOX-resistant CRC cell lines. It stimulated PP2A activity to a greater extent, displayed lower binding energies through molecular docking, and showed higher binding affinity through surface plasmon resonance for PP2A catalytic subunit α than the known PP2A activators. PPA24 dose-dependently induced apoptosis and oxidative stress, decreased the level of c-Myc expression, and synergistically potentiated cytotoxicity when combined with gemcitabine and cisplatin. Furthermore, a PPA24-encapsulated nanoformulation significantly inhibited the growth of CRC xenografts without systemic toxicities. Together, these results signify the potential of PPA24 as a novel PP2A activator and a prospective therapeutic for CRC and FOLFOX-resistant CRC.

Energy metabolism as the hub of advanced non-small cell lung cancer management: a comprehensive view in the framework of predictive, preventive, and personalized medicine

Energy metabolism is a hub of governing all processes at cellular and organismal levels such as, on one hand, reparable vs. irreparable cell damage, cell fate (proliferation, survival, apoptosis, malignant transformation etc.), and, on the other hand, carcinogenesis, tumor development, progression and metastazing versus anti-cancer protection and cure. The orchestrator is the mitochondria who produce, store and invest energy, conduct intracellular and systemically relevant signals decisive for internal and environmental stress adaptation, and coordinate corresponding processes at cellular and organismal levels. Consequently, the quality of mitochondrial health and homeostasis is a reliable target for health risk assessment at the stage of reversible damage to the health followed by cost-effective personalized protection against health-to-disease transition as well as for targeted protection against the disease progression (secondary care of cancer patients against growing primary tumors and metastatic disease). The energy reprogramming of non-small cell lung cancer (NSCLC) attracts particular attention as clinically relevant and instrumental for the paradigm change from reactive medical services to predictive, preventive and personalized medicine (3PM). This article provides a detailed overview towards mechanisms and biological pathways involving metabolic reprogramming (MR) with respect to inhibiting the synthesis of biomolecules and blocking common NSCLC metabolic pathways as anti-NSCLC therapeutic strategies. For instance, mitophagy recycles macromolecules to yield mitochondrial substrates for energy homeostasis and nucleotide synthesis. Histone modification and DNA methylation can predict the onset of diseases, and plasma C7 analysis is an efficient medical service potentially resulting in an optimized healthcare economy in corresponding areas. The MEMP scoring provides the guidance for immunotherapy, prognostic assessment, and anti-cancer drug development. Metabolite sensing mechanisms of nutrients and their derivatives are potential MR-related therapy in NSCLC. Moreover, miR-495-3p reprogramming of sphingolipid rheostat by targeting Sphk1, 22/FOXM1 axis regulation, and A2 receptor antagonist are highly promising therapy strategies. TFEB as a biomarker in predicting immune checkpoint blockade and redox-related lncRNA prognostic signature (redox-LPS) are considered reliable predictive approaches. Finally, exemplified in this article metabolic phenotyping is instrumental for innovative population screening, health risk assessment, predictive multi-level diagnostics, targeted prevention, and treatment algorithms tailored to personalized patient profiles-all are essential pillars in the paradigm change from reactive medical services to 3PM approach in overall management of lung cancers. This article highlights the 3PM relevant innovation focused on energy metabolism as the hub to advance NSCLC management benefiting vulnerable subpopulations, affected patients, and healthcare at large.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13167-024-00357-5.

Cip2a induces arginine biosynthesis and promotes tumor progression in non-small cell lung cancer

Cancerous inhibitor of protein phosphatase 2A (Cip2a) is an oncoprotein, playing important roles in tumor progression. However, the underlying mechanisms by which Cip2a promotes tumor aggressiveness in NSCLC remain to be further investigated. In this study, we found that Cip2a expression is elevated in NSCLC and correlates with poor prognosis. Knockdown of Cip2a significantly reduced the ability of cell proliferation, invasion, and metastasis of NSCLC both in vitro and in vivo. Furthermore, we found that Cip2a promotes tumor progression partly by inducing arginine biosynthesis, and knockdown of Cip2a exhibited a significantly increased sensitivity to arginine deprivation and mTOR inhibition. In addition, we found that p53 mutants in NSCLC cells increased Cip2a expression by inhibiting the activity of wild-type p53. Our findings provide new insights into the mechanisms of Cip2a in promoting tumor progression and suggest that Cip2a represents a potential therapeutic target for treating NSCLC.

Increased phosphorylated CREB1 protein correlates with poor prognosis in clear cell renal cell carcinoma

Background

This study aims to investigate the level of cAMP response element-binding protein 1 (phospho S133) (p-CREB1) protein in clear cell renal cell carcinoma (ccRCC) and evaluates its prognosis significance.

Methods

Immunohistochemistry (IHC) method was performed to detect p-CREB1 staining in 233 ccRCC patients. Three or more high-power fields per tissue section were equally captured by a Leica DMRXA microphotographic system, and average staining intensity (optical density, OD) was analyzed by Leica Qwin Standard V2.6 system. Univariate and multivariate Cox proportional regression model was performed to assess the correlation of p-CREB1 staining and clinical outcomes.

Results

IHC proved that the level of p-CREB1 protein was significantly higher in tumor tissues than in adjacent normal tissues, and gradually increased from normal to tumor sections. On the basis of the receiver operating characteristic curve, patients were divided into low p-CREB1 staining (OD ≤0.28) and high p-CREB1 staining subgroup (OD >0.28) according to p-CREB1 protein staining intensity of tumor cells. Multivariate analyses showed that high p-CREB1staining was an independent risk factor for cancer-specific free survival, overall survival and progression-free survival.

Conclusions

p-CREB1 protein is an independent prognostic biomarker for ccRCC patients.

Aberrant expression of vasculogenic mimicry, PRRX1, and CIP2A in clear cell renal cell carcinoma and its clinicopathological significance

Vasculogenic mimicry (VM) involves a tubular structure with a basement membrane that is similar to and communicates with vessels but functions independent of blood vessels to nourish tumor cells, promote tumor progression, invasion, and metastasis, with reduced 5-year survival rates. Tumor cell proliferation, invasion, and metastasis are promoted by the epithelial-mesenchymal transition (EMT). Paired-related homeobox 1 (PRRX1), a newly discovered EMT inducer, has been shown to correlate with metastasis and prognosis in diverse cancer types. Cancerous inhibitor of protein phosphatase 2A (CIP2A) was initially recognized as an oncoprotein. In this study, we aimed to investigate the expression and clinical significance of the EMT markers PRRX1, CIP2A and VM in clear cell renal cell carcinoma (CCRCC) and their respective associations with clinicopathological parameters and survival.Expression of PRRX1, CIP2A and VM in whole CCRCC tissues from 110 patients was analyzed by immunohistochemical and histochemical staining. Fisher's exact test or the chi square test was used to assess associations with positive or negative staining of these markers and clinicopathological characteristics.Positive expression of CIP2A and VM presence was significantly higher and that of PRRX1 was significantly lower in CCRCC tissues than in corresponding normal tissues. Furthermore, positive expression of CIP2A and VM was significantly associated with tumor grade, size, lymph node metastasis (LNM) stage, and tumor node metastasis (TNM) stage and inversely associated with overall survival time (OST). Moreover, levels of PRRX1 were negatively associated with tumor grade, size, LNM stage, and TNM stage. The PRRX1 subgroup had a significantly longer OST time than did the PRRX1 subgroup. In multivariate analysis, high VM and CIP2A, tumor grade, LNM stage, TNM stage, and low PRRX1 levels were identified as potential independent prognostic factors for OST in CCRCC patients.VM and expression of CIP2A and PRRX1 represent promising biomarkers for metastasis and prognosis and potential therapeutic targets in CCRCC.

Cancerous inhibitor of protein phosphatase 2A (CIP2A) modifies energy metabolism via 5' AMP-activated protein kinase signalling in malignant cells

Cancerous inhibitor of protein phosphatase 2A (CIP2A) is an adverse biomarker across many malignancies. Using K562 cells engineered to have high or low CIP2A expression, we show that high CIP2A levels significantly bias cellular energy production towards oxidative phosphorylation (OXPHOS) rather than glycolysis. Mass spectrometric analysis of CIP2A interactors and isobaric tagging for relative and absolute protein quantitation (ITRAQ) experiments identified many associated proteins, several of which co-vary with CIP2A level. Many of these CIP2A associating and co-varying proteins are involved in energy metabolism including OXPHOS, or in 5' AMP-activated protein kinase (AMPK) signalling, and manipulating AMPK activity mimics the effects of low/high CIP2A on OXPHOS. These effects are dependent on the availability of nutrients, driven by metabolic changes caused by CIP2A. CIP2A level did not affect starvation-induced AMPK phosphorylation of Unc-51 autophagy activating kinase 1 (ULK-1) at Ser555, but autophagy activity correlated with an increase in AMPK activity, to suggest that some AMPK processes are uncoupled by CIP2A, likely via its inhibition of protein phosphatase 2A (PP2A). The data demonstrate that AMPK mediates this novel CIP2A effect on energy generation in malignant cells.

Regulation of the phosphoprotein phosphatase 2A system and its modulation during oxidative stress: A potential therapeutic target?

Phosphoprotein phosphatases are of growing interest in the pathophysiology of many diseases and are often the neglected partner of protein kinases. One family member, PP2A, accounts for dephosphorylation of ~55-70% of all serine/threonine phosphosites. Interestingly, dysregulation of kinase signalling is a hallmark of many diseases in which an increase in oxidative stress is also noted. With this in mind, we assess the evidence to support oxidative stress-mediated regulation of the PP2A system In this article, we first present an overview of the PP2A system before providing an analysis of the regulation of PP2A by endogenous inhibitors, post translational modification, and miRNA. Next, a detailed critique of data implicating reactive oxygen species, ischaemia, ischaemia-reperfusion, and hypoxia in regulating the PP2A holoenzyme and associated regulators is presented. Finally, the pharmacological targeting of PP2A, its endogenous inhibitors, and enzymes responsible for its post-translational modification are covered. There is extensive evidence that oxidative stress modulates multiple components of the PP2A system, however, most of the data pertains to the catalytic subunit of PP2A. Irrespective of the underlying aetiology, free radical-mediated attenuation of PP2A activity is an emerging theme. However, in many instances, a dichotomy exists, which requires clarification and mechanistic insight. Nevertheless, this raises the possibility that pharmacological activation of PP2A, either through small molecule activators of PP2A or CIP2A/SET antagonists may be beneficial in modulating the cellular response to oxidative stress. A better understanding of which, will have wide ranging implications for cancer, heart disease and inflammatory conditions.

Early diagnosis of colorectal cancer via plasma proteomic analysis of CRC and advanced adenomatous polyp

AIM

This paper aimed to identify new candidate biomarkers in blood for early diagnosis of CRC.

BACKGROUND

Colorectal cancer (CRC) is the third most widespread malignancies increasing globally. The high mortality rate associated with colorectal cancer is due to the delayed diagnosis in an advanced stage while the metastasis has occurred. For better clinical management and subsequently to reduce mortality of CRC, early detection biomarkers are in high demand.

METHODS

A 2D-PAGE separation of proteins was performed followed by tandem mass Spectrometry (MALDI-TOF-TOF) to discover potential plasma protein markers for CRC and AA (advanced adenomas). Furthermore, western blot method was used to confirm a part of the results in colorectal tissue samples.

RESULTS

The significantly altered proteins including HPR, HP, ALB, KRT1, APOA1, FGB, IGJ and C4A were down-regulated in polyp relative to normal, and CRC compare to polyp surprisingly, and inversely, ORM2 was up-regulated with the fold change ≥ 2 and p-value ≤ 0.05. We also surveyed APOA1, FGB, and C4A for further confirmation of their expression changes by western blotting. All three of them showed a decreasing trend from normal toward CRC tissue samples as it mentioned before, but just changes of FGB and C4A were significant.

CONCLUSION

The results demonstrated that plasma proteins can be less invasive markers for the detection of CRC. FGB and C4A can be considered as plasma potential biomarkers to early diagnosis of CRC patients and understanding the underlying procedures in tumorigenesis. Undoubtedly, the additional study must be conducted on large scale cohorts to verify the results.

Oncoprotein CIP2A promotes the disassembly of primary cilia and inhibits glycolytic metabolism

In most mammalian cells, the primary cilium is a microtubule-enriched protrusion of the plasma membrane and acts as a key coordinator of signaling pathways during development and tissue homeostasis. The primary cilium is generated from the basal body, and cancerous inhibitor of protein phosphatase 2A (CIP2A), the overexpression of which stabilizes c-MYC to support the malignant growth of tumor cells, is localized in the centrosome. Here, we show that CIP2A overexpression induces primary cilia disassembly through the activation of Aurora A kinase, and CIP2A depletion increases ciliated cells and cilia length in retinal pigment epithelium (RPE1) cells. CIP2A depletion also shifts metabolism toward the glycolytic pathway by altering the expression of metabolic genes related to glycolysis. However, glycolytic activation in CIP2A-depleted cells does not depend on cilia assembly, even though enhanced cilia assembly alone activates glycolytic metabolism. Collectively, these data suggest that CIP2A promotes primary cilia disassembly and that CIP2A depletion induces metabolic reprogramming independent of primary cilia.

Identification of PP1-Gadd34 substrates involved in the unfolded protein response using K-BIPS, a method for phosphatase substrate identification

Phosphorylation is a key post-translational modification in cell signaling, which is regulated by the equilibrium activities of kinases and phosphatases. The biological significance of many phosphorylation events remains poorly characterized due to the scarcity of tools to discover phosphatases substrates. In prior work, we established kinase-catalyzed biotinylation where kinases accept the γ-modified ATP analog, ATP-biotin, to label phosphoproteins. Here, we developed a novel method to study substrates of phosphatases using kinase-catalyzed biotinylation termed K-BIPS (Kinase-catalyzed Biotinylation to Identify Phosphatase Substrates). In a proof-of-concept experiment, K-BIPS was initially used to explore the substrates of phosphatases inhibited by okadaic acid. Many known phosphatase substrates were observed, confirming K-BIPS as a valid phosphatase substrate identification tool. Then, as a further application, K-BIPS was used to discover the substrates of the PP1-Gadd34 phosphatase complex in the context of unfolded protein response (UPR). In addition to the known substrate eIF2α, K-BIPS revealed several novel substrates, suggesting a more prominent role for the PP1-Gadd34 complex in UPR than previously appreciated. Overall, the two studies establish K-BIPS as a powerful tool to discover the cellular substrates of phosphatases.

Cyclic AMP responsive element-binding protein promotes renal cell carcinoma proliferation probably via the expression of spindle and kinetochore-associated protein 2

Emerging evidence shows that the aberrantly expressed cyclic AMP responsive element-binding protein (CREB) is associated with tumor development and progression in several cancers. Spindle and kinetochore-associated protein 2 (SKA2) is essential for regulating the progress of mitosis. In this study, we evaluate in vitro and in vivo the functional relationship between CREB and SKA2 in renal cell carcinoma (RCC). Suppressing and replenishing CREB levels were used to manipulate SKA2 expression, observing the effects on RCC cell lines. Computational prediction and ChIP assay identified that CREB targeted ska2 by binding its CRE sequence in the human genome. Overexpression of CREB reversed the inhibited cell growth following siSKA2 treatment, and reduced the number of cells holding in mitosis. Decreased expression of CREB suppressed RCC cell growth and xenograft tumor formation, accompanied by reduced expression of SKA2. In RCC tumor samples from patients, mRNA for SKA2 were plotted near those of CREB in each sample, with significantly increased immunohistochemical staining of higher SKA2 and CREB in the higher TNM stages. The study adds evidence that CREB, a tumor oncogene, promotes RCC proliferation. It probably achieves this by increasing SKA2 expression.

CT45A1 siRNA silencing suppresses the proliferation, metastasis and invasion of lung cancer cells by downregulating the ERK/CREB signaling pathway

The aim of the present study was to investigate the role of the cancer-testis antigen family 45 member A1 (CT45A1) in the proliferation, apoptosis, invasion and metastasis of lung cancer cells, and the associated molecular mechanisms. Western blotting determined that the expression of CT45A1 in normal lung cells was far lower than that observed in lung cancer cells. Following the transfection of CT45A1 small (or short) interfering (si)RNA and its negative control into A549 cells using Lipofectamine 2000, the CT45A1 protein and mRNA levels were determined further by western blotting and reverse transcription-polymerase chain reaction. Following CT45A1 siRNA transfection, the levels of CT45A1 in lung cancer cells were markedly reduced (P<0.01). Then, cell viability and apoptosis were investigated with a methyl thiazolyl tetrazolium assay and Annexin V-FITC/propidium iodide staining, respectively. Transwell assays were employed to evaluate the migration and invasion of A549 cells. When compared with the negative control, the viability, migration and invasion of lung cancer cells treated with CT45A1 siRNA were suppressed and apoptosis was promoted (all P<0.01). In addition, the levels of B-cell lymphoma-2 (Bcl-2), Bcl-2 associated X (Bax), survivin, matrix metalloproteinase 2 (MMP2), MMP9, extracellular signal-regulated kinase 1/2 (ERK1/2), phosphorylated ERK1/2 (p-ERK1/2), cyclic AMP response element binding protein (CREB) and p-CREB were assessed by western blotting. Following CT45A1 silencing, the expressions of Bcl-2, survivin, MMP2, MMP9, p-ERK1/2 and p-CREB were downregulated and the expression of Bax was upregulated (all P<0.01). It was concluded that CT45A1 siRNA silencing suppressed the proliferation, metastasis and invasion of lung cancer cells by downregulating the ERK/CREB signalling pathway.

Cyclic AMP responsive element-binding protein induces metastatic renal cell carcinoma by mediating the expression of matrix metallopeptidase-2/9 and proteins associated with epithelial-mesenchymal transition

Renal cell carcinoma (RCC) is the most frequently occurring malignancy of the kidney worldwide. Anti-angiogenic targeted therapies inhibit the progression of RCC, however, limited effects on the invasion or metastasis of tumor cells have been observed. Cyclic AMP responsive element‑binding protein (CREB) is a serine/threonine kinase that has been implicated in the regulation of cell proliferation, apoptosis, cycle progression and metastasis, amongst others. Our previous research demonstrated that phosphorylated CREB (pCREB) was upregulated in human renal cancer cell lines and tissues, and decreased pCREB at the Ser133 site inhibited the growth and metastatic activity of OS‑RC‑2 cells. However, the role of CREB in RCC metastasis requires further investigation. Thus, the present study further investigated the role of CREB in RCC metastasis. The present study demonstrated that knockdown of CREB using small interfering RNA (siRNA) that targeted CREB (siCREB) significantly inhibited the migration and invasion of 786‑O and OS‑RC‑2 cells, however, the opposite effect was observed in ACHN cells. In addition, knockdown of CREB suppressed the expression of matrix metallopeptidase (MMP)‑2/9 and proteins associated with epithelial‑mesenchymal transition (EMT) in 786‑O and OS‑RC‑2 cells, and promoted expression in ACHN cells. Furthermore, the chromatin immunoprecipitation assay indicated that pCREB (Ser133) had a direct interaction with the fibronectin promoter, however, pCREB (Ser133) did not target the vimentin promoter in RCC. Therefore, the results of the present study indicate that CREB regulated metastatic RCC by mediating the expression of MMP‑2/9 and EMT‑associated proteins, however, CREB‑mediated MMP‑2/9 and EMT‑associated protein expression may be induced by different pathways in different RCC cells.

CIP2A Promotes T-Cell Activation and Immune Response to Listeria monocytogenes Infection

The oncoprotein Cancerous Inhibitor of Protein Phosphatase 2A (CIP2A) is overexpressed in most malignancies and is an obvious candidate target protein for future cancer therapies. However, the physiological importance of CIP2A-mediated PP2A inhibition is largely unknown. As PP2A regulates immune responses, we investigated the role of CIP2A in normal immune system development and during immune response in vivo. We show that CIP2A-deficient mice (CIP2A^HOZ) present a normal immune system development and function in unchallenged conditions. However when challenged with Listeria monocytogenes, CIP2A^HOZ mice display an impaired adaptive immune response that is combined with decreased frequency of both CD4⁺ T-cells and CD8⁺ effector T-cells. Importantly, the cell autonomous effect of CIP2A deficiency for T-cell activation was confirmed. Induction of CIP2A expression during T-cell activation was dependent on Zap70 activity. Thus, we reveal CIP2A as a hitherto unrecognized mediator of T-cell activation during adaptive immune response. These results also reveal CIP2A^HOZ as a possible novel mouse model for studying the role of PP2A activity in immune regulation. On the other hand, the results also indicate that CIP2A targeting cancer therapies would not cause serious immunological side-effects.

CIP2A overexpression induces autoimmune response and enhances JNK signaling pathway in human lung cancer

Background

Cancerous inhibitor of PP2A (CIP2A) is a recently characterized oncoprotein, which promotes cancer cell proliferation. But the role of CIP2A in lung cancer progression is still not well understood.

Methods

The expression level of CIP2A in lung cancer tissues was examined by immunohistochemistry. CIP2A-associated cell proliferation was performed by knock down or overexpression of CIP2A in lung cancer cells. Phospho-array was used to screen kinase candidates related to expression change of CIP2A. Western-blot and luciferase reporter assay were used to validate phospho-array results.

Results

Overexpression of CIP2A in lung cancer not only triggers immune response in lung cancer patients but also promotes lung cancer cell proliferation. By phospho-array, several kinase candidates were identified, one of which is c-Jun activated kinases (JNK). The knock down of CIP2A decreased JNK phosphorylation, and the phosphorylation of downstream transcriptional factors, ATF2 and c-Jun, whose transcriptional activity were decreased as well. Furthermore, the expression level of CIP2A also affected the phosphorylation of the upstream kinase of JNK, MKK4/MKK7. At last, treatment with JNK inhibitor partially abolished CIP2A-induced cell proliferation.

Conclusion

CIP2A is a tumor-associated autoantigen in lung cancer, which promote lung cancer proliferation partially through MKK4/7-JNK signaling pathway.