Leucine-rich repeat-containing protein 59 mediates nuclear import of cancerous inhibitor of PP2A in prostate cancer cells

CIP2A induces PKM2 tetramer formation and oxidative phosphorylation in non-small cell lung cancer

Tumor cells are usually considered defective in mitochondrial respiration, but human non-small cell lung cancer (NSCLC) tumor tissues are shown to have enhanced glucose oxidation relative to adjacent benign lung. Here, we reported that oncoprotein cancerous inhibitor of protein phosphatase 2A (CIP2A) inhibited glycolysis and promoted oxidative metabolism in NSCLC cells. CIP2A bound to pyruvate kinase M2 (PKM2) and induced the formation of PKM2 tetramer, with serine 287 as a novel phosphorylation site essential for PKM2 dimer-tetramer switching. CIP2A redirected PKM2 to mitochondrion, leading to upregulation of Bcl2 via phosphorylating Bcl2 at threonine 69. Clinically, CIP2A level in tumor tissues was positively correlated with the level of phosphorylated PKM2 S287. CIP2A-targeting compounds synergized with glycolysis inhibitor in suppressing cell proliferation in vitro and in vivo. These results indicated that CIP2A facilitates oxidative phosphorylation by promoting tetrameric PKM2 formation, and targeting CIP2A and glycolysis exhibits therapeutic potentials in NSCLC.

Emerging roles of the CIP2A-TopBP1 complex in genome integrity

CIP2A is an inhibitor of the tumour suppressor protein phosphatase 2A. Recently, CIP2A was identified as a synthetic lethal interactor of BRCA1 and BRCA2 and a driver of basal-like breast cancers. In addition, a joint role of TopBP1 (topoisomerase IIβ-binding protein 1) and CIP2A for maintaining genome integrity during mitosis was discovered. TopBP1 has multiple functions as it is a scaffold for proteins involved in DNA replication, transcriptional regulation, cell cycle regulation and DNA repair. Here, we briefly review details of the CIP2A-TopBP1 interaction, its role in maintaining genome integrity, its involvement in cancer and its potential as a therapeutic target.

LRRC59 serves as a novel biomarker for predicting the progression and prognosis of bladder cancer

BACKGROUND

Leucine-rich repeat-containing protein 59 (LRRC59) is an endoplasmic reticulum membrane protein involved in various cancers, but its role in bladder cancer (BC) has not been reported. The aim of the present study was to investigate the role of LRRC59 protein in BC progression and prognosis.

METHODS

The expression profile and clinical significance were retrieved from BC patients in the Cancer Genome Atlas database. The methylation status of LRRC59 was analyzed by UALCAN and MethSurv databases. Potential signaling pathways and biological functions were explored by functional enrichment analysis. Immunocyte infiltration was evaluated by CIBERSORT analysis. The prognostic value of LRRC59 was evaluated by Kaplan-Meier and Cox regression analyses. Overall survival (OS) was predicted by the nomogram plot established in this study. LRRC59 expression in 10 pairs BC and adjacent noncancerous tissues were analyzed by immunohistochemistry (IHC). Cell proliferation, migration, and invasion were detected by CCK8, colony formation assay, transwell assay, and cell scratch assay, respectively. Proteins related to epithelial-mesenchymal transition and apoptosis were detected by western blot.

RESULTS

LRRC59 overexpression significantly decreased OS, disease-specific survival, and progress-free interval of BC patients. LRRC59 was a prognostic marker for OS and its hypomethylation status signified a poor prognosis. LRRC59 overexpression was correlated with infiltration of resting memory CD4 T cells, memory activated CD4 T cells, resting NK cells, macrophages M0, M1, M2, and neutrophils. IHC showed that the LRRC59 expression in BC tissue was significantly higher than that in adjacent noncancerous tissue. Knockdown of LRRC59 expression inhibited the proliferation of BC cells and reduced their migratory ability. Western blot showed that Snail and vimentin protein expressions decreased, while E-cadherin expressions increased.

CONCLUSIONS

LRRC59 expression can predict the outcome of BC independently and serve as a new biomarker for diagnosis.

Identification of leucine-rich repeat-containing protein 59 (LRRC59) located in the endoplasmic reticulum as a novel prognostic factor for urothelial carcinoma

BACKGROUND

Urothelial carcinoma (UC) is one of the most common cancers worldwide. The biological heterogeneity of UCs causes considerable difficulties in predicting treatment outcomes and usually leads to clinical mismanagement. The identification of more sensitive and efficient predictive biomarkers is important in the diagnosis and classification of UCs. Herein, we report leucine-rich repeat-containing protein 59 (LRRC59) located in the endoplasmic reticulum as a novel predictive factor and potential therapeutic target for UCs.

METHODS

Using whole-slide image analysis in our cohort of 107 UC samples, we performed immunohistochemistry to evaluate the prognostic value of LRRC59 expression in UCs. In vitro experiments using RNAi were conducted to explore the role of LRRC59 in promoting UC cell proliferation and migration.

RESULTS

A significant correlation between LRRC59 and unfavorable prognosis of UCs in our cohort was demonstrated. Subsequent clinical analysis also revealed that elevated expression levels of LRRC59 were significantly associated with higher pathological grades and advanced stages of UC. Subsequently, knockdown of LRRC59 in UM-UC-3 and T24 cells using small interfering RNA significantly inhibited cell proliferation and migration, resulting in cell cycle arrest at the G1 phase. Conversely, the overexpression of LRRC59 in UC cells enhanced cell proliferation and migration. An integrated bioinformatics analysis revealed a significant functional network of LRRC59 involving protein misfolding, ER stress, and ubiquitination. Finally, in vitro experiments demonstrated that LRRC59 modulates ER stress signaling.

CONCLUSIONS

LRRC59 expression was significantly correlated with UC prognosis. LRRC59 might not only serve as a novel prognostic biomarker for risk stratification of patients with UC but also exhibit as a potential therapeutic target in UC that warrants further investigation.

Depletion of CIP2A inhibits the proliferation, migration, invasion and epithelial-mesenchymal transition of glioma cells

CIP2A is an oncoprotein that is overexpressed in multiple solid tumours and some malignant haematologic disorders. However, its function in glioma is poorly understood. In this study, our results demonstrated that the expression of CIP2A was higher in glioma tissues than in normal tissues. Using tissue microarrays for immunohistochemistry, we found that the intensity of CIP2A expression was higher in high-grade gliomas (grade III-IV) than in low-grade gliomas (grade I-II). In addition, we found that depletion of CIP2A inhibited glioma cell proliferation, migration, invasion and epithelial-mesenchymal transition (EMT) in vitro. Taken together, our findings revealed that CIP2A was involved in glioma progression, indicating that CIP2A could be used as a potential therapeutic target in the future.

Folylpoly-ɣ-glutamate synthetase association to the cytoskeleton: Implications to folate metabolon compartmentalization

Folates are essential for nucleotide biosynthesis, amino acid metabolism and cellular proliferation. Following carrier-mediated uptake, folates are polyglutamylated by folylpoly-ɣ-glutamate synthetase (FPGS), resulting in their intracellular retention. FPGS appears as a long isoform, directed to mitochondria via a leader sequence, and a short isoform reported as a soluble cytosolic protein (cFPGS). However, since folates are labile and folate metabolism is compartmentalized, we herein hypothesized that cFPGS is associated with the cytoskeleton, to couple folate uptake and polyglutamylation and channel folate polyglutamates to metabolon compartments. We show that cFPGS is a cytoskeleton-microtubule associated protein: Western blot analysis revealed that endogenous cFPGS is associated with the insoluble cellular fraction, i.e., cytoskeleton and membranes, but not with the cytosol. Mass spectrometry analysis identified the putative cFPGS interactome primarily consisting of microtubule subunits and cytoskeletal motor proteins. Consistently, immunofluorescence microscopy with cytosol-depleted cells demonstrated the association of cFPGS with the cytoskeleton and unconventional myosin-1c. Furthermore, since anti-microtubule, anti-actin cytoskeleton, and coatomer dissociation-inducing agents yielded perinuclear pausing of cFPGS, we propose an actin- and microtubule-dependent transport of cFPGS between the ER-Golgi and the plasma membrane. These novel findings support the coupling of folate transport with polyglutamylation and folate channeling to intracellular metabolon compartments. SIGNIFICANCE: FPGS, an essential enzyme catalyzing intracellular folate polyglutamylation and efficient retention, was described as a soluble cytosolic enzyme in the past 40 years. However, based on the lability of folates and the compartmentalization of folate metabolism and nucleotide biosynthesis, we herein hypothesized that cytoplasmic FPGS is associated with the cytoskeleton, to couple folate transport and polyglutamylation as well as channel folate polyglutamates to biosynthetic metabolon compartments. Indeed, using complementary techniques including Mass-spectrometry proteomics and fluorescence microscopy, we show that cytoplasmic FPGS is associated with the cytoskeleton and unconventional myosin-1c. This novel cytoskeletal localization of cytoplasmic FPGS supports the dynamic channeling of polyglutamylated folates to metabolon compartments to avoid oxidation and intracellular dilution of folates, while enhancing folate-dependent de novo biosynthesis of nucleotides and DNA/protein methylation.

Progress in Delivery of siRNA-Based Therapeutics Employing Nano-Vehicles for Treatment of Prostate Cancer

Prostate cancer (PCa) accounts for a high number of deaths in males with no available curative treatments. Patients with PCa are commonly diagnosed in advanced stages due to the lack of symptoms in the early stages. Recently, the research focus was directed toward gene editing in cancer therapy. Small interfering RNA (siRNA) intervention is considered as a powerful tool for gene silencing (knockdown), enabling the suppression of oncogene factors in cancer. This strategy is applied to the treatment of various cancers including PCa. The siRNA can inhibit proliferation and invasion of PCa cells and is able to promote the anti-tumor activity of chemotherapeutic agents. However, the off-target effects of siRNA therapy remarkably reduce its efficacy in PCa therapy. To date, various carriers were designed to improve the delivery of siRNA and, among them, nanoparticles are of importance. Nanoparticles enable the targeted delivery of siRNAs and enhance their potential in the downregulation of target genes of interest. Additionally, nanoparticles can provide a platform for the co-delivery of siRNAs and anti-tumor drugs, resulting in decreased growth and migration of PCa cells. The efficacy, specificity, and delivery of siRNAs are comprehensively discussed in this review to direct further studies toward using siRNAs and their nanoscale-delivery systems in PCa therapy and perhaps other cancer types.

Overexpression of LRRC59 Is Associated with Poor Prognosis and Promotes Cell Proliferation and Invasion in Lung Adenocarcinoma

Aim

LRRC59 (leucine-rich repeat-containing protein 59) is a ribosome-binding protein that also interacts with fibroblast growth factors. Limited investigations revealed a possible role of LRRC59 in the aggressive phenotype of breast cancer. However, whether LRRC59 contributes to the progression of lung cancer remains unclear.

Materials and Methods

In this study, an online TCGA-based survival analysis software (GEPIA2) was used to estimate the prognostic value of LRRC59 mRNA expression level for lung cancer. Cell Counting Kit-8 assay, colony-forming assay, cell cycle analysis, and transwell assay were used to assess the biological functions of LRRC59 in lung cancer cells. Then, 94 lung adenocarcinoma (LUAD) patient tissues were collected to examine the expression level of LRRC59 by the tissue microarray (TMA)-based immunohistochemistry staining (IHC). Univariate Kaplan-Meier and multivariate Cox regression analyses were performed to evaluate the prognostic value of LRRC59 protein expression in LUAD.

Results

Higher mRNA level of LRRC59 was significantly associated with worse survival for lung adenocarcinoma, but not for lung squamous cell carcinoma. Knockdown of LRRC59 by shRNA apparently inhibited cell proliferation and colony formation in both H1299 and A549 cells. The G1/S phase arrest induced by LRRC59 depletion was observed in A549 and H1299 cells. Besides, the silencing of LRRC59 decreased cell migrative and invasive abilities. Moreover, TMA-based IHC showed that LRRC59 was highly expressed in LUAD tissues and closely associated with lymph node metastasis (P<0.001), TNM stage (P<0.001), and histological differentiation (P=0.007). Further multivariate analysis suggested that LRRC59 overexpression was an independent prognostic factor in LUAD.

Conclusion

LRRC59 may serve as a novel biomarkers and therapeutic target for LUAD clinical practice.

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.

Identification and Clinical Validation of a Novel 4 Gene-Signature with Prognostic Utility in Colorectal Cancer

Colorectal cancer (CRC) is a high burden disease with several genes involved in tumor progression. The aim of the present study was to identify, generate and clinically validate a novel gene signature to improve prediction of overall survival (OS) to effectively manage colorectal cancer. We explored The Cancer Genome Atlas (TCGA), COAD and READ datasets (597 samples) from The Protein Atlas (TPA) database to extract a total of 595 candidate genes. In parallel, we identified 29 genes with perturbations in > 6 cancers which are also affected in CRC. These genes were entered in cBioportal to generate a 17 gene panel with highest perturbations. For clinical validation, this gene panel was tested on the FFPE tissues of colorectal cancer patients (88 patients) using Nanostring analysis. Using multivariate analysis, a high prognostic score (composite 4 gene signature-DPP7/2, YWHAB, MCM4 and FBXO46) was found to be a significant predictor of poor prognosis in CRC patients (HR: 3.42, 95% CI: 1.71-7.94, p < 0.001 *) along with stage (HR: 4.56, 95% CI: 1.35-19.15, p = 0.01 *). The Kaplan-Meier analysis also segregated patients on the basis of prognostic score (log-rank test, p = 0.001 *). The external validation using GEO dataset (GSE38832, 122 patients) corroborated the prognostic score (HR: 2.7, 95% CI: 1.99-3.73, p < 0.001 *). Additionally, higher score was able to differentiate stage II and III patients (130 patients) on the basis of OS (HR: 2.5, 95% CI: 1.78-3.63, p < 0.001 *). Overall, our results identify a novel 4 gene prognostic signature that has clinical utility in colorectal cancer.

Targeting of LRRC59 to the Endoplasmic Reticulum and the Inner Nuclear Membrane

LRRC59 (leucine-rich repeat-containing protein 59) is a tail-anchored protein with a single transmembrane domain close to its C-terminal end that localizes to the endoplasmic reticulum (ER) and the nuclear envelope. Here, we investigate the mechanisms of membrane integration of LRRC59 and its targeting to the inner nuclear membrane (INM). Using purified microsomes, we show that LRRC59 can be post-translationally inserted into ER-derived membranes. The TRC-pathway, a major route for post-translational membrane insertion, is not required for LRRC59. Like emerin, another tail-anchored protein, LRRC59 reaches the INM, as demonstrated by rapamycin-dependent dimerization assays. Using different approaches to inhibit importin α/β-dependent nuclear import of soluble proteins, we show that the classic nuclear transport machinery does not play a major role in INM-targeting of LRRC59. Instead, the size of the cytoplasmic domain of LRRC59 is an important feature, suggesting that targeting is governed by passive diffusion.

siRNA-Mediated Silencing of CIP2A Enhances Docetaxel Activity Against PC-3 Prostate Cancer Cells

Purpose: Cancerous inhibitor of protein phosphatase 2A (CIP2A) is an identified human oncoprotein which modulates malignant cell growth. It is overexpressed in human prostate cancer and in most of the human malignancies. The aim of this study was to investigate the effects of CIP2A silencing on the sensitivity of PC-3 prostate cancer cells to docetaxel chemotherapy.

Methods: PC-3 cells were transfected using CIP2A siRNA. CIP2A mRNA and protein expression were assessed after CIP2A gene silencing using q-RT PCR and Western blotting. Proliferation and apoptosis were analyzed after treatment with docetaxol using MTT assay, DAPI staining, and flow cytometry, respectively.

Results: Silencing of CIP2A enhanced the sensitivity of PC-3 cells to docetaxel by strengthening docetaxel induced cell growth inhibition and apoptosis against PC-3 cells.

Conclusion: Silencing of CIP2A may potentiate the cytotoxic effects of docetaxel and this might be a promising therapeutic approach in prostate cancer treatment.

CIP2A acts as a scaffold for CEP192-mediated microtubule organizing center assembly by recruiting Plk1 and aurora A during meiotic maturation

In somatic cells spindle microtubules are nucleated from centrosomes that act as major microtubule organizing centers (MTOCs), whereas oocytes form meiotic spindles by assembling multiple acentriolar MTOCs without canonical centrosomes. Aurora A and Plk1 are required for these events, but the underlying mechanisms remain largely unknown. Here we show that CIP2A regulates MTOC organization by recruiting aurora A and Plk1 at spindle poles during meiotic maturation. CIP2A colocalized with pericentrin at spindle poles with a few distinct cytoplasmic foci. Although CIP2A has been identified as an endogenous inhibitor of protein phosphatase 2A (PP2A), overexpression of CIP2A had no effect on meiotic maturation. Depletion of CIP2A perturbed normal spindle organization and chromosome alignment by impairing MTOC organization. Importantly, CIP2A was reciprocally associated with CEP192, promoting recruitment of aurora A and Plk1 at MTOCs. CIP2A was phosphorylated by Plk1 at S904, which targets CIP2A to MTOCs and facilitates MTOC organization with CEP192. Our results suggest that CIP2A acts as a scaffold for CEP192-mediated MTOC assembly by recruiting Plk1 and aurora A during meiotic maturation in mouse oocytes.

Splenic microRNA Expression Profiles and Integration Analyses Involved in Host Responses to Salmonella enteritidis Infection in Chickens

To understand the role of miRNAs in regulating genes involved in the host response to Salmonella enteritidis (SE) infection, next generation sequencing was applied to explore the altered splenic expression of microRNAs (miRNAs) and deregulated genes in specific-pathogen-free chickens. Birds were either infected or not (controls, C) and those challenged with SE were evaluated 24 h later and separated into two groups on the basis of the severity of clinical symptoms and blood load of SE: resistant (R, SE challenged-slight clinical symptoms and <105 cfu / 10 μL), and susceptible (S, SE challenged-severe clinical symptoms and >107 cfu/10 μL). Thirty-two differentially expressed (DE) miRNAs were identified in spleen, including 16 miRNAs between S and C, 13 between R and C, and 13 between S and R. Through integration analysis of DE miRNAs and mRNA, a total of 273 miRNA-target genes were identified. Functional annotation analysis showed that Apoptosis and NOD-like receptor signaling pathway and adaptive immune response were significantly enriched (P < 0.05). Interestingly, apoptosis pathway was significantly enriched in S vs. C, while NOD-like receptor pathway was enriched in R vs. C (P < 0.05). Two miRNAs, gga-miR-101-3p and gga-miR-155, in the hub positions of the miRNA-mRNA regulatory network, were identified as candidates potentially associated with SE infection. These 2 miRNAs directly repressed luciferase reporter gene activity via binding to 3'-untranslated regions of immune-related genes IRF4 and LRRC59; over-expressed gga-miR-155 and interference gga-miR-101-3p in chicken HD11 macrophage cells significantly altered expression of their target genes and decreased the production of pro-inflammatory cytokines. These findings facilitate better understanding of the mechanisms of host resistance and susceptibility to SE infection in chickens.

LRRC59 Regulates Trafficking of Nucleic Acid-Sensing TLRs from the Endoplasmic Reticulum via Association with UNC93B1

Compartmentalization of nucleic acid (NA)-sensing TLR3, 7, 8, and 9 is strictly regulated to direct optimal response against microbial infection and evade recognition of host-derived NAs. Uncoordinated 93 homolog B1 (UNC93B1) is indispensable for trafficking of NA-sensing TLRs from the endoplasmic reticulum (ER) to endosomes/lysosomes. UNC93B1 controls loading of the TLRs into COPII vesicles to exit from the ER and traffics with the TLRs in the steady state. Ligand-induced translocation also happens on NA-sensing TLRs. However, the molecular mechanism for ligand-dependent trafficking of TLRs from the ER to endosomes/lysosomes remains unclear. In this study, we demonstrated that leucine-rich repeat containing protein (LRRC) 59, an ER membrane protein, participated in trafficking of NA-sensing TLRs from the ER. Knockdown of LRRC59 reduced TLR3-, 8-, and 9-mediated, but not TLR4-mediated, signaling. Upon ligand stimulation, LRRC59 associated with UNC93B1 in a TLR-independent manner, which required signals induced by ligand internalization. Endosomal localization of endogenous TLR3 was decreased by silencing of LRRC59, suggesting that LRRC59 promotes UNC93B1-mediated translocation of NA-sensing TLRs from the ER upon infection. These findings help us understand how NA-sensing TLRs control their proper distribution in the infection/inflammatory state.