Flotillin-2 promotes metastasis of nasopharyngeal carcinoma by activating NF-κB and PI3K/Akt3 signaling pathways

Precision medicine in nasopharyngeal carcinoma: comprehensive review of past, present, and future prospect

Nasopharyngeal carcinoma (NPC) is an aggressive malignancy with high propensity for lymphatic spread and distant metastasis. It is prominent as an endemic malignancy in Southern China and Southeast Asia regions. Studies on NPC pathogenesis mechanism in the past decades such as through Epstein Barr Virus (EBV) infection and oncogenic molecular aberrations have explored several potential targets for therapy and diagnosis. The EBV infection introduces oncoviral proteins that consequently hyperactivate many promitotic pathways and block cell-death inducers. EBV infection is so prevalent in NPC patients such that EBV serological tests were used to diagnose and screen NPC patients. On the other hand, as the downstream effectors of oncogenic mechanisms, the promitotic pathways can potentially be exploited therapeutically. With the apparent heterogeneity and distinct molecular aberrations of NPC tumor, the focus has turned into a more personalized treatment in NPC. Herein in this comprehensive review, we depict the current status of screening, diagnosis, treatment, and prevention in NPC. Subsequently, based on the limitations on those aspects, we look at their potential improvements in moving towards the path of precision medicine. The importance of recent advances on the key molecular aberration involved in pathogenesis of NPC for precision medicine progression has also been reported in the present review. Besides, the challenge and future outlook of NPC management will also be highlighted.

Platycodonis Radix Alleviates LPS-Induced Lung Inflammation through Modulation of TRPA1 Channels

Platycodonis Radix (PR), a widely consumed herbal food, and its bioactive constituents, platycodins, have therapeutic potential for lung inflammation. Transient Receptor Potential Ankyrin 1 (TRPA1), which is essential for the control of inflammation, may be involved in the development of inflammation in the lungs. The aim of this study was to determine the TRPA1-targeted effects of PR against pulmonary inflammation and to investigate the affinity of PR constituents for TRPA1 and their potential mechanisms of action. Using a C57BL/6J mouse lipopolysaccharides (LPS) intratracheal instillation pneumonia model and advanced analytical techniques (UPLC-Q-TOF-MS/MS, molecular docking, immuno-fluorescence), five platycodins were isolated from PR, and the interaction between these platycodins and hTRPA1 was verified. Additionally, we analyzed the impact of platycodins on LPS-induced TRPA1 expression and calcium influx in BEAS-2B cells. The results indicated that PR treatment significantly reduced the severity of LPS-triggered inflammation in the mouse model. Interestingly, there was a mild increase in the expression of TRPA1 caused by PR in healthy mice. Among five isolated platycodins identified in the PR extract, Platycodin D₃ (PD₃) showed the highest affinity for hTRPA1. The interaction between platycodins and TRPA1 was verified through molecular docking methods, highlighting the significance of the S5-S6 pore-forming loop in TRPA1 and the unique structural attributes of platycodins. Furthermore, PD₃ significantly reduced LPS-induced TRPA1 expression and calcium ion influx in BEAS-2B cells, substantiating its own role as an effective TRPA1 modulator. In conclusion, PR and platycodins, especially PD₃, show promise as potential lung inflammation therapeutics. Further research should explore the precise mechanisms by which platycodins modulate TRPA1 and their broader therapeutic potential.

ESRG is critical to maintain the cell survival and self-renewal/pluripotency of hPSCs by collaborating with MCM2 to suppress p53 pathway

The mechanisms of self-renewal and pluripotency maintenance of human pluripotent stem cells (hPSCs) have not been fully elucidated, especially for the role of those poorly characterized long noncoding RNAs (lncRNAs). ESRG is a lncRNA highly expressed in hPSCs, and its functional roles are being extensively explored in the field. Here, we identified that the transcription of ESRG can be directly regulated by OCT4, a key self-renewal factor in hPSCs. Knockdown of ESRG induces hPSC differentiation, cell cycle arrest, and apoptosis. ESRG binds to MCM2, a replication-licensing factor, to sustain its steady-state level and nuclear location, safeguarding error-free DNA replication. Further study showed that ESRG knockdown leads to MCM2 abnormalities, resulting in DNA damage and activation of the p53 pathway, ultimately impairs hPSC self-renewal and pluripotency, and induces cell apoptosis. In summary, our study suggests that ESRG, as a novel target of OCT4, plays an essential role in maintaining the cell survival and self-renewal/pluripotency of hPSCs in collaboration with MCM2 to suppress p53 signaling. These findings provide critical insights into the mechanisms underlying the maintenance of self-renewal and pluripotency in hPSCs by lncRNAs.

Function of AXL and molecular mechanisms in regulation of nasopharyngeal carcinoma

OBJECTIVES

Nasopharyngeal carcinoma (NPC) is a highly invasive epithelial malignant tumor with unique geographical and ethnic distribution characteristics. NPC is mostly found in south China and Southeast Asia, and its treatment mainly depends on radiotherapy and chemotherapy. However, NPC is usually found in the late stage, and local recurrence and distant metastasis are common, leading to poor prognosis. The receptor tyrosine kinase AXL is up-regulated in various tumors and it is involved in tumor proliferation, migration, invasion, and other processes, which are associated with poor prognosis of tumors. This study aims to detect the expression of AXL in NPC cell lines and tissues, and to investigate its biological function of AXL and the underlying molecular mechanisms in regulation of NPC.

METHODS

The expression levels of AXL in normal nasopharyngeal epithelial tissues and NPC tissues were analyzed by GSE68799, GSE12452, and GSE53819 data sets based on Gene Expression Omnibus (GEO) database. The Cancer Genome Atlas (TCGA) database was used to analyze the relationship between AXL and prognosis of head and neck squamous cell carcinoma (HNSC). The indicators of prognosis included overall survival (OS), disease-free interval (DFI), disease-specific survival (DSS), and progression-free interval (PFI). Western blotting assay was used to detect the AXL protein expression levels in normal nasopharyngeal epithelial cell line and NPC cell lines. Immunohistochemical method was used to detect AXL expression levels in normal nasopharyngeal epithelial tissues and NPC tissues. Cell lines with stable AXL knockdown were established by infecting 5-8F and Fadu cells with lentivirus interference vector, and cell lines with stable AXL overexpression were established by infecting C666-1 and HK-1 cells with lentivirus expression vector. Real-time PCR and Western blotting were used to detect the efficiency of knockdown and overexpression in stable cell lines. The effects of AXL knockdown or overexpression on proliferation, migration, and invasion of NPC cells were detected by CCK-8, plate colony formation, and Transwell assays, and the effect of AXL knockdown on tumor growth in nude mice was detected by subcutaneous tumor formation assay. The sequence of AXL upstream 2.0 kb promoter region was obtained by UCSC online database. The PROMO online database was used to predict AXL transcription factors with 0% fault tolerance, and the JASPAR online database was used to predict the binding sites of ETS1 to AXL. Real-time PCR and Western blotting were used to detect the effect of ETS1 on AXL protein and mRNA expression. The AXL upstream 2.0 kb promoter region was divided into 8 fragments, each of which was 250 bp in length. Primers were designed for 8 fragments. The binding of ETS1 to AXL promoter region was detected by chromatin immuno-precipitation (ChIP) assay to determine the direct regulatory relationship between ETS1 and AXL. Rescue assay was used to determine whether ETS1 affected the proliferation, migration, and invasion of NPC cells through AXL.

RESULTS

Bioinformatics analysis showed that AXL was highly expressed in NPC tissues (P<0.05), and AXL expression was positively correlated with OS, DFI, DSS, and PFI in HNSC patients. Western blotting and immunohistochemical results showed that AXL was highly expressed in NPC cell lines and tissues compared with the normal nasopharyngeal epithelial cell line and tissues. Real-time PCR and Western blotting results showed that knockdown and overexpression efficiency in the stable cell lines met the requirements of subsequent experiments. The results of CCK-8, plate colony formation, Transwell assays and subcutaneous tumor formation in nude mice showed that down-regulation of AXL significantly inhibited the proliferation, migration, invasion of NPC cells and tumor growth (all P<0.05), and the up-regulation of AXL significantly promoted the proliferation, migration, and invasion of NPC cells (all P<0.05).As predicted by PROMO and JASPAR online databases, ETS1 was a transcription factor of AXL and had multiple binding sites in the AXL promoter region. Real-time PCR and Western blotting results showed that knockdown or overexpression of ETS1 down-regulated or up-regulated AXL protein and mRNA expression levels. ChIP assay result showed that ETS1 bound to AXL promoter region and directly regulate AXL expression. Rescue assay showed that AXL rescued the effects of ETS1 on proliferation, migration and invasion of NPC cells (P<0.05).

CONCLUSIONS

AXL is highly expressed in NPC cell lines and tissues, which can promote the malignant progression of NPC, and its expression is regulated by transcription factor ETS1.

The Potential Role of Exosomal Proteins in Prostate Cancer

Prostate cancer is the most prevalent malignant tumor in men across developed countries. Traditional diagnostic and therapeutic methods for this tumor have become increasingly difficult to adapt to today’s medical philosophy, thus compromising early detection, diagnosis, and treatment. Prospecting for new diagnostic markers and therapeutic targets has become a hot topic in today’s research. Notably, exosomes, small vesicles characterized by a phospholipid bilayer structure released by cells that is capable of delivering different types of cargo that target specific cells to regulate biological properties, have been extensively studied. Exosomes composition, coupled with their interactions with cells make them multifaceted regulators in cancer development. Numerous studies have described the role of prostate cancer-derived exosomal proteins in diagnosis and treatment of prostate cancer. However, so far, there is no relevant literature to systematically summarize its role in tumors, which brings obstacles to the later research of related proteins. In this review, we summarize exosomal proteins derived from prostate cancer from different sources and summarize their roles in tumor development and drug resistance.

UBE2T is upregulated, predicts poor prognosis, and promotes cell proliferation and invasion by promoting epithelial-mesenchymal transition via inhibiting autophagy in an AKT/mTOR dependent manner in ovarian cancer

Aberrant upregulation and oncogenic roles of UBE2T are revealed in several cancers. However, the expression, clinical significance, and functions of UBE2T have not been explored in ovarian cancer (OC). In this study, the expression of UBE2T and its relation with clinicopathological features and prognosis of OC patients were explored by analyzing online data and experimental data. Besides, the functions of UBE2T in OC cells were investigated by in vitro experiments, including CCK-8, plate clone formation, and Transwell assays. Finally, the underlying mechanism of UBE2T associated functions in OC was analyzed. The results indicated that UBE2T was significantly upregulated in OC tissues. UBE2T expression was notably correlated with clinical features, such as primary T stage and FIGO stage in OC patients. UBE2T, acting as an independent prognostic indicator, was inversely associated with the prognosis of OC patients. The UBE2T knockdown remarkably suppressed the growth, proliferation, and invasion of OC cells, indicated by impaired cell viability, fewer cell clones, and invasive cells. Mechanistically, UBE2T depletion suppressed epithelial-mesenchymal transition (EMT), which was caused by autophagy activation due to inactivation of AKT/mTOR in OC cells with UBE2T knockdown. Collectively, our findings confirm that UBE2T upregulation predicts poor prognosis and promotes malignant progression in OC. UBE2T upregulation suppresses autophagy and subsequently boosts EMT via activating the AKT/mTOR axis, which accounts for the underlying mechanism of oncogenic roles of UBE2T in OC.

The differential role of the lipid raft-associated protein flotillin 2 for progression of myeloid leukemia

Lipid raft-associated proteins play a vital role in membrane-mediated processes. The lipid microdomain-associated protein flotillin 2 (FLOT2), which has scaffolding function, is involved in polarization, as well as in actin cytoskeletal organization of primitive and mature hematopoietic cells and has been associated with different malignancies. However, its involvement in myeloid leukemias is not well studied. Using murine transplantation models, we show here that absence of FLOT2 from leukemia- initiating cells (LIC) altered disease course of BCR-ABL1+ chronic myeloid leukemia (CML), but not of MLL-AF9-driven acute myeloid leukemia (AML). While FLOT2 was required for expression of the adhesion molecule CD44 on both CML- and AML-LIC, a defect in the cytoskeleton, cell polarity and impaired homing ability of LIC was only observed in FLOT2-deficient BCR-ABL1+ compared to MLL-AF9+ cells. Downstream of CD44, BCR-ABL1-kinase-independent discrepancies were observed regarding expression, localization and activity of cell division control protein 42 homolog (CDC42) between wildtype and FLOT2-deficient human CML and AML cells. Inhibition of CDC42 by ML141 impaired the homing of CML LIC and, thereby, CML progression. This suggested that alteration of both CD44 and CDC42 may be causative of impaired CML progression in absence of FLOT2. In summary, our data suggest a FLOT2-CD44-CDC42 axis, which differentially regulates CML versus AML progression, with deficiency of FLOT2 impairing the development of CML.

MicroRNA-486-3p promotes the proliferation and metastasis of cutaneous squamous cell carcinoma by suppressing flotillin-2

BACKGROUND

Dysregulation of miR-486-3p was related to the growth and development of a variety of cancers, but the specific function of miR-486-3p in cutaneous squamous cell carcinoma (cSCC) is not to be confirmed yet.

OBJECTIVE

Our present study aimed to validate the potential molecular mechanisms of miR-486-3p in cSCC and the potential of miR-486-3p as a novel target for future treatment.

METHODS

Human cSCC samples and normal skin tissues were applied to determine the expression level of miR-486-3p and FLOT2 by fluorescence in situ hybridization (FISH) and quantitative reverse transcription PCR (qRT-PCR), respectively. As well as BALB/C nude mouse tumor model, three cSCC cells lines including HSC-1, HSC-5 and A431 were utilized to demonstrate the potential function of miR-486-3p and FLOT2 in tumorigenesis.

RESULTS

Our experimental results showed that miR-486-3p was highly expressed both in tumor samples and cell lines of cSCC. Upregulation of miR-486-3p enhanced the proliferation and migration ability of cSCC cell lines and promoted tumorigenicity in vivo. Furthermore, we confirmed that FLOT2 was a direct targeted gene of miR-486-3p. In contrary to the expression level of miR-486-3p, FLOT2 was low expressed in cSCC patient specimens and cell lines. Knockdown of FLOT2 promoted tumorigenesis of cSCC; whereas FLOT2 reversed the tumor-promoting effect of miR-486-3p.

CONCLUSION

Our data exhibited that miR-486-3p exerted its effects on carcinogenesis as an oncogene in cSCC via suppression of FLOT2. This discovery will develop new therapeutic targets of cSCC.

miR-34a-5p functions as a tumor suppressor in head and neck squamous cell cancer progression by targeting Flotillin-2

While a number of therapeutic advances have been made in recent years, the overall survival of patients with head and neck squamous cell cancer (HNSCC) remains poor. MicroRNAs (miRNAs) are key drivers of oncogenic progression, with miR-34a-5p downregulation having been observed in many different tumor types. Here, we assessed the link between miR-34a-5p and HNSCC progression and the mechanistic basis for this relationship. Levels of miR-34a-5p in HNSCC tumors and cell lines were assessed via qPCR, after which we explored the functional importance of this miRNA in this oncogenic setting. Through luciferase reporter assays, the ability of miR-34a-5p to regulate flotillin-2 (FLOT-2) was further clarified. Overall, these analyses revealed that HNSCC tumors and cells exhibited marked miR-34a-5p downregulation that was linked to the progression of this tumor type. At a functional level, miR-34a-5p constrained the proliferation, migratory/invasive activity, and epithelial-mesenchymal transition induction in HNSCC cells. At the mechanistic level, miR-34a-5p was found to suppress FLOT-2 expression and to activate the MEK/ERK1/2 pathway. Overall, these results suggest that miR-34a-5p can function as a tumor suppressor miRNA in HNSCC owing to its ability to target FLOT-2, highlighting the promise of targeting this regulatory axis to treat HNSCC.

The clinical features, prognostic significance, and immune heterogeneity of CD37 in diffuse gliomas

Diffuse glioma is the most prevalent and malignant brain tumor. The function and significance of CD37 in diffuse gliomas remain largely unknown. Here, we showed CD37 was abnormally expressed in diverse cancers, especially glioma by pan-cancer differential expression analysis. In addition, we found CD37 was upregulated in higher grade and IDH or IDH1-wildtype gliomas, which was further validated by qPCR and IHC. Survival analysis revealed CD37 served as an independent indicator for unfavorable prognosis of patients with diffuse gliomas. Functional enrichment analysis revealed CD37 was associated with immunological processes. Moreover, immune infiltration analyses suggested gliomas with high-expression CD37 had greater infiltration of M2 macrophages and neutrophils, and lower NK cell abundance. CD37 was closely correlated to immune checkpoint molecules, including CD276, CD80, CD86, and PD-L2. Our results indicated CD37 is an independent prognostic factor and plays an immunosuppressive role in diffuse gliomas. Targeting CD37 could be a promising immunotherapeutic strategy for diffuse gliomas.

miR-182-5p and miR-96-5p Target PIAS1 and Mediate the Negative Feedback Regulatory Loop between PIAS1 and STAT3 in Endometrial Cancer

The expressions and roles of protein inhibitor of activated STAT (PIAS) proteins, a group of proteins with STAT inhibition and SUMOylation E3 ligase activity, are rarely revealed in endometrial cancer (EC). In this study, we analyzed the expressions of PIASs and their relationships with clinical features by mining online data through web servers, including UALCAN and Gene Expression Profiling Interactive Analysis (GEPIA) in EC. The expressions of PIASs in EC tissues were further validated by immunohistochemistry (IHC). The online analyses revealed only PIAS1 was consistently downregulated both at mRNA and protein level in EC, which was validated by the IHC. Subsequently, the mechanism of PIAS1 downregulation was explored with online tools like UALCAN, cBioPortal, LinkedOmics, and the Encyclopedia of RNA Interactomes (ENCORI). The results indicated that the mutation rate of PIAS1 was extremely low and not associated with PIAS1 expression. The promoter methylation level of PIAS1 was comparable between normal and EC tissues. miR-182-5p and miR-96-5p with negative association with PIAS1 in EC were predicted to target PIAS1. Dual luciferase reporter assay confirmed miR-182-5p and miR-96-5p could target PIAS1 in EC. MiR-182-5p and miR-96-5p inhibitors could upregulate PIAS1 in EC cells. Moreover, ectopic PIAS1 expression and STAT3 inhibitor treatment significantly inhibited STAT3's activity and the levels of miR-182-5p and miR-96-5p in EC cells. Collectively, our findings revealed PIAS1 was downregulated in EC, which was caused by upregulation of miR-182-5p and miR-96-5p, and PIAS1 downregulation further activated STAT3 and increased the expression of miR-182-5p and miR-96-5p, confirming miR-182-5p and miR-96-5p mediated the negative feedback regulatory loop between PIAS1 and STAT3 in EC.

Flotillin-2 promotes cell proliferation via activating the c-Myc/BCAT1 axis by suppressing miR-33b-5p in nasopharyngeal carcinoma

Previously, we elucidated the function of flotilin-2 (FLOT2) and branched-chain amino acid transaminase 1(BCAT1) in nasopharyngeal carcinoma (NPC). However, the relationship between FLOT2 and BCAT1 in promoting NPC progression remains unknown. Here, we observed that FLOT2 upregulated BCAT1 expression in NPC cells. Ectopic expression of BCAT1 significantly antagonized the inhibitory effects on NPC cell proliferation induced by FLOT2 depletion. Consequently, BCAT1 knockdown markedly inhibited the pro-proliferative effects of FLOT2 overexpression in NPC cells. FLOT2 expression was positively correlated with BCAT1 expression in NPC tissues and was inversely correlated with the prognosis of NPC patients. Mechanistically, FLOT2 maintains the expression level of c-Myc, a positive transcription factor of BCAT1, and subsequently promote BCAT1 transcription. FLOT2 inhibited miR-33b-5p in NPC cells and attenuated its inhibitory effects on c-Myc. Further, experimental validation of the function of the FLOT2/miR-33b-5p/c-Myc/BCAT1 axis in regulating NPC cell proliferation was performed. Our results revealed that FLOT2 promotes NPC cell proliferation by suppressing miR-33b-5p, to maintain proper levels of c-Myc, and upregulate BCAT1trancription. Therefore, the FLOT2/miR-33b-5p/c-Myc/BCAT1 axis is a potential therapeutic target for NPC.

FLOT2 upregulation promotes growth and invasion by interacting and stabilizing EphA2 in gliomas

The expression and roles of FLOT2, especially for its underlying mechanism, in gliomas have been rarely revealed. In this study, upregulations of both FLOT2 and EphA2 in gliomas tissues were validated by immunohistochemistry (IHC) staining and Western blot. FLOT2 silencing notably inhibited the growth and invasion of gliomas cells. Simultaneously, FLOT2 depletion suppressed Akt and NF-κB activities, induced apoptosis, cell cycle arrest, and epithelial-mesenchymal transition (EMT) inhibition, demonstrated by expression alterations of key proteins of the above processes. Mechanistically, FLOT2 could maintain EphA2 stability viainteraction, and restoration of EphA2 could remarkably release the suppressive effects on gliomas cells induced by FLOT2 knockdown. Lastly, FLOT2 and EphA2, whose protein and mRNA levels are both positively correlated in gliomas, shows significant association with clinical characteristics like Ki67 intensity, p53 expression, and tumor stage in patients with gliomas. In conclusion, our results reveal the upregulation, oncogenic roles of FLOT2, and the corresponding underlying mechanism in gliomas, highlighting that the FLOT2-EphA2 axis is served as a promising therapeutic target for gliomas.

Flotillin membrane domains in cancer

Flotillins 1 and 2 are two ubiquitous, highly conserved homologous proteins that assemble to form heterotetramers at the cytoplasmic face of the plasma membrane in cholesterol- and sphingolipid-enriched domains. Flotillin heterotetramers can assemble into large oligomers to form molecular scaffolds that regulate the clustering of at the plasma membrane and activity of several receptors. Moreover, flotillins are upregulated in many invasive carcinomas and also in sarcoma, and this is associated with poor prognosis and metastasis formation. When upregulated, flotillins promote plasma membrane invagination and induce an endocytic pathway that allows the targeting of cargo proteins in the late endosomal compartment in which flotillins accumulate. These late endosomes are not degradative, and participate in the recycling and secretion of protein cargos. The cargos of this Upregulated Flotillin–Induced Trafficking (UFIT) pathway include molecules involved in signaling, adhesion, and extracellular matrix remodeling, thus favoring the acquisition of an invasive cellular behavior leading to metastasis formation. Thus, flotillin presence from the plasma membrane to the late endosomal compartment influences the activity, and even modifies the trafficking and fate of key protein cargos, favoring the development of diseases, for instance tumors. This review summarizes the current knowledge on flotillins and their role in cancer development focusing on their function in cellular membrane remodeling and vesicular trafficking regulation.

SIRT6 inhibits metastasis by suppressing SNAIL expression in nasopharyngeal carcinoma cells

Nasopharyngeal carcinoma (NPC) is a head and neck cancer with severe local invasion and early distant metastasis. SIRT6 serves as a critical modulator of the development and metastasis of multiple types of cancer; however, the roles and underlying mechanisms of SIRT6 in regulating NPC metastasis remain largely unknown. Here, the expression of SIRT6 in high metastatic 5-8F cells and low metastatic 6-10B cells was analyzed. SIRT6 expression was found to be negatively associated with the metastatic capability of NPC cells. Moreover, we identified that SIRT6 inhibited NPC cell metastasis through suppression of SNAIL expression. Mechanistically, we demonstrated that SIRT6 interacted with transcription factor p65 (NF-kB subunit) and deacetylated histone H3 lysine 9 (H3K9) and lysine 56 (H3K56) at the promoter of SNAIL, leading to reduced transcription of SNAIL. In summary, SIRT6 functions as a metastasis suppressor in NPC cells through epigenetic regulation of SNAIL gene expression.

Rafting Down the Metastatic Cascade: The Role of Lipid Rafts in Cancer Metastasis, Cell Death, and Clinical Outcomes

Lipid rafts are tightly packed, cholesterol- and sphingolipid-enriched microdomains within the plasma membrane that play important roles in many pathophysiologic processes. Rafts have been strongly implicated as master regulators of signal transduction in cancer, where raft compartmentalization can promote transmembrane receptor oligomerization, shield proteins from enzymatic degradation, and act as scaffolds to enhance intracellular signaling cascades. Cancer cells have been found to exploit these mechanisms to initiate oncogenic signaling and promote tumor progression. This review highlights the roles of lipid rafts within the metastatic cascade, specifically within tumor angiogenesis, cell adhesion, migration, epithelial-to-mesenchymal transition, and transendothelial migration. In addition, the interplay between lipid rafts and different modes of cancer cell death, including necrosis, apoptosis, and anoikis, will be described. The clinical role of lipid raft-specific proteins, caveolin and flotillin, in assessing patient prognosis and evaluating metastatic potential of various cancers will be presented. Collectively, elucidation of the complex roles of lipid rafts and raft components within the metastatic cascade may be instrumental for therapeutic discovery to curb prometastatic processes.

Pulsatilla saponin E suppresses viability, migration, invasion and promotes apoptosis of NSCLC cells through negatively regulating Akt/FASN pathway via inhibition of flotillin-2 in lipid raft

PURPOSE

Pulsatilla saponins from pulsatilla chinensis (Bunge) Regel have potential anti-tumor activities to certain human cancers. However, the roles of pulsatilla saponin E separated from pulsatilla saponins in non-small cell lung cancer (NSCLC) have not been reported.

MATERIALS AND METHODS

After treating NSCLC cells by pulsatilla saponin E at different concentrations, cell viability was measured by MTT and CCK-8 assays, and cell migration, invasion and apoptosis were detected by scratch wound-healing, transwell and flow cytometry assays. The contents of free cholesterol (FC) and total cholesterol (TC) were measured by high performance liquid chromatography (HPLC). The expression levels of flotillin-1, flotillin-2, Akt, fatty acid synthase (FASN) were detected by qRT-PCR and Western blot assays.

RESULTS

Pulsatilla saponin E suppressed viability, migration, invasion and promoted apoptosis of NSCLC cells followed by regulation of apoptosis-related proteins, reduced contents of FC and TC, and the expression levels of flotillin-1, flotillin-2, Akt, and FASN in a concentration-dependent manner. However, the inhibitory effects of pulsatilla saponin E on viability, migration, invasion of A549 cells and the expression levels of flotillin-1, flotillin-2, Akt, and FASN were reversed by flotillin-2 overexpression.

CONCLUSIONS

Our study revealed that pulsatilla saponin E suppressed migration, invasion and promoted apoptosis of NSCLC cells through negatively regulating Akt/FASN signaling pathway via the inhibition of flotillin-2 in lipid raft (LR). The current findings could be explored for developing a novel therapeutic drug for NSCLC treatment.

Advances in targeted therapy mainly based on signal pathways for nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is a malignant epithelial carcinoma of the head and neck region which mainly distributes in southern China and Southeast Asia and has a crucial association with the Epstein-Barr virus. Based on epidemiological data, both incidence and mortality of NPC have significantly declined in recent decades grounded on the improvement of living standard and medical level in an endemic region, in particular, with the clinical use of individualized chemotherapy and intensity-modulated radiotherapy (IMRT) which profoundly contributes to the cure rate of NPC patients. To tackle the challenges including local recurrence and distant metastasis in the current NPC treatment, we discussed the implication of using targeted therapy against critical molecules in various signal pathways, and how they synergize with chemoradiotherapy in the NPC treatment. Combination treatment including targeted therapy and IMRT or concurrent chemoradiotherapy is presumably to be future options, which may reduce radiation or chemotherapy toxicities and open new avenues for the improvement of the expected functional outcome for patients with advanced NPC.

TPGS2k-PLGA composite nanoparticles by depleting lipid rafts in colon cancer cells for overcoming drug resistance

Recently, studies showed that the drug-resistant cell membranes have formed high-density lipid rafts regions; traditional targeted drug delivery systems can hardly break through the hard shell and deliver drugs to drug-resistant cells. Here, α-tocopherol polyethylene glycol 2000 succinate (TPGS_2k) was successfully synthesized and used to modify poly (lactic-glycolic acid) nanoparticles co-loaded with doxorubicin (DOX) and simvastatin (SV) (SV/DOX@TPGS_2k-PLGA NPs). The purpose of this study is to explore the synergistic effect between SV consuming cholesterol in lipid rafts and directly down-regulating P-gp expression on the intracellular drugs retention. The research highlights these nanoparticles interrupted lipid rafts (cholesterol-rich domains, where P-gp is often located), which inhibited drug efflux by down-regulating P-gp, promoted the mitochondria apoptosis and made SW620/AD300 cells (DOX-resistant colon cancer cell line) re-sensitized to DOX. Therefore, the carrier can become a promising SV-based nano-delivery system with depleting cholesterol in lipid rafts to reverse drug resistance.

miR‑320‑3p is involved in morphine pre‑conditioning to protect rat cardiomyocytes from ischemia/reperfusion injury through targeting Akt3

Morphine pre-conditioning (MPC) can significantly reduce myocardial ischemic injury and inhibit cardiomyocyte apoptosis, but the underlying mechanism still remains unclear. The aim of the present study was to investigate the protective mechanism of MPC in myocardial hypoxia/reoxygenation (H/R) injury at the microRNA (miR) level. H9c2 cells were used as a model of H/R and subjected to morphine pre-treatment. The protective effects of MPC on H/R injury in cardiomyocytes were evaluated using MTT and colorimetric assay, as well as flow cytometry. In addition, reverse transcription-quantitative PCR, western blotting and dual-luciferase reporter assay experiments were performed to determine the relationship between MPC, miR-320-3p and Akt3, and their effects on H/R injury. The present study demonstrated that MPC enhanced cell activity, decreased LDH content, and reduced apoptosis in rat cardiomyocytes, suggesting that MPC could protect these cells from H/R injury. Moreover, MPC partially reversed the increase in miR-320-3p expression and the decrease in Akt3 levels caused by H/R injury. Inhibition of miR-320-3p expression also attenuated the effects of H/R on cardiomyocyte activity, LDH content and apoptosis. Furthermore, Akt3 was predicted to be a target gene of miR-320-3p, and overexpression of miR-320-3p inhibited the expression of Akt3, blocking the protective effects of MPC on the cells. The current findings revealed that MPC could protect cardiomyocytes from H/R damage through targeting miR-320-3p to regulate the PI3K/Akt3 signaling pathway.

Flotillins: At the Intersection of Protein S-Palmitoylation and Lipid-Mediated Signaling

Flotillin-1 and flotillin-2 are ubiquitously expressed, membrane-associated proteins involved in multifarious cellular events from cell signaling, endocytosis, and protein trafficking to gene expression. They also contribute to oncogenic signaling. Flotillins bind the cytosolic leaflet of the plasma membrane and endomembranes and, upon hetero-oligomerization, serve as scaffolds facilitating the assembly of multiprotein complexes at the membrane-cytosol interface. Additional functions unique to flotillin-1 have been discovered recently. The membrane-binding of flotillins is regulated by S-palmitoylation and N-myristoylation, hydrophobic interactions involving specific regions of the polypeptide chain and, to some extent, also by their oligomerization. All these factors endow flotillins with an ability to associate with the sphingolipid/cholesterol-rich plasma membrane domains called rafts. In this review, we focus on the critical input of lipids to the regulation of the flotillin association with rafts and thereby to their functioning. In particular, we discuss how the recent developments in the field of protein S-palmitoylation have contributed to the understanding of flotillin1/2-mediated processes, including endocytosis, and of those dependent exclusively on flotillin-1. We also emphasize that flotillins affect directly or indirectly the cellular levels of lipids involved in diverse signaling cascades, including sphingosine-1-phosphate and PI(4,5)P₂. The mutual relations between flotillins and distinct lipids are key to the regulation of their involvement in numerous cellular processes.

Flotillin-2 predicts poor prognosis and promotes tumor invasion in intrahepatic cholangiocarcinoma

Intrahepatic cholangiocarcinoma (iCCA) is a highly malignant neoplasm arising from the intrahepatic bile ducts. As a scaffold protein of lipid rafts, flotillin-2 is upregulated in several types of cancer and promotes tumor progression and metastasis. To the best of our knowledge, the present study was the first to detect the upregulation of flotillin-2 in iCCA tissues compared with matched adjacent non-tumor tissues. In addition, immunohistochemistry was used to investigate the expression of flotillin-2 in a microarray consisting of 92 iCCA tissues. A total of 59 samples (64.1%) exhibited high flotillin-2 expression, which was significantly related to lymph node metastasis (P=0.029) and tumor-node-metastasis stage (P=0.016). Further in vitro study demonstrated that knockdown of flotillin-2 inhibited the invasive capability of iCCA cell lines, further supporting the participation of flotillin-2 in cancer invasion and metastasis. Moreover, Kaplan-Meier analysis showed patients with high flotillin-2 expression had worse overall survival outcomes. The multivariate Cox proportional hazards model further revealed that high flotillin-2 expression was an independent indicator (P=0.005) of poor prognosis for patients with iCCA. Collectively, the present study revealed that as a promoter of invasion and an independent marker of poor prognosis, flotillin-2 may serve as a potential target for the development of novel therapeutic agents for iCCA.

ATG3, a Target of miR-431-5p, Promotes Proliferation and Invasion of Colon Cancer via Promoting Autophagy

Background

Studies have indicated that ATG3 could mediate the effects of other tumor-related regulators in carcinogenesis. However, the expression, role, and mechanism of ATG3 itself in cancers are rarely revealed. Thus, we explored the expression, function, and mechanism of ATG3 in colon cancer.

Materials and methods

The expression of ATG3 was detected in colon cancer tissues and cell lines, as well as in adjacent tumor tissues and normal colon epithelial cells. The effects of ATG3 alteration on proliferation and invasion were further analyzed. The expression and role of miR-431-5p, a potential negative regulator of ATG3, were also studied. Eventually, the role of autophagy in ATG3 related effects in colon cancer was checked.

Results

ATG3 is upregulated in colon cancer tissues and cells demonstrated by qPCR and IHC. ATG3 knockdown significantly suppressed proliferation and invasion of colon cancer cells indicated by plate clone formation and Transwell invasion assays. The expression of miR-431-5p is downregulated and negatively correlates with ATG3 in colon cancer. Furthermore, luciferase report system, plate clone formation and Transwell invasion assays demonstrated that miR-431-5p could prohibit cell proliferation and invasion via directly targeting ATG3 in colon cancer. Eventually, Western blot, plate clone formation and Transwell invasion assays proved that autophagy block could antagonize the promotive functions of ATG3 on proliferation and invasion in cancer suggesting autophagy activation accounts for the promotive role of ATG3 on proliferation and invasion in colon cancer.

Conclusion

Collectively, ATG3 upregulation, caused by downregulated miR-435-5p, promotes proliferation and invasion via an autophagy-dependent manner in colon cancer suggesting that miR-431-5p/ATG3/autophagy may be a potential therapeutic target in colon cancer.

Inhibition of the key metabolic pathways, glycolysis and lipogenesis, of oral cancer by bitter melon extract

BACKGROUND

Metabolic reprogramming is one of the hallmarks of cancer which favours rapid energy production, biosynthetic capabilities and therapy resistance. In our previous study, we showed bitter melon extract (BME) prevents carcinogen induced mouse oral cancer. RNA sequence analysis from mouse tongue revealed a significant modulation in "Metabolic Process" by altering glycolysis and lipid metabolic pathways in BME fed group as compared to cancer group. In present study, we evaluated the effect of BME on glycolysis and lipid metabolism pathways in human oral cancer cells.

METHODS

Cal27 and JHU022 cells were treated with BME. RNA and protein expression were analysed for modulation of glycolytic and lipogenesis genes by quantitative real-time PCR, western blot analyses and immunofluorescence. Lactate and pyruvate level was determined by GC/MS. Extracellular acidification and glycolytic rate were measured using the Seahorse XF analyser. Shotgun lipidomics in Cal27 and JHU022 cell lines following BME treatment was performed by ESI/ MS. ROS was measured by FACS.

RESULTS

Treatment with BME on oral cancer cell lines significantly reduced mRNA and protein expression levels of key glycolytic genes SLC2A1 (GLUT-1), PFKP, LDHA, PKM and PDK3. Pyruvate and lactate levels and glycolysis rate were reduced in oral cancer cells following BME treatment. In lipogenesis pathway, we observed a significant reduction of genes involves in fatty acid biogenesis, ACLY, ACC1 and FASN, at the mRNA and protein levels following BME treatment. Further, BME treatment significantly reduced phosphatidylcholine, phosphatidylethanolamine, and plasmenylethanolamine, and reduced iPLA2 activity. Additionally, BME treatment inhibited lipid raft marker flotillin expression and altered its subcellular localization. ER-stress associated CHOP expression and generation of mitochondrial reactive oxygen species were induced by BME, which facilitated apoptosis.

CONCLUSION

Our study revealed that bitter melon extract inhibits glycolysis and lipid metabolism and induces ER and oxidative stress-mediated cell death in oral cancer. Thus, BME-mediated metabolic reprogramming of oral cancer cells will have important preventive and therapeutic implications along with conventional therapies.

MicroRNA-485-5p suppresses the proliferation, migration and invasion of small cell lung cancer cells by targeting flotillin-2

This study is aimed to elucidate the mechanisms underlying the role of miR-485-5p in small cell lung cancer (SCLC). The expression of miR-485-5p were quantified with real time quantitative PCR and it was found that the level of miR-485-5p was lower in SCLC tissues than normal tissues. In cultured SCLC cell lines, overexpression of miR-485-5p reduced cell proliferation, migration, and invasion in vitro, whereas knockdown of miR-485-5p performed contrary. FLOT2 expression was obviously upregulated and negatively correlated with miR-485-5p expression level in SCLC tissues. Overexpression of miR-485-5p significantly inhibited the protein expression of flotillin-2 (FLOT2) in cultured SCLC cells. Luciferase reporter assay confirmed that FLOT2 was a direct target of miR-485-5p in SCLC cells. It is concluded that miR-485-5p, as a tumor suppressor, inhibits the growth and metastasis in SCLC by targeting FLOT2. Upregulation of miR-485-5p expression may be an attractive strategy for SCLC therapy.

Downregulated miR-585-3p promotes cell growth and proliferation in colon cancer by upregulating PSME3

Background

Upregulation of PSME3 and its oncogenic roles have been reported in colon cancer recently. However, the underlying mechanism of PSME3 upregulation remains unknown. Here, we explored the expression of PSME3 and subsequently uncovered its mechanism in colon cancer.

Materials and methods

The expression of PSME3 was analyzed by using online databases, Oncomine and UALCAN. qPCR was carried out to detect the expression of PSME3 in collected colon cancer tissues and cell lines. Moreover, the promoter methylation and the hnRNA level of PSME3 were also analyzed by online database and qPCR, respectively. The candidate miRNAs targeting PSME3 were predicted by Starbase 3.0 and validated by luciferase reporter system. CCK-8, plate colon formation, and Edu incorporation were applied to study the functions of miRNA in colon cancer. The expression of miRNA and its correlation with PSME3 were detected in colon cancer tissues.

Results

Oncomine and UALCAN data indicate PSME3 is obviously upregulated in colon cancer tissue samples which is further confirmed in collected colon cancer tissues and cells by qPCR. No significant difference in methylation status promoter of PSME3 was observed between colon and colon cancer tissues. The hnRNA level of PSME3 was comparable between colon epithelial cell and colon cancer cells. miR-585-3p is predicted to directly target PSME3 and is validated by luciferase reporter assay. Then, miR-585-3p downregulation is confirmed and miR-585-3p restoration can suppress cell growth and proliferation by inhibiting PSME3 in colon cancer indicating by CCK-8, plate colon formation, and Edu incorporation. Moreover, negative correlation in expression between miR-585-3p and PSME3 was observed in our collected tissues samples.

Conclusion

We reveal for the first time that miR-585-3p downregulation accounts for the overexpression of PSME3 in colon cancer. Moreover, miR-585-3p, serving as a tumor suppressor, can inhibit cell growth and proliferation in colon cancer by targeting PSME3.

MicroRNA-351 eases insulin resistance and liver gluconeogenesis via the PI3K/AKT pathway by inhibiting FLOT2 in mice of gestational diabetes mellitus

Gestational diabetes mellitus (GDM) is known as different degree glucose intolerance that is initially identified during pregnancy. MicroRNAs (miRs) may be a potential candidate for treatment of GDM. Herein, we suggested that miR‐351 could be an inhibitor in the progression of GDM via the phosphoinositide 3‐kinase/protein kinase B (PI3K/AKT) pathway. Microarray analysis was used to identify differentially expressed genes and predict miRs regulating flotillin 2 (FLOT2). Target relationship between miR‐351 and FLOT2 was verified. Gestational diabetes mellitus mice were treated with a series of mimic, inhibitor and small interfering RNA to explore the effect of miR‐351 on insulin resistance (IR), cell apoptosis in pancreatic tissues and liver gluconeogenesis through evaluating GDM‐related biochemical indexes, as well as expression of miR‐351, FLOT2, PI3K/AKT pathway‐, IR‐ and liver gluconeogenesis‐related genes. MiR‐351 and FLOT2 were reported to be involved in GDM. FLOT2 was the target gene of miR‐351. Gestational diabetes mellitus mice exhibited IR and liver gluconeogenesis, up‐regulated FLOT2, activated PI3K/AKT pathway and down‐regulated miR‐351 in liver tissues. Additionally, miR‐351 overexpression and FLOT2 silencing decreased the levels of FLOT2, phosphoenolpyruvate carboxykinase, glucose‐6‐phosphatase, fasting blood glucose, fasting insulin, total cholesterol, triglyceride, glyeosylated haemoglobin and homeostasis model of assessment for IR index (HOMA‐IR), extent of PI3K and AKT phosphorylation, yet increased the levels of HOMA for islet β‐cell function, HOMA for insulin sensitivity index and glucose transporter 2 expression, indicating reduced cell apoptosis in pancreatic tissues and alleviated IR and liver gluconeogenesis. Our results reveal that up‐regulation of miR‐351 protects against IR and liver gluconeogenesis by repressing the PI3K/AKT pathway through regulating FLOT2 in GDM mice, which identifies miR‐351 as a potential therapeutic target for the clinical management of GDM.

MSI2-TGF-β/TGF-β R1/SMAD3 positive feedback regulation in glioblastoma

PURPOSE

Glioblastoma is the most malignant glioma tumors with inevitable relapse and resistance to chemotherapy; however, the mechanisms driving chemoresistance remain to be fully elucidated. This study is to explore the molecular and cellular mechanisms involving in the chemoresistance of glioblastoma.

METHODS

The expression of musashi (MSI) RNA-binding protein in the tumor tissues and cells of glioblastoma was measured. The effects of MSI2 in epithelial-to-mesenchymal transition (EMT), resistance to temozolomide (TMZ), tumor cell invasion, migration, and proliferation and associated signaling were evaluated.

RESULTS

High MSI2 expression was observed in the glioblastoma tissues. Silencing or overexpression of MSI2 significantly affected tumor cells invasion, migration, and proliferation. Silencing of MSI2 expression significantly inhibited O₆-methylguanine-DNA methyltransferase (MGMT) expression and tumor growth, and reversed resistance to TMZ in xenograft tumor models. MSI2 expression regulated EMT through activating the transcription factors Snail and the TGFβ R1/SMAD3 signaling.

CONCLUSIONS

Our study demonstrated a positive feedback loop of MSI2-TGFβ/SMAD3 signaling which activates the EMT and MGMT which may contribute to chemoresistance in glioblastoma. This study also highlights that MSI2 could be a new target for the therapy of glioblastoma.

Akt-ing Up Just About Everywhere: Compartment-Specific Akt Activation and Function in Receptor Tyrosine Kinase Signaling

The serine/threonine kinase Akt is a master regulator of many diverse cellular functions, including survival, growth, metabolism, migration, and differentiation. Receptor tyrosine kinases are critical regulators of Akt, as a result of activation of phosphatidylinositol-3-kinase (PI3K) signaling leading to Akt activation upon receptor stimulation. The signaling axis formed by receptor tyrosine kinases, PI3K and Akt, as well as the vast range of downstream substrates is thus central to control of cell physiology in many different contexts and tissues. This axis must be tightly regulated, as disruption of PI3K-Akt signaling underlies the pathology of many diseases such as cancer and diabetes. This sophisticated regulation of PI3K-Akt signaling is due in part to the spatial and temporal compartmentalization of Akt activation and function, including in specific nanoscale domains of the plasma membrane as well as in specific intracellular membrane compartments. Here, we review the evidence for localized activation of PI3K-Akt signaling by receptor tyrosine kinases in various specific cellular compartments, as well as that of compartment-specific functions of Akt leading to control of several fundamental cellular processes. This spatial and temporal control of Akt activation and function occurs by a large number of parallel molecular mechanisms that are central to regulation of cell physiology.

Sodium butyrate induces autophagic apoptosis of nasopharyngeal carcinoma cells by inhibiting AKT/mTOR signaling

Previously, we confirmed the anti-tumor effects of sodium butyrate (NaBu) in nasopharyngeal carcinoma (NPC). However, its molecular mechanisms have not be fully elucidated. In this study, we studied the effects of NaBu on autophagy and explored the relation between NaBu associated autophagy and apoptosis in NPC cells. EGFP-LC3 plasmids were introduced into NPC cells to observed the effects of NaBu on autophagy flux with or without chloroquine (CQ) addition. Autophagy markers were also detected by Western blot. Under NaBu treatment, autophagy and apoptosis markers were detected simultaneously at different time. Then, to explore the roles of autophagy in NaBu induced apoptosis, the effects of autophagy inhibition, via specific inhibitor treatment or key gene knockdown, were analyzed. At last, the upstream signaling and its roles in NaBu induced autophagy and apoptosis were also analyzed. Increased LC3 dots and LC3-II accumulation indicated that NaBu can promote autophagy flux in NPC cells. LC3-II accumulation was earlier than cleaved PARP increment suggesting autophagy activation is prior to apoptosis activation, which was validated by flow cytometry mediated apoptosis analysis. Moreover, autophagy inhibition, achieved by 3-MA treatment or BECN1 knockdown, can antagonize NaBu induced apoptosis reflecting by re-deregulated cPARP and apoptotic rates. Furthermore, NaBu treatment inhibited the AKT/mTOR axis indicated by deregulated p-AKT(S473) and p-mTOR(S2448) and ectopic AKT expression both suppressed NaBu induced autophagy and apoptosis. At last, Western blot showed that HDAC6 dependent EGFR deregulation may account for the NaBu associated AKT/mTOR inhibition. NaBu can induce autophagic apoptosis via suppressing AKT/mTOR axis in NPC cells. Our results suggest that combination of autophagy inhibitors and deacetylase inhibitors may not be recommended in NPC clinical treatment.

Insufficient radiofrequency ablation promotes the metastasis of residual hepatocellular carcinoma cells via upregulating flotillin proteins

Purpose

Radiofrequency ablation (RFA) therapy has proven to be effective and feasible for early-stage hepatocellular carcinoma (HCC); however, rapid progression of residual tumor cells after RFA has been confirmed, but the molecular mechanisms of this phenomenon are poorly understood. This study evaluated the effect of the lipid raft proteins known as flotillins on the invasive and metastatic potential of residual HCC.

Methods

The human HCC cell line HCCLM3 was used to establish insufficient RFA models in vivo and in vitro. Changes in cellular morphology, soft agar colony formation, motility, metastasis, and epithelial–mesenchymal transition (EMT) markers after insufficient RFA intervention in vitro and in vivo were detected by real-time PCR, western blotting, immunohistochemistry and transwell assays.

Results

The results showed that flotillin-1 and flotillin-2 expression were upregulated in HCCLM3 cells following 45 °C heat treatment and in residual HCCLM3 xenografts cells after insufficient RFA. Knocking down flotillin-1 or flotillin-2 in HCCLM3 cells by shRNA significantly lowered insufficient RFA-induced tumor growth, EMT changes, and metastasis in vitro and in vivo. Furthermore, mechanism studies indicated that flotillins altered the EMT status and metastatic potential of heat-treated HCCLM3 cells by activating the Akt/Wnt/β-catenin signaling pathway.

Conclusions

Our findings present new evidence that flotillins play a key role in the aggressive behaviors of residual cancer cells after insufficient RFA and provide new insights into the regulatory mechanism of Wnt/β-catenin signaling.

Electronic supplementary material

The online version of this article (10.1007/s00432-019-02852-z) contains supplementary material, which is available to authorized users.

Genome-wide DNA methylation profiles in Tibetan and Yorkshire pigs under high-altitude hypoxia

Background

Tibetan pigs, which inhabit the Tibetan Plateau, exhibit distinct phenotypic and physiological characteristics from those of lowland pigs and have adapted well to the extreme conditions at high altitude. However, the genetic and epigenetic mechanisms of hypoxic adaptation in animals remain unclear.

Methods

Whole-genome DNA methylation data were generated for heart tissues of Tibetan pigs grown in the highland (TH, n = 4) and lowland (TL, n = 4), as well as Yorkshire pigs grown in the highland (YH, n = 4) and lowland (YL, n = 4), using methylated DNA immunoprecipitation sequencing.

Results

We obtained 480 million reads and detected 280679, 287224, 259066, and 332078 methylation enrichment peaks in TH, YH, TL, and YL, respectively. Pairwise TH vs. YH, TL vs. YL, TH vs. TL, and YH vs. YL comparisons revealed 6829, 11997, 2828, and 1286 differentially methylated regions (DMRs), respectively. These DMRs contained 384, 619, 192, and 92 differentially methylated genes (DMGs), respectively. DMGs that were enriched in the hypoxia-inducible factor 1 signaling pathway and pathways involved in cancer and hypoxia-related processes were considered to be important candidate genes for high-altitude adaptation in Tibetan pigs.

Conclusions

This study elucidates the molecular and epigenetic mechanisms involved in hypoxic adaptation in pigs and may help further understand human hypoxia-related diseases.

Flotillins in the intercalated disc are potential modulators of cardiac excitability

BACKGROUND

The intercalated disc (ID) is important for cardiac remodeling and has become a subject of intensive research efforts. However, as yet the composition of the ID has still not been conclusively resolved and the role of many proteins identified in the ID, like Flotillin-2, is often unknown. The Flotillin proteins are known to be involved in the stabilization of cadherins and desmosomes in the epidermis and upon cancer development. However, their role in the heart has so far not been investigated. Therefore, in this study, we aimed at identifying the role of Flotillin-1 and Flotillin-2 in the cardiac ID.

METHODS

Location of Flotillins in human and murine cardiac tissue was evaluated by fluorescent immunolabeling and co-immunoprecipitation. In addition, the effect of Flotillin knockout (KO) on proteins of the ID and in electrical excitation and conduction was investigated in cardiac samples of wildtype (WT), Flotillin-1 KO, Flotilin-2 KO and Flotilin-1/2 double KO mice. Consequences of Flotillin knockdown (KD) on cardiac function were studied (patch clamp and Multi Electrode Array (MEA)) in neonatal rat cardiomyocytes (NRCMs) transfected with siRNAs against Flotillin-1 and/or Flotillin-2.

RESULTS

First, we confirmed presence in the ID and mutual binding of Flotillin-1 and Flotillin-2 in murine and human cardiac tissue. Flotillin KO mice did not show cardiac fibrosis, nor hypertrophy or changes in expression of the desmosomal ID proteins. However, protein expression of the cardiac sodium channel Na_V1.5 was significantly decreased in Flotillin-1 and Flotillin-1/2 KO mice compared to WT mice. In addition, sodium current density showed a significant decrease upon Flotillin-1/2 KD in NRCMs as compared to scrambled siRNA-transfected NRCMs. MEA recordings of Flotillin-2 KD NRCM cultures showed a significantly decreased spike amplitude and a tendency of a reduced spike slope when compared to control and scrambled siRNA-transfected cultures.

CONCLUSIONS

In this study, we demonstrate the presence of Flotillin-1, in addition to Flotillin-2 in the cardiac ID. Our findings indicate a modulatory role of Flotillins on Na_V1.5 expression at the ID, with potential consequences for cardiac excitation.

Roles of flotillins in tumors

The identification and use of molecular biomarkers have greatly improved the diagnosis and treatment of malignant tumors. However, a much deeper understanding of oncogenic proteins is needed for the benefit to cancer patients. The lipid raft marker proteins, flotillin-1 and flotillin-2, were first found in goldfish retinal ganglion cells during axon regeneration. They have since been found in a variety of cells, mainly on the inner surface of cell membranes, and not only act as a skeleton to provide a platform for protein-protein interactions, but also are involved in signal transduction, nerve regeneration, endocytosis, and lymphocyte activation. Previous studies have shown that flotillins are closely associated with tumor development, invasion, and metastasis. In this article, we review the functions of flotillins in relevant cell processes, their underlying mechanisms of action in a variety of tumors, and their potential applications to tumor molecular diagnosis and targeted therapy.

MT1-MMP targeting to endolysosomes is mediated by upregulation of flotillins

Tumor cell invasion and metastasis formation are the major cause of death in cancer patients. These processes rely on extracellular matrix (ECM) degradation mediated by organelles termed invadopodia, to which the transmembrane matrix metalloproteinase MT1-MMP (also known as MMP14) is delivered from its reservoir, the RAB7-containing endolysosomes. How MT1-MMP is targeted to endolysosomes remains to be elucidated. Flotillin-1 and -2 are upregulated in many invasive cancers. Here, we show that flotillin upregulation triggers a general mechanism, common to carcinoma and sarcoma, which promotes RAB5-dependent MT1-MMP endocytosis and its delivery to RAB7-positive endolysosomal reservoirs. Conversely, flotillin knockdown in invasive cancer cells greatly reduces MT1-MMP accumulation in endolysosomes, its subsequent exocytosis at invadopodia, ECM degradation and cell invasion. Our results demonstrate that flotillin upregulation is necessary and sufficient to promote epithelial and mesenchymal cancer cell invasion and ECM degradation by controlling MT1-MMP endocytosis and delivery to the endolysosomal recycling compartment.

CD109 is identified as a potential nasopharyngeal carcinoma biomarker using aptamer selected by cell-SELEX

Nasopharyngeal carcinoma (NPC) is one of the most prevailing cancers in southern China and southern Asia. Because of the nonspecific symptoms and lack of effective biomarker, most patients are diagnosed at advanced stages, resulting in poor 5-year survival rate. To identify a novel NPC biomarker facilitating early detection and effective therapy of NPC, a two-step strategy consisting of cancer cell-Systematic Evolution of Ligands by EXponential enrichment (cell-SELEX) procedure and aptamer-based purification approach was developed. Using cell-SELEX procedure, four aptamers (S3, S5, S12 and S27) differentiating the molecular differences between NPC cells and NP cells were successfully screened. Then, using aptamer-based protein purification, membrane protein CD109 was identified as the target of aptamer S3. CD109 protein was further identified to be over-expressed in NPC cell lines and clinic tissues, but not or low in NP cell line and clinic NP tissues, detected by western blot and immunohistochemistry experiments. Our study demonstrated that CD109 identified by cell-SELEX and aptamer-based purification strategy might be used as a potential NPC biomarker for early diagnosis and targeted therapy.

Identification of nasopharyngeal carcinoma metastasis-related biomarkers by iTRAQ combined with 2D-LC-MS/MS

To identify metastasis-related proteins in nasopharyngeal carcinoma (NPC), iTRAQ-tagging combined with 2D LC-MS/MS analysis was performed to identify the differentially expressed proteins (DEPs) in high metastatic NPC 5-8F cells and non-metastatic NPC 6-10B cells, and qRT-PCR and Western blotting were used to confirm DEPs. As a result, 101 DEPs were identified by proteomics, and 12 DEPs were selectively validated. We further detected expression of three DEPs (RAN, SQSTM1 and TRIM29) in a cohort of NPC tissue specimens to assess their value as NPC metastatic biomarkers, and found that combination of RAN, SQSTM1 and TRIM29 could discriminate metastatic NPC from non-metastatic NPC with a sensitivity of 88% and a specificity of 91%. TRIM29 and RAN expression level were closely correlated with lymph node and distant metastasis and clinical stage (P <0.05) in NPC patients. Finally, a combination of loss-of-function and gain-of-function approaches was performed to determine the effects of TRIM29 on NPC cell proliferation, migration, invasion and metastasis. The results showed that TRIM29 knockdown significantly attenuated while TRIM29 overexpression promoted NPC cell in vitro proliferation, migration and invasion and in vivo metastasis. The present data first time show that SQSTM1, RAN and TRIM29 are novel potential biomarkers for predicting NPC metastasis, demonstrate that TRIM29 is a metastasis-promoted protein of NPC.

PLCD3, a flotillin2-interacting protein, is involved in proliferation, migration and invasion of nasopharyngeal carcinoma cells

Phospholipase C (PLC) is a pivotal enzyme in the phosphoinositide pathway that promotes the second messengers, diacylglycerol (DAG) and inositol 1,4,5-trisphosphate (IP3), to participate in eukaryotic signal transduction. Several PLC isozymes are associated with cancer, such as PLC-β1, PLC-δ1, PLC-ε and PLC-γ1. However, the role of PLC-δ3 (PLCD3) in nasopharyngeal carcinoma (NPC) has not been investigated to date. In our previous study, we demonstrated that flotillin2 (Flot2) plays a pro-neoplastic role in NPC and is involved in tumour progression and metastasis. In the present study, we screened the interacting proteins of Flot2 using the yeast two-hybrid (Y2H) method and verified the interaction between PLCD3 and Flot2 by co-immunoprecipitation. We also investigated the biological functions of PLCD3 in NPC. Inhibition of PLCD3 expression impaired the malignant potential of 5–8F, a highly metastatic NPC cell line, by restraining its growth, proliferation, mobility and migration. The present study demonstrated that PLCD3 may be an oncogenic protein in NPC and that it plays an important role in the progression of NPC partially by interacting with Flot2.

Flot2 promotes tumor growth and metastasis through modulating cell cycle and inducing epithelial-mesenchymal transition of hepatocellular carcinoma

Flotillin-2 (Flot2) is a highly conserved and ubiquitously expressed protein that resides on the cytoplasmic side of the cell membrane within specific cholesterol rich microdomains. Some studies have reported that overexpression of Flot2 is related to cancer progression. However, the role of Flot2 in hepatocellular carcinoma (HCC) remains unclarified. In this study, we aim to explore the correlation between Flot2 expression and HCC progression and the underlying mechanism. In the present study, overexpression of Flot2 in HCC tissues and cell lines was detected, and forced overexpression of Flot2 significantly promoted the proliferation, migration, invasion and metastasis of HCC in vitro and in vivo by modulating cell cycle and inducing EMT, which was mediated via up-regulation of Twist as a result of Raf/MEK/ERK1/2 pathway activation. In contrast, silencing Flot2 expression inhibited these biological processes. Furthermore, high expression of Flot2 was significantly correlated with poor prognosis of HCC patients after curative resection and is an independent risk factor. In conclusion, Flot2 promoted tumor growth and metastasis of HCC through modulating cell cycle and inducing EMT. The expression of Flot2 may play a key role in HCC progression and may be regarded as a potential poor prognostic marker for HCC.

MiR-20b targets AKT3 and modulates vascular endothelial growth factor-mediated changes in diabetic retinopathy

Diabetic retinopathy (DR) is the leading cause of new-onset blindness. The roles of microRNAs in diabetic retinopathy are largely unknown. The aim of this study is to investigate the role of miR-20b in DR. Transfection of miR-20b mimic in high glucose (HG)-treated human retinal endothelial cells (HRECs) increased miR-20b expression and decreased the expression level of VEGF mRNA, while transfection of miR-20b inhibitor in control HRECs reduced the miR-20b expression with a corresponding increase of VEGF mRNA. In vitro functional assay showed that transfection of miR-20b mimic prevented HG-induced increase in transendothelial permeability and tube formation in HRECs. Transfection of miR-20b inhibitor or treatment of VEGF increased transendothelial permeability and tube formation in control HRECs. Luciferase reported assay showed that AKT3 is a target of miR-20b. Transfection of miR-20b mimic prevented the up-regulation of AKT3 induced by HG without changing the protein levels of other isoforms of AKT, and silencing of AKT3 caused decrease of VEGF mRNA and protein levels as well as prevented HG-induced increase in transendothelial permeability and tube formation. Finally, we showed that miR-20b was down-regulated in the retina and retinal endothelial cells in diabetic rats, with a correlated up-regulation of VEGF and AKT3. Intravitreal injection of miR-20b mimic in the diabetic rat significantly increased the miR-20b expression and decreased the expression levels of AKT3 and VEGF in the retina tissues, and intravitreal delivery of AKT3 siRNA in the diabetic rat significantly decreased the expressions of AKT3 and VEGF. Collectively, miR-20b is important for the regulation of VEGF-mediated changes in HRECs and rat retinal tissues under hyperglycemic conditions possibly via targeting AKT3.