MATR3-antisense LINE1 RNA meshwork scaffolds higher-order chromatin organization.

Long interspersed nuclear elements (LINEs) play essential roles in shaping chromatin states, while the factors that cooperate with LINEs and their roles in higher-order chromatin organization remain poorly understood. Here, we show that MATR3, a nuclear matrix protein, interplays with antisense LINE1 (AS L1) RNAs to form a meshwork via phase separation, providing a dynamic platform for chromatin spatial organization. MATR3 and AS L1 RNAs affect the nuclear localization of each other. After MATR3 depletion, the chromatin, particularly H3K27me3-modified chromatin, redistributes in the cell nuclei. Topologically associating domains (TADs) that highly transcribe MATR3-associated AS L1 RNAs show decreased intra-TAD interactions in both AML12 and ES cells. MATR3 depletion increases the accessibility of H3K27me3 domains adjacent to MATR3-associated AS L1, without affecting H3K27me3 modifications. Furthermore, amyotrophic lateral sclerosis (ALS)-associated MATR3 mutants alter biophysical features of the MATR3-AS L1 RNA meshwork and cause an abnormal H3K27me3 staining. Collectively, we reveal a role of the meshwork formed by MATR3 and AS L1 RNAs in gathering chromatin in the nucleus.

The efficacy of concurrent weekly carboplatin with radiotherapy in the treatment of cervical cancer: A meta-analysis.

OBJECTIVES: We aimed to evaluate whether carboplatin has a comparable efficacy with cisplatin as part of weekly concurrent chemoradiotherapy for cervical cancer (Car-RT vs. Cis-RT). METHODS: A literature search was conducted and both prospective and retrospective studies that evaluated the efficacy of Car-RT for cervical cancer were included. The primary endpoints were complete response (CR) rate, progression-free survival (PFS)/disease-free survival (DFS), overall survival (OS), reported as odds ratios (ORs) and 95% confidence intervals (CIs). The estimated CR rate and survival of patients treated with Car-RT were pooled. Acute toxicity was also summarized. RESULTS: Twelve studies consisting of 1698 patients were eligible for meta-analysis. A lower CR rate (OR, 0.53; 95% CI, 0.34-0.82, I2 = 0%) and a trend toward poorer 3-year PFS/DFS (OR, 0.71; 95% CI, 0.49-1.02, I2 = 0%) and 3-year OS (OR, 0.70; 95% CI, 0.46-1.05, I2 = 36%) were found in Car-RT compared with Cis-RT. For the Car-RT groups, the pooled overall CR rate was 81% (95% CI 0.74-0.89). The pooled 3-year PFS/DFS rate was 64% (95% CI 0.52-0.78). The pooled 3-year OS rate was 73% (95% CI 0.62-0.87). Acute toxic events ≥ grade 3 were infrequent in the Car-RT groups. CONCLUSIONS: Car-RT showed a poorer tumor response and a trend toward inferior survival compared with Cis-RT in the treatment of cervical cancer. However, this evidence was limited by the imbalance among studies. Due to the encouraging efficacy and low toxicity, carboplatin is a suitable concurrent agent for patients with contraindications to cisplatin.

CDK4 as a Prognostic Marker of Hepatocellular Carcinoma and CDK4 Inhibitors as Potential Therapeutics.

BACKGROUND: The proteins CDK4 and CDK6, which are extremely homologous, control cell cycle entry. For the treatment of breast tumors that include hormone receptors, CDK4 and CDK6 inhibitors have been authorized. The link between CDK4 and liver hepatocellular carcinoma (LIHC), however, has not yet been established. OBJECTIVE: The study aimed to explore the link between CDK4 and LIHC and the effect of CDK4 inhibitors on LIHC. METHOD: In this study, we have evaluated CDK4's prognostic relevance in LIHC using data from The Cancer Genome Atlas (TCGA). The relationship between clinical-pathologic features and CDK4 expression has been evaluated using the Kruskal-Wallis test, the Wilcoxon signed-rank test, and logistic regression. We have analyzed CDK4 and factors related to the prognosis of HCC using the Kaplan-Meier technique and multivariate Cox regression. Gene set enrichment analysis (GSEA) identified CDK4-related critical pathways. To investigate the connections between CDK4 and cancer immune infiltrates, TCGA data were employed in single-sample gene set enrichment analysis (ssGSEA). For functional validation, CDK4 was chosen since it can be inhibited by recognized CDK4/ 6-inhibitors (e.g., abemaciclib). RESULTS: Poorer overall and disease-specific outcomes were linked to high CDK4 expression in HCC patients. GSEA suggested that CDK4 and immune response are closely connected. The amount of Th2 cells infiltrating was positively correlated with CDK4 expression, while the amount of cytotoxic cells infiltrating was negatively correlated, according to ssGSEA. Both in vitro and in vivo, the anti-tumor efficacy of CDK4 inhibitor has been found to be superior to that of sorafenib. CONCLUSION: This study suggests a relationship between CDK4 and immune infiltration and prognosis in HCC. Additionally, a CDK4 inhibitor may have anti-tumor properties against hepatocellular cancer.

Immune depletion of the methylated phenotype of colon cancer is closely related to resistance to immune checkpoint inhibitors.

Background: Molecular typing based on single omics data has its limitations and requires effective integration of multiple omics data for tumor typing of colorectal cancer (CRC). Methods: Transcriptome expression, DNA methylation, somatic mutation, clinicopathological information, and copy number variation were retrieved from TCGA, UCSC Xena, cBioPortal, FireBrowse, or GEO. After pre-processing and calculating the clustering prediction index (CPI) with gap statistics, integrative clustering analysis was conducted via MOVICS. The tumor microenvironment (TME) was deconvolved using several algorithms such as GSVA, MCPcounter, ESTIMATE, and PCA. The metabolism-relevant pathways were extracted through ssGSEA. Differential analysis was based on limma and enrichment analysis was carried out by Enrichr. DNA methylation and transcriptome expression were integrated via ELMER. Finally, nearest template or hemotherapeutic sensitivity prediction was conducted using NTP or pRRophetic. Results: Three molecular subtypes (CS1, CS2, and CS3) were recognized by integrating transcriptome, DNA methylation, and driver mutations. CRC patients in CS3 had the most favorable prognosis. A total of 90 differentially mutated genes among the three CSs were obtained, and CS3 displayed the highest tumor mutation burden (TMB), while significant instability across the entire chromosome was observed in the CS2 group. A total of 30 upregulated mRNAs served as classifiers were identified and the similar diversity in clinical outcomes of CS3 was validated in four external datasets. The heterogeneity in the TME and metabolism-related pathways were also observed in the three CSs. Furthermore, we found CS2 tended to loss methylations while CS3 tended to gain methylations. Univariate and multivariate Cox regression revealed that the subtypes were independent prognostic factors. For the drug sensitivity analysis, we found patients in CS2 were more sensitive to ABT.263, NSC.87877, BIRB.0796, and PAC.1. By Integrating with the DNA mutation and RNA expression in CS3, we identified that SOX9, a specific marker of CS3, was higher in the tumor than tumor adjacent by IHC in the in-house cohort and public cohort. Conclusion: The molecular subtypes based on integrated multi-omics uncovered new insights into the prognosis, mechanisms, and clinical therapeutic targets for CRC.

Transcriptomic Analyses of the Adenoma-Carcinoma Sequence Identify Hallmarks Associated With the Onset of Colorectal Cancer.

The concept of the adenoma-carcinoma sequence in colorectal cancer (CRC) is widely accepted. However, the relationship between the characteristics of the transcriptome and the adenoma-carcinoma sequence in CRC remains unclear. Here, the transcriptome profiles of 15 tissue samples from five CRC patients were generated by RNAseq. Six specific dynamic expression patterns of differentially expressed genes (DEGs) were generated by mFuzz. Weighted correlation network analysis showed that DEGs in cluster 4 were associated with carcinoma tissues, and those in cluster 6 were associated with non-normal tissues. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses identified metabolic dysregulation as a consistent finding throughout the transition process, whereas downregulation of the immune response occurred during normal to adenoma transition, and the upregulation of canonical pathways was associated with adenoma to carcinoma transition. Overall survival analysis of patients in cluster 6 identified TPD52L1 as a marker of poor prognosis, and cell proliferation, colony formation, wound healing, and Transwell invasion assays showed that high expression levels of TPD52L1 promoted malignant behaviors. In total, 70 proteins were identified as potential partners of hD53 by mass spectrometry. CRC formation was associated with three cancer hallmarks: dysregulation of metabolism, inactivation of the immune response, and activation of canonical cancer pathways. The TPD52L1 gene was identified as a potential marker to track tumor formation in CRC and as an indicator of poor patient prognosis.

Transcriptional and post-transcriptional control of DNA methyltransferase 3B is regulated by phosphatidylinositol 3 kinase/Akt pathway in human hepatocellular carcinoma cell lines.

DNA methyltransferases (DNMTs) are essential for maintenance of aberrant methylation in cancer cells and play important roles in the development of cancers. Unregulated activation of PI3K/Akt pathway is a prominent feature of many human cancers including human hepatocellular carcinoma (HCC). In present study, we found that DNMT3B mRNA and protein levels were decreased in a dose- and time-dependent manner in HCC cell lines with LY294002 treatment. However, we detected that LY294002 treatment did not induce increase of the degradation of DNMT3B protein using protein decay assay. Moreover we found that Akt induced alteration of the expression of DNMT3B in cells transfected with myristylated variants of Akt2 or cells transfected with small interfering RNA respectively. Based on DNMT3B promoter dual-luciferase reporter assay, we found PI3K pathway regulates DNMT3B expression at transcriptional level. And DNMT3B mRNA decay analysis suggested that down-regulation of DNMT3B by LY294002 is also post-transcriptional control. Furthermore, we demonstrated that LY294002 down-regulated HuR expression in a time-dependent manner in BEL-7404. In summary, we have, for the first time, demonstrate that PI3K/Akt pathway regulates the expression of DNMT3B at transcriptional and post-transcriptional levels, which is particularly important to understand the effects of PI3K/Akt and DNMT3B on hepatocarcinogenesis.

The effect of receptor protein tyrosine phosphatase kappa on the change of cell adhesion and proliferation induced by N-acetylglucosaminyltransferase V.

N-acetylglucosaminyltransferase V (GnT-V) has been reported to be positively associated with tumor progression, but its mechanism still remains unknown. In the present study, we found that GnT-V overexpression not only changed the glycosylation of receptor protein tyrosine phosphatase kappa (RPTPkappa) but also decreased its protein level. Moreover, GnT-V overexpression decreased cell calcium-independent adhesion and increased the tyrosine phosphorylation level of beta-catenin, in which RPTPkappa played an important role. Since RPTPkappa has an RXKR motif, which is a favored cleavage site for furin, we used furin inhibitor to further explore the effect of RPTPkappa on the change of cell adhesion and beta-catenin signaling induced by GnT-V. Our results showed that preventing RPTPkappa cleavage rescued the above effects of GnT-V, suggesting that furin cleavage could be one of the factors for RPTPkappa to regulate cell adhesion and beta-catenin signaling in GnT-V overexpression cell lines. In addition, the increased tyrosine phosphorylation level of beta-catenin was associated with the increased nuclear level of beta-catenin and downstream signaling molecules such as c-myc and cyclin D1 that were associated with cell proliferation. Our results suggest that GnT-V could decrease human hepatoma SMMC-7721 cell adhesion and promote cell proliferation partially through RPTPkappa.

The effect of epidermal growth factor receptor variant III on glioma cell migration by stimulating ERK phosphorylation through the focal adhesion kinase signaling pathway.

Epidermal growth factor receptor variant III (EGFRvIII), the most common EGFR mutation, is associated with cell migration of glioblastoma multiforme (GBM) cases; however, the mechanism has not been elucidated. In this study, we found that the EGFRvIII-promoted glioma cell migration was closely linked to high levels of tyrosine phosphorylation in focal adhesion kinase (FAK) Y397. We also demonstrated that EGFRvIII formed a complex with FAK, resulting in enhanced tyrosine phosphorylation levels of FAK Y397 and EGFR Y1068. After knockdown of FAK expression via anti-FAK shRNA, the U87ΔEGFR cell migration was significantly inhibited, accompanying with the reduced phosphorylation levels of extracellular signal-regulated kinase (ERK1/2). Furthermore, the role of ERK1/2 in FAK-regulated cell migration was confirmed. Taken together, our results suggest that FAK and its downstream molecule ERK were involved in EGFRvIII-promoted glioma cell migration in U87ΔEGFR cells.

Post-transcriptional and post-translational regulation of PTEN by transforming growth factor-beta1.

PTEN is a critical tumor suppressor gene mutated frequently in various human cancers. Previous studies have showed that PTEN mRNA expression is down-regulated by TGF-beta1 in various cell lines. In present study, we have found that TGF-beta1 down-regulates PTEN mRNA and protein expression in a dose- and time-dependent manner in hepatocarcinoma cell line SMMC-7721. Based on the PTEN promoter dual-luciferase report assay, we have found that PTEN transcription is not affected by TGF-beta1. By using transcriptional inhibitor actinomycin D (Act D), the turnover rate of PTEN transcripts appeared to be accelerated during TGF-beta1 stimulation, which indicated that down-regulation of PTEN by TGF-beta1 was post-transcriptional. What interested us was that transfection of PTEN coding sequence increased TGF-beta1-induced degradation of PTEN mRNA, suggesting that PTEN coding region was account for TGF-beta1-mediated down-regulation of PTEN. In addition, TGF-beta1 down-regulated PTEN expression was blocked by the TbetaIR inhibitor SB431542 and the p38 inhibitor SB203580, suggesting Smad and p38 MAPK signal pathways played crucial roles in PTEN down-regulation via TGF-beta1 stimulation. In this study, we also found TGF-beta1 accelerated down-regulation of PTEN through the ubiquitin-proteasome pathway. Collectively, our data clearly demonstrated that TGF-beta1-mediated down-regulation of PTEN was post-transcriptional and post-translational, depending on its coding sequence, Smad and p38-MAPK signal pathways were involved in this down-regulation.

E-cadherin decreased human breast cancer cells sensitivity to staurosporine by up-regulating Bcl-2 expression.

E-cadherin, a well-characterized cell-cell adhesion molecule, executes multifunction roles on cell behaviors. However, its effect on chemo-resistance remains controversial. In this study, we found that E-cadherin positive breast cell lines were less sensitive to staurosporine compared to E-cadherin negative ones. Next, we substantiated that the expression of E-cadherin in MDA-MB-435 cells could partly counteract the cytotoxic effect induced by staurosporine through a series of apoptosis assay. The resistance of E-cadherin over-expressing cells to staurosporine may due to the up-regulation of Bcl-2/Bax ratio. When E-cadherin interference plasmids were transfected into MCF-7 cells, Bcl-2 expression was down-regulated. Moreover, perturbation of E-cadherin function by blocking the cell-cell contact resulted in decreased cellular levels of Bcl-2 protein expression. All these results demonstrated the chemo-resistance function of E-cadherin in the condition of staurosporine treatment, therefore, might contribute effective therapeutic strategies in breast carcinoma.

Inhibition of cell growth and invasion by epidermal growth factor-targeted phagemid particles carrying siRNA against focal adhesion kinase in the presence of hydroxycamptothecin.

BACKGROUND: Previous studies demonstrated the EGF-targeted phagemid particles carrying siRNA against Akt could be expressed efficiently in the presence of hydroxycamptothecin (HCPT). However, no significant cell growth inhibition was obtained. This study was to further investigate whether the EGF-targeted phagemid particles carrying siRNA would be a promising tool for anti-cancer siRNA delivery. RESULTS: We found that pSi4.1-siFAK phagemid particles could significantly inhibit the expression of focal adhesion kinase in the HCPT-treated cells. Moreover, we also observed that the particles could potently suppress cell growth and cell invasion. CONCLUSION: These results indicated that EGF-targeted phagemid particles might be a promising tool for anti-cancer siRNA delivery in the presence of HCPT.

Phosphatidylinositol 3-kinase/protein kinase B pathway stabilizes DNA methyltransferase I protein and maintains DNA methylation.

DNA methylation, which affects gene expression and chromatin stability, is catalyzed by DNA methyltransferases (DNMTs) of which DNMT1 possesses most abundant activity. PI3K/PKB pathway is an important pathway involved in cell proliferation, viability, and metabolism and often disrupted in cancer. Here we investigated the impact of PKB on DNMT1 and DNA methylation. Positive correlation between PKB-Ser473-phosphorylation and DNMT1 protein level in 17 human cell lines (p<0.01) and in 27 human bladder cancer tissues (p<0.05) was found. With activator, inhibitor, siRNA and constitutively active or dominant-negative plasmids of PKB, we found that PKB increased the protein level of DNMT1 without coordinate mRNA change, which was specific rather than due to cell-cycle change. PKB enhanced DNMT1 protein stability independent of de novo synthesis of any protein, which was attributed to down-regulation of N-terminal-120-amino-acids-dependent DNMT1 degradation via ubiquitin-proteasome pathway. Gsk3beta inhibitor rescued the decrease of DNMT1 by PKB inhibition, suggesting that Gsk3beta mediated the stabilization of DNMT1 by PKB. Then role of PKB regulating DNMT1 was investigated. Inhibition of PKB caused observable DNA hypomethylation and chromatin decondensation and DNMT1 overexpression partially reversed cell growth inhibition by PKB inhibition. In conclusion, our results suggested that PKB enhanced DNMT1 stability and maintained DNA methylation and chromatin structure, which might contribute to cancer cell growth.

Development of efficient RNA interference system using EGF-displaying phagemid particles.

AIM: To develop an efficient RNA interference system using phagemid particles displaying the epidermal growth factor (EGF) ligand. METHODS: pSilencer1.0-siEGFP and pSilencer4.1-siAkt plasmids were constructed by gene clone technology. The modified helper phage genome (plasmid) M13KO7EGFCT was used to package phagemids, such as pSilencer1.0-siEGFP and pSilencer4.1-siAkt. ELISA was used to quantify the titer of the progeny virus particles. Single-strand DNA was extracted and analyzed by agarose gel electrophoresis to evaluate the percentage of the phagemid particles. The expression level of the reporter gene enhanced green fluorescence protein (EGFP) was determined by transducing phagemid particles packaging pSilencer1.0-siEGFP into cells. The level of Akt gene expression in cells transduced phagemid particles packaging pSilencer4.1-siAkt was examined by Western blotting. Hydroxycamptothecin (HCPT) was used to enhance the gene transduction efficiency. RESULTS: RNAi vectors pSilencer1.0-siEGFP and pSilencer4.1-siAkt were successfully constructed. Phagemid-encoding siRNA can be packaged efficiently. After the cells were infected by EGF displaying phagemid particles in the presence of HCPT, the expression of the target gene EGFP or Akt was substantially downregulated. CONCLUSION: Cell-targeted phagemid particles are efficient siRNA delivery vectors in the presence of HCPT.

MAGI-2 Inhibits cell migration and proliferation via PTEN in human hepatocarcinoma cells.

MAGI-2, a multidomain scaffolding protein, contains nine potential protein-protein interaction modules, including a GuK domain, two WW domains and six PDZ domains. In this study, we examined eight human hepatocarcinoma cell lines (HHCCs) and found that MAGI-2 was expressed only in 7721 cells. After 7721, 7404 and 97H cells were transfected with myc-MAGI-2 plasmid, their migration and proliferation was significantly inhibited, which was associated with downregulation of p-FAK and p-Akt. It is known that p-FAK is a substrate of PTEN and p-Akt can be regulated by PTEN via PIP(3). We demonstrated that PTEN was upregulated after myc-MAGI-2 transfection, which was due to the enhancement of PTEN protein stability rather than mRNA levels. Furthermore, MAGI-2-induced inhibition of cell migration and proliferation was attenuated in 7721 cells with PTEN silence or in PTEN-null cell line U87MG, and PTEN transfection could restore the effect of MAGI-2 in U87MG cells. Finally, the molecular association between PTEN and MAGI-2 was confirmed. Our results suggested that PTEN played a critical role in MAGI-2-induced inhibition of cell migration and proliferation in HHCCs.

Synergistic antitumor efficacy against the EGFRvIII+HER2+ breast cancers by combining trastuzumab with anti-EGFRvIII antibody CH12.

Although Trastuzumab, an anti-HER2 antibody, benefits certain patients with HER2-overexpressing breast cancer, de novo or acquired trastuzumab resistance remains a haunting issue. EGFRvIII, co-expressing with HER2 in some breast tumors, indicates a poor clinical prognosis. However, the role of EGFRvIII in the function of trastuzumab is not clear. Here, we demonstrated that EGFRvIII overexpression contributed to de novo trastuzumab resistance and the feedback activation of STAT3 caused by trastuzumab also resulted in acquired resistance in EGFRvIII(+)HER2(+) breast cancers. CH12, a highly effective anti-EGFRvIII monoclonal antibody that preferentially binds to EGFRvIII, significantly suppressed the growth of EGFRvIII+HER2(+) breast cancer cells in vitro and in vivo. Importantly, CH12 in combination with trastuzumab had a synergistic inhibitory effect on EGFRvIII(+)HER2(+) breast cancers in vitro and in vivo via attenuating the phosphorylation of EGFR and HER2 and their downstream signal pathways more effectively and reversing STAT3 feedback activation. Moreover, the combination therapy suppressed angiogenesis and induced cell apoptosis significantly. Together, these results suggested a synergistic efficacy of the combination of trastuzumab with CH12 against EGFRvIII(+)HER2(+) breast cancers, which might be a potential clinical application in the future.

Integrin beta1 subunit overexpressed in the SMMC-7721 cells regulates the promoter activity of p21(CIP1) and enhances its transcription.

Evidence has been emerging to suggest that integrin could induce growth inhibition in some cell types. Some of the molecular mechanisms underlying growth arrest have been elucidated. We reported here that overexpression of integrin beta1 imposed a growth inhibitory effect on the hepatocellular carcinoma cell line SMMC-7721, and this phenomenon was mainly attributed to the cyclin-dependent kinase inhibitor p21(CIP1). Furthermore, our findings suggested that transcription activity of the p21(CIP1) gene could be upregulated in the integrin beta1-overexpressing cells, and possibly controlled by the cis-elements in the core region of the p21(CIP1) promoter.

MAGI2 enhances the sensitivity of BEL-7404 human hepatocellular carcinoma cells to staurosporine-induced apoptosis by increasing PTEN stability.

Adaptor proteins are involved in the assembly of various intracellular complexes and the regulation of cellular functions. Membrane-associated guanylate kinase inverted 2 (MAGI2), also known as synaptic scaffolding molecule (S-SCAM), plays a critical role in signal transduction by assembling and anchoring its ligands. However, the role of MAGI2 in mediating apoptosis remains largely unknown. In the present study, BEL-7404 human hepatocellular carcinoma cells were transfected with a plasmid containing myc-MAGI2 or an empty plasmid and cell viability was then determined using the Cell Counting kit-8. Apoptosis was also detected using an Annexin V apoptosis assay. The cells were then treated with various doses of staurosporine (STS) for different periods of time. The overexpression of myc-MAGI2 was found to sensitize the BEL-7404 cells to apoptosis in response to STS in a time- and dose-dependent manner. Our results demonstrated that MAGI2 enhanced STS-induced apoptosis by increasing the protein expression of cytoplasmic phosphatase and tensin homologue deleted on chromosome 10 (PTEN) and decreasing its protein degradation. The apoptotic sensitivity of the cells caused by the overexpression of myc-MAGI2 was reversed by the silencing of PTEN expression by PTEN siRNA, thus revealing a momentous role of PTEN in the enhancement of the sensitivity of cancer cells to STS-induced apoptosis by MAGI2. Finally, we observed that the MAGI-PTEN complex triggered by MAGI2 overexpression reduced the phosphorylation levels of AKT. These results suggest that MAGI2 overexpression enhances the sensitivity of cancer cells harboring ectopic PTEN to STS-induced apoptosis.

HER3 intracellular domains play a crucial role in HER3/HER2 dimerization and activation of downstream signaling pathways.

Dimerization among the EGFR family of tyrosine kinase receptors leads to allosteric activation of the kinase domains of the partners. Unlike other members in the family, the kinase domain of HER3 lacks key amino acid residues for catalytic activity. As a result, HER3 is suggested to serve as an allosteric activator of other EGFR family members which include EGFR, HER2 and HER4. To study the role of intracellular domains in HER3 dimerization and activation of downstream signaling pathways, we constructed HER3/HER2 chimeric receptors by replacing the HER3 kinase domain (HER3-2-3) or both the kinase domain and the C-terminal tail (HER3-2-2) with the HER2 counterparts and expressed the chimeric receptors in Chinese hamster ovary (CHO) cells. While over expression of the intact human HER3 transformed CHO cells with oncogenic properties such as AKT/ERK activation and increased proliferation and migration, CHO cells expressing the HER3-2-3 chimeric receptor showed significantly reduced HER3/HER2 dimerization and decreased phosphorylation of both AKT and ERK1/2 in the presence of neuregulin-1 (NRG-1). In contrast, CHO cells expressing the HER3-2-2 chimeric receptor resulted in a total loss of downstream AKT activation in response to NRG-1, but maintained partial activation of ERK1/2. The results demonstrate that the intracellular domains play a crucial role in HER3's function as an allosteric activator and its role in downstream signaling.

Increase in beta1-6 GlcNAc branching caused by N-acetylglucosaminyltransferase V directs integrin beta1 stability in human hepatocellular carcinoma cell line SMMC-7721.

In this study, an enzymatic inactive mutant of GnT-V (delta cGnT-V) was constructed and transfected in SMMC 7721 cell line. Integrin beta1 in delta cGnT-V transfectants (delta c-7721) showed attenuation of the number of beta1-6 GlcNAc branching, whereas those in wtGnT-V transfectants (wt-7721) presented a beta1-6 GlcNAc-rich pattern. High integrin beta1 expression was observed in wt-7721 compared with mock cells (7721 cell transfected with the vector pcDNA3), while transfection of delta cGnT-V decreased the integrin beta1 expression, despite of no significant changes on integrin beta1 mRNA level in these cell lines. Pulse-chase experiment showed that Integrin beta1 in delta c-7721 was prone to quick degradation and its half-life was less than 3 h, on the contrary, the alleviating degradation of beta1 subunit was observed in wt-7721 where the beta1 subunit half-life was about 16 h, meanwhile, the degradation rate of beta1 subunit in mock cells was in between, about 10 h. More effective in promoting cell migration toward fibronectin and invasion through Matrigel was observed in wt-7721 while this was almost suppressed in delta c-7721. Our results suggest that the addition of beta1-6 GlcNAc branching caused more fully glycosylated mature form on integrin beta1 and inhibited beta1 protein degradation. Glycosylation caused by GnT-V directs integrin beta1 stability and more delivery to plasma membrane, subsequently promotes Fn-based cell migration and invasion.

Profilin 1 obtained by proteomic analysis in all-trans retinoic acid-treated hepatocarcinoma cell lines is involved in inhibition of cell proliferation and migration.

Previous studies have shown that all-trans retinoic acid (ATRA) suppresses growth of hepatocarcinoma cell in vitro. To understand the underlying mechanisms, we investigated the protein expression profiles by 2-DE in hepatocarcinoma cell line SMMC-7721 treated with ATRA. Our results reveal that six proteins were differently expressed in response to ATRA. Using MS and database searching, they were identified as profilin 1, phosphoglycerate kinase 1, RuvB-like 1, alpha-enolase, pyridoxal kinase and F-actin capping protein. We selected the up-regulated protein, profilin 1 (PFN1), for further studies. The PFN1 expression was increased in response to ATRA in a dose- and time-dependent manner. The PFN1 expression was reduced dramatically in four hepatoma cell lines compared to L02 cell line of non-tumor origin. The PFN1 expression was also examined in 4 cases of primary hepatocarcinoma tissues by Western blot and 30 cases by tissues microarray. It was found that the protein level of PFN1 was lower in hepatocarcinoma tissues compared to that in the adjacent tissues. Similar to ATRA, overexpression of PFN1 led to inhibition of cell proliferation and migration. Furthermore, RNAi-based PFN1 knockdown could rescue the inhibitory effect of ATRA on cell proliferation and migration. In conclusion, ATRA inhibited cell proliferation and migration through up-regulation of PFN1.