Anti-tumor effects of P-LPK-CPT, a peptide-camptothecin conjugate, in colorectal cancer.

To explore highly selective targeting molecules of colorectal cancer (CRC) is a challenge. We previously identified a twelve-amino acid peptide (LPKTVSSDMSLN, namely P-LPK) by phage display technique which may specifically binds to CRC cells. Here we show that P-LPK selectively bind to a panel of human CRC cell lines and CRC tissues. In vivo, Gallium-68 (68Ga) labeled P-LPK exhibits selective accumulation at tumor sites. Then, we designed a peptide-conjugated drug comprising P-LPK and camptothecin (CPT) (namely P-LPK-CPT), and found P-LPK-CPT significantly inhibits tumor growth with fewer side effects in vitro and in vivo. Furthermore, through co-immunoprecipitation and molecular docking experiment, the glutamine transporter solute carrier 1 family member 5 (SLC1A5) was identified as the possible target of P-LPK. The binding ability of P-LPK and SLC1A5 is verified by surface plasmon resonance and immunofluorescence. Taken together, P-LPK-CPT is highly effective for CRC and deserves further development as a promising anti-tumor therapeutic for CRC, especially SLC1A5-high expression type.

Fbxo45-mediated NP-STEP46 degradation via K6-linked ubiquitination sustains ERK activity in lung cancer.

Lung cancer is one of the most threatening malignant tumors to human health. Epidermal growth factor receptor (EGFR)-targeted therapy is a common and essential means for the clinical treatment of lung cancer. However, drug resistance has always affected the therapeutic effect and survival rate in non-small cell lung cancer (NSCLC). Tumor heterogeneity is a significant reason, yielding various drug resistance mechanisms, such as EGFR-dependent or -independent extracellular signal-regulated kinase 1 and/or 2 (ERK1/2) activation in NSCLC. To examine whether this aberrant activation of ERK1/2 is related to the loss of function of its specific phosphatase, a series of in vitro and in vivo assays were performed. We found that F-box/SPRY domain-containing protein 1 (Fbxo45) induces ubiquitination of NP-STEP46 , an active form of striatal-enriched protein tyrosine phosphatase, with a K6-linked poly-ubiquitin chain. This ubiquitination led to proteasome degradation in the nucleus, which then sustains the aberrant level of phosphorylated-ERK (pERK) and promotes tumor growth of NSCLC. Fbxo45 silencing can significantly inhibit cell proliferation and tumor growth. Moreover, NSCLC cells with silenced Fbxo45 showed great sensitivity to the EGFR tyrosine kinase inhibitor (TKI) afatinib. Here, we first report this critical pERK maintenance mechanism, which might be independent of the upstream kinase activity in NSCLC. We propose that inhibiting Fbxo45 may combat the issue of drug resistance in NSCLC patients, especially combining with EGFR-TKI therapy.

Positive feedback between ROS and cis-axis of PIASxα/p38α-SUMOylation/MK2 facilitates gastric cancer metastasis.

MAPK/p38 is an important mammalian signaling cascade that responds to a variety of intracellular or extracellular stimuli, such as reactive oxygen species (ROS), and participates in numerous physiological and pathological processes. However, the biological function of p38 in different tumors, and even at different stages of the same tumor, remains elusive. To further understand the regulatory mechanism of p38 and oxidative stress in the occurrence and development of gastric cancer, we report SUMOylation as a novel post-translational modification occurring on lysine 152 of MAPK14/p38α through immunoprecipitation and series of pull-down assays in vitro and in vivo. Importantly, we determine that p38α-SUMOylation functions as an authentic sensor and accelerator of reactive oxygen species generation via interaction with and activation of MK2 in the nucleus, and the ROS accumulation, in turn, promotes the SUMOylation of p38α by stabilizing the PIASxα protein. This precise regulatory mechanism is exploited by gastric cancer cells to create an internal environment for survival and, ultimately, metastasis. This study reveals novel insights into p38α-SUMOylation and its association with the intracellular oxidative stress response, which is closely related to the processes of gastric cancer. Furthermore, the PIASxα/p38α-SUMOylation/MK2 cis-axis may serve as a desirable therapeutic target in gastric cancer as targeting PIASxα, MK2, or a specific peptide region of p38α may reconcile the aberrant oxidative stress response in gastric cancer cells.

Dynamic Structural and Functional Reorganizations Following Motor Stroke.

BACKGROUND The combined effects of bilateral corticospinal tract (CST) reorganization and interhemispheric functional connectivity (FC) reorganization on motor recovery of upper and lower limbs after stroke remain unknown. MATERIAL AND METHODS A total of 34 patients underwent magnetic resonance imaging (MRI) examination at weeks 1, 4, and 12 after stroke, with a control group of 34 healthy subjects receiving 1 MRI examination. Interhemispheric FC in the somatomotor network (SMN) was calculated using the resting-state functional MRI (rs-fMRI). Fractional anisotropy (FA) of bilateral CST was recorded as a measure of reorganization obtained from diffusion tensor imaging (DTI). After intergroup comparisons, multiple linear regression analysis was used to explore the effects of altered FA and interhemispheric FC on motor recovery. RESULTS Interhemispheric FC restoration mostly occurred within 4 weeks after stroke, and FA in ipsilesional remained CST consistently elevated within 12 weeks. Multivariate linear regression analysis showed that the increase in both interhemispheric FC and ipsilesional CST-FA were significantly correlated with greater motor recovery from week 1 to week 4 following stroke. Moreover, only increased FA of ipsilesional CST was significantly correlated with greater motor recovery during weeks 4 to 12 after stroke compared to interhemispheric FC. CONCLUSIONS Our results show dynamic structural and functional reorganizations following motor stroke, and structure reorganization may be more related to motor recovery at the late subacute phase. These results may play a role in guiding neurological rehabilitation.

The investigation of genetic and clinical features in patients with hereditary spastic paraplegia in central-Southern China.

OBJECTIVE: Hereditary spastic paraplegias (HSP) is a clinically and genetically heterogeneous group of neurodegenerative disorders. We describe the genetic and clinical features of a cohort of five HSP families from central-southern China. METHODS: Using targeted exome-sequencing technology, we investigated the genetic and clinical features in five HSP families. We reviewed the clinical histories of these patients as well as the molecular and functional characterization of the associated gene variants. We also performed functional analysis of an intron variant of SPAST in vitro. RESULTS: We identified a known SPAST mutation (p.Pro435Leu) in a family with autosomal dominant HSP (AD-HSP) and four novel variants in two HSP families and a sporadic case. These identified four novel variants included a variant in SPG11 (p.Val1979Ter), two variants in B4GALNT1 (p.Ser475Phe and c.1002 + 2 T > G), and a splicing site variant in SPAST (c.1245+5G>A). Minigene analysis of the splicing variant in SPAST (c.1245+5G>A) revealed that the mutation resulted in mRNAs with a loss of exon 9. The SPG4 family carrying c.1245+5G>A variant in SPAST exhibited genetic anticipation, with a decreased age at onset and increased severity in successive generations. The proband with p.Val1979Ter variant in SPG11 showed characteristic clinical features of early-onset, severe spasticity, and corpus callosum atrophy which were highly suggestive of the diagnosis of SPG11-associated HSP. CONCLUSIONS: Our findings strongly support variable phenotype of B4GALNT1-related SPG26 and also expand the clinical and mutation spectrum of HSP caused by mutations in SPAST, SPG11, and B4GALNT1. These results will help to improve the efficiency of early diagnosis in patients clinically suspected of HSP.

SUMOylation is essential for Sirt2 tumor-suppressor function in neuroblastoma.

SUMOylation is an important post-translational modification that participates in a variety of cellular physiological and pathological processes in eukaryotic cells. Sirt2, a NAD+-dependent deacetylase, usually exerts a tumor-suppressor function. However, the role of SUMOylation in cancer cells is not fully known. In this study, we found that SUMOylation can occur in the Sirt2 protein at both lysine 183 and lysine 340 sites. SUMOylation did not affect Sirt2 localization or stability but was involved in P38-mTORC2-AKT cellular signal transduction via direct deacetylation on a new substrate MAPK/P38. SUMOylation-deficient Sirt2 lost the capability of suppressing tumor processes and showed resistance to the Sirt2-specific inhibitor AK-7 in neuroblastoma cells. Here, we revealed the important function of Sirt2-SUMOylation, which is closely associated with cellular signal transduction and is essential for suppressing tumorigenesis in neuroblastoma.

Peritoneal macrophages attenuate retinal ganglion cell survival and neurite outgrowth.

Inflammation is a critical pathophysiological process that modulates neuronal survival in the central nervous system after disease or injury. However, the effects and mechanisms of macrophage activation on neuronal survival remain unclear. In the present study, we co-cultured adult Fischer rat retinas with primary peritoneal macrophages or zymosan-treated peritoneal macrophages for 7 days. Immunofluorescence analysis revealed that peritoneal macrophages reduced retinal ganglion cell survival and neurite outgrowth in the retinal explant compared with the control group. The addition of zymosan to peritoneal macrophages attenuated the survival and neurite outgrowth of retinal ganglion cells. Conditioned media from peritoneal macrophages also reduced retinal ganglion cell survival and neurite outgrowth. This result suggests that secretions from peritoneal macrophages mediate the inhibitory effects of these macrophages. In addition, increased inflammation- and oxidation-related gene expression may be related to the enhanced retinal ganglion cell degeneration caused by zymosan activation. In summary, this study revealed that primary rat peritoneal macrophages attenuated retinal ganglion cell survival and neurite outgrowth, and that macrophage activation further aggravated retinal ganglion cell degeneration. This study was approved by the Animal Ethics Committee of the Joint Shantou International Eye Center of Shantou University and the Chinese University of Hong Kong, Shantou, Guangdong Province, China, on March 11, 2014 (approval no. EC20140311(2)-P01).

The p53-inducible CLDN7 regulates colorectal tumorigenesis and has prognostic significance.

Most colorectal cancer (CRC) are characterized by allele loss of the genes located on the short arm of chromosome 17 (17p13.1), including the tumor suppressor p53 gene. Although important, p53 is not the only driver of chromosome 17p loss. In this study, we explored the biological and prognostic significance of genes around p53 on 17p13.1 in CRC. The Cancer Genome Atlas (TCGA) were used to identify differentially expressed genes located between 1000 kb upstream and downstream of p53 gene. The function of CLDN7 was evaluated by both in vitro and in vivo experiments. Quantitative real-time PCR, western blot, and promoter luciferase activity, immunohistochemistry were used to explore the molecular drivers responsible for the development and progression of CRC. The results showed that CLDN7, located between 1000 kb upstream and downstream of p53 gene, were remarkably differentially expressed in tumor and normal tissues. CLDN7 expression also positively associated with p53 level in different stages of the adenoma-carcinoma sequence. Both in vitro and in vivo assays showed that CLDN7 inhibited cell proliferation in p53 wild type CRC cells, but had no effects on p53 mutant CRC cells. Mechanistically, p53 could bind to CLDN7 promoter region and regulate its expression. Clinically, high CLDN7 expression was negatively correlated with tumor size, invasion depth, lymphatic metastasis and AJCC III/IV stage, but was positively associated with favorable prognosis of CRC patients. Collectively, our work uncovers the tumor suppressive function for CLDN7 in a p53-dependent manner, which may mediate colorectal tumorigenesis induced by p53 deletion or mutation.

N-glycosylated SGK196 suppresses the metastasis of basal-like breast cancer cells.

SGK196 is a protein O-mannose kinase involved in an indispensable phosphorylation step during laminin-binding glycan synthesis on alpha-dystroglycan (α-DG). However, the function of SGK196 in cancer diseases remains elusive. In the current study, we demonstrated that SGK196 is primarily modified by N-glycosylation in breast cancer (BC) cells. Furthermore, gain and loss-of-function studies showed that N-glycosylated SGK196 suppresses cell migration, invasion, and metastasis in BC, particularly in the basal-like breast cancer (BLBC) type. In addition, we found that SGK196 N-glycosylation performs the regulatory function through the PI3K/AKT/GSK3ß signaling pathway. Collectively, our results show that N-glycosylated SGK196 plays suppression roles in BLBC metastases, therefore providing new insights into SGK196 function in BC.

The MTOR signaling pathway regulates macrophage differentiation from mouse myeloid progenitors by inhibiting autophagy.

Understanding of the mechanism for myeloid differentiation provides important insights into the hematopoietic developmental processes. By using an ESC-derived myeloid progenitor cell model, we found that CSF2/GM-CSF triggered macrophage differentiation and activation of the MTOR signaling pathway. Activation or inhibition of the MTOR signaling enhanced or attenuated macrophage differentiation, respectively, suggesting a critical function. We further showed that macroautophagy/autophagy was inhibited with the addition of CSF2. Furthermore, pharmacological inhibition and genetic modification of autophagy enhanced macrophage differentiation and rescued the inhibitory effect on differentiation caused by MTOR inhibition. Thus, the MTOR signaling pathway regulates macrophage differentiation of myeloid progenitors by inhibiting autophagy. Our results provide new insights into the mechanisms for myeloid differentiation and may prove useful for therapeutic applications of hematopoietic and myeloid progenitor cells. Abbreviations: 2-DG: 2-deoxy-D-glucose; ADGRE1/F4/80: adhesion G protein-coupled receptor E1; BM: bone marrow; CQ: chloroquine; ECAR: extracellular acidification rate; ESC: embryonic stem cell; CSF2/GM-CSF: colony stimulating factor 2; CSF3/G-CSF: colony stimulating factor 3; HPC: hematopoietic progenitor cell; ITGAM/CD11b: integrin alpha M; LPS: lipopolysaccharide; MFI: median fluorescence intensity; MTOR: mechanistic target of rapamycin kinase; RPS6KB1/p70S6K1: ribosomal protein S6 kinase, polypeptide 1; shRNA: short hairpin RNA; SQSTM1/p62: sequestosome 1.

Autophagy inhibition enhances celecoxib-induced apoptosis in osteosarcoma.

Osteosarcoma (OS) is the most prevalent bone malignancy in childhood and adolescence, with highly aggressive and early systemic metastases. Here, we reported that celecoxib, a selective COX-2 inhibitor in the NSAID class, exhibits strong antitumor activity in dose dependent manner in two OS cell lines-143B and U2OS. We showed that celecoxib inhibits OS cell growth, causes G0/G1-phase arrest, modulates apoptosis and autophagy and reduces migration in OS cells. In addition, the results of fluorescent mitochondrial probe JC-1 test indicated that the mitochondrial pathway mediates celecoxib-induced apoptosis. Significantly, the autophagy inhibitor CQ combined with celecoxib causes greater cell proliferation inhibition and apoptosis. Pharmacologic inhibition of autophagy with another potent autophagy inhibitor SAR405 also enhances celecoxib-mediated suppression of cell viability. These results were confirmed with shRNAs targeting the autophagy-related gene Atg5. In OS tumor xenografts in vivo, celecoxib also presents antitumor activity. Taken together, our results shed light on the function and mechanism of antitumor action of celecoxib for treatment of OS patients.

NLRP12 Promotes Mouse Neutrophil Differentiation through Regulation of Non-canonical NF-κB and MAPKERK1/2 Signaling.

Neutrophils are the most important component of the innate immune system. Mechanistic understanding of the mechanism underlying neutrophil differentiation remains elusive. Using genome-wide RNA-seq, we identified genes whose expression is dramatically up-regulated during neutrophil differentiation. Among them is nucleotide-binding leucine-rich repeat and pyrindomain-containing receptor 12 (NLRP12), which plays a role in immune inflammatory responses. Genetic ablation of NLRP12 suppresses NF-κB inducing kinase (NIK) stabilization, RelB nuclear translocation and neutrophil differentiation in vitro. At a mechanistic level, NLRP12 inhibits the activity of mitogen-activated protein kinases (MAPK)/extracellular signal-regulated kinases (ERK1/2), relieves ERK1/2 suppression of NIK protein levels. Thus, NLRP12 enhances noncanonical NF-κB signaling through inhibition of ERK1/2 signaling, thereby promoting neutrophil differentiation.

Metformin is associated with survival benefit in pancreatic cancer patients with diabetes: a systematic review and meta-analysis.

BACKGROUND: Pancreatic cancer is a highly lethal disease with a poor prognosis while metformin has been associated with a decreased risk of pancreatic cancer. Although the benefit of metformin was observed for pancreatic cancer prevention, it is not clear whether it can also affect the survival of pancreatic cancer patients with type 2 diabetes mellitus. A systematic review and meta-analysis was conducted to assess the effect of metformin on the survival of pancreatic cancer patients with type 2 diabetes mellitus. METHODS: Two independent authors searched PubMed and Web of science up to 08/07/2016. We assessed studies for eligibility, extracted data, and examined their quality, with the primary outcome as overall survival. We used published hazard ratio (HR) available or estimated based on other survival data. We pooled the data and used a random-effect model to combine direct comparisons from included articles. We also investigated treatment effects by different countries, quality and the time of metformin initiation. RESULTS: We found that there was a relative survival benefit associated with metformin treatment compared with non-metformin treatment in both overall survival (OS) ([HR] 0.84; 95% confidence interval [CI]: 0.73 - 0.96). These associations were also observed in subgroups of Asian countries and high quality articles. CONCLUSIONS: Our results support the notion that metformin maybe the best anti-diabetic medicine of choice in patients with pancreatic cancer and concurrent type 2 diabetes mellitus. The perspectives of enhancing survival of pancreatic cancer patients with diabetes mellitus by the use of metformin deserve more attention in future research and clinical practice.

A simple, rapid and sensitive FRET assay for botulinum neurotoxin serotype B detection.

Botulinum neurotoxins (BoNTs), the most potent naturally-occurring neurotoxins known to humans, comprise seven distinct serotypes (BoNT/A-G), each of which exhibits unique substrate specificity. Many methods have been developed for BoNT detection, in particular for BoNT/A, with various complexity and sensitivity, while substrate based FRET assay is considered as the most widely used approach due to its simplicity and sensitivity. In this study, we designed a vesicle-associated membrane protein 2 (VAMP2) based FRET assay based on the understanding of the VAMP2 and light chain/B (LC/B) interactions in our previous studies. The current design constituted the shortest peptide, VAMP2 (63-85), with FRET dyes (EDAN and Dabcyl) labelled at position 76 and 85, respectively, which showed minimal effect on VAMP2 substrate catalysis by LC/B and therefore enhanced the sensitivity of the assay. The FRET peptide, designated as FVP-B, was specific to LC/B, with a detection sensitivity as low as ∼20 pM in 2 h. Importantly, FVP-B showed the potential to be scaled up and used in high throughput screening of LC/B inhibitor. The currently developed FRET assay is one of the most economic and rapid FRET assays for LC/B detection.

Convergent synthesis of MUC1 glycopeptides via serine ligation.

Syntheses of MUC1 glycopeptides (40-mer and 80-mer) are described. The convergent synthesis was achieved by native serine ligation using side-chain unprotected glycopeptide segments.

Total synthesis of daptomycin by cyclization via a chemoselective serine ligation.

A total synthesis of daptomycin, the first natural product antibiotic launched in a generation, was achieved. This convergent synthesis relies on an efficient macrocyclization via a serine ligation to assemble the 31-membered cyclic depsipeptide. The difficult esterification by the nonproteinogenic amino acid kynurenine was accomplished via the esterification of a threonine residue by a suitably protected Trp ester, followed by ozonolysis. This synthesis provides a foundation and framework to prepare varied analogues of daptomycin to establish its structure-activity profile.

Protein chemical synthesis by serine and threonine ligation.

An efficient method has been developed for the salicylaldehyde ester-mediated ligation of unprotected peptides at serine (Ser) or threonine (Thr) residues. The utility of this peptide ligation approach has been demonstrated through the convergent syntheses of two therapeutic peptides--ovine-corticoliberin and Forteo--and the human erythrocyte acylphosphatase protein (∼11 kDa). The requisite peptide salicylaldehyde ester precursor is prepared in an epimerization-free manner via Fmoc-solid-phase peptide synthesis.

Thioglycosylation of 1,2-cis-glycosyl acetates: a long-standing overlooked issue in preparative carbohydrate chemistry.

1,2-cis-Glycosyl acetates with the α-configuration were revealed to be very unreactive towards Lewis acid catalyzed thioglycosylations. Optimal and cost-effective conditions for enabling this direct conversion is absent in the literature. Our studies have shown that elevating the reaction temperature with a catalytic amount of BF(3)·OEt(2) was more effective than changing Lewis acids with higher acidities to accommodate the low reactivity of α-glycosyl acetates. The effect of impurities in stored BF(3)·OEt(2) on the reaction is also discussed.

Human macrophage metalloelastase correlates with angiogenesis and prognosis of gastric carcinoma.

BACKGROUND AND AIMS: The function of human macrophage metalloelastase (HME) also known as matrix metalloproteinase 12, in tumorigenesis is contradictory. The current study was designed to investigate the association of HME expression with angiogenesis and prognosis of gastric carcinomas. METHODS: In situ hybridization and immunohistochemistry were used to detect HME in human gastric carcinomas, chronic gastritis with atypical hyperplasia, and normal gastric epithelium mucosa. The results were further confirmed by RT-PCR or semi-quantitative reverse transcription polymerase chain reaction and Western blotting in gastric carcinomas and paired noncancerous tissues. VEGF and microvessel density count were also detected by immunohistochemical staining in all carcinoma tissues. The prognostic significance of HME was assessed with multiple linear regression analysis and Cox proportional hazards model. RESULTS: High expression of HME protein/mRNA was observed in gastric carcinomas and atypical hyperplasia tissues compared with normal gastric epithelium mucosa, or paired noncancerous tissues. HME protein/mRNA were negatively correlated with MVD (p < 0.01), VEGF (p < 0.01), tumor differentiation grade (p < 0.05), vascular invasion (p < 0.01), and recurrence (p < 0.05-0.01). HME protein was an independent influential factor of MVD (p < 0.01). HME protein/mRNA was an independent prognostic factor of gastric carcinoma (p < 0.05-0.01). Patients with overexpression of HME protein/mRNA demonstrated a significantly better survival rate compared with those who did not (p < 0.05-0.01). CONCLUSIONS: Overexpression of HME is strongly correlated with the reduced angiogenesis and vascular invasion of gastric carcinoma, and may serve as a useful predictive indicator in patients with this disease.