Down-regulation of SNX1 predicts poor prognosis and contributes to drug resistance in colorectal cancer

Spatiotemporal regulation of the hepatocyte growth factor receptor MET activity by sorting nexins 1/2 in HCT116 colorectal cancer cells

Cumulative research findings support the idea that endocytic trafficking is crucial in regulating receptor signaling and associated diseases. Specifically, strong evidence points to the involvement of sorting nexins (SNXs), particularly SNX1 and SNX2, in the signaling and trafficking of the receptor tyrosine kinase (RTK) MET in colorectal cancer (CRC). Activation of hepatocyte growth factor (HGF) receptor MET is a key driver of CRC progression. In the present study, we utilized human HCT116 CRC cells with SNX1 and SNX2 genes knocked out to demonstrate that their absence leads to a delay in MET entering early endosomes. This delay results in increased phosphorylation of both MET and AKT upon HGF stimulation, while ERK1/2 (extracellular signal-regulated kinases 1 and 2) phosphorylation remains unaffected. Despite these changes, HGF-induced cell proliferation, scattering, and migration remain similar between the parental and the SNX1/2 knockout cells. However, in the absence of SNX1 and SNX2, these cells exhibit increased resistance to TRAIL-induced apoptosis. This research underscores the intricate relationship between intracellular trafficking, receptor signaling, and cellular responses and demonstrates for the first time that the modulation of MET trafficking by SNX1 and SNX2 is critical for receptor signaling that may exacerbate the disease.

Sorting nexins: role in the regulation of blood pressure

Sorting nexins (SNXs) are a family of proteins that regulate cellular cargo sorting and trafficking, maintain intracellular protein homeostasis, and participate in intracellular signaling. SNXs are also important in the regulation of blood pressure via several mechanisms. Aberrant expression and dysfunction of SNXs participate in the dysregulation of blood pressure. Genetic studies show a correlation between SNX gene variants and the response to antihypertensive drugs. In this review, we summarize the progress in SNX-mediated regulation of blood pressure, discuss the potential role of SNXs in the pathophysiology and treatment of hypertension, and propose novel strategies for the medical therapy of hypertension.

Promotion of esophageal adenocarcinoma metastasis via Wnt/ß-catenin signal pathway by sorting nexins 3

BACKGROUND

Esophageal adenocarcinoma is often associated with late diagnoses, poor prognoses, significant morbidities, and high mortality rates. Aberrant expression of Wnt/β-catenin signal pathways were observed in the tumorigenesis and metastasis of esophageal adenocarcinoma. Sorting nexins 3 has been shown to participate in Wnt protein sorting and regulate Wnt/β-catenin signal transduction. Thus, we studied the role and molecular mechanism of sorting nexins 3 in esophageal adenocarcinoma.

METHODS

Tissue microassay were used to analyze the expression of sorting nexins 3 in esophageal adenocarcinoma tissue and its relationship with survival rate. Using in vivo and in vitro models, we further investigated the effect of sorting nexins 3 on tumor growth and metastasis and underling mechanism.

RESULTS

Immunohistochemical staining of human esophageal adenocarcinoma tissue microassay revealed an increased sorting nexins 3 level in esophageal adenocarcinoma tissue and high expression of sorting nexins 3 correlated with the poor prognosis. In vitro study showed that sorting nexins 3 knockdown suppressed esophageal adenocarcinoma cell invasion, metastasis, and epithelial-mesenchymal translation (EMT) process, and this result was confirmed by in vivo tumor metastasis assays. Moreover, we further proved that sorting nexins 3 affected cell invasion and EMT through Wnt/β-catenin signal pathway.

CONCLUSION

Our data provided strong evidence that sorting nexins 3 played a critical role in esophageal adenocarcinoma metastasis through Wnt/β-catenin signal pathway.

Sorting nexins: A novel promising therapy target for cancerous/neoplastic diseases

Sorting nexins (SNXs) are a diverse group of cytoplasmic- and membrane-associated phosphoinositide-binding proteins containing the PX domain proteins. The function of SNX proteins in regulating intracellular protein trafficking consists of endocytosis, endosomal sorting, and endosomal signaling. Dysfunctions of SNX proteins are demonstrated to be involved in several cancerous/neoplastic diseases. Here, we review the accumulated evidence of the molecular structure and biological function of SNX proteins and discuss the regulatory role of SNX proteins in distinct cancerous/neoplastic diseases. SNX family proteins may be a valuable potential biomarker and therapeutic strategy for diagnostics and treatment of cancerous/neoplastic diseases.

Prediction of Poor Outcomes in Patients with Colorectal Cancer: Elevated Preoperative Prothrombin Time (PT) and Activated Partial Thromboplastin Time (APTT)

Background and Objective

Tools for the non-invasive assessment of colorectal cancer (CRC) prognosis have profound significance. Although plasma coagulation tests have been investigated in a variety of tumours, the prognostic value of the prothrombin time (PT) and activated partial thromboplastin time (APTT) in CRC has not been discussed. Our study objective was to explore the prognostic significance of preoperative PT and APTT in CRC patients.

Patients and Methods

A retrospective analysis of preoperative coagulation indexes including PT, PTA, INR, APTT, FIB, TT, PLT, NLR and PLR in 250 patients with CRC was performed. Kaplan–Meier and multivariate Cox regression analysis were used to demonstrate the prognostic value of these preoperative coagulation indexes.

Results

The overall survival (OS, p<0.05) and disease-free survival (DFS, p<0.05) of CRC patients with lower PT and APTT levels were significantly prolonged. Based on univariate analysis, PT levels (p<0.001, p<0.001), PTA levels (p=0.001, p=0.001), APTT levels (p=0.001, p<0.001), INR levels (p<0.001, p<0.001), fibrinogen levels (p=0.032, p=0.036), tumour status (p=0.005, p=0.003), nodal status (p<0.001, p<0.001), metastasis status (p<0.001, p<0.001) and TNM stages (p<0.001, p<0.001) were remarkably associated with DFS and OS. Multivariate Cox regression analysis suggested that the levels of PT (HR: 2.699, p=0.006) and APTT (HR: 1.942, p=0.015), metastasis status (HR: 2.091, p= 0.015) and TNM stage (HR: 7.086, p=0.006) were independent predictors of survival in CRC. In the whole cohort, the enrolled patients were then divided into three groups according to their PT and APTT levels. The OS and DFS differed notably among the low-risk (PT<11.85 sec and APTT<25.85 sec), medium-risk (PT≥11.85 sec or APTT≥25.85 sec), and high-risk (PT≥11.85 sec and APTT≥25.85 sec) groups.

Conclusion

Elevated levels of preoperative PT and APTT were predictors of poor outcomes in CRC patients. Moreover, the combination of preoperative PT and APTT can be a new prognostic stratification approach for more precise clinical staging of CRC.

The emerging role of sorting nexins in cardiovascular diseases

The sorting nexin (SNX) family consists of a diverse group of cytoplasmic- and membrane-associated phosphoinositide-binding proteins that play pivotal roles in the regulation of protein trafficking. This includes the entire endocytic pathway, such as endocytosis, endosomal sorting, and endosomal signaling. Dysfunctions of SNX pathway are involved in several forms of cardiovascular disease (CVD). Moreover, SNX gene variants are associated with CVDs. In this review, we discuss the current knowledge on SNX-mediated regulatory mechanisms and their roles in the pathogenesis and treatment of CVDs.

Candidate genes associated with the heritable humoral response to Mycobacterium avium ssp. paratuberculosis in dairy cows have factors in common with gastrointestinal diseases in humans

Infection of cattle with bovine paratuberculosis (i.e., Johne's disease) is caused by Mycobacterium avium ssp. paratuberculosis (MAP) and results in a chronic incurable gastroenteritis. This disease, which has economic ramifications for the cattle industry, is increasing in detected prevalence globally; subclinically infected animals can silently shed the bacterium into the environment for years, exposing contemporaries and hampering disease-control programs. The objective of the present study was to first quantify the genetic parameters for humoral response to MAP in dairy cattle. This was followed by a genome-based association analysis and subsequent downstream bioinformatic analyses from imputed whole genome sequence SNP data. After edits, ELISA test records were available on 136,767 cows; analyses were also undertaken on a subset of 33,818 of these animals from herds with at least 5 MAP ELISA-positive cows, with at least 1 of those positive cows being homebred. Variance components were estimated using univariate animal and sire linear mixed models. The heritability calculated from the animal model for humoral response to MAP using alternative phenotype definitions varied from 0.02 (standard error = 0.003) to 0.05 (standard error = 0.008). The genome-based associations were undertaken within a mixed model framework using weighted deregressed estimated breeding values as a dependent variable on 1,883 phenotyped animals that were ≥87.5% Holstein-Friesian. Putative susceptibility quantitative trait loci (QTL) were identified on Bos taurus autosome 1, 3, 5, 6, 8, 9, 10, 11, 13, 14, 18, 21, 23, 25, 26, 27, and 29; mapping the most significant SNP to genes within and overlapping these QTL revealed that the most significant associations were with the 10 functional candidate genes KALRN, ZBTB20, LPP, SLA2, FI3A1, LRCH3, DNAJC6, ZDHHC14, SNX1, and HAS2. Pathway analysis failed to reveal significantly enriched biological pathways, when both bovine-specific pathway data and human ortholog data were taken into account. The existence of genetic variation for MAP susceptibility in a large data set of dairy cows signifies the potential of breeding programs for reducing MAP susceptibility. Furthermore, the identification of susceptible QTL facilitates greater biological understanding of bovine paratuberculosis and potential therapeutic targets for future investigation. The novel molecular similarities identified between bovine paratuberculosis and human inflammatory bowel disease suggest potential for human therapeutic interventions to be translated to veterinary medicine and vice versa.

SNX9 determines the surface levels of integrin β1 in vascular endothelial cells: Implication in poor prognosis of human colorectal cancers overexpressing SNX9

Angiogenesis, the formation of new blood vessels, is involved in a variety of diseases including the tumor growth. In response to various angiogenic stimulations, a number of proteins on the surface of vascular endothelial cells are activated to coordinate cell proliferation, migration, and spreading processes to form new blood vessels. Plasma membrane localization of these angiogenic proteins, which include vascular endothelial growth factor receptors and integrins, are warranted by intracellular membrane trafficking. Here, by using a siRNA library, we screened for the sorting nexin family that regulates intracellular trafficking and identified sorting nexin 9 (SNX9) as a novel angiogenic factor in human umbilical vein endothelial cells (HUVECs). SNX9 was essential for cell spreading on the Matrigel, and tube formation that mimics in vivo angiogenesis in HUVECs. SNX9 depletion significantly delayed the recycling of integrin β1, an essential adhesion molecule for angiogenesis, and reduced the surface levels of integrin β1 in HUVECs. Clinically, we showed that SNX9 protein was highly expressed in tumor endothelial cells of human colorectal cancer tissues. High-level expression of SNX9 messenger RNA significantly correlated with poor prognosis of the patients with colorectal cancer. These results suggest that SNX9 is an angiogenic factor and provide a novel target for the development of new antiangiogenic drugs.

GPCRs in Cancer: Protease-Activated Receptors, Endocytic Adaptors and Signaling

G protein-coupled receptors (GPCRs) are a large diverse family of cell surface signaling receptors implicated in various types of cancers. Several studies indicate that GPCRs control many aspects of cancer progression including tumor growth, invasion, migration, survival and metastasis. While it is known that GPCR activity can be altered in cancer through aberrant overexpression, gain-of-function activating mutations, and increased production and secretion of agonists, the precise mechanisms of how GPCRs contribute to cancer progression remains elusive. Protease-activated receptors (PARs) are a unique class of GPCRs implicated in cancer. PARs are a subfamily of GPCRs comprised of four members that are irreversibly activated by proteolytic cleavage induced by various proteases generated in the tumor microenvironment. Given the unusual proteolytic irreversible activation of PARs, expression of receptors at the cell surface is a key feature that influences signaling responses and is exquisitely controlled by endocytic adaptor proteins. Here, we discuss new survey data from the Cancer Genome Atlas and the Genotype-Tissue Expression projects analysis of expression of all PAR family member expression in human tumor samples as well as the role and function of the endocytic sorting machinery that controls PAR expression and signaling of PARs in normal cells and in cancer.

Sorting nexin-1 is a candidate tumor suppressor and potential prognostic marker in gastric cancer

Sorting nexin-1 (SNX1) is an important functional protein in cell endocytosis, efflux, protein sorting, cell signal transduction, etc; however, the expression, the role and clinical relevance of SNX1 have not been investigated in gastric cancer (GC). In this study, we first performed a bioinformatics investigation using the data obtained from The Cancer Genome Atlas (TCGA) database. The result showed that SNX1 mRNA levels were significantly lower in GC tissues than in paracancerous tissues. In a study of 150 cases of GC, including 60 cases with paired paracancerous and cancer tissues and 90 cases with detailed follow-up information, SNX1 expression was analyzed by immunohistochemistry. Our study on paired paracancerous and cancer tissues showed that SNX1 protein expression remarkably decreased in GC tissues (50/60, 83.33%). A study on 90 patients with detailed follow-up information showed that tumors with higher SNX1 protein level were correlated with better clinicopathologic stages (p = 0.0285), nodal status (p = 0.0286), smaller tumor sizes (p = 0.0294) and a better survival rate in patients with GC (p = 0.0245). Univariate analysis of the 90 patients with GC showed that low-level SNX1 was significantly correlated with decreased overall survival of GC patients (p = 0.008), and associated with a relatively higher cumulative hazard of death. Exogenous expression of SNX1 inhibited the growth, migration, invasion and promoted the apoptosis and enhanced the sensitivity of GC cells to the chemotherapeutic drug 5-Fluorouracil (5-Fu) in vitro, while knockdown of SNX1 by short hairpin RNA (shRNA) significantly promoted the growth, migration, invasion and reduced the apoptosis and the sensitivity of GC cells to 5-Fu. SNX1 also showed to influence the levels of epithelial-mesenchymal transition markers including Vimentin, Snail, and E-cadherin in GC cells in vitro. Taken together, we propose here that SNX1 serves as a tumor suppressor and prognostic marker that reduces tumor cell malignancy for GC.

Up-regulated expression of SNHG6 predicts poor prognosis in colorectal cancer

Long non-coding RNAs (lncRNAs) have been shown to play important roles in tumor formation and development. Small nucleolar RNA host gene 6 (SNHG6) is a recently identified cancer-related lncRNA, and its role in colorectal cancer (CRC) remains to be explored. The aim of this study was to evaluate the expression and function of SNHG6 in CRC. The expression of SNHG6 was detected by real time quantitative RT-PCR (qRT-PCR) in 74 CRC tissues and matched noncancerous tissues (NCTs). Relationships between the expression levels of SNHG6 and various clinicopathological features were analyzed by Chi-square test. The Kaplan-Meier method and log-rank test were applied to compare the survival distribution between different groups. CCK8 assay and colony formation assay were used to measure the effect of SNGH6 on cell proliferation. Flow cytometric analysis was performed to measure the effect of SNHG6 on cell cycle and apoptosis. Our results showed that SNHG6 was up-regulated more than 1.5-fold in 50.0% (37/74) of CRC tissues compared with paired NCTs (P < 0.0001). High level of SNHG6 expression was strongly associated with advanced tumor stage (P = 0.026) and predicted poor prognosis of CRC (P = 0.0215). The Cox proportional hazards model demonstrated that SNHG6 expression was an independent prognostic factor for CRC (HR, 2.568; 95% CI, 1.055-6.252; P = 0.038). Furthermore, SNHG6 knockdown by siRNA could inhibit cell proliferation, cell cycle progression, and induce apoptosis. Taken together, SNHG6 functions as an oncogene in CRC and appears as a novel prognositic factor for CRC patients.

Salidroside could enhance the cytotoxic effect of L‑OHP on colorectal cancer cells

Evidence has suggested that salidroside inhibits the proliferation and invasion of renal clear cell, lung, breast, and colon cancer. However, effect of salidroside on colorectal cancer (CRC) cells against oxaliplatin (L-OHP) resistance remains unclear. In the present study, the CRC HT-29 cell line and L-OHP resistance HT-29/L-OHP cell line were used to evaluate the effect, and mechanism of salidroside on L-OHP resistance. The results demonstrated that the activity of HT-29 cells was lower compared with that of HT-29/L-OHP cells following L-OHP intervention, and was accompanied with varied expression levels of drug resistant proteins. The combination of salidroside and L-OHP weakened cell activity significantly compared single utilization. Compared with the control group, salidroside intervention resulted in a higher percentage of HT-29/L-OHP cells in the G₀/G₁ stage, and reduced percentage in the G₂/M stage, but no significant variation in the S stage. The HT-29/L-OHP cells exhibited increased apoptosis rates and caspase-3 activity, but decreased metastatic, and invasive abilities following salidroside intervention. Quantitative polymerase chain reaction and western blot analysis detected variations in the expression levels of associated genes in HT-29/L-OHP cells following salidroside intervention. In all, the results of the present study revealed that salidroside is able to decrease the activity and invasive capacity of HT-29/L-OHP cells, and treatment with salidroside is associated with increased apoptosis of cancer cells through the regulation of certain genes.

Caspase-mediated proteolysis of the sorting nexin 2 disrupts retromer assembly and potentiates Met/hepatocyte growth factor receptor signaling

The unfolding of apoptosis involves the cleavage of hundreds of proteins by the caspase family of cysteinyl peptidases. Among those substrates are proteins involved in intracellular vesicle trafficking with a net outcome of shutting down the crucial processes governing protein transport to organelles and to the plasma membrane. However, because of the intertwining of receptor trafficking and signaling, cleavage of specific proteins may lead to unintended consequences. Here we show that in apoptosis, sorting nexin 1 and 2 (SNX1 and SNX2), two proteins involved in endosomal sorting, are cleaved by initiator caspases and also by executioner caspase-6 in the case of SNX2. Moreover, SNX1 is cleaved at multiple sites, including following glutamate residues. Cleavage of SNX2 results in a loss of association with the endosome-to-trans-Golgi network transport protein Vps35 and in a delocalization from endosomes of its associated partner Vps26. We also demonstrate that SNX2 depletion causes an increase in hepatocyte growth factor receptor tyrosine phosphorylation and Erk1/2 signaling in cells. Finally, we show that SNX2 mRNA and protein levels are decreased in colorectal carcinoma and that lower SNX2 gene expression correlates with an increase in cancer patient mortality. Our study reveals the importance to characterize the cleavage fragments produced by caspases of specific death substrates given their potential implication in the mechanism of regulation of physiological (signaling/trafficking) pathways or in the dysfunction leading to pathogenesis.