Function and mechanism of F-box proteins in gastric cancer (Review)

Identification of molecular biomarkers associated with non-small-cell lung carcinoma (NSCLC) using whole-exome sequencing

OBJECTIVES

Significant progress has been made in the treatment of patients with pulmonary adenocarcinoma (ADCA) based on molecular profiling. However, no such molecular target exists for squamous cell carcinoma (SQCC). An exome sequence may provide new markers for personalized medicine for lung cancer patients of all subtypes. The current study aims to discover new genetic markers that can be used as universal biomarkers for non-small cell lung cancer (NSCLC).

METHODS

WES of 19 advanced NSCLC patients (10 ADCA and 9 SQCC) was performed using Illumina HiSeq 2000. Variant calling was performed using GATK HaplotypeCaller and then the impacts of variants on protein structure or function were predicted using SnpEff and ANNOVAR. The clinical impact of somatic variants in cancer was assessed using cancer archives. Somatic variants were further prioritized using a knowledge-driven variant interpretation approach. Sanger sequencing was used to validate functionally important variants.

RESULTS

We identified 24 rare single-nucleotide variants (SNVs) including 17 non-synonymous SNVs, and 7 INDELs in 18 genes possibly linked to lung carcinoma. Variants were classified as known somatic (n= 10), deleterious (n= 8), and variant of uncertain significance (n= 6). We found TBP and MPRIP genes exclusively associated with ADCA subtypes, FBOX6 with SQCC subtypes and GPRIN2, KCNJ18 and TEKT4 genes mutated in all the patients. The Sanger sequencing of 10 high-confidence somatic SNVs showed 100% concordance in 7 genes, and 80% concordance in the remaining 3 genes.

CONCLUSIONS

Our bioinformatics analysis identified KCNJ18, GPRIN2, TEKT4, HRNR, FOLR3, ESSRA, CTBP2, MPRIP, TBP, and FBXO6 may contribute to progression in NSCLC and could be used as new biomarkers for the treatment. The mechanism by which GPRIN2, KCNJ12, and TEKT4 contribute to tumorigenesis is unclear, but our results suggest they may play an important role in NSCLC and it is worth investigating in future.

Fbxo45 promotes the malignant development of esophageal squamous cell carcinoma by targeting GGNBP2 for ubiquitination and degradation

Esophageal squamous cell carcinoma (ESCC) is one of the most common and deadly cancers. Fbxo45, a substrate recognition subunit of E3 ligase, is critically involved in tumorigenesis and tumor progression. However, the function of Fbxo45 and the underlying mechanisms have not been elucidated in ESCC. We used cellular and molecular methods to explore the molecular basis of Fbxo45-mediated ESCC development. We found that ectopic overexpression of Fbxo45 promoted the growth of Kyse-150, Kyse30 and ECA-109 cells and inhibited the apoptosis. Moreover, overexpression of Fbxo45 promoted the migration and invasion of ESCC cells. Consistently, knockdown of Fbxo45 exhibited the opposite effects on ESCC cells. Mechanistically, we observed that Fbxo45 binds to GGNBP2 via its SPRY domain and targets GGNBP2 for ubiquitination and degradation. GGNBP2 overexpression exhibited anticancer activity in ESCC cells. Furthermore, Fbxo45 exerted its functions by regulating GGNBP2 stability in ESCC cells. Notably, overexpression of Fbxo45 facilitated tumor growth in mice. Strikingly, Fbxo45 was highly expressed in ESCC tissues, and GGNBP2 had a lower expression in ESCC specimens. High expression of Fbxo45 and low expression of GGNBP2 were associated with poor prognosis in ESCC patients. Fbxo45 was negatively correlated with GGNBP2 expression in ESCC tissues. Therefore, Fbxo45 serves as an oncoprotein to promote ESCC tumorigenesis by targeting the stability of the tumor suppressor GGNBP2 in ESCC.

Comprehensive Study of Human FBXW7 Deleterious nsSNP's Functional Inference and Susceptibility to Gynaecological Cancer

Cancer is one of the world's major causes of mortality, and it plays a most important role in the world's declining life expectancy. F-box and WD-40 domain protein 7 (FBXW7), a typical participant of the F-box family of proteins, has been considered as an anti-tumor protein and one of the maximum deregulated ubiquitin-proteasome system proteins in uterine carcinosarcoma, endometrial clear cell carcinoma and cervical carcinoma with the greatest prevalence of alterations. FBXW7 variants with known clinical significance, as well as non-synonymous single nucleotide polymorphisms (nsSNPs) in the F-Box and WD40 domains, were evaluated using functionality prediction web resources. Upon analysing the seventy-three deleterious nsSNP's impact on protein stability and function, we identified that forty-one nsSNPs of WD40 domain and three of F-Box domain imply decreased stability of the FBXW7 structure. Next to TP53 and PTEN, FBXW7 was reported with the highest percentage of arginine substitution among mutations related to cancer. The current research concentrated on two arginine residue locations (Arg465, Arg505) within the WD40-repeat domain, which is vital for substrate binding. Computational analysis revealed significant deviation in stability and structural configuration of mutants R505L, R465H, R465P, R505G, R505C, R465C, R505S and R505L structures. Protein-protein interaction network of FBXW7 populated with promising hub proteins NOTCH1, c-Myc, CCNE1, STYX, KLG5, SREB1, NFKB2, SKP1 and CUL1; thus, alteration in the FBXW7 leads to aberration in their signalling pathways as well as their substrate binding ability makes this protein as attractive target for personalized therapeutic intervention.

Roles of E3 ubiquitin ligases in gastric cancer carcinogenesis and their effects on cisplatin resistance

Although gastric cancer (GC) is one of the most common cancers with high incidence and mortality rates, its pathogenesis is still not elucidated. GC carcinogenesis is complicated and involved in the activation of oncoproteins and inactivation of tumor suppressors. The ubiquitin-proteasome system (UPS) is crucial for protein degradation and regulation of physiological and pathological processes. E3 ubiquitin ligases are pivotal enzymes in UPS, containing various subfamily proteins. Previous studies report that some E3 ligases, including SKP2, CUL1, and MDM2, act as oncoproteins in GC carcinogenesis. On the other hand, FBXW7, FBXL5, FBXO31, RNF43, and RNF180 exert as tumor suppressors in GC carcinogenesis. Moreover, E3 ligases modulate cell growth, cell apoptosis, and cell cycle; thus, it is complicated to confer cisplatin resistance/sensitivity in GC cells. The intrinsic and acquired cisplatin resistance limits its clinical application against GC. In this review, we explore oncogenic and tumor suppressive roles of E3 ligases in GC carcinogenesis and focus on the effects of E3 ligases on cisplatin resistance in GC cells, which will provide novel therapeutic targets for GC therapy, especially for cisplatin-resistant patients.

Circulating miRNAs as a Predictive Biomarker of the Progression from Prediabetes to Diabetes: Outcomes of a 5-Year Prospective Observational Study

Due to a global increase in the prevalence of type 2 diabetes mellitus (T2DM), there is an urgent need for early identification of prediabetes, as these people have the highest risk of developing diabetes. Circulating miRNAs have shown potential as progression biomarkers in other diseases. This study aimed to conduct a baseline comparison of serum-circulating miRNAs in prediabetic individuals, with the distinction between those who later progressed to T2DM and those who did not. The expression levels of 798 miRNAs using NanoString technology were examined. Spearman correlation, receiver operating characteristic (ROC) curve analysis, and logistic regression modeling were performed. Gene ontology (GO) and canonical pathway analysis were used to explore the biological functions of the miRNA target genes. The study revealed that three miRNAs were upregulated in the serum samples of patients who later progressed to T2DM. Pathway analysis showed that the miRNA target genes were mainly significantly enriched in neuronal NO synthase (nNOS) signaling in neurons, amyloid processing, and hepatic cholestasis. ROC analysis demonstrated that miR-491-5p, miR-1307-3p, and miR-298 can be introduced as a diagnostic tool for the prediction of T2DM (area under the curve (AUC) = 94.0%, 88.0%, and 84.0%, respectively). Validation by real-time quantitative polymerase chain reaction (qRT-PCR) confirmed our findings. The results suggest that circulating miRNAs can potentially be used as predictive biomarkers of T2DM in prediabetic patients.

FBXW7 in Cancer: What Has Been Unraveled Thus Far?

: The FBXW7 (F-box with 7 tandem WD40) protein encoded by the gene FBXW7 is one of the crucial components of ubiquitin ligase called Skp1-Cullin1-F-box (SCF) complex that aids in the degradation of many oncoproteins via the ubiquitin-proteasome system (UPS) thus regulating cellular growth. FBXW7 is considered as a potent tumor suppressor as most of its target substrates can function as potential growth promoters, including c-Myc, Notch, cyclin E, c-JUN, and KLF5. Its regulators include p53, C/EBP-δ, Numb, microRNAs, Pin 1, Hes-5, BMI1, Ebp2. Mounting evidence has indicated the involvement of aberrant expression of FBXW7 for tumorigenesis. Moreover, numerous studies have also shown its role in cancer cell chemosensitization, thereby demonstrating the importance of FBXW7 in the development of curative cancer therapy. This comprehensive review emphasizes on the targets, functions, regulators and expression of FBXW7 in different cancers and its involvement in sensitizing cancer cells to chemotherapeutic drugs.

Coexpression modules constructed by weighted gene co-expression network analysis indicate ubiquitin-mediated proteolysis as a potential biomarker of uveal melanoma

Uveal melanoma (UM) is a tumor that affects individuals throughout the world. Although gene expression analysis of UM has been performed previously, systemic co-expression analysis for this type of cancer remains lacking. Microarray data of UM samples was obtained from the Genome Expression Omnibus (dataset GSE44295). Co-expression modules were built by weighted gene co-expression network analysis. Functional enrichment analysis was performed on the co-expressed genes from important modules. Seven co-expression modules were constructed from the 5,000 genes gathered from the 58 human UM samples. The number of genes in these modules ranged from 73 to 3,051, with the mean number being 711. There was a marked difference in interactions among pairwise modules. Functional enrichment analysis demonstrated that module 2 was mainly enriched in pathways associated with the regulation of transcription. Additionally, modules 2–4 were significantly enriched in the ubiquitin mediated proteolysis pathway, suggesting it could serve a critical role in the occurrence and development of UM. The findings of the present study present a framework of co-expressed gene modules for human UM and provide an improved understanding of these modules at a functional level. Understanding the molecular mechanism and cellular pathways involved in pathogenesis of UM is extremely important for the development of more effective diagnostic and therapeutic strategies.

Xanthohumol, a prenylated flavonoid from Hops, exerts anticancer effects against gastric cancer in vitro

Xanthohumol (Xn), a prenylated flavonoid isolated from Hops (Humulus lupulus L.), has demonstrated potent anticancer activity in multiple types of cancer. However, the effect of Xn on gastric cancer (GC) remains unknown. The aim of the present study was to investigate the effect of Xn on GC cell proliferation, apoptosis and metastasis. It was observed that Xn decreased the viability of GC cells, with very low or no toxicity to normal gastric epithelial cells GES‑1 at a concentration of 1‑100 µM. The proliferation of AGS cells was inhibited by Xn, as indicated by the decreased number of EdU‑positive cells. Xn treatment increased the number of apoptotic cells, downregulated the expression of Bcl‑2 and upregulated the expression of Bax, suggesting induction of apoptosis. The results from the wound healing and Transwell assays indicated that Xn suppressed AGS cell metastasis. Moreover, Xn induced reactive oxygen species (ROS) overproduction and inhibited nuclear factor (NF)‑κB signaling in AGS cells, which was reversed by the ROS inhibitor N‑acetylcysteine (NAC). NAC suppressed the effect of Xn on the proliferation, apoptosis and metastasis of AGS cells. Taken together, these results suggest that Xn exerts anticancer effects against GC via induction of ROS production and subsequent inhibition of NF‑κB signaling. Therefore, Xn may be a promising candidate treatment against GC progression.

Influence of single nucleotide polymorphisms in pri-miR-124-1 and STAT3 genes on gastric cancer susceptibility

INTRODUCTION

MicroRNAs (miRNAs) are small ribonucleic acids that modulate the expression of downstream target genes. There is considerable evidence of their involvement in many malignancies, such as oesophageal and gastric. We hypothesised altered expressions of pri-miR-124-1 rs531564 and STAT3 rs1053023 polymorphisms in gastric cancer.

MATERIALS AND METHODS

Genomic DNA was extracted from peripheral blood of 250 patients with gastric cancer and 310 healthy individuals. The RFLP method was applied for determination of pri-miR-124 polymorphism and the AS-PCR method for STAT3 polymorphism.

RESULTS

The distribution of rs531564 genotypes in cases and controls was different: the G allele carriers had a reduced gastric cancer risk (OR = 0.62; 95%CI = 0.49-0.80, P = 0.0002). Presence of the minor allele of STAT3 (rs1053023) was linked with higher risk of gastric cancer (OR = 2.29; 95% CI = 1.79-2.93, P < 0.0001). Compared with the most frequent haplotype C-G [the SNP order was pri-miR-124-1 (rs531564) and STAT3 (rs1053023)] in controls, C-A haplotype was associated with a significantly increased risk of gastric cancer (OR = 2.28; 95%CI = 1.64-3.09, P < 0.0001).

CONCLUSION

There is a strong link between pri-miR-124-1 rs531564 and STAT3 rs1053023 and gastric cancer that may be pathogenic, and so worthy of further investigation.

F-box proteins involved in cancer-associated drug resistance

The ubiquitin proteasome system (UPS) regulated human biological processes through the appropriate and efficient proteolysis of cellular proteins. F-box proteins are the vital components of SKP1-CUL1-FBP (SCF)-type E3 ubiquitin ligases that determine substrate specificity. As F-box proteins have the ability to control the degradation of several crucial protein targets associated with drug resistance, the dysregulation of these proteins may lead to induction of chemoresistance in cancer cells. Chemotherapy is one of the most conventional therapeutic approaches of treatment of patients with cancer. However, its exclusive application in clinical settings is restricted due to the development of chemoresistance, which typically results treatment failure. Therefore, overcoming drug resistance is considered as one of the most critical issues that researchers and clinician associated with oncology face. The present review serves to provide a comprehensive overview of F-box proteins and their possible targets as well as their correlation with the chemoresistance and chemosensitization of cancer cells. The article also presents an integrated representation of the complex regulatory mechanisms responsible for chemoresistance, which may lay the foundation to explore sensible candidate drugs for therapeutic intervention.

Mannose receptor as a potential biomarker for gastric cancer: a pilot study

BACKGROUND

The mannose receptor is an immune adhesion molecule mainly expressed on the surface of antigen-presenting cells such as nonmature dendritic cells and macrophages. This study aimed to investigate mannose receptor expression and its predictive role in papillary gastric cancer patients.

METHODS

The expression of the mannose receptor was measured in 120 samples of gastric cancer tissues and corresponding paracarcinoma tissues, by immunohistochemical and quantitative real-time PCR analysis. The relationships between mannose receptor expression and clinicopathological features of gastric cancer patients were analyzed.

RESULTS

The expression rate of the mannose receptor in gastric cancer cells was 45.8% (54/120), significantly higher than that in the paracarcinoma tissue (20.0%, 36/120) (χ2 = 6.286, p = 0.012). High expression of the mannose receptor was closely related to tumor size, T stage, N stage and Union for International Cancer Control (UICC) stage of gastric cancer (p<0.05). A Kaplan-Meier survival model indicated that the survival of patients in the high-expression mannose receptor group was significantly shorter than in the low-expression mannose receptor group (p<0.05). Cox regression analysis showed that high mannose receptor expression was an independent predictor for the prognosis of patients with gastric cancer.

CONCLUSIONS

High mannose receptor expression indicates poor prognosis for gastric cancer patients. The mannose receptor may be an important molecular marker for gastric cancer prognosis.

F-box protein FBXL2 inhibits gastric cancer proliferation by ubiquitin-mediated degradation of forkhead box M1

F-box/LRR-repeat protein 2 (FBXL2), a component of Skp-Cullin-F box (SCF) ubiquitin E3 ligase, has been shown to inhibit tumorigenesis by targeting and ubiquitinating several oncoproteins. However, its role in gastric cancer remains poorly understood. Here, by tandem mass spectrometry, we show that FBXL2 interacts with forkhead box M1 (FoxM1) transcription factor. As a result, FBXL2 promotes ubiquitination and degradation of FoxM1 in gastric cancer cells. Furthermore, overexpression of FBXL2 inhibits, while its deficiency promotes cell proliferation and invasion. Expression levels of cell-cycle regulators (Cdc25B and p27), which are down-stream target effectors of FoxM1, are also regulated by FBXL2. Therefore, our results uncover a previous unknown network involving FBXL2 and FoxM1 in the regulation of gastric cancer growth.