Clinical significance of SPARC in esophageal squamous cell carcinoma

SPARC: a potential target for functional nanomaterials and drugs

Secreted protein acidic and rich in cysteine (SPARC), also termed osteonectin or BM-40, is a matricellular protein which regulates cell adhesion, extracellular matrix production, growth factor activity, and cell cycle. Although SPARC does not perform a structural function, it, however, modulates interactions between cells and the surrounding extracellular matrix due to its anti-proliferative and anti-adhesion properties. The overexpression of SPARC at sites, including injury, regeneration, obesity, cancer, and inflammation, reveals its application as a prospective target and therapeutic indicator in the treatment and assessment of disease. This article comprehensively summarizes the mechanism of SPARC overexpression in inflammation and tumors as well as the latest research progress of functional nanomaterials in the therapy of rheumatoid arthritis and tumors by manipulating SPARC as a new target. This article provides ideas for using functional nanomaterials to treat inflammatory diseases through the SPARC target. The purpose of this article is to provide a reference for ongoing disease research based on SPARC-targeted therapy.

Phase I study of cisplatin and nanoparticle albumin-bound-paclitaxel combined with concurrent radiotherapy in locally advanced esophageal squamous cell carcinoma

BACKGROUND

This phase I study aimed to assess the safety, dose-limiting toxicity (DLT), maximum tolerated dose (MTD) and preliminary effect of nanoparticle albumin-bound (nab)-paclitaxel in combination with concurrent chemoradiotherapy in patients with locally advanced esophageal squamous cell carcinoma (ESCC).

METHODS

Patients with locally advanced ESCC who were ineligible or refused surgery were enrolled. Nab-paclitaxel (60 mg/m2 , 75 mg/m2 , and 90 mg/m2 ) and cisplatin (25 mg/m2 ) were administered intravenously weekly on days 1, 8, 15, 22, and 29 on the basis of the 3 + 3 dose escalation method. The total dose of radiation was 50-64 Gy. The primary endpoint was the safety of chemotherapy.

RESULTS

The study enrolled 12 patients across three dose levels. No treatment-related deaths occurred. One patient in the 60 mg/m2 dose level occurred dose-limiting Grade 3 febrile neutropenia. No DLT was found in the 90 mg/m2 dose level thus the MTD was not reached. The phase II study's recommended dose was 75 mg/m2 based on the available preclinical and clinical data including pharmacokinetics, pharmacodynamics, efficacy, and toxicity. The frequent hematologic toxicities were leukocytopenia (Grade 1-2 of 66.7% and Grade 3-4 of 33.3%), neutropenia (Grade 1-2 of 91.7% and Grade 3-4 of 8.3%). Nonhematologic toxicities were mild and manageable. Overall response rate (ORR) of all patients achieved 100%.

CONCLUSIONS

Weekly schedule of cisplatin and nab-paclitaxel in combination with concurrent radiotherapy showed manageable toxicities and promising antitumor activity in patients with locally advanced ESCC. The recommended dose of nab-paclitaxel for further studies is 75 mg/m2 .

SPARC expression in tumor microenvironment induces partial epithelial-to-mesenchymal transition of esophageal adenocarcinoma cells via cooperating with TGF-β signaling

Secreted protein, acidic and rich in cysteine (SPARC) has been characterized as an oncoprotein in esophageal squamous cell carcinoma (ESCC), but its involvement in the pathological development of esophageal adenocarcinoma (ESAD) remains poorly understood. In this study, we aimed to explore the sources of SPARC in the tumor microenvironment (TME) and its functional role in ESAD. Bioinformatic analysis was conducted using data from The Cancer Genome Atlas (TCGA)-esophageal cancer (ESCA) and Genotype-Tissue Expression (GTEx). ESAD tumor cell line OE33 and OE19 cells were used as in vitro cell models. Results showed that SPARC upregulation was associated with unfavorable disease-specific survival (DSS) in ESAD. ESAD tumor cells (OE33 and OE19) had no detectable SPARC protein expression. In contrast, IHC staining in ESAD tumor tissues suggested that peritumoral stromal cells (tumor-associated fibroblasts and macrophages) were the dominant SPARC source in TME. Exogenous SPARC induced partial epithelial-to-mesenchymal transition of ESAD cells, reflected by reduced CDH1 and elevated ZEB1/VIM expression at both mRNA and protein levels. Besides, exogenous SPARC enhanced tumor cell invasion. When TGFBR2 expression was inhibited, the activation of TGF-β signaling induced by exogenous SPARC was impaired. However, the activating effects were rescued by overexpressing mutant TGFBR2 resistant to the shRNA sequence. Copresence of exogenous SPARC and TGF-β1 induced higher expression of mesenchymal markers and enhanced the invading capability of ESAD cells than TGF-β1 alone. In conclusion, this study suggests a potential cross-talk between ESAD tumor stromal cells and cancer cells via a SPARC-TGF-β1 paracrine network.

Downregulation of promoter methylation gene PRDM5 contributes to the development of tumor proliferation and predicts poor prognosis in gastric cancer

Background: Epigenetic aberrations of tumor suppressor genes (TSGs), particularly DNA methylation, are frequently involved in the pathogenesis of gastric cancer (GC). Previous studies have shown that PRDM5 is methylated and silenced in GC. However, the role of PRDM5 in GC progression has not been explored.

Methods: The expression and epigenetic alterations of PRDM5 in GC were analyzed in public datasets. The mRNA and protein expression of PRDM5 in fresh tissues were detected by semi-quantitative PCR and Western blot. And expression of PRDM5 in gastric paracarcinoma and carcinoma tissues from 162 patients was detected by immunohistochemistry (IHC) and assessed the association with different clinicopathological features. The prognostic value of PRDM5 in GC patients was evaluated using Kaplan-Meier plotter. We also studied promoter region methylation of PRDM5 in GC by methylation-specific PCR (MSP). The effects of PRDM5 on cell proliferation and migration were conducted by functional experiments in vitro.

Results: The expression of PRDM5 was downregulated in GC, and that was associated with poor survival and tumor progression. And PRDM5 expression was found to be an independent prognostic factor for GC. We also found that the methylation of PRDM5 promoter was closely related to the histopathological types and the progression of tumors through the public relations database. In vitro, ectopical expression of PRDM5 inhibited the growth of tumor cells, while knockdown of PRDM5 increased the proliferation and migration of tumor cells.

Conclusion: These results suggest that PRDM5 may be a novel TSG methylated in GC that plays important roles in GC development. And we found PRDM5 as a potential survival biomarker for GC, especially in well differentiated GC. PRDM5 expression was significantly correlated with tumor stage and histological type.

Identification of Key Genes and Pathways Associated With Paclitaxel Resistance in Esophageal Squamous Cell Carcinoma Based on Bioinformatics Analysis

Esophageal squamous cell carcinoma (ESCC) ranks as the fourth leading cause of cancer-related death in China. Although paclitaxel has been shown to be effective in treating ESCC, the prolonged use of this chemical will lead to paclitaxel resistance. In order to uncover genes and pathways driving paclitaxel resistance in the progression of ESCC, bioinformatics analyses were performed based on The Cancer Genome Atlas (TCGA) database and the Gene Expression Omnibus (GEO) database including GSE86099 and GSE161533. Differential expression analysis was performed in TCGA data and two GEO datasets to obtain differentially expressed genes (DEGs). Based on GSE161533, weighted gene co-expression network analysis (WGCNA) was conducted to identify the key modules associated with ESCC tumor status. The DEGs common to the two GEO datasets and the genes in the key modules were intersected to obtain the paclitaxel resistance-specific or non-paclitaxel resistance-specific genes, which were subjected to subsequent least absolute shrinkage and selection operator (LASSO) feature selection, whereby paclitaxel resistance-specific or non-paclitaxel resistance-specific key genes were selected. Ten machine learning models were used to validate the biological significance of these key genes; the potential therapeutic drugs for paclitaxel resistance-specific genes were also predicted. As a result, we identified 24 paclitaxel resistance-specific genes and 18 non-paclitaxel resistance-specific genes. The ESCC machine classifiers based on the key genes achieved a relatively high AUC value in the cross-validation and in an independent test set, GSE164158. A total of 207 drugs (such as bevacizumab) were predicted to be alternative therapeutics for ESCC patients with paclitaxel resistance. These results might shed light on the in-depth research of paclitaxel resistance in the context of ESCC progression.

ECM Remodeling in Squamous Cell Carcinoma of the Aerodigestive Tract: Pathways for Cancer Dissemination and Emerging Biomarkers

Squamous cell carcinomas (SCC) include a number of different types of tumors developing in the skin, in hollow organs, as well as the upper aerodigestive tract (UADT) including the head and neck region and the esophagus which will be dealt with in this review. These tumors are often refractory to current therapeutic approaches with poor patient outcome. The most important prognostic determinant of SCC tumors is the presence of distant metastasis, significantly correlating with low patient survival rates. Rapidly emerging evidence indicate that the extracellular matrix (ECM) composition and remodeling profoundly affect SSC metastatic dissemination. In this review, we will summarize the current knowledge on the role of ECM and its remodeling enzymes in affecting the growth and dissemination of UADT SCC. Taken together, these published evidence suggest that a thorough analysis of the ECM composition in the UADT SCC microenvironment may help disclosing the mechanism of resistance to the treatments and help defining possible targets for clinical intervention.

ECM Remodeling in Squamous Cell Carcinoma of the Aerodigestive Tract: Pathways for Cancer Dissemination and Emerging Biomarkers

Simple Summary

Local and distant metastasis of patients affected by squamous cell carcinoma of the upper aerodigestive tract predicts poor prognosis. In the latest years, the introduction of new therapeutic approaches, including targeted and immune therapies, has improved the overall survival. However, a large number of these patients do not benefit from these treatments. Thus, the identification of suitable prognostic and predictive biomarkers, as well as the discovery of new therapeutic targets have emerged as a crucial clinical need. In this context, the extracellular matrix represents a suitable target for the development of such therapeutic tools. In fact, the extracellular matrix is composed by complex molecules able to interact with a plethora of receptors and growth factors, thus modulating the dynamic crosstalk between cancer cells and the tumor microenvironment. In this review, we summarize the current knowledge of the role of the extracellular matrix in affecting squamous cell carcinoma growth and dissemination. Despite extracellular matrix is known to affect the development of many cancer types, only a restricted number of these molecules have been recognized to impact on squamous cell carcinoma progression. Thus, we consider that a thorough analysis of these molecules may be key to develop new potential therapeutic targets/biomarkers.

Abstract

Squamous cell carcinomas (SCC) include a number of different types of tumors developing in the skin, in hollow organs, as well as the upper aerodigestive tract (UADT) including the head and neck region and the esophagus which will be dealt with in this review. These tumors are often refractory to current therapeutic approaches with poor patient outcome. The most important prognostic determinant of SCC tumors is the presence of distant metastasis, significantly correlating with low patient survival rates. Rapidly emerging evidence indicate that the extracellular matrix (ECM) composition and remodeling profoundly affect SSC metastatic dissemination. In this review, we will summarize the current knowledge on the role of ECM and its remodeling enzymes in affecting the growth and dissemination of UADT SCC. Taken together, these published evidence suggest that a thorough analysis of the ECM composition in the UADT SCC microenvironment may help disclosing the mechanism of resistance to the treatments and help defining possible targets for clinical intervention.

Identification of lncRNA-associated differential subnetworks in oesophageal squamous cell carcinoma by differential co-expression analysis

Differential expression analysis has led to the identification of important biomarkers in oesophageal squamous cell carcinoma (ESCC). Despite enormous contributions, it has not harnessed the full potential of gene expression data, such as interactions among genes. Differential co-expression analysis has emerged as an effective tool that complements differential expression analysis to provide better insight of dysregulated mechanisms and indicate key driver genes. Here, we analysed the differential co-expression of lncRNAs and protein-coding genes (PCGs) between normal oesophageal tissue and ESCC tissues, and constructed a lncRNA-PCG differential co-expression network (DCN). DCN was characterized as a scale-free, small-world network with modular organization. Focusing on lncRNAs, a total of 107 differential lncRNA-PCG subnetworks were identified from the DCN by integrating both differential expression and differential co-expression. These differential subnetworks provide a valuable source for revealing lncRNA functions and the associated dysfunctional regulatory networks in ESCC. Their consistent discrimination suggests that they may have important roles in ESCC and could serve as robust subnetwork biomarkers. In addition, two tumour suppressor genes (AL121899.1 and ELMO2), identified in the core modules, were validated by functional experiments. The proposed method can be easily used to investigate differential subnetworks of other molecules in other cancers.

The Matrix Revolution: Matricellular Proteins and Restructuring of the Cancer Microenvironment

The extracellular matrix (ECM) surrounding cells is indispensable for regulating their behavior. The dynamics of ECM signaling are tightly controlled throughout growth and development. During tissue remodeling, matricellular proteins (MCP) are secreted into the ECM. These factors do not serve classical structural roles, but rather regulate matrix proteins and cell-matrix interactions to influence normal cellular functions. In the tumor microenvironment, it is becoming increasingly clear that aberrantly expressed MCPs can support multiple hallmarks of carcinogenesis by interacting with various cellular components that are coupled to an array of downstream signals. Moreover, MCPs also reorganize the biomechanical properties of the ECM to accommodate metastasis and tumor colonization. This realization is stimulating new research on MCPs as reliable and accessible biomarkers in cancer, as well as effective and selective therapeutic targets.

Downregulation of SPARC Expression Decreases Cell Migration and Invasion Involving Epithelial-Mesenchymal Transition through the p-FAK/p-ERK Pathway in Esophageal Squamous Cell Carcinoma

Purpose: Secreted protein acidic and rich in cysteine (SPARC) is an extracellular glycoprotein overexpressed in various malignancies, including esophageal squamous cell carcinoma (ESCC), and is involved in tumor development and progression. This study was initially designed to investigate the biological roles of SPARC in ESCC cell lines by silencing SPARC expression. Methods: The expression of SPARC was examined in eight human ESCC cell lines. Eca109 and HKESC cell lines with high SPARC expression were selected and transiently transfected with SPARC-targeted small interfering RNAs (siRNAs) and subsequently evaluated its impact on cell proliferation, migration and invasion in vitro, as well as the underlying mechanism. Results: Knockdown of SPARC by the specified siRNAs in Eca109 and HKESC cell lines resulted in dramatically downregulation of SPARC expression, and significantly decreased cell migration and invasion involving epithelial-mesenchymal transition (EMT) in vitro. Moreover, SPARC-targeted siRNA reduced the activation of phosphorylated focal adhesion kinase (p-FAK) and extracellular regulated protein kinase (p-ERK). Furthermore, downregulation of either FAK or SPARC expression with specified siRNAs inhibited the phosphorylation of ERK and inhibited cell migration and invasion. However, decreased SPARC expression showed no impact on cell proliferation, survival or apoptosis of Eca109 and HKESC cells when comparing to control transfected groups. Conclusions: These results demonstrated that downregulation of SPARC could decrease cell migration and invasion involving EMT via the p-FAK/p-ERK pathway that might serve as a novel therapeutic target against ESCC.

Integrated Bioinformatics Analysis Identifies Hub Genes Associated with the Pathogenesis and Prognosis of Esophageal Squamous Cell Carcinoma

Esophageal squamous cell carcinoma (ESCC) accounts for over 90% of all esophageal tumors. However, the molecular mechanism underlying ESCC development and prognosis remains unclear, and there are still no effective molecular biomarkers for diagnosing or predicting the clinical outcome of patients with ESCC. Here, using bioinformatics analyses, we attempted to identify potential biomarkers and therapeutic targets for ESCC. Differentially expressed genes (DEGs) between ESCC and normal esophageal tissue samples were obtained through comprehensive analysis of three publicly available gene expression profile datasets from the Gene Expression Omnibus database. The biological roles of the DEGs were identified by Gene Ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis. Moreover, the Cytoscape 3.7.1 platform and subsidiary tools such as Molecular Complex Detection (MCODE) and CytoHubba were used to visualize the protein-protein interaction (PPI) network of the DEGs and identify hub genes. A total of 345 DEGs were identified between normal esophageal and ESCC samples, which were enriched in the KEGG pathways of the cell cycle, endocytosis, pancreatic secretion, and fatty acid metabolism. Two of the highest scoring models were selected from the PPI network using Molecular Complex Detection. Moreover, CytoHubba revealed 21 hub genes with a valuable influence on the progression of ESCC in these patients. Among these, the high expression levels of five genes-SPP1, SPARC, BGN, POSTN, and COL1A2-were associated with poor disease-free survival of ESCC patients, as indicated by survival analysis. Taken together, we identified that elevated expression of five hub genes, including SPP1, is associated with poor prognosis in ESCC patients, which may serve as potential prognostic biomarkers or therapeutic target for ESCC.

Immunohistochemical analysis of the expression of cancer-associated fibroblast markers in esophageal cancer with and without neoadjuvant therapy

Esophageal carcinoma (EC) is one of the most aggressive human malignancies with high rates of resistance to conventional anticancer treatment. Cancer-associated fibroblasts (CAFs) are an important part of the tumor microenvironment and associated with tumor progression. COL11A1, SPARC, and CD90 have been identified as rather specific CAF markers, with COL11A1 expression particularly shown to influence response to chemotherapy. We investigated the impact of CAFs in esophageal cancer with a special focus on response to neoadjuvant treatment (nTX). Two collections of esophageal carcinomas were investigated: 164 cases treated with primary resection and 256 cases receiving nTX before resection. The expression of CAF markers was determined using next-generation tissue microarray (ngTMA®) technology and immunohistochemistry. The presence of COL11A1 and SPARC in fibroblasts within both primary resected cases and nTX-treated cases was associated with unfavorable clinicopathological variables such as higher (y)pT category and lymphatic invasion (p<0.001 each). The presence of COL11A1-positive CAFs was associated with worse overall survival in primary resected cases (HR: 2.162, p = 0.004, CI 95% 1.275-3.686). While in tumors showing regression after nTX, COL11A1-positive CAFs were detected less frequently, SPARC-positive CAFs were enriched after nTX, in both responding and non-responding patients (p < 0.001). Our results support the concept of CAFs as an important factor of tumor promotion and maintenance in EC. The population of CAFs increases with tumor progression and decreases, partly depending on the subtype, after regression following nTX. CAFs may serve as potential target for future therapeutic approaches for these highly aggressive tumors.

Identification of key genes involved in the development and progression of early-onset colorectal cancer by co-expression network analysis

A number of studies have revealed that there is an increasing incidence of early-onset colorectal cancer (CRC) in young adults (before the age of 50 years) and a progressive decline in CRC among older patients, after the age of 50 years (late-onset CRC). However, the etiology of early-onset CRC is not fully understood. The aim of the present study was to identify key genes associated with the development of early-onset CRC through weighted gene co-expression network analysis (WGCNA). The GSE39582 dataset was downloaded from the Gene Expression Omnibus database, and the data profiles of tissues from patients diagnosed before the age of 50 years were selected. The top 10,000 genes with the highest variability were used to construct the WGCNA. Hub genes were identified from the modules associated with clinical traits using gene significance >0.2 and module membership >0.8 as the cut-off criteria. Gene Ontology and pathway analyses were subsequently performed on the hub genes and a protein-protein interaction network (PPI) was constructed. The diagnostic value of module hub genes with a degree score >5 in the PPI network was verified in samples from patients with CRC diagnosed before the age of 50 years obtained from The Cancer Genome Atlas. Eight co-expressed gene modules were identified in the WGCNA and two modules (blue and turquoise) were associated with the tumor-node-metastasis stage. A total of 140 module hub genes were identified and found to be enriched in 'mitochondrial large ribosomal subunit', 'structural constituent of ribosome', 'poly (A) RNA binding', 'collagen binding', 'protein ubiquitination' and 'ribosome pathway'. Twenty-six module hub genes were found to have a degree score >5 in the PPI network, seven of which [secreted protein acidic and cysteine rich (SPARC), decorin (DCN), fibrillin 1 (FBN1), WW domain containing transcription regulator 1 (WWTR1), transgelin (TAGLN), DEAD-box helicase 28 (DDX28) and cold shock domain containing C2 (CSDC2)], had good prognostic values for patients with early-onset CRC, but not late-onset CRC. Therefore, SPARC, DCN, FBN1, WWTR1, TAGLN, DDX28 and CSDC2 may contribute to the development of early-onset CRC and may serve as potential diagnostic biomarkers.

miR-30b-5p acts as a tumor suppressor microRNA in esophageal squamous cell carcinoma

Background

To study miR-30b-5p expression in esophageal squamous cell carcinoma (ESCC) by comparisons between tumor tissues and matched adjacent non-cancerous tissues to elucidate the correlation between miR-30b-5p expression and ESCC clinical parameters, and to explore the signaling pathways associated with miR-30b-5p and key target genes.

Methods

Clinical data, cancer tissues, and adjacent non-cancerous tissues of 32 patients diagnosed with ESCC were collected from Taizhou Hospital of Zhejiang Province. The expression levels of miR-30b-5p were determined by real-time polymerase chain reaction (RT-PCR). mRNA data for ESCC tissues and normal tissues, and clinical materials of patients with ESCC were obtained from the Gene Expression Omnibus (GEO) database and The Cancer Genome Atlas (TCGA). Associations between miR-30b-5p expression and clinical features of patients with ESCC and overall survival were explored. A bioinformatics analysis was performed to determine the pathways and key miR-30b-5p targets associated with ESCC. Additionally, a cytological experiment was performed to evaluate the biological functions of miR-30b-5p. Finally, correlations between miR-30b-5p and key targets involved in PI3K/Akt signaling pathways were validated by western blotting.

Results

The expression level of miR-30b-5p in the 32 ESCC tissues was significantly lower than that in adjacent normal tissues (P<0.01) and was significantly disparate in the T stage, with higher expression in T1 than in T2 (P<0.05). Among the patients with higher expression levels of miR-30b-5p in ESCC tissues than in adjacent normal tissues, patients with higher expression of miR-30b-5p had a better prognosis (P<0.05). An analysis of gene chip data from the GEO database showed similar results. A gene enrichment analysis indicated a series of pathways that may be associated with the downregulation of miR-30b-5p, including focal adhesion, ECM-receptor interaction, and PI3K/Akt signaling pathways. Seven key target genes (PDGFRB, VIM, ITGA5, ACTN1, THBS2, SERPINE1, and RUNX2) were identified; these were found to be upregulated in ESCC tissues and were negatively correlated with miR-30b-5p. Functional experiments showed that miR-30b-5p attenuated migration (P<0.01) and invasion (P<0.05) in the Eca109 cell line. Moreover, the levels of ITGA5, PDGFRB, p-PI3K, and p-AKT, which are involved in the PI3K/Akt signaling pathway, were decreased in the miR-30b-5p-overexpressing Eca109 cell line.

Conclusions

Upregulated miR-30b-5p may inhibit migration and invasion in ESCC by targeting ITGA5, PDGFRB, and signaling pathways, such as PI3K/Akt, involved in ESCC regulation. Our results indicate that miR-30b-5p plays an important role in the occurrence and progression of ESCC and is a potential therapeutic target.

Low expression of SPARC in gastric cancer-associated fibroblasts leads to stemness transformation and 5-fluorouracil resistance in gastric cancer

Background

The aim of the present study was to clarify the correlations between SPARC expression in gastric cancer-associated fibroblasts (GCAFs) and the prognosis of patients with gastric cancer and to elucidate the role of GCAF-derived SPARC in stemness transformation and 5-fluorouracil resistance in gastric cancer.

Methods

One hundred ninety-two patients were enrolled in the present study. SPARC expression levels were evaluated by immunohistochemical staining. Primary GCAFs were obtained and cultured from cancer patients for in vitro study, and a lentivirus infection method was employed to knock down SPARC expression in GCAFs. The stemness phenotype and 5-fluorouracil (5-FU) response of gastric cancer cells were assessed via a 3D co-culture model. The apoptotic status and stemness alterations were monitored by flow cytometry and western blotting. Additionally, label-free quantification proteomics was used to identify the differentially expressed proteins and potential pathways in gastric cancer cells treated with GCAF-derived SPARC.

Results

Low expression of GCAF-derived SPARC was associated with decreased differentiation and reduced 5-year overall survival and was an independent predictive factor for prognosis in gastric cancer. The 3D tumour growth and 5-FU resistance abilities of gastric cancer cells were elevated after treatment with GCAFs with SPARC knockdown relative to these abilities in negative control cells. Additionally, suppressing SPARC expression in GCAFs facilitated the phenotypic alteration of gastric cancer cells towards CD44⁺/CD24⁻ cancer stem cell (CSC)-like cells. Quantification proteomics analysis revealed that the differentially expressed proteins in gastric cancer cells were mainly involved in the AKT/mTOR and MEK/ERK signalling pathways.

Conclusions

SPARC expression in GCAFs is a useful prognostic factor in patients with gastric cancer. Low expression of GCAF-derived SPARC can lead to CSC transformation and 5-FU resistance. Additionally, the AKT/mTOR and MEK/ERK signalling pathways may participate in the malignant process.

Electronic supplementary material

The online version of this article (10.1186/s12935-019-0844-8) contains supplementary material, which is available to authorized users.