The changing face of gastric cancer: epidemiologic trends and advances in novel therapies

Machine learning-based integration develops a disulfidptosis-related lncRNA signature for improving outcomes in gastric cancer

Gastric cancer remains one of the deadliest cancers globally due to delayed detection and limited treatment options, underscoring the critical need for innovative prognostic methods. Disulfidptosis, a recently discovered programmed cell death triggered by disulphide stress, presents a fresh avenue for therapeutic exploration. This research examines disulfidptosis-related long noncoding RNAs (DRLs) in gastric cancer, with the goal of leveraging these lncRNAs as potential markers to enhance patient outcomes and treatment approaches. Comprehensive genomic and clinical data from stomach adenocarcinoma (STAD) were obtained from The Cancer Genome Atlas (TCGA). Employing least absolute shrinkage and selection operator (LASSO) regression analysis, a prognostic model was devised incorporating five key DRLs to forecast survival rates. The effectiveness of this model was validated using Kaplan-Meier survival plots, receiver operating characteristic (ROC) curves, and extensive functional enrichment studies. The importance of select lncRNAs and the expression variability of genes tied to disulfidptosis were validated via quantitative real-time PCR (qRT-PCR) and Western blot tests, establishing a solid foundation for their prognostic utility. Analyses of functional enrichment and tumour mutation burden highlighted the biological importance of these DRLs, connecting them to critical cancer pathways and immune responses. These discoveries broaden our comprehension of the molecular framework of gastric cancer and bolster the development of tailored treatment plans, highlighting the substantial role of DRLs in clinical prognosis and therapeutic intervention.

The use of indocyanine green and near-infrared fluorescence in the detection of metastatic lymph nodes during oesophageal and gastric cancer resection: a systematic review and meta-analysis

BACKGROUND

Lymph node status is one of the most important prognosticating factors for patients afflicted by oesophageal cancer (OC) and gastric cancer (GC), and lymphadenectomy during surgery is therefore an essential step to ensure complete oncological resection and accurate disease staging. Intraoperative lymph node visualisation using near-infrared fluorescence (NIRF) and indocyanine green (ICG) tracing has been postulated to improve the overall lymph node yield, and to ensure the appropriate radicality, but its usefulness in the detection of metastatic lymph nodes remains unclear.

METHODS

We conducted a systematic review and meta-analysis of the relevant literature to ascertain the accuracy of ICG-guided lymphadenectomy in the detection of metastatic nodes in OC and GC. The primary outcomes were the sensitivity, specificity and diagnostic odds ratio of ICG-guided lymphadenectomy. Secondary outcomes included measurement of the effect of prior neoadjuvant chemotherapy (NAC), tumour characteristics and method of ICG administration. Summary receiver operator characteristic (SROC) curves were built to illustrate the relationship between the sensitivity of ICG and false positive rate.

RESULTS

From an initial search of 6,302 articles, 15 studies met the criteria for inclusion, incorporating 4,004 patients. The pooled sensitivity for metastatic node detection was 69.1% (95% CI 56.5-79.3%), specificity 47.4% (38.0-56.9%), and DOR 2.02 (1.40-2.92). The SROC curve for diagnostic test accuracy yielded an area under the curve of 0.60. The use of NAC adversely affected the sensitivity of ICG 74.7% [59.2-85.8%] without NAC; 52.8% [43.6-61.9%] with NAC, p = 0.018). No significant difference in efficacy was demonstrated between pathological 'T' stage, or ICG administration method.

CONCLUSION

Our findings suggest that the oncological benefits of NIRF and ICG in the context of lymphadenectomy in OC and GC are limited, and that surgeons risk omitting a significant proportion of metastatic nodes if this technique is solely relied upon.

Multi-omics analysis of Helicobacter pylori-associated gastric cancer identifies hub genes as a novel therapeutic biomarker

Helicobacter pylori infection is one of the most common gastric pathogens; however, the molecular mechanisms driving its progression to gastric cancer remain poorly understood. This study aimed to identify the key transcriptomic drivers and therapeutic targets of H. pylori-associated gastric cancer through an integrative transcriptomic analysis. This analysis integrates microarray and RNA-seq datasets to identify significant differentially expressed genes (DEGs) involved in the progression of H. pylori-associated gastric cancer. In addition to independent analyses, data were integrated using ComBat to detect consistent expression patterns of hub genes. This approach revealed distinct clustering patterns and stage-specific transcriptional changes in common DEGs across disease progression, including H. pylori infection, gastritis, atrophy, and gastric cancer. Genes such as TPX2, MKI67, EXO1, and CTHRC1 exhibited progressive upregulation from infection to cancer, highlighting involvement in cell cycle regulation, DNA repair, and extracellular matrix remodeling. These findings provide insights into molecular shifts linking inflammation-driven infection to malignancy. Furthermore, network analysis identified hub genes, including CXCL1, CCL20, IL12B, and STAT4, which are enriched in immune pathways such as chemotaxis, leukocyte migration, and cytokine signaling. This emphasizes their role in immune dysregulation and tumor development. Expression profiling demonstrated the upregulation of hub genes in gastric cancer and stage-specific changes correlating with disease progression. Finally, drug-gene interaction analysis identified therapeutic opportunities, with hub genes interacting with approved drugs like abatacept and zoledronic acid, as well as developmental drugs such as adjuvant and relapladib. These findings highlight the key role of these hub genes as biomarkers and therapeutic targets, providing a foundation for advancing precision medicine in H. pylori-associated gastric cancer. Overall, this study paves the way for advancing precision medicine in H. pylori-associated gastric cancer by providing insights into the development of early detection biomarkers, risk stratification, and targeted therapies. This supports the clinical translation of precision medicine strategies in H. pylori-associated gastric cancer.

MicroRNA 320a-3p up-regulation reduces PD-L1 expression in gastric cancer cells: an experimental and bioinformatic study

Growing evidence suggests that dysregulated microRNAs were critical in the development of tumors and the progression number of malignancies. This research aimed to check the effect of microRNA 320a-3p transfection on gastric cancer (GC) cell lines. Following transfection, the efficacy was determined by the RT-PCR method. After that, MTT, scratch assay, DAPI staining, RT-PCR, and flow cytometry were used respectively. The results demonstrated that the viability of GC cells considerably decreased following transfection. Moreover, microRNA 320a-3p transfection significantly suppressed cell migration and induced apoptosis in these cells. We found that transfection of microRNA 320a-3p remarkably decreased PD-L1 gene expression and influenced epithelial-mesenchymal transition (EMT)-related and apoptotic gene expressions. The findings propose that microRNA 320a-3p could decrease cell proliferation and migration and induce apoptosis by increasing TP53 and CASP3 expression levels in GC cells. Notably, microRNA 320a-3p might be a potential target in GC immunotherapy by suppressing the PD-L1 gene expression.

IGFL2 expression and surgical volume: Independent predictors of survival in gastric cancer

This study aimed to assess the impact of surgeons' annual volume and insulin-like growth factor-like family member 2 (IGFL2) expression on gastric cancer prognosis. Clinicopathological data from 475 patients who underwent D2 lymph node dissection were analyzed. IGFL2 expression was evaluated using immunohistochemistry. Patients were divided into training (70%) and validation (30%) groups. Univariate and multivariate Cox regression identified risk factors for overall survival (OS) and disease-free survival (DFS), leading to a clinical prediction model. Model performance was evaluated using C-index. High IGFL2 expression and low surgical volume independently predicted poorer OS and DFS (hazard ratio = 2.13, 2.17, all P < .01). Surgeons performing >26 cases annually had higher OS and DFS (hazard ratio = 1.65, 1.58, all P < .01). Nomograms integrating surgical volume, IGFL2 expression, grade, TNM staging, and carcinoembryonic antigen showed superior predictive accuracy for OS and DFS compared to TNM alone, with robust C-indices and area under the curve values. Surgeons' annual volume and IGFL2 expression independently predict gastric cancer prognosis, emphasizing the need for specialized training and further research on IGFL2's molecular mechanisms to enhance patient outcomes.

Gastric cancer-Epidemiology, modifiable and non-modifiable risk factors, challenges and opportunities: An updated review

Gastric cancer represents a significant global health challenge due to its high mortality and incidence rates, particularly in Eastern Asia, Eastern Europe, and South America. This comprehensive review synthesizes the latest epidemiological data and explores both modifiable and non-modifiable risk factors associated with gastric cancer, aiming to delineate the multifactorial etiology of this disease. Modifiable risk factors include Helicobacter pylori infection, obesity, dietary habits, smoking and alcohol consumption, whereas nonmodifiable factors comprise genetic predispositions, age, family history and male gender. The interplay of these factors significantly impacts the risk and progression of gastric cancer, suggesting potential preventive strategies. The challenges in treating gastric cancer are considerable, largely because of the late-stage diagnosis and the heterogeneity of the disease, which complicate effective treatment regimens. Current treatment strategies involve a combination of surgery, chemotherapy, radiotherapy, and targeted therapies. The FLOT regimen (5-FU, Leucovorin, Oxaliplatin and Docetaxel) is now a standard for resectable cases in Europe and the US, showing superior survival and response rates over ECF and ECX regimens. For HER2-positive gastric cancer, trastuzumab combined with chemotherapy improves overall survival, as demonstrated by the ToGA trial. Additionally, immune checkpoint inhibitors like pembrolizumab and nivolumab offer promising results. However, the five-year survival rate remains low, underscoring the urgency for improved therapeutic approaches. Recent advancements in molecular biology and cancer genomics have begun to pave the way for personalized medicine in gastric cancer care, focusing on molecular targeted therapies and immunotherapy. This review also highlights the critical need for better screening methods that could facilitate early detection and treatment, potentially improving the prognosis. By integrating epidemiological insights with new therapeutic strategies, this article aims to thoroughly understand of gastric cancer's dynamics and outline a framework for future research and clinical management, advocating for a multidisciplinary approach to tackle this formidable disease.

Curcumin for gastric cancer: Mechanism prediction via network pharmacology, docking, and in vitro experiments

BACKGROUND

Curcumin originates from the natural herb turmeric, and its antitumor effects have been known about for a long time. However, the mechanism by which curcumin affects gastric cancer (GC) has not been elucidated.

AIM

To elucidate the potential mechanisms of curcumin in the treatment of GC.

METHODS

Network pharmacological approaches were used to perform network analysis of Curcumin. We first analyzed Lipinski's Rule of Five for the use of Curcumin. Curcumin latent targets were predicted using the PharmMapper, SwissTargetPrediction and DrugBank network databases. GC disease targets were mined through the GeneCard, OMIM, DrugBank and TTD network databases. Then, GO enrichment, KEGG enrichment, protein-protein interaction (PPI), and overall survival analyses were performed. The results were further verified through molecular docking, differential expression analysis and cell experiments.

RESULTS

We identified a total of 48 curcumin-related genes with 31 overlapping GC-related targets. The intersection targets between curcumin and GC have been enriched in 81 GO biological processes and 22 significant pathways. Following PPI analysis, 6 hub targets were identified, namely, estrogen receptor 1 (ESR1), epidermal growth factor receptor (EGFR), cytochrome P450 family 3 subfamily A member 4 (CYP3A4), mitogen-activated protein kinase 14 (MAPK14), cytochrome P450 family 1 subfamily A member 2 (CYP1A2), and cytochrome p450 family 2 subfamily B member 6 (CYP2B6). These factors are correlated with decreased survival rates among patients diagnosed with GC. Molecular docking analysis further substantiated the strong binding interactions between Curcumin and the hub target genes. The experimental findings demonstrated that curcumin not only effectively inhibits the growth of BGC-823 cells but also suppresses their proliferation. mRNA levels of hub targets CYP3A4, MAPK14, CYP1A2, and CYP2B6 in BGC-823 cells were significantly increased in each dose group.

CONCLUSION

Curcumin can play an anti-GC role through a variety of targets, pathways and biological processes.

Advances in targeted therapy for human epidermal growth factor receptor 2 positive in advanced gastric cancer

Emerging therapeutic methods represented by targeted therapy are effective supplements to traditional first-line chemoradiotherapy resistance. Human epidermal growth factor receptor 2 (HER2) is one of the most important targets in targeted therapy for gastric cancer. Trastuzumab combined with chemotherapy has been used as the first-line treatment for advanced gastric cancer. The safety and efficacy of pertuzumab and margetuximab in the treatment of gastric cancer have been verified. However, monoclonal antibodies, due to their large molecular weight, inability to penetrate the blood-brain barrier, and drug resistance, lead to decreased therapeutic efficacy, so it is necessary to explore the efficacy of other HER2-targeting therapies in gastric cancer. Small-molecule tyrosine kinase inhibitors, such as lapatinib and pyrrotinib, have the advantages of small molecular weight, penetrating the blood-brain barrier and high oral bioavailability, and are expected to become the drugs of choice for perioperative treatment and neoadjuvant therapy of gastric cancer after validation by large-scale clinical trials in the future. Antibo-drug conjugate, such as T-DM1 and T-DXd, can overcome the resistance of monoclonal antibodies despite their different mechanisms of tumor killing, and are a supplement for the treatment of patients who have failed the treatment of monoclonal antibodies such as trastuzumab. Therefore, after more detailed stratification of gastric cancer patients, various gastric cancer drugs targeting HER2 are expected to play a more significant role.

LTBP2 regulates cisplatin resistance in GC cells via activation of the NF-κB2/BCL3 pathway

Gastric cancer (GC) often develops resistance to cisplatin treatment, but while latent transforming growth factor β-binding protein (LTBP2) is recognized as a potential regulator in GC, its specific role in cisplatin resistance is not fully understood. This study investigated LTBP2's impact on cisplatin resistance in GC. LTBP2 expression was assessed in various GC cell lines, and its correlation with cisplatin sensitivity was determined through cell viability assays. Lentivirus-mediated LTBP2 silencing in HGC-27 cells demonstrated enhanced cisplatin sensitivity, reduced cell proliferation, and inhibition of the NF-κB2/Bcl-3/cyclin D1 pathway. Additionally, transient transfection overexpressed the NFκB2 gene in LTBP2-silenced HGC-27/DDPR cells, restoring cisplatin sensitivity and upregulating p52/Bcl-3/cyclin D1. In conclusion, silencing LTBP2 could effectively inhibit cell proliferation and mitigate cisplatin resistance via the NFKB noncanonical pathway NFKB2 p52/Bcl-3/cyclin D1. These findings propose LTBP2 as a potential therapeutic target for overcoming cisplatin resistance in GC patients.

Clinical significance of CD166 and HER-2 in different types of gastric cancer

INTRODUCTION

Cluster of differentiation 166 (CD166), a cancer stem cell (CSC) marker, and human epidermal growth factor receptor 2 (HER-2) are expressed in a diversity of malignancies and is associated with tumor progression. Although studies regarding the importance of CSC markers and HER-2 in gastric cancer (GC) have rapidly developed, their clinicopathological, prognosis, and diagnosis value still remain unsatisfying in GC. Therefore, the present study aims to investigate the clinical, prognostic, and diagnostic significance of CD166 and HER-2 in different histological types of GC.

MATERIALS AND METHODS

Bioinformatic analysis was applied to determine the clinical importance of CD166 and HER-2 expression based on their tissue localization in primary GC tumors and the normal adjacent samples. The expression patterns, clinical significance, prognosis, and diagnosis value of CD166 and HER-2 proteins in tissue microarrays (TMAs) of 206 GC samples, including Signet Ring Cell (SRC) and intestinal types and also 28 adjacent normal tissues were evaluated using immunohistochemistry (IHC).

RESULTS

The results indicated that the expression of CD166 (membranous and cytoplasmic) and HER-2 were significantly up-regulated in tumor cells compared to adjacent normal tissues (P = 0.010, P < 0.001, and P = 0.011, respectively). A statistically significant association was detected between a high level of membranous expression of CD166 and lymphovascular invasion (P = 0.006); We also observed a statistically significant association between high cytoplasmic expression of CD166 protein and more invasion of the subserosa (P = 0.040) in the SRC type. In contrast, there was no correlation between the expression of HER-2 and clinicopathologic characteristics. Both CD166 and HER-2 showed reasonable accuracy and high specificity as diagnostic markers.

CONCLUSION

Our results confirmed that increased membranous and cytoplasmic expression of CD166 showed clinical significance in the SRC type and is associated with the progression of the disease and more aggressive tumor behaviors. These findings can be used to assist in designating subgroups of patients that require different follow-up strategies, and also, they might be utilized as the prognostic or diagnostic biomarkers in these types of GC for prospective clinical application.

Comprehensive Analysis of Disulfidptosis-Related LncRNAs in Molecular Classification, Immune Microenvironment Characterization and Prognosis of Gastric Cancer

BACKGROUND

Disulfidptosis is a novel form of programmed cell death that unveils promising avenues for the exploration of tumor treatment modalities. Gastric cancer (GC) is a malignant tumor characterized by high incidence and mortality rate. However, there has been no systematic study of disulfidptosis-related long noncoding RNAs (DRLs) signature in GC patients.

METHODS

The lncRNA expression profiles containing 412 GC samples were acquired from the Cancer Genome Atlas (TCGA) database. Differential expression analysis was performed alongside Pearson correlation analysis to identify DRLs. Prognostically significant DRLs were further screened using univariate COX regression analysis. Subsequently, LASSO regression and multifactorial COX regression analyses were employed to establish a risk signature composed of DRLs that exhibit independent prognostic significance. The predictive value of this risk signature was further validated in a test cohort. The ESTIMATE, CIBERSORT and ssGSEA methodologies were utilized to investigate the tumor immune microenvironment of GC populations with different DRLs profiles. Finally, the correlation between DRLs and various GC drug responses was explored.

RESULTS

We established a prognostic signature comprising 12 disulfidptosis-related lncRNAs (AC110491.1, AL355574.1, RHPN1-AS1, AOAH-IT1, AP001065.3, MEF2C-AS1, AC016394.2, LINC00705, LINC01952, PART1, TNFRSF10A-AS1, LINC01537). The Kaplan-Meier survival analysis revealed that patients in the high-risk group exhibited a poor prognosis. Both univariate and multivariate COX regression models demonstrated that the DRLs signature was an independent prognostic indicator in GC patients. Furthermore, the signature exhibited accurate predictions of survival at 1-, 3- and 5- years with the area under the curve (AUC) values of 0.708, 0.689 and 0.854, respectively. In addition, we also observed significant associations between the DRLs signature and various clinical variables, distinct immune landscape and drug sensitivity profiles in GC patients. The low-risk group patients may be more likely to benefit from immunotherapy and chemotherapy.

CONCLUSIONS

Our study investigated the role and potential clinical implications of DRLs in GC. The risk model constructed by DRLs demonstrated high accuracy in predicting the survival outcomes of GC and improving the treatment efficacy for GC patients.

Randomized controlled trial in gastric or gastroesophageal junction adenocarcinoma undergoing systemic therapy over two decades

INTRODUCTION

The number of randomized controlled trials (RCTs) investigating the systemic treatment of gastric or gastroesophageal junction adenocarcinoma (GA-RCTs) is increasing. We aimed to describe the characteristics and evaluate the clinical benefit of GA-RCTs over the past 20 years.

MATERIALS AND METHODS

We searched for RCTs of systemic treatment in GA published in eight major journals between 2001 and 2020 in PubMed. From the included studies, the characteristics and results of GA-RCTs were extracted. Clinical benefit was assessed using the European Society for Medical Oncology Magnitude of Clinical Benefit Scale (ESMO-MCBS).

RESULTS

About 93 RCTs with 38365 patients were included. Seventy-one (76.3%) studies received external funding, with an increase from 27.3% (2001-2005) to 94.1% (2016-2020). RCTs on targeted therapy and/or immunotherapy have also increased over time, but only 14 (41.2%) were restricted to specific biomarkers. Forty-four (47.3%) studies met their primary endpoint (defined as positive RCTs), but median overall survival has not improved over time. Moreover, only 16 (36.4%) studies met the ESMO-MCBS threshold. RCTs whose study design and results met the ESMO-MCBS thresholds has not increased over time (p = 0.827 and p = 0.733, respectively).

CONCLUSIONS

GA-RCTs are increasingly focused on targeted therapy and/or immunotherapy, and are more likely to receive external funding. However, the effect size has not shown significant improvement in the past 20 years. Only a few RCTs with positive results met ESMO thresholds. Future RCTs should prioritize the clinical benefits and provide direct evidence to optimize and reform GA treatment practices.

Laparoscopic Versus Robotic Gastric Cancer Surgery: Short-Term Outcomes-Systematic Review and Meta-Analysis of 25,521 Patients

Background: Gastric cancer has the third highest cancer-related mortality worldwide. There is no consensus regarding the optimal surgical technique to perform curative resection surgery. Objective: Compare laparoscopic gastrectomy (LG) and robotic gastrectomy (RG) regarding short-term outcomes in patients with gastric cancer. Materials and Methods: This systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. We searched the following topics: "Gastrectomy," "Laparoscopic," and "Robotic Surgical Procedures." The included studies compared short-term outcomes between LG and RG. Individual risk of bias was assessed with the Methodological Index for Non-Randomized Studies (MINORS) scale. Results: There was no significant difference between RG and LG regarding conversion rate, reoperation rate, mortality, overall complications, anastomotic leakage, distal and proximal resection margin distances, and recurrence rate. However, mean blood loss (mean difference [MD] -19.43 mL, P < .00001), length of hospital stay (MD -0.50 days, P = .0007), time to first flatus (MD -0.52 days, P < .00001), time to oral intake (MD -0.17 days, P = .0001), surgical complications with a Clavien-Dindo grade ≥III (risk ratio [RR] 0.68, P < .0001), and pancreatic complications (RR 0.51, P = .007) were significantly lower in the RG group. Furthermore, the number of retrieved lymph nodes was significantly higher in the RG group. Nevertheless, the RG group showed a significantly higher operation time (MD 41.19 minutes, P < .00001) and cost (MD 3684.27 U.S. Dollars, P < .00001). Conclusion: This meta-analysis supports the choice of robotic surgery over laparoscopy concerning relevant surgical complications. However, longer operation time and higher cost remain crucial limitations. Randomized clinical trials are required to clarify the advantages and disadvantages of RG.

The SOCS-1 -1478CA/del functional polymorphism (rs33989964) is associated with gastric cancer but is unrelated to overall survival

BACKGROUND

In vitro studies have shown that the functional - 1478CA > del polymorphism (rs33989964) of the suppressor of cytokine signaling (SOCS)-1 gene is associated with an altered trascriptional activity. Here, we sought to examine the potential association of this polymorphism with the risk of gastric cancer (GC) and to analyze its prognostic impact on overall survival (OS).

MATERIALS AND METHODS

The study cohort consisted of 74 Turkish patients with GC and 52 healthy controls. Genotyping of the SOCS-1 -1478CA > del polymorphism was carried out using restriction fragment length polymorphism analysis.

RESULTS

After allowance of age and sex, multivariable logistic regression analysis revealed that the carriage of the del allele of the SOCS-1 -1478CA > del polymorphism was independently associated with an increased risk of GC (odds ratio = 6.78, 95% confidence interval = 3.24-10.99, P < 0.001). Kaplan-Meier analysis revealed no significant differences in OS for patients harboring at least one del allele of rs33989964 compared with CA/CA homozygotes (log-rank test, P = 0.17).

CONCLUSION

While the SOCS-1 -1478CA > del polymorphism is significantly associated with the risk of GC in the Turkish population, it does not affect OS.

Machine learning-based identification of a novel prognosis-related long noncoding RNA signature for gastric cancer

Gastric cancer (GC) is one of the most common malignancies with a poor prognosis. Immunotherapy has attracted much attention as a treatment for a wide range of cancers, including GC. However, not all patients respond to immunotherapy. New models are urgently needed to accurately predict the prognosis and the efficacy of immunotherapy in patients with GC. Long noncoding RNAs (lncRNAs) play crucial roles in the occurrence and progression of cancers. Recent studies have identified a variety of prognosis-related lncRNA signatures in multiple cancers. However, these studies have some limitations. In the present study, we developed an integrative analysis to screen risk prediction models using various feature selection methods, such as univariate and multivariate Cox regression, least absolute shrinkage and selection operator (LASSO), stepwise selection techniques, subset selection, and a combination of the aforementioned methods. We constructed a 9-lncRNA signature for predicting the prognosis of GC patients in The Cancer Genome Atlas (TCGA) cohort using a machine learning algorithm. After obtaining a risk model from the training cohort, we further validated the model for predicting the prognosis in the test cohort, the entire dataset and two external GEO datasets. Then we explored the roles of the risk model in predicting immune cell infiltration, immunotherapeutic responses and genomic mutations. The results revealed that this risk model held promise for predicting the prognostic outcomes and immunotherapeutic responses of GC patients. Our findings provide ideas for integrating multiple screening methods for risk modeling through machine learning algorithms.

Genetic mutation and tumor microbiota determine heterogenicity of tumor immune signature: Evidence from gastric and colorectal synchronous cancers

Both colorectal and gastric cancer are lethal solid-tumor malignancies, leading to the majority of cancer-associated deaths worldwide. Although colorectal cancer (CRC) and gastric cancer (GC) share many similarities, the prognosis and drug response of CRC and GC are different. However, determinants for such differences have not been elucidated. To avoid genetic background variance, we performed multi-omics analysis, including single-cell RNA sequencing, whole-exome sequencing, and microbiome sequencing, to dissect the tumor immune signature of synchronous primary tumors of GC and CRC. We found that cellular components of juxta-tumoral sites were quite similar, while tumoral cellular components were specific to the tumoral sites. In addition, the mutational landscape and microbiome contributed to the distinct TME cellular components. Overall, we found that different prognoses and drug responses of GC and CRC were mainly due to the distinct TME determined by mutational landscape and microbiome components.

Crosstalk between tumor-associated macrophages and tumor cells promotes chemoresistance via CXCL5/PI3K/AKT/mTOR pathway in gastric cancer

BACKGROUND

5-fluorouracil (5-FU)-based chemotherapy regimen has been widely used for the treatment of gastric cancer, but meanwhile the development of chemotherapeutic resistance remains a major clinical challenge. Tumor microenvironment (TME) frequently correlates with the development of chemoresistance in human cancer. As a major component of TME, the role of tumor-associated macrophages (TAMs) in the chemoresistance of gastric cancer has not been fully elucidated.

METHODS

Immunohistochemistry (IHC) was applied to detect the density of TAMs in clinical samples of 103 patients with gastric cancer who had undergone 5-FU-based neoadjuvant chemotherapy. 5-FU-resistant gastric cell lines MKN45-R and HGC27-R were established, macrophages were then separately co-cultured with MKN45-R, HGC27-R cells and their parental cells. The effect of gastric cancer cells on the polarization of macrophages, the biological function of M2-polaried macrophages and the mechanism for promoting 5-FU-resistance were investigated. Then the correlation between the expression of CXC motif chemokine ligand 5 (CXCL5) and the infiltration of hemoglobin scavenger receptor (CD163) positive and mannose receptor (CD206) positive macrophages was analyzed, the prognostic value of CXCL5 expression in clinical samples was further explored.

RESULTS

The high infiltration of macrophages marked by CD68 in gastric cancer samples was significantly associated with the resistance of gastric cancer to chemotherapy. Gastric cancer cells could modulate macrophages to M2-like polarization through indirect co-culture, and chemoresistant cells were more efficient in inducing macrophages polarization to M2 phenotype. Co-culturing M2-polarized macrophages in turn enhanced 5-FU-resistance of gastric cancer cells, and it was further verified that CXCL5 derived from M2-polarized macrophages promoted chemoresistance through activing the PI3K/AKT/mTOR pathway. Besides, high level of CXCL5 could recruit monocytes to form more M2-polarized macrophages. Clinically, high expression of CXCL5 in gastric cancer samples was associated with the high infiltration of CD163 positive macrophages and CD206 positive macrophages, and patients with high expression of CXCL5 presented lower overall survival (OS) rates than those with low expression of CXCL5.

CONCLUSION

Interaction between TAMs and gastric cancer cells promoted chemoresistance in gastric cancer via CXCL5/PI3K/AKT/mTOR pathway. Thus, targeting TAMs and blocking the cell-cell crosstalk between TAMs and gastric cancer cells may represent prospective therapeutic strategies for patients with gastric cancer.

Ethnic Disparities in Early-Onset Gastric Cancer: A Population-Based Study in Texas and California

BACKGROUND

Incidence rates of gastric cancer are increasing in young adults (age &lt;50 years), particularly among Hispanic persons. We estimated incidence rates of early-onset gastric cancer (EOGC) among Hispanic and non-Hispanic White persons by census tract poverty level and county-level metro/nonmetro residence.

METHODS

We used population-based data from the California and Texas Cancer Registries from 1995 to 2016 to estimate age-adjusted incidence rates of EOGC among Hispanic and non-Hispanic White persons by year, sex, tumor stage, census tract poverty level, metro versus nonmetro county, and state. We used logistic regression models to identify factors associated with distant stage diagnosis.

RESULTS

Of 3,047 persons diagnosed with EOGC, 73.2% were Hispanic White. Incidence rates were 1.29 [95% confidence interval (CI), 1.24-1.35] and 0.31 (95% CI, 0.29-0.33) per 100,000 Hispanic White and non-Hispanic White persons, respectively, with consistently higher incidence rates among Hispanic persons at all levels of poverty. There were no statistically significant associations between ethnicity and distant stage diagnosis in adjusted analysis.

CONCLUSIONS

There are ethnic disparities in EOGC incidence rates that persist across poverty levels.

IMPACT

EOGC incidence rates vary by ethnicity and poverty; these factors should be considered when assessing disease risk and targeting prevention efforts.

High CHAF1A Expression Levels Are Positively-Correlated with PD-L1 Expression and Indicate Poor Prognosis in Gastric Cancer

Objective

The aim of this study was to analyze the association between the expression of chromatin assembly factor 1 subunit A (CHAF1A) in gastric cancer (GC) and clinicopathological features, disease prognosis, and expression of programmed cell death-ligand 1 (PD-L1). Material and Methods. A total of 140 GC tissue specimens were collected between January 2013 and December 2017. CHAF1A expression in GC and paracancerous tissues was determined. Then, the associations between CHAF1A expression level in the collected tissues and clinicopathological features as well as PD-L1 expression level were investigated. Cox regression analyses were carried out to determine whether CHAF1A is an independent prognostic factor for GC. Finally, the association between CHAF1A expression levels and survival of the GC patients was investigated.

Results

A significantly higher level of CHAF1A expression in GC tissues was found compared to that in paracancerous tissues (p=0.042). CHAF1A expression level in GC tissues was found to be strongly associated with family history (p=0.005), smoking history (p=0.016), T stage (p=0.001), tumor marker AFP (p=0.017), tumor marker CEA (p=0.027), and PD-L1 expression (p=0.029). CHAF1A expression was also found to be positively correlated to PD-L1 expression (p=0.012). Moreover, high CHAF1A expression levels were found to lead to poor prognosis (p=0.019). Univariate and multivariate analyses all showed that CHAF1A was an independent poorer prognostic factor for gastric cancer (p=0.021, HR = 1.175, 95% CI: 1.090–2.890 for univariate analyses; p=0.014, HR = 2.191, 95% CI:1.170–4.105 for multivariate analyses). A high level of CHAF1A expression was thus found to be an independent risk factor for GC prognosis.

Conclusion

High CHAF1A expression is associated with poor GC prognosis and positively correlated to PD-L1 expression. Thus, CHAF1A expression level may be used as a novel biomarker for GC diagnosis.

Prognostic role of myeloid-derived tumor-associated macrophages at the tumor invasive margin in gastric cancer with liver metastasis (GCLM): a single-center retrospective study

BACKGROUND

Liver metastasis is one of the important factors leading to poor prognosis of gastric cancer. According to the classic "seed soil theory", it is speculated that the liver microenvironment at the invasion margin of gastric cancer liver metastases (GCLM) may have a crucial impact on tumor progression. However, few studies had stated the correlation between the patients' prognosis and the densities of stromal cells infiltrating into the invasive margin, where our retrospective study designed to identify the role of infiltrating macrophages on the prognosis of GCLM as a reliable supplement of predictive tumor markers.

METHODS

The material consisted of a group of 72 gastric cancer (GC) patients with liver metastasis diagnosed from February 2015 and December 2020. The CD68+, CD206+, and Clec4f+ macrophages in their specimens were counted by immunohistochemistry (IHC), and the analysis area was the invasive margin of metastatic lesions. Clinical data were collected retrospectively. Overall survival (OS) was calculated from the date of initial diagnosis to the date of last follow-up or death. Survival analyses were performed using the Kaplan-Meier method and log-rank test. Multivariate Cox regression was performed to asses impact of macrophages on OS.

RESULTS

The expression of CD206 could indicate the prognosis of patients with GCLM, and patients with high expression of CD206 had worse prognoses (P=0.0002). Univariate and multivariate analyses showed that CD206 was an independent risk factor for prognosis (HR 5.276, 95% CI: 1.730-16.089, P=0.003).

CONCLUSIONS

The CD206+ myeloid-derived tumor associated macrophages (TAMs) may predict whether patients could benefit from R1 resection of liver-metastatic lesions, which has important theoretical significance and practical value for accurately evaluating the clinical prognosis of patients with GCLM and guiding clinical treatment.

Lenvatinib inhibits the growth of gastric cancer patient-derived xenografts generated from a heterogeneous population

BACKGROUND

Lenvatinib is a multitargeted tyrosine kinase inhibitor that is being tested in combination with immune checkpoint inhibitors to treat advanced gastric cancer; however, little data exists regarding the efficacy of lenvatinib monotherapy. Patient-derived xenografts (PDX) are established by engrafting human tumors into immunodeficient mice. The generation of PDXs may be hampered by growth of lymphomas. In this study, we compared the use of mice with different degrees of immunodeficiency to establish PDXs from a diverse cohort of Western gastric cancer patients. We then tested the efficacy of lenvatinib in this system.

METHODS

PDXs were established by implanting gastric cancer tissue into NOD.Cg-PrkdcscidIl2rgtm1Wjl/SzJ (NSG) or Foxn1nu (nude) mice. Tumors from multiple passages from each PDX line were compared histologically and transcriptomically. PDX-bearing mice were randomized to receive the drug delivery vehicle or lenvatinib. After 21 days, the percent tumor volume change (%Δvtumor) was calculated.

RESULTS

23 PDX models were established from Black, non-Hispanic White, Hispanic, and Asian gastric cancer patients. The engraftment rate was 17% (23/139). Tumors implanted into NSG (16%; 18/115) and nude (21%; 5/24) mice had a similar engraftment rate. The rate of lymphoma formation in nude mice (0%; 0/24) was lower than in NSG mice (20%; 23/115; p < 0.05). PDXs derived using both strains maintained histologic and gene expression profiles across passages. Lenvatinib treatment (mean %Δvtumor: -33%) significantly reduced tumor growth as compared to vehicle treatment (mean %Δvtumor: 190%; p < 0.0001).

CONCLUSIONS

Nude mice are a superior platform than NSG mice for generating PDXs from gastric cancer patients. Lenvatinib showed promising antitumor activity in PDXs established from a diverse Western patient population and warrants further investigation in gastric cancer.

Pharmaceutical advances in the treatment of gastric adenocarcinoma

INTRODUCTION

Gastric adenocarcinoma (GAC) continues to be a prevalent global concern. Differences in incidence are predominantly due to geographic locations with Asia contributing to majority of cases. Another parallel challenge is due to heterogenous molecular and immune profiles of GAC along with varying clinicopathological features of patients. In most countries, GACs are diagnosed late in an advanced stage as the early detection infrastructure cannot be implemented or not feasible. Future advances in liquid biopsies could change all that.

AREAS COVERED

The authors focus on the recent advances in the management of advanced GAC patients w but also address localized GAC. Herein, the authors review the most contemporary treatments and promising breakthroughs.

EXPERT OPINION

The addition of immunotherapy to standard of care has changed the outlook of advanced GAC patients. The authors anticipate continued advances in the development of immunotherapy both in surgically resectable and unresectable GACs. Targeting the ERBB2 (HER2) protein pathway remains uniquely important in GACs with ERBB2 (HER2) protein positivity. Currently, many novel anti-ERBB2 (HER2) protein therapies are under investigation. The next generation of GAC patients will derive considerably more benefit as the therapeutic landscape becomes more complex coupled with challenges in biomarker platforms and new drug development.

miR-153-3p Attenuates the Development of Gastric Cancer by Suppressing SphK2

Gastric cancer (GC) is the second leading cause of cancer-related mortality worldwide. MicroRNAs (miRNAs) have been extensively reported to play a role in GC development; however, it remains unknown whether miR-153-3p participates in the nosogenesis of GC. GC tissues along with the adjacent nontumor tissues were obtained from 50 patients with GC. Moreover, we incubated human GC cell lines (SGC7901, AGS, MGC803, and BGC823) and a gastric epithelial cell line (GES-1) and then transfected BGC823 cells with miR-153-3p and DNA/SphK2 vector to determine the action of miR-153-3p and SphK2 on GC. RT-qPCR was performed to determine the levels of miR-153-3p and sphingosine kinase 2 (SphK2). The viability of BGC823 cells was measured by the CCK-8 assay, while wound healing assays and transwell assays were used to measure the migration and invasion ability of BGC823 cells. Western blotting analysis and immunohistochemistry (IHC) were conducted to evaluate the level of SphK2. The binding ability of miR-153-3p and SphK2 was determined by dual-luciferase reporter assays. The expression level of miR-153-3p was reduced in GC tissues and cells, while the SphK2 was enhanced. An increase in miR-153-3p level led to a decline in the growth and metastasis of GC cells and increased their apoptosis. Moreover, a decrease in miR-153-3p level elevated GC cells growth and metastasis, and attenuated their apoptosis. SphK2 was also corroborated as a downstream gene of miR-153-3p. Here, SphK2 expression was elevated in GC tissues and cells, indicating SphK2 might be involved in the development of GC. Rescue assays showed that miR-153-3p could reverse the effect of SphK2 on the cell growth, metastasis, and the apoptosis of GC cells. In conclusion, this study showed that miR-153-3p suppressed the growth and metastasis in GC cells by regulating SphK2, which might facilitate the search for novel biomarkers to treat GC.

Immune Score Predicts Outcomes of Gastric Cancer Patients Treated with Adjuvant Chemoradiotherapy

Background

Substantial evidence has demonstrated that tumor-infiltrating lymphocytes (TILs) are correlated with patient prognosis. The TIL-based immune score (IS) affects prognosis in various cancers, but its prognostic impact in gastric cancer (GC) patients treated with adjuvant chemoradiotherapy remains unclear.

Methods

A total of 101 GC patients who received chemoradiotherapy after gastrectomy were retrospectively analyzed in this study. Immunohistochemistry staining for CD3+ and CD8+ T-cell counts in both tumor center (CT) and invasive margin (IM) regions was built into the IS. Patients were then divided into three groups based on their differential IS levels. The correlation between IS and clinical parameters was analyzed. The prognostic impact of IS and clinical parameters was evaluated using Kaplan-Meier analysis and Cox proportional hazard regression analysis. Receiver operating characteristic (ROC) curves were plotted to compare the area under the curve (AUC) of IS with other clinical parameters. Nomograms for disease-free survival (DFS) and overall survival (OS) prediction were constructed based on the identified parameters.

Results

Finally, 20 (19.8%), 57 (56.4%), and 24 (23.8%) GC patients were identified with low, intermediate, and high IS levels, respectively. GC patients with higher IS levels exhibited better DFS (p < 0.001) and OS (p < 0.001). IS was an independent prognostic factor for both DFS (p < 0.001) and OS (p < 0.001) in multivariate analysis. IS presented a better predictive ability than the traditional pathological tumor-node-metastasis (pTNM) staging system (AUC: 0.801 vs. 0.677 and 0.800 vs. 0.660, respectively) with respect to both DFS and OS. The C-index of the nomograms for DFS and OS prediction was 0.737 and 0.774, respectively.

Conclusions

IS is a strong predictive factor for both DFS and OS in GC patients treated with adjuvant chemoradiotherapy, which may complement the traditional pTNM staging system.

Characteristics and Research Waste Among Randomized Clinical Trials in Gastric Cancer

IMPORTANCE

The results of numerous large randomized clinical trials (RCTs) have changed clinical practice in gastric cancer (GC). However, research waste (ie, unpublished data, inadequate reporting, or avoidable design limitations) is still a major challenge for evidence-based medicine.

OBJECTIVES

To determine the characteristics of GC RCTs in the past 20 years and the presence of research waste and to explore potential targets for improvement.

DESIGN, SETTING, AND PARTICIPANTS

In this cross-sectional study of GC RCTs, ClinicalTrials.gov was searched for phase 3 or 4 RCTs registered from January 2000 to December 2019 using the keyword gastric cancer. Independent investigators undertook assessments and resolved discrepancies via consensus. Data were analyzed from August through December 2020.

MAIN OUTCOMES AND MEASURES

The primary outcomes were descriptions of the characteristics of GC RCTs and the proportion of studies with signs of research waste. Research waste was defined as unpublished data, inadequate reporting, or avoidable design limitations. Publication status was determined by searching PubMed and Scopus databases. The adequacy of reporting was evaluated using the Consolidated Standards of Reporting Trials (CONSORT) reporting guideline checklist. Avoidable design limitations were determined based on existing bias or lack of cited systematic literature reviews. In the analyses of research waste, 125 RCTs that ended after June 2016 without publication were excluded.

RESULTS

A total of 262 GC RCTs were included. The number of RCTs increased from 25 trials in 2000 to 2004 to 97 trials in 2015 to 2019, with a greater increase among RCTs of targeted therapy or immunotherapy, which increased from 0 trials in 2000 to 2004 to 36 trials in 2015 to 2019. The proportion of RCTs that were multicenter was higher in non-Asian regions than in Asian regions (50 of 71 RCTs [70.4%] vs 96 of 191 RCTs [50.3%]; P = .004). The analysis of research waste included 137 RCTs, of which 81 (59.1%) were published. Among published RCTs, 65 (80.2%) were judged to be adequately reported and 63 (77.8%) had avoidable design defects. Additionally, 119 RCTs (86.9%) had 1 or more features of research waste. Study settings that included blinding (odds ratio [OR], 0.56; 95% CI, 0.33-0.93; P = .03), a greater number of participants (ie, ≥200 participants; OR, 0.07; 95% CI, 0.01-0.51; P = .01), and external funding support (OR, 0.22; 95% CI, 0.08-0.60; P = .004) were associated with lower odds of research waste. Additionally, 35 RCTs (49.3%) were referenced in guidelines, and 18 RCTs (22.2%) had their prospective data reused.

CONCLUSIONS AND RELEVANCE

To our knowledge, this study is the first to describe the characteristics of GC RCTs in the past 20 years, and it found a research waste burden, which may provide evidence for the development of rational RCTs and reduction of waste in the future.

Autoimmunity as an Etiological Factor of Cancer: The Transformative Potential of Chronic Type 2 Inflammation

Recent epidemiological studies have found an alarming trend of increased cancer incidence in adults younger than 50 years of age and projected a substantial rise in cancer incidence over the next 10 years in this age group. This trend was exemplified in the incidence of non-cardia gastric cancer and its disproportionate impact on non-Hispanic white females under the age of 50. The trend is concurrent with the increasing incidence of autoimmune diseases in industrialized countries, suggesting a causal link between the two. While autoimmunity has been suspected to be a risk factor for some cancers, the exact mechanisms underlying the connection between autoimmunity and cancer remain unclear and are often controversial. The link has been attributed to several mediators such as immune suppression, infection, diet, environment, or, perhaps most plausibly, chronic inflammation because of its well-recognized role in tumorigenesis. In that regard, autoimmune conditions are common causes of chronic inflammation and may trigger repetitive cycles of antigen-specific cell damage, tissue regeneration, and wound healing. Illustrating the connection between autoimmune diseases and cancer are patients who have an increased risk of cancer development associated with genetically predisposed insufficiency of cytotoxic T lymphocyte-associated protein 4 (CTLA4), a prototypical immune checkpoint against autoimmunity and one of the main targets of cancer immune therapy. The tumorigenic process triggered by CTLA4 insufficiency has been shown in a mouse model to be dependent on the type 2 cytokines interleukin-4 (IL4) and interleukin-13 (IL13). In this type 2 inflammatory milieu, crosstalk with type 2 immune cells may initiate epigenetic reprogramming of epithelial cells, leading to a metaplastic differentiation and eventually malignant transformation even in the absence of classical oncogenic mutations. Those findings complement a large body of evidence for type 1, type 3, or other inflammatory mediators in inflammatory tumorigenesis. This review addresses the potential of autoimmunity as a causal factor for tumorigenesis, the underlying inflammatory mechanisms that may vary depending on host-environment variations, and implications to cancer prevention and immunotherapy.

Long noncoding RNA (lncRNA) EIF3J-DT induces chemoresistance of gastric cancer via autophagy activation

Chemotherapy is currently the main treatment for unresectable or advanced postoperative gastric cancers. However, its efficacy is negatively affected by the occurrence of chemoresistance, which severely affects patient prognosis. Recently, dysregulation in autophagy has been suggested as a potential mechanism for chemoresistence, and long noncoding RNA (lncRNA) also shows its regulatory role in cancer drug resistance. Using RNA sequencing, we found that lncRNA EIF3J-DT was highly expressed in drug-resistant gastric cancer cells. In-vitro and in-vivo experiments showed that EIF3J-DT activated autophagy and induced drug resistance in gastric cancer cells by targeting ATG14. Bioinformatics and experimental results showed that EIF3J-DT regulated the expression of ATG14 through direct binding to enhance stabilization of ATG14 mRNA and via blocking the degradation of ATG14 mRNA through competitively binding with microRNA (miRNA) MIR188-3p. Therefore, EIF3J-DT increased the expression of ATG14, contributing to activation of autophagy and chemoresistance. Furthermore, it was confirmed that EIF3J-DT and ATG14 were highly expressed in gastric cancer patients resistant to chemotherapy, and this was closely associated with patient prognosis. In conclusion, EIF3J-DT is involved in the regulation of autophagy and chemoresistance in gastric cancer cells by targeting ATG14. It may be a suitable new target for enhancing chemosensitivity and improving prognosis.Abbreviations: 3-MA: 3-methyladenine; 5-Fu: 5-fluorouracil; ATG: autophagy related; C-CASP3: cleaved caspase 3; C-CASP7: cleaved caspase 7; C-PARP: cleaved PARP; CQ: chloroquine; CR: complete response; DIG: digoxigenin; ESR1: estrogen receptor 1; FBS: fetal bovine serum; FISH: fluorescence in situ hybridization; IHC: immunohistochemistry; ISH: in situ hybridization; lncRNA: long noncoding RNA; miRNA: microRNA; MUT: mutant; NC: negative control; OXA: oxaliplatin; PBS: phosphate-buffered saline; PD: progressive disease; PFA: paraformaldehyde; PR: partial response; qPCR: quantitative polymerase chain reaction; RAPA: rapamycin; SD: stable disease; TEM: transmission electron microscopy; WT: wild type.

Clinical and prognostic significances of cancer stem cell markers in gastric cancer patients: a systematic review and meta-analysis

Background

Gastric cancer (GC) is considered one of the most lethal malignancies worldwide, which is accompanied by a poor prognosis. Although reports regarding the importance of cancer stem cell (CSC) markers in gastric cancer progression have rapidly developed over the last few decades, their clinicopathological and prognostic values in gastric cancer still remain inconclusive. Therefore, the current meta-analysis aimed to quantitatively re-evaluate the association of CSC markers expression, overall and individually, with GC patients’ clinical and survival outcomes.

Methods

Literature databases including PubMed, Scopus, ISI Web of Science, and Embase were searched to identify the eligible articles. Hazard ratios (HRs) or odds ratios (ORs) with 95% confidence intervals (CIs) were recorded or calculated to determine the relationships between CSC markers expression positivity and overall survival (OS), disease-free survival (DFS)/relapse-free survival (RFS), disease-specific survival (DSS)/ cancer-specific survival (CSS), and clinicopathological features.

Results

We initially retrieved 4,425 articles, of which a total of 66 articles with 89 studies were considered as eligible for this meta-analysis, comprising of 11,274 GC patients. Overall data analyses indicated that the overexpression of CSC markers is associated with TNM stage (OR = 2.19, 95% CI 1.84–2.61, P = 0.013), lymph node metastasis (OR = 1.76, 95% CI 1.54–2.02, P < 0.001), worse OS (HR = 1.65, 95% CI 1.54–1.77, P < 0.001), poor CSS/DSS (HR = 1.69, 95% CI 1.33–2.15, P < 0.001), and unfavorable DFS/RFS (HR = 2.35, 95% CI 1.90–2.89, P < 0.001) in GC patients. However, CSC markers expression was found to be slightly linked to tumor differentiation (OR = 1.25, 95% CI 1.01–1.55, P = 0.035). Sub-analysis demonstrated a significant positive relationship between most of the individual markers, specially Gli-1, Oct-4, CD44, CD44V6, and CD133, and clinical outcomes as well as the reduced survival, whereas overexpression of Lgr-5, Nanog, and sonic hedgehog (Shh) was not found to be related to the majority of clinical outcomes in GC patients.

Conclusion

The expression of CSC markers is mostly associated with worse outcomes in patients with GC, both overall and individual. The detection of a combined panel of CSC markers might be appropriate as a prognostic stratification marker to predict tumor aggressiveness and poor prognosis in patients with GC, which probably results in identifying novel potential targets for therapeutic approaches.