Immunotherapy for gastric cancers: emerging role and future perspectives

Integrated multi-omics analysis and machine learning identify hub genes and potential mechanisms of resistance to immunotherapy in gastric cancer

BACKGROUND

Patients with gastric cancer respond poorly to immunotherapy. There are still unknowns about the biomarkers associated with immunotherapy sensitivity and their underlying molecular mechanisms.

METHODS

Gene expression data for gastric cancer were gathered from TCGA and GEO databases. DEGs associated with immunotherapy response came from ICBatlas. KEGG and GO analyses investigated pathways. Hub genes identification employed multiple machine algorithms. Associations between hub genes and signaling pathways, disease genes, immune cell infiltration, drug sensitivity, and prognostic predictions were explored via multi-omics analysis. Hub gene expression was validated through HPA and CCLE. Multiple algorithms pinpointed Cancer-Associated Fibroblasts genes (CAFs), with ten machine-learning methods generating CAFs scores for prognosis. Model gene expression was validated at the single-cell level using the TISCH database.

RESULTS

We identified 201 upregulated and 935 downregulated DEGs. Three hub genes, namely CDH6, EGFLAM, and RASGRF2, were unveiled. These genes are implicated in diverse disease-related signaling pathways. Additionally, they exhibited significant correlations with disease-associated gene expression, immune cell infiltration, and drug sensitivity. Exploration of the HPA and CCLE databases exposed substantial expression variations across patients and cell lines for these genes. Subsequently, we identified CAFs-associated genes and established a robust prognostic model. The analysis in the TISCH database showed that the genes in this model were highly expressed in CAFs.

CONCLUSIONS

The results unveil an association between CDH6, EGFLAM, and RASGRF2 and the immunotherapeutic response in gastric cancer. These genes hold potential as predictive biomarkers for gastric cancer immunotherapy resistance and prognostic assessment.

Current therapies and progress in the treatment of advanced gastric cancer

Gastric cancer (GC) remains one of the most life-threatening disease worldwide with poor prognosis because of the absence of effective treatment and the delay in diagnosis. Due to the delay of diagnosis, a large proportion of GC patients are diagnosed as advanced GC, with extreme short lifespan. In the past few years, some pivotal progress and novel therapies was proposed, and conducted into clinical researches and practice. In this study, we summarized the development of several novel immunotherapy or targeted treatment modalities for advanced GC, including immune checkpoint inhibitors, anti-angiogenic therapy and cancer vaccines. Additionally, the advantage and potential weakness in each of these therapeutic methods are also listed. Finally, we discussed the promising research direction of advanced GC treatment, and the limitation in basic and clinical research of advanced GC, including the combination of immunotherapy and targeted therapy.

Perioperative Tailored Treatments for Gastric Cancer: Times Are Changing

Resectable gastric or gastroesophageal (G/GEJ) cancer is a heterogeneous disease with no defined molecularly based treatment strategy. Unfortunately, nearly half of patients experience disease recurrence despite standard treatments (neoadjuvant and/or adjuvant chemotherapy/chemoradiotherapy and surgery). In this review, we summarize the evidence of potential tailored approaches in perioperative treatment of G/GEJ cancer, with a special focus on patients with human epidermal growth factor receptor-2(HER2)-positive and microsatellite instability-high (MSI-H) tumors. In patients with resectable MSI-H G/GEJ adenocarcinoma, the ongoing INFINITY trial introduces the concept of non-operative management for patients with complete clinical-pathological-molecular response, and this could be a novel and potential practice changing strategy. Other pathways involving vascular endothelial growth factor receptor (VEGFR), fibroblast growth factor receptor (FGFR), claudin18 isoform 2 (CLDN18.2), and DNA damage repair proteins are also described, with limited evidence until now. Although tailored therapy appears to be a promising strategy for resectable G/GEJ cancer, there are several methodological issues to address: inadequate sample size for pivotal trials, underestimation of subgroup effects, and choice of primary endpoint (tumor-centered vs. patient-centered endpoints). A better optimization of G/GEJ cancer treatment allows maximizing patient outcomes. In the perioperative phase, although caution is mandatory, times are changing and tailored strategies could introduce new treatment concepts. Overall, MSI-H G/GEJ cancer patients possess the characteristics to be the subgroup that could receive the most benefit from a tailored approach.

Common strategies for effective immunotherapy of gastroesophageal cancers using immune checkpoint inhibitors

Gastroesophageal cancers (GECs) are very prevalent around the world and rank as the second cause of all cancer-related deaths in men and women and demonstrate a very poor prognosis. Currently, the treatment options for these malignancies are very limited and the response rates are also very low. Recently, immune checkpoint inhibitors (ICIs) have been proposed for immunotherapy of GECs; although preliminary results obtained from the clinical trials of ICIs in GECs were promising, they have shown to be effective only in a few subsets of patients who had a previous immune response to the tumor. In order to maximize the efficacy of ICIs in GECs, as well as identify the patients who will likely benefit from ICIs, several predictive biomarkers, such as Programmed death-ligand 1 (PD-L1) have been developed and evaluated. Since the single ICI therapies resulted in poor treatment response, several clinical studies began to explore various combinations of one or two ICIs with other anti-cancer treatment approaches, including chemotherapy, radiotherapy, and anti-angiogenesis therapy. These combinations demonstrated a more effective response among the ICIs-responsive patients and even in some instances sensitized the non-responsive individuals. This review is aimed to summarize the efforts made so far for improving the effectiveness of ICIs in the treatment of patients with GECs. Furthermore, multiple aspects of translational medicine such as available biomarkers and interactions between tumor and the immune system, as well as clinical aspects regarding the combination therapies and results of clinical trials will be discussed.

Immunotherapy in Squamous Cell Cancer of the Esophagus

Treatment of esophageal carcinoma has changed dramatically following several landmark trials, which have proven the benefit of immunotherapy. The selective PD-1 (programmed cell death ligand-1)-inhibitor nivolumab has been shown to improve DFS in the adjuvant therapy setting (CheckMate-577). In the first-line treatment, PD-L1 positive (CPS ≥ 10) squamous cell carcinoma patients (pts) have been shown to have an increased OS following treatment with the PD-1-inhibitor pembrolizumab in combination with chemotherapy (KEYNOTE-590). Nivolumab also improved overall survival in the first line setting either combined with ipilimumab or with chemotherapy (CheckMate 648) compared to chemotherapy alone. In Asian first-line patients, phase III trials investigating camrelizumab (ESCORT 1), toripalimab (JUPITER 06), or sintilimab (ORIENT 15) in addition to chemotherapy also showed significant survival benefits. In the second-line setting, monotherapy with nivolumab (ATTRACTION-03), pembrolizumab (KEYNOTE-181), camrelizumab (ESCORT), and tislelizumab (RATIONALE 302) demonstrated a benefit in OS in comparison to chemotherapy. Here we will review these trials and integrate them into the current treatment algorithm.

Immunotherapy for Esophageal Cancer: State-of-the Art in 2021

The management of esophageal cancer (EC) has experienced manifold changes during the last decades. Centralization of EC treatment has been introduced in many countries, subsequently allowing the development of specialized high-volume centers. Minimal invasive surgery has replaced open surgery in many centers, whereas more potent systemic treatments have been introduced in clinical practice. Newer chemotherapy regimens increase long-term survival. Nevertheless, the overall survival of EC patients remains dismal for advanced tumor stages. In this direction, a wide range of targeted biologic agents (immunotherapy) is currently under assessment. Anti- Human Epidermal Growth Factor Receptor-2 (HER-2) monoclonal antibodies are used in HER2 (+) tumors, predominantly well-differentiated adenocarcinomas, and are currently assessed in the neoadjuvant setting (TRAP, INNOVATION trials). Immune checkpoint inhibitors Nivolumab (ATTRACTION-03) and pembrolizumab (KEYNOTE-181), have demonstrated a survival benefit compared with conventional chemotherapy in heavily pre-treated progressive disease. More recently, CheckMate-577 showed very promising results for nivolumab in a curative adjuvant setting, improving disease-free survival mainly for esophageal squamous cell carcinoma. Several ongoing trials are investigating novel targeted agents in the preoperative setting of locally advanced EC. In addition, other immunomodulatory approaches such as peptide vaccines and tumor infiltrating lymphocytes (TILs) are currently under development and should be increasingly integrated into clinical practice.

State-of-the-Art of Monoclonal Antibodies for the Treatment of Gastric Cancer

Gastric cancer (GC) is a complex and heterogeneous disease with poor prognosis and limited available treatment options. During recent years, several molecular stratifications have been proposed to optimize the overall treatment strategy for GC patients. Breakthroughs in cancer biology and in molecular profiling through DNA and RNA sequencing are now opening novel landscapes, leading to the personalization of molecular matched therapy. In particular, therapies against HER2, Claudine 18.2, Fibroblast Growth Factor Receptors (FGFR), and other molecular alterations could significantly improve survival outcomes in the advance phase of the disease. Furthermore, immunotherapy with checkpoint inhibitors also represents a promising option in a selected population. Hoping that precision oncology will enter soon in clinical practice, our review describes the state of the art of many novel pathways and the current evidence supporting the use of monoclonal antibodies implicated in GC treatment.

Non-immune Cell Components in the Gastrointestinal Tumor Microenvironment Influencing Tumor Immunotherapy

Interactions of genetic susceptibility factors, immune microenvironment, and microbial factors contribute to gastrointestinal tumorigenesis. The suppressive immune microenvironment reshaped by the tumors during gastrointestinal tumorigenesis directly contributes to T-cell depletion in tumor immunotherapy. Soluble factors secreted by tumor cells or stromal cells collectively shape the suppressive immune environment. Here, we reviewed the key factors in the gastrointestinal tumor microenvironment that influence tumor immunotherapy, focusing on the effects of fibroblasts, neuronal cells, soluble cytokines, exosomes, and the microbiome in tumor microenvironment. Research in this field has helped to identify more precise and effective biomarkers and therapeutic targets in the era of tumor immunotherapy.

Comparing immunotherapies to other frequently used treatments of gastric cancer

Introduction: Although standard doublet chemotherapy represents the upfront gold standard to increase survival and improve quality of life of gastric cancer patients, overall improvements in long-term outcomes are modest and novel treatments are urgently needed. Among these, immunotherapy is an increasingly attractive option.Areas covered: A number of clinical trials have shown that checkpoint inhibitors may be of value, but many unclear issues remain controversial and should be promptly untangled. In our short review, we offer the current available data regarding immunotherapies in gastric cancers, discuss potential limits of the reported trials, compare outcomes of checkpoints inhibitor to those of standard chemotherapy or other novel treatments, and present basic principles of immune surveillance and immune escape that may be embraced in the near future with novel drug combinations.Expert opinion: Gastric cancer patients may benefit from immunotherapy, both given alone in advanced lines and upfront in combination with chemotherapy. We believe that appropriate patients' and tumor's selection are crucial issues to maximize its potential efficacy. In addition, we think that assay standardization, biomarker agreement, and translational studies will improve the benefit-to-risk ratio of these agents in the clinical practice.

Patterns of immune infiltration in gastric cancer and their clinical significance

OBJECTIVE

The malignant phenotypes of cancer are defined not only by its intrinsic tumor cells but also by the tumor-infiltrating immune cells activated and recruited to the cancer microenvironment. However, a comprehensive introduction of gastric cancer immune cell infiltration has not been identified so far.

METHODS

In this study, we comprehensively analyzed the tumor-infiltrating immune cells abundance in gastric cancer for the first time by CIBERSORT. The meta-analysis, single-sample gene set enrichment analysis and hierarchical agglomerative clustering were used to measure and evaluate the respective proportions of 22 cell types of immune infiltration using normalized gene expression data. The fraction of tumor-infiltrating immune cells subpopulations was also evaluated to determine the associations with clinical features and molecular subtypes.

RESULTS

Tumor-infiltrating immune cells are extensively involved in the pathogenesis and development of the gastric cancer. We discovered Tfh and activated CD4+ memory T cells were associated with poorer overall survival and Progression-free survival (PFS), but that naïve B cells were opposite for PFS. Unsupervised clustering analysis revealed there existed three tumor-infiltrating immune cells subgroups with distinct survival patterns. Specially, cluster 1 showed significantly better clinical outcome than other two clusters.

CONCLUSIONS

Collectively, our data explored the differences of tumor-infiltrating immune cells in gastric cancer, and these variations were likely to be important clues for prognosis and management of its future clinical implementation.

Biomarkers in Immunotherapy-Based Precision Treatments of Digestive System Tumors

Immunotherapy, represented by immune checkpoint inhibitors (mainly referring to programmed death-1 (PD-1)/programmed death-ligand 1 (PD-L1) blockades), derives durable remission and survival benefits for multiple tumor types including digestive system tumors [gastric cancer (GC), colorectal cancer (CRC), and hepatocellular carcinoma (HCC)], particularly those with metastatic or recurrent lesions. Even so, not all patients would respond well to anti-programmed death-1/programmed death-ligand 1 agents (anti-PD-1/PD-L1) in gastrointestinal malignancies, suggesting the need for biomarkers to identify the responders and non-responders, as well as to predict the clinical outcomes. PD-L1expression has increasingly emerged as a potential biomarker when predicting the immunotherapy-based efficacy; but regrettably, PD-L1 alone is not sufficient to differentiate patients. Other molecules, such as tumor mutational burden (TMB), microsatellite instability (MSI), and circulating tumor DNA (ctDNA) as well, are involved in further explorations. Overall, there are not still no perfect or well-established biomarkers in immunotherapy for digestive system tumors at present as a result of the inherent limitations, especially for HCC. Standardizing and harmonizing the assessments of existing biomarkers, and meanwhile, switching to other novel biomarkers are presumably wise and feasible.

Screening of Potential Biomarkers for Gastric Cancer with Diagnostic Value Using Label-free Global Proteome Analysis

Gastric cancer (GC) is known as a top malignant type of tumors worldwide. Despite the recent decrease in mortality rates, the prognosis remains poor. Therefore, it is necessary to find novel biomarkers with early diagnostic value for GC. In this study, we present a large-scale proteomic analysis of 30 GC tissues and 30 matched healthy tissues using label-free global proteome profiling. Our results identified 537 differentially expressed proteins, including 280 upregulated and 257 downregulated proteins. The ingenuity pathway analysis (IPA) results indicated that the sirtuin signaling pathway was the most activated pathway in GC tissues whereas oxidative phosphorylation was the most inhibited. Moreover, the most activated molecular function was cellular movement, including tissue invasion by tumor cell lines. Based on IPA results, 15 hub proteins were screened. Using the receiver operating characteristic curve, most of hub proteins showed a high diagnostic power in distinguishing between tumors and healthy controls. A four-protein (ATP5B-ATP5O-NDUFB4-NDUFB8) diagnostic signature was built using a random forest model. The area under the curve (AUC) values of this model were 0.996 and 0.886 for the training and testing sets, respectively, suggesting that the four-protein signature has a high diagnostic power. This signature was further tested with independent datasets using plasma enzyme-linked immune sorbent assays, resulting in an AUC value of 0.778 for distinguishing GC tissues from healthy controls, and using immunohistochemical tissue microarray analysis, resulting in an AUC value of 0.805. In conclusion, this study identifies potential biomarkers and improves our understanding of the pathogenesis, providing novel therapeutic targets for GC.

Immune Checkpoint Inhibition in Oesophago-Gastric Carcinoma

Immune checkpoint inhibitors enrich the therapeutic landscape in oesophago-gastric carcinoma. With regard to oesophageal squamous cell carcinoma (ESCC), the selective PD-1 (programmed cell death receptor 1)-inhibitor nivolumab improves disease-free survival in the adjuvant therapy setting (CHECKMATE-577). In first-line treatment, ESCC patients (pts) benefit in overall survival (OS) from the PD-1-inhibitor pembrolizumab in combination with chemotherapy (KEYNOTE-590). In the second-line setting, nivolumab (ATTRACTION-03) and pembrolizumab (KEYNOTE-181) demonstrate a benefit in OS compared with chemotherapy. These data resulted in the approval of nivolumab for the second-line treatment of advanced ESCC pts regardless of PD-L1 (programmed cell death ligand 1) status in Europe, Asia, and the USA, and pembrolizumab for pts with PD-L1 CPS (combined positivity score) ≥ 10 in Asia and the USA. Further approvals can be expected. In gastro-oesophageal junction and gastric cancer, the addition of nivolumab to chemotherapy in first-line treatment improves OS in pts with advanced disease with PD-L1 CPS ≥ 5 (CHECKMATE-649). Additionally, pembrolizumab was non-inferior to chemotherapy for OS in PD-L1 CPS ≥ 1 pts (KEYNOTE-062). In third-line treatment, nivolumab shows benefits in OS regardless of PD-L1 expression (ATTRACTION-02) with approval in Asia, and pembrolizumab prolonged the duration of response in PD-L1 positive pts (KEYNOTE-059) with approval in the USA. We discuss the recent results of the completed phase II and III clinical trials.

Immunotherapy of gastric cancer: Past, future perspective and challenges

Gastric cancer is considered as the third leading cause of deaths and the fifth most common cancers worldwide. Common treatment approaches include chemotherapy, radiation, gastric resection and targeted therapies. The emergence of gastric cancer immunotherapy has already shown some promising results and have altered the therapeutic procedures. Now, different combination therapies as well as novel immunotherapies targeting new molecules have been proposed. Despite ongoing investigations on the therapeutic options and significant advancements in this regard, the disease is poorly prognosed. In fact, limited therapeutic options and delayed diagnosis lead to the progression, dissemination and metastasis of the disease. Current immunotherapies are mostly based on cytotoxic immunocytes, monoclonal antibodies and gene transferred vaccines. The use of Immune checkpoint inhibitors (ICIs) have grown rapidly. In this review, we aimed to explore perspective and progression of different approaches of immunotherapy in the treatment of GC and the clinical outcomes reported so far. We also summarized the tumor immunosurveillance and tumor immunoescape.

Exosomal miRNA-16-5p Derived From M1 Macrophages Enhances T Cell-Dependent Immune Response by Regulating PD-L1 in Gastric Cancer

Macrophages have an affinity to developing tumors and have been shown to play a role in tumor combat and immune surveillance. However, the exact mechanism by which macrophages participate in the anti-tumor immune response remains unclear. Hence, the current study aimed to identify the effect of macrophages on gastric cancer (GC) cells via exosomes. Paired cancerous, tumor-adjacent, and non-cancerous stomach tissues were initially from 68 GC patients. T cells were isolated from peripheral blood mononuclear cells (PBMCs) obtained from both the GC patients as well as the healthy donors. Next, the exosomes were isolated from LPS and IFN-γ-induced PBMCs (M1 macrophages) and co-cultured with human GC cells. Another co-culture system comprised of CD3⁺ T cells and exosomes-treated GC cells was then performed. BALB/c mice and NOD/SCID nude mice were prepared for effects of exosomal miR-16-5p on tumor growth and anti-tumor immune response in GC in vivo. A relationship between M1 macrophages and the poor survival of GC patients was identified, while they secreted exosomes to inhibit GC development and activate a T cell-dependent immune response. Our results revealed that miR-16-5p was transferred intercellularly from M1 macrophages to GC cells via exosomes and targeted PD-L1. M1 macrophage-derived exosomes containing miR-16-5p were found to trigger a T cell immune response which inhibited tumor formation both in vitro and in vivo by decreasing the expression of PD-L1. Taken together, the key findings of the current study suggest that M1 macrophage-derived exosomes carrying miR-16-5p exert an inhibitory effect on GC progression through activation of T cell immune response via PD-L1. Our study highlights the promise of M1 macrophages as a potential cell-based therapy for GC treatment by increasing miR-16-5p in exosomes.

Immunotherapy for older patients with melanoma: From darkness to light?

Approximately 40% of malignant melanomas are diagnosed in patients older than 65 years. Elderly patients with melanoma present clinicopathological features related to a more aggressive biology, and they are often diagnosed with advanced stage of disease. Interestingly, in older patients the immune system can be altered with changes both in the innate system and in the adaptive immune system with the acquisition of a pro-inflammatory and immune suppressive phenotype. Immunotherapy with immune checkpoint inhibitors has reshaped the treatment strategies and prognosis of patients with melanoma, and particularly, older age should not be considered a contraindication for immunotherapy. However, data regarding efficacy and safety of immunotherapy in elderly population are still limited because frail older patients are generally excluded from clinical trials. Recently, real-world data have shed light on similar efficacy and safety of immunotherapy in older population compared with younger counterpart. The aim of the present review was to summarize the available knowledge on the underlying immune system in older patients with a diagnosis of melanoma and the immunotherapeutic approaches in this population.

The SENECA study: Prognostic role of serum biomarkers in older patients with metastatic colorectal cancer

BACKGROUND

Aging induces meaningful changes in the immune system and inflammation response with increase in monocyte-lymphocyte ratio (MLR) and serum lactate dehydrogenase (LDH) levels. Aim of this study was to explore the prognostic role of MLR and LDH levels in older patients (pts) with metastatic colorectal cancer (mCRC).

METHODS

We conducted a retrospective analysis of a consecutive cohort of 168 older (>70 years) patients with mCRC. The prognostic impact of MLR and LDH levels on overall survival (OS) was investigated through uni-and multivariate Cox regression analyses. Moreover, we categorized patients into three groups according to MLR and LDH levels (group 1: MLR-low and LDH-low; group 2: MLR-high or LDH-high; group 3: MLR-high and LDH-high).

RESULTS

By univariate analysis, high LDH level (HR 1.74, 95% CI 1.05-2.90) and high MLR level (HR 2.19, 95% CI 1.48-3.44) were significantly associated with a worse OS. Conversely, primary tumor resection and left-sidedness were significantly associated with a longer OS. By multivariate analysis, high LDH level (HR 2.00, 95% CI 1.13-3.55) and high MLR level (HR 2.99, 95% CI 1.68-5.33) were independent prognostic factors of worse prognosis. Compared to group 1, a shorter survival was reported for patients included in group 2 (HR 1.97, 95% CI 1.21-3.23 in univariate; HR 2.54, 95% CI 1.43-4.51 in multivariate) or in group 3 (HR 2.42, 95% CI 24-4.74, p = .010 in univariate; HR 5.59, 95% CI 2.15-14.54 in multivariate) CONCLUSIONS: High baseline levels of LDH, MLR or both are independent unfavorable prognostic factors in older patients treated with first-line chemotherapy for mCRC.

Dynamic monitoring of serum soluble programmed cell death ligand 1 as a response predictor to chemotherapy in metastatic or recurrent gastrointestinal cancer

Background

Biomarkers in serum may have important clinical implications for personalized medicine, including therapeutic guidance, and monitoring of recurrence. The role of programmed cell death ligand 1 (PD-L1) expression as a tumor biomarker remains controversial. In this study, we aimed at determining the changes of soluble PD-L1 (sPD-L1) during first-line chemotherapy and assessing the association with treatment response and progression-free survival (PFS) of patients with advanced gastrointestinal cancer.

Methods

Blood samples from 115 gastrointestinal cancer patients who have not received any previous systemic chemotherapy for recurrent or metastatic disease were collected at the time of diagnosis and each response evaluation. Serum of sPD-L1 expression was tested by enzyme-linked immunosorbent assay (ELISA). The associations between the baseline level of serum sPD-L1 and clinical-pathological characteristics and prognosis were analyzed. we further dynamically monitored the level change of serum sPD-L1 during treatment and analyzed its relationship with clinical-pathological characteristics, chemotherapy response and prognosis.

Results

Among 115 metastatic gastrointestinal patients, the median serum sPD-L1 level was 0.777 (range, <0.156–6.680) ng/mL. In most cases, changes in sPD-L1 level correlated with treatment response. Patients with values of serum sPD-L1 decreasing after chemotherapy had better tumor response and median PFS compared with patients with values increasing after chemotherapy (ORR, 88.3% vs. 54.0% P=0.000005 and PFS, not reached vs. 27 months, P=0.00026). D-values of sPD-L1 in patients with progressive disease (PD) were observed increasing from 0.406 to 1.097 ng/mL between pre- and post-chemotherapy, while in those with better tumor response D-values decreased from 1.153 to 0.791 ng/mL after chemotherapy compared with baseline. In the logistic regression analysis, the change of sPD-L1 levels in serum after chemotherapy were found to be a prognostic factor for treatment response and PFS in the multivariate analysis.

Conclusions

These results showed for the first time that sPD-L1 in serum samples of patients with advanced gastrointestinal cancer were changed after chemotherapy and increased serum sPD-L1 levels were poor prognostic factors for both tumor response and PFS of patients. Dynamic monitoring of serum sPDL1 after treatment may be served as a potential predictor to treatment response in gastrointestinal cancer patients.

Third- and later-line treatment in advanced or metastatic gastric cancer: a systematic review and meta-analysis

Aim: We performed a systematic review and meta-analysis to investigate the efficacy and safety of third-line (TLT) and salvage treatment (ST) in advanced or metastatic gastric cancer. Materials & methods: Eligible studies included randomized clinical trials assessing TLT and ST versus placebo or best supportive care. Outcomes of interest included: overall survival, objective response rate and disease control rate in TLT; progression-free survival in ST; grade 3-4 adverse events in ST. Results: The use of TLT and ST was superior to placebo or best supportive care in terms of prolonging overall survival and progression-free survival. Hematological toxicities were more frequent in ST. Conclusion: TLT and ST are considerable and tolerable treatment options for patients with advanced or metastatic gastric cancer. Given the substantial heterogeneities affecting the efficacy analyses, these results have to be interpreted cautiously.

A Pan-Cancer Approach to Predict Responsiveness to Immune Checkpoint Inhibitors by Machine Learning

Immunotherapy by using immune checkpoint inhibitors (ICI) has dramatically improved the treatment options in various cancers, increasing survival rates for treated patients. Nevertheless, there are heterogeneous response rates to ICI among different cancer types, and even in the context of patients affected by a specific cancer. Thus, it becomes crucial to identify factors that predict the response to immunotherapeutic approaches. A comprehensive investigation of the mutational and immunological aspects of the tumor can be useful to obtain a robust prediction. By performing a pan-cancer analysis on gene expression data from the Cancer Genome Atlas (TCGA, 8055 cases and 29 cancer types), we set up and validated a machine learning approach to predict the potential for positive response to ICI. Support vector machines (SVM) and extreme gradient boosting (XGboost) models were developed with a 10×5-fold cross-validation schema on 80% of TCGA cases to predict ICI responsiveness defined by a score combining tumor mutational burden and TGF- β signaling. On the remaining 20% validation subset, our SVM model scored 0.88 accuracy and 0.27 Matthews Correlation Coefficient. The proposed machine learning approach could be useful to predict the putative response to ICI treatment by expression data of primary tumors.

An Accurate and Comprehensive Clinical Sequencing Assay for Cancer Targeted and Immunotherapies

BACKGROUND

Incorporation of next-generation sequencing (NGS) technology into clinical utility in targeted and immunotherapies requires stringent validation, including the assessment of tumor mutational burden (TMB) and microsatellite instability (MSI) status by NGS as important biomarkers for response to immune checkpoint inhibitors.

MATERIALS AND METHODS

We designed an NGS assay, Cancer Sequencing YS panel (CSYS), and applied algorithms to detect five classes of genomic alterations and two genomic features of TMB and MSI.

RESULTS

By stringent validation, CSYS exhibited high sensitivity and predictive positive value of 99.7% and 99.9%, respectively, for single nucleotide variation; 100% and 99.9%, respectively, for short insertion and deletion (indel); and 95.5% and 100%, respectively, for copy number alteration (CNA). Moreover, CSYS achieved 100% specificity for both long indel (50-3,000 bp insertion and deletion) and gene rearrangement. Overall, we used 33 cell lines and 208 clinical samples to validate CSYS's NGS performance, and genomic alterations in clinical samples were also confirmed by fluorescence in situ hybridization, immunohistochemistry, and polymerase chain reaction (PCR). Importantly, the landscape of TMB across different cancers of Chinese patients (n = 3,309) was studied. TMB by CSYS exhibited a high correlation (Pearson correlation coefficient r = 0.98) with TMB by whole exome sequencing (WES). MSI measurement showed 98% accuracy and was confirmed by PCR. Application of CSYS in a clinical setting showed an unexpectedly high occurrence of long indel (6.3%) in a cohort of tumors from Chinese patients with cancer (n = 3,309), including TP53, RB1, FLT3, BRCA2, and other cancer driver genes with clinical impact.

CONCLUSION

CSYS proves to be clinically applicable and useful in disclosing genomic alterations relevant to cancer target therapies and revealing biomarkers for immune checkpoint inhibitors.

IMPLICATIONS FOR PRACTICE

The study describes a specially designed sequencing panel assay to detect genomic alterations and features of 450 cancer genes, including its overall workflow and rigorous clinical and analytical validations. The distribution of pan-cancer tumor mutational burden, microsatellite instability, gene rearrangement, and long insertion and deletion mutations was assessed for the first time by this assay in a broad array of Chinese patients with cancer. The Cancer Sequencing YS panel and its validation study could serve as a blueprint for developing next-generation sequencing-based assays, particularly for the purpose of clinical application.

Prognostic significance of tumor immune microenvironment and immunotherapy: Novel insights and future perspectives in gastric cancer

Despite a decrease in gastric cancer incidence, the development of novel biologic agents and combined therapeutic strategies, the prognosis of gastric cancer remains poor. Recently, the introduction of modern immunotherapy, especially using immune checkpoint inhibitors, led to an improved prognosis in many cancers. The use of immunotherapy was also associated with manageable adverse event profiles and promising results in the treatment of patients with gastric cancer, especially in heavily pretreated patients. These data have led to an accelerated approval of some checkpoint inhibitors in this setting. Understanding the complex relationship between the host immune microenvironment and tumor and the immune escape phenomenon leading to cancer occurrence and progression will subsequently lead to the identification of prognostic immune markers. Furthermore, this understanding will result in the discovery of both new mechanisms for blocking tumor immunosuppressive signals and pathways to stimulate the local immune response by targeting and modulating different subsets of immune cells. Due to the molecular heterogeneity of gastric cancers associated with different clinico-biologic parameters, immune markers expression and prognosis, novel immunotherapy algorithms should be personalized and addressed to selected subsets of gastric tumors, which have been proven to elicit the best clinical responses. Future perspectives in the treatment of gastric cancer include tailored dual immunotherapies or a combination of immunotherapy with other targeted agents with synergistic antitumor effects.

Molecular biomarkers in gastro-esophageal cancer: recent developments, current trends and future directions

Gastro-esophageal adenocarcinomas (GEA) represent a severe global health burden and despite improvements in the multimodality treatment of these malignancies the prognosis of patients remains poor. HER2 overexpression/amplification has been the first predictive biomarker approved in clinical practice to guide patient selection for targeted treatment with trastuzumab in advanced gastric and gastro-esophageal junction cancers. More recently, immunotherapy has been approved for the treatment of GEA and PD-L1 expression is now a biomarker required for the administration of pembrolizumab in these diseases. Significant progress has been made in recent years in dissecting the genomic makeup of GEA in order to identify distinct molecular subtypes linked to distinct patterns of molecular alterations. GEA have been found to be highly heterogeneous malignances, representing a challenge for biomarkers discovery and targeted treatment development. The current review focuses on an overview of established and novel promising biomarkers in GEA, covering recent molecular classifications from TCGA and ACRG. Main elements of molecular heterogeneity are discussed, as well as emerging mechanisms of primary and secondary resistance to HER2 targeted treatment and recent biomarker-driven trials. Future perspectives on the role of epigenetics, miRNA/lncRNA and liquid biopsy, and patient-derived xenograft models as a new platform for molecular-targeted drug discovery in GEA are presented. Our knowledge on the genomic landscape of GEA continues to evolve, uncovering the high heterogeneity and deep complexity of these tumors. The availability of new technologies and the identification of promising novel biomarker will be critical to optimize targeted treatment development in a setting where therapeutic options are currently lacking. Nevertheless, clinical validation of novel biomarkers and treatment strategies still represents an issue.

Immunotherapy for Gastric Cancer: Time for a Personalized Approach?

Over the last decade, our understanding of the mechanisms underlying immune modulation has greatly improved, allowing for the development of multiple therapeutic approaches that are revolutionizing the treatment of cancer. Immunotherapy for gastric cancer (GC) is still in the early phases but is rapidly evolving. Recently, multi-platform molecular analyses of GC have proposed a new classification of this heterogeneous group of tumors, highlighting subset-specific features that may more reliably inform therapeutic choices, including the use of new immunotherapeutic drugs. The clinical benefit and improved survival observed in GC patients treated with immunotherapeutic strategies and their combination with conventional therapies highlighted the importance of the immune environment surrounding the tumor. A thorough investigation of the tumor microenvironment and the complex and dynamic interaction between immune cells and tumor cells is a fundamental requirement for the rational design of novel and more effective immunotherapeutic approaches. This review summarizes the pre-clinical and clinical results obtained so far with immunomodulatory and immunotherapeutic treatments for GC and discusses the novel combination strategies that are being investigated to improve the personalization and efficacy of GC immunotherapy.

Characterizing Metastatic HER2-Positive Gastric Cancer at the CDH1 Haplotype

The CDH1 gene, coding for the E-cadherin protein, is linked to gastric cancer (GC) susceptibility and tumor invasion. The human epidermal growth factor receptor 2 (HER2) is amplified and overexpressed in a portion of GC. HER2 is an established therapeutic target in metastatic GC (mGC). Trastuzumab, in combination with various chemotherapeutic agents, is a standard treatment for these tumors leading to outcome improvement. Unfortunately, the survival benefit is limited to a fraction of patients. The aim of this study was to improve knowledge of the HER2 and the E-cadherin alterations in the context of GC to characterize subtypes of patients that could better benefit from targeted therapy. An association between the P7-CDH1 haplotype, including two polymorphisms (rs16260A-rs1801552T) and a subset of HER2-positive mGC with better prognosis was observed. Results indicated the potential evaluation of CDH1 haplotypes in mGC to stratify patients that will benefit from trastuzumab-based treatments. Moreover, data may have implications to understanding the HER2 and the E-cadherin interactions in vivo and in response to treatments.

Outcomes of Advanced Gastric Cancer Patients Treated with at Least Three Lines of Systemic Chemotherapy

BACKGROUND

Second-line therapy has consistently demonstrated survival benefit if compared with best supportive care; however, there is limited evidence whether further lines of treatment may improve the prognosis of advanced gastric cancer (AGC) patients.

MATERIALS AND METHODS

Starting from a real-world cohort of 868 AGC patients, we retrospectively analyzed baseline parameters, tumor characteristics, and treatment data of those treated with at least three lines. Categorical features were described through cross-tables and chi-square test. We explored the impact of treatment intensity and progression-free survival (PFS) experienced in previous lines on PFS and overall survival in third-line by uni- and multivariate Cox regression models and described by Kaplan-Meier estimator plot with log-rank test.

RESULTS

Overall, 300 patients were included in the analysis. The most common site of primary tumor was gastric body; 45.3% of cancers had an intestinal histotype, 14% were human epidermal growth receptor 2 positive. In third-line, 45.7% of patients received a single-agent chemotherapy, 49.7% a combination regimen. Patients who had experienced a first-line PFS ≥6.9 months had a better prognosis compared with those who had achieved a shorter one. Consistently, a second-line PFS ≥3.5 months positively influenced the prognosis. Patients receiving a third-line combination regimen had better outcomes compared with those treated with a single-agent chemotherapy.

CONCLUSION

Our real-world study confirms that selected AGC patients may receive third-line treatment. Longer PFS in previous lines or a more intense third-line treatment positively influenced prognosis. Further efforts are warranted to define the best therapeutic sequences, and to identify the optimal candidate for treatment beyond second-line.

IMPLICATIONS FOR PRACTICE

The benefit of third-line treatment to advanced gastric cancer patients is controversial. This study depicts a real scenario of the clinical practice in Italy, confirming that a non-negligible proportion of patients receive a third-line therapy. Longer progression-free survival in previous treatment lines or higher third-line treatment intensity positively influenced prognosis. Including a large number of real-world patients, this study provides information on third-line treatment from the daily clinical practice; moreover, its results help in defining the best therapeutic sequence and offer some hints to select the optimal candidate for treatment beyond second-line.

Immunotherapy in Gastrointestinal Cancers

Gastrointestinal cancers represent a major public health problem worldwide. Immunotherapeutic strategies are currently under investigation in this setting and preliminary results of ongoing trials adopting checkpoint inhibitors are striking. Indeed, although a poor immunogenicity for GI has been reported, a strong biological rationale supports the development of immunotherapy in this field. The clinical and translational research on immunotherapy for the treatment of GI cancers started firstly with the identification of immune-related mechanisms possibly relevant to GI tumours and secondly with the development of immunotherapy-based agents in clinical trials. In the present review a general overview is firstly provided followed by a focus on major findings on gastric, colorectal, and hepatocellular carcinomas. Finally, pathological and molecular perspectives are provided since many efforts are ongoing in order to identify possible predictive biomarkers and to improve patients' selection. Many issues are still unsolved in this field; however, we strongly believe that immunotherapy might positively affect the natural history of a subgroup of GI cancer patients improving outcome and the overall quality of life.