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Gastric cancer and gastro-oesophageal junction cancer represent a global health-care challenge. Despite the efficacy of improved chemotherapy and surgical options, these patients still have a poor prognosis. In advanced disease, only trastuzumab and some immune checkpoint inhibitors, such as nivolumab and pembrolizumab in addition to chemotherapy, have demonstrated consistent and reliable efficacy in patients with HER2-positive and PDL1-positive tumours, respectively. In this Review, we discuss the intrinsic characteristics of gastric and gastro-oesophageal cancer from the molecular and clinical perspectives and provide a comprehensive review of previously reported and ongoing phase II and III clinical trials with targeted agents and immunotherapy in advanced and localized settings. Finally, we suggest alternative strategies to help overcome current challenges in precision medicine and to improve outcomes for these patients.Gastric and gastro-oesophageal cancer is a leading cause of cancer-related death worldwide with a poor prognosis. This Review provides a comprehensive overview of current treatment strategies set on a molecular basis, and discusses future therapeutic avenues.

Despite neoadjuvant/conversion chemotherapy, the prognosis of cT4a/bN+ gastric cancer is poor. Immune checkpoint inhibitors (ICIs) and antiangiogenic agents have shown activity in late-stage gastric cancer, but their efficacy in the neoadjuvant/conversion setting is unclear. In this single-armed, phase II, exploratory trial (NCT03878472), we evaluate the efficacy of a combination of ICI (camrelizumab), antiangiogenesis (apatinib), and chemotherapy (S-1 ± oxaliplatin) for neoadjuvant/conversion treatment of cT4a/bN+ gastric cancer. The primary endpoints are pathological responses and their potential biomarkers. Secondary endpoints include safety, objective response, progression-free survival, and overall survival. Complete and major pathological response rates are 15.8% and 26.3%. Pathological responses correlate significantly with microsatellite instability status, PD-L1 expression, and tumor mutational burden. In addition, multi-omics examination reveals several putative biomarkers for pathological responses, including RREB1 and SSPO mutation, immune-related signatures, and a peripheral T cell expansion score. Multi-omics also demonstrates dynamic changes in dominant tumor subclones, immune microenvironments, and T cell receptor repertoires during neoadjuvant immunotherapy. The toxicity and post-surgery complications are limited. These data support further validation of ICI- and antiangiogenesis-based neoadjuvant/conversion therapy in large randomized trials and provide candidate biomarkers. Immune checkpoint inhibitors and antiangiogenic agents have shown some activity in patients with late-stage gastric cancer. Here the authors report the results of a phase II trial of neoadjuvant anti-PD1 (camrelizumab), antiangiogenic agent (apatinib), and chemotherapy (S-1 ± Oxaliplatin) in stage T4a/bN + M0 gastric cancer patients.

Claudin 18.2, a tight-junction molecule predominantly found in the nonmalignant gastric epithelium, becomes accessible on the tumour cell surface during malignant transformation, thereby providing an appealing target for cancer therapy. Data from two phase III trials testing the anti-claudin 18.2 antibody zolbetuximab have established claudin 18.2-positive advanced-stage gastric cancers as an independent therapeutic subset that derives benefit from the addition of this agent to chemotherapy. This development has substantially increased the percentage of patients eligible for targeted therapy. Furthermore, newer treatments, such as high-affinity monoclonal antibodies, bispecific antibodies, chimeric antigen receptor T cells and antibody–drug conjugates capable of bystander killing effects, have shown considerable promise in patients with claudin 18.2-expressing gastric cancers. This new development has resulted from drug developers moving beyond traditional targets, such as driver gene alterations or growth factors. In this Review, we highlight the biological rationale and explore the clinical activity of therapies that target claudin 18.2 in patients with advanced-stage gastric cancer and explore the potential for expansion of claudin 18.2-targeted therapies to patients with other claudin 18.2-positive solid tumours.The development and successful phase III testing of the anti-claudin 18.2 antibody zolbetuximab has provided a novel targeted therapy for the 30–40% of patients with strongly claudin 18.2-positive gastric cancers. Furthermore, the development of an effective targeted therapy for a target that does not have a driver role in cancer development provides a novel drug development paradigm. In this Review, the authors describe the development of claudin 18.2-targeted therapies, including zolbetuximab, as well as novel therapies, including chimeric antigen receptor (CAR) T cells, antibody–drug conjugates and bispecific antibodies, all of which have the potential to expand the number of patients who can derive benefit from claudin 18.2-targeted therapies in the near future.

Epstein–Barr virus-associated gastric cancer (EBVaGC) shows a robust response to immune checkpoint inhibitors. Therefore, a cost-efficient and accessible tool is needed for discriminating EBV status in patients with gastric cancer. Here we introduce a deep convolutional neural network called EBVNet and its fusion with pathologists for predicting EBVaGC from histopathology. The EBVNet yields an averaged area under the receiver operating curve (AUROC) of 0.969 from the internal cross validation, an AUROC of 0.941 on an external dataset from multiple institutes and an AUROC of 0.895 on The Cancer Genome Atlas dataset. The human-machine fusion significantly improves the diagnostic performance of both the EBVNet and the pathologist. This finding suggests that our EBVNet could provide an innovative approach for the identification of EBVaGC and may help effectively select patients with gastric cancer for immunotherapy. Epstein–Barr virus-associated gastric cancer shows a robust response to immune checkpoint inhibitors. Here the authors introduce a deep convolutional neural network and its fusion with pathologists for predicting it from histopathology.

Liquid biopsies are providing new opportunities for detection of residual disease in cell-free DNA (cfDNA) after surgery but may be confounded through identification of alterations arising from clonal hematopoiesis. Here, we identify circulating tumor-derived DNA (ctDNA) alterations through ultrasensitive targeted sequencing analyses of matched cfDNA and white blood cells from the same patient. We apply this approach to analyze samples from patients in the CRITICS trial, a phase III randomized controlled study of perioperative treatment in patients with operable gastric cancer. After filtering alterations from matched white blood cells, the presence of ctDNA predicts recurrence when analyzed within nine weeks after preoperative treatment and after surgery in patients eligible for multimodal treatment. These analyses provide a facile method for distinguishing ctDNA from other cfDNA alterations and highlight the utility of ctDNA as a predictive biomarker of patient outcome to perioperative cancer therapy and surgical resection in patients with gastric cancer. Identifying patients that will respond to a particular therapy remains a key challenge in precision oncology. Here, in gastric cancer, the authors show that circulating tumour DNA can predict recurrence, provided that the signal from white blood cells is filtered out.

The synergistic effect of neoadjuvant immunotherapy and chemoradiotherapy in gastric adenocarcinoma is unclear. This phase II trial (NCT03631615) investigated this neoadjuvant combination in locally advanced adenocarcinoma of stomach or gastroesophageal junction. Thirty-six patients received capecitabine 850 mg/m 2 twice daily and simultaneous radiotherapy for 5 weeks, sandwiched by a 21-day cycle of oxaliplatin 130 mg/m 2 (day 1) plus capecitabine 1000 mg/m 2 twice daily (days 1–14), respectively, followed by surgery. Camrelizumab 200 mg (day 1) was given for 5 cycles since initiating chemotherapy. Primary endpoint was pathological complete response (pCR, ypT0) rate. Secondary endpoints included total pCR (tpCR, ypT0N0) rate, major pathological response (MPR, < 10% residual tumor cells) rate, margin-free (R0) resection rate, downstaging, progression-free survival (PFS), overall survival (OS), and safety. The pCR rate was 33.3% (95% CI, 18.6–51.0), meeting pre-specified endpoint. TpCR, MPR, and R0 resection rates were 33.3%, 44.4%, and 91.7%, respectively. Twenty-eight (77.8%) patients reached ypN0. Two-year PFS and OS rates were 66.9% and 76.1%, respectively. The most common grade 3–4 adverse event was decreased lymphocyte count (27 [75.0%]). Neoadjuvant camrelizumab plus concurrent chemoradiotherapy exhibits promising pathological response in patients with locally advanced gastric adenocarcinoma, with an acceptable safety profile. Surgery is an important part of treatment for gastric adenocarcinoma, however, the consensus on perioperative care is less clear. Here, the authors report the results of a phase II clinical trial investigating neoadjuvant camrelizumab with concurrent chemoradiotherapy, followed by surgery for the treatment of advanced gastric adenocarcinoma.

Prospective evidence regarding the combination of programmed cell death (PD)−1 and angiogenesis inhibitors in treating locally advanced gastric cancer (LAGC) is limited. In this multicenter, randomized, phase 2 trial (NCT04195828), patients with gastric adenocarcinoma (clinical T2-4N + M0) were randomly assigned (1:1) to receive neoadjuvant camrelizumab and apatinib combined with nab-paclitaxel plus S-1 (CA-SAP) or chemotherapy SAP alone (SAP) for 3 cycles. The primary endpoint was the major pathological response (MPR), defined as <10% residual tumor cells in resection specimens. Secondary endpoints included R0 resection rate, radiologic response, safety, overall survival, and progression-free survival. The modified intention-to-treat population was analyzed (CA-SAP [ n  = 51] versus SAP [ n  = 53]). The trial has met pre-specified endpoints. CA-SAP was associated with a significantly higher MPR rate (33.3%) than SAP (17.0%, P  = 0.044). The CA-SAP group had a significantly higher objective response rate (66.0% versus 43.4%, P  = 0.017) and R0 resection rate (94.1% versus 81.1%, P  = 0.042) than the SAP group. Nonsurgical grade 3-4 adverse events were observed in 17 patients (33.3%) in the CA-SAP group and 14 (26.4%) in the SAP group. Survival results were not reported due to immature data. Camrelizumab and apatinib combined with chemotherapy as a neoadjuvant regimen was tolerable and associated with favorable responses for LAGC. Neoadjuvant treatment represents a therapeutic option for locally advanced gastric cancer (LAGC). Here the authors report the results of a randomized phase 2 trial of camrelizumab (anti-PD1) and apatinib (anti-VEGFR2) combined with nab-paclitaxel plus S-1 versus chemotherapy alone as neoadjuvant treatment for LAGC.

Background Claudin-18 (CLDN18) is a highly specific tight junction protein of the gastric mucosa. An isoform of CLDN18, the Claudin 18.2, has recently emerged as an innovative drug target for metastatic gastric cancer. Methods We investigated the immunohistochemical profile of CLDN18, p53, p16, E-cadherin, MSH2, MSH6, MLH1, PSM2, HER2, and PDL-1 in a large series of 523 primary gastric carcinomas (GCs; n  = 408) and gastro-oesophageal carcinomas (GECs; n  = 115) and 135 matched and synchronous nodal metastases. The status of HER2 and EBER by means of chromogenic in situ hybridisation (CISH) was also evaluated. Results High membranous CLDN18 expression was present in 150/510 (29.4%) primary cases and in 45/132 (34.1%) metastases. An abnormal expression (i.e. nuclear and/or cytoplasmic) was observed in 115 (22.5%) primary cases and in 33 (25.0%) metastases. A 38.8% of the cases showed significant CLDN18 intratumoural variability among the different tissue microarray cores obtained from the same tumour. Positive membrane CLDN18 expression was statistically associated with non-antral GCs ( p  = 0.016), Lauren diffuse type ( p  = 0.009), and with EBV-associated cancers ( p  < 0.001). Conclusions CLDN18 is frequently expressed in gastric and gastro-oesophageal cancers; further studies should investigate the prognostic significance of CLDN18 heterogeneity in order to implement its test into clinical practice.

Targetable drivers governing 5-fluorouracil and cisplatin (5FU + CDDP) resistance remain elusive due to the paucity of physiologically and therapeutically relevant models. Here, we establish 5FU + CDDP resistant intestinal subtype GC patient-derived organoid lines. JAK/STAT signaling and its downstream, adenosine deaminases acting on RNA 1 (ADAR1), are shown to be concomitantly upregulated in the resistant lines. ADAR1 confers chemoresistance and self-renewal in an RNA editing-dependent manner. WES coupled with RNA-seq identify enrichment of hyper-edited lipid metabolism genes in the resistant lines. Mechanistically, ADAR1-mediated A-to-I editing on 3’UTR of stearoyl-CoA desaturase (SCD1) increases binding of KH domain-containing, RNA-binding, signal transduction-associated 1 (KHDRBS1), thereby augmenting SCD1 mRNA stability. Consequently, SCD1 facilitates lipid droplet formation to alleviate chemotherapy-induced ER stress and enhances self-renewal through increasing β-catenin expression. Pharmacological inhibition of SCD1 abrogates chemoresistance and tumor-initiating cell frequency. Clinically, high proteomic level of ADAR1 and SCD1, or high SCD1 editing/ADAR1 mRNA signature score predicts a worse prognosis. Together, we unveil a potential target to circumvent chemoresistance. Resistance to 5-fluorouracil and cisplatin (5FU + CDDP) presents a major issue in patients with gastric cancer. Here, the authors establish 5FU + CDDP resistant intestinal gastric cancer patient-derived organoids and identify JAK/STAT-ADAR1 altered lipid metabolism as a regulator of chemoresistance.

Gastric signet ring cell carcinoma (GSRC) is a special subtype of gastric cancer (GC) associated with poor prognosis, but an in-depth and systematic study of GSRC is lacking. Here, we perform single-cell RNA sequencing to assess GC samples. We identify signet ring cell carcinoma (SRCC) cells. Microseminoprotein-beta ( MSMB ) can be used as a marker gene to guide the identification of moderately/poorly differentiated adenocarcinoma and signet ring cell carcinoma (SRCC). The upregulated differentially expressed genes in SRCC cells are mainly enriched in abnormally activated cancer-related signalling pathways and immune response signalling pathways. SRCC cells are also significantly enriched in mitogen-activated protein kinase and oestrogen signalling pathways, which can interact and promote each other in a positive feedback loop. SRCC cells are shown to have lower cell adhesion and higher immune evasion capabilities as well as an immunosuppressive microenvironment, which may be closely associated with the relatively poor prognosis of GSRC. In summary, GSRC exhibits unique cytological characteristics and a unique immune microenvironment, which may be advantageous for accurate diagnosis and treatment. The tumour microenvironment in signet ring cell carcinoma (SRCC) remains to be characterised. Here, the authors perform single-cell RNA sequencing and reveal distinct features compared to moderately/poorly differentiated adenocarcinoma.