PD-L1 is an independent prognostic predictor in gastric cancer of Western patients

Low Expression of Programmed Death 1 (PD-1), PD-1 Ligand 1 (PD-L1), and Low CD8+ T Lymphocyte Infiltration Identify a Subgroup of Patients With Gastric and Esophageal Adenocarcinoma With Severe Prognosis

Prognosis of gastric and esophageal cancer is poor and treatment improvements are needed. Programmed cell death 1 receptor (PD-1) interaction with its ligand PD-L1 in tumor micro-environment promotes immune tolerance and blocking monoclonal antibodies have entered clinical practice. However, clinical significance of PD-1 and PD-L1 expression in gastric and esophageal adenocarcinomas, particularly in non-Asian patients, is still unclear. Three tissue microarrays including 190 clinically annotated esophageal (n = 31) and gastric (n = 159) adenocarcinomas and 58 paired mucosa specimens, were stained with PD-1, PD-L1, and CD8-specific reagents in indirect immunohistochemistry assays. PD-L1 expression was detectable in 23.2% of cancer specimens. High PD-1 expression was detectable in 37.3% of cases and high CD8+ infiltration in 76%. PD-L1 and high PD1 expression significantly correlated with each other (r_s = 0.404, P < 0.0001) and both significantly correlated with CD8+ infiltration (r_s = 0.435, P = 0.0003, and r_s = 0.444; P = 0.0004, respectively). CD8+ lymphocyte infiltration correlated with improved survival in univariate (P = 0.009), but not multivariate analysis. Most interestingly, multivariate analysis and Kaplan-Meier curves indicate that combined low PD-1/PD-L1 expression and low CD8+ lymphocyte infiltration significantly correlate with poor prognosis. Our data document the clinical significance of a microenvironmental signature including PD-1/PD-L1 expression and CD8+ lymphocyte infiltration in gastric and esophageal adenocarcinomas and contribute to identify a patients' subset requiring more aggressive peri-operative treatments.

Recent Developments of Systemic Chemotherapy for Gastric Cancer

Gastric cancer (GC) is a molecularly heterogeneous disease. Its molecular background, epidemiology, and standard of care are quite different between Eastern and Western countries. Many efforts have been made in developing more effective surgeries and adjuvant chemotherapies for resectable GC in each region. Recently, an intensive combination of cytotoxic agents has been established as a new standard of adjuvant treatment. Meanwhile, palliative chemotherapy is a uniform standard treatment for unresectable GC worldwide. Recently, one of the most remarkable advances in therapy for unresectable GC has been the approval of immune checkpoint inhibitors (ICIs). The use of ICIs as frontline treatment is currently being investigated. In addition, novel combinations of ICIs and targeted drugs are being evaluated in clinical trials. Despite these advances, the complex biology of GC has resulted in the failure of targeted therapies, with the exceptions of HER2-targeted trastuzumab and VEGFR2-targeted ramucirumab. GC harbors many redundant oncogenic pathways, and small subsets of tumors are driven by different specific pathways. Therefore, a combination strategy simultaneously inhibiting several pathways and/or stricter patient selection for better response to targeted drugs are needed to improve clinical outcomes in this field.

Safety and Tolerability of Bintrafusp Alfa, a Bifunctional Fusion Protein Targeting TGFβ and PD-L1, in Asian Patients with Pretreated Recurrent or Refractory Gastric Cancer

PURPOSE

Patients with advanced gastric/gastroesophageal junction cancer (GC/GEJC) have limited treatment options after first-line therapy. Bintrafusp alfa is a first-in-class bifunctional fusion protein composed of the extracellular domain of the TGFβRII receptor (a TGFβ "trap") fused to a human IgG1 antibody against programmed death ligand 1 (PD-L1), potentially offering a new treatment approach for these patients. We report results for bintrafusp alfa in GC/GEJC.

PATIENTS AND METHODS

Asian patients with recurrent GC/GEJC for whom standard therapy does not exist or for whom standard therapy has failed enrolled in this expansion cohort of an ongoing phase I trial and received bintrafusp alfa 1,200 mg once every 2 weeks until disease progression, unacceptable toxicity, or withdrawal. The primary objective was to assess safety/tolerability.

RESULTS

By July 23, 2018, 31 heavily pretreated patients received bintrafusp alfa for a median of 10.1 weeks; 3 patients remained on treatment. Six patients (19%) experienced grade 3 treatment-related adverse events (AE); no grade 4 events occurred. One on-treatment death occurred (sudden death); rupture of a preexisting thoracic aortic aneurysm was the suspected cause. Ten patients (32%) had immune-related AEs. The confirmed objective response rate per independent review committee was 16%; disease control rate was 26%. Median duration of response was 8.7 months (range, 2.4-12.4+). Responses occurred irrespective of PD-L1 expression or microsatellite instability status and appeared to correlate with high tumor TGFB1 levels.

CONCLUSIONS

In this first evaluation in Asian patients with heavily pretreated advanced GC/GEJC, bintrafusp alfa demonstrated a manageable safety profile and clinical activity.

Intratumoral Immune Response to Gastric Cancer Varies by Molecular and Histologic Subtype

Immune checkpoint inhibition is effective in a subset of patients with advanced gastric cancer. Genomic profiling has revealed the heterogeneity of gastric adenocarcinomas, but the immune microenvironment and predictors of immunotherapy response remain poorly understood. We aimed to better characterize the underlying immune response to gastric cancer. Retrospective review of a prospectively maintained institutional database was performed to identify patients who underwent curative intent resection of gastric adenocarcinoma from 2006 to 2016. Tumors were classified according to modified TCGA subtype: Epstein-Barr virus (EBV)-associated, microsatellite instability (MSI)-high, intestinal as a surrogate for chromosomal instability, diffuse as a surrogate for genomically stable. Tumor-infiltrating leukocytes were measured using immunohistochemistry. Forty-three patients were identified: 6 EBV, 11 MSI, 14 intestinal, 12 diffuse. The most prevalent tumor-infiltrating leukocytes were CD8 T lymphocytes and CD68 macrophages, comprising 15% and 13% of all tumor cells. EBV and MSI tumors were the most infiltrated, harboring 30% to 50% T cells and 20% macrophages. Intestinal tumors contained fewer T cells but disproportionately more macrophages. Diffuse tumors were the least infiltrated. Programmed cell death protein 1 was most frequently expressed in intestinal tumors, whereas 70% of EBV and MSI tumors expressed programmed death-ligand 1. We herein demonstrate a heterogenous immune response to gastric cancer, which varies by tumor subtype and has implications for future immunotherapy trials. Checkpoint inhibition is unlikely to be effective as single-agent therapy against intestinal and diffuse tumors lacking prominent T-cell infiltration or substantial programmed death-ligand 1 expression.

Cost-Effectiveness Analysis of Biomarker-Guided Treatment for Metastatic Gastric Cancer in the Second-Line Setting

BACKGROUND

The 5-year survival rate of patients with metastatic gastric cancer (GC) is only 5%. However, trials have demonstrated promising antitumor activity for targeted therapies/immunotherapies among chemorefractory metastatic GC patients. Pembrolizumab has shown particular efficacy among patients with programmed death ligand-1 (PD-L1) expression and high microsatellite instability (MSI-H). The aim of this study was to assess the effectiveness and cost-effectiveness of biomarker-guided second-line GC treatment.

METHODS

We constructed a Markov decision-analytic model using clinical trial data. Our model compared pembrolizumab monotherapy and ramucirumab/paclitaxel combination therapy for all patients and pembrolizumab for patients based on MSI status or PD-L1 expression. Paclitaxel monotherapy and best supportive care for all patients were additional comparators. Costs of drugs, treatment administration, follow-up, and management of adverse events were estimated from a US payer perspective. The primary outcomes were quality-adjusted life years (QALYs) and incremental cost-effectiveness ratios (ICERs) with a willingness-to-pay threshold of $100,000/QALY over 60 months. Secondary outcomes were unadjusted life years (survival) and costs. Deterministic and probabilistic sensitivity analyses were performed to evaluate model uncertainty.

RESULTS

The most effective strategy was pembrolizumab for MSI-H patients and ramucirumab/paclitaxel for all other patients, adding 3.8 months or 2.0 quality-adjusted months compared to paclitaxel. However, this strategy resulted in a prohibitively high ICER of $1,074,620/QALY. The only cost-effective strategy was paclitaxel monotherapy for all patients, with an ICER of $53,705/QALY.

CONCLUSION

Biomarker-based treatments with targeted therapies/immunotherapies for second-line metastatic GC patients substantially improve unadjusted and quality-adjusted survival but are not cost-effective at current drug prices.

High PD-L1 expression in gastric cancer (GC) patients and correlation with molecular features

BACKGROUND

The programmed death receptor ligand 1 (PD-L1) immunohistochemistry (IHC) 22C3 pharmDx assay is a widely used selection method for pembrolizumab treatment in gastric cancer (GC) patients, especially in the U.S. The present study investigated the relationship between PD-L1 expression and the clinical features, molecular markers, and molecular subtypes of GC.

METHODS

PD-L1 expression was assessed based on combined positive score (CPS) using PD-L1 IHC 22C3 pharmDx in the Asian Cancer Research Group (ACRG) GC cohort (N = 300), which has been previously genomically profiled. PD-L1 positivity was defined as PD-L1 CPS ≥ 1. The association between PD-L1 expression and clinical features, tumor burden, and molecular subtypes (ACRG and The Cancer Genome Atlas [TCGA]) was analyzed.

RESULTS

Of the 300 tumors, 178 (59.3 %) had PD-L1 CPS ≥ 1 and 122 (40.7 %) had PD-L1 CPS < 1. PD-L1 CPS ≥ 1 was significantly associated with stage I tumor (P = 0.022), high microsatellite instability (MSI-H) (P < 0.001), Epstein-Barr virus (EBV) positivity (P = 0.008), and positive Helicobacter pylori status (P = 0.001). PD-L1 CPS ≥ 1 was observed in 96/193 (49.7 %) EBV-negative/microsatellite stable (MSS) tumors. In gene expression profiling, PD-L1 CPS was highly correlated with mutational load (P < 0.001) as well as EBV (P < 0.001) and MSI subtypes (P < 0.001); 27/300 (9%) GC patients had a very high PD-L1 (≥ 20) score (MSI-H, n = 10; EBV, n = 6; and non-EBV/MSS, n = 11). OS was longer in patients with PD-L1 CPS ≥ 1 tumors than in those with PD-L1 CPS < 1 tumors (median OS not reached vs. 40 months; P = 0.008; log-rank test).

CONCLUSIONS

PD-L1 is expressed in 59.3 % of GC patients and is associated with MSI and EBV positivity. These results provide a basis for identifying GC patients who may benefit from anti-PD-1/PD-L1 therapy.

Prognostic impacts of the combined positive score and the tumor proportion score for programmed death ligand-1 expression by double immunohistochemical staining in patients with advanced gastric cancer

BACKGROUND

The tumor proportion score (TPS) and combined positive score (CPS) have been developed to assess programmed death ligand 1 (PD-L1) expression in gastric cancer (GC). This study aimed to elucidate the role of TPS and CPS as prognostic biomarkers.

METHODS

A total of 191 patients with GC who received curative gastrectomy were retrospectively enrolled. Double immunohistochemistry of PD-L1 and ionized calcium binding adaptor molecule 1 was performed to clearly distinguish PD-L1 expression between tumor cells and macrophages. Survival analysis for PD-L1 expression by TPS and CPS was performed.

RESULTS

PD-L1 positivity was detected in 39 patients (20.4%) by TPS and in 137 patients (71.7%) by CPS. Patients with PD-L1 positivity by CPS experienced significantly shorter overall survival (OS) (P < 0.01) and relapse-free survival (RFS) (P = 0.01) than the other patients. In contrast, patients with either PD-L1 status by the TPS showed similar OS and RFS times. Multivariate Cox regression analysis for OS and RFS demonstrated that PD-L1 positivity by CPS was a significant independent factor for poor OS (hazard ratio [HR] 2.27, 95% confidence interval [CI] 1.27-4.37, P < 0.01) and RFS (HR 1.81, 95% CI 1.07-3.22, P = 0.03).

CONCLUSIONS

CPS was shown to be a more useful assessment method of determining PD-L1 expression than TPS as a prognostic biomarker. This suggests that the total number of PD-L1-expressing cells, including tumor and immune cells, is a more sensitive prognostic biomarker than the number of PD-L1-expressing tumor cells in GC.

Exploratory subgroup analysis of patients with prior trastuzumab use in the ATTRACTION-2 trial: a randomized phase III clinical trial investigating the efficacy and safety of nivolumab in patients with advanced gastric/gastroesophageal junction cancer

BACKGROUND

Data on immune checkpoint inhibitor efficacy in patients with human epidermal growth factor receptor 2-positive (HER2+) advanced gastric/gastroesophageal junction (G/GEJ) cancer are lacking. Because HER2 status was not captured in the ATTRACTION-2 trial, we used patients with prior trastuzumab use (Tmab+) as surrogate for HER2 expression status to evaluate the efficacy and safety of nivolumab as third- or later-line therapy in these patients.

METHODS

In ATTRACTION-2, a randomized, double-blind, placebo-controlled, phase 3 multicenter trial, patients were randomized (2:1) to receive nivolumab (3 mg/kg) or placebo every 2 weeks until disease progression or toxicity requiring study discontinuation. Overall survival (OS), progression-free survival (PFS), objective response rate (ORR), and safety were assessed.

RESULTS

Of 493 enrolled patients, 81 (nivolumab, n = 59; placebo, n = 22) were Tmab+ and 412 (nivolumab, n = 271; placebo, n = 141) were Tmab-. In both groups, patients receiving nivolumab showed a longer median OS vs placebo (Tmab+, 8.3 [95% confidence interval, 5.3-12.9] vs 3.1 [1.9-5.3] months, hazard ratio, 0.38 [0.22-0.66]; P = 0.0006; Tmab-, 4.8 [4.1-6.0] vs 4.2 [3.6-4.9] months, 0.71 [0.57-0.88]; P = 0.0022). PFS was longer in both groups receiving nivolumab vs placebo (Tmab+, 1.6 [1.5-4.0] vs 1.5 [1.3-2.9] months, 0.49 [0.29-0.85]; P = 0.0111; Tmab-, 1.6 [1.5-2.4] vs 1.5 [1.5-1.5] months, 0.64 [0.51-0.80]; P = 0.0001).

CONCLUSIONS

Nivolumab was efficacious and safe as third- or later-line therapy regardless of prior trastuzumab use in patients with advanced G/GEJ cancer.

Therapy Resistance in Neoadjuvantly Treated Gastric Cancer and Cancer of the Gastroesophageal Junction is Associated with an Increased Expression of Immune Checkpoint Inhibitors-Comparison Against a Therapy Naïve Cohort

With recent studies uncovering the complex landscape of immune checkpoint regulators in gastric cancer (GC), we aimed to characterize the expression of the checkpoint proteins V-domain Ig suppressor of T-cell activation (VISTA), programmed cell death 1 ligand 1 (PD-L1), and programmed cell death protein-1 (PD-1) in a cohort of GCs following platinum-based neoadjuvant chemotherapy. A total of 141 GC samples, 93 lymph node metastases, and 15 distant metastases were assessed using immunohistochemistry. Staining results were correlated with clinicopathological patient characteristics, genetic alterations, and survival. The expression of VISTA was detected in tumor cells of 38 (30.9%) GCs and immune cells of 139 (98.6%) GCs. The expression of PD-L1 was detected in tumor cells of 27 (22.7%) GCs and immune cells of 134 (96.4%) GCs. The expression of PD-1 was only observed in lymphocyte aggregates/intratumoral lymphoid follicles of 123 (87.2%) GCs. VISTA and PD-L1 correlated in their expression and were associated with poor tumor regression. Compared with an ancient cohort of therapy naïve GCs, we observed a major increase in overall immune cell density accompanied by an over proportional increase in PD-1 and VISTA-positive immune cells. The frequency of VISTA expression in tumor cells was also found to be substantially increased. To the contrary, expression of PD-L1 was decreased in immune cells and tumor cells of neoadjuvantly treated GCs. As a result, a subset of GCs using a single (only VISTA or PD-L1) or combined (VISTA and PD-L1) immune evasion mechanisms might benefit from an anti-PD-L1/anti-VISTA–targeted therapy.

Expression of LGR5, FZD7, TROY, and MIST1 in Perioperatively Treated Gastric Carcinomas and Correlation with Therapy Response

The cancer stem cell model is considered as a putative cause of resistance to chemotherapy and disease recurrence in malignant tumors. In this study, we tested the hypothesis that the response to neoadjuvant/perioperative chemotherapy correlates with the expression of four different putative cancer stem cell markers of gastric cancer (GC), i.e., LGR5, FZD7, TROY, and MIST1. The expression of LGR5, FZD7, TROY, and MIST1 was assessed by immunohistochemistry in 119 perioperatively treated GCs including pretherapeutic biopsies, resected primary GCs, and corresponding nodal and distant metastases. All four markers were detected in our cohort with variable prevalence and histoanatomical distributions. Few tumor cells expressed TROY. LGR5, FZD7, and MIST1 were coexpressed in 41.2% and completely absent in 6.2%. The prevalence of LGR5- and FZD7-positive GCs was higher and of TROY-positive GCs lower in perioperatively treated GCs compared with treatment-naïve tumors. LGR5, FZD7, and MIST1 in the primary tumors correlated significantly with their expression in the corresponding lymph node metastasis. An increased expression of LGR5 in primary GC correlated significantly with tumor regression. The expression of MIST1 in lymph node metastases correlated significantly with the number of lymph node metastases as well as overall and tumor-specific survival. FZD7 did not correlate with any clinicopathological patient characteristic. Our study on clinical patient samples shows that GCs may coexpress independently different stem cell markers; that neoadjuvant/perioperative treatment of GC significantly impacts on the expression of stem cell markers, which cannot be predicted by the analysis of pretherapeutic biopsies; and that their expression and tumor biological effect are heterogeneous and have to be viewed as a function of histoanatomical distribution.

Gastroesophageal cancer: Navigating the immune and genetic terrain to improve clinical outcomes

Recent advances in our understanding of the molecular biology of gastric and oesophageal cancers have shown that gastroesophageal adenocarcinoma should be considered as one disease spectrum. Clinical management of these cancers is challenging, with poor outcomes in both early and late disease settings. Certain molecular subsets of gastroesophageal adenocarcinoma demonstrate features that suggest immunotherapy could be an effective treatment. Immunogenetic markers, including mismatch repair deficiency, PD-L1 status and tumour infiltrating lymphocytes influence overall prognosis. They may also determine the response to adjuvant and neoadjuvant conventional chemotherapy. Initial results from immunotherapy trials for gastroesophageal cancer have however been mixed, with poor overall responses in the first- and second-line settings. This review aims to discuss how better understanding of these immune and genetic interactions may lead to better selection of patients for conventional and immune based therapies, and therefore improve patient outcomes. We also discuss the challenges in implementing this new understanding in routine practice, and the current limitations of immune based treatments for gastroesophageal cancer.

Overexpressed ITGA2 promotes malignant tumor aggression by up-regulating PD-L1 expression through the activation of the STAT3 signaling pathway

Background

Recent studies have reported that Integrin alpha 2 (ITGA2) plays an essential role in tumor cell proliferation, invasion, metastasis, and angiogenesis. An abnormally expressed ITGA2 correlates with unfavorable prognoses in multiple types of cancer. However, the specific mechanism of how ITGA2 contributes to tumorigenesis remains unclear.

Methods

The GEPIA web tool was used to find the clinical relevance of ITGA2 in cancer, and this significance was verified using Western blotting analysis of paired patient tissues and immunohistochemistry of the pancreatic cancer tissue. Functional assays, such as the MTS assay, colony formation assay, and transwell assay, were used to determine the biological role of ITGA2 in human cancer. The relationship between ITGA2 and programmed death-ligand 1 (PD-L1) was examined using Western blot analysis, RT-qPCR assay, and immunohistochemistry. The protein-protein interaction between ITGA2 and STAT3 was detected via co-immunoprecipitation.

Results

Our study showed that ITGA2 was markedly overexpressed in several malignant tumor cells and clinical tissues. Blocking ITGA2 inhibited the proliferation and invasion ability of cancer cells significantly, whereas overexpressed ITGA2 increased the degree of those processes considerably. Additionally, the RNA-seq assay indicated that ITGA2 transcriptionally regulated the expression of PD-L1 in pancreatic cancer. We also demonstrated that ITGA2 interacted with STAT3 and up-regulated the phosphorylation of STAT3; this interaction might involve the mechanism of ITGA2 inducing PD-L1 expression in cancer cells. Our results suggest that ITGA2 plays a critical role in cancer cell progression and the regulation of PD-L1 by activating the STAT3 pathway.

Conclusions

We identified a novel mechanism by which ITGA2 plays a critical role in modulating cancer immune response by transcriptionally increasing the expression of PD-L1 in cancer cells. Thus, targeting ITGA2 is an effective method to enhance the efficacy of checkpoint immunotherapy against cancer.

Sexual dimorphism in gastric cancer: tumor-associated neutrophils predict patient outcome only for women

PURPOSE

Tumor-associated neutrophils (TANs) are part of the tumor immune microenvironment (TIME) and may contribute to gastric cancer (GC) biology. We hypothesized that TAN are enriched in the TIME, show sex-specific differences, and correlate with patient outcome.

METHODS

We analyzed the distribution and putative tumor biological significance of TANs in a well-characterized, therapy-naïve, European GC cohort using immunohistochemical staining of myeloperoxidase (MPO), and digital image analysis using Definiens Tissue Studio^®.

RESULTS

Different tumor compartments were examined, and TAN densities were correlated with various clinicopathological patient characteristics. TAN density showed a large interindividual variability ranging from 0 to 6711.0 TANs/mm². Intratumoral distribution patterns were inhomogeneous (tumor surface vs. tumor center vs. invasion front) and correlated significantly with Laurén phenotype, tumor grade, and microsatellite status in the tumor center and invasion front. In the multivariate analysis, TAN density in the invasion front was an independent predictor of tumor-specific survival only for women (HR = 2.77, p   < 0.001). In men, no correlation was found between TAN density and survival.

CONCLUSION

With regard to TANs, our study independently validates sexual dimorphism in GC biology.

Clinical Implications of Microsatellite Instability in Early Gastric Cancer

Purpose

We aimed to evaluate the clinical characteristics of microsatellite instability in early gastric cancer.

Materials and Methods

The microsatellite instability status of resected early gastric tumors was evaluated using two mononucleotide repeat markers (BAT25 and BAT26) and three dinucleotide repeat markers (D5S346, D2S123, and D17S250). Tumors with instability in two or more markers were defined as microsatellite instability-high (MSI-H) and others were classified as microsatellite stable (MSS).

Results

Overall, 1,156 tumors were included in the analysis, with 85 (7.4%) classified as MSI-H compared with MSS tumors. For MSI-H tumors, there was a significant correlation with the female sex, older age, tumor location in the lower gastric body, intestinal histology, lymphovascular invasion (LVI), and submucosal invasion (P<0.05). There was also a trend toward an association with lymph node (LN) metastasis (P=0.056). In mucosal gastric cancer, there was no significant difference in MSI status in tumors with LN metastasis or tumors with LVI. In submucosal gastric cancer, LVI was more frequently observed in MSI-H than in MSS tumors (38.9% vs. 25.0%, P=0.027), but there was no difference in the presence of LN metastases. The prognosis of MSI-H tumors was similar to that of MSS tumors (log-rank test, P=0.797, the hazard ratio for MSI-H was adjusted by age, sex, pT stage, and the number of metastatic LNs, 0.932; 95% confidence interval, 0.423–2.054; P=0.861).

Conclusions

MSI status was not useful in predicting prognosis in early gastric cancer. However, the frequent presence of LVI in early MSI-H gastric cancer may help guide the appropriate treatment for patients, such as endoscopic treatment or limited LN surgical dissection.

Intratumoral heterogeneity and loss of ARID1A expression in gastric cancer correlates with increased PD-L1 expression in Western patients

Recent whole-genome sequencing showed frequent mutations of ARID1A in gastric cancer (GC). In this study of a large independent Central European cohort, we evaluated the expression of ARID1A in whole tissue sections (WTS) of GC testing the following hypotheses: ARID1A shows intratumoral heterogeneity, and ARID1A expression and/or heterogeneity correlates with clinicopathological patient characteristics. ARID1A expression was studied by immunohistochemistry in 450 primary GCs and 143 corresponding lymph node metastases. The expression pattern was correlated with clinicopathological characteristics and patient survival. ARID1A genotype and CpG methylation status were additionally analyzed in 7 GCs with a heterogeneous "black-and-white" expression pattern. ARID1A was expressed heterogeneously in 23 (5.1%) GCs, depicting a black-and-white pattern of negative and positive tumor areas. Complete loss of expression was found in 43 (9.6%) GCs. ARID1A status correlated significantly with tumor type according to Laurén, Epstein-Barr virus status, microsatellite instability, PD-L1 status, and nodal spread. There was no correlation with patient survival. In 4 cases with heterogeneous ARID1A expression, frame shift variants were detected. Summing up, heterogeneous or complete loss of ARID1A expression occurred in 14.7% of GCs and correlated with PD-L1 status, indicating potential for future combined anti-PD-L1/ARID1A therapy. In a subgroup of cases, ARID1A loss was heterogeneous, which suggests that ARID1A mutations might be a later event in gastric carcinogenesis.

Differences in immune contextures among different molecular subtypes of gastric cancer and their prognostic impact

BACKGROUND

Gastric cancers have been recently classified in accordance with their molecular characteristics, thus demonstrating the complex nature of cancers and an association with the immune contexture within the tumor microenvironment. This study aimed to investigate the correlation between the molecular subtype and immune contexture of gastric cancers.

METHODS

The immune contexture, including the type, density, and location of tumor-infiltrating lymphocytes (TILs), of gastric cancer patients was examined and immune subtypes were classified based on it. In particular, PD-L1 expression on tumor cells and TILs and Foxp3⁺ TILs was assessed in accordance with molecular subtypes.

RESULTS

High levels of visual TIL estimates and Foxp3⁺ TILs were markedly associated with increased overall survival (P = 0.001, P < 0.001, separately). Immune subtypes were associated with tumor size, gross type, depth of invasion, lymph node metastatic status, lymphovascular invasion, perineural invasion, and microsatellite instability status. EBV-positive (C1) and MSI (C2) gastric cancers, considered subtypes with better prognosis, were significantly associated with high TIL levels (P < 0.05). In contrast, epithelial-mesenchymal transition (EMT, C3) gastric cancers with poor overall survival displayed low levels of Foxp3⁺ TILs. Type II tumors (low level of TILs/low PD-L1 expression) displayed a significant correlation with poor overall survival (P = 0.004) and accounted for the highest proportion in the aberrant p53-expressing (C4) gastric cancers.

CONCLUSION

The molecular subtype of gastric cancers is correlated with the immune subtype, including immune contexture and PD-L1 expression, within the tumor microenvironment.

PD-1 and PD-L1 inhibitors in oesophago-gastric cancers

Oesophago-gastric cancers (OGCs) are aggressive tumours. While better peri-operative strategies, increased number of cytotoxic agents and availability of targeted therapies have improved survival, there remains an unmet need for novel treatment approaches. Immune checkpoint inhibitors (ICIs) have marked a new era in cancer management with unprecedented results in several malignancies. Although OGC lagged behind other solid tumours, evidence has increasingly accumulated supporting the contention that modulation of the anti-cancer host immune response may be beneficial for at least some patients. Many trials have been completed in Eastern and Western countries, some of these leading to the approval of ICIs in the refractory setting, and favorable opinion from regulatory agencies is expected also in treatment-naïve, advanced OGC. Furthermore, studies are evaluating ICIs in the early stage setting and exploring the potential of combination treatments. In this article we discuss the biological bases underlying the successful development of ICIs in OGC and review the available data on PD-1 and PD-L1 monoclonal antibodies in this disease. Also, we present ongoing clinical trials of these ICIs that could shape the future treatment landscape of OGC.

Targeted therapies in metastatic gastric cancer: Current knowledge and future perspectives

Gastric cancer (GC) represents a leading cause of cancer related morbidity and mortality worldwide accounting for more than 1 million of newly diagnosed cases and thousands of deaths every year. In the last decade, the development of targeted therapies and the optimization of already available chemotherapeutic drugs has expanded the available treatment options for advanced GC and granted better survival expectations to the patients. At the same time, global efforts have been undertaken to investigate in detail the genomic and epigenomic heterogeneity of this disease, resulting in the identification of new specific and sensitive predictive and prognostic biomarkers and in innovative molecular classifications based on gene expression profiling. Nonetheless, several randomized studies aimed at exploring new innovative agents, such as immune checkpoint inhibitors, failed to demonstrate clinically meaningful survival advantages. Therefore, it is essential to further improve the molecular characterization of GC subgroups in order to provide researchers and medical oncologists with new tools for patients’ selection and stratification in future clinical development programs and subsequent trials. The aim of the present manuscript is to provide a global overview of the recent molecular classifications from The Cancer Genome Atlas and the Asian Cancer Research Group and to present key promising developments in the field of immunotherapy and targeted therapies in metastatic GC.

CMTM6, the newly identified PD-L1 regulator, correlates with PD-L1 expression in lung cancers

Modulation of Immune check point regulators, especially the PD-1/PD-L1 axis, plays a critical role in successful management of a small proportion of lung cancer patients, but not so effective in the rest of lung cancer patients. A better understanding of immunotherapy non-responsive or resistant patients therefore warranted for future development of novel therapeutics. The newly identified regulator CMTM6 (CKLF-like MARVEL transmembrane domain containing 6) has been reported to serves as the stabilizer of PD-L1 and enhances the inhibitory effect of PD-L1 on immune system in both cell line and animal models, but its clinical relevance associated with PD-L1 is unknown and the current study is designed to address this question. The study using immunohistochemistry demonstrated that CMTM6 positivity from 15 out of 19 types of cancers with our in-house tissue microarray, and PD-L1 expression is always found only in CMTM6 positive cancers. CMTM6 and PD-L1 expression were analyzed in 81 lung cancer patient sample, and we observed that CMTM6 expression correlated with cancer histotypes and inversely correlated with cancer metastases, but not with patients’ age and gender. No PD-L1 expression was observed in negative CMTM6 samples. Higher expression PD-L1 is also associated with higher CMTM6 expression. In summary, CMTM6 expression is associated with PD-L1 expression, as well as lung cancer histotypes and metastasis. The results thus for the first time confirmed earlier reports on CMTM6/PD-L1 connection, from a clinical aspect of analysis.

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Confirmed the CMTM6 expression in different cancer tissues include lung cancers.

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Addressed the correlation of CMTM6 and PD-L1 expression in clinical samples.

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Demonstrated the correlation between CMTM6 expression and lung cancer histotypes.

Gastric Cancer in the Era of Immune Checkpoint Blockade

Gastric cancer (GC) is one of the most important malignancies worldwide because of its high incidence and mortality. The very low survival rates are mainly related to late diagnosis and limited treatment options. GC is the final clinical outcome of a stepwise process that starts with a chronic and sustained inflammatory reaction mounted in response to Helicobacter pylori infection. The bacterium modulates innate and adaptive immunity presumably as part of the strategies to survive, which favors the creation of an immunosuppressive microenvironment that ultimately facilitates GC progression. T-cell exhaustion, which is characterized by elevated expression of immune checkpoint (IC) proteins, is one of the most salient manifestations of immunosuppressive microenvironments. It has been consistently demonstrated that the tumor-immune microenvironment(TIME)‐exhausted phenotype can be reverted by blocking ICs with monoclonal antibodies. Although these therapies are associated with long-lasting response rates, only a subset of patients derive clinical benefit, which varies according to tumor site. The search for biomarkers to predict the response to IC inhibition is a matter of intense investigation as this may contribute to maximize disease control, reduce side effects, and minimize cost. The approval of pembrolizumab for its use in GC has rocketed immuno-oncology research in this cancer type. In this review, we summarize the current knowledge centered around the immune contexture and recent findings in connection with IC inhibition in GC.

Clinicopathologic Characteristics of Epstein-Barr Virus-Associated Gastric Cancer Over the Past Decade in Japan

: Epstein-Barr virus (EBV) is a ubiquitous human herpes virus, but related with several types of malignancies. Among EBV-related malignancies, EBV-associated gastric carcinoma (EBVaGC) has the largest patient's number. We screened for EBV infection in 1067 GC lesions of 1132 patients who underwent surgical resection from 2007 to 2017 in Japan and examined clinicopathological features of EBVaGC. EBV infection was detected by in situ hybridization with EBV-encoded small RNA 1(EBER-1 ISH). EBV was infected in 80 GC lesions (7.1%). Mean age was significantly lower in patients with EBVaGC than with EBV-negative GC. EBVaGC was more frequent in men than in women. EBVaGC was found twice as frequent in the upper or middle stomach as in the lower stomach. Early EBVaGC was more frequent, and submucosally invaded cases were dominant. The presence of lymphatic vessel invasion was less in EBVaGC, but frequency of lymph node metastasis was similar. Carcinoma with lymphoid stroma (CLS) was found in 3.8% (43/1132) of all lesions with 60.5% of EBV positivity. The synchronous or metachronous multiple GC was frequent in EBVaGC. We clarified clinicopathologic characteristics of EBVaGC over the past decade in Japan. EBV infection should be examined in gastric cancer cases showing these characteristics.

Tumor microenvironment immune types in gastric cancer are associated with mismatch repair however, not HER2 status

The treatment of patients with human epidermal growth factor receptor 2 (HER2)-negative gastric cancer is a major challenge. Immunotherapy using immune checkpoint inhibitors is a rapidly growing field. In a number of malignancy types it has been demonstrated that patients with mismatch repair deficiency efficiently respond to programmed death-ligand 1 (PD-L1) blockade therapy. Recent studies have evaluated tumor microenvironment immune types to predict which patients may clinically benefit from immunotherapy. The present study aimed to evaluate the immunohistochemical expression of PD-L1 in 70 gastric cancer tissue samples. Potential associations between PD-L1 expression and mismatch repair deficiency, HER2 and Epstein Barr virus (EBV) status were then investigated in the context of the tumor microenvironment. A positive association was identified for PD-L1 expression with mismatch repair deficiency and EBV status; however, no association was revealed with HER2 status. Immunohistochemistry was then used to classify the microenvironment immune types. This demonstrated that the majority of the gastric cancer samples (73%) belonged to the tumor microenvironment immune type II [PD-L1-/cluster of differentiation 8 (CD8)+ low], which involves an immune ignorant state and has a low sensitivity to immunotherapy. However, 7% of the gastric cancer cases were identified to belong to the tumor microenvironment immune type I (PD-L1+/CD8+ high), which exhibits adaptive immune escape responses and a high chance of reversion with immune checkpoint blockade therapy. In conclusion, the present study emphasized the importance of evaluating tumor microenvironment immune types, mismatch repair deficiency status and EBV status, rather than PD-L1 expression alone, when evaluating the eligibility of a patient for immunotherapy with anti-programmed cell death protein-1/PD-L1 antibodies.

Detecting genetic hypermutability of gastrointestinal tumor by using a forensic STR kit

Growing evidence suggests that somatic hypermutational status and programmed cell death-1 overexpression are potential predictive biomarkers indicating treatment benefits from immunotherapy using immune checkpoint inhibitors. However, biomarker-matched trials are still limited, and many of the genomic alterations remain difficult to target. To isolate the potential somatic hypermutational tumor from microsatellite instability low/microsatellite stability (MSI-L/MSS) cases, we employed two commercial kits to determine MSI and forensic short tandem repeat (STR) alternations in 250 gastrointestinal (GI) tumors. Three types of forensic STR alternations, namely, allelic loss, Aadd, and Anew, were identified. 62.4% (156/250) of the patients with GI exhibited STR alternation, including 100% (15/15) and 60% (141/235) of the microsatellite high instability and MSI-L/MSS cases, respectively. 30% (75/250) of the patients exhibited STR instability with more than 26.32% (26.32%-84.21%) STR alternation. The cutoff with 26.32% of the STR alternations covered all 15 MSI cases and suggested that it might be a potential threshold. Given the similar mechanism of the mutations of MSI and forensic STR, the widely used forensic identifier STR kit might provide potential usage for identifying hypermutational status in GI cancers.

Can PD-L1 expression evaluated by biopsy sample accurately reflect its expression in the whole tumour in gastric cancer?

Programmed death ligand 1 (PD-L1) expression as a predictive biomarker for programmed cell death 1 (PD-1) inhibitor efficacy in gastric cancer (GC) remains controversial. We hypothesised that the conflicting results may be due to the inaccurate assessment of PD-L1 expression using biopsy samples. A total of 191 patients with GC who received radical resection were enrolled. PD-L1 expressions in biopsy and paired resected samples by immunohistochemistry staining were compared according to the number of biopsies. The numbers of PD-L1-positive patients determined by biopsy and resected samples were 89 (46.6%) and 135 (70.1%), respectively. The accordance rate was 64.4% (κ = 0.31). Single biopsy showed a lower accordance rate compared with multiple biopsies. Our study revealed that single biopsy cannot fully reflect PD-L1 expression in the whole tumour in GC. Multiple biopsies are recommended for accurate diagnosis of PD-L1 expression in GC.

Changes in Expression of Multiple Checkpoint Molecules and Infiltration of Tumor Immune Cells after Neoadjuvant Chemotherapy in Gastric Cancer

It remains unclear that how tumor immune micro-environment will change following neoadjuvant chemotherapy (NACT) in locally advanced gastric cancer (LAGC). In this study, we aimed to characterize the changes in tumor-infiltrating immune cells and checkpoint molecules following NACT and investigate the prognostic value of these changes in LAGC. Paired tumor samples (pre-NACT and post-NACT) of 60 patients were retrospectively identified and analyzed by multiplex immunohistochemistry with a panel including CD4, CD8, FOXP3, PD-1, PD-L1, and TIM3. Following NACT, the overall median expression levels of CD4, CD8, PD1, PD-L1 and TIM3 were significantly increased (P = 0.008 for PD-L1 and P < 0.001 for all the other markers), while the median FOXP3 expression level remained stable (P = 0.120). Individually, the majority of patients presented increased expression of the markers, while 8.5%, 11.9%, 16.9%, 25.4%, 22.0% and 42.2% of patients had decreased expression of CD4, CD8, PD-1, PD-L1, TIM3 and FOXP3, respectively. Changes in expression between baseline and post-NACT of TIM3, PD-1, and PD-L1 showed strongly positive pairwise correlations with each other (P < 0.001). Multivariate analysis demonstrated that high upregulation levels of CD8 (HR = 0.73, P = 0.028), PD-1 (HR = 0.76, P = 0.027), and PD-L1 (HR = 0.67, P = 0.038) following NACT were beneficial prognostic factors of OS. NACT increase the expression of multiple checkpoint molecules and infiltration of CD4+, CD8+ immune cells in LAGC with the levels of changes in checkpoint molecules positively related with each other. This may raise the possibility of applying immunotherapy with chemotherapy or even dual checkpoint inhibitors in LAGC.

Current and Future Aspects of Immunotherapy for Esophageal and Gastric Malignancies

Esophagogastric (EG) cancer has a poor prognosis despite the use of standard therapies, such as chemotherapy and biologic agents. Recently, immune checkpoint inhibitors (ICIs) have been introduced as treatments for EG cancer; nivolumab and pembrolizumab have been approved in the United States and Europe to treat advanced EG cancer. Other ICIs, such as avelumab, durvalumab, ipilimumab, and tremelimumab, have been evaluated in several trials, although their roles are still not established in clinical practice. In addition, preclinical evidence suggests that combining an ICI with a tumor-targeting antibody can result in greater antitumor effects in metastatic EG cancer. There are not yet validated predictive biomarkers to identify which patients will respond best to ICI treatment. PD-L1 expression may predict intensity of response, although PD-L1-negative patients can still respond to ICIs. Despite differences in PD-L1 expression between Asian and non-Asian populations, no geographic differences in rates of treatment-related or immune-mediated/infusion-related adverse events have been reported. Also, several trials are currently evaluating combinations of ICIs, standard chemotherapy, and biologic agents as well as novel biomarkers to improve treatments and outcomes. Our review will address the current use of and evidence for ICIs for advanced EG cancer treatment and future trends in this area for clinical practice.

EBV-associated gastric cancer evades T-cell immunity by PD-1/PD-L1 interactions

BACKGROUND

Epstein-Barr virus (EBV) is an oncogenic human herpesvirus involved in the development of around 10% of gastric cancers. The overexpression of PD-L1 is one of the features of EBV-associated gastric cancer (EBVaGC); however, the function of PD-L1 has not been studied in EBVaGC.

METHODS

We used three EBVaGC cell lines, SNU719 cells, NCC24 cells, and YCCEL1 cells, to evaluate the PD-L1 expression and function in EBVaGC. Jurkat T-lymphocytes expressing PD-1 were co-cultured with NCC24 and YCCEL1 cells and the cell cycles were analyzed. To study the regulatory mechanism for PD-L1 expression, the 3'UTR of PD-L1 was sequenced, and the effect of inhibitors of the IFN-γ signaling pathway was evaluated.

RESULTS

All of the EBVaGC cell lines expressed PD-L1, and its expression was further enhanced by stimulation with IFN-γ. In Jurkat T-cells co-cultured with IFN-γ-stimulated NCC24 and YCCEL1 cells, the number of cells in the G0/G1 phase was significantly increased. This G0/G1 arrest was partially released by administration of anti-PD-L1 antibody. We found SNPs in PD-L1 3'UTR nucleotide sequences that were located at seed regions for microRNAs. Treatment of EBVaGC cell lines with JAK2-inhibitor, PI3K-inhibitor, and mTOR inhibitor reduced the level of PD-L1 expression to the same level as cells without IFN-γ stimulation.

CONCLUSIONS

EBVaGC cells expressing high levels of PD-L1 suppress T-cell proliferation, and the IFN-γ signaling pathway is involved in the expression of PD-L1.

PD-1/PD-L1 antagonists in gastric cancer: Current studies and perspectives

Immune checkpoints release suppressive signals for T cells, which enable the tumors to escape from immune destruction and provide a new concept that uses the capabilities of the immune system as a therapeutic target for tumors. At present, programmed death receptor 1 (PD-1)/programmed death ligand-1 (PD-L1) has become the most promising therapeutic target. PD-1/PD-L1 blockades exhibit long-lasting antitumor efficacy and safety in patients with various cancers, such as melanoma and non-small-cell lung cancer. Moreover, PD-L1 is highly expressed in the peripheral blood and tumor specimens of patients with cancer, and the expression of PD-L1 is positively correlated with various pathological features and may serve as a predictor of poor prognosis or a diagnostic tool. Clinical trials have verified that PD-1/PD-L1 blockade therapy benefits patients with advanced gastric cancer or gastroesophageal junction cancer. Furthermore, there are many molecules involved in the regulation of PD-1/PD-L1 expression, and the modification of these molecules via drugs and combinations with PD-1/PD-L1 inhibitors may further improve the efficacy of immunotherapy for gastric cancer. In this review, the efficacy, safety, and possible combination treatment options of PD-1/PD-L1 in gastric cancer are reviewed in experimental and clinical settings.

PD-L1 expression combined with microsatellite instability/CD8+ tumor infiltrating lymphocytes as a useful prognostic biomarker in gastric cancer

While the importance of programmed death-ligand 1 (PD-L1), mutation burden caused by microsatellite instability (MSI), and CD8+ tumor infiltrating lymphocytes (TILs) has become evident, the significance of PD-L1 expression on prognosis still remains controversial. We evaluated the usefulness of combined markers of PD-L1 and MSI or CD8+ TILs as a prognostic biomarker in gastric cancer. A total of 283 patients with gastric cancer were reviewed retrospectively. PD-L1 expression on >5% tumor cells was defined as PD-L1-positive. PD-L1-positive rate was 15.5% (44/283). PD-L1 positivity was significantly correlated with invasive and advanced cancer and also significantly correlated with MSI, whereas no significance was observed with CD8+ TILs. Kaplan-Meier analysis showed that PD-L1 positivity significantly correlated with a poor prognosis (p = 0.0025). Multivariate analysis revealed that PD-L1 positivity was an independent poor prognostic factor (hazard ratio [HR]: 1.97, p = 0.0106) along with diffuse histological type and lymph node metastases. Combinations of PD-L1 and MSI (HR: 2.18) or CD8+ TILs (HR: 2.57) were stronger predictive factors for prognosis than PD-L1 alone. In conclusion, combined markers of PD-L1 and MSI or CD8+ TILs may be more useful prognostic biomarkers in gastric cancer, and better clarify the immune status of gastric cancer patients.

Expression of PD-L1 and PD-1 in Chemoradiotherapy-Naïve Esophageal and Gastric Adenocarcinoma: Relationship With Mismatch Repair Status and Survival

Background: The outlook for patients with esophageal and gastric (EG) cancer remains poor. Hence, there is a compelling need to identify novel treatment strategies and complementary biomarkers. Programmed death ligand 1 (PD-L1) and mismatch repair deficiency (dMMR) are putative biomarkers of response to immune-checkpoint blockade, but their prognostic value and interrelationship in EG cancer have been sparsely investigated.

Methods: Immunohistochemical expression of PD-L1 on tumour cells (TC) and tumour-infiltrating immune cells (TIC), and of PD-1 (programmed death receptor 1) on TIC was assessed using tissue microarrays with primary tumours and a subset of paired lymph node metastases from a consecutive, retrospective cohort of 174 patients with chemoradiotherapy-naïve EG adenocarcinoma. MMR proteins MLH1, PMS2, MSH2, and MSH6 were assessed by immunohistochemistry. The total number (intratumoural, tumour-adjacent, and stromal) of CD8⁺ T cells in each core was calculated by automated analysis.

Results: High PD-L1 expression on both TC and TIC, but not PD-1 expression, was significantly associated with dMMR. PD-L1 expression on TIC was significantly higher in lymph node metastases than in primary tumours. High expression of PD-L1 or PD-1 on TIC was significantly associated with a prolonged survival, the former independently of established prognostic factors. A significant stepwise positive association was found between CD8⁺ T cells and categories of PD-L1 expression on TIC.

Conclusion: PD-L1 expression on TIC is higher in lymph node metastases compared to primary tumours, correlates with dMMR, and is an independent factor of prolonged survival in patients with chemoradiotherapy-naïve EG adenocarcinoma. These findings suggest that PD-L1 expression on TIC may be a useful biomarker for identifying patients who may not need additional chemo- or chemoradiotherapy, and who may benefit from PD-1/PD-L1 immune-checkpoint blockade.

POLE Score: a comprehensive profiling of programmed death 1 ligand 1 expression in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) being characterized by a pronounced stromal compartment is commonly diagnosed at an advanced stage limiting curative treatment options. Although therapeutical targeting of immune checkpoint regulators like programmed death 1 ligand 1 (PD-L1) represent a promising approach that substantially improved survival of several highly aggressive malignancies, convincing indicators for response prediction are still lacking for PDAC which might be attributed to the insufficient characterization of PD-L1 status. Therefore, we investigated PD-L1 expression by immunohistochemistry in a well characterized cohort of 59 PDAC and 18 peritumoral tissues. Despite the histopathological homogeneity within our cohort, tumor tissues exhibited a great heterogeneity regarding PD-L1 expression. Considering distinct PD-L1 expression patterns, we established the novel POLE Score that incorporates overall PD-L1 expression (P), cellular Origin of PD-L1 (O), PD-L1 level in tumor-associated Lymph follicles (L) and Enumerated local PD-L1 distribution (E). We show that tumoral PD-L1 expression is higher compared to peritumoral areas. Furthermore, POLE Score parameters correlated with overall survival, tumor grade, Ki67 status, local proximity of tumor cells and particular stroma composition. For the first time, we demonstrate that PD-L1 is mostly expressed by stroma and rarely by tumor cells in PDAC. Moreover, our in situ analyses on serial tissue sections and in vitro data suggest that PD-L1 is prominently expressed by tumor-associated macrophages. In conclusion, POLE Score represents a comprehensive characterization of PD-L1 expression in tumor and stroma compartment and might provide the basis for improved patient stratification in future clinical trials on PD-1/PD-L1 targeting therapies in PDAC.

KEYNOTE-585: Phase III study of perioperative chemotherapy with or without pembrolizumab for gastric cancer

BACKGROUND

Surgical resection is the only curative treatment option for gastric cancer. Despite widespread adoption of multimodality perioperative treatment strategies, 5-year overall survival rates remain low. In patients with advanced gastric or gastroesophageal junction adenocarcinoma, pembrolizumab has demonstrated promising efficacy and manageable safety as monotherapy in previously treated patients and as first-line therapy in combination with cisplatin and 5-fluorouracil. Combining chemotherapy with pembrolizumab in the neoadjuvant/adjuvant setting may benefit patients with locally advanced, resectable disease.

AIM

To describe the design and rationale for the global, multicenter, randomized, double-blind, Phase III KEYNOTE-585 study to evaluate the efficacy and safety of pembrolizumab plus chemotherapy compared with placebo plus chemotherapy as neoadjuvant/adjuvant treatment for localized gastric or gastroesophageal junction adenocarcinoma. ClinicalTrials.gov : NCT03221426.

Avelumab (anti-PD-L1) as first-line switch-maintenance or second-line therapy in patients with advanced gastric or gastroesophageal junction cancer: phase 1b results from the JAVELIN Solid Tumor trial

Background

We evaluated the antitumor activity and safety of avelumab, a human anti–PD-L1 IgG1 antibody, as first-line switch-maintenance (1 L-mn) or second-line (2 L) treatment in patients with advanced gastric/gastroesophageal cancer (GC/GEJC) previously treated with chemotherapy.

Methods

In a phase 1b expansion cohort, patients without (1 L-mn) or with (2 L) disease progression following first-line chemotherapy for advanced GC/GEJC received avelumab 10 mg/kg intravenously every 2 weeks. Endpoints included best overall response, progression-free survival (PFS), overall survival (OS), and safety.

Results

Overall, 150 patients were enrolled (1 L-mn, n = 90; 2 L, n = 60) and median follow-up in the 1 L-mn and 2 L subgroups was 36.0 and 33.7 months, respectively. The confirmed objective response rate was 6.7% in both subgroups (95% CI, 2.5–13.9% and 1.8–16.2%, respectively), including complete responses in 2.2% of the 1 L-mn subgroup (n = 2). In the 1 L-mn and 2 L subgroups, median duration of response was 21.4 months (95% CI, 4.0–not estimable) and 3.5 months (95% CI, 2.8–8.3) and disease control rates were 56.7 and 28.3%, respectively. Median PFS in the 1 L-mn and 2 L subgroups was 2.8 months (95% CI, 2.3–4.1) and 1.4 months (95% CI, 1.3–1.5), with 6-month PFS rates of 23.0% (95% CI, 14.7–32.4%) and 7.9% (95% CI, 2.6–17.2%), and median OS was 11.1 months (95% CI, 8.9–13.7) and 6.6 months (95% CI, 5.4–9.4), respectively. In the 1 L-mn subgroup, median OS measured from start of 1 L chemotherapy was 18.7 months (95% CI, 15.4–20.6). Across both subgroups, 20.7% had an infusion-related reaction of any grade. Other common treatment-related adverse events (TRAEs) of any grade included fatigue (10.0%) and nausea (6.7%). Treatment-related serious adverse events occurred in 4.0% of patients. Overall, 8.7% had a grade ≥3 TRAE, including 1 treatment-related death.

Conclusion

Avelumab showed clinical activity and an acceptable safety profile in patients with GC/GEJC.

Trial registration

ClinicalTrials.govNCT01772004; registered 21 January 2013.

Electronic supplementary material

The online version of this article (10.1186/s40425-019-0508-1) contains supplementary material, which is available to authorized users.

Discordancy and changes in the pattern of programmed death ligand 1 expression before and after platinum-based chemotherapy in metastatic gastric cancer

BACKGROUND

Our goal was to evaluate changes in PD-L1 expression in primary tumours of metastatic gastric cancer before and after chemotherapy.

METHODS

We evaluated the PD-L1 expression of 72 patients with primary gastric cancer, before and after palliative first-line platinum-based chemotherapy, between January 2015 and March 2017. The PD-L1 ratio was defined as pre-chemotherapy PD-L1 expression divided by the post-chemotherapy PD-L1 expression.

RESULTS

In 30 patients with PD-L1 negative pre-chemotherapy, 12 (40%) were positive post-chemotherapy; among the 42 patients with PD-L1 positive pre-chemotherapy, 24 (57.1%) were negative post-chemotherapy. The degree of PD-L1 expression decreased from 58.3% before chemotherapy to 41.7% after chemotherapy (P = 0.046). Among patients with complete response/partial response (CR/PR), the degree of PD-L1 expression decreased (P = 0.002), as well as PD-L1 positivity with statistical significance (P = 0.013) after chemotherapy, but not among patients with stable disease/progressive disease (SD/PD). Higher disease control rates (CR/PR/SD) were observed in patients with an elevated PD-L1 ratio (P = 0.043). Patients with a high PD-L1 ratio (> 1) were found to be associated with a better progression-free survival (HR 0.34, 95% CI 0.17-0.67, P = 0.002).

CONCLUSIONS

PD-L1 expression can change during chemotherapy. Moreover, changes in patterns of PD-L1 expression might be associated with patient prognosis and response to chemotherapy.

Phase 1 trial of avelumab (anti-PD-L1) in Japanese patients with advanced solid tumors, including dose expansion in patients with gastric or gastroesophageal junction cancer: the JAVELIN Solid Tumor JPN trial

BACKGROUND

Avelumab is a human anti-PD-L1 IgG1 monoclonal antibody that has shown antitumor activity in several advanced cancers. We report results from JAVELIN Solid Tumor JPN, a phase 1 trial of avelumab in Japanese patients with advanced solid tumors with expansion in patients with advanced gastric cancer/gastroesophageal junction cancer.

METHODS

In the dose-escalation part, eligible patients had various previously treated metastatic or advanced solid tumors. In the dose-expansion part, patients had stage IV gastric cancer/gastroesophageal junction adenocarcinoma and disease progression after prior therapy that included a platinum and fluoropyrimidine agent. Patients received avelumab every 2 weeks intravenously at 3, 10, or 20 mg/kg during dose escalation and 10 mg/kg during dose expansion.

RESULTS

Among 17 patients who received avelumab in the dose-escalation part, no dose-limiting toxicities occurred, and the maximum tolerated dose was not reached. 40 patients were enrolled in the dose-expansion part, of whom 21 (52.5%) had received ≥ 3 prior lines of therapy for advanced disease. In these patients, the objective response rate was 10.0% (95% CI, 2.8-23.7%) and median overall survival was 9.1 months (95% CI, 7.2-11.2 months). Three of 40 patients (7.5%) had a grade 3 treatment-related adverse event (alanine aminotransferase increase, anemia, and hyponatremia), and no grade ≥ 4 treatment-related adverse events occurred. Five patients (12.5%) had an immune-related adverse event (all grade 1/2).

CONCLUSIONS

Avelumab showed acceptable safety in Japanese patients with advanced solid tumors and clinical activity in patients with advanced gastric cancer/gastroesophageal junction cancer and disease progression after chemotherapy.

Pembrolizumab alone or in combination with chemotherapy as first-line therapy for patients with advanced gastric or gastroesophageal junction adenocarcinoma: results from the phase II nonrandomized KEYNOTE-059 study

BACKGROUND

The multicohort, phase II, nonrandomized KEYNOTE-059 study evaluated pembrolizumab ± chemotherapy in advanced gastric/gastroesophageal junction cancer. Results from cohorts 2 and 3, evaluating first-line therapy, are presented.

METHODS

Patients ≥ 18 years old had previously untreated recurrent or metastatic gastric/gastroesophageal junction adenocarcinoma. Cohort 3 (monotherapy) had programmed death receptor 1 combined positive score ≥ 1. Cohort 2 (combination therapy) received pembrolizumab 200 mg on day 1, cisplatin 80 mg/m² on day 1 (up to 6 cycles), and 5-fluorouracil 800 mg/m² on days 1-5 of each 3-week cycle (or capecitabine 1000 mg/m² twice daily in Japan). Primary end points were safety (combination therapy) and objective response rate per Response Evaluation Criteria in Solid Tumors version 1.1 by central review, and safety (monotherapy).

RESULTS

In the combination therapy and monotherapy cohorts, 25 and 31 patients were enrolled; median follow-up was 13.8 months (range 1.8-24.1) and 17.5 months (range 1.7-20.7), respectively. In the combination therapy cohort, grade 3/4 treatment-related adverse events occurred in 19 patients (76.0%); none were fatal. In the monotherapy cohort, grade 3-5 treatment-related adverse events occurred in seven patients (22.6%); one death was attributed to a treatment-related adverse event (pneumonitis). The objective response rate was 60.0% [95% confidence interval (CI), 38.7-78.9] (combination therapy) and 25.8% (95% CI 11.9-44.6) (monotherapy).

CONCLUSIONS

Pembrolizumab demonstrated antitumor activity and was well tolerated as monotherapy and in combination with chemotherapy in patients with previously untreated advanced gastric/gastroesophageal junction adenocarcinoma.

CLINICAL TRIAL

ClinicalTrials.gov NCT02335411.

New insights into the inflamed tumor immune microenvironment of gastric cancer with lymphoid stroma: from morphology and digital analysis to gene expression

BACKGROUND

Gastric cancer with lymphoid stroma (GCLS) is characterized by prominent stromal infiltration of T-lymphocytes. The aim of this study was to investigate GCLS biology through analysis of clinicopathological features, EBV infection, microsatellite instability (MSI), immune gene-expression profiling and PD-L1 status in neoplastic cells and tumor immune microenvironment.

METHODS

Twenty-four GCLSs were analyzed by RNA in situ hybridization for EBV (EBER), PCR/fragment analysis for MSI, immunohistochemistry (PD-L1, cytokeratin, CD3, CD8), co-immunofluorescence (CK/PD-L1, CD68/PD-L1), NanoString gene-expression assay for immune-related genes and PD-L1 copy number alterations. CD3+ and CD8+ T-cell densities were calculated by digital analysis. Fifty-four non-GCLSs were used as control group.

RESULTS

GCLSs displayed distinctive clinicopathological features, such as lower pTNM stage (p = 0.02) and better overall survival (p = 0.01). EBV+ or MSI-high phenotype was found in 66.7 and 16.7% cases, respectively. GCLSs harbored a cytotoxic T-cell-inflamed profile, particularly at the invasive front of tumors (p < 0.01) and in EBV+ cases (p = 0.01). EBV+ GCLSs, when compared to EBV- GCLSs, showed higher mRNA expression of genes related to Th1/cytotoxic and immunosuppressive biomarkers. PD-L1 protein expression, observed in neoplastic and immune stromal cells (33.3 and 91.7%, respectively), and PD-L1 amplification (18.8%) were restricted to EBV+/MSI-high tumors and correlated with high values of PD-L1 mRNA expression.

CONCLUSIONS

This study shows that GCLS has a distinctive clinico-pathological and molecular profile. Furthermore, through an in-depth study of tumor immune microenvironment-by digital analysis and mRNA expression profiling-it highlights the role of EBV infection in promoting an inflamed tumor microenvironment, with putative therapeutic implications.

Hedgehog signaling induces PD-L1 expression and tumor cell proliferation in gastric cancer

Tumor cells expressing programmed cell death ligand 1 (PD-L1) interact with PD-1 on CD8+ cytotoxic T lymphocytes (CTLs) to inhibit CTL effector function. In gastric cancer, the mechanism regulating PD-L1 is unclear. The Hedgehog (Hh) signaling pathway is reactivated in various cancers including gastric. Here we tested the hypothesis that Hh-induced PD-L1 inactivates effector T cell function and allows gastric cancer cell proliferation. Mouse organoids were generated from tumors of a triple-transgenic mouse model engineered to express an activated GLI2 allele, GLI2A, in Lgr5-expressing stem cells, (mTGOs) or normal mouse stomachs (mGOs). Bone marrow-derived dendritic cells (DCs) were pulsed with conditioned media collected from normal (mGOCM) or cancer (mTGOCM) organoids. Pulsed DCs and CTLs were then co-cultured with either mGOs or mTGOs in the presence of PD-L1 neutralizing antibody (PD-L1Ab). Human-derived gastric cancer organoids (huTGOs) were used in drug and xenograft assays. Hh/Gli inhibitor, GANT-61 significantly reduced the expression of PD-L1 and tumor cell proliferation both in vivo and in vitro. PD-L1Ab treatment induced tumor cell apoptosis in mTGO/immune cell co-cultures. GANT-61 treatment sensitized huTGOs to standard-of-care chemotherapeutic drugs both in vivo and in vitro. Thus, Hh signaling mediates PD-L1 expression in gastric cancer cells and subsequently promotes tumor proliferation.

From Tumor Immunology to Immunotherapy in Gastric and Esophageal Cancer

Esophageal and gastric cancers represent tumors with poor prognosis. Unfortunately, radiotherapy, chemotherapy, and targeted therapy have made only limited progress in recent years in improving the generally disappointing outcome. Immunotherapy with checkpoint inhibitors is a novel treatment approach that quickly entered clinical practice in malignant melanoma and renal cell cancer, but the role in esophageal and gastric cancer is still poorly defined. The principal prognostic/predictive biomarkers for immunotherapy efficacy currently considered are PD-L1 expression along with defects in mismatch repair genes resulting in microsatellite instability (MSI-H) phenotype. The new molecular classification of gastric cancer also takes these factors into consideration. Available reports regarding PD-1, PD-L1, PD-L2 expression and MSI status in gastric and esophageal cancer are reviewed to summarize the clinical prognostic and predictive role together with potential clinical implications. The most important recently published clinical trials evaluating checkpoint inhibitor efficacy in these tumors are also summarized.

PD-L1 and immune infiltrates are differentially expressed in distinct subgroups of gastric cancer

This study investigates the association of PD-L1 expression and immune cell infiltrates and their impact on clinical outcome, in addition to their overlap with microsatellite instability (MSI), HER2 and ATM molecular subgroups of gastric cancer (GC). PD-L1 membrane expression on tumour cells (TC) and infiltrating immune cells (IC), CD3 + T-lymphocytes, CD8+ cytotoxic T-cells, ATM and HER2 were assessed by immunohistochemistry (IHC) in the ACRG (Asian Cancer Research Group) GC cohort (N = 380). EBV status was determined using in situ hybridization and MSI status was performed using PCR and MLH1 IHC. The PD-L1 segment was associated with increased T-cell infiltrates, while the MSI-high segment was enriched for PD-L1, CD3, and CD8. Multivariate analysis confirmed PD-L1 positivity, high CD3 and high CD8 as independent prognostic factors for both disease-free survival and overall survival (all p < 0.05). Patients with MSI-high tumours had better overall survival by both univariate and multivariate analysis. The ATM-low and HER2-high subgroups differed markedly in their immune profile; the ATM-low subgroups enriched for MSI, PD-L1 positivity and CD8 + T-cells, while the HER2 segment was enriched for MSS, with no enrichment for immune markers. Hence, we demonstrate a molecular profiling approach that can divide GC into four molecular subgroups, namely ATM-low, HER2-high, PD-L1 positive and MSI-high with differing levels of immune infiltrates and prognostic significance which may help to stratify patients for response to targeted therapies.

Role of the HDAC6/STAT3 pathway in regulating PD-L1 expression in osteosarcoma cell lines

Histone deacetylases (HDACs), initially described as histone modifiers, have more recently been verified to target various other proteins unrelated to the chromatin environment. On this basis, findings of the current study demonstrates that the pharmacological or genetic abrogation of HDAC6 in osteosarcoma cell lines down-regulates the expression of program death receptor ligand-1 (PD-L1), an important co-stimulatory molecule expressed in cancer cells, which activates the inhibitory regulatory pathway PD-1 in T cells. As shown by our results, the mechanism by which HDAC6 regulated PD-L1 expression was mediated by the transcription factor STAT3. In addition, we observed that selective HDAC6 inhibitors could inhibit tumor progression in vivo. Crucially, these results provide an essential pre-clinical rationale and justification for the necessity of further research on HDAC6 inhibitors as potential immuno-modulatory agents in osteosarcoma.

Immunotherapy in advanced gastric cancer, is it the future?

The prognosis of advanced gastric cancer remains extremely poor despite the use of standard therapies such as chemotherapy and biological agents. Blocking immune checkpoint especially programmed cell death-1 (PD-1) and its ligand (PD-L1 or B7-H1), has proven efficacy in several solid cancers, and seems to become a potential option in gastric cancer treatment. This review will focus on data describing the immune microenvironment of gastric tumors on which blocking PD-1/PD-L1 axis may have an anti-tumor efficacy. Then, the encouraging results of clinical trials evaluating anti-PD-1/PD-L1-based therapeutic strategy in first or later-line settings will be discuss. Finally, clinical outcomes according to PD-L1 expression, mismatch repair phenotype and other potential predictive biomarkers of anti-tumor response will be described. Altogether, immunotherapy seems promising in advanced gastric cancer in monotherapy or in combining strategies probably for a specific subgroup of patients who need to be better identified.

Poor prognosis in Epstein-Barr virus-negative gastric cancer with lymphoid stroma is associated with immune phenotype

BACKGROUND

Gastric cancer with lymphoid stroma (GCLS) is pathologically characterized by poorly developed tubular structures with a prominent lymphocytic infiltration. Its clinical and prognostic features differ in patients positive and negative for Epstein-Barr virus (EBV) infection. This study analyzed the expression of programmed cell death-1 (PD-1), programmed cell death ligand-1 (PD-L1), and the density of tumor-infiltrating lymphocytes (TILs) including CD3+ and CD8+ T cells, as well as their prognostic significance in patients with GCLS.

METHODS

The study included 58 patients with GCLS (29 EBV+ and 29 EBV-) who underwent curative resection. Expression of CD3, CD8, PD-1, and PD-L1 in tumor cells and TILs was analyzed using a quantitative multispectral imaging system (Opal™), with these results validated by immuno-histochemical assays for PD-L1 on whole slide sections.

RESULTS

The proportion of tumors overexpressing PD-L1 (31.0 vs. 0%, P = 0.002), TIL density (4548 vs. 2631/mm², P < 0.001), and intra-tumoral CD8+ T-cell density (2650 vs. 1060/mm², P < 0.001) were significantly higher in EBV+ than in EBV- GCLS. In addition, CD8+/CD3+ T-cell ratio was higher in EBV+ than in EBV- GCLS (55.3 vs. 35.8%, P < 0.001). Lower TIL density, defined as < 1350/mm², was a significant negative factor of survival.

CONCLUSIONS

Despite histopathological similarity, quantitative multispectral imaging revealed differences in the tumor immune micro-environment between EBV+ and EBV- GCLS, indicating that the underlying pathogenesis differs in these two disease entities. TIL density may be a prognostic marker in patients with GCLS.

Immunohistochemistry Biomarkers Predict Survival in Stage II/III Gastric Cancer Patients: From a Prospective Clinical Trial

Purpose

Identification of biomarkers to predict recurrence risk is essential to improve adjuvant treatment strategies in stage II/III gastric cancer patients. This study evaluated biomarkers for predicting survival after surgical resection.

Materials and Methods

This post-hoc analysis evaluated patients from the CLASSIC trial who underwent D2 gastrectomywith orwithout adjuvant chemotherapy (capecitabine plus oxaliplatin) at the Yonsei Cancer Center. Tumor expressions of thymidylate synthase (TS), excision repair cross-complementation group 1 (ERCC1), and programmed death-ligand 1 (PD-L1) were evaluated by immunohistochemical (IHC) staining to determine their predictive values.

Results

Among 139 patients, IHC analysis revealed high tumor expression of TS (n=22, 15.8%), ERCC1 (n=23, 16.5%), and PD-L1 (n=42, 30.2%) in the subset of patients. Among all patients, high TS expression tended to predict poor disease-free survival (DFS; hazard ratio [HR], 1.80; p=0.053), whereas PD-L1 positivity was associated with favorable DFS (HR, 0.33; p=0.001) and overall survival (OS; HR, 0.38; p=0.009) in multivariate Cox analysis. In the subgroup analysis, poor DFS was independently predicted by high TS expression (HR, 2.51; p=0.022) in the adjuvant chemotherapy subgroup (n=66). High PD-L1 expression was associated with favorable DFS (HR, 0.25; p=0.011) and OS (HR, 0.22; p=0.015) only in the surgery-alone subgroup (n=73). The prognostic impact of high ERCC1 expression was not significant in the multivariate Cox analysis.

Conclusion

This study shows that high TS expression is a predictive factor for worse outcomes on capecitabine plus oxaliplatin adjuvant chemotherapy, whereas PD-L1 expression is a favorable prognostic factor in locally advanced gastric cancer patients.

Tumor-Intrinsic PD-L1 Signaling in Cancer Initiation, Development and Treatment: Beyond Immune Evasion

Although the role of PD-L1 in suppressing the anti-tumor immune response is extensively documented, recent discoveries indicate a distinct tumor-intrinsic role for PD-L1 in modulating epithelial-to-mesenchymal transition (EMT), cancer stem cell (CSC)-like phenotype, metastasis and resistance to therapy. In this review, we will focus on the newly discovered functions of PD-L1 in the regulation of cancer development, describe underlying molecular mechanisms responsible for PD-L1 upregulation and discuss current insights into novel components of PD-L1 signaling. Furthermore, we summarize our current understanding of the link between PD-L1 signaling and the EMT program as well as the CSC state. Tumor cell-intrinsic PD-L1 clearly contributes to cancer stemness, EMT, tumor invasion and chemoresistance in multiple tumor types. Conversely, activation of OCT4 signaling and upregulation of EMT inducer ZEB1 induce PD-L1 expression in cancer cells, thereby suggesting a possible immune evasion mechanism employed by cancer stem cells during metastasis. Our meta-analysis demonstrated that PD-L1 is co-amplified along with MYC, SOX2, N-cadherin and SNAI1 in the TCGA endometrial and ovarian cancer datasets. Further identification of immune-independent PD-L1 functions and characterization of crucial signaling events upstream or downstream of PD-L1 in diverse cancer types and specific cancer subtypes, would provide additional targets and new therapeutic approaches.

Emerging Therapies in the Management of Advanced-Stage Gastric Cancer

Globally, gastric malignancy contributes to significant cancer-related morbidity and mortality. Despite a recent approval of two targeted agents, trastuzumab and ramucirumab, the treatment options for advanced-stage gastric cancer are limited. Consequently, the overall clinical outcomes for patients with advanced-stage gastric cancer remain poor. Numerous agents that are active against novel targets have been evaluated in the course of randomized trials; however, most have produced disappointing results because of the molecular heterogeneity of gastric cancer. The Cancer Genome Atlas (TCGA) project proposed a new classification system for gastric cancer that includes four different tumor subtypes based on molecular characteristics. This change led to the identification of several distinct and potentially targetable pathways. However, most agents targeting these pathways do not elicit any meaningful clinical benefit when employed for the treatment of advanced-stage gastric cancer. Most advanced-stage gastric cancer trials currently focus on agents that modulate tumor microenvironments and cancer cell stemness. In this review, we summarize data regarding novel compounds that have shown efficacy in early phase studies and show promise as effective therapeutic agents, with special emphasis on those for which phase III trials are either planned or underway.

Gastric cancer mesenchymal stem cells derived IL-8 induces PD-L1 expression in gastric cancer cells via STAT3/mTOR-c-Myc signal axis

The expression of PD-L1 in tumor cells is one of the main causes of tumor immune escape. However, the exact mechanism for regulating PD-L1 expression in gastric cancer (GC) cells remains unclear. Our previous studies have shown that mesenchymal stem cells (MSCs) exert broad immunosuppressive potential, modulating the activity of cells either in innate or adaptive immune system to promote tumor progress. This study aims to investigate whether GCMSCs regulate the PD-L1 expression in GC cells and explore the specific molecular mechanism. The results have shown that GCMSCs enhanced PD-L1 expression in GC cells resulting in the resistance of GC cells to CD8⁺ T cells cytotoxicity. However, this resistance was attenuated with IL-8 inhibition. Further studies proved that IL-8 derived from GCMSCs induced PD-L1 expression in GC cells via c-Myc regulated by STAT3 and mTOR signaling pathways. Our data indicated that blocking IL-8 derived from GCMSCs may overcome the immune escape induced by PD-L1 in GC cells and provide a potential strategy to enhance the immunotherapy efficiency in GC.