Comprehensive molecular characterization of clinical responses to PD-1 inhibition in metastatic gastric cancer. Nat Med. 2018;24:1449-1458. [PMID: 30013197 DOI: 10.1038/s41591-018-0101-z]

Targeting VEGFR2 with Ramucirumab strongly impacts effector/ activated regulatory T cells and CD8+ T cells in the tumor microenvironment

BACKGROUND

Several studies have established a correlation between the VEGF-VEGFR2 axis and an immunosuppressive microenvironment; this immunosuppression can be overcome by anti-angiogenic reagents, such as ramucirumab (RAM). However, little is known about the immunological impact of anti-angiogenic reagents within the tumor microenvironment in human clinical samples. This study aimed at investigating the effects of RAM on the tumor microenvironmental immune status in human cancers.

METHODS

We prospectively enrolled 20 patients with advanced gastric cancer (GC) who received RAM-containing chemotherapy. We obtained paired samples from peripheral blood mononuclear cells (PBMCs) and tumor-infiltrating lymphocytes (TILs) in primary tumors both pre- and post-RAM therapy to assess immune profiles by immunohistochemistry and flow cytometry.

RESULTS

Within the tumor microenvironment, both PD-L1 expression and CD8+ T-cell infiltration increased after RAM-containing therapies. In addition, CD45RA-FOXP3highCD4+ cells (effector regulatory T cells [eTreg cells]) and PD-1 expression by CD8+ T cells were significantly reduced in TILs compared with PBMCs after RAM-containing therapies. Patients with partial response and longer progression-free survival had significantly higher pre-treatment eTreg frequencies in TILs than those with progressive disease. In in vitro analysis, VEGFR2 was highly expressed by eTreg cells. Further, VEGFA promoted VEGFR2+ eTreg cell proliferation, and this effect could be inhibited by RAM.

CONCLUSIONS

This study suggests that the frequency of eTreg cells in TILs could be a biomarker for stratifying clinical responses to RAM-containing therapies. Further, we propose that RAM may be employed as an immuno-modulator in combination with immune checkpoint blockade.

Computational measurement of tumor immune microenvironment in gastric adenocarcinomas

The use of four groups of tumor immune microenvironments (TME) based on PD-L1 and tumor-infiltrating T lymphocytes (TIL) is a reliable biomarker for anti-PD-1/PD-L1 inhibitor therapy. We classified the TME in 241 gastric cancers which were subdivided according to 40 EBV+, 76 microsatellite instability-high (MSI-H), and 125 EBV-/microsatellite-stable (MSS) subtypes by quantitative image analysis (QIA) and correlated the results with mRNA expression levels. The mean PD-L1 ratio and CD8 ratio in EBV+, MSI-H, and EBV−/MSS GCs were significantly different (P < 0.006). The PD-L1 ratio and CD8 ratio obtained by QIA correlated well with the RNA levels of PD-L1 (r = 0.63) and CD8 (r = 0.67), respectively. The TME were type I (PD-L1^H/CD8^H) in 45, type II (PD-L1^L/CD8^L) in 106, type III (PD-L1^H/CD8^L) in 8, and type IV (PD-L1^L/CD8^H) in 82 cases. The type I TME was significantly associated with high TIL (P = 3.0E-11) and EBV+ status (P = 8.55E-08). In conclusion, QIA results correlated well with the mRNA expression levels and classified TME of gastric cancers.

What's New in Gastric Cancer: The Therapeutic Implications of Molecular Classifications and Future Perspectives

Despite some remarkable innovations and the advent of novel molecular classifications the prognosis of patients with advanced gastric cancer (GC) remains overall poor and current clinical application of new advances is disappointing. During the last years only Trastuzumab and Ramucirumab have been approved and currently used as standard of care targeted therapies, but the systemic management of advanced disease did not radically change in contrast with the high number of molecular drivers identified. The Cancer Genome Atlas (TCGA) and Asian Cancer Research Group (ACRG) classifications paved the way, also for GC, to that more contemporary therapeutic approach called "precision medicine" even if tumor heterogeneity and a complex genetic landscape still represent a strong barrier. The identification of specific cancer subgroups is also making possible a better selection of patients that are most likely to respond to immunotherapy. This review aims to critically overview the available molecular classifications summarizing the main druggable molecular drivers and their possible therapeutic implications also taking advantage of new technologies and acquisitions.