Search

BACKGROUND: Tumor-associated antigen (TAA)-specific CD8(+) T cells are essential for nivolumab therapy, and irradiation has been reported to have the potential to generate and activate TAA-specific CD8(+) T cells. However, mechanistic insights of T-cell response during combinatorial immunotherapy using radiotherapy and nivolumab are still largely unknown. METHODS: Twenty patients included in this study were registered in the CIRCUIT trial (ClinicalTrials.gov, NCT03453164). All patients had multiple distant metastases and were intolerance or had progressed after primary and secondary chemotherapy without any immune checkpoint inhibitor. In the CIRCUIT trial, eligible patients were treated with a total of 22.5 Gy/5 fractions/5 days of radiotherapy to the largest or symptomatic lesion prior to receiving nivolumab every 2 weeks. In these 20 patients, T-cell responses during the combinatorial immunotherapy were monitored longitudinally by high-dimensional flow cytometry-based, multiplexed major histocompatibility complex multimer analysis using a total of 46 TAAs and 10 virus epitopes, repertoire analysis of T-cell receptor β-chain (TCRβ), together with circulating tumor DNA analysis to evaluate tumor mutational burden (TMB). RESULTS: Although most TAA-specific CD8(+) T cells could be tracked longitudinally, several TAA-specific CD8(+) T cells were detected de novo after irradiation, but viral-specific CD8(+) T cells did not show obvious changes during treatment, indicating potential irradiation-driven antigen spreading. Irradiation was associated with phenotypical changes of TAA-specific CD8(+) T cells towards higher expression of killer cell lectin-like receptor subfamily G, member 1, human leukocyte antigen D-related antigen, T-cell immunoglobulin and immunoreceptor tyrosine-based inhibitory motif domain, CD160, and CD45RO together with lower expression of CD27 and CD127. Of importance, TAA-specific CD8(+) T cells in non-progressors frequently showed a phenotype of CD45RO(+)CD27(+)CD127(+) central memory T cells compared with those in progressors. TCRβ clonality (inverted Pielous evenness) increased and TCRβ diversity (Pielous evenness and Diversity Evenness score) decreased during treatment in progressors (p=0.029, p=0.029, p=0.012, respectively). TMB score was significantly lower in non-progressors after irradiation (p=0.023). CONCLUSION: Oligo-fractionated irradiation induces an immune-modulating effect with potential antigen spreading and the combination of radiotherapy and nivolumab may be effective in a subset of patients with gastric cancer.

Mismatch repair deficient (dMMR)/microsatellite instability-high (MSI-H) gastric cancer (GC) exhibits an immune-active tumor microenvironment (TME) compared to MMR proficient (pMMR)/microsatellite stable/Epstein-Barr virus-negative [EBV (−)] GC. The tumor cell-intrinsic cyclic GMP–AMP synthase (cGAS)–stimulator of interferon genes (STING) pathway has been considered a key regulator of immune cell activation in the TME. However, its significance in regulating the immune-active TME in dMMR/MSI-H GC remains unclear. Here, we demonstrated that tumor cell-intrinsic cGAS–STING was highly expressed in dMMR GC compared to pMMR/EBV (−) GC. The expression of tumor cell-intrinsic STING was significantly and positively associated with the number of CD8+ tumor-infiltrating lymphocytes in GC. Analysis of TCGA datasets revealed that the expression of interferon-stimulated genes and STING downstream T-cell attracting chemokines was significantly higher in MSI-H GC compared to other subtypes of GC with EBV (−). These results suggest that tumor cell-intrinsic STING signaling plays a key role in activating immune cells in the dMMR/MSI-H GC TME and might serve as a novel biomarker predicting the efficacy of immunotherapy for GC treatment. [ABSTRACT FROM AUTHOR]

Background: The sonic hedgehog (SHH) signaling pathway is critical in fetal organogenesis. Activation of the SHH pathway has been associated with several types of human cancer; however, the clinical impact of SHH activation in patients with gastric cancer is still unknown. Methods: The present study included 41 patients with gastric cancer who underwent gastrectomy between 2000 and 2004. SHH, Patched-1 (PTCH1), Smoothened (SMO) and Glioma-associated oncogene-1 (GLI1) were examined immunohistochemically, and these of mRNAs from the cancer lesions were evaluated using real-time quantitative RT-PCR. Results: Immunohistological expressions of SHH-related molecules were relatively intense in cancer tissue, but no significant correlation was found with any clinicopathological factors of tumor. PTCH1 was only the molecule associated with poor prognosis of patients with differentiated type of tumor. For mRNA analysis, a significant correlation was demonstrated between certain clinicopathological factors and PTCH1, SMO or/and GLI1 mRNA levels. High levels of SHH and PTCH1 mRNA were associated with poor prognosis. Multivariate analysis demonstrated the PTCH1 mRNA level and liver metastasis as significant independent prognostic factors. Conclusions:PTCH1 expression in the SHH pathway was possibly involved in gastric cancer tumor progression, and could be a useful indicator for the prognosis of gastric cancer. Copyright © 2012 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]