Functional remodeling of intraperitoneal macrophages by oncolytic adenovirus restores anti-tumor immunity for peritoneal metastasis of gastric cancer.

Intraperitoneal tumor-associated macrophages (TAMs) are involved in evading anti-tumor immunity and promoting the peritoneal metastasis (PM) of gastric cancer (GC). Oncolytic viruses are known to induce the activation of host anti-tumor immunity in addition to tumor lysis. This study investigated whether a wild-type p53-loading telomerase-specific oncolytic adenovirus (OBP-702) could elicit the remodeling of intraperitoneal macrophages and enhance the efficacy of immune therapy. Increased numbers of CD163 TAMs and few CD8+ lymphocytes were immunohistochemically observed in clinical samples with PM, which suggested that TAMs were associated with the suppression of anti-tumor immunity. OBP-702 induced immunogenic cell death and upregulated PD-L1 expression in human and murine GC cell lines. Intraperitoneal administration of OBP-702 increased recruitment of CD8+ lymphocytes into the PM via the functional remodeling of intraperitoneal macrophages from TAM toward a pro-inflammatory phenotype, resulting in significantly suppressed tumor growth for the in vivo model. Furthermore, the combination of intraperitoneal OBP-702 with anti-programmed cell death-1 antibody enhanced anti-tumor immunity and prolonged the survival of mice bearing PM. Intraperitoneal immunotherapy using OBP-702 restores anti-tumor immunity via the remodeling of intraperitoneal macrophages in addition to direct tumor lysis and cooperates with immune checkpoint inhibitors to suppress PM in GC.

Functional loss of p53 cooperates with the in vivo microenvironment to promote malignant progression of gastric cancers.

p53 mutations are frequently detected in malignant gastric cancers. However, the molecular mechanisms by which loss of p53 function promotes gastric cancer are not clear. We utilized Gan mice (K19-Wnt1/C2mE), which have functional p53 and develop intestinal-type gastric tumors, to investigate the role of p53 in gastric cancer progression by knocking out p53. We found that gastric epithelial cells acquire tumorigenicity in the subcutis of C57BL/6 mice as a result of Wnt activation, COX-2 activation and p53 deficiency. With repeated allograft transfers, these gastric epithelial cells gradually acquired the properties of malignant gastric cancer. Loss of p53 conferred cell stemness and induced epithelial to mesenchymal transition (EMT) in gastric epithelial cells, and these properties were further enhanced by the in vivo microenvironment, ultimately leading to gastric cancer formation and metastasis. We also found that the in vivo microenvironment enhanced activation of the COX-2 pathway, which further contributed to cancer progression. With this system, we have succeeded in recapitulating the development of malignant gastric cancer from gastric epithelial cells in a normal immune environment.

Identification of telomere-associated molecules by engineered DNA-binding molecule-mediated chromatin immunoprecipitation (enChIP).

Biochemical analysis of molecular interactions in specific genomic regions requires their isolation while retaining molecular interactions in vivo. Here, we report isolation of telomeres by engineered DNA-binding molecule-mediated chromatin immunoprecipitation (enChIP) using a transcription activator-like (TAL) protein recognizing telomere repeats. Telomeres recognized by the tagged TAL protein were immunoprecipitated with an antibody against the tag and subjected to identification of telomere-binding molecules. enChIP-mass spectrometry (enChIP-MS) targeting telomeres identified known and novel telomere-binding proteins. The data have been deposited to the ProteomeXchange with identifier PXD000461. In addition, we showed that RNA associated with telomeres could be isolated by enChIP. Identified telomere-binding molecules may play important roles in telomere biology. enChIP using TAL proteins would be a useful tool for biochemical analysis of specific genomic regions of interest.