Expression of cell adhesion molecule 1 in gastric neck and base glandular cells: Possible involvement in peritoneal dissemination of signet ring cells

Expression of cell adhesion molecule 1 in human and murine endometrial glandular cells and its increase during the proliferative phase by estrogen and cell density

AIMS

Cell adhesion molecule 1 (CADM1) mediates interepithelial adhesion and is upregulated in crowded epithelial monolayers. This study aimed to examine CADM1 expression in the human endometrium of proliferative and secretory phases, and its transcriptional regulation in terms of estrogen stimuli and higher cellularity.

MAIN METHODS

CADM1 immunohistochemistry was conducted on endometrial tissues from women in their 40s and adult mice subcutaneously injected with estradiol following ovariectomy. Dual-luciferase reporter assays were conducted using human endometrial HEC-50B and HEC-1B cells and reporter plasmids harboring the human CADM1 3.4-kb promoter and its deleted and mutated forms. Cells were transfected with estrogen receptor α cDNA and reporter plasmids, and treated with estradiol before luciferase activity measurement.

KEY FINDINGS

Immunohistochemistry revealed that CADM1 was clearly expressed on the lateral membranes of the simple columnar glandular cells in the proliferative phase, but not in the secretory phase, from both women and the mouse model. The glandular cell density increased two-fold in the proliferative phase. Reporter assays identified three Sp1-binding sites as estradiol-responsive elements in the proximal region (from -223 to -84) of the transcription start site (+1) in HEC-50B cells. When the cell culture was started at eight-fold higher cell density, the CADM1 3.4-kb promoter was transactivated at a two-fold higher level in HEC-50B cells. This cell density effect was not detected for the CADM1 2.3-kb or 1.6-kb promoter.

SIGNIFICANCE

Two (proximal and distal) promoter regions are suggested to function additively to transactivate CADM1 in endometrial glandular cells that crowd in the proliferative phase.

Comprehensive Roles and Future Perspectives of Exosomes in Peritoneal Metastasis of Gastric Cancer

Gastric cancer (GC) is one of the most prevalent digestive malignancies. A great number of patients at first visit or post curative resections are diagnosed with widespread metastasis within the peritoneal cavity. Overwhelming evidence has demonstrated that exosomes, a variety of biologically functional extracellular vesicles comprising active factors, mediate the progression and metastasis of GC. Although the regulatory mechanisms of exosomes remain fairly elusive, they are responsible for intercellular communication between tumor cells and normal stroma, cancer-related fibroblasts, immune cells within the primary tumor and metastatic niche. In this review, we provide new insight into the molecular signatures of GC-associated exosomes in reprogramming the tumor microenvironment and the subsequent promotion of peritoneal metastasis—including infiltration of the gastric wall, implantation of tumor cells onto the pre-metastatic peritoneum, and remodeling of the pre-metastatic niche. Based on this review, we hope to draw a more general conclusion for the functions of exosomes in the progression and peritoneal metastasis of GC and highlight the future perspective on strategies targeting exosomes in prognostic biomarkers and therapy for peritoneal metastasis.

Exposure to Blood Components and Inflammation Contribute to Pancreatic Cancer Progression

BACKGROUND

Pancreatectomy is a highly invasive procedure with extensive intraoperative blood loss (IBL) and high risk of postoperative pancreatic fistula (POPF). We conducted an experimental and retrospective clinical study to determine whether the malignant behaviors of pancreatic cancer cells were enhanced by exposure to blood components in vitro and to evaluate the oncological significance of high IBL and POPF in pancreatic cancer.

METHODS

This study included 107 patients undergoing radical pancreatectomy in the University of Yamanashi Hospital between 2011 and 2017, classified into high (n = 29) and low (n = 78) IBL groups. In vitro experiments included functional analyses of Panc-1 pancreatic cancer and normal mesothelial cells exposed to patient blood components, and clinical data were used to assess the contribution of IBL and POPF to patient outcomes.

RESULTS

The migration (p = 0.007), invasion (p < 0.001), and proliferation (p < 0.01) of Panc-1 cells were enhanced with platelet coculture. The ability of Panc-1 cells to adhere mesothelial cells was enhanced by plasma coincubation, especially in the presence of inflammation (p < 0.001). High IBL was associated with worse overall survival (p = 0.007) and increased locoregional recurrence (p = 0.003) in patients. POPF enhanced the negative prognostic significance of high IBL (p < 0.001 for overall survival, p = 0.001 for locoregional recurrence), indicating the oncological negative effects of high IBL and POPF.

CONCLUSIONS

Blood components, especially platelets, and inflammation enhance the malignant behaviors of pancreatic cancer cells, potentially contributing to poor prognosis for pancreatic cancer patients.

Differential Expression of CADM1 in Gastrointestinal Stromal Tumors of Different Sites and with Different Gene Abnormalities

Gastrointestinal stromal tumor (GIST), the most common mesenchymal tumor of the human gastrointestinal tract, differentiating toward the interstitial cell of Cajal (ICC), arises predominantly in the stomach and small intestine. Small intestinal GISTs appear to have worse prognosis than gastric GISTs. In a pilot study of a cDNA expression chip using several GISTs, we found that Cell Adhesion Molecule 1 (CADM1), which could contribute to tumor growth and infiltration, is expressed more strongly in small intestinal GISTs than gastric GISTs. In the present study, we examined CADM1 expression in GISTs of different sites and with different gene abnormalities using a large number of gastric and small intestinal GISTs. First, immunoblotting confirmed significantly higher CADM1 expression in small intestinal GISTs with exon 11 c-kit mutation than gastric GISTs with exon 11 c-kit mutation. Real-time PCR also revealed that small intestinal GISTs with exon 11 c-kit mutation showed significantly higher CADM1 mRNA than gastric GISTs with exon 11 c-kit mutation. Although most small intestinal GISTs showed high CADM1 mRNA expression regardless of gene abnormality types, different CADM1 expression was detected between gastric GISTs with c-kit mutation and those with PDGFRA mutation. Immunohistochemistry showed that many small intestinal GISTs were CADM1-positive but most gastric GISTs CADM1-negative or -indefinite. In the normal gastric and small intestinal walls, immunoreactivity of CADM1 was detected only in nerves, but neither in gastric ICCs nor small intestinal ICCs, indicating that the high CADM1expression in small intestinal GISTs might be acquired during tumorigenesis. Different CADM1 expression between gastric and small intestinal GISTs might be related to different prognoses between them. Further functional experiments are needed to elucidate the role of CADM1 on GIST biology, and there is a possibility that targeting therapy against CADM1 has a preventive effect for tumor spreading in small intestinal GISTs.

Cell Adhesion Molecule 1 Contributes to Cell Survival in Crowded Epithelial Monolayers

When epithelial cells in vivo are stimulated to proliferate, they crowd and often grow in height. These processes are likely to implicate dynamic interactions among lateral membranous proteins, such as cell adhesion molecule 1 (CADM1), an immunoglobulin superfamily member. Pulmonary epithelial cell lines that express CADM1, named NCI-H441 and RLE-6TN, were grown to become overconfluent in the polarized 2D culture system, and were examined for the expression of CADM1. Western analyses showed that the CADM1 expression levels increased gradually up to 3 times in a cell density-dependent manner. Confocal microscopic observations revealed dense immunostaining for CADM1 on the lateral membrane. In the overconfluent monolayers, CADM1 knockdown was achieved by two methods using CADM1-targeting siRNA and an anti-CADM1 neutralizing antibody. Antibody treatment experiments were also done on 6 other epithelial cell lines expressing CADM1. The CADM1 expression levels were reduced roughly by half, in association with cell height decrease by half in 3 lines. TUNEL assays revealed that the CADM1 knockdown increased the proportion of TUNEL-positive apoptotic cells approximately 10 folds. Increased expression of CADM1 appeared to contribute to cell survival in crowded epithelial monolayers.