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Hepatocellular carcinoma (HCC) is the second leading cause of cancer‐related death. High recurrence rates after curative resection and the lack of specific biomarkers for intrahepatic metastases are major clinical problems. Recently, exosomal microRNAs (miRNAs) have been reported to have a role in the formation of the pre‐metastatic niche and as promising biomarkers in patients with malignancy. Here we aimed to clarify the molecular mechanisms of intrahepatic metastasis and to identify a novel biomarker miRNA in patients with HCC. A highly intrahepatic metastatic cell line (HuH‐7M) was established by in vivo selection. HuH‐7M showed increased proliferative ability and suppression of apoptosis and anoikis. HuH‐7M and the parental cell (HuH‐7P) showed the similar expression of epithelial‐mesenchymal transition markers and cancer stem cell markers. In vivo, mice treated with exosomes derived from HuH‐7M showed increased tumorigenesis of liver metastases. Exosomes from HuH‐7M downregulated endothelial cell expression of vascular endothelial‐cadherin (VE‐cadherin) and zonula occludens‐1 (ZO‐1) in non‐cancerous regions of liver and increased the permeability of FITC‐dextran through the monolayer of endothelial cells. The miRNAs (miR‐638, miR‐663a, miR‐3648, and miR‐4258) could attenuate endothelial junction integrity by inhibiting VE‐cadherin and ZO‐1 expression. In patients with HCC, higher serum exosomal miR‐638 expression was associated with tumor recurrence. In conclusion, the miRNAs secreted from a highly metastatic cancer cell can promote vascular permeability via downregulation of endothelial expression of VE‐cadherin and ZO‐1. Serum exosomal miR‐638 expression holds potential for serving as a significant and independent prognostic marker in HCC. miR‐638, miR‐663a, miR‐3648, and miR‐4258 downregulate VE‐cadherin and ZO‐1 expression in HUVECs.

BackgroundCD36, a multi-ligand scavenger receptor, has been associated with several cancers. Many studies have revealed that CD36 contributed to cancer malignancy. This study aimed to reveal the function of CD36 expression in pancreatic ductal adenocarcinoma (PDAC).MethodsCD36 expression was characterized using immunohistochemistry in 95 clinical specimens resected from patients with PDAC. We divided patients into two groups, with different CD36 expression levels, and analyzed and compared their prognoses. CD36 expression was also assessed in PDAC cell lines. Gemcitabine-resistant (GR) PDAC cell lines were transfected with small interfering RNA (siRNA) that specifically targeted CD36 to evaluate chemoresistance and apoptosis.ResultsIn resected PDAC samples, CD36 expression was significantly correlated with microinvasion into the venous system (p = 0.0284). Patients with high CD36 expression had significantly lower overall survival (OS) and recurrence-free survival (RFS) rates than patients with low expression; thus, CD36 was an independent prognostic factor for OS and RFS. In subgroup analyses, CD36 was an independent risk factor for OS and RFS in 59 patients treated with gemcitabine adjuvant chemotherapy. CD36 expression was upregulated in PDAC–GR cell lines compared with the PDAC parent cell line. Transduction with siRNA downregulated CD36, which reduced PDAC cell resistance to gemcitabine and inhibited anti-apoptosis proteins.ConclusionCD36 expression influenced gemcitabine resistance by regulating anti-apoptosis proteins. High CD36 expression was a significant, unfavorable prognostic factor in PDAC. Anti-CD36 treatment might serve as an optional treatment for lowering resistance to gemcitabine.

CXCL9, an IFN‐γ inducible chemokine, has been reported to play versatile roles in tumor‐host interrelationships. However, little is known about its role in intrahepatic cholangiocarcinoma (iCCA). Here, we aimed to elucidate the prognostic and biological implications of CXCL9 in iCCA. Endogenous CXCL9 expression and the number of tumor‐infiltrating lymphocytes were immunohistochemically assessed in resection specimens. These data were validated in mice treated by silencing CXCL9 with short hairpin RNA. In addition, the induction of endogenous CXCL9 and the effects of CXCL9 on tumor biological behaviors were evaluated in human cholangiocarcinoma cell lines. Immunohistochemical analyses revealed that high CXCL9 expression was closely correlated with prolonged postoperative survival and a large number of tumor‐infiltrating natural killer (NK) cells. In fact, due to the trafficking of total and tumor necrosis factor‐related apoptosis‐inducing ligand‐expressing NK cells into tumors, CXCL9‐sufficient cells were less tumorigenic in the liver than CXCL9‐deficient cells in mice. Although CXCL9 involvement in tumor growth and invasion abilities differed across cell lines, it did not exacerbate these abilities in CXCL9‐expressing cell lines. We showed that CXCL9 was useful as a prognostic marker. Our findings also suggested that CXCL9 upregulation might offer a therapeutic strategy for treating CXCL9‐expressing iCCA by augmenting anti–tumor immune surveillance. CXCL9, an IFN‐γ inducible chemokine, plays versatile roles in the tumor‐host interrelationship. In this study, we demonstrated that elevated intratumoral CXCL9 expression was associated with a large number of tumor‐infiltrating NK cells, leading to favorable postoperative survival in patients with intrahepatic cholangiocarcinoma. Upregulation of CXCL9 might be an immunotherapeutic approach for treating intrahepatic cholangiocarcinoma.

Cancer stem cells (CSCs) are generally dormant or slowly cycling tumor cells that have the ability to reconstitute tumors. They are thought to be involved in tumor resistance to chemo/radiation therapy and tumor relapse and progression. However, neither their existence nor their identity within many cancers has been well defined. Here, we have demonstrated that CD13 is a marker for semiquiescent CSCs in human liver cancer cell lines and clinical samples and that targeting these cells might provide a way to treat this disease. CD13+ cells predominated in the G0 phase of the cell cycle and typically formed cellular clusters in cancer foci. Following treatment, these cells survived and were enriched along the fibrous capsule where liver cancers usually relapse. Mechanistically, CD13 reduced ROS-induced DNA damage after genotoxic chemo/radiation stress and protected cells from apoptosis. In mouse xenograft models, combination of a CD13 inhibitor and the genotoxic chemotherapeutic fluorouracil (5-FU) drastically reduced tumor volume compared with either agent alone. 5-FU inhibited CD90+ proliferating CSCs, some of which produce CD13+ semiquiescent CSCs, while CD13 inhibition suppressed the self-renewing and tumor-initiating ability of dormant CSCs. Therefore, combining a CD13 inhibitor with a ROS-inducing chemo/radiation therapy may improve the treatment of liver cancer.

BackgroundBiliary tract cancer (BTC) has few choices of chemotherapy, including gemcitabine, therefore exploring the mechanisms of gemcitabine resistance is important. We focused on lipid metabolism because biliary tract epithelial cells are essential in cholesterol and bile acid metabolism and the messenger RNA (mRNA) microarray analysis showed high acyl coenzyme A: cholesterol acyltransferase 1 (ACAT-1) expression in BTC gemcitabine-resistant (GR) cell lines. We hypothesized that aberrant accumulation of cholesteryl ester (CE) regulated by ACAT-1 could modulate GR in BTC.MethodsCE accumulations were measured in human BTC cell lines, and the relationships between CE levels, ACAT-1 expressions, and gemcitabine sensitivity were analyzed. We performed a small-interfering RNA (siRNA)-mediated knockdown and biochemical inhibition of ACAT-1 in BTC cell lines and alterations of gemcitabine sensitivity were evaluated. To evaluate the clinical significance of ACAT-1 in regard to GR, immunohistochemistry was performed and ACAT-1 expressions were analyzed in resected BTC specimens.ResultsCE levels were correlated with ACAT-1 expressions and GR in four human BTC cell lines. siRNA-mediated knockdown of ACAT-1 in two independent GR cell clones as well as ACAT-1 inhibitor treatment significantly increased gemcitabine sensitivity; knockdown of ACAT-1: 5.63- and 8.02-fold; ACAT-1 inhibitor: 8.75- and 9.13-fold, respectively. ACAT-1 expression in resected BTC specimens revealed that the disease-free survival of the ACAT-1 low-intensity group (median 2.3 years) had a significantly better outcome than that of the ACAT-1 high-intensity group (median 1.1 years) under gemcitabine treatment after surgery (*p < 0.05).ConclusionsOur findings suggest that CE and ACAT-1 might be a novel therapeutic target for GR in BTC.

Tumor endothelial cells (TECs) promote tumor angiogenesis and regulate cytotoxic T cells in the tumor microenvironment. However, the roles of TECs for tumor‐infiltrating T‐cell in hepatocellular carcinoma (HCC) is still unknown. Here, we aimed to investigate how TECs influenced tumor growth and immune responses of HCC focusing on CD8+ T‐cell infiltration and exhaustion. First, TECs were isolated from subcutaneous HCC tumors with murine HCC cell lines (BNL‐T) with magnetic selection of CD31+ cells, and normal endothelial cells (NECs) were isolated from normal liver. Second, immunocompetent mice were injected with BNL‐T alone, BNL‐T + NECs, or BNL‐T + TECs for tumor formation, and the functions and exhaustion of tumor‐infiltrating CD8+ T cells were evaluated. The mice injected with BNL‐T + TEC showed rapid tumorigenesis and a decrease in the number of infiltrating CD8+ T cells. In addition, the percentage of CD8+ T‐cell exhaustion was significantly higher in tumors from the administration of BNL‐T + TEC. Third, the next‐generation sequencing on TECs was performed to identify mRNAs that might be a novel treatment target. The molecule of glycoprotein nonmetastatic melanoma protein B (GPNMB) was identified and the functions of GPNMB was analyzed by silencing of GPNMB expression using small interfering RNAs. The silencing of GPNMB expression in TECs induced the suppression of tumor growth and T‐cell exhaustion. In conclusion, TECs induced tumor‐infiltrating T‐cell exhaustion via GPNMB expression and GPNMB might be a novel therapeutic target in HCC. Tumor endothelial cells induced exhaustion in tumor‐infiltrating T cells by upregulating GPNMB; therefore, GPNMB might be a novel therapeutic target in hepatocellular carcinoma.

BackgroundThe benefits of robotic gastrectomy (RG) over laparoscopic gastrectomy (LG) remain controversial. This single-center, propensity score-matched study aimed to compare the outcomes of RG with those of LG for treating gastric cancer.MethodsWe searched the prospective gastric cancer database of our institute for patients with gastric cancer who underwent RG or LG between January 2014 and December 2019, excluding patients with remnant stomach cancer and those who underwent concurrent surgery for comorbid malignancies. One-to-one propensity score matching was performed to reduce bias from confounding patient-related variables, and short- and long-term outcomes were compared between the groups.ResultsWe identified 1189 patients who underwent LG (n = 979) or RG (n = 210). After propensity score matching, we selected 210 pairs of patients who underwent LG (distal gastrectomy, 138; total or proximal gastrectomy, 72) or RG (distal gastrectomy, 143; total or proximal gastrectomy, 67). RG was associated with a significantly shorter operative time (RG = 201 min vs. LG = 231 min, p = 0.0051), less blood loss (RG = 13 mL vs. LG = 42 mL, p < 0.0001), lower postoperative morbidity (RG = 1.0% vs. LG = 4.8%, p = 0.0066), and a shorter postoperative hospital stay (p = 0.0002) than LG. Drain amylase levels on postoperative Days 1 and 3 in the RG group were significantly lower than those in the LG group (p < 0.0001).ConclusionsRG is a safe and feasible treatment for gastric cancer, with a shorter operative time, less blood loss, and lower postoperative morbidity than LG. The application of robotics in minimally invasive gastric cancer surgery may offer an alternative to conventional surgery. Multicenter, prospective, randomized controlled trials comparing RG with conventional LG are needed to establish the feasibility and efficacy of minimally invasive gastric cancer surgery.

BackgroundF-18 fluorodeoxyglucose-positron emission tomography (FDG-PET) has been used to diagnose and stage various cancers. In regard to biliary tract cancer (BTC), due to cholangitis it is difficult to evaluate FDG uptake caused by cancer. We previously showed that FDG-positive lymph nodes (LNs) of resectable BTC had a possibility of predicting postoperative prognosis. ObjectiveThis study aimed to validate the usability of FDG-PET for LNs using another cohort and to investigate in detail the relationship between FDG-positive LNs and the prognosis of BTC.MethodsWe measured the preoperative maximum standardized uptake value (SUVmax) at each of the 190 surgically dissected LN areas in 67 patients and investigated the prognosis using our previously determined SUVmax cut-off values of ≥ 2.8.ResultsRegarding the prognosis of patients with resectable BTC, a LN SUVmax ≥ 2.8 [PET N (+)] was a poor prognostic factor for recurrence-free survival (RFS) compared with a LN SUVmax < 2.8 [PET N (−)]. It was confirmed that the hazard ratio forest plot [PET N (+)/PET N (−)] for RFS indicated a similar tendency among subcategories. Moreover, we investigated patients with pN0 disease and demonstrated that the PET N (+) group also had a significantly worse RFS outcome compared with the PET N (−) group. Recurrence of the PET N (+) group has significantly occurred more often in LNs than that of the PET N (−) group.ConclusionHigh LN SUVmax was confirmed to be the preoperatively diagnosed prognostic risk factor for RFS in resectable BTC and could be helpful for clinical decision making regarding the perioperative treatment strategy.

In pancreatic cancer, methyltransferase-like 3 (METTL3), a N(6)-methyladenosine (m6A) methyltransferase, has a favorable effect on tumors and is a risk factor for patients’ prognosis. However, the details of what genes are regulated by METTL3 remain unknown. Several RNAs are methylated, and what genes are favored in pancreatic cancer remains unclear. By epitranscriptomic analysis, we report that polo-like kinase 1 (PLK1) is an important hub gene defining patient prognosis in pancreatic cancer and that RNA methylation is involved in regulating its cell cycle-specific expression. We found that insulin like growth factor 2 mRNA binding protein 2 (IGF2BP2) binds to m6A of PLK1 3′ untranslated region and is involved in upregulating PLK1 expression and that demethylation of this site activates the ataxia telangiectasia and Rad3-related protein pathway by replicating stress and increasing mitotic catastrophe, resulting in increased radiosensitivity. This suggests that PLK1 methylation is essential for cell cycle maintenance in pancreatic cancer and is a new therapeutic target.