Arihiro Aihara

Identification of Pancreatic Cancer Stem Cells and Selective Toxicity of Chemotherapeutic Agents

BACKGROUND & AIMS Identification and purification of cancer stem cells (CSCs) could lead to new therapeutic targets, but their heterogeneous expansion is an obstacle to their study. We investigated whether it is possible to monitor pancreatic CSCs in real time, based on their intrinsic low level of proteasome activity. METHODS We engineered human pancreatic adenocarcinoma cells (PANC1, MIAPaCa2, BxPC3, and KLM1) to express a green fluorescent molecule fused to the degron of ornithine decarboxylase (Gdeg) from a retroviral vector; the fluorescent Gdeg accumulates in CSCs as a result of low activity of the 26S proteasome. Cells with high and low levels of fluorescence (Gdeg(high) and Gdeg(low)) were isolated by flow cytometry; tumor growth was analyzed in immunocompromised mice. We performed a screen for agents that were specifically toxic to pancreatic CSCs, in a synthetic lethal manner. RESULTS Gdeg(high) cells, but not Gdeg(low) cells, formed spheres and underwent asymmetric division-features of CSCs. Injection of as few as 10 Gdeg(high) cells led to tumor formation in mice. Gemcitabine was toxic to cultured Gdeg(low) cells, whereas Gdeg(high) cells were resistant. We observed that quercetin was toxic to Gdeg(high) cells in culture and in pre-established tumors grown from these cells in mice. Nuclear accumulation of β-catenin was detected in Gdeg(high), but not Gdeg(low), and lost after exposure to quercetin. CONCLUSIONS We used a fluorescence marker system for level of proteasome activity to identify pancreatic cancer cells with features of cancer stem cells. We identified quercetin as a compound that is specifically toxic to pancreatic CSCs.

Long-term and perioperative outcomes of laparoscopic versus open liver resection for hepatocellular carcinoma with propensity score matching: A multi-institutional Japanese study

The aim of this study was to compare the long‐term outcomes and perioperative outcomes of laparoscopic liver resection (LLR) with those of open liver resection (OLR) for hepatocellular carcinoma (HCC) between well‐matched patient groups.

The selective Aurora B kinase inhibitor AZD1152 as a novel treatment for hepatocellular carcinoma

BACKGROUND & AIMS We previously identified that high Aurora B expression was associated with hepatocellular carcinoma (HCC) recurrence due to tumor dissemination. In this preclinical study, a novel inhibitor of Aurora B kinase was evaluated as a treatment for human HCC. METHODS AZD1152 is a selective inhibitor of Aurora B kinase. Twelve human HCC cell lines were analyzed for Aurora B kinase expression and the in vitro effects of AZD1152. The in vivo effects of AZD1152 were analyzed in a subcutaneous xenograft model and a novel orthotopic liver xenograft model. RESULTS Aurora B kinase expression varied among the human HCC cell lines and was found to correlate with inhibition of cell proliferation, accumulation of 4N DNA, and the proportion of polyploid cells following administration of AZD1152-hydroxyquinazoline-pyrazol-anilide (AZD1152-HQPA). AZD1152-HQPA suppressed histone H3 phosphorylation and induced cell death in a dose-dependent manner. Growth of subcutaneous human HCC xenografts was inhibited by AZD1152 administration. In an orthotopic hepatoma model, treatment with AZD1152 significantly decelerated tumor growth and increased survival. Pharmacobiological analysis revealed that AZD1152 induced the rapid suppression of phosphohistone H3, followed by cellular apoptosis in the liver tumors but not in the normal tissues of the orthotopic models. CONCLUSIONS Our preclinical studies indicate that AZD1152 is a promising novel therapeutic approach for the treatment of HCC.

Visualization of stem cell features in human hepatocellular carcinoma reveals in vivo significance of tumor‐host interaction and clinical course

Hepatocellular carcinoma (HCC) is one of the most aggressive malignancies because of recurrence and/or metastasis even after curative resection. Emerging evidence suggests that tumor metastasis and recurrence might be driven by a small subpopulation of stemness cells, so‐called cancer stem cells (CSCs). Previous investigations have revealed that glioma and breast CSCs exhibit intrinsically low proteasome activity and that breast CSCs also reportedly contain a lower reactive oxygen species (ROS) level than corresponding nontumorigenic cells. Here we visualized two stem cell features, low proteasome activity and low intracellular ROS, in HCC cells using two‐color fluorescence activated cell sorting to isolate cells with stem cell features. These cells were then analyzed for their division behavior in normoxia and hypoxia, expression of stem cell markers, tumorigenicity, metastatic potential, specific gene expression signatures, and their clinical implications. A visualized small subpopulation of HCC cells demonstrated asymmetric divisions. Their remarkable tumorigenicity in nonobese diabetic/severe combined immunodeficient mice suggested the cancer initiation potential of these HCC CSCs. Comprehensive gene expression analysis revealed that chemokine‐related genes were up‐regulated in the CSCs subpopulation. Our identified HCC CSCs facilitated the migration of macrophages in vitro and demonstrated metastatic potential by way of recruitment of macrophages in vivo. In patients who undergo curative operation for HCC, the CSC‐specific gene signature in the liver microenvironment significantly correlates with recurrence. Conclusion: Based on these findings, the stem cell feature monitoring system proposed here is a promising tool to analyze the in vivo significance of CSC microenvironments in human HCCs. (HEPATOLOGY 2013;)

Expression of Aurora B and alternative variant forms in hepatocellular carcinoma and adjacent tissue

Surgical resection is the effective treatment modality for hepatocellular carcinoma (HCC); however, rapid recurrence of the tumors are frequently observed even after apparently curative resection. The recurrence and prognostic assessment of patients with HCC after resection is an important clinical issue. We recently reported that aberrant expression of Aurora B is observed in primary HCC, and that it can be a predictive factor for HCC recurrence exceeding Milan criteria after curative hepatectomy. In this study we investigated the expression of the newly observed Aurora B splicing variant forms in HCC, and their roles in hepatocarcinogenisis. The expression of Aurora B and splicing variant forms were screened in 125 HCC patients (94 chronic hepatitis with cirrhosis background liver specimens), 18 metastatic liver cancer patients and 16 normal liver specimens by cDNA microarray, reverse transcription – polymerase chain reaction (RT–PCR) and Real time quentitative Reverse Transcription PCR (qRT‐PCR). The results showed that expression of Aurora B splicing variant 2 (AURKB‐Sv2) variant form was absent in normal liver and was higher in metastatic liver cancer than HCC. This aberrant expression was associated with the advanced stages of HCC (P < 0.01), correlated with a poor outcome (P = 0.008) and short disease‐free period (P = 0.018). Furthermore, AURKB‐Sv2 variant form is associated with a higher level of serum α‐fetoprotein, protein induced by vitamin K absence or antagonist‐II (PIVKAII), tumor capsular invasion, multiple tumor formation and at an age younger than those with other variant forms (P < 0.05). The results thus suggest that AURKB‐Sv2 variant form is more significantly associated with the advanced stages of HCC than others and is a marker of poor prognosis. Founded in the tumor capsular invasion and multiple tumor regions, suggests that this might play a role in enhancing multiple malignant tumor formation and recurrence of HCC in hepatocarcinogenesis. This is the first study to report clinicopathological significance of aberrant expression of AURKB‐Sv2 variant form in hepatocellular carcinoma. (Cancer Sci 2009; 100: 472–480)

Dominant Expression of DCLK1 in Human Pancreatic Cancer Stem Cells Accelerates Tumor Invasion and Metastasis

Patients with pancreatic cancer typically develop tumor invasion and metastasis in the early stage. These malignant behaviors might be originated from cancer stem cells (CSCs), but the responsible target is less known about invisible CSCs especially for invasion and metastasis. We previously examined the proteasome activity of CSCs and constructed a real-time visualization system for human pancreatic CSCs. In the present study, we found that CSCs were highly metastatic and dominantly localized at the invading tumor margins in a liver metastasis model. Microarray and siRNA screening assays showed that doublecortin-like kinase 1 (DCLK1) was predominantly expressed with histone modification in pancreatic CSCs with invasive and metastatic potential. Overexpression of DCLK1 led to amoeboid morphology, which promotes the migration of pancreatic cancer cells. Knockdown of DCLK1 profoundly suppressed in vivo liver metastasis of pancreatic CSCs. Clinically, DCLK1 was overexpressed in the metastatic tumors in patients with pancreatic cancer. Our studies revealed that DCLK1 is essential for the invasive and metastatic properties of CSCs and may be a promising epigenetic and therapeutic target in human pancreatic cancer.

Contrast‐enhanced intraoperative ultrasonography for vascular imaging of hepatocellular carcinoma: Clinical and biological significance

Abnormal tumor vascularity is one of the typical features of hepatocellular carcinoma (HCC). In this study, the significance of contrast‐enhanced intraoperative ultrasonography (CEIOUS) images of HCC vasculature was evaluated by clinicopathological and gene expression analyses. We enrolled 82 patients who underwent curative hepatic resection for HCC with CEIOUS. Clinicopathological and gene expression analyses were performed according to CEIOUS vasculature patterns. CEIOUS images of HCC vasculatures were classified as reticular HCC or thunderbolt HCC. Thunderbolt HCC was significantly correlated with higher alpha‐fetoprotein levels, tumor size, histological differentiation, portal vein invasion, and tumor‐node‐metastasis stage, and these patients demonstrated a significantly poorer prognosis for both recurrence‐free survival (P = 0.0193) and overall survival (P = 0.0362) compared with patients who had reticular HCC. Gene expression analysis revealed that a rereplication inhibitor geminin was significantly overexpressed in thunderbolt HCCs (P = 0.00326). In vitro knockdown of geminin gene reduced significantly the proliferation of human HCC cells. Immunohistochemical analysis confirmed overexpression of geminin protein in thunderbolt HCC (P < 0.0001). Multivariate analysis revealed geminin expression to be an independent factor in predicting poor survival in HCC patients (P = 0.0170). Conclusion: CEIOUS vascular patterns were distinctly identifiable by gene expression profiling associated with cellular proliferation of HCC and were significantly related to HCC progression and poor prognosis. These findings might be clinically useful as a determinant factor in the postoperative treatment of HCC. (HEPATOLOGY 2013)

A cell-surface β-hydroxylase is a biomarker and therapeutic target for hepatocellular carcinoma

Hepatocellular carcinoma (HCC) has a poor prognosis as a result of widespread intra‐ and extrahepatic metastases. There is an urgent need to understand signaling cascades that promote disease progression. Aspartyl‐(asparaginyl)‐β‐hydroxylase (ASPH) is a cell‐surface enzyme that generates enhanced cell motility, migration, invasion, and metastatic spread in HCC. We hypothesize that inhibition of its enzymatic activity could have antitumor effects. Small molecule inhibitors (SMIs) were developed based on the crystal structure of the ASPH catalytic site followed by computer‐assisted drug design. Candidate compounds were tested for inhibition of β‐hydroxylase activity and selected for their capability to modulate cell proliferation, migration, invasion, and colony formation in vitro and to inhibit HCC tumor growth in vivo using orthotopic and subcutaneous murine models. The biological effects of SMIs on the Notch signaling cascade were evaluated. The SMI inhibitor, MO‐I‐1100, was selected because it reduced ASPH enzymatic activity by 80% and suppressed HCC cell migration, invasion, and anchorage‐independent growth. Furthermore, substantial inhibition of HCC tumor growth and progression was observed in both animal models. The mechanism(s) for this antitumor effect was associated with reduced activation of Notch signaling both in vitro and in vivo. Conclusions: These studies suggest that the enzymatic activity of ASPH is important for hepatic oncogenesis. Reduced β‐hydroxylase activity generated by the SMI MO‐I‐1100 leads to antitumor effects through inhibiting Notch signaling cascade in HCC. ASPH promotes the generation of an HCC malignant phenotype and represents an attractive molecular target for therapy of this fatal disease. (Hepatology 2014;60:1302–1313)

LRH1 as a driving factor in pancreatic cancer growth

Liver receptor homolog 1 (LRH1), directs the development and differentiation of embryonic pancreas, and is overexpressed in pancreatic cancer (PC). We hypothesized that LRH1 promotes PC growth. Cell proliferation and tumorigenicity in nude mice were compared between empty vector-transfected (control) and stable LRH1-overexpressed PC cell lines. The subsequent tumor burden, vasculature development, and histologic features were evaluated. LRH1 overexpression enhanced the expression of downstream target genes (cyclin D1/E1) and stimulated cell proliferation in PC cell lines. LRH1 upregulated cyclin E1 truncated T1/T2 isoforms expression which may occur through ERα-calpain1 signaling. Compared with the control, LRH1 overexpressing stable cells generated tumors with increased weight, proliferation index and enhanced angiogenesis. Cyclin D1/E1 and calpain1 were overexpressed in human PC tumors compared to adjacent normal pancreas. These observations demonstrate that LRH1 promotes PC growth and angiogenesis, suggesting that LRH1 is a driving factor in tumorigenesis and may serve as a potential therapeutic target.

The difficulty of laparoscopic liver resection

Grading of difficulty is needed for laparoscopic liver resection (LLR). Indications for LLR are expanding worldwide from minor to major resections, particularly in institutions having surgeons with advanced skills. If the degrees of surgical difficulty were defined, it would serve as a useful guide when introducing LLR and stepping up to the more advanced LLR. As no previous study has addressed the degrees of difficulty of various LLR procedures, we devised a practical scoring system for this purpose. We extracted the following five factors from preoperative information to score difficulty levels: (1) tumor location, (2) extent of liver resection, (3) tumor size, (4) proximity to major vessels, and (5) liver function. This difficulty index is comprised of the cumulative score for the five individual factors. There has not yet been a standard definition of difficulty. Our proposed scoring system might be a practical means of assessing the difficulty of LLR procedures. However, this system must be prospectively validated.