Tadayuki Kou

Expression of activation-induced cytidine deaminase in human hepatocytes during hepatocarcinogenesis

Activation‐induced cytidine deaminase (AID) plays a role as a genome mutator in activated B cells, and inappropriate expression of AID has been implicated in the immunopathological phenotype of human B‐cell malignancies. Notably, we found that the transgenic mice overexpressing AID developed lung adenocarcinoma and hepatocellular carcinoma (HCC), suggesting that ectopic expression of AID can lead to tumorigenesis in epithelial tissues as well. To examine the involvement of AID in the development of human HCC, we analyzed the AID expression and its correlation with mutation frequencies of the p53 gene in liver tissues from 51 patients who underwent resection of primary HCCs. The specific expression, inducibility by cytokine stimulation and mutagenic activity of AID were investigated in cultured human hepatocytes. Only trace amounts of AID transcripts were detected in the normal liver; however, endogenous AID was significantly upregulated in both HCC and surrounding noncancerous liver tissues with underlying chronic hepatitis or liver cirrhosis (p < 0.05). Most liver tissues with underlying chronic inflammation with endogenous AID upregulation already contained multiple genetic changes in the p53 gene. In both hepatoma cell lines and cultured human primary hepatocytes, the expression of AID was substantially induced by TGF‐β stimulation. Aberrant activation of AID in hepatocytes resulted in accumulation of multiple genetic alterations in the p53 gene. Our findings suggest that the aberrant expression of AID is observed in human hepatocytes with several pathological settings, including chronic liver disease and HCC, which might enhance the genetic susceptibility to mutagenesis leading to hepatocarcinogenesis.

Activation-Induced Cytidine Deaminase Links Between Inflammation and the Development of Colitis-Associated Colorectal Cancers

BACKGROUND & AIMS Activation-induced cytidine deaminase (AID) was originally identified as an inducer of somatic hypermutations in the immunoglobulin gene. We recently revealed that ectopic AID expression serves as a link between the cellular editing machinery and high mutation frequencies, leading to human cancer development. In the current study, we investigated whether AID might contribute to the development of colitis-associated colorectal cancers. METHODS The expression and regulation of AID in association with proinflammatory cytokine stimulation were investigated in cultured colonic cells. Genotoxic activity of AID in colonic cells was analyzed using retroviral system. Immunohistochemistry for AID was carried out on various human colonic tissues specimens. RESULTS Tumor necrosis factor-alpha induced aberrant AID expression via IkappaB kinase-dependent nuclear factor (NF)-kappaB-signaling pathways in human colonic epithelial cells. Moreover, AID expression was also induced in response to the T helper cell 2-driven cytokines interleukin-4 and interleukin-13, which are activated in human inflammatory bowel disease. Aberrant activation of AID in colonic cells preferentially induced genetic mutations in the TP53 gene, whereas there were no nucleotide alterations of the APC gene. Immunohistochemistry revealed enhanced expression of endogenous AID protein not only in the inflamed colonic mucosa of ulcerative colitis patients but also in tumor lesions of colitis-associated colorectal cancers. CONCLUSIONS Our findings indicate that proinflammatory cytokine-mediated aberrant expression of AID in colonic epithelial cells is a genotoxic factor linking inflammation, somatic mutations, and colorectal cancer development.

Activation‐induced cytidine deaminase links bile duct inflammation to human cholangiocarcinoma

Chronic inflammation plays a critical role in oncogenesis in various human organs. Epidemiological studies have demonstrated that patients with primary sclerosing cholangitis have a predisposition to develop cholangiocarcinoma (CC). However, the molecular mechanisms that account for the development of bile duct carcinomas are not well defined. We recently provided evidence that activation‐induced cytidine deaminase (AID), a member of the DNA/RNA editing enzyme family, is implicated in human tumorigenesis via its mutagenic activity. We found here that ectopic AID production is induced in response to tumor necrosis factor‐α (TNF‐α) stimulation via the IkappaB kinase‐dependent nuclear factor‐κB (NF‐κB) activation pathway in human cholangiocarcinoma‐derived cells. Aberrant expression of AID in biliary cells resulted in the generation of somatic mutations in tumor‐related genes, including p53, c‐myc, and the promoter region of the INK4A/p16 sequences. In human tissue specimens, real‐time reverse transcription polymerase chain reaction (RT‐PCR) analyses revealed that AID was increased significantly in 28 of 30 CC tissues (93%), whereas only trace amounts of AID were detected in the normal liver. Immunohistochemistry showed that all of the CC tissue samples examined showed overproduction of endogenous AID protein in cancer cells. Moreover, immunostaining for AID was detectable in 16 of 20 bile epithelia in the tissues underlying primary sclerosing cholangitis. Conclusion: The proinflammatory cytokine‐induced aberrant production of AID might link bile duct inflammation to an enhanced genetic susceptibility to mutagenesis, leading to cholangiocarcinogenesis. (HEPATOLOGY 2008;47:888–896.)

Serum miR-21, miR-29a, and miR-125b Are Promising Biomarkers for the Early Detection of Colorectal Neoplasia.

Purpose: Circulating microRNAs (miRNA) are emerging as promising diagnostic biomarkers for colorectal cancer, but their usefulness for detecting early colorectal neoplasms remains unclear. This study aimed to identify serum miRNA biomarkers for the identification of patients with early colorectal neoplasms. Experimental Design: A cohort of 237 serum samples from 160 patients with early colorectal neoplasms (148 precancerous lesions and 12 cancers) and 77 healthy subjects was analyzed in a three-step approach that included a comprehensive literature review for published biomarkers, a screening phase, and a validation phase. RNA was extracted from sera, and levels of miRNAs were examined by real-time RT-PCR. Results: Nine miRNAs (miR-18a, miR-19a, miR-19b, miR-20a, miR-21, miR-24, miR-29a, miR-92, and miR-125b) were selected as candidate biomarkers for initial analysis. In the screening phase, serum levels of miR-21, miR-29a, and miR-125b were significantly higher in patients with early colorectal neoplasm than in healthy controls. Elevated levels of miR-21, miR-29a, and miR-125b were confirmed in the validation phase using an independent set of subjects. Area under the curve (AUC) values for serum miR-21, miR-29a, miR-125b, and their combined score in discriminating patients with early colorectal neoplasm from healthy controls were 0.706, 0.741, 0.806, and 0.827, respectively. Serum levels of miR-29a and miR-125b were significantly higher in patients who had only small colorectal neoplasms (≤5 mm) than in healthy subjects. Conclusions: Because serum levels of miR-21, miR-29a, and miR-125b discriminated patients with early colorectal neoplasm from healthy controls, our data highlight the potential clinical use of these molecular signatures for noninvasive screening of patients with colorectal neoplasia. Clin Cancer Res; 21(18); 4234–42. ©2015 AACR.

Dynamics of Hepatitis B Virus Quasispecies in Association with Nucleos(t)ide Analogue Treatment Determined by Ultra-Deep Sequencing

Background and Aims Although the advent of ultra-deep sequencing technology allows for the analysis of heretofore-undetectable minor viral mutants, a limited amount of information is currently available regarding the clinical implications of hepatitis B virus (HBV) genomic heterogeneity. Methods To characterize the HBV genetic heterogeneity in association with anti-viral therapy, we performed ultra-deep sequencing of full-genome HBV in the liver and serum of 19 patients with chronic viral infection, including 14 therapy-naïve and 5 nucleos(t)ide analogue(NA)-treated cases. Results Most genomic changes observed in viral variants were single base substitutions and were widely distributed throughout the HBV genome. Four of eight (50%) chronic therapy-naïve HBeAg-negative patients showed a relatively low prevalence of the G1896A pre-core (pre-C) mutant in the liver tissues, suggesting that other mutations were involved in their HBeAg seroconversion. Interestingly, liver tissues in 4 of 5 (80%) of the chronic NA-treated anti-HBe-positive cases had extremely low levels of the G1896A pre-C mutant (0.0%, 0.0%, 0.1%, and 1.1%), suggesting the high sensitivity of the G1896A pre-C mutant to NA. Moreover, various abundances of clones resistant to NA were common in both the liver and serum of treatment-naïve patients, and the proportion of M204VI mutants resistant to lamivudine and entecavir expanded in response to entecavir treatment in the serum of 35.7% (5/14) of patients, suggesting the putative risk of developing drug resistance to NA. Conclusion Our findings illustrate the strong advantage of deep sequencing on viral genome as a tool for dissecting the pathophysiology of HBV infection.

Cytomegalovirus infection in patients with ulcerative colitis diagnosed by quantitative real-time PCR analysis

Cytomegalovirus (CMV) infection is an exacerbating factor in patients with ulcerative colitis (UC) (1–8). The prognosis of patients with UC complicated by CMV infection is generally poor if the infection is not recognized at an early stage (4, 8, 9). Therefore, it is important to consider the possibility of CMV infection and to make a rapid diagnosis when patients with UC do not respond to conventional corticosteroid therapy (6, 10). We describe here three patients with refractory UC complicated by CMV infection, which were diagnosed by quantitative real-time polymerase chain reaction (PCR) assay of CMV DNA in colonic tissue.

Reactivation from occult HBV carrier status is characterized by low genetic heterogeneity with the wild-type or G1896A variant prevalence

BACKGROUND & AIMS Individuals negative for hepatitis B surface antigen (HBsAg) but positive for antibodies to hepatitis B core antigen (anti-HBc) are at risk of hepatitis B virus (HBV) reactivation under immunosuppressive conditions. We investigated clinical features and viral genetics in patients with reactivation from occult HBV infection triggered by chemotherapy or immunosuppressive therapy. METHODS Clinical courses of 14 individuals originally HBsAg-negative but anti-HBc-positive that experienced HBV reactivation were examined. Ultra-deep sequencing analysis of the entire HBV genome in serum was conducted. Prevalence of the G1896A variant in latently infected livers was determined among 44 healthy individuals that were HBsAg-negative but anti-HBc-positive. RESULTS In 14 cases, HBV reactivation occurred during (n=7) and after (n=7) termination of immunosuppressive therapy. Ultra-deep sequencing revealed that the genetic heterogeneity of reactivated HBV was significantly lower in patients with reactivation from occult HBV carrier status compared with that in patients from HBsAg carrier status. The reactivated viruses in each case were almost exclusively the wild-type G1896 or G1896A variant. The G1896A variant was detected in 42.9% (6/14) of cases, including two cases with fatal liver failure. The G1896A variant was observed in the liver tissue of 11.4% (5/44) of individuals with occult HBV infection. CONCLUSIONS Reactivation from occult HBV infection is characterized by low genetic heterogeneity, with the wild-type G1896 or G1896A variant prevalent.

Regression of B-Cell Lymphoma of the Liver with Hepatitis C Virus Infection After Treatment with Pegylated Interferon-α and Ribavirin

The pathogenesis of human B-cell lymphoma is not well understood, although some types of B-cell lymphoma seem to be related to infection with pathogens such as Helicobacter pylori [1]. Accumulating evidence reveals a high incidence of B-cell lymphoma in patients with hepatitis C virus (HCV) infection, suggesting a link between HCV infection and the development of B-cell lymphoma [2–6]. We describe here a case of primary B-cell lymphoma of the liver with HCV infection that regressed following the eradication of HCV.

The possibility of clinical sequencing in the management of cancer

Comprehensive genomic profiling using next-generation sequencing technologies provides insights into understanding the genomic architecture of human cancer. This new understanding of the cancer genome allows us to identify many more genomic alterations occurring within tumors than before, some of which could be potential therapeutic targets through molecular targeted agents. Currently, a large number of molecular targeted agents are being developed, and consequently, cancer treatment is rapidly shifting from empiric therapy employing cytotoxic anticancer drugs to genotype-directed therapy using molecular targeted agents. In current daily clinical practice, hotspot-based single-gene assays that detect RAS mutations in colorectal cancer or EGFR mutations in non-small cell lung cancer are widely used to identify variants. However, it is becoming evident that more comprehensive genomic analysis is crucial in identifying the patient population that may benefit from molecular targeted therapy and the accelerated development of novel drugs for early clinical trials. For these purposes, an increasing number of gene panel-based targeted sequencing is commercially available in clinical practice from sequencing companies. Despite several challenges in implementing this approach, comprehensive genomic profiling and identification of actionable mutations is likely to become one of the standard options in the management of cancer in the near future. The use of clinical sequencing has the potential to usher a new era in precision medicine for cancer diagnosis and treatment. In this review, we discuss the application of comprehensive genomic profiling using next-generation sequencing technologies in clinical oncology and address the current challenges for its implementation.

Clinical outcome of elderly patients with unresectable pancreatic cancer treated with gemcitabine plus S-1, S-1 alone, or gemcitabine alone: Subgroup analysis of a randomised phase III trial, GEST study.

BACKGROUND In the GEST study of unresectable pancreatic cancer, S-1 demonstrated non-inferiority compared to gemcitabine, but gemcitabine plus S-1 (GS) did not show superiority over gemcitabine for overall survival (OS). We performed subgroup analysis of these data focused on the efficacy and safety of these regimens as a first-line treatment for elderly patients. METHODS Elderly patients (≥ 70 years, n = 261) treated for unresectable pancreatic cancer (GS: n = 90, S-1: n = 85 and gemcitabine: n = 86) were analysed. RESULTS No significant differences between the GS, S-1, or gemcitabine groups in OS (median: 10.2, 8.0 and 8.5 months, respectively) or objective response rates (27.6%, 25.3% and 14.3%, respectively) were noted. Grade ≥ III adverse haematological events were observed more frequently in GS-treated than in S-1- or gemcitabine-treated elderly patients (p < 0.001 and p = 0.016, respectively). Four of 8 patients aged ≥ 80 years experienced serious adverse events. CONCLUSIONS S-1 and gemcitabine are both efficacious options for treatment of elderly patients with unresectable pancreatic cancer. Conversely, first-line treatment of elderly patients with GS should only be used after careful consideration.