Epigenetic silencing of diacylglycerol kinase gamma in colorectal cancer

Diacylglycerol kinases (DGKs) are important regulators of cell signaling and have been implicated in human malignancies. Whether epigenetic alterations are involved in the dysregulation of DGKs in cancer is unknown, however. We therefore analyzed methylation of the promoter CpG islands of DGK genes in colorectal cancer (CRC) cell lines. We found that DGKG, which encodes DGKγ, was hypermethylated in all CRC cell lines tested (n = 9), but was not methylated in normal colonic tissue. Correspondingly, DGKG expression was suppressed in CRC cell lines but not in normal colonic tissue, and was restored in CRC cells by treatment with the DNA methyltransferase inhibitor 5-aza-2'-deoxycytidine (5-aza-dC). DGKG methylation was frequently observed in primary CRCs (73/141, 51.8%) and was positively associated with KRAS and BRAF mutations and with the CpG island methylator phenotype (CIMP). DGKG methylation was also frequently detected in colorectal adenomas (89 of 177, 50.3%), which suggests it is an early event during colorectal tumorigenesis. Ectopic expression of wild-type DGKγ did not suppress CRC cell proliferation, but did suppress cell migration and invasion. Notably, both constitutively active and kinase-dead DGKγ mutants exerted inhibitory effects on CRC cell proliferation, migration and invasion, and the wild-type and mutant forms of DGKγ all suppressed Rac1 activity in CRC cells. These data suggest DGKG may play a tumor suppressor role in CRC.

Abstract P6-07-05: PD-L1 expression and decreased tumor-infiltrating lymphocytes are associated with poor prognosis in patients with triple negative breast cancer

Background: Tumor microenvironment has been considered to have an active role in determining the aggressiveness of tumor cells. Recently, programmed cell death ligand-1 (PD-L1) expression or tumor-infiltrating lymphocytes (TILs) are known to be an important prognostic factor of breast cancer. However, the correlation of expression of PD-L1 and TILs still remains unclear. Triple-negative breast cancer (TNBC) is a heterogeneous tumor that encompasses many different subclasses. Further identification of these subclasses is necessary in order to predict prognosis and choose appropriate treatments. Our goal was to correlate PD-L1 expression with clinicopathological features including TILs by using a large cohort of TNBCs.

Patients and Methods: This study included 248 patients with primary TNBC who underwent resection without neoadjuvant chemotherapy at our three hospitals between January 2004 and December 2014. The tumor subtypes were routinely determined immunohistochemically by using resected specimens. IHC scoring for PD-L1 expression was defined in reference to that for HER2 expression. PD-L1 positivity was defined as both IHC 2+ and IHC 3+. Cases were defined as high if stromal TILs ≥50% according to recommendations by the International TILs Working Group.

Results: Of the 248 TNBCs, PD-L1 were expressed as positive in 103 (41.5%) tumors, and TILs were highly present in 118 (47.6%) tumors. PD-L1 expression was significantly correlated with higher levels of TILs (P < 0.0001). There was no significant difference when the prognosis of the patients who had PD-L1-positive tumors was compared with that of the patients who had PD-L1-negative tumors (P = 0.56 in recurrence free survival [RFS] and P = 0.13 in overall survival [OS]). Meanwhile, the patients with high-TILs tumors had longer OS, compared to the patients with low-TILs tumors (P = 0.55 in RFS and P = 0.016 in OS). The analysis in the cross effect between PD-L1 expression and TILs using cox proportional hazards model demonstrated that the PD-L1 expression and TILs are not independent factors(P = 0.0018 in RFS and P = 0.015 in OS). The PD-L1-positive group with low-TILs had significantly shorter survival than the PD-L1-positive group with high-TILs (hazard ratio [HR] = 4.7, 95% confidence interval [CI] 1.6–12.7, P = 0.0067 in RFS; HR = 8.4, 95%CI 2.3-30.3, P = 0.0019 in OS).

Conclusions: Our data indicated that PD-L1 expression was related to higher levels of TILs, and PD-L1-positive tumors with low-TILs were associated with poor prognosis in patients with TNBCs. It is proposed that these biomarkers may be of use for predicting their prognosis and essential in the subclassification of TNBCs.

Citation Format: Mori H, Kubo M, Yamaguti R, Nishimura R, Osako T, Arima N, Okumura Y, Okido M, Yamada M, Kai M, Kishimoto J, Oda Y, Nakamura M. PD-L1 expression and decreased tumor-infiltrating lymphocytes are associated with poor prognosis in patients with triple negative breast cancer [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P6-07-05.

TET1 Depletion Induces Aberrant CpG Methylation in Colorectal Cancer Cells

Aberrant DNA methylation is commonly observed in colorectal cancer (CRC), but the underlying mechanism is not fully understood. 5-hydroxymethylcytosine levels and TET1 expression are both reduced in CRC, while epigenetic silencing of TET1 is reportedly associated with the CpG island methylator phenotype. In the present study, we aimed to clarify the relationship between loss of TET1 and aberrant DNA methylation in CRC. Stable TET1 knockdown clones were established using Colo320DM cells, which express high levels of TET1, and HCT116 cells, which express TET1 at a level similar to that in normal colonic tissue. Infinium HumanMethylation450 BeadChip assays revealed increased levels of 5-methylcytosine at more than 10,000 CpG sites in TET1-depleted Colo320DM cells. Changes in DNA methylation were observed at various positions within the genome, including promoters, gene bodies and intergenic regions, and the altered methylation affected expression of a subset of genes. By contrast, TET1 knockdown did not significantly affect DNA methylation in HCT116 cells. However, TET1 depletion was associated with attenuated effects of 5-aza-2’-deoxycytidine on gene expression profiles in both cell lines. These results suggest that loss of TET1 may induce aberrant DNA methylation and may attenuate the effect of 5-aza-2’-deoxycytidine in CRC cells.

Epigenetic silencing of NTSR1 is associated with lateral and noninvasive growth of colorectal tumors

Our aim was to identify DNA methylation changes associated with the growth pattern and invasiveness of colorectal cancers (CRCs). Comparison of the methylation statuses of large (≥20 mm in diameter along the colonic surface) noninvasive tumors (NTs) and small (<20 mm in diameter along the colonic surface) invasive tumors (ITs) using CpG island microarray analysis showed neurotensin receptor 1 (NTSR1) to be hypermethylated in large NTs. Quantitative bisulfite pyrosequencing revealed that NTSR1 is frequently methylated in colorectal tumors, with large NTs exhibiting the highest methylation levels. The higher NTSR1 methylation levels were associated with better prognoses. By contrast, NTSR1 copy number gains were most frequent among small ITs. Methylation of NTSR1 was associated with the gene's silencing in CRC cell lines, whereas ectopic expression of NTSR1 promoted proliferation and invasion by CRC cells. Analysis of primary tumors composed of adenomatous and malignant portions revealed that NTSR1 is frequently methylated in the adenomatous portion, while methylation levels are generally lower in the cancerous portions. These results suggest that NTSR1 methylation is associated with lateral and noninvasive growth of colorectal tumors, while low levels of methylation may contribute to the malignant potential through activation of NTSR1. Our data also indicate that NTSR1 methylation may be a prognostic biomarker in CRC.

Abstract 3385: Identification of tumor endothelium-related genes in colorectal cancer

Background and Aims:

Angiogenesis is a hallmark of cancer development that has been considered an attractive therapeutic target. In this study, we aimed to unravel the molecular mechanism of tumor angiogenesis in colorectal cancer (CRC).

Materials and Methods:

We isolated endothelial and epithelial cells from surgically resected 14 human CRC tissues by using antibodies against endothelial (CD146) and epithelial markers (EpCAM). RNA sequencing was carried out using 3 pairs of normal and tumor endothelial cells. Expression of the genes was validated using quantitative RT-PCR, immunohistochemistry. Functions of a selected gene were carried analyzed by tumor conditioned medium (TCM) experiments, tube formation assay, gene expression microarray and cell cycle analysis.

Results:

Through RNA-seq analysis, we identified 18 genes, which were upregulated in the endothelial cells isolated from CRC tissues. We further validated the results by performing quantitative RT-PCR and immunohistochemical analysis in a larger series of clinical samples, and identified gene A as a novel candidate of the tumor endothelium-related gene. Expression of gene A was also upregulated in human umbilical vein endothelial cells (HUVECs) treated with TCM obtained from CRC cell lines. Knockdown of gene A in HUVECs suppressed in vitro tube formation and induced G1 cell cycle arrest. Microarray analysis revealed that gene A knockdown induced expression changes of approximately 300 genes in HUVECs, and gene ontology analysis showed that genes related to cell cycle or cell division were significantly enriched in the affected genes. To confirm our findings in vivo, we co-transplanted CRC cells with HUVECs into nude mice. We found that gene A knockdown in HUVECs resulted in reduced micro vessel formations in the xenograft tissues.

Conclusion:

We identified elevated expression of gene A in tumor endothelial cells of primary colorectal cancer tissues. Our results suggest that gene A may play an important role in the angiogenesis in colorectal cancer, and that it could be a potential therapeutic target.

Citation Format: Akira Yorozu, Eiichiro Yamamoto, Reo Maruyama, Masahiro Kai, Toshihiko Nishidate, Tomohisa Furuhata, Tamotsu Sugai, Hiromu Suzuki. Identification of tumor endothelium-related genes in colorectal cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3385.

Abstract P5-05-04: MALDI mass spectrometry imaging profile of low molecular metabolites in breast carcinoma tissues embedded in frozen tissue microarray

[Background]

Metabolomics is now widely utilized for searching disease markers or identification of new drug targets. In common method, tissue samples originated in human resected specimens are stored by formalin-fixed, paraffin-embedded (FFPE) blocks. However, these samples are inadequate to measure low molecular metabolites or lipids. Furthermore, extraction process that is required for conventional mass-spectrometry causes the loss of information on the spatial localization of the metabolites. In this study, we directly analyzed breast carcinoma tissues embedded in frozen tissue microarray (fTMA) using MALDI mass spectrometry imaging (MALDI-MSI). With our original method, we could obtain profiles of low molecular metabolite and mapping images of several tissues at one time.

[Method]

Six fTMA blocks were constructed by 119 breast tissues (carcinoma 84, normal 35) from 99 patients and sectioned at 10 um thickness. MADLI-MSI were performed by AXIMA Confidence (Shimadzu, Japan) with 9-aminoacridine as a matrix (m/z range:50∼1000, Negative Ion mode). Carcinoma and normal area in individual tissues were confirmed by H&E staining of slide grasses after MADLI-MSI analysis. Acquired MSI data were processed with the freely available software BioMap (Novartis, Switzerland).

[Result]

We could detected 1,915 peaks derive from endogenous metabolite by direct tissue MALDI-MSI analysis of breast carcinoma fTMA. Among them, 185 peaks that could be commonly detected were subjected to further analysis. Among these peaks, we could identify 18 metabolites related to energy metabolism such as ATP. By comparison of metabolite profiles obtained from carcinoma with normal tissues, we found that the energy charge (EC; which is related to ATP, ADP and AMP concentrations) and the sum of adenosine phosphate compound intensities (AXP) were significantly higher than that of normal tissue (EC; T : N = 0.56 : 0.35, AXP; 17453 : 2066, p&lt;0.0001), but there were no significant difference with lymph node metastasis, tumor histological type and tumor size. In comparison with tumor subtype, higher EC was observed in ER(+)/ Her2(-) tumor than others but AXP showed no significant among all subtypes including Ki-67 labeling index.

[Conclusion]

A combination of fTMA and MALDI-MSI is promising approach for biomarker discovery because it can achieve high throughput metabolic mapping without obvious artifact or other problem. In this study, even though high EC value were indicated in carcinoma tissue than normal but newly biomarker candidate was indeterminate at this moment. Identification of the candidates of novel carcinoma tissue biomarker is now underway.

Citation Format: Torata N, Kubo M, Miura D, Ohuchida K, Miyazaki T, Fujimura Y, Hayakawa E, Kai M, Oda Y, Mizumoto K, Hashizume M, Nakamura M. MALDI mass spectrometry imaging profile of low molecular metabolites in breast carcinoma tissues embedded in frozen tissue microarray. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P5-05-04.

Abstract P3-06-07: Changes in the tumor microenvironment develop acquired resistance to pegylated liposomal doxorubicin in breast cancer mouse model

Pegylated liposomal doxorubicin (PLD) is one of the most widely used nanotherapeutics for the treatment of advanced/metastatic breast cancer. PLD accumulates in tumors utilizing so-called the enhanced permeation and retention (EPR) effect. Nevertheless, therapeutic efficacy and long term survival remain variable due to the development of acquired resistance. Elucidating the mechanisms of acquired resistance to PLD shall help developing new strategies to improve therapeutic outcome. It has been largely overlooked that the transport of therapeutics across biological barriers can significantly affect the efficacy of cancer therapies. Previously, we showed that the transport of PLD to tumors depends both on the tumor type and organ site. This effect is controlled by the extent to which endothelial cells (ECs) are covered by the collagen type IV (Col4) in the basement membrane, which in turn is influenced by the levels of MMP-9. Here, we have developed 4T1 tumor model which develops acquired resistance to PLD and spontaneous lung metastases. Our objective is to elucidate the resistant mechanism by evaluating the changes in the transport of PLD to the sensitive and resistant/metastatic tumors.

BALB/c mice bearing 4T1 cancers were treated with PLD intravenously when tumor volumes reached a size of approximately 100-200 mm3 . Tumor volumes in all mice decreased after initial PLD injections (sensitive). However, tumors started to grow again after 20 days and didn't respond to the second/third injections (resistant). Furthermore, 13 out of 14 mice developed spontaneous lung metastases. To elucidate the mechanisms of the resistance, mice bearing sensitive or resistant tumors were sacrificed after 24 hours of PLD injection, respectively. PLD accumulation in tumors was evaluated by imaging fluorescence of doxorubicin. Immunofluorescence staining was performed to evaluate the expression of ECs, Col4, MMP-9, and efflux pump associated p-glycoprotein (P-gp) in the primary tumors, and the expression of ECs and Col4 were also evaluated in lung metastases.

PLD accumulation was significantly decreased in the resistant tumors compared to the sensitive tumors, although P-gp expression was not increased in the resistant tumors. The amount of ECs and Col4 increased in the resistant tumors. Interestingly, ECs were covered more tightly by Col4 in the resistant tumors as compared with the sensitive tumors, which could decrease the EPR effect in the tumors. MMP-9 expression decreased in the resistant tumors, suggesting less degradation of Col4 in the basement membrane. Coverage of ECs by Col4 was similar between the metastatic lung tumors and uninvolved lung tissue as well as the resistant primary tumors, indicating the EPR effect is not increased in the metastatic tumors.

In summary, ratio of ECs covered by Col4 is higher in the resistant/metastatic tumors as compared to that in the sensitive primary tumors. This structural change in the tumor microenvironment, impeding the sufficient PLD transport to the tumors after the initial PLD therapy, can be a cause of acquired resistance/development of lung metastasis. These changes should be taken into account to develop strategies for overcoming the acquired resistance and metastasis.

Citation Format: Kai M, Liu YT, Saito Y, Ferrari M, Yokoi K. Changes in the tumor microenvironment develop acquired resistance to pegylated liposomal doxorubicin in breast cancer mouse model. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P3-06-07.

Abstract P4-09-15: BRCAness and PD-L1 expression of basal-like and not basal-like triple negative breast cancer

Background: Triple Negative Breast Cancer (TNBC) subtype occurs in approximately 20% of all patients with breast cancer and is associated with rapid growth, early metastasis and poor prognosis compared with other subtypes. TNBCs are a heterogeneous disease entity and further subclassification is needed, but still ongoing. In this study, we assessed BRCAness, defined as shared characteristics between sporadic and BRCA1-mutated tumors, in a cohort of basal-like and non-basal-like TNBCs.

Patients and Methods: DNA was isolated from formalin-fixed paraffin-embedded tumor tissues and BRCAness status was analyzed in 262 patients with primary TNBCs resected at our three hospitals between 2004 and 2014. Classification of BRCAness was performed by using Multiple Ligation-dependent Probe Amplification (MLPA) with the probemix P376 BRCA1ness by MRC (Amsterdam, Holland). The tumor subtypes were routinely determined immunohistochemically by using resected specimens. Basal-like phenotype was defined as being positive for Epidermal Growth Factor Receptor (EGFR) and/or Cytokeratin 5/6 (CK5/6). Moreover, TNBCs were stained and analyzed for programmed cell death ligand-1 (PD-L1) expression as a target of new immune therapies.

Results: Of 262 TNBCs, 232 tumors (88.5%) was a basal-like phenotype. The results of MLPA assay showed that 159 (68.5%) of 232 tumors had a BRCAness profile. Patients with basal-like BRCAness tumors were younger than patients with basal-like non-BRCAness tumors (p&lt;0.0001). There was no significant difference between the two groups regarding pathological stage. The basal-like BRCAness group had shorter relapse-free survival (RFS) and overall survival (OS) than the basal-like non-BRCAness group (p=0.028 and p=0.13, respectively), and anthracycline-based regimens provided greater benefit to the basal-like BRCAness group significantly (p=0.01 in RFS and p=0.007 in OS). PD-L1 was expressed in 71 (44.7%) of 159 basal-like TNBCs with BRCAness.

Conclusion: We reported the majority of basal-like TNBCs showed a BRCAness profile and PD-L1 expressed in approximately 50% of BRCAness tumors. It is known that about 30% of BRCAness tumors are BRCA1-mutated tumors. Those biomarkers are essential for subclassification of TNBCs and may offer not only platinum-based chemotherapy but also novel therapies, such as immune-targeted therapies of PD-1/PD-L1 inhibitors and PARP inhibitors, to patients with basal-like TNBCs with BRCAness.

Citation Format: Mori H, Kubo M, Yamada M, Kai M, Osako T, Nishimura R, Arima N, Okido M, Kuroki S, Oda Y, Nakamura M. BRCAness and PD-L1 expression of basal-like and not basal-like triple negative breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P4-09-15.

Abstract P3-03-02: Identification of molecular pathways to define the intake rate of patient-derived hormone receptor positive (HR+) breast cancer xenografts (PDXs) in NOD/SCID/interleukin-2 receptor gamma chain null (NSG) mice

Background and Purpose: Despite recent progress in our endocrine therapy of hormone receptor positive (HR+) breast cancers, a significant number of patients with primary breast cancer continue to relapse, and those with stage IV disease face a median overall survival of ∼ 3.5 years. Primary or acquired resistance to anti-estrogen-based therapies is an overarching challenge. To guide our treatment selection, there is an essential need to improve our understanding of the biology of HR+ breast tumors responsive to and those resist to anti-estrogens or aromatase inhibitors (AIs). The application of patient-derived xenografts (PDXs) in preclinical studies has begun to open the door to mimicking human disease on the research bench. However, HR+ breast cancer PDXs are difficult to establish. Although preclinical data from DeRose et al [Nat. Med. 2011: 17:1514-1520] indicate that the rate of engraftment serves as an independent predictor for poor outcome, the question which has not yet been adequately addressed is: "why some tumors can grow in mice, and some don't, even when their clinical, pathological stage and subtype (i.e. ER positivity) are same?" Here, we hypothesize that the molecular characteristics of patient HR+ tumors are key determinants to the tumor intake rate in NOD/SCID/interleukin-2 receptor gamma chain null (NSG) mice. Hence, reverse phase protein array (RPPA) analysis has be performed using human patient tumors to identify driver-pathways that impact tumor intake in NSG mice.

Results and Discussion: We compared the protein expression profile of six HR+ patient tumors (four HR+ and two HR+ HER2+), which were successfully engrafted into NSG mice and established as PDX models, with the patient tumors which we were unable to establish as PDX. Of 90 patient HR+ tumors which failed to transplant, 21 tumors were picked to match the tumor type (all of them were invasive ductal carcinoma or its metastases), clinical stage and pathological grade of engrafted tumors [Table 1]. In addition to patient tumors, six established HR+ PDXs were also submitted for analysis. Quantified expressions of 272 cancer-related proteins and phospho-proteins by RPPA have been performed on these specimens. Pathways identified as predictors of intake rate of PDXs in NSG mice, and tissues from paired PDX from mice with different passages, will be evaluated for the protein expression changes to elucidate the passage effects and generate therapeutic models based on protein expression and tumor growth.

Table 1. Characteristics of the patient tumors which were successfully established as PDX modelsERPgRHER2AgePatient ethnicityClinical stageNottingham histologic scoreSource++-63Hispanic3IIIBreast tumor+--71Hispanic2IIIBreast tumor+--52African-american4N/ABrain mets+--63Caucasian4N/AChest wall mets+-+34Caucasian2IIBreast tumor+++72Caucasian4IIIChest wall metsmets: metastases

Citation Format: Kanaya N, Somlo G, Wu J, Frankel P, Wu SV, Nguyen D, Kai M, Chan N, Meng-Yin H, Kirschenbaum M, Kruper L, Vito C, Yuan Y, Hurria A, Mortimer J, Chen S. Identification of molecular pathways to define the intake rate of patient-derived hormone receptor positive (HR+) breast cancer xenografts (PDXs) in NOD/SCID/interleukin-2 receptor gamma chain null (NSG) mice. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P3-03-02.

Clinical utility of neuronal cells directly converted from fibroblasts of patients for neuropsychiatric disorders: studies of lysosomal storage diseases and channelopathy

Methodologies for generating functional neuronal cells directly from human fibroblasts [induced neuronal (iN) cells] have been recently developed, but the research so far has only focused on technical refinements or recapitulation of known pathological phenotypes. A critical question is whether this novel technology will contribute to elucidation of novel disease mechanisms or evaluation of therapeutic strategies. Here we have addressed this question by studying Tay-Sachs disease, a representative lysosomal storage disease, and Dravet syndrome, a form of severe myoclonic epilepsy in infancy, using human iN cells with feature of immature postmitotic glutamatergic neuronal cells. In Tay-Sachs disease, we have successfully characterized canonical neuronal pathology, massive accumulation of GM2 ganglioside, and demonstrated the suitability of this novel cell culture for future drug screening. In Dravet syndrome, we have identified a novel functional phenotype that was not suggested by studies of classical mouse models and human autopsied brains. Taken together, the present study demonstrates that human iN cells are useful for translational neuroscience research to explore novel disease mechanisms and evaluate therapeutic compounds. In the future, research using human iN cells with well-characterized genomic landscape can be integrated into multidisciplinary patient-oriented research on neuropsychiatric disorders to address novel disease mechanisms and evaluate therapeutic strategies.

Calculating disability-adjusted life years (DALY) as a measure of excess cancer risk following radiation exposure

This paper has proposed that disability-adjusted life year (DALY) can be used as a measure of radiation health risk. DALY is calculated as the sum of years of life lost (YLL) and years lived with disability (YLD). This multidimensional concept can be expressed as a risk index without a probability measure to avoid the misuse of the current radiation detriment at low doses. In this study, we calculated YLL and YLD using Japanese population data by gender. DALY for all cancers in Japan per 1 Gy per person was 0.84 year in men and 1.34 year in women. The DALY for all cancers in the Japanese baseline was 4.8 in men and 3.5 in women. When we calculated the ICRP detriment from the same data, DALYs for the cancer sites were similar to the radiation detriment in the cancer sites, excluding leukemia, breast and thyroid cancer. These results suggested that the ICRP detriment overestimate the weighting fraction of leukemia risk and underestimate the weighting fraction of breast and thyroid cancer. A big advantage over the ICRP detriment is that DALY can calculate the risk components for non-fatal diseases without the data of lethality. This study showed that DALY is a practical tool that can compare many types of diseases encountered in public health.

A Screen for Epigenetically Silenced microRNA Genes in Gastrointestinal Stromal Tumors

Background

Dysregulation of microRNA (miRNA) has been implicated in gastrointestinal stromal tumors (GISTs) but the mechanism is not fully understood. In this study, we aimed to explore the involvement of epigenetic alteration of miRNA genes in GISTs.

Methods

GIST-T1 cells were treated with 5-aza-2’-deoxycytidine (5-aza-dC) and 4-phenylbutyric acid (PBA), after which miRNA expression profiles were analyzed using TaqMan miRNA arrays. DNA methylation was then analyzed using bisulfite pyrosequencing. The functions of miRNAs were examined using MTT assays, wound-healing assays, Boyden chamber assays and Matrigel invasion assays. Gene expression microarrays were analyzed to assess effect of ectopic miRNA expression in GIST-T1 cells.

Results

Of the 754 miRNAs analyzed, 61 were significantly upregulated in GIST-T1 cells treated with 5-aza-dC plus PBA. Among those, 21 miRNA genes were associated with an upstream CpG island (CGI), and the CGIs of miR-34a and miR-335 were frequently methylated in GIST-T1 cells and primary GIST specimens. Transfection of miR-34a or miR-335 mimic molecules into GIST-T1 cells suppressed cell proliferation, and miR-34a also inhibited migration and invasion by GIST-T1 cells. Moreover, miR-34a downregulated a number of predicted target genes, including PDGFRA. RNA interference-mediated knockdown of PDGFRA in GIST-T1 cells suppressed cell proliferation, suggesting the tumor suppressive effect of miR-34a is mediated, at least in part, through targeting PDGFRA.

Conclusions

Our results suggest that miR-34a and miR-335 are candidate tumor suppressive miRNAs in GISTs, and that they are frequent targets of epigenetic silencing in GISTs.

Experience and current issues with recovery management from the Fukushima accident

This paper describes the experiences of, and issues with, recovery management following the accident at Fukushima Daiichi nuclear power plant. The Fukushima accident has brought about socio-economic consequences with inevitable changes to daily life, as well as psychological effects. There is heightened concern amongst the population about the risk and effects of radiation at low doses. Experience has shown that the direct involvement of the affected population and local professionals is a decisive factor for management of the recovery phase. The radiological protection system of the International Commission on Radiological Protection (ICRP) seems to be relevant to the recovery requirements of the Fukushima accident, although some problems remain in implementation. Reference levels could play a role in improving the situation by requiring an iterative optimisation process. The Fukushima experience indicated that a routine, top-down approach using radiological criteria alone was unable to deal with the complexity of the problems, and that stakeholder engagement should be explored. The technical knowledge gap between radiation experts and the public caused a lot of confusion. Experts should understand the ethical values attached to recovery, and ICRP should be more active in promoting trustworthy radiological protection advice.

Analysis of DNA methylation in bowel lavage fluid for detection of colorectal cancer

Aberrant DNA methylation could potentially serve as a biomarker for colorectal neoplasms. In this study, we assessed the feasibility of using DNA methylation detected in bowel lavage fluid (BLF) for colorectal cancer screening. A total of 508 BLF specimens were collected from patients with colorectal cancer (n = 56), advanced adenoma (n = 53), minor polyp (n = 209), and healthy individuals (n = 190) undergoing colonoscopy. Methylation of 15 genes (miR-1-1, miR-9-1, miR-9-3, miR-34b/c, miR-124-1, miR-124-2, miR-124-3, miR-137, SFRP1, SFRP2, APC, DKK2, WIF1, LOC386758, and ZNF582) was then analyzed in MethyLight assays, after which receiver operating characteristic (ROC) curves were analyzed to assess the diagnostic performance of BLF methylation. Through analyzing BLF specimens in a training set (n = 345), we selected the three genes showing the greatest sensitivity for colorectal cancer detection (miR-124-3, 71.8%; LOC386758, 79.5%; and SFRP1, 74.4%). A scoring system based on the methylation of those three genes (M-score) achieved 82% sensitivity and 79% specificity, and the area under the ROC curve (AUC) was 0.834. The strong performance of this system was then validated in an independent test set (n = 153; AUC = 0.808). No significant correlation was found between M-score and the clinicopathologic features of the colorectal cancers. Our results demonstrate that DNA methylation in BLF specimens may be a useful biomarker for the detection of colorectal cancer.

Biological significance of the CpG island methylator phenotype

Cancers exhibiting the CpG island methylator phenotype (CIMP) are found among a wide variety of human malignancies and represent a subclass of tumors showing concurrent hypermethylation of multiple CpG islands. These CIMP-positive tumors often exhibit characteristic molecular and clinicopathological features, suggesting CIMP represents a distinct carcinogenic pathway. However, marker genes to define CIMP have been largely inconsistent among studies, which has caused results to vary. Nonetheless, recent advances in genome-wide methylation analysis have enabled the existence of CIMP to be confirmed, and large-scale cancer genome analyses have begun to unravel the previously unknown molecular basis of CIMP tumors. CIMP is strongly associated with clinical outcome, suggesting it may be a predictive biomarker.

Genome-wide re-sequencing of multidrug-resistant Mycobacterium leprae Airaku-3

Genotyping and molecular characterization of drug resistance mechanisms in Mycobacterium leprae enables disease transmission and drug resistance trends to be monitored. In the present study, we performed genome-wide analysis of Airaku-3, a multidrug-resistant strain with an unknown mechanism of resistance to rifampicin. We identified 12 unique non-synonymous single-nucleotide polymorphisms (SNPs) including two in the transporter-encoding ctpC and ctpI genes. In addition, two SNPs were found that improve the resolution of SNP-based genotyping, particularly for Venezuelan and South East Asian strains of M. leprae.

Aberrant methylation of microRNA-34b/c is a predictive marker of metachronous gastric cancer risk

BACKGROUND

Metachronous gastric cancer (GC) can develop after endoscopic resection of GC and cannot be predicted based on clinical signature. Aberrant DNA methylation in noncancerous gastric mucosa is strongly implicated in gastric carcinogenesis and could be a useful biomarker of GC risk. We evaluated the clinical utility of DNA methylation as a biomarker of metachronous GC risk.

METHOD

We carried out scheduled follow-up endoscopy in 129 patients after curative endoscopic resection of GC. Biopsy specimens were collected from noncancerous mucosa in the gastric antrum and body, after which quantitative methylation analysis of miR-34b/c, SFRP1, SFRP2, SFRP5, DKK2 and DKK3 was carried out using bisulfite pyrosequencing. The utility of the methylation for predicting the risk of metachronous GC development was assessed using Kaplan-Meier and Cox proportional hazards model analyses.

RESULTS

During the follow-up period, 17 patients (13%) developed metachronous GCs. The cumulative incidence of metachronous GC was significantly higher among patients with elevated miR-34b/c, SFRP2 and DKK2 methylation in their gastric body. MiR-34b/c showed the strongest association with the risk of metachronous GC, and the cumulative incidence of metachronous GC was much higher in the high-miR-34b/c-methylation group than the low-methylation group. Multivariate analysis adjusted for age, sex, H. pylori status and pathological findings showed miR-34b/c methylation in gastric body to be an independent predictor of metachronous GC risk.

CONCLUSION

Our results suggest that methylation of miR-34b/c in the mucosa of the noncancerous gastric body may be a useful biomarker for predicting the risk of metachronous GC.

Abstract P6-04-06: Targeting cancer stem cells in triple negative breast cancer by a combination treatment of LBH589 and salinomycin

Background and purpose:

Triple-negative breast cancer (TNBC) is aggressive with poorer prognosis compared to breast cancer that is positive for hormone receptors or HER2. This can be explained further due in part to the existence of breast cancer stem cells (BCSCs). Our lab has found that histone deacetylase (HDAC) inhibitors are effective in the growth suppression of TNBC in vitro and in vivo. To understand the mechanisms involved, we performed RNA-seq analysis for TNBC cells treated with two HDAC inhibitors (LBH589 and Entinostat). Our RNA-seq analysis and studies from other laboratories have found that HDAC inhibitors may modify multiple signaling pathways with undesired effects due to its broad reactivity. To improve the efficacy of HDAC inhibitors in the treatment of TNBCs, we have examined the effects of LBH589 in combination with several drugs. Among them, Salinomycin works effectively with LBH589. It has been used as an antibiotic for farm animals, but has been identified from a screen of a large library of chemicals to target BCSCs (Gupta et al., Cell, 2009). The purpose of this study is to examine the synergistic effect between LBH589 and Salinomycin in the anticipation of their clinical utility and to evaluate a new target therapy to treat TNBC more efficiently and completely.

Material and method:

Two TNBC cell lines (HCC1937, MDA-MB-231) were used as models to examine the combined effects of Salinomycin and LBH589. Cell proliferation studies were performed through 3-(4, 5-Dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay. To evaluate the effects on BCSC population, mammosphere assay was used for estimating self-renewal capacity and ALDEFLUOR analysis was used for monitoring the distribution of BCSCs in treated samples. For tumor induction experiments, ALDH+ cells were injected into NSG mice. As a therapeutic study, single or combined use of LBH589 (10mg/kg) and Salinomycin (5mg/kg) were peritoneally injected into non-obese diabetic scid gamma (NSG) mice 3 days a week. Tumor volume, body weight and food intake were checked weekly. For mechanistic analysis, qPCR, Western blotting and IHC were performed for gene and protein expression using tumors from mice from different treatments.

Results:

Salinomycin and LBH589 worked synergistically in the suppression of the proliferation of TNBCs (IC50 was 68.8nM and 13.1nM, respectively). Similarly, both drugs inhibited mammosphere formation and ALDH positive population in a synergistic manner. The combination of LBH589 (16nM) with Salinomycin (60nM) reduced 60% of mammosphere formation and 94% of ALDH positive population compared with DMSO treatment. In a mouse model, the combination of LBH589 and Salinomycin had an inhibitory effect on tumor growth compared with the control group and the groups treated with single drug. In all groups, no side effect was seen. The results from mechanistic studies showed that the combination of LBH589 and Salinomycin regulated the Wnt/b-catenin pathway.

Discussion:

We have evidence that the combination of LBH589 and Salinomycin has a synergistic effect on TNBC through Wnt pathway and suggested this combination could potentially be a new therapeutic strategy for exploring targeting therapy in TNBC.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P6-04-06.

Epigenetic alteration and microRNA dysregulation in cancer

MicroRNAs (miRNAs) play pivotal roles in numerous biological processes, and their dysregulation is a common feature of human cancer. Thanks to recent advances in the analysis of the cancer epigenome, we now know that epigenetic alterations, including aberrant DNA methylation and histone modifications, are major causes of miRNA dysregulation in cancer. Moreover, the list of miRNA genes silenced in association with CpG island hypermethylation is rapidly growing, and various oncogenic miRNAs are now known to be upregulated via DNA hypomethylation. Histone modifications also play important roles in the dysregulation of miRNAs, and histone deacetylation and gain of repressive histone marks are strongly associated with miRNA gene silencing. Conversely, miRNA dysregulation is causally related to epigenetic alterations in cancer. Thus aberrant methylation of miRNA genes is a potentially useful biomarker for detecting cancer and predicting its outcome. Given that many of the silenced miRNAs appear to act as tumor suppressors through the targeting of oncogenes, re-expression of the miRNAs could be an effective approach to cancer therapy, and unraveling the relationship between epigenetic alteration and miRNA dysregulation may lead to the discovery of new therapeutic targets.

Olanzapine increases hepatic glucose production through the activation of hypothalamic adenosine 5'-monophosphate-activated protein kinase

AIMS

To investigate the mechanism of the metabolic disturbance induced by the atypical antipsychotic olanzapine, we examined whether adenosine 5'-monophosphate-activated protein kinase (AMPK) in the hypothalamus and hepatic glucose production are involved in the effect of olanzapine.

METHODS

Male 6-week-old ICR mice were used. Blood glucose levels were determined by the glucose oxidase method. The mRNA levels of gluconeogenic or glycolytic enzymes were measured by reverse transcription polymerase chain reaction (RT-PCR). AMPK expression was measured by Western blotting.

RESULTS

Systemic injection of olanzapine increased blood glucose levels in both unfasted and fasted mice. However, the increase in fasted mice was less than that in unfasted mice. Central administration of olanzapine also increased the blood glucose levels in unfasted mice, but not in fasted mice. In a pyruvate tolerance test, olanzapine significantly increased blood glucose levels. In addition, olanzapine increased the mRNA levels of glucose-6-phosphatase (G6Pase), a gluconeogenic enzyme, in the liver. Furthermore, olanzapine increased phosphorylated AMPK in the hypothalamus of unfasted mice, and olanzapine-induced hyperglycaemia was inhibited by the AMPK inhibitor compound C. Central administration of the AMPK activator AICAR significantly increased G6Pase mRNA levels in the liver and blood glucose levels. Moreover, both olanzapine- and AICAR-induced hyperglycaemia were attenuated by the β-adrenergic receptor antagonist propranolol, suggesting that olanzapine and AICAR induce hepatic glucose production through the sympathetic nervous system.

CONCLUSIONS

Our results indicate that olanzapine activates AMPK in the hypothalamus, which increases hepatic glucose production via the sympathetic nervous system.

Selection of prophylactic antibiotics according to the microorganisms isolated from surgical site infections (SSIs) in a previous series of surgeries reduces SSI incidence after pancreaticoduodenectomy

BACKGROUND

The incidence of surgical site infections (SSIs) is high after pancreaticoduodenectomy (PD).

METHODS

We divided 116 consecutive patients who underwent PD into an early group (n = 58) and a later group (n = 58) according to time of surgery. In both groups, endoscopic retrograde biliary drainage was mainly employed for the patients with obstructive jaundice. In the later group, prophylactic antibiotics were selected according to the susceptibility of microorganisms isolated from SSIs in the early group. The incidence of SSIs was compared between the groups.

RESULTS

The background characteristics (including methods of preoperative biliary drainage and microorganisms in the bile obtained before or during operation) of the patients were not significantly different between the groups, except for the serum albumin level, which was lower in the later group than in the early group (P = 0.0026). The incidence of SSIs was significantly lower in the later group (24.1 %) than in the early group (46.6 %) (P = 0.0116). Belonging to the later group was one independent negative risk factor for SSI.

CONCLUSIONS

Selection of prophylactic antibiotics on the basis of microorganisms isolated from SSIs in the early group contributed to the reduced incidence of SSIs in the later group after PD.

Activation of spinal cannabinoid CB2 receptors inhibits neuropathic pain in streptozotocin-induced diabetic mice

The role of spinal cannabinoid systems in neuropathic pain of streptozotocin (STZ)-induced diabetic mice was studied. In normal mice, injection of the cannabinoid receptor agonist WIN-55,212-2 (1 and 3μg, i.t.) dose-dependently prolonged the tail-flick latency, whereas there were no changes with the injection of either cannabinoid CB1 (AM 251, 1 μg, i.t.) or CB2 (AM 630, 4 μg, i.t.) receptor antagonists. AM 251 (1 μg, i.t.), but not AM 630 (4 μg, i.t.), significantly inhibited the prolongation of the tail-flick latency induced by WIN-55,212-2 (3 μg, i.t.). In STZ-induced diabetic mice, the tail-flick latency was significantly shorter than that in normal mice. A low dose of WIN-55,212-2 (1 μg, i.t.) significantly recovered the tail-flick latency in STZ-induced diabetic mice. The effect of WIN-55,212-2 (1 μg, i.t.) in STZ-induced diabetic mice was significantly inhibited by AM 630 (4 μg, i.t.), but not AM 251 (1 μg). The selective cannabinoid CB2 receptor agonist L-759,656 (19 and 38 μg, i.t.) also dose-dependently recovered the tail-flick latency in STZ-induced diabetic mice, and this recovery was inhibited by AM 630 (4 μg, i.t.). The protein levels of cannabinoid CB1 receptors, CB2 receptors and diacylglycerol lipase α (DGL-α), the enzyme that synthesizes endocannabinoid 2-arachidonoylglycerol, in the spinal cord were examined using Western blotting. The protein levels of both cannabinoid CB1 and CB2 receptors were increased in STZ-induced diabetic mice, whereas the protein level of DGL-α was significantly decreased. These results indicate that spinal cannabinoid systems are changed in diabetic mice and suggest that cannabinoid CB2 receptor agonists might have an ability to recover diabetic neuropathic pain.

Association between genomic alterations and metastatic behavior of colorectal cancer identified by array-based comparative genomic hybridization

Colorectal cancers (CRCs) exhibit multiple genetic alterations, including allelic imbalances (copy number alterations, CNAs) at various chromosomal loci. In addition to genetic aberrations, DNA methylation also plays important roles in the development of CRC. To better understand the clinical relevance of these genetic and epigenetic abnormalities in CRC, we performed an integrative analysis of copy number changes on a genome-wide scale and assessed mutations of TP53, KRAS, BRAF, and PIK3CA and DNA methylation of six marker genes in single glands isolated from 39 primary tumors. Array-based comparative genomic hybridization (array-CGH) analysis revealed that genomic losses commonly occurred at 3q26.1, 4q13.2, 6q21.32, 7q34, 8p12-23.3, 15qcen and 18, while gains were commonly found at 1q21.3-23.1, 7p22.3-q34, 13q12.11-14.11, and 20. The total numbers and lengths of the CNAs were significantly associated with the aberrant DNA methylation and Dukes' stages. Moreover, hierarchical clustering analysis of the array-CGH data suggested that tumors could be categorized into four subgroups. Tumors with frequent DNA methylation were most strongly enriched in subgroups with infrequent CNAs. Importantly, Dukes' D tumors were enriched in the subgroup showing the greatest genomic losses, whereas Dukes' C tumors were enriched in the subgroup with the greatest genomic gains. Our data suggest an inverse relationship between chromosomal instability and aberrant methylation and a positive association between genomic losses and distant metastasis and between genomic gains and lymph node metastasis in CRC. Therefore, DNA copy number profiles may be predictive of the metastatic behavior of CRCs.

Characteristics and surgical outcome of HCC patients with low platelet count

BACKGROUND/AIMS

Hepatocellular carcinoma (HCC) patients often have low platelet count (LPC). The aim of this study was to determine unique features of HCC patients with LPC.

METHODOLOGY

HCC patients who underwent surgery were divided into two groups: LPC group (platelet count ≤100,000/mm³, n=84) and control group (platelet count >100,000/mm³, n=240). Surgical outcomes, risk factors for postoperative complications and prognostic factors were retrospectively compared.

RESULTS

HCC patients with LPC had poorer liver function, smaller tumors, less anatomical resection and more frequent postoperative liver failure than control group patients. Postoperative survival was not different between the two groups. Tumor invasion to the main branch or trunk of portal vein (Vp3, 4) was the only risk factor for postoperative substantial complications in the LPC group. Postoperative survival was worse in patients with tumor diameter ≥4 cm or multiple tumors and in those who underwent preoperative transcatheter arterial chemoembolization (TACE) in the LPC group by multivariate analysis. Among them, preoperative TACE were not prognostic factors in the control group.

CONCLUSIONS

In HCC patients with LPC, Vp3, 4 patients should be carefully monitored after surgery and preoperative TACE is not recommended for long-term postoperative survival.

Molecular dissection of premalignant colorectal lesions reveals early onset of the CpG island methylator phenotype

The concept of the CpG island methylator phenotype (CIMP) in colorectal cancer (CRC) is widely accepted, although the timing of its occurrence and its interaction with other genetic defects are not fully understood. Our aim in this study was to unravel the molecular development of CIMP cancers by dissecting their genetic and epigenetic signatures in precancerous and malignant colorectal lesions. We characterized the methylation profile and BRAF/KRAS mutation status in 368 colorectal tissue samples, including precancerous and malignant lesions. In addition, genome-wide copy number aberrations, methylation profiles, and mutations of BRAF, KRAS, TP53, and PIK3CA pathway genes were examined in 84 colorectal lesions. Genome-wide methylation analysis of CpG islands and selected marker genes revealed that CRC precursor lesions are in three methylation subgroups: CIMP-high, CIMP-low, and CIMP-negative. Interestingly, a subset of CIMP-positive malignant lesions exhibited frequent copy number gains on chromosomes 7 and 19 and genetic defects in the AKT/PIK3CA pathway genes. Analysis of mixed lesions containing both precancerous and malignant components revealed that most aberrant methylation is acquired at the precursor stage, whereas copy number aberrations are acquired during the progression from precursor to malignant lesion. Our integrative genomic and epigenetic analysis suggests early onset of CIMP during CRC development and indicates a previously unknown CRC development pathway in which epigenetic instability associates with genomic alterations.

Aberrant methylation of RASGRF1 is associated with an epigenetic field defect and increased risk of gastric cancer

Aberrant DNA methylation is implicated in the epigenetic field defect seen in gastric cancer. Our aim in this study was to identify predictive biomarkers by screening for DNA methylation in noncancerous background gastric mucosa from patients with gastric cancer. Using methylated-CpG island amplification coupled with CpG island microarray (MCAM) analysis, we identified 224 genes that were methylated in the noncancerous gastric mucosa of patients with gastric cancer. Among them, RASGRF1 methylation was significantly elevated in gastric mucosa from patients with either intestinal or diffuse type gastric cancer, as compared with mucosa from healthy individuals (8.3% vs. 22.4%, P < 0.001; 8.3% vs. 19.4%, P < 0.001). RASGRF1 methylation was independent of mucosal atrophy and could be used to distinguish both serum pepsinogen test-positive [sensitivity, 70.0%; specificity, 86.7%; area under the receiver operator characteristic (ROC) curve, AUC, 0.763] and -negative patients with gastric cancer (sensitivity, 72.2%; specificity, 87.0%; AUC, 0.844) from healthy individuals. Ectopic expression of RASGRF1 suppressed colony formation and Matrigel invasion by gastric cancer cells, suggesting it may be involved in gastric tumorigenesis. Collectively, our data suggest that RASGRF1 methylation is significantly involved in an epigenetic field defect in the stomach, and that it could be a useful biomarker to identify individuals at high risk for gastric cancer.

Nuclear expression of thioredoxin-1 in the invasion front is associated with outcome in patients with gallbladder carcinoma

BACKGROUND

Multifunctional redox protein human thioredoxin (TRX-1) is reduced by thioredoxin reductase (TRX-R). The aim of the present study was to examine the distribution of TRX-1 and TRX-R expressions in gallbladder carcinoma (GBC) to clarify their usefulness as prognostic factors after surgical resection.

METHODS

Immunohistochemical staining for TRX-1 and TRX-R was performed in GBC tissue from 38 patients who underwent surgical resection, and TRX-1/TRX-R localization in relation to outcome was examined.

RESULTS

TRX-1 protein levels were significantly higher in GBC samples than in cholecystolithiasis samples (P = 0.0174). TRX-1 expression was observed in 100% (38/38) of tumour samples and in the nucleus in 76% (29/38), with nuclear expression in the invasion front observed in 45% (13/29). TRX-R expression was only detected in the cytoplasm of cancer cells and in the invasion front in 28 samples. In all of the samples, the depth of tumour invasion, lymph node metastasis, surgical margin, curability and nuclear expression of TRX-1 in the invasion front were significant prognostic factors by univariate analysis. In 27 selected patients who underwent curative resection, both TRX-1 nuclear expression and TRX-R cytoplasmic expression in the invasion front was a significantly prognostic factor.

CONCLUSION

TRX-1 nuclear expression in the GBC invasion front is a significant prognostic marker. Patients with both TRX-1 nuclear expression and TRX-R cytoplasmic expression in the tumour invasion front should be observed carefully even if after curative resection.

DNA methylation and microRNA dysregulation in cancer

DNA methylation plays a key role in the silencing of numerous cancer-related genes, thereby affecting a number of vital cellular processes, including the cell cycle checkpoint, apoptosis, signal transduction, cell adhesion and angiogenesis. Also widely altered in human malignancies is the expression of microRNAs (miRNAs), a class of small noncoding RNAs that act as posttranscriptional regulators of gene expression. Furthermore, emerging evidence now supports the idea that DNA methylation is crucially involved in the dysregulation of miRNAs in cancer. This is in part the result of technological advances that enable more comprehensive analysis of miRNA expression profiles and the epigenome in cancer cells, which has led to the identification of a number of epigenetically regulated miRNAs. As with protein-coding genes, it appears that miRNA genes involved in regulating cancer-related pathways are silenced in association with CpG island hypermethylation. In addition, methylation in CpG island shore regions and DNA hypomethylation also appear to contribute to miRNA dysregulation in cancer. Aberrant DNA methylation of miRNA genes is a potentially useful biomarker for detecting cancer and predicting its outcome. Moreover, re-expression of miRNAs and the replacement of tumor suppressive miRNAs using miRNA mimics or expression vectors could be effective approaches to cancer therapy.

Role of hilar resection in the treatment of hilar cholangiocarcinoma

BACKGROUND/AIMS

The aim of this study was to clarify the role of bile duct resection without hepatectomy (hilar resection) in hilar cholangiocarcinoma.

METHODOLOGY

We retrospectively compared surgical results for hilar cholangiocarcinoma between 8 patients treated with hilar resection and 21 patients treated with hepatectomy.

RESULTS

All hilar resections were performed for Bismuth type I or II tumors with T2 or less lesions, whereas hepatectomy was done for type III or IV tumors excluding one type II tumor. R0 resection was equally achieved in both groups (62.5% in hilar resection group and 76.2% in hepatectomy group, p=0.469) and overall 5-year survival rates were comparable (21.9% vs. 23.6%, p=0.874). With respect to gross tumor appearance, R0 resection was achieved in all patients with papillary tumor in both groups with the excellent 5-year survivals (100% vs. 100%). In patients with nodular and flat tumors, R0 resection was achieved less frequently in the hilar resection vs. hepatectomy group (50% vs. 77.8%) mainly due to failure to clear the proximal ductal margin, resulting in poorer 5-year survival (0% vs. 18.7%).

CONCLUSIONS

Hilar resection may be indicated for papillary T1 or 2 tumors in Bismuth type I or II cholangiocarcinoma.

Some lessons on radiological protection learnt from the accident at the Fukushima Dai-ichi nuclear power plant

The accident at the Fukushima Dai-ichi nuclear power plant released a large quantity of radioactive iodine and caesium into the environment. In terms of radiological protection, the evacuation and food restrictions that were adopted in a timely manner by the authorities effectively reduced the dose received by people living in the affected area. Since late March, the transition from an emergency to an existing exposure situation has been in progress. In selecting the reference exposure levels in some areas under an existing exposure situation, the authorities tried to follow the situation-based approach recommended by the ICRP. However, a mixture of emergency and post-emergency approaches confused the people living in the contaminated areas because the reactor conditions continued to be not completely stable. In deriving the criteria in an existing exposure situation, the regulatory authority selected 20 mSv y(-1). The mothers in the affected area believed that a dose of 20 mSv y(-1) was unacceptably high for children since 1 mSv y(-1) is the dose limit for the public under normal conditions. Internet information accelerated concern about the internal exposure to children and the related health effects. From some experiences after the accident the following lessons could be learned. The selection of reference doses in existing exposure situations after an accident must be openly communicated with the public using a risk-informed approach. The detriment-adjusted nominal risk coefficient was misused for calculating the hypothetical number of cancer deaths by some non-radiation experts. It would not be possible to resolve this problem unless the ICRP addressed an alternative risk assessment to convey the meaning and associated uncertainty of the risk to an exposed population. A situation-based approach in addition to a risk-informed approach needs to be disseminated properly in order to select the level of protection that would be the best possible under the prevailing circumstances. A dialogue between radiation and other risk experts such as those dealing with chemical exposures is now needed.

A novel pit pattern identifies the precursor of colorectal cancer derived from sessile serrated adenoma

OBJECTIVES

Sessile serrated adenomas (SSAs) are known to be precursors of sporadic colorectal cancers (CRCs) with microsatellite instability (MSI), and to be tightly associated with BRAF mutation and the CpG island methylator phenotype (CIMP). Consequently, colonoscopic identification of SSAs has important implications for preventing CRCs, but accurate endoscopic diagnosis is often difficult. Our aim was to clarify which endoscopic findings are specific to SSAs.

METHODS

The morphological, histological and molecular features of 261 specimens from 226 colorectal tumors were analyzed. Surface microstructures were analyzed using magnifying endoscopy. Mutation in BRAF and KRAS was examined by pyrosequencing. Methylation of p16, IGFBP7, MLH1 and MINT1, -2, -12 and -31 was analyzed using bisulfite pyrosequencing.

RESULTS

Through retrospective analysis of a training set (n=145), we identified a novel surface microstructure, the Type II open-shape pit pattern (Type II-O), which was specific to SSAs with BRAF mutation and CIMP. Subsequent prospective analysis of an independent validation set (n=116) confirmed that the Type II-O pattern is highly predictive of SSAs (sensitivity, 65.5%; specificity, 97.3%). BRAF mutation and CIMP occurred with significant frequency in Type II-O-positive serrated lesions. Progression of SSAs to more advanced lesions was associated with further accumulation of aberrant DNA methylation and additional morphological changes, including the Type III, IV and V pit patterns.

CONCLUSIONS

Our results suggest the Type II-O pit pattern is a useful hallmark of the premalignant stage of CRCs with MSI and CIMP, which could serve to improve the efficacy of colonoscopic surveillance.

Effects of depletion of dihydropyrimidine dehydrogenase on focus formation and RPA phosphorylation

Gimeracil, an inhibitor of dihydropyrimidine dehydrogenase (DPYD), partially inhibits homologous recombination (HR) repair and has a radiosensitizing effect as well as enhanced sensitivity to Camptothecin (CPT). DPYD is the target protein for radiosensitization by Gimeracil. We investigated the mechanisms of sensitization of radiation and CPT by DPYD inhibition using DLD-1 cells treated with siRNA for DPYD. We investigated the focus formation of various kinds of proteins involved in HR and examined the phosphorylation of RPA by irradiation using Western blot analysis. DPYD depletion by siRNA significantly restrained the formation of radiation-induced foci of Rad51 and RPA, whereas it increased the number of foci of NBS1. The numbers of colocalization of NBS1 and RPA foci in DPYD-depleted cells after radiation were significantly smaller than in the control cells. These results suggest that DPYD depletion is attributable to decreased single-stranded DNA generated by the Mre11/Rad50/NBS1 complex-dependent resection of DNA double-strand break ends. The phosphorylation of RPA by irradiation was partially suppressed in DPYD-depleted cells, suggesting that DPYD depletion may partially inhibit DNA repair with HR by suppressing phosphorylation of RPA. DPYD depletion showed a radiosensitizing effect as well as enhanced sensitivity to CPT. The radiosensitizing effect of DPYD depletion plus CPT was the additive effect of DPYD depletion and CPT. DPYD depletion did not have a cell-killing effect, suggesting that DPYD depletion may not be so toxic. Considering these results, the combination of CPT and drugs that inhibit DPYD may prove useful for radiotherapy as a method of radiosensitization.

Epigenetic alteration of DNA in mucosal wash fluid predicts invasiveness of colorectal tumors

Although conventional colonoscopy is considered the gold standard for detecting colorectal tumors, accurate staging is often difficult because advanced histology may be present in small colorectal lesions. We collected DNA present in mucosal wash fluid from patients undergoing colonoscopy and then assessed the methylation levels of four genes frequently methylated in colorectal cancers to detect invasive tumors. We found that methylation levels in wash fluid were significantly higher in patients with invasive than those with noninvasive tumors. Cytologic and K-ras mutation analyses suggested that mucosal wash fluid from invasive tumors contained greater numbers of tumor cells than wash fluid from noninvasive tumors. Among the four genes, levels of mir-34b/c methylation had the greatest correlation with the invasion and showed the largest area under the receiver operating characteristic curve (AUC = 0.796). Using cutoff points of mir-34b/c methylation determined by efficiency considerations, the sensitivity/specificity were 0.861/0.657 for the 13.0% (high sensitivity) and 0.765/0.833 for the 17.8% (well-balanced) cutoffs. In the validation test set, the AUC was also very high (0.915), the sensitivity/specificity were 0.870/0.875 for 13.0% and 0.565/0.958 for 17.8%. Using the diagnostic tree constructed by an objective algorithm, the diagnostic accuracy of the invasiveness of colorectal cancer was 91.3% for the training set and 85.1% for the test set. Our results suggest that analysis of the methylation of DNA in mucosal wash fluid may be a good molecular marker for predicting the invasiveness of colorectal tumors.

Development of a web-based CT dose calculator: WAZA-ARI

A web-based computed tomography (CT) dose calculation system (WAZA-ARI) is being developed based on the modern techniques for the radiation transport simulation and for software implementation. Dose coefficients were calculated in a voxel-type Japanese adult male phantom (JM phantom), using the Particle and Heavy Ion Transport code System. In the Monte Carlo simulation, the phantom was irradiated with a 5-mm-thick, fan-shaped photon beam rotating in a plane normal to the body axis. The dose coefficients were integrated into the system, which runs as Java servlets within Apache Tomcat. Output of WAZA-ARI for GE LightSpeed 16 was compared with the dose values calculated similarly using MIRD and ICRP Adult Male phantoms. There are some differences due to the phantom configuration, demonstrating the significance of the dose calculation with appropriate phantoms. While the dose coefficients are currently available only for limited CT scanner models and scanning options, WAZA-ARI will be a useful tool in clinical practice when development is finalised.

Gimeracil, an inhibitor of dihydropyrimidine dehydrogenase, inhibits the early step in homologous recombination

Gimeracil (5-chloro-2, 4-dihydroxypyridine) is an inhibitor of dihydropyrimidine dehydrogenase (DPYD), which degrades pyrimidine including 5-fluorouracil in the blood. Gimeracil was originally added to an oral fluoropyrimidine derivative S-1 to yield prolonged 5-fluorouracil concentrations in serum and tumor tissues. We have already reported that gimeracil had radiosensitizing effects by partially inhibiting homologous recombination (HR) in the repair of DNA double strand breaks. We investigated the mechanisms of gimeracil radiosensitization. Comet assay and radiation-induced focus formation of various kinds of proteins involved in HR was carried out. siRNA for DPYD were transfected to HeLa cells to investigate the target protein for radiosensitization with gimeracil. SCneo assay was carried out to examine whether DPYD depletion by siRNA inhibited HR repair of DNA double strand breaks. Tail moments in neutral comet assay increased in gimeracil-treated cells. Gimeracil restrained the formation of foci of Rad51 and replication protein A (RPA), whereas it increased the number of foci of Nbs1, Mre11, Rad50, and FancD2. When HeLa cells were transfected with the DPYD siRNA before irradiation, the cells became more radiosensitive. The degree of radiosensitization by transfection of DPYD siRNA was similar to that of gimeracil. Gimeracil did not sensitize DPYD-depleted cells. Depletion of DPYD by siRNA significantly reduced the frequency of neopositive clones in SCneo assay. Gimeracil partially inhibits the early step in HR. It was found that DPYD is the target protein for radiosensitization by gimeracil. The inhibitors of DPYD, such as gimeracil, could enhance the efficacy of radiotherapy through partial suppression of HR-mediated DNA repair.

Genome-wide profiling of chromatin signatures reveals epigenetic regulation of MicroRNA genes in colorectal cancer

Altered expression of microRNAs (miRNA) occurs commonly in human cancer, but the mechanisms are generally poorly understood. In this study, we examined the contribution of epigenetic mechanisms to miRNA dysregulation in colorectal cancer by carrying out high-resolution ChIP-seq. Specifically, we conducted genome-wide profiling of trimethylated histone H3 lysine 4 (H3K4me3), trimethylated histone H3 lysine 27 (H3K27me3), and dimethylated histone H3 lysine 79 (H3K79me2) in colorectal cancer cell lines. Combining miRNA expression profiles with chromatin signatures enabled us to predict the active promoters of 233 miRNAs encoded in 174 putative primary transcription units. By then comparing miRNA expression and histone modification before and after DNA demethylation, we identified 47 miRNAs encoded in 37 primary transcription units as potential targets of epigenetic silencing. The promoters of 22 transcription units were associated with CpG islands (CGI), all of which were hypermethylated in colorectal cancer cells. DNA demethylation led to increased H3K4me3 marking at silenced miRNA genes, whereas no restoration of H3K79me2 was detected in CGI-methylated miRNA genes. DNA demethylation also led to upregulation of H3K4me3 and H3K27me3 in a number of CGI-methylated miRNA genes. Among the miRNAs we found to be dysregulated, many of which are implicated in human cancer, miR-1-1 was methylated frequently in early and advanced colorectal cancer in which it may act as a tumor suppressor. Our findings offer insight into the association between chromatin signatures and miRNA dysregulation in cancer, and they also suggest that miRNA reexpression may contribute to the effects of epigenetic therapy.

Estimation of the number of CT procedures based on a nationwide survey in Japan

In 2007, a nationwide survey was conducted to determine the frequency of CT procedures in Japan in order to compare the current use of CT among developed countries. The frequency of adult and pediatric CT scans was estimated using a model based on the results of the survey. Survey questionnaires were sent to 2,266 CT facilities: 1,068 government hospitals and 1,198 other hospitals and non-hospital medical centers. The questionnaire requested information including the number of beds, outpatients per day, type of CT scanner, various body regions scanned, and the number of scans performed. The results of the study indicate that the number of CT procedures was closely correlated with the number of hospital beds. The authors estimate that approximately 20.5 million procedures were performed in 2005 and 21.2 million in 2006. The number of pediatric CT procedures was calculated by multiplying the total number of CT procedures by the estimated fraction of pediatric (0-15 y) CT procedures. Annual pediatric CT procedures were estimated to have been approximately 580,000 in 2005 and 600,000 in 2006. The present study indicates that the number of procedures per thousand of population, 166 for total CT and 32-34 for pediatric CT, is lower in Japan than in the U.S.

Methylation-associated silencing of microRNA-34b/c in gastric cancer and its involvement in an epigenetic field defect

Altered expression of microRNA (miRNA) is strongly implicated in cancer, and recent studies have shown that the silencing of some miRNAs is associated with CpG island hypermethylation. To identify epigenetically silenced miRNAs in gastric cancer (GC), we screened for miRNAs induced by treatment with 5-aza-2'-deoxycytidine and 4-phenylbutyrate. We found that miR-34b and miR-34c are epigenetically silenced in GC and that their downregulation is associated with hypermethylation of the neighboring CpG island. Methylation of the miR-34b/c CpG island was frequently observed in GC cell lines (13/13, 100%) but not in normal gastric mucosa from Helicobacter pylori-negative healthy individuals. Transfection of a precursor of miR-34b and miR-34c into GC cells induced growth suppression and dramatically changed the gene expression profile. Methylation of miR-34b/c was found in a majority of primary GC specimens (83/118, 70%). Notably, analysis of non-cancerous gastric mucosae from GC patients (n = 109) and healthy individuals (n = 85) revealed that methylation levels are higher in gastric mucosae from patients with multiple GC than in mucosae from patients with single GC (27.3 versus 20.8%; P < 0.001) or mucosae from H. pylori-positive healthy individuals (27.3 versus 20.7%; P < 0.001). These results suggest that miR-34b and miR-34c are novel tumor suppressors frequently silenced by DNA methylation in GC, that methylation of miR-34b/c is involved in an epigenetic field defect and that the methylation might be a predictive marker of GC risk.

ICRP Publication 111 - Application of the Commission's recommendations to the protection of people living in long-term contaminated areas after a nuclear accident or a radiation emergency

In this report, the Commission provides guidance for the protection of people living in long-term contaminated areas resulting from either a nuclear accident or a radiation emergency. The report considers the effects of such events on the affected population. This includes the pathways of human exposure, the types of exposed populations, and the characteristics of exposures. Although the focus is on radiation protection considerations, the report also recognises the complexity of post-accident situations, which cannot be managed without addressing all the affected domains of daily life, i.e. environmental, health, economic, social, psychological, cultural, ethical, political, etc. The report explains how the 2007 Recommendations apply to this type of existing exposure situation, including consideration of the justification and optimisation of protection strategies, and the introduction and application of a reference level to drive the optimisation process. The report also considers practical aspects of the implementation of protection strategies, both by authorities and the affected population. It emphasises the effectiveness of directly involving the affected population and local professionals in the management of the situation, and the responsibility of authorities at both national and local levels to create the conditions and provide the means favouring the involvement and empowerment of the population. The role of radiation monitoring, health surveillance, and the management of contaminated foodstuffs and other commodities is described in this perspective. The Annex summarises past experience of longterm contaminated areas resulting from radiation emergencies and nuclear accidents, including radiological criteria followed in carrying out remediation measures.