Nanoliposomal irinotecan with fluorouracil and folinic acid, FOLFIRINOX, and S-1 as second-line treatment for unresectable pancreatic cancer after gemcitabine/nab-paclitaxel.

This study aimed to compare second-line treatment outcomes for patients with unresectable pancreatic cancer previously treated with gemcitabine plus nab-paclitaxel (GnP) therapy. We conducted an integrated analysis of two retrospective studies included 318 patients receiving nanoliposomal irinotecan + 5-fluorouracil/folinic acid (NFF) (n = 102), S-1 (n = 57), or FOLFIRINOX (n = 14) as second-line treatment. Median overall survival (OS) in the NFF group was 9.08 months, significantly better than S-1 (4.90 months, P = 0.002). FOLFIRINOX had a median OS of 4.77 months, not statistically different from NFF. Subgroup analyses of OS indicated NFF was generally superior, however, a statistical interaction was observed between the treatment regimen in serum Alb < 3.5 g/dL (P = 0.042) and serum CRP ≥ 0.3 mg/dL (P = 0.006). Median progression-free survival (PFS) was 2.93 months for NFF, significantly better than S-1 (2.53 months, P = 0.024), while FOLFIRINOX had a comparable PFS (3.04 months, P = 0.948). Multivariate analysis identified the serum CRP, serum CA19-9, duration of first-line GnP therapy, and use (yes/no) of S-1 for second-line treatment as independent predictors for OS. This study concludes that second-line NFF therapy demonstrated a more favorable OS compared to S-1 therapy, however, it is still important to consider the patient background characteristics while selecting the most appropriate treatment.

A multicenter retrospective observational NAPOLEON2 study of nanoliposomal irinotecan with fluorouracil and folinic acid in patients with unresectable pancreatic cancer.

Nanoliposomal irinotecan with fluorouracil and folinic acid (NFF) is a standard regimen after gemcitabine-based therapy for patients with unresectable or recurrent pancreatic cancer. However, there are limited clinical data on its efficacy and safety in the real-world. We therefore initiated a retrospective and prospective observational study (NAPOLEON-2). The results of the retrospective part were reported herein. In this retrospective study, we evaluated 161 consecutive patients who received NFF as second-or-later-line regimen. The main endpoint was overall survival (OS), and the other endpoints were response rate, disease control rate, progression-free survival (PFS), dose intensity, and adverse events (AEs). The median age was 67 years (range, 38-85 years). The median OS and PFS were 8.1 and 3.4 months, respectively. The objective response and disease control rates were 5% and 52%, respectively. The median relative dose intensity was 81.6% for nanoliposomal irinotecan and 82.9% for fluorouracil. Grade 3 or 4 hematological and nonhematological AEs occurred in 47 and 42 patients, respectively. Common grade 3 or 4 AEs included neutropenia (24%), anorexia (12%), and leukocytopenia (12%). Subanalysis of patients treated with second-line and third-or-later-line demonstrated no statistical significant difference in OS (7.6 months vs. 9.1 months, respectively; hazard ratio, 0.92; 95% confidence interval, 0.64-1.35; p = 0.68). In conclusion, NFF has acceptable efficacy and safety profile even in real-world clinical settings. The prospective study is in progress to validate these findings.

[A Case of Clostridium difficile Enteritis with Ileostomy for Rectal Cancer Surgery].

A 74-year-old male presenting with bloody stools was diagnosed with advanced rectal cancer. He underwent robot- assisted low anterior resection and temporary ileostomy. Cefmetazole(CMZ)was administered during surgery and on postoperative day(POD)1. His postoperative course was generally good. On POD8, he developed abdominal fullness, vomiting, renal dysfunction, and hyperkalemia. Plain CT revealed small bowel ileus and outlet obstruction with ileostomy was suspected. A nasogastric tube was placed in the stomach, and a balloon catheter was inserted from the ileostomy to the oral side of the ileum. The patient went into shock on the same day and was transferred to a high-care unit. Contrast-enhanced CT indicated pneumatosis intestinalis of the small bowel and portal venous gas. However, the wall of the small bowel was enhanced, so the patient was observed carefully without attempting an operation. The patient's condition improved with systemic management. On POD10, a stool culture from the ileostomy tested positive for CD toxin. Clostridium difficile enteritis(CDE)was diagnosed. The condition improved with systemic control. On POD52, paralytic ileus recurred, and his stool tested positive for the CD toxin again. The ileus improved with conservative treatment. On POD70, the patient was transferred to the hospital for rehabilitation. We report a case of CDE with ileostomy for rectal cancer surgery.

OX40 and LAG3 are associated with better prognosis in advanced gastric cancer patients treated with anti-programmed death-1 antibody.

BACKGROUND: Anti-PD-1 monoclonal antibody, nivolumab, has shown efficacy for advanced gastric cancer (AGC). However, the specific immune cell subsets predominantly activated during the period of anti-PD-1 therapy for AGC have not been clarified. METHODS: Peripheral blood of 30 AGC patients treated with nivolumab was prospectively obtained before the initial and second administrations and at the time of progressive disease (PD). The proportions of immune cell subsets and the serum concentrations of cytokines were systematically analysed by flow cytometry. Associations of subsets and serum cytokines with therapeutic effects were evaluated. RESULTS: After the initial administration, significant increases in activated central/effector memory, activated effector T cells, and activated T-helper 1 subsets were observed. At the time of PD, activated regulatory T cells, LAG3-positive CD4+/CD8+ T cells, and TIM3-positive CD4+/CD8+ T cells increased significantly. Significant positive correlations were shown between progression-free survival and proportions of LAG3-positive CD4+/CD8+ T cells and of OX40-positive CD4+/CD8+ T cells (log-rank p = 0.0008, 0.0003, 0.0035 and 0.0040). CONCLUSIONS: Nivolumab therapy enhances activation of central/effector memory and effector subsets of CD4+/CD8+ T cells. The expression levels of LAG-3 and OX40 on T cells correlated with the efficacy of nivolumab therapy and could be reasonable biomarkers for anti-PD-1 therapy.

Irinotecan monotherapy as third-line or later treatment in advanced gastric cancer.

BACKGROUND: Patients with advanced gastric cancer (AGC) are often treated with irinotecan monotherapy as salvage-line therapy. However, the survival benefit of this therapy remains to be elucidated. METHODS: Medical records of AGC patients who were treated with irinotecan monotherapy as salvage-line treatment in six institutions from 2007 to 2014 were reviewed. RESULTS: A total of 146 patients had prior fluoropyrimidine and taxane therapies, and 75.3% had prior platinum therapy. The median age was 66 (range 27-81) years, and 102 males (69.9%) were included. Performance status (PS) was 0/1/2/3 in 53/70/19/4 patients. Eighty-nine patients (61.0%) had two or more metastatic sites. Irinotecan monotherapy as 3rd-/4th-line therapy was performed in 135/11 (92.5%/7.5%). The median number of administrations was 4 (range 1-62). Forty-six patients (31.5%) required initial dose reduction at the physician's discretion. The overall response rate was 6.8%, and the disease control rate was 43.1%. The median PFS was 3.19 months [95% confidence interval (CI) 2.30-4.08 months], and the median OS was 6.61 months (95% CI 5.94-7.28 months). Grade 3/4 adverse events were hematological toxicity (46 patients, 31.5%) and non-hematological toxicity (50 patients, 34.2%). Hospitalization due to adverse events was required in 31 patients (21.2%). Patients with relative dose intensity (RDI) less than 80% showed similar survival to those with RDI 80% or higher. CONCLUSIONS: Irinotecan monotherapy was relatively safely performed as salvage-line treatment for AGC in Japanese clinical practice. Careful patient selection and intensive modification of the dose of irinotecan might possibly be associated with favorable survival.

Anti-Epidermal Growth Factor Receptor Antibody Readministration in Chemorefractory Metastatic Colorectal Cancer.

BACKGROUND/AIM: Readministration of anti-epidermal growth factor receptor (EGFR) antibody for metastatic colorectal cancer (mCRC) after disease progression remains to be determined. PATIENTS AND METHODS: Readministration of anti-EGFR antibody in mCRC patients previously refractory to anti-EGFR antibody was prospectively observed. RESULTS: A total of thirteen patients with a median age of 60-years old and an Eastern Cooperative Oncology Group (ECOG) performance status 0 or 1, were enrolled. The median number of previous chemotherapies was 3 (range 2-5). Prior anti-EGFR antibody in combination with cytotoxic drugs was administered in 12 patients. Anti-EGFR antibody readministration regimens were cetuximab/panitumumab plus capecitabine/S-1 (seven patients), panitumumab plus FOLFOX (three patients), cetuximab plus irinotecan (two patients), and panitumumab monotherapy (one patient). Seven patients showed stable disease following readministration and six patients showed progressive disease. The median overall survival (OS) following readministration was 228 days and the median PFS was 102 days. Patients with intervals longer than 90 days between anti-EGFR therapies exhibited more favorable survival than those with intervals shorter than 90 days. Switching of anti-EGFR antibody between treatments was observed to contribute survival. CONCLUSION: Anti-EGFR antibody readministration could show a modest survival benefit in mCRC patients, with the length of therapy interval and switching of antibody being important contributory factors.

Early tumor shrinkage indicates a favorable response to bevacizumab-based first-line chemotherapy for metastatic colorectal cancer.

A close correlation between early tumor shrinkage (ETS) and overall survival (OS) has been shown in antiepidermal growth factor receptor antibody-based chemotherapies for metastatic colorectal cancer (mCRC), but the clinical impact of ETS in bevacizumab-based chemotherapy has not been adequately clarified. Clinical data of mCRC patients who started initial chemotherapy without antiepidermal growth factor receptor antibody from 2005 to 2010 were retrospectively evaluated. The relative change in tumor size after 8 weeks of chemotherapy expected from the first image assessment [estimated ETS (EETS)] and the relative change in the tumor size at the nadir compared with the baseline [depth of response (DPR)] were examined. Seventy-three patients were enrolled and 61 patients were evaluable for survival by simple regression analysis. Bevacizumab-based chemotherapies were administered to 40 (66%) patients. The median EETS, DPR, progression-free survival, and OS were 16.1%, 27.2%, 8.0 months, and 19.5 months, respectively. Progression-free survival showed a positive correlation with OS (R=0.429), whereas EETS and DPR were less correlated with OS (R=0.0682, 0.186). EETS was well correlated with DPR (R=0.659). Patients with EETS greater than 16.12% were predicted to achieve tumor shrinkage of more than 30% at the maximum response. EETS in bevacizumab-treated mCRC showed a close correlation with DPR, which suggested that EETS might be useful, indicating a favorable response in treatment with bevacizumab-based chemotherapy.

LJM716 in Japanese patients with head and neck squamous cell carcinoma or HER2-overexpressing breast or gastric cancer.

PURPOSE: Human epidermal growth factor receptor 3 (HER3) has been identified as an important component of many receptor tyrosine kinase-driven cancers. LJM716 is a human IgG monoclonal antibody that binds HER3, trapping it in an inactive conformation. In this study, a phase I dose escalation was performed with a primary objective to establish the maximum tolerated dose and/or the recommended dose of LJM716 in Japanese patients with selected advanced solid tumors. Secondary objectives included the evaluation of the safety and tolerability, preliminary antitumor activity, and pharmacokinetics of LJM716 in Japanese patients. METHODS: LJM716 was administered intravenously at doses of 10, 20, or 40 mg/kg once weekly, in 28-day cycles, to 12 patients with HER2-amplified breast cancer or gastric cancer, or with esophageal squamous cell carcinoma or squamous cell carcinoma of the head and neck, regardless of HER2 status. RESULTS: The maximum tolerated dose was not reached, and the recommended dose was established at 40 mg/kg. No dose-limiting toxicities were observed in the first cycle. The most frequently reported adverse events were diarrhea, fatigue, stomatitis, pyrexia, and paronychia. One unconfirmed partial response was observed in a patient with breast cancer, and 50% of the patients achieved stable disease as the best overall response. Exposure increased with ascending dose, and half-life was estimated to be 11-14 days. No anti-LJM716 antibodies were detected. CONCLUSIONS: LJM716 was well tolerated in Japanese patients, and a degree of tumor shrinkage was observed. CLINICAL TRIAL INFORMATION: ClinicalTrials.gov NCT01911936.

Favorable control of advanced colon adenocarcinoma with severe bone marrow metastasis: A case report.

Colorectal cancer (CRC) has a propensity to metastasize to the liver, lungs and regional abdominal lymph nodes, but rarely to the bone marrow. A 60-year-old man presented to the National Hospital Organization Kyushu Cancer Center with a 4-week history of persistent lower back pain, anorexia and difficulty defecating. Complete blood count revealed severe thrombocytopenia and erythroblastosis, suggesting a hematological malignancy. However, the bone marrow examination demonstrated involvement by a moderately to poorly differentiated adenocarcinoma, but no hematopoietic abnormalities. A computed tomography scan revealed thickening of the wall of the sigmoid colon, with para-aortic, hilar, mediastinal and supraclavicular lymphadenopathy. The patient was thus diagnosed with sigmoid colon adenocarcinoma with lymph node and bone marrow metastasis. Modified FOLFOX6 was promptly initiated, with concurrent therapy for disseminated intravascular coagulation (DIC). An increased number of thrombocytes was observed on day 6. After 3 cycles of treatment, the patient recovered from DIC and the levels of serum carcinoembryonic antigen and cytokeratin 19 fragment were decreased. Tumor biopsy during colonoscopy following recovery from DIC demonstrated poorly differentiated adenocarcinoma with mucin production, without mutations in the RAS, BRAF or PIK3CA genes, and a cytokeratin (CK) 7-negative, CK20-positive phenotype. The patient has been treated with chemotherapy for 150 days without disease progression. However, the efficacy of chemotherapy for rarely encountered bone marrow metastasis from CRC is poor. The present case was favorably maintained on chemotherapy and survived for 10 months.

SET7/9 Enzyme Regulates Cytokine-induced Expression of Inducible Nitric-oxide Synthase through Methylation of Lysine 4 at Histone 3 in the Islet ß Cell.

SET7/9 is an enzyme that methylates histone 3 at lysine 4 (H3K4) to maintain euchromatin architecture. Although SET7/9 is enriched in islets and contributes to the transactivation of ß cell-specific genes, including Ins1 and Slc2a, SET7/9 has also been reported to bind the p65 subunit of nuclear factor κB in non-ß cells and modify its transcriptional activity. Given that inflammation is a central component of ß cell dysfunction in Type 1 and Type 2 diabetes, the aim of this study was to elucidate the role of SET7/9 in proinflammatory cytokine signaling in ß cells. To induce inflammation, ßTC3 insulinoma cells were treated with IL-1ß, TNF-α, and IFN-γ. Cytokine treatment led to increased expression of inducible nitric-oxide synthase, which was attenuated by the diminution of SET7/9 using RNA interference. Consistent with previous reports, SET7/9 was co-immunoprecipitated with p65 and underwent cytosolic to nuclear translocation in response to cytokines. ChIP analysis demonstrated augmented H3K4 mono- and dimethylation of the proximal Nos2 promoter with cytokine exposure. SET7/9 was found to occupy this same region, whereas SET7/9 knockdown attenuated cytokine-induced histone methylation of the Nos2 gene. To test this relationship further, islets were isolated from SET7/9-deficient and wild-type mice and treated with IL-1ß, TNF-α, and IFN-γ. Cytokine-induced Nos2 expression was reduced in the islets from SET7/9 knock-out mice. Together, our findings suggest that SET7/9 contributes to Nos2 transcription and proinflammatory cytokine signaling in the pancreatic ß cell through activating histone modifications.

Reduced dose of salvage-line regorafenib monotherapy for metastatic colorectal cancer in Japan.

BACKGROUND: Salvage-line regorafenib monotherapy exhibited a marked survival benefit for metastatic colorectal cancer (mCRC). However, the toxicity of this regimen has resulted in the clinical use of a reduced dose of regorafenib. PATIENTS AND METHODS: Thirty-two Japanese mCRC patients (median age=61 years) who had been treated with regorafenib were retrospectively examined. RESULTS: Best objective response rate was 0% and stable disease (SD) was 31%. Median progression-free survival was 81 days and median overall survival was 233 days. Adverse events of any grade were observed in all patients: 17 (53%) patients suffered grade 3 or 4 adverse events including fatigue (13%), anorexia (13%), hand-foot skin reaction (22%) and elevations of alanine aminotransferase/aspartate aminotransferase (19%/16%). One patient with grade 5 liver dysfunction was identified (3%). Twenty-nine (91%) patients required treatment dose reduction or a delay in treatment. The relative dose intensity was 59%. Regorafenib treatments were terminated because of disease progression (59%) or adverse events (34%). CONCLUSION: Despite a decrease in the intensity of regorafenib treatment, because of severe adverse events, a fairly favorable efficacy was achieved in Japanese patients.

Spontaneous development of hepatocellular carcinoma with cancer stem cell properties in PR-SET7-deficient livers.

PR-SET7-mediated histone 4 lysine 20 methylation has been implicated in mitotic condensation, DNA damage response and replication licensing. Here, we show that PR-SET7 function in the liver is pivotal for maintaining genome integrity. Hepatocyte-specific deletion of PR-SET7 in mouse embryos resulted in G2 phase arrest followed by massive cell death and defect in liver organogenesis. Inactivation at postnatal stages caused cell duplication-dependent hepatocyte necrosis, accompanied by inflammation, fibrosis and compensatory growth induction of neighboring hepatocytes and resident ductal progenitor cells. Prolonged necrotic regenerative cycles coupled with oncogenic STAT3 activation led to the spontaneous development of hepatic tumors composed of cells with cancer stem cell characteristics. These include a capacity to self-renew in culture or in xenografts and the ability to differentiate to phenotypically distinct hepatic cells. Hepatocellular carcinoma in PR-SET7-deficient mice displays a cancer stem cell gene signature specified by the co-expression of ductal progenitor markers and oncofetal genes.

Pemetrexed combined with platinum-based chemotherapy for advanced malignant peritoneal mesothelioma: retrospective analysis of six cases.

BACKGROUND: Malignant peritoneal mesothelioma (PM) is an extremely rare disease. Pemetrexed and platinum have been used for advanced PM following malignant pleural mesothelioma (PLM). Because PM differs considerably from PLM in clinical features, the efficacy and safety of these therapies have yet to be established. PATIENTS AND METHODS: Six Japanese patients with PM who had been treated with pemetrexed-based chemotherapy in four Institutions were retrospectively identified. Treatment response, progression-free survival, and overall survival were examined. Toxicities of therapy were also evaluated. RESULTS: Three patients with mild ascites achieved clinical benefits (one with partial response and two with stable disease). Treatments with reduced cisplatin or carboplatin for patients with massive ascites were safely performed. Median PFS and OS were 7.2 and 13.1 months, respectively. Grade 3 hematological toxicities appeared in two patients with massive ascites. CONCLUSION: Selection of chemotherapy based on the patient's condition, such as ascites, might be important for advanced PM.

The role of PR-Set7 in replication licensing depends on Suv4-20h.

PR-Set7 is the sole monomethyltransferase responsible for H4K20 monomethylation (H4K20me1) that is the substrate for further methylation by Suv4-20h1/h2. PR-Set7 is required for proper cell cycle progression and is subject to degradation by the CRL4(Cdt2) ubiquitin ligase complex as a function of the cell cycle and DNA damage. This report demonstrates that PR-Set7 is an important downstream effector of CRL4(Cdt2) function during origin of DNA replication licensing, dependent on Suv4-20h1/2 activity. Aberrant rereplication correlates with decreased levels of H4K20me1 and increased levels of H4K20 trimethylation (H4K20me3). Expression of a degradation-resistant PR-Set7 mutant in the mouse embryo that is normally devoid of Suv4-20 does not compromise development or cell cycle progression unless Suv4-20h is coexpressed. PR-Set7 targeting to an artificial locus results in recruitment of the origin recognition complex (ORC) in a manner dependent on Suv4-20h and H4K20me3. Consistent with this, H4K20 methylation status plays a direct role in recruiting ORC through the binding properties of ORC1 and ORCA/LRWD1. Thus, coordinating the status of H4K20 methylation is pivotal for the proper selection of DNA replication origins in higher eukaryotes.

PR-Set7 and H4K20me1: at the crossroads of genome integrity, cell cycle, chromosome condensation, and transcription.

Histone post-translational modifications impact many aspects of chromatin and nuclear function. Histone H4 Lys 20 methylation (H4K20me) has been implicated in regulating diverse processes ranging from the DNA damage response, mitotic condensation, and DNA replication to gene regulation. PR-Set7/Set8/KMT5a is the sole enzyme that catalyzes monomethylation of H4K20 (H4K20me1). It is required for maintenance of all levels of H4K20me, and, importantly, loss of PR-Set7 is catastrophic for the earliest stages of mouse embryonic development. These findings have placed PR-Set7, H4K20me, and proteins that recognize this modification as central nodes of many important pathways. In this review, we discuss the mechanisms required for regulation of PR-Set7 and H4K20me1 levels and attempt to unravel the many functions attributed to these proteins.

The histone methyltransferase Setd8 acts in concert with c-Myc and is required to maintain skin.

Setd8/PR-Set7/KMT5a-dependent mono-methylation of histone H4 at lysine 20 is essential for mitosis of cultured cells; yet, the functional roles of Setd8 in complex mammalian tissues are unknown. We use skin as a model system to explore how Setd8 may regulate cell division in vivo. Deletion of Setd8 in undifferentiated layers of the mouse epidermis impaired both proliferation and differentiation processes. Long-lived epidermal progenitor cells are lost in the absence of Setd8, leading to an irreversible loss of sebaceous glands and interfollicular epidermis. We show that Setd8 is a transcriptional target of c-Myc and an essential mediator of Myc-induced epidermal differentiation. Deletion of Setd8 in c-Myc-overexpressing skin blocks proliferation and differentiation and causes apoptosis. Increased apoptosis may be explained by our discovery that p63, an essential transcription factor for epidermal commitment is lost, while p53 is gained upon removal of Setd8. Both overexpression of p63 and deletion of p53 rescue Setd8-induced apoptosis. Thus, Setd8 is a crucial inhibitor of apoptosis in skin and its activity is essential for epidermal stem cell survival, proliferation and differentiation.

Regulation of the histone H4 monomethylase PR-Set7 by CRL4(Cdt2)-mediated PCNA-dependent degradation during DNA damage.

The histone methyltransferase PR-Set7/Set8 is the sole enzyme that catalyzes monomethylation of histone H4 at K20 (H4K20me1). Previous reports document disparate evidence regarding PR-Set7 expression during the cell cycle, the biological relevance of PR-Set7 interaction with PCNA, and its role in the cell. We find that PR-Set7 is indeed undetectable during S phase and instead is detected during late G2, mitosis, and early G1. PR-Set7 is transiently recruited to laser-induced DNA damage sites through its interaction with PCNA, after which 53BP1 is recruited dependent on PR-Set7 catalytic activity. During the DNA damage response, PR-Set7 interaction with PCNA through a specialized "PIP degron" domain targets it for PCNA-coupled CRL4(Cdt2)-dependent proteolysis. PR-Set7 mutant in its "PIP degron" is now detectable during S phase, during which the mutant protein accumulates. Outside the chromatin context, Skp2 promotes PR-Set7 degradation as well. These findings demonstrate a stringent spatiotemporal control of PR-Set7 that is essential for preserving the genomic integrity of mammalian cells.

Monomethylation of histone H4-lysine 20 is involved in chromosome structure and stability and is essential for mouse development.

PR-Set7/Set8/KMT5A is the sole enzyme known to catalyze monomethylation of histone H4 lysine 20 (H4K20) and is present only in multicellular organisms that compact a large fraction of their DNA. We found that mouse embryos that are homozygous null mutants for the gene PR-Set7 display early embryonic lethality prior to the eight-cell stage. Death was due to the absence of PR-Set7 catalytic activity, since microinjection of the wild type, but not a catalytically inactive version, into two-cell embryos rescued the phenotype. A lack of PR-Set7 activity resulted not only in depletion of H4K20me1 but also in reduced levels of the H4K20me2/3 marks catalyzed by the Suv4-20h1/h2 enzymes, implying that H4K20me1 may be essential for the function of these enzymes to ensure the dimethylated and trimethylated states. Embryonic stem cells that were inducibly deleted for PR-Set7 passed through an initial G(2)/M phase, but the progeny were defective at the subsequent S and G(2)/M phases, exhibiting a delay in their cell cycle, accumulation at G(2)/M, massive DNA damage, and improper mitotic chromosome condensation. Cell cycle analysis after synchronization indicated that the defects were a consequence of decreased H4K20me1 due to the absence of PR-Set7. Most importantly, the lack of H4K20me1 also resulted in defects in chromosome condensation in interphase nuclei. These results demonstrate the critical role of H4K20 monomethylation in mammals in a developmental context.

The GT to GC single nucleotide polymorphism at the beginning of an alternative exon 2C of human MTH1 gene confers an amino terminal extension that functions as a mitochondrial targeting signal.

Human MTH1 protein hydrolyzes oxidized purine nucleotides 8-oxo-2'-deoxyguanosine triphosphate (8-oxo-dGTP), 2-OH-dATP or their ribo-forms to their monophosphates, thus minimizing replicational and transcriptional errors both in the nuclei and mitochondria. MTH1 suppresses mitochondrial dysfunction and cell death caused by H(2)O(2). Furthermore, MTH1 suppresses the transient increase in 8-oxoguanine in mitochondrial DNA in the dopaminergic nerve terminals in mouse striatum after 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine administration, and it protects the nerve terminals. We previously reported that a novel MTH1 allele with a single nucleotide polymorphism (SNP) in its exon 2c segment encodes the fourth MTH1 isoform, namely, MTH1a (p26), in addition to the three known isoforms, MTH1b (p22), c (p21), and d (p18). Another SNP located in exon 4 of the MTH1 gene, which is closely linked to the SNP in exon 2c, substitutes the Val83 residue in MTH1d with Met83. We herein show that all MTH1 isoforms efficiently hydrolyzed 2-OH-dATP and 8-oxo-dGTP. The amino terminal region of MTH1a functioned as a mitochondrial targeting signal when it was expressed in the HeLa cells as a fusion protein with enhanced green fluorescent protein. The cellular fractionation revealed that MTH1a(Met83) was localized in the mitochondria to the same extent as was MTH1d(Val83). However, the mitochondrial translocation of MTH1d(Met83) was less efficient than that of MTH1d(Val83).

Microarray analysis of the genes induced by tetracycline-regulated expression of NDRF/NeuroD2 in P19 cells.

NeuroD-related factor (NDRF)/NeuroD2 is a basic helix-loop-helix (bHLH) protein that plays important roles in neuronal development. To elucidate the NDRF transcription network, we used mouse cDNA microarray analysis combined with a tetracycline-regulatable expression system in P19 embryonal carcinoma cells. Five genes were identified to be up-regulated in the presence of NDRF protein. RNA hybridization analysis confirmed that brain-lipid-binding protein (BLBP) and inhibitor of differentiation 1 (Id1) genes were among the five genes that were rapidly and significantly up-regulated after induction of NDRF. When a dominant negative form of NDRF protein was expressed during retinoic acid-induced neuronal differentiation of P19 cells, the BLBP gene, but not the Id1 gene, was potently repressed. Immunohistochemical analysis revealed that both NDRF and Id1 immunoreactivities were observed in some granule cells of the cerebellum in the postnatal period. These results suggest that NDRF or its related bHLH proteins may act upstream of these genes in a subset of developing neurons.