Head-to-head comparison of three chelates reveals DOTAGA promising for 225 Ac labeling of anti-FZD10 antibody OTSA101.

To select the most suitable chelate for 225 Ac radiolabeling of the anti-FZD10 antibody OTSA101, we directly compared three chelates: S-2-(4-isothiocyanatobenzyl)-1,4,7,10-tetraazacyclododecane tetraacetic acid (p-SCN-Bn-DOTA), 2,2',2″-(10-(1-carboxy-4-((4-isothiocyanatobenzyl)amino)-4-oxobutyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl) triacetic acid (p-SCN-Bn-DOTAGA), and 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid mono-N-hydroxysuccinimide ester (DO3A-NHS-ester). We evaluated the binding affinity of the chelate-conjugated OTSA101 antibodies, as well as the labeling efficiency and stability in murine serum of 225 Ac-labeled OTSA101 as in vitro properties. The biodistribution, intratumoral distribution, absorbed doses, and therapeutic effects of the chelate-conjugated OTSA101 antibodies were assessed in the synovial sarcoma mouse model SYO-1. Of the three conjugates, DOTAGA conjugation had the smallest impact on the binding affinity (p < 0.01). The labeling efficiencies of DOTAGA-OTSA101 and DO3A-OTSA101 were 1.8-fold higher than that of DOTA-OTSA101 (p < 0.01). The stabilities were similar between 225 Ac-labeled DOTA-OTSA101, DOTAGA-OTSA101, and DO3A-OTSA101in serum at 37 and 4°C. The dosimetric analysis based on the biodistribution revealed significantly higher tumor-absorbed doses by 225 Ac-labeled DOTA-OTSA101 and DOTAGA-OTSA101 compared with 225 Ac-DO3A-OTSA101 (p < 0.05). 225 Ac-DOTAGA-OTSA101 exhibited the highest tumor-to-bone marrow ratio, with bone marrow being the dose-limiting tissue. The therapeutic and adverse effects were not significantly different between the three conjugates. Our findings indicate that among the three evaluated chelates, DOTAGA appears to be the most promising chelate to produce 225 Ac-labeled OTSA101 with high binding affinity and high radiochemical yields while providing high absorbed doses to tumors and limited absorbed doses to bone marrow.

FZD10-targeted α-radioimmunotherapy with 225 Ac-labeled OTSA101 achieves complete remission in a synovial sarcoma model.

Synovial sarcomas are rare tumors arising in adolescents and young adults. The prognosis for advanced disease is poor, with an overall survival of 12-18 months. Frizzled homolog 10 (FZD10) is overexpressed in most synovial sarcomas, making it a promising therapeutic target. The results of a phase 1 trial of ß-radioimmunotherapy (RIT) with the 90 Y-labeled anti-FZD10 antibody OTSA101 revealed a need for improved efficacy. The present study evaluated the potential of α-RIT with OTSA101 labeled with the α-emitter 225 Ac. Competitive inhibition and cell binding assays showed that specific binding of 225 Ac-labeled OTSA101 to SYO-1 synovial sarcoma cells was comparable to that of the imaging agent 111 In-labeled OTSA101. Biodistribution studies showed high uptake in SYO-1 tumors and low uptake in normal organs, except for blood. Dosimetric studies showed that the biologically effective dose (BED) of 225 Ac-labeled OTSA101 for tumors was 7.8 Bd higher than that of 90 Y-labeled OTSA101. 90 Y- and 225 Ac-labeled OTSA101 decreased tumor volume and prolonged survival. 225 Ac-labeled OTSA101 achieved a complete response in 60% of mice, and no recurrence was observed. 225 Ac-labeled OTSA101 induced a larger amount of necrosis and apoptosis than 90 Y-labeled OTSA101, although the cell proliferation decrease was comparable. The BED for normal organs and tissues was tolerable; no treatment-related mortality or obvious toxicity, except for temporary body weight loss, was observed. 225 Ac-labeled OTSA101 provided a high BED for tumors and achieved a 60% complete response in the synovial sarcoma mouse model SYO-1. RIT with 225 Ac-labeled OTSA101 is a promising therapeutic option for synovial sarcoma.

The survival and proliferation of osteosarcoma cells are dependent on the mitochondrial BIG3-PHB2 complex formation.

Previous studies reported the critical role of the brefeldin A-inhibited guanine nucleotide exchange protein 3-prohibitin 2 (BIG3-PHB2) complex in modulating estrogen signaling activation in breast cancer cells, yet its pathophysiological roles in osteosarcoma (OS) cells remain elusive. Here, we report a novel function of BIG3-PHB2 in OS malignancy. BIG3-PHB2 complexes were localized mainly in mitochondria in OS cells, unlike in estrogen-dependent breast cancer cells. Depletion of endogenous BIG3 expression by small interfering RNA (siRNA) treatment led to significant inhibition of OS cell growth. Disruption of BIG3-PHB2 complex formation by treatment with specific peptide inhibitor also resulted in significant dose-dependent suppression of OS cell growth, migration, and invasion resulting from G2/M-phase arrest and in PARP cleavage, ultimately leading to PARP-1/apoptosis-inducing factor (AIF) pathway activation-dependent apoptosis in OS cells. Subsequent proteomic and bioinformatic pathway analyses revealed that disruption of the BIG3-PHB2 complex might lead to downregulation of inner mitochondrial membrane protein complex activity. Our findings indicate that the mitochondrial BIG3-PHB2 complex might regulate PARP-1/AIF pathway-dependent apoptosis during OS cell proliferation and progression and that disruption of this complex may be a promising therapeutic strategy for OS.

Functional genomics for breast cancer drug target discovery.

Breast cancer is a heterogeneous disease that develops through a multistep process via the accumulation of genetic/epigenetic alterations in various cancer-related genes. Current treatment options for breast cancer patients include surgery, radiotherapy, and chemotherapy including conventional cytotoxic and molecular-targeted anticancer drugs for each intrinsic subtype, such as endocrine therapy and antihuman epidermal growth factor receptor 2 (HER2) therapy. However, these therapies often fail to prevent recurrence and metastasis due to resistance. Overall, understanding the molecular mechanisms of breast carcinogenesis and progression will help to establish therapeutic modalities to improve treatment. The recent development of comprehensive omics technologies has led to the discovery of driver genes, including oncogenes and tumor-suppressor genes, contributing to the development of molecular-targeted anticancer drugs. Here, we review the development of anticancer drugs targeting cancer-specific functional therapeutic targets, namely, MELK (maternal embryonic leucine zipper kinase), TOPK (T-lymphokine-activated killer cell-originated protein kinase), and BIG3 (brefeldin A-inhibited guanine nucleotide-exchange protein 3), as identified through comprehensive breast cancer transcriptomics.

Significant association between high serum CCL5 levels and better disease-free survival of patients with early breast cancer.

Analysis of anticancer immunity aids in assessing the prognosis of patients with breast cancer. From 250 operated breast cancers, we focused on serum levels of C-C motif chemokine ligand 5 (CCL5), which is involved in cancer immune reactions. Serum levels of CCL5 were measured using a cytometric bead-based immunoassay kit and CCL5 expression in cancer cells was determined using immunohistochemical staining. In addition, mRNA in cancer and stromal cells was analyzed by microdissection and comparison with the public dataset. Disease-free survival (DFS) of patients with high CCL5 levels (cut-off, 13.87 ng/mL; n = 192) was significantly better than those with low CCL5 levels (n = 58; hazard ratio, 0.20; 95% confidence interval, 0.10-0.39; P < .0001). An improved overall survival was observed in patients with high CCL5 levels compared to those with low CCL5 levels (P = .024). On the contrary, high immunohistochemical expression of CCL5 in cancer cells was significantly associated with decreased DFS. As serum CCL5 levels did not correlate with CCL5 expression in cancer cells and the relative expression of mRNA CCL5 was elevated in stromal cells in relation to cancer cells, serum CCL5 might be derived not from cancer cells, but from stromal cells. Expression of CCL5 in serum, but not in cancer cells, might contribute to improved patient prognosis mediating through not only immune reaction, but through other mechanisms. Determination of circulating CCL5 levels could be useful for predicting patient prognosis.

Biophysical characterization of the breast cancer-related BIG3-PHB2 interaction: Effect of non-conserved loop region of BIG3 on the structure and the interaction.

Brefeldin A-inhibited guanine nucleotide-exchange protein 3 (BIG3) interacts with and inhibits the tumor suppressor function of prohibitin-2 (PHB2), and recent in vivo studies have demonstrated that the BIG3-PHB2 interaction is a promising target for breast cancer therapy. However, little biophysical characterization on BIG3 and its interaction with PHB2 has been reported. Here we compared the calculated 8-class secondary structure of the N-terminal domains of BIG family proteins and identified a loop region unique to BIG3. Our biophysical characterization demonstrated that this loop region significantly affects the colloidal and thermodynamic stability of BIG3 and the thermodynamic and kinetic profile of its interaction with PHB2. These results establish a model for the BIG3-PHB2 interaction and an entry for drug discovery for breast cancer.

Present status and future perspective of peptide-based vaccine therapy for urological cancer.

Use of peptide-based vaccines as therapeutics aims to elicit immune responses through antigenic epitopes derived from tumor antigens. Peptide-based vaccines are easily synthesized and lack significant side-effects when given in vivo. Peptide-based vaccine therapy against several cancers including urological cancers has made progress for several decades, but there is no worldwide approved peptide vaccine. Peptide vaccines were also shown to induce a high frequency of immune response in patients accompanied by clinical efficacy. These data are discussed in light of the recent progression of immunotherapy caused by the addition of immune checkpoint inhibitors thus providing a general picture of the potential therapeutic efficacy of peptide-based vaccines and their combination with other biological agents. In this review, we discuss the mechanism of the antitumor effect of peptide-based vaccine therapy, development of our peptide vaccine, recent clinical trials using peptide vaccines for urological cancers, and perspectives of peptide-based vaccine therapy.

α-particle therapy for synovial sarcoma in the mouse using an astatine-211-labeled antibody against frizzled homolog 10.

Synovial sarcoma (SS) is a rare yet refractory soft-tissue sarcoma that predominantly affects young adults. We show in a mouse model that radioimmunotherapy (RIT) with an α-particle emitting anti-Frizzled homolog 10 (FZD10) antibody, synthesized using the α-emitter radionuclide astatine-211 (211 At-OTSA101), suppresses the growth of SS xenografts more efficiently than the corresponding ß-particle emitting anti-FZD10 antibody conjugated with the ß-emitter yettrium-90 (90 Y-OTSA101). In biodistribution analysis, 211 At was increased in the SS xenografts but decreased in other tissues up to 1 day after injection as time proceeded, albeit with a relatively higher uptake in the stomach. Single 211 At-OTSA101 doses of 25 and 50 µCi significantly suppressed SS tumor growth in vivo, whereas a 50-µCi dose of 90 Y-OTSA101 was needed to achieve this. Importantly, 50 µCi of 211 At-OTSA101 suppressed tumor growth immediately after injection, whereas this effect required several days in the case of 90 Y-OTSA101. Both radiolabeled antibodies at the 50-µCi dosage level significantly prolonged survival. Histopathologically, severe cellular damage accompanied by massive cell death was evident in the SS xenografts at even 1 day after the 211 At-OTSA101 injection, but these effects were relatively milder with 90 Y-OTSA101 at the same timepoint, even though the absorbed doses were comparable (3.3 and 3.0 Gy, respectively). We conclude that α-particle RIT with 211 At-OTSA101 is a potential new therapeutic option for SS.

A first-in-human study investigating biodistribution, safety and recommended dose of a new radiolabeled MAb targeting FZD10 in metastatic synovial sarcoma patients.

BACKGROUND: Synovial Sarcomas (SS) are rare tumors occurring predominantly in adolescent and young adults with a dismal prognosis in advanced phases. We report a first-in-human phase I of monoclonal antibody (OTSA-101) targeting FZD10, overexpressed in most SS but not present in normal tissues, labelled with radioisotopes and used as a molecular vehicle to specifically deliver radiation to FZD10 expressing SS lesions. METHODS: Patients with progressive advanced SS were included. In the first step of this trial, OTSA-101 in vivo bio-distribution and lesions uptake were evaluated by repeated whole body planar and SPECT-CT scintigraphies from H1 till H144 after IV injection of 187 MBq of 111In-OTSA-101. A 2D dosimetry study also evaluated the liver absorbed dose when using 90Y-OTSA-101. In the second step, those patients with significant tumor uptake were randomized between 370 MBq (Arm A) and 1110 MBq (Arm B) of 90Y-OTSA-101 for radionuclide therapy. RESULTS: From January 2012 to June 2015, 20 pts. (median age 43 years [21-67]) with advanced SS were enrolled. Even though 111In-OTSA-101 liver uptake appeared to be intense, estimated absorbed liver dose was less than 20 Gy for each patient. Tracer intensity was greater than mediastinum in 10 patients consistent with sufficient tumor uptake to proceed to treatment with 90Y-OTSA-101: 8 were randomized (Arm A: 3 patients and Arm B: 5 patients) and 2 were not randomized due to worsening PS. The most common Grade ≥ 3 AEs were reversible hematological disorders, which were more frequent in Arm B. No objective response was observed. Best response was stable disease in 3/8 patients lasting up to 21 weeks for 1 patient. CONCLUSIONS: Radioimmunotherapy targeting FZD10 is feasible in SS patients as all patients presented at least one lesion with 111In-OTSA-101 uptake. Tumor uptake was heterogeneous but sufficient to select 50% of pts. for 90Y-OTSA-101 treatment. The recommended activity for further clinical investigations is 1110 MBq of 90Y-OTSA-101. However, because of hematological toxicity, less energetic particle emitter radioisopotes such as Lutetium 177 may be a better option to wider the therapeutic index. TRIAL REGISTRATION: The study was registered on the NCT01469975 website with a registration code NCT01469975 on November the third, 2011.

Protein kinase A inhibition facilitates the antitumor activity of xanthohumol, a valosin-containing protein inhibitor.

Xanthohumol (XN), a simple prenylated chalcone, can be isolated from hops and has the potential to be a cancer chemopreventive agent against several human tumor cell lines. We previously identified valosin-containing protein (VCP) as a target of XN; VCP can also play crucial roles in cancer progression and prognosis. Therefore, we investigated the molecular mechanisms governing the contribution of VCP to the antitumor activity of XN. Several human tumor cell lines were treated with XN to investigate which human tumor cell lines are sensitive to XN. Several cell lines exhibited high sensitivity to XN both in vitro and in vivo. shRNA screening and bioinformatics analysis identified that the inhibition of the adenylate cyclase (AC) pathway synergistically facilitated apoptosis induced by VCP inhibition. These results suggest that there is crosstalk between the AC pathway and VCP function, and targeting both VCP and the AC pathway is a potential chemotherapeutic strategy for a subset of tumor cells.

Effective induction of cytotoxic T cells recognizing an epitope peptide derived from hypoxia-inducible protein 2 (HIG2) in patients with metastatic renal cell carcinoma.

PURPOSE: Through genome-wide expression profile analysis, hypoxia-inducible protein 2 (HIG2) has previously been identified as an oncoprotein involved in development/progression of renal cell carcinoma (RCC). We subsequently identified a highly immunogenic HLA-A*0201/0206-restricted epitope peptide (HIG2-9-4) corresponding to a part of HIG2 and applied it as a therapeutic vaccine. We conducted a phase I clinical trial using the HIG2-9-4 peptide for patients with advanced RCC. MATERIALS AND METHODS: Nine patients having HLA-A*0201 or HLA-A*0206 with metastatic or unresectable RCC after failure of the cytokine and/or tyrosine kinase inhibitor therapies were enrolled in this study. The patients received subcutaneous administration of the peptide as an emulsion form with Montanide ISA-51 VG once a week in a dose-escalation manner (doses of 0.5, 1.0, or 3.0 mg/body, 3 patients for each dose). The primary endpoint was safety, and the secondary endpoints were immunological and clinical responses. RESULTS: Vaccinations with HIG2-9-4 peptide could be well tolerated without any serious systemic adverse events. Peptide-specific cytotoxic T lymphocyte (CTL) responses were detected in eight of the nine patients. Doses of 1.0 or 3.0 mg/body seemed to induce a CTL response better than did a dose of 0.5 mg/body, although the number of patients was too small to draw a firm conclusion. The disease control rate (stable disease for ≥4 months) was 77.8 %, and the median progression-free survival time was 10.3 months. CONCLUSIONS: HIG2-9-4 peptide vaccine treatment was tolerable and effectively induced peptide-specific CTLs in RCC patients. This novel peptide vaccine therapy for RCC is promising.

Therapeutic advances in BIG3-PHB2 inhibition targeting the crosstalk between estrogen and growth factors in breast cancer.

Our previous studies demonstrated that specific inhibition of the BIG3-PHB2 complex, which is a critical modulator in estrogen (E2) signaling, using ERAP, a dominant negative peptide inhibitor, leads to suppression of E2-dependent estrogen receptor (ER) alpha activation through the reactivation of the tumor suppressive activity of PHB2. Here, we report that ERAP has significant suppressive effects against synergistic activation caused by the crosstalk between E2 and growth factors associated with intrinsic or acquired resistance to anti-estrogen tamoxifen in breast cancer cells. Intrinsic PHB2 released from BIG3 by ERAP effectively disrupted each interaction of membrane-associated ERα and insulin-like growth factor 1 receptor beta (IGF-1Rß), EGFR, PI3K or human epidermal growth factor 2 (HER2) in the presence of E2 and the growth factors IGF or EGF, followed by inhibited the activation of IGF-1Rß, EGFR or HER2, and reduced Akt, MAPK and ERα phosphorylation levels, resulting in significant suppression of proliferation of ERα-positive breast cancer cells in vitro and in vivo. More importantly, combined treatment with ERAP and tamoxifen led to a synergistic suppression of signaling that was activated by crosstalk between E2 and growth factors or HER2 amplification. Taken together, our findings suggest that the specific inhibition of BIG3-PHB2 is a novel potential therapeutic approach for the treatment of tamoxifen-resistant breast cancers activated by the crosstalk between E2 and growth factor signaling, especially in premenopausal women.

High levels at baseline of serum pyridinoline crosslinked carboxyterminal telopeptide of type I collagen are associated with worse prognosis for breast cancer patients.

It is speculated that adjuvant use of bisphosphonate reduces recurrence in breast cancer patients through suppression of bone resorption. To determine the prognostic impact of bone resorption markers, we investigated serum levels of the pyridinoline crosslinked carboxyterminal telopeptide of type I collagen (1CTP) and N-terminal crosslinking telopeptides of type I collagen (NTX). 1CTP and NTX were measured at baseline (before operation or neoadjuvant therapies) and afterward in 469 patients operated on breast cancer. The optimal cutoff value of 1CTP for relapse-free survival (RFS) was set at 3.6 ng/ml with an area under the receiver operating characteristics curve of 0.641 [95% confidence interval (CI) = 0.560-0.721; p = 0.0011]. However, we were unable to determine a significant cutoff value for NTX. RFS was significantly worse for 1CTP-high patients with than for those with low levels of 1CTP (p = 0.0002). Multivariate analysis with tumor size, lymph node metastasis, and nuclear grade showed that 1CTP was a significant independent prognostic factor (hazard ratio = 2.04, 95% CI = 1.13-3.68; p = 0.018). Worse prognosis for the subset with high 1CTP levels applied only to postmenopausal patients (p = 0.0002). RFS of 130 patients whose 1CTP changed from low at baseline to high at 6 months postoperatively showed RFS almost as poor as that for patients with high 1CTP throughout. These findings suggest that 1CTP may be useful not only for identifying patients with unfavorable prognosis, but also for selecting patients who may benefit from administration of bone-modifying agents in an adjuvant setting.

Influence of body mass index on clinicopathological factors including estrogen receptor, progesterone receptor, and Ki67 expression levels in breast cancers.

BACKGROUND: High body mass index (BMI) is associated not only with a higher incidence of breast cancers but also with poorer prognosis. It is speculated that both enhanced production of estrogens and other factors associated with obesity are involved in these associations, but the biological characteristics associated with high BMI have yet to be thoroughly identified. METHODS: We studied 525 breast cancers, focusing on biological differences between tumors associated with high and low BMI and by immunohistochemically defined intrinsic subtype. Ki67 expression levels were used to differentiate luminal A from luminal B estrogen receptor (ER)+/human epidermal growth factor receptor 2 (HER2)-breast cancers. RESULTS: Premenopausal patients with high BMI showed a significantly higher frequency of lymph node metastasis (46.4 % vs. 22.9 %, P = 0.005) and tended to have a larger tumor size (P = 0.05) and higher nuclear grade (P = 0.07) than those with low BMI. These differences were not observed among postmenopausal patients. BMI was not associated with distribution of breast cancer subtypes, and ER, progesterone receptor (PR), and Ki67 expression levels of each subtype showed no differences between high and low BMI among premenopausal patients. CONCLUSION: Higher BMI might influence aggressive tumor characteristics among premenopausal patients, but its influence on ER, PR, and Ki67 expression levels seems to be limited.

Repositioning of mifepristone as an integrated stress response activator to potentiate cisplatin efficacy in non-small cell lung cancer.

Lung cancer, primarily non-small-cell lung cancer (NSCLC), is a significant cause of cancer-related mortality worldwide. Cisplatin-based chemotherapy is a standard treatment for NSCLC; however, its effectiveness is often limited due to the development of resistance, leading to NSCLC recurrence. Thus, the identification of effective chemosensitizers for cisplatin is of paramount importance. The integrated stress response (ISR), activated by various cellular stresses and mediated by eIF2α kinases, has been implicated in drug sensitivity. ISR activation globally suppresses protein synthesis while selectively promoting the translation of ATF4 mRNA, which can induce pro-apoptotic proteins such as CHOP, ATF3, and TRIB3. To expedite and economize the development of chemosensitizers for cisplatin treatment in NSCLC, we employed a strategy to screen an FDA-approved drug library for ISR activators. In this study, we identified mifepristone as a potent ISR activator. Mifepristone activated the HRI/eIF2α/ATF4 axis, leading to the induction of pro-apoptotic factors, independent of its known role as a synthetic steroid. Our in vitro and in vivo models demonstrated mifepristone's potential to inhibit NSCLC re-proliferation following cisplatin treatment and tumor growth, respectively, via the ISR-mediated cell death pathway. These findings suggest that mifepristone, as an ISR activator, could enhance the efficacy of cisplatin-based therapy for NSCLC, highlighting the potential of drug repositioning in the search for effective chemosensitizers.

Dynamic movement of the Golgi unit and its glycosylation enzyme zones.

Knowledge on the distribution and dynamics of glycosylation enzymes in the Golgi is essential for better understanding this modification. Here, using a combination of CRISPR/Cas9 knockin technology and super-resolution microscopy, we show that the Golgi complex is assembled by a number of small 'Golgi units' that have 1-3 µm in diameter. Each Golgi unit contains small domains of glycosylation enzymes which we call 'zones'. The zones of N- and O-glycosylation enzymes are colocalised. However, they are less colocalised with the zones of a glycosaminoglycan synthesizing enzyme. Golgi units change shapes dynamically and the zones of glycosylation enzymes rapidly move near the rim of the unit. Photobleaching analysis indicates that a glycosaminoglycan synthesizing enzyme moves between units. Depletion of giantin dissociates units and prevents the movement of glycosaminoglycan synthesizing enzymes, which leads to insufficient glycosaminoglycan synthesis. Thus, we show the structure-function relationship of the Golgi and its implications in human pathogenesis.

Blue light induces apoptosis and autophagy by promoting ROS-mediated mitochondrial dysfunction in synovial sarcoma.

BACKGROUND: Synovial sarcoma (SS) has limited treatment options and there is an urgent need to develop a novel therapeutic strategy to treat SS. Blue light (BL) has been shown to inhibit the growth of several cancer cells. However, the efficacy of BL in soft tissue sarcomas such as SS has not been demonstrated, and the detailed mechanism underlying the antitumor activity of BL is not fully understood. In this study, we investigated the antitumor effect of BL on SS. METHODS: Human SS cell lines were continuously irradiated with BL using light-emitting diodes (LEDs) in an incubator for in vitro analysis. The chicken chorioallantoic membrane (CAM) tumors and xenograft tumors in mice were subjected to daily BL irradiation with LEDs. RESULTS: BL caused growth inhibition of SS cells and histological changes in CAM tumors. BL also suppressed the migration and invasion abilities of SS cells. The type of cell death in SS cells was revealed to be apoptosis. Furthermore, BL induced excessive production of reactive oxygen species (ROS) in mitochondria, resulting in oxidative stress and malfunctioned mitochondria. Reducing the production of ROS using N-acetylcysteine (NAC), a ROS scavenger, attenuated the inhibitory effect of BL on SS cells and mitochondrial dysfunction. In addition, BL induced autophagy, which was suppressed by the administration of NAC. The autophagy inhibitor of 3-methyladenine and small interfering RNA against the autophagy marker light chain 3B facilitated apoptotic cell death. Moreover, BL suppressed tumor growth in a mouse xenograft model. CONCLUSION: Taken together, our results revealed that BL induced apoptosis via the ROS-mitochondrial signaling pathway, and autophagy was activated in response to the production of ROS, which protected SS cells from apoptosis. Therefore, BL is a promising candidate for the development of an antitumor therapeutic strategy targeting SS.

p53-independent tumor suppression by cell-cycle arrest via CREB/ATF transcription factor OASIS.

CREB/ATF transcription factor OASIS/CREB3L1 is upregulated in long-term-cultured astrocytes undergoing cell-cycle arrest due to loss of DNA integrity by repeated replication. However, the roles of OASIS in the cell cycle remain unexplored. We find that OASIS arrests the cell cycle at G2/M phase after DNA damage via direct induction of p21. Cell-cycle arrest by OASIS is dominant in astrocytes and osteoblasts, but not in fibroblasts, which are dependent on p53. In a brain injury model, Oasis-/- reactive astrocytes surrounding the lesion core show sustained growth and inhibition of cell-cycle arrest, resulting in prolonged gliosis. We find that some glioma patients exhibit low expression of OASIS due to high methylation of its promoter. Specific removal of this hypermethylation in glioblastomas transplanted into nude mice by epigenomic engineering suppresses the tumorigenesis. These findings suggest OASIS as a critical cell-cycle inhibitor with potential to act as a tumor suppressor.

Lack of impact of the ALDH2 rs671 variant on breast cancer development in Japanese BRCA1/2-mutation carriers.

The aldehyde degrading function of the ALDH2 enzyme is impaired by Glu504Lys polymorphisms (rs671, termed A allele), which causes alcohol flushing in east Asians, and elevates the risk of esophageal cancer among habitual drinkers. Recent studies suggested that the ALDH2 variant may lead to higher levels of DNA damage caused by endogenously generated aldehydes. This can be a threat to genome stability and/or cell viability in a synthetic manner in DNA repair-defective settings such as Fanconi anemia (FA). FA is an inherited bone marrow failure syndrome caused by defects in any one of so far identified 22 FANC genes including hereditary breast and ovarian cancer (HBOC) genes BRCA1 and BRCA2. We have previously reported that the progression of FA phenotypes is accelerated with the ALDH2 rs671 genotype. Individuals with HBOC are heterozygously mutated in either BRCA1 or BRCA2, and the cancer-initiating cells in these patients usually undergo loss of the wild-type BRCA1/2 allele, leading to homologous recombination defects. Therefore, we hypothesized that the ALDH2 genotypes may impact breast cancer development in BRCA1/2 mutant carriers. We genotyped ALDH2 in 103 HBOC patients recruited from multiple cancer centers in Japan. However, we were not able to detect any significant differences in clinical stages, histopathological classification, or age at clinical diagnosis across the ALDH2 genotypes. Unlike the effects in hematopoietic cells of FA, our current data suggest that there is no impact of the loss of ALDH2 function in cancer initiation and development in breast epithelium of HBOC patients.

Pivotal role for S-nitrosylation of DNA methyltransferase 3B in epigenetic regulation of tumorigenesis.

DNA methyltransferases (DNMTs) catalyze methylation at the C5 position of cytosine with S-adenosyl-L-methionine. Methylation regulates gene expression, serving a variety of physiological and pathophysiological roles. The chemical mechanisms regulating DNMT enzymatic activity, however, are not fully elucidated. Here, we show that protein S-nitrosylation of a cysteine residue in DNMT3B attenuates DNMT3B enzymatic activity and consequent aberrant upregulation of gene expression. These genes include Cyclin D2 (Ccnd2), which is required for neoplastic cell proliferation in some tumor types. In cell-based and in vivo cancer models, only DNMT3B enzymatic activity, and not DNMT1 or DNMT3A, affects Ccnd2 expression. Using structure-based virtual screening, we discovered chemical compounds that specifically inhibit S-nitrosylation without directly affecting DNMT3B enzymatic activity. The lead compound, designated DBIC, inhibits S-nitrosylation of DNMT3B at low concentrations (IC50 ≤ 100 nM). Treatment with DBIC prevents nitric oxide (NO)-induced conversion of human colonic adenoma to adenocarcinoma in vitro. Additionally, in vivo treatment with DBIC strongly attenuates tumor development in a mouse model of carcinogenesis triggered by inflammation-induced generation of NO. Our results demonstrate that de novo DNA methylation mediated by DNMT3B is regulated by NO, and DBIC protects against tumor formation by preventing aberrant S-nitrosylation of DNMT3B.