Showing papers by "Japanese Foundation for Cancer Research published in 2005"

Update on the Paris classification of superficial neoplastic lesions in the digestive tract

Abstract: Background and Study Aims: Neoplastic lesions in the digestive-tract mucosa are termed superficial when the depth of invasion is limited to the mucosa and submucosa. The endoscopic appearance has a predictive value for invasion into the submucosa, which is critical for the risk of nodal metastases. Materials and Methods: The endoscopic morphology of superficial lesions can be assessed with a standard video endoscope after spraying of a dye - an iodine-potassium iodide solution for the stratified squamous epithelium, or an indigo carmine solution for the columnar epithelium. In 2002, a workshop was held in Paris to explore the relevance of the Japanese classification. The conclusions were revised in 2003 in Osaka in relation to the definition of the subtypes used in endoscopy and the evaluation of the depth of invasion into the submucosa. In Japan, the description of advanced cancer in the digestive-tract mucosa using types 1 -4 is supplemented by a type 0 when the endoscopic appearance is that of a superficial lesion. Type 0 is divided into three categories: protruding (0-1), nonprotruding and nonexcavated (0-11), and excavated (0-III). Type 0-II lesions are then subdivided into slightly elevated (IIa), flat (IIb), or depressed (IIc). Nonprotruding depressed lesions are associated with a higher risk of submucosal invasion. After endoscopic resection, invasion into the submucosa is an important criterion for the necessity of additional surgical resection. Micrometer analysis of the depth of invasion in the specimen is more precise, and distinct cut-off limits have been established in the esophagus, stomach, and large bowel. Conclusions: The morphology of superficial and nonprotruding neoplastic lesions is relevant to the prognosis. Following endoscopic detection, the lesions are analyzed using chromoendoscopy and assigned a subtype of the type 0 classification. The choice between endoscopicorsurgical treatment is based on this description.

Classification of types of intraductal papillary-mucinous neoplasm of the pancreas: a consensus study.

Abstract: Now that more than two decades have passed since the first reports of intraductal papillary-mucinous neoplasms (IPMNs), it has become clear that IPMN consists of a spectrum of neoplasms with both morphological and immunohistochemical variations. At a meeting of international experts on pancreatic precursor lesions held in 2003, it was agreed that a consensus classification of IPMN subtypes should be established to enable a more detailed analysis of the clinicopathological significance of the variations. Based on our experience and on information from the literature, we selected representative histological examples of IPMNs and defined a consensus nomenclature and criteria for classifying variants as distinctive IPMN subtypes including gastric type, intestinal type, pancreatobiliary type, and oncocytic type. These definitions can be used for further analyses of the clinicopathological significance of the variations of IPMN.

Methylation silencing of SOCS-3 promotes cell growth and migration by enhancing JAK/STAT and FAK signalings in human hepatocellular carcinoma

Abstract: We identified that suppressor of cytokine signaling-3 (SOCS-3) gene was aberrantly methylated in its CpG island in three of 10 human hepatocellular carcinoma (HCC) cell lines. SOCS-3 RNA was undetectable in five of the 10 HCC cell lines including the three methylated cell lines, and a demethylating agent, 5-aza-2'-deoxycytidine, reactivated SOCS-3 expression in three cell lines tested. The DNA region where we found aberrant DNA methylation includes a signal transducers and activators of transcription (STAT) binding consensus sequence. When the DNA region was used as a promoter, DNA methylation markedly reduced promoter activity. SOCS-3 was also aberrantly methylated in six of 18 primary HCC samples. SOCS-3 expression was reduced in three of the three methylated and one of the three unmethylated primary samples examined. Restoration of SOCS-3 in cells lacking SOCS-3 expression suppressed STAT3 phosphorylation and cell growth. We found that IL-6 acted as a growth factor in HCC cells. Inhibition of SOCS-3 expression in cells whose growth was induced by IL-6 enhanced STAT3 phosphorylation and cell growth. In addition, AG490, a chemical JAK2 inhibitor, suppressed cell growth and downregulated STAT3 phosphorylation, but not FAK phosphorylation. We also found that SOCS-3 physically interacted with phosphorylated FAK and Elongin B in HCC cells. Restoration of SOCS-3 decreased FAK phosphorylation as well as FAK protein level. Inhibition of SOCS-3 expression increased FAK phosphorylation, resulting in enhancement of cell migration. These data indicate that SOCS-3 negatively regulates cell growth and cell motility by inhibiting Janus kinase (JAK)/STAT and FAK signalings in HCC cells. Thus, loss of SOCS-3 by the associated DNA methylation confers cells advantage in growth and migration.

The ALK-5 inhibitor A-83-01 inhibits Smad signaling and epithelial-to-mesenchymal transition by transforming growth factor-beta.

Abstract: Transforming growth factor (TGF)-β signaling facilitates tumor growth and metastasis in advanced cancer. Use of inhibitors of TGF-β signaling may thus be a novel strategy for the treatment of patients with such cancer. In this study, we synthesized and characterized a small molecule inhibitor, A-83-01, which is structurally similar to previously reported ALK-5 inhibitors developed by Sawyer et al. (2003) and blocks signaling of type I serine/threonine kinase receptors for cytokines of the TGF-β superfamily (known as activin receptor-like kinases; ALKs). Using a TGF-β-responsive reporter construct in mammalian cells, we found that A-83-01 inhibited the transcriptional activity induced by TGF-β type I receptor ALK-5 and that by activin type IB receptor ALK-4 and nodal type I receptor ALK-7, the kinase domains of which are structurally highly related to those of ALK-5. A-83-01 was found to be more potent in the inhibition of ALK5 than a previously described ALK-5 inhibitor, SB-431542, and also to prevent phosphorylation of Smad2/3 and the growth inhibition induced by TGF-β. In contrast, A-83-01 had little or no effect on bone morphogenetic protein type I receptors, p38 mitogen-activated protein kinase, or extracellular regulated kinase. Consistent with these findings, A-83-01 inhibited the epithelial-to-mesenchymal transition induced by TGF-β, suggesting that A-83–01 and related molecules may be useful for preventing the progression of advanced cancers. (Cancer Sci 2005; 96: 791–800)

Complications of craniofacial resection for malignant tumors of the skull base: Report of an International Collaborative Study

Abstract: Background. Advances in imaging, surgical technique, and perioperative care have made craniofacial resection (CFR) an effective and safe option for treating malignant tumors involving the skull base. The procedure does, however, have complications. Because of the relative rarity of these tumors, most existing data on postoperative complications come from individual reports of relatively small series of patients. This international collaborative report examines a large cohort of patients accumulated from multiple institutions with the aim of identifying patient-related and tumor-related predictors of postoperative morbidity and mortality and set a benchmark for future studies. Methods. One thousand one hundred ninety-three patients from 17 institutions were analyzed for postoperative mortality and complications. Postoperative complications were classified into systemic, wound, central nervous system (CNS), and orbit. Statistical analyses were carried out in relation to patient characteristics, extent of disease, prior radiation treatment, and type of reconstruction to determine factors that predicted mortality or complications. Results. Postoperative mortality occurred in 56 patients (4.7%). The presence of medical comorbidity was the only independent predictor of mortality. Postoperative complications occurred in 433 patients (36.3%). Wound complications occurred in 237 (19.8%), CNS-related complications in 193 (16.2%), orbital complications in 20 (1.7%), and systemic complications in 57 (4.8%) patients. Medical comorbidity, prior radiation therapy, and the extent of intracranial tumour involvement were independent predictors of postoperative complications. Conclusions. CFR is a safe surgical treatment for malignant tumors of the skull base, with an overall mortality of 4.7% and complication rate of 36.3%. The impact of medical comorbidity and intracranial tumor extent should be carefully considered when planning therapy for patients whose tumors are amenable to CFR. © 2005 Wiley Periodicals, Inc. Head Neck27: XXX–XXX, 2005

Craniofacial resection for malignant paranasal sinus tumors: Report of an International Collaborative Study

Abstract: Background. Malignant tumors of the superior sinonasal vault are rare, and, because of this and the varied histologic findings, most outcomes data reflect the experience of small patient cohorts. This International Collaborative study examines a large cohort of patients accumulated from multiple institutions experienced in craniofacial surgery, with the aim of reporting benchmark figures for outcomes and identifying patient-related and tumor-related predictors of prognosis after craniofacial resection (CFR). Methods. Three hundred thirty-four patients from 17 institutions were analyzed for outcome. Patients with esthesioneuroblastoma were excluded and are being reported separately. The median age was 57 years (range, 3–98 years). One hundred eighty-eight patients (56.3%) had had prior single-modality or combined treatment, which included surgery in 120 (36%), radiation in 79 (23.7%), and chemotherapy in 56 (16.8%). The most common histologic findings were adenocarcinoma in 107 (32%) and squamous cell carcinoma in 101 (30.2%). The margins of resection were close or microscopically positive in 95 (30%). Adjuvant radiotherapy was given in 161 (48.2%) and chemotherapy in 16 (4.8%). Statistical analyses for outcomes were performed in relation to patient characteristics, tumor characteristics, including histologic findings and extent of disease, surgical resection margins, prior radiation, and prior chemotherapy to determine predictive factors. Results. Postoperative mortality occurred in 15 patients (4.5%). Postoperative complications occurred in 110 patients (32.9%). The 5-year overall, disease-specific, and recurrence-free survival rates were 48.3%, 53.3%, and 45.8%, respectively. The status of surgical margins, histologic findings of the primary tumor, and intracranial extent were independent predictors of overall, disease-specific, and recurrence-free survival on multivariate analysis. Conclusions. CFR for malignant paranasal sinus tumors is a safe surgical treatment with an overall mortality of 4.5% and complication rate of 33%. The status of surgical margins, histologic findings of the primary tumor, and intracranial extent are independent predictors of outcome. © 2005 Wiley Periodicals, Inc. Head Neck27: XXX–XXX, 2005

Enhanced Expression of Aggrus (T1alpha/Podoplanin), a Platelet-Aggregation-Inducing Factor in Lung Squamous Cell Carcinoma

Abstract: Aggrus (T1alpha/podoplanin, known as a specific marker for type I alveolar cells or lymphatic endothelial cells) is a transmembrane sialoglycoprotein that aggregates platelets. Previously, we showed that upregulated expression of Aggrus occurs in colorectal tumors or testicular tumors and could be associated with platelet-aggregating activity and metastatic ability. In testicular tumors, Aggrus is specifically expressed in seminoma. The present study investigates Aggrus expression in human primary lung cancer tissues of different types. Microarray analysis demonstrated that aggrus was significantly expressed in squamous cell carcinoma (10/15; 66.7%). Immunohistochemical analysis also showed that the incidence of positive staining in sections of squamous cell carcinoma (7/8; 87.5%) was higher than that in adenocarcinoma (2/13; 15.4%). Furthermore, Aggrus expression was detected in a squamous cell carcinoma cell line, NCI-H226, by real-time PCR. These findings indicated that overexpression of Aggrus occurred in squamous cell carcinoma of the lung. Therefore, Aggrus could be a useful diagnostic marker for squamous cell carcinoma of the lung.

NEDD4-2 (neural precursor cell expressed, developmentally down-regulated 4-2) negatively regulates TGF-β (transforming growth factor-β) signalling by inducing ubiquitin-mediated degradation of Smad2 and TGF-β type I receptor

Abstract: Inhibitory Smad, Smad7, is a potent inhibitor of TGF-β (transforming growth factor-β) superfamily signalling. By binding to activated type I receptors, it prevents the activation of R-Smads (receptor-regulated Smads). To identify new components of the Smad pathway, we performed yeast two-hybrid screening using Smad7 as bait, and identified NEDD4-2 (neural precursor cell expressed, developmentally down-regulated 4-2) as a direct binding partner of Smad7. NEDD4-2 is structurally similar to Smurfs (Smad ubiquitin regulatory factors) 1 and 2, which were identified previously as E3 ubiquitin ligases for R-Smads and TGF-β superfamily receptors. NEDD4-2 functions like Smurfs 1 and 2 in that it associates with TGF-β type I receptor via Smad7, and induces its ubiquitin-dependent degradation. Moreover, NEDD4-2 bound to TGF-β-specific R-Smads, Smads 2 and 3, in a ligand-dependent manner, and induced degradation of Smad2, but not Smad3. However, in contrast with Smurf2, NEDD4-2 failed to induce ubiquitination of SnoN (Ski-related novel protein N), although NEDD4-2 bound to SnoN via Smad2 more strongly than Smurf2. We showed further that overexpressed NEDD4-2 prevents transcriptional activity induced by TGF-β and BMP, whereas silencing of the NEDD4-2 gene by siRNA (small interfering RNA) resulted in enhancement of the responsiveness to TGF-β superfamily cytokines. These data suggest that NEDD4-2 is a member of the Smurf-like C2-WW-HECT (WW is Trp-Trp and HECT is homologous to the E6-accessory protein) type E3 ubiquitin ligases, which negatively regulate TGF-β superfamily signalling through similar, but not identical, mechanisms to those used by Smurfs.

Estrogen-mediated post transcriptional down-regulation of breast cancer resistance protein/ABCG2.

Abstract: Breast cancer resistance protein (BCRP)/ABCG2 mediates concurrent resistance to chemotherapeutic agents, such as 7-ethyl-10-hydroxycamptothecin (SN-38), mitoxantrone, and topotecan, by pumping them out of cells. We previously reported that BCRP transports sulfated estrogens. In the present study, we show that at physiologic levels, estrogens markedly decrease endogenous BCRP expression in the estrogen-responsive and estrogen receptor alpha (ERalpha)-positive human breast cancer MCF-7 cells, but not in estrogen-nonresponsive human cancer cells. 17 beta-Estradiol (E(2)) also significantly reduces exogenous BCRP expression, driven by a constitutive promoter, in BCRP-transduced estrogen-responsive and ERalpha-positive MCF-7 (MCF-7/BCRP) and T-47D cells, but not in BCRP-transduced estrogen-nonresponsive MDA-MB-231 and SKOV-3 cells. E(2) potentiates the cytotoxicity of SN-38, but not vincristine, in MCF-7/BCRP cells significantly, and increases cellular topotecan uptake in MCF-7 and MCF-7/BCRP cells. Antiestrogen tamoxifen partially reverses E(2)-mediated BCRP down-regulation in MCF-7 and MCF-7/BCRP cells and treatment of MCF-7/BCRP cells with an ERalpha small interfering RNA abolished E(2)-mediated BCRP down-regulation, suggesting that interaction of E(2) and ERalpha is necessary for BCRP down-regulation. E(2) does not affect endogenous BCRP mRNA levels in MCF-7 cells or exogenous BCRP mRNA levels in MCF-7/BCRP cells. The results from pulse-chase labeling experiments with MCF-7/BCRP cells suggest that decreased protein biosynthesis and maturation, but not alterations in protein turnover, might underlie E(2)-mediated BCRP down-regulation. These data indicate that estrogen down-regulates BCRP expression by novel posttranscriptional mechanisms. This is the first report of small molecules that can affect BCRP protein expression in cells and may therefore assist in establishing new strategies for regulating BCRP expression.

Pulmonary adenocarcinomas with enteric differentiation: histologic and immunohistochemical characteristics compared with metastatic colorectal cancers and usual pulmonary adenocarcinomas.

Abstract: Primary pulmonary adenocarcinomas with enteric differentiation (PAED) are mainly composed of tall-columnar cells that show similarity to intestinal epithelia and colorectal carcinomas. In this study, we analyzed the immunostaining profiles of 7 PAEDs in comparison with 14 metastatic colorectal carcinomas (MCRs) and 30 usual pulmonary adenocarcinomas (PACs), using antibodies against CDX-2, cytokeratin 7 (CK7), cytokeratin 20 (CK20), TTF-1, surfactant apoprotein-A (SP-A), Napsin A, and MUC2. The positive rates for CDX-2, CK7, CK20, TTF-1, SP-A, Napsin A, and MUC2 were 71%, 100%, 43%, 43%, 14%, 0%, and 43%, respectively, in the PAEDs; 100%, 0%, 86%, 0%, 0%, 0%, and 57% in the MCRs; 3%, 100%, 0%, 93%, 73%, 90%, and 0% in PACs. As expected, immunoreactivity of CDX-2, CK20, and MUC2 was detected in PAEDs. The observed decrease or loss of immunoreactivity for TTF-1, SP-A, and Napsin A indicates that these lesions demonstrate a shift away from their pulmonary phenotype, although CK7 expression was retained. The results indicate that CK7 and CK20 may be useful markers for distinction of PAEDs from MCRs.

Akt/Protein Kinase B-Dependent Phosphorylation and Inactivation of WEE1Hu Promote Cell Cycle Progression at G2/M Transition

Abstract: The serine/threonine kinase Akt is known to promote cell growth by regulating the cell cycle in G1 phase through activation of cyclin/Cdk kinases and inactivation of Cdk inhibitors. However, how the G2/M phase is regulated by Akt remains unclear. Here, we show that Akt counteracts the function of WEE1Hu. Inactivation of Akt by chemotherapeutic drugs or the phosphatidylinositide-3-OH kinase inhibitor LY294002 induced G2/M arrest together with the inhibitory phosphorylation of Cdc2. Because the increased Cdc2 phosphorylation was completely suppressed by wee1hu gene silencing, WEE1Hu was associated with G2/M arrest induced by Akt inactivation. Further analyses revealed that Akt directly bound to and phosphorylated WEE1Hu during the S to G2 phase. Serine-642 was identified as an Akt-dependent phosphorylation site. WEE1Hu kinase activity was not affected by serine-642 phosphorylation. We revealed that serine-642 phosphorylation promoted cytoplasmic localization of WEE1Hu. The nuclear-to-cytoplasmic translocation was mediated by phosphorylation-dependent WEE1Hu binding to 14-3-3theta but not 14-3-3beta or -sigma. These results indicate that Akt promotes G2/M cell cycle progression by inducing phosphorylation-dependent 14-3-3theta binding and cytoplasmic localization of WEE1Hu.

Identification of ATF-3, caveolin-1, DLC-1, and NM23-H2 as putative antitumorigenic, progesterone-regulated genes for ovarian cancer cells by gene profiling.

Abstract: Although progesterone (P4) has been implicated to offer protection against ovarian cancer (OCa), little is known of its mechanism of action. The goal of this study was to identify P4-regulated genes that have anti-OCa action. Three immortalized nontumorigenic human ovarian surface epithelial (HOSE) cell lines and three OCa (OVCA) cell lines were subjected to 5 days of P4 treatment. Transcriptional profiling with a cDNA microarray containing ≈2400 known genes was used to identify genes (1) whose expression was consistently downregulated in OVCA cell lines compared to HOSE cell lines, and (2) whose expression was restored in OCa cell lines by P4 treatment. From the candidates selected, activating transcription factor-3 (ATF-3), caveolin-1, deleted in liver cancer-1 (DLC-1), and nonmetastatic clone 23 (NM23-H2) were chosen for post hoc functional studies based on their previously reported action as tumor suppressors or apoptosis inducers. Semiquantitative RT–PCR analyses confirmed loss of or reduced transcription of these genes in OVCA cells when compared to HOSE cells and their upregulation following P4 treatment. Hormonal specificity was demonstrated by blockade experiments with a progestin antagonist RU 38486. Ectopic expression of caveolin-1, DLC-1, and NM23-H2 caused growth inhibition in OVCA cell cultures, but not in HOSE cell cultures, while forced expression of ATF-3 suppressed growth in both. Overexpression of AFT-3 also enhanced caspase-3 activity in both HOSE and OVCA cells, whereas ectopic expression of caveolin-1 and DLC-1 only activated this enzyme in OCa cells. In contrast, NM23-H2 overexpression was ineffective in activating caspase-3. Overexpression of any of the four genes in OCa cells reduced soft-agar colony formation and cell invasiveness. Taken together, we have identified four new P4-regulated, antitumor genes for OCa. However, their modes of action differ significantly; ATF-3 primarily functions as an apoptosis inducer, NM23-H2 as a suppressor of cell motility, and caveolin-1 and DLC-1 exhibiting features of classical tumor suppressors. To the best of our knowledge, except for NM23-H2, this is the first report linking P4 to the regulation of these tumor suppressor/proapoptotic genes, which could serve as future therapeutic targets.

Achlorhydria by ezrin knockdown defects in the formation/expansion of apical canaliculi in gastric parietal cells

Abstract: Loss of gastric acid secretion is pathologically known as achlorhydria. Acid-secreting parietal cells are characterized by abundant expression of ezrin (Vil2), one of ezrin/radixin/moesin proteins, which generally cross-link actin filaments with plasma membrane proteins. Here, we show the direct in vivo involvement of ezrin in gastric acid secretion. Ezrin knockout (Vil2(-/-)) mice did not survive >1.5 wk after birth, making difficult to examine gastric acid secretion. We then generated ezrin knockdown (Vil2(kd/kd)) mice by introducing a neomycin resistance cassette between exons 2 and 3. Vil2(kd/kd) mice born at the expected Mendelian ratio exhibited growth retardation and a high mortality. Approximately 7% of Vil2(kd/kd) mice survived to adulthood. Ezrin protein levels in Vil2(kd/kd) stomachs decreased to <5% of the wild-type levels without compensatory up-regulation of radixin or moesin. Adult Vil2(kd/kd) mice suffered from severe achlorhydria. Immunofluorescence and electron microscopy revealed that this achlorhydria was caused by defects in the formation/expansion of canalicular apical membranes in gastric parietal cells.

Genetic analysis of Pten and Tsc2 functional interactions in the mouse reveals asymmetrical haploinsufficiency in tumor suppression

Abstract: The role of tumor suppressor haploinsufficiency in oncogenesis is still poorly understood. The PTEN and TSC2 tumor suppressors function to antagonize mTOR (mammalian target of rapamycin) activation by Akt; hence, compound heterozygous inactivation of Pten and Tsc2 in the mouse may in principle exacerbate the tumor phenotypes observed in the single mutants in a reciprocal manner. In contrast, we found that while Tsc2 heterozygosity unmasks Pten haploinsufficiency in growth and tumor suppression, tumorigenesis in Tsc2+/- mutants is surprisingly not accelerated by Pten heterozygosity, even though mTOR activation is cooperatively enhanced by compound Pten/Tsc2 heterozygosity. We show that the wild-type alleles of both Pten and Tsc2 are retained in prostate tumors from both Pten+/- and Pten+/-Tsc2+/- mice, whereas TSC-related tumor lesions are invariably associated with Tsc2 loss of heterozygosity (LOH) in both Tsc2+/- and Pten+/-Tsc2+/- mice. These findings demonstrate that inactivation of TSC2 is epistatic to PTEN in the control of tumor initiation and progression and, importantly, that both Pten and Tsc2 are haploinsufficient for suppression of tumorigenesis initiated by Pten heterozygosity, while neither Pten nor Tsc2 is haploinsufficient for repression of carcinogenesis arising from Tsc2 heterozygosity, providing a rationale for the differential cancer susceptibility of the two human conditions associated with PTEN or TSC2 heterozygous mutations.

Two subclasses of lung squamous cell carcinoma with different gene expression profiles and prognosis identified by hierarchical clustering and non-negative matrix factorization

Abstract: Current clinical and histopathological criteria used to define lung squamous cell carcinomas (SCCs) are insufficient to predict clinical outcome. To make a clinically useful classification by gene expression profiling, we used a 40 386 element cDNA microarray to analyse 48 SCC, nine adenocarcinoma, and 30 normal lung samples. Initial analysis by hierarchical clustering (HC) allowed division of SCCs into two distinct subclasses. An additional independent round of HC induced a similar partition and consensus clustering with the non-negative matrix factorization approach indicated the robustness of this classification. Kaplan-Meier analysis with the log-rank test pointed to a nonsignificant difference in survival (P = 0.071), but the likelihood of survival to 6 years was significantly different between the two groups (40.5 vs 81.8%, P = 0.014, Z-test). Biological process categories characteristic for each subclass were identified statistically and upregulation of cell-proliferation-related genes was evident in the subclass with poor prognosis. In the subclass with better survival, genes involved in differentiated intracellular functions, such as the MAPKKK cascade, ceramide metabolism, or regulation of transcription, were upregulated. This work represents an important step toward the identification of clinically useful classification for lung SCC.

p53-Defective Tumors With a Functional Apoptosome-Mediated Pathway: A New Therapeutic Target

Abstract: Background: Although cancer cells appear to maintain the machinery for intrinsic apoptosis, defects in the pathway develop during malignant transformation, preventing apoptosis from occurring. How to specifically induce apoptosis in cancer cells remains unclear. Methods: We determined the apoptosome activity and p53 status of normal human cells and of lung, colon, stomach, brain, and breast cancer cells by measuring cytochrome c-dependent caspase activation and by DNA sequencing, respectively, and we used COMPARE analysis to identify apoptosome-specific agonists. We compared cell death, cytochrome c release, and caspase activation in NCI-H23 (lung cancer), HCT-15 (colon cancer), and SF268 (brain cancer) cells treated with Triacsin c, an inhibitor of acyl-CoA synthetase (ACS), or with vehicle. The cells were mock, transiently, or stably transfected with genes for Triacsin c-resistant ACSL5, dominant negative caspase-9, or apoptotic protease activating factor-1 knockdown. We measured ACS activity and levels of cardiolipin, a mitochondrial phospholipid, in mock and ACSL5-transduced SF268 cells. Nude mice carrying NCI-H23 xenograft tumors (n = 10) were treated with Triacsin c or vehicle, and xenograft tumor growth was assessed. Groups were compared using two-sided Student t tests. Results: Of 21 p53-defective tumor cell lines analyzed, 17 had higher apoptosome activity than did normal cells. Triacsin c selectively induced apoptosome-mediated death in tumor cells (caspase activity of Triacsin c-treated versus untreated SF268 cells; means = 1020% and 100%, respectively; difference = 920%, 95% CI = 900% to 940%; P<.001). Expression of ACSL5 suppressed Triacsin c-induced cytochrome c release and subsequent cell death (cell survival of Triacsin c-treated mockversus ACSL5-transduced SF268 cells; means = 40% and 83%, respectively; difference = 43%, 95% CI = 39% to 47%; P<.001). ACS was also essential to the maintenance of cardiolipin levels. Finally, Triacsin c suppressed growth of xenograft tumors (relative tumor volume on day 21 of Triacsin c-treated versus untreated mice; means = 4.6 and 9.6, respectively; difference = 5.0, 95% CI = 2.1 to 7.9; P =.006). Conclusions: Many p53-defective tumors retain activity of the apoptosome, which is therefore a potential target for cancer chemotherapy. Inhibition of ACS may be a novel strategy to induce the death of p53-defective tumor cells.

EWSR1 is fused to POU5F1 in a bone tumor with translocation t(6;22)(p21;q12).

Abstract: POU5F1(OCT3/4) is a sequence-specific transcription factor that is essential for keeping germ cells and embryonic stem cells in an immature and pluripotent status. In this article, we report that POU5F1 was fused to EWSR1 in a case of undifferentiated sarcoma derived from pelvic bone with chromosomal translocation t(6;22)(p21;q12). The EWSR1-POU5F1 chimera consists of exons 1-6 of EWSR1 and exons 2-5 and a part of exon 1 of POU5F1. The predicted amino acid sequence indicates that the chimera is composed of the N-terminal QSY domain of EWS that functions as a transcriptional activation domain and the C-terminal POU DNA-binding domains derived from POU5F1. The t(6;22) tumor does not belong to any known categories of bone and soft-tissue tumors (BSTs). It is suggested that EWS-POU5F1 may act as an oncogenic transcription factor and that its expression may contribute to undifferentiated and immature phenotypes of BST.

Involvement of mitochondrial aggregation in arsenic trioxide (As2O3)‐induced apoptosis in human glioblastoma cells

Abstract: Arsenic trioxide (As(2)O(3)) is effective against acute promyelocytic leukemia and has potential as a novel treatment against malignant solid tumors. As(2)O(3) induces differentiation and inhibits growth. It also causes mitochondrial damage mediated by the production of reactive oxygen species (ROS) and the dissipation of mitochondrial transmembrane potential (DeltaPsi(m)), leading to apoptosis. Mitochondria might be the key target of antitumor activity by As(2)O(3); however, its mechanisms have not been completely elucidated. Using two human glioblastoma cell lines, A172 and T98G, we found that As(2)O(3) induced apoptosis in A172 cells but not in T98G cells. As(2)O(3)-induced ROS production was observed in both cell lines; however, the dissipation of DeltaPsi(m), Bax oligomerization and caspase activation occurred only in As(2)O(3)-sensitive A172 cells. To determine the mechanisms of As(2)O(3)-induced apoptosis after ROS generation, we examined the change of mitochondrial morphology. As we reported previously, mitochondrial aggregation occurs before cytochrome c release during apoptosis, thus playing a role in cell death progression. We observed mitochondrial aggregation in As(2)O(3)-sensitive A172 cells but not in T98G cells treated with As(2)O(3). Using laser scanning cytometry, we quantitatively confirmed the results, which indicate that mitochondrial aggregation plays an important role in regulating sensitivity to As(2)O(3)-induced apoptosis. We propose a sequential process involving ROS generation, mitochondrial aggregation, Bax oligomerization and DeltaPsi(m) dissipation, and caspase activation during As(2)O(3)-induced apoptosis.

Breast cancer resistance protein: molecular target for anticancer drug resistance and pharmacokinetics/pharmacodynamics.

Abstract: Breast cancer resistance protein (BCRP) is a half-molecule ATP-binding cassette transporter that forms a functional homodimer and pumps out various anticancer agents, such as 7-ethyl-10-hydroxycamptothecin, topotecan, mitoxantrone and flavopiridol, from cells. Estrogens, such as estrone and 17β-estradiol, have been found to restore drug sensitivity levels in BCRP-transduced cells by increasing the cellular accumulation of such agents. Furthermore, synthetic estrogens, tamoxifen derivatives and phytoestrogens/flavonoids have now been identified that can effectively circumvent BCRP-mediated drug resistance. Transcellular transport experiments have shown that BCRP transports sulfated estrogens and various sulfated steroidal compounds, but not free estrogens. The kinase inhibitor gefitinib inhibited the transporter function of BCRP and reversed BCRP-mediated drug resistance both in vitro and in vivo. BCRP-transduced human epidermoid carcinoma A431 (A431/BCRP) and BCRP-transduced human non-small cell lung cancer PC-9 (PC-9/BCRP) cells showed gefitinib resistance. Physiological concentrations of estrogens (10–100 pM) reduced BCRP protein expression without affecting its mRNA levels. Two functional polymorphisms of the BCRP gene have been identified. The C376T (Q126Stop) polymorphism has a dramatic phenotype as active BCRP protein cannot be expressed from a C376T allele. The C421A (Q141K) polymorphism is also significant as Q141K-BCRP-transfected cells show markedly low protein expression levels and low-level drug resistance. Hence, individuals with C376T or C421A polymorphisms may express low levels of BCRP or none at all, resulting in hypersensitivity of normal cells to BCRP-substrate anticancer agents. In summary, both modulators of BCRP and functional single nucleotide polymorphisms within the BCRP gene affect the transporter function of the protein and thus can modulate drug sensitivity and substrate pharmacokinetics and pharmacodynamics in affected cells and individuals. (Cancer Sci 2005; 96: 457–465)

Leptosins isolated from marine fungus Leptoshaeria species inhibit DNA topoisomerases I and/or II and induce apoptosis by inactivation of Akt/protein kinase B.

Abstract: DNA topoisomerases (topo) I and II are molecular targets of several potent anticancer agents. Thus, inhibitors of these enzymes are potential candidates or model compounds for anticancer drugs. Leptosins (Leps) F and C, indole derivatives, were isolated from a marine fungus, Leptoshaeria sp. as cytotoxic substances. In vitro cytotoxic effects of Lep were measured using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide-based viability assay. Lep F inhibited the activity of topos I and II, whereas Lep C inhibited topo I in vitro. Interestingly both of the compounds were found to be catalytic inhibitors of topo I, as evidenced by the lack of stabilization of reaction intermediate cleavable complex (CC), as camptothecin (CPT) does stabilize. Furthermore, Lep C inhibited the CC stabilization induced by CPT in vitro. In vivo band depletion analysis demonstrated that Lep C likewise appeared not to stabilize CC, and inhibited CC formation by CPT, indicating that Lep C is also a catalytic inhibitor of topo I in vivo. Cell cycle analysis of Lep C-treated cells showed that Lep C appeared to inhibit the progress of cells from G(1) to S phase. Lep C induced apoptosis in RPMI8402 cells, as revealed by the accumulation of cells in sub-G(1) phase, activation of caspase-3 and the nucleosomal degradation of chromosomal DNA. Furthermore, Leps F and C inhibited the Akt pathway, as demonstrated by dose-dependent and time-dependent dephosphorylation of Akt (Ser473). Our study shows that Leps are a group of anticancer chemotherapeutic agents with single or dual catalytic inhibitory activities against topos I and II.

Role of Cys‐603 in dimer/oligomer formation of the breast cancer resistance protein BCRP/ABCG2

Abstract: Breast cancer resistance protein (BCRP/ABCG2) is a half-molecule ATP-binding cassette transporter that we have previously suggested might function as a homodimer, bridged by disulfide bonds. In the present study, we carried out cysteine-scanning mutagenesis, substituting Ser for Cys, and established 12 PA317 transfectants expressing BCRP mutants with possible disruptions to their S-S bonds. Western blot analysis of BCRP from the wild-type transfectants (PA/WT) confirmed that the wild-type protein migrates as a 140-kDa dimer under non-reducing conditions, but as a 70-kDa monomer under reducing conditions. However, under non-reducing conditions the BCRP-C603S mutant migrated both as a 70-kDa monomer and a 140-kDa dimer, whereas all other mutant BCRP migrated only as dimers. PA317 cells transfected with C603S-BCRP (PA/C603S) showed either similar or only marginally lower SN-38 resistance than PA/WT cells, despite the reduced levels of BCRP dimer in these cells. Moreover, the degree of SN-38 resistance in the mutant BCRP transfectants was found to be associated with the monomer expression levels under reducing conditions. Reverse transcription-polymerase chain reaction analysis showed that the BCRP mRNA levels were similar in the transfectants. We subsequently generated six C603X mutants of BCRP (X=D, H, R, Y, A and W) and carried out western blot analysis and drug sensitivity assays. The results were equivalent to those from the PA/C603S cells, with some variations that again corresponded to the monomer levels. Our findings suggest that Cys-603 is an important residue in the covalent bridge between BCRP monomers but that a functioning unit of BCRP may not necessarily require covalent linkages.