Higher Tumor Incidence Research Articles

UDP‐glucuronosyltransferase 1 (UGT1) knockdown in colon epithelial cells causes inactivation of P53 mediated apoptosis and increases colon tumorigenesis (LB599)

Significant evidence demonstrates a pattern of down‐regulation of UGT expression in tumor tissue when compared to surrounding healthy tissue. This indicates the loss of UGT expression may be an early marker in the process of tissue neoplastic transformation. Although the UGTs are usually considered to be a metabolic defense against chemical carcinogens through glucuronidation, the underlying mechanism is still unclear. Here we show that UGT1 silenced by UGT1A siRNA in HT29 and LS180 colon epithelial cells decreases actinomycin D and etoposide‐induced P53 protein expression. Also observed is a reduction in P21, BAX, and caspase‐3, with a lowering of the cytotoxicity of these two chemicals, indicating inactivation of P53 mediated apoptosis. To identify this phenomenon in vivo, intestinal epithelial cell (IEC)‐specific Ugt1 knockout (Ugt1ΔIEC) and control (Ugt1F/F) mice are treated with dextran sulfate sodium (DSS) to induce acute colon inflammation and cell apoptosis. Corresponding with the in vitro data, western blot and TUNEL stain show lower protein expressions of P53, P21, BAX, caspase‐3 and less apoptotic cells in the colon of Ugt1ΔIEC mice. However, there is no difference in inflammatory response between Ugt1ΔIEC and Ugt1F/F samples. Moreover, the treatment of azoxymethane plus DSS causes higher tumor incidence and larger tumor size in the colon of Ugt1ΔIEC mice, suggesting that the inactivation of P53 mediated apoptosis increases colon tumorigenesis. In summary, our experiments verify that the presence of UGT1 in colon epithelial cells is important in the activation of P53 mediated apoptosis and protects normal tissue from neoplastic transformation.Grant Funding Source: Supported by US Public Health Service Grants R21CA171008, ES010337 and GM100481, Natural Science Foundation of China (Grants 91029746), and Chiha Scholarship Funding

Bilateral Ovary Adrenal Rest Tumor in a Congenital Adrenal Hyperplasia Following Adrenalectomy

In contrast to the high incidence of testicular adrenal rest tumors in adult male patients with congenital adrenal hyperplasia (CAH), ovarian adrenal rest tumors (OARTs) in female CAH patients are rare. In this case report, we describe a case of bilateral OART in a female patient with CAH due to 21-hydroxylase deficiency. We present a detailed case report with the clinical, imaging, and laboratory findings of the patient. The pertinent literature is also reviewed. A 17-year-old patient was known to have CAH due to 21-hydroxylase deficiency. Since the second month of her gestational age, her mother was treated with cortisone-replacement therapy. The patient was treated with hydrocortisone and fludrocortisone since the neonatal period. Her pertinent history included a bilateral adrenalectomy at the age of 13 years in 2006, and for 3 years she led a normal puberty life with no complaint with hormonal replacement therapy. Nevertheless, in 2009, she developed a virilizing syndrome. Subsequently, she underwent surgery in December 2009 for right adnexectomy. However, the regression of the masculinizing mass was not complete and worsened several months after the surgery. A new pelvic magnetic resonance image showed the activation of a contralateral ovarian mass, necessitating a left adnexectomy in August 2010. This case demonstrates some interesting features of OART that pose challenges to its management. If an OART is detected early enough and glucocorticoid therapy is received, it is possible that the OART will decrease in size following suppression of adrenocorticotropic hormone levels.

Hobnail Variant of Papillary Thyroid Carcinoma: An Institutional Case Series and Molecular Profile

Papillary thyroid carcinoma (PTC) is increasing in incidence while mortality is unchanged. Identifying patients with higher risk of recurrence and death is essential. Case series identify the hobnail variant of PTC (HVPTC), which is characterized by micropapillary architecture, apocrine features, and loss of cellular polarity. Herein, we describe the clinical course, pathologic features, and mutational profile of patients at our institution with HVPTC. A query into the surgical pathologic database (2009-2012) was performed, and clinicopathologic data were collected on all patients carrying the diagnosis of HVPTC. BRAF(V600E) testing was performed on paraffin-embedded blocks using SNaPshot mutational analysis. Twelve patients with HVPTC were identified, with an average age of 54.1±18.8 years. Seven patients (63.6%) were AJCC Stage III or IV at presentation. Tumors were large (3.7±2.0 cm), some were multifocal (33.3%), and frequently with extrathyroidal extension (58.3%), lymphovascular invasion (41.7%), and lymph node metastasis (75%). Forty percent of the patients had concomitant tall cell features (TCF), and two had small foci of undifferentiated (anaplastic) thyroid carcinoma (ATC). Eighty percent of tumors undergoing mutational analysis had the BRAF(V600E) mutation, and the remaining 20% harbored a RET/PTC1 gene rearrangement. No other known thyroid cancer mutations were identified on SNaPshot analysis. At median follow-up of 26 months, four patients had recurrent or persistent disease, one of whom died from the disease one year after surgery. The hobnail variant of PTC has an aggressive behavior, with a high incidence of infiltrative tumors and metastatic disease. Strikingly, all tumors in our series harbored a PTC-associated genetic abnormality, either a BRAF(V600E) mutation (80%) or a RET/PTC1 rearrangement (20%). This histologic variant warrants further study, and patients with this diagnosis should be observed closely for recurrence.

Incidence and Metastasis of Cutaneous Malignant Melanoma with Respect to ABO Blood Groups: A Case-Controlled Study in Northeast of China

BackgroundABO blood groups have been suggested to contribute to the development of certain tumors; however, the associations between ABO blood groups and the incidence and metastases of cutaneous malignant melanomas have not been fully evaluated in Chinese populations. Thus, we investigated these associations with a case-controlled study in northeast of China.MethodsA total of 482 patients with cutaneous malignant melanoma and 3,068 healthy- controls were enrolled for the study between 2001 and 2012 at The Tumor Hospital of Harbin Medical University. A multivariate logistic model was used to evaluate adjusted odds ratios (ORs) and 95% confidence intervals (CI) for the incidence and metastases of cutaneous malignant melanoma.ResultsBlood type A individuals had higher tumor incidence and metastasis compared to those with blood type O (OR = 1.575; 95% CI = 1.208–2.053, p = 0.001; OR = 2.004; 95% CI = 1.032–3.889, p = 0.040), after adjusting for age, gender, smoking status and alcohol consumption.ConclusionsBlood type A was associated with higher incidence and metastasis of cutaneous malignant melanoma but future studies are needed to examine the mechanisms linking cutaneous malignant melanoma to ABO blood types.

Brca2 and tp53 Collaborate in Tumorigenesis in Zebrafish

Germline mutations in the tumor suppressor genes BRCA2 and TP53 significantly influence human cancer risk, and cancers from humans who inherit one mutant allele for BRCA2 or TP53 often display loss of the wildtype allele. In addition, BRCA2-associated cancers often exhibit mutations in TP53. To determine the relationship between germline heterozygous mutation (haploinsufficiency) and somatic loss of heterozygosity (LOH) for BRCA2 and TP53 in carcinogenesis, we analyzed zebrafish with heritable mutations in these two genes. Tumor-bearing zebrafish were examined by histology, and normal and neoplastic tissues were collected by laser-capture microdissection for LOH analyses. Zebrafish on a heterozygous tp53M214K background had a high incidence of malignant tumors. The brca2Q658X mutation status determined both the incidence of LOH and the malignant tumor phenotype. LOH for tp53 occurred in the majority of malignant tumors from brca2 wildtype and heterozygous mutant zebrafish, and most of these were malignant peripheral nerve sheath tumors. Malignant tumors in zebrafish with heterozygous mutations in both brca2 and tp53 frequently displayed LOH for both genes. In contrast, LOH for tp53 was uncommon in malignant tumors from brca2 homozygotes, and these tumors were primarily undifferentiated sarcomas. Thus, carcinogenesis in zebrafish with combined mutations in tp53 and brca2 typically requires biallelic mutation or loss of at least one of these genes, and the specific combination of inherited mutations influences the development of LOH and the tumor phenotype. These results provide insight into cancer development associated with heritable BRCA2 and TP53 mutations.

Transgenic mouse model of cutaneous adnexal tumors.

TMEM207 was first characterized as being an important molecule for the invasion activity of gastric signet-ring cell carcinoma cells. In order to unravel the pathological properties of TMEM207, we generated several transgenic mouse lines, designated C57BL/6-Tg (ITF-TMEM207), in which murine TMEM207 was ectopically expressed under a truncated (by ~200 bp) proximal promoter of the murine intestinal trefoil factor (ITF) gene (also known as Tff3). Unexpectedly, a C57BL/6-Tg (ITF-TMEM207) mouse line exhibited a high incidence of spontaneous intradermal tumors with histopathological features that resembled those of various human cutaneous adnexal tumors. These tumors were found in ~14% female and 13% of male 6- to 12-month-old mice. TMEM207 immunoreactivity was found in hair follicle bulge cells in non-tumorous skin, as well as in cutaneous adnexal tumors of the transgenic mouse. The ITF-TMEM207 construct in this line appeared to be inserted to a major satellite repeat sequence at chromosome 2, in which no definite coding molecule was found. In addition, we also observed cutaneous adnexal tumors in three other C57BL/6-Tg (ITF-TMEM207) transgenic mouse lines. We believe that the C57BL/6-Tg (ITF-TMEM207) mouse might be a useful model to understand human cutaneous adnexal tumors.

Abstract B152: MR-based assessment and quantification of cerebral edema in an orthotopic mouse glioma model.

Abstract Introduction: Brain edema is a prominent feature of brain cancer and contributes to neurologic dysfunction and impaired quality of life. While corticosteroids are the standard of care, improved treatments that are more efficacious and reduce side effects are sought after. In discovery of novel therapies for edema, animal brain tumor models that show relevant, reproducible and high incidence of tumor and cerebral edema are needed. Additionally, quantitative, non-invasive methods for detecting and measuring brain tumor associated edema are needed to facilitate therapeutic discovery efforts. In this work, an intracranial U251-luc human glioma model was characterized for edema incidence and progression. MRI-based relaxivity and contrast-enhancement protocols for edema detection and delineation from tumor tissue, were tested and characterized in the model. Methods: Female nude mice were implanted intracranially with 1×10∧6 U251-luc (Luc-mCherry) glioma cells. Tumor volume assessment was performed by manual segmentation of T1-weighted, gadolinium-enhanced anatomical brain images based on the assumption of tumor enhancement due to leaky vessels or compromised blood-brain barrier. Edema assessment was performed by manual segmentation of T2-weighted anatomical brain images based on the assumption that enhancing regions include tumor tissue in addition to regions of brain edema. The difference in T2-weighted and T1-weighted volumes was assumed to be edema. T2 maps were also generated over the whole brain to measure T2 values over the respective regions of interest, and confirm the differentiation between tumor tissue and edema. Results: Edema volume was successfully distinguished from contrast enhancing tumor tissue and quantified in orthotopically implanted U251-luc (Luc-mCherry) glioma. Incidence was 100%. Edema progression occurred with increasing tumor volume over time. Regions of edema exhibited greater T2 values compared to tumor tissue regions (that also had greater T2 than normal tissue). This is consistent with edematous tissue water content, compared with tumor tissue and normal brain. These results support the use of intracranial U251-luc (Luc-mCherry) as a reliable model for studying the effects of therapies targeting tumor-related cerebral edema, and the application of MR imaging for quantifying those effects real-time in vivo. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):B152. Citation Format: Deanne R. Lister, Deepa Balagurunathan, Meridith Baugher, Erin Trachet, Patrick McConville, Scott Wise, W.R. Leopold. MR-based assessment and quantification of cerebral edema in an orthotopic mouse glioma model. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr B152.

Prognostic Factors in Elderly Osteosarcoma Patients: A Multi-institutional Retrospective Study of 86 Cases

The occurrence of osteosarcoma in elderly patients has recently been increasing, and the outcome is poor. This multi-institutional retrospective study was conducted to investigate clinical features and prognostic factors in patients older than 40 years with osteosarcoma. Patients with conventional high-grade osteosarcoma older than 40 years were recruited to this study. Secondary osteosarcoma arising from Paget's disease or irradiated bones was excluded. Information on tumor- and treatment-related factors was collected and statistically analyzed. The median follow-up was 57 months (range 8-244 months) for all surviving patients. A total of 86 patients were enrolled in this study. The median age at diagnosis was 61 years. Surgery and chemotherapy were conducted in 73 and 63 % of all patients, respectively. The 5-year overall and event-free survival rates were 38.8 and 34.0 %, respectively. Tumor site (extremity 57.9 %; axial 19.0 %; p < 0.0001), metastasis at diagnosis (yes 12.2 %; no 48.3 %; p < 0.0091), and definitive surgery (yes 56.2 %; no 10.6 %; p < 0.0001) were associated with overall survival. Although patients without metastasis who received definitive surgery were regarded as good candidates for chemotherapy, the addition of chemotherapy did not have any impact on the outcome (yes 63.4 %; no 65.2 %; p = 0.511). The present study revealed the distinct clinical features, such as the high incidence of truncal tumors or metastasis at diagnosis, in patients older than 40 years with osteosarcoma. Additionally, prognostic factor analyses revealed that tumor site, metastasis at diagnosis, definitive surgery, and surgical margins were significant prognostic factors, whereas chemotherapy did not influence survival.

Disruption of DNA methylation via S-adenosylhomocysteine is a key process in high incidence liver carcinogenesis

Modifications in histologically normal tissue distal to tumours are increasingly evident and the role of such molecular events in tumour susceptibility or in response to presence of a tumour is unclear. We have exploited the ability to explain distal tissue modifications in the dab fish (Limanda limanda) which has an unprecedented high occurrence of hepatic adenoma (up to 20%) when analysed from the natural environment. To investigate this, three tissue categories of hepatocellular adenoma, histologically normal liver tissue distal to tumours and livers of non-tumour-bearing dab were used. A multi-“omics” approach was used to provide a comprehensive understanding of the key molecular abnormalities. A remarkable and consistent global hypomethylation, modification of CpG island methylation, gene expression and disruption of one-carbon metabolism was discovered in normal tissue distal to tumours compared to livers of non-tumour-bearing fish. The mechanism of this disruption is linked, not to depletion of S-adenosylmethionine, as is often a feature of mammalian tumours, but to a decrease in choline and elevated S-adenosylhomocysteine, a potent inhibitor of DNA methytransferase. This novel feature of normal-appearing tissue of tumour-bearing fish helps to understand the unprecedentedly high incidence of tumours in fish sampled from the field and adds weight to the controversial epigenetic progenitor model of tumourigenesis.

Nested Stromal Epithelial Tumor of the Liver in Beckwith-Wiedemann Syndrome

ABSTRACT Beckwith-Wiedemann syndrome (BWS) is an imprinting disorder characterized by overgrowth, congenital malformation, and tumor predisposition. Children with BWS have a higher incidence of tumors, commonly intra-abdominal tumors such as Wilms tumor, hepatoblastoma, and adrenal cortical carcinoma. Here, we describe the first case of a rare hepatic malignancy of nested stromal epithelial tumor (NSET) of the liver in a child with BWS. A 22-month old girl with BWS had a new incidental liver mass. Her alpha-fetoprotein levels were normal. She underwent a liver segmentectomy. Histopathologic features combined with immunohistochemistry results (positivity for pankeratin [AE1/3], CD56, CK19, CD117, CD99 [weak membranous pattern], β-catenin, and WT1-COOH [focal]), were diagnostic of NSET of the liver. This is the first case of NSET of the liver associated with BWS. Its occurrence at such an early age is consistent with the tumor predisposition of BWS.

Disruption of DNA Methylation viaS-Adenosylhomocysteine Is a Key Process in High Incidence Liver Carcinogenesis in Fish

Interactions between epigenome and the environment in biology and in disease are of fundamental importance. The incidence of hepatocellular adenomas in flatfish exceeds 20% in some environments forming a unique opportunity to study environmental tumorigenesis of general relevance to cancer in humans. We report the novel finding of marked DNA methylation and metabolite concentration changes in histopathologically normal tissue distal to tumors in fish liver. A multi-"omics" discovery approach led to targeted and quantitative gene transcription analyses and metabolite analyses of hepatocellular adenomas and histologically normal liver tissue in the same fish. We discovered a remarkable and consistent global DNA hypomethylation, modification of DNA methylation and gene transcription, and disruption of one-carbon metabolism in distal tissue compared to livers of non-tumor-bearing fish. The mechanism of this disruption is linked not to depletion of S-adenosylmethionine, as is often a feature of mammalian tumors, but to a decrease in choline and elevated S-adenosylhomocysteine, a potent inhibitor of DNA methyltransferase. This novel feature of normal-appearing tissue of tumor-bearing fish helps to understand the unprecedentedly high incidence of tumors in fish sampled from the field and adds weight to the controversial epigenetic progenitor model of tumorigenesis. With further studies, the modifications may offer opportunities as biomarkers of exposure to environmental factors influencing disease.

A population-based study of tumours of the renal pelvis and ureter: Incidence, aetiology and histopathological findings

Objective. Carcinoma of the renal pelvis and ureter are unusual tumours and our limited knowledge comes mainly from case reports and small series from large academic hospitals, as a rule without histopathological review. This study reports aetiological and demographical factors as well as clinicopathological findings of all patients in a large geographical region. Material and methods. All patients in western Sweden with a renal pelvic or ureteral tumour diagnosed between 1971 and 1998 (n = 930) were included. Untreated cases were not excluded. Demographic data and results of preoperative examinations were retrieved from the original clinical records. The histopathological slides were reviewed and tumour stage, grade, configuration, presence of carcinoma in situ and angiolymphatic invasion were determined Results. The majority of patients (80%) had invasive or high-grade tumours. Carcinoma in situ was present among 30% of patients with non-invasive high-grade tumours. Angiolymphatic invasion (62%) and solid (non-papillary) growth pattern (84%) were very common among patients with stage T2–T4 tumours. Twenty-three women out of 138 (16.7%) with ureteral carcinoma had a history of abdominal radiotherapy for gynaecological cancer 22 years (median) earlier. Forty-one patients out of 930 (4.4%) had a history of abuse of phenacetin-containing analgesics. Conclusions. This study demonstrates a very high incidence of high-grade upper tract tumours with carcinoma in situ, angiolymphatic invasion and solid (non-papillary) growth pattern, which underscores the malignant character of the disease. The possible association between pelvic radiotherapy and ureteral carcinoma warrants further study.

Mycotoxins and fish farming: A risk left behind?

Mycotoxins produced by various fungi of the genera Aspergillus, Fusarium and Penicillium can easily contaminate cereals, their by-products and many plant and animal products commonly used for manufacturing industrial and homemade fish feed. The most common are: aflatoxins, ochratoxin A, zearalenone and trichothecenes. However, information on the impact of mycotoxins is still scarce, most of it coming from experimental studies. The toxicological effects of mycotoxins on fish depend on the type of mycotoxin and on the relationship between dose and exposure to which the fish are subjected. Subchronic intoxication usually results in decreasing rates of growth, changes in the general condition of the fish, specific lesions in various organs including the liver, immunosuppression and an increased occurrence of opportunistic pathogens. Aflatoxins are often associated with a high incidence of liver tumours. However, significant variations in toxicity are related to various factors, including the species and age of the fish in question. This article provides an overview of the issues related to mycotoxins in fish farming and presents the necessary actions to be undertaken in order to reduce their effects with emphasis on the multifactorial aspects of these contaminants.

Connecting molecular pathways to hereditary cancer risk syndromes.

An understanding of the genetic causes and molecular pathways of hereditary cancer syndromes has historically informed our knowledge and treatment of all types of cancers. For this review, we focus on three rare syndromes and their associated genetic mutations including BAP1, TP53, and SDHx (SDHA, SDHB, SDHC, SDHD, SDHAF2). BAP1 encodes an enzyme that catalyzes the removal of ubiquitin from protein substrates, and germline mutations of BAP1 cause a novel cancer syndrome characterized by high incidence of benign atypical melanocytic tumors, uveal melanomas, cutaneous melanomas, malignant mesotheliomas, and potentially other cancers. TP53 mutations cause Li-Fraumeni syndrome (LFS), a highly penetrant cancer syndrome associated with multiple tumors including but not limited to sarcomas, breast cancers, brain tumors, and adrenocortical carcinomas. Genomic modifiers for tumor risk and genotype-phenotype correlations in LFS are beginning to be identified. SDH is a mitochondrial enzyme complex involved in the tricarboxylic acid (TCA) cycle, and germline SDHx mutations lead to increased succinate with subsequent paragangliomas, pheochromocytomas, renal cell carcinomas (RCCs), gastrointestinal stromal tumors (GISTs), and other rarer cancers. In all of these syndromes, the molecular pathways have informed our understanding of tumor risk and successful early tumor surveillance and screening programs.

Ataxia-Telangiectasia and Wilms Tumor

Ataxia-telangiectasia (A-T) is an autosomal recessive disease characterized by progressive cerebellar ataxia, oculocutaneous telangiectasia, immunodeficiency, a high incidence of lymphoreticular tumors, and an increased sensitivity to chemoradiotherapy-induced DNA damage. The appropriate cancer therapy remains unknown because of high toxicity rates with full-dose conventional protocols. We present a patient with A-T and nephroblastoma, who received an adapted treatment regimen. To our knowledge this is the second report on nephroblastoma in a patient with A-T but the first with confirmed premortem studies. Although the patient tolerated the chemotherapy regimen well, the patient relapsed and died a year after initial diagnosis.

Abstract 428: Decreased RXRα dampened APC-independent proteosomal targeting of β-catenin to cause increased intestinal tumorigenesis after 56-Fe radiation.

Abstract Purpose: Radiation exposure is a risk factor for colorectal cancer (CRC) and high linear energy transfer radiation (high-LET) radiation such as 56-Fe in outer space is expected to pose greater risk of CRC to space travelers. Earlier, we have reported increased intestinal tumorigenesis in heavy ion radiation (HZE) exposed APCMin/+ mice, a well studied model of CRC, and higher tumor incidence was due to increased stabilization and activation of β-catenin signaling after 56-Fe radiation exposure. However the molecular mechanism behind β-catenin activation is not yet explored. Levels of β-catenin are tightly regulated through its targeting to proteasomal degradation mediated via adenomatous polyposis coli (APC) dependent and independent pathways. The APC independent pathway of β-catenin degradation is facilitated via retinoid-X receptor alpha (RXRα). The present study aimed to investigate alterations in RXRα mediated proteasomal pathways in intestinal tumors induced by 56Fe relative to γ radiation. Materials and Methods: Six to eight weeks old female APCMin/+ mice (n=6 mice/ group) were irradiated with 5 Gy of gamma and isotoxic doses of 56Fe (4 Gy, energy: 1 GeV/nucleon; LET: 148 keV/μ) radiation. Mice were euthanized between 100 and 110 days after radiation and intestinal tumor samples were collected. Tumor samples were analyzed to deliniate the 56-Fe-induced changes in RXRα-proteasomal pathways using activity assays, Western blot and immunohistochemistry (IHC). Results: Higher proteasomal activity was observed in 56Fe-induced tumors accompanied with increased expression of proteasomal subunit 20S-β and increased expression/activation of proteosomal activator-200 (PA200) compared to γ radiation. However, we found decreased phosphorylation and consequent reduction in ubiquitination of β-catenin, leading to its increased cellular level in 56Fe relative to gamma radiation-induced tumors. We also show both by Western blot as well as IHC that exposure to 56-Fe radiation led to decreased RXRα expression, a key element in the APC-independent β-catenin degradation pathway. Conclusions: Although 56Fe radiation led to elevated proteasomal activity via overexpression of proteasomal subunit and its activator, we observed increased rather than decreased active β-catenin. We propose that increased β-catenin activity and consequent higher frequency of intestinal tumors is due to the inability of not only the APC-dependent but also the APC-independent RXRα-mediated pathway to facilitate ubiquitination of β-catenin and its subsequent proteasomal degradation. Taken together our study shows for the first time that 56-Fe radiation exposure modulates β-catenin stability in an APC-independent manner to promote intestinal tumorigenesis. Citation Format: Shubhankar Suman, Kamal Datta, Albert J. Fornace. Decreased RXRα dampened APC-independent proteosomal targeting of β-catenin to cause increased intestinal tumorigenesis after 56-Fe radiation. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 428. doi:10.1158/1538-7445.AM2013-428

Abstract 1581: Tumor suppressor functions of the zebrafish ink4ab: a novel cyclin-dependent kinase inhibitor.

Abstract The human INK4b-ARF-INK4a genetic locus encodes two closely related members of the INK4 family of cyclin dependent kinase inhibitors, p15INK4b and p16INK4a regulating RB phosphorylation and subsequently cell proliferation, and a p53 stabilizer, known as ARF. All of the three products play a pivotal role in tumor suppression and are frequently deleted or inactivated in a wide spectrum of human cancers. Despite the critical role of the mammalian INK4b-ARF-INK4a locus in tumor suppression, its counterpart in zebrafish has not yet been characterized. Zebrafish is an advantageous vertebrate to model human cancers, specifically because of the high fecundity, the ease of performing high-throughput screens, and the genetic conservation with mammals. We identified a syntenic zebrafish ink4ab locus that consists of a single gene orthologous to both mammalian CDKN2a (INK4A) and CDKN2b (INK4B), and functions to activate senescence in response to oxidative stress. Utilizing morpholino targeted knockdown and zebrafish mutants for the ink4ab gene, we have developed a zebrafish model for tumorigenesis. We demonstrate that the zebrafish ink4ab gene functions as a tumor suppressor by controlling cell cycle regulation under stress. Senescence was activated by oxidative stress in wild type embryos but not in embryos with ink4ab deficiency when examined with a whole embryo senescence-associated beta-galactosidase (SA-β-gal) assay. Surprisingly, we find that ink4ab deficient embryos also display significantly higher levels of apoptosis than controls. We determined that the apoptosis associated with ink4ab deficiency is p53-dependent. Furthermore, ink4ab deficiency led to significantly lower survival rates, both overall and upon radiation. Ink4ab deficient zebrafish had splenomegaly, increased lymphocyte proliferation, and developed spontaneous tumors including metastatic melanoma, osteosarcoma, leukemia and myelodysplastic disorders. Thus, the zebrafish ink4ab protein functions as a tumor suppressor similarly to the human p15INK4B and p16INK4A. To study the upstream control of zebrafish ink4ab expression, we investigated the orchestrated regulation by the Bmi-1 oncogene, and identified bmi-1a as a repressor of ink4ab expression. Zebrafish heterozygous for both p53 and ink4ab mutations displayed significantly higher tumor incidence compared to p53 heterozygotes with wild-type ink4ab, indicating that ink4ab haploinsufficiency promotes tumorigenesis. To this end, the combined deficiency of ink4ab and p53 accelerates the latency and broadens the tumor spectrum including the formation of retinoblastoma. Collectively, the zebrafish ink4ab model of tumor suppression provides a platform to perform large-scale screens for small molecules that modulate tumorigenesis in the ink4ab deficient fish, and permit defining the genetic pathways of CDKN2a- and CDKN2b-mediated tumor suppression. Citation Format: Stephani Davis, Hatem E. Sabaawy. Tumor suppressor functions of the zebrafish ink4ab: a novel cyclin-dependent kinase inhibitor. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1581. doi:10.1158/1538-7445.AM2013-1581

Connecting Molecular Pathways to Hereditary Cancer Risk Syndromes

An understanding of the genetic causes and molecular pathways of hereditary cancer syndromes has historically informed our knowledge and treatment of all types of cancers. For this review, we focus on three rare syndromes and their associated genetic mutations including BAP1, TP53, and SDHx (SDHA, SDHB, SDHC, SDHD, SDHAF2). BAP1 encodes an enzyme that catalyzes the removal of ubiquitin from protein substrates, and germline mutations of BAP1 cause a novel cancer syndrome characterized by high incidence of benign atypical melanocytic tumors, uveal melanomas, cutaneous melanomas, malignant mesotheliomas, and potentially other cancers. TP53 mutations cause Li-Fraumeni syndrome (LFS), a highly penetrant cancer syndrome associated with multiple tumors including but not limited to sarcomas, breast cancers, brain tumors, and adrenocortical carcinomas. Genomic modifiers for tumor risk and genotype-phenotype correlations in LFS are beginning to be identified. SDH is a mitochondrial enzyme complex involved in the tricarboxylic acid (TCA) cycle, and germline SDHx mutations lead to increased succinate with subsequent paragangliomas, pheochromocytomas, renal cell carcinomas (RCCs), gastrointestinal stromal tumors (GISTs), and other rarer cancers. In all of these syndromes, the molecular pathways have informed our understanding of tumor risk and successful early tumor surveillance and screening programs.

腹腔鏡下性腺摘出術を施行した性分化疾患の3例

Disorders of sex development (DSD) are defined as congenital conditions in which development of chromosomal, gonadal, or anatomic sex is atypical. In some cases of DSD, especially 46,XY DSD and Turner syndrome (+Y), early bilateral gonadectomy is recommended; this recommendation is based upon the high incidence of gonadal tumors in affected individuals. Because these cases are frequently found in younger women, laparoscopic surgery is an excellent choice for minimally invasive treatment. We performed a prophylactic laparoscopic gonadectomy on three patients at the appropriate time after carefully determining the correct diagnosis.

Dietary selenium fails to influence cigarette smoke-induced lung tumorigenesis in A/J mice

The goal of the study was to determine if dietary selenium inhibited the induction of lung tumorigenesis by cigarette smoke in A/J mice. Purified diets containing 0.15, 0.5, or 2.0mg/kg selenium in the form of sodium selenite were fed to female A/J mice. Half of the mice in each dietary group were exposed to cigarette smoke 6h/day, 5days/week for five months followed by a four month recovery period in ambient air, while the other half were used as controls. After the recovery period, the mice were euthanized, and their lungs were removed for further analysis. Mice exposed to smoke had a higher tumor incidence and a higher tumor multiplicity, whereas dietary Se did not affect either the tumor incidence or tumor multiplicity. An increase in dietary selenium led to increased levels of selenium in the lung as well as GPx protein levels, but dietary Se did not affect lung SOD protein levels. In conclusion, these data confirm the carcinogenic activity of cigarette smoke in mice but show that dietary Se provided as sodium selenite does not affect smoke-induced carcinogenesis in this model.