Creating Models to Identify New Therapeutic Options for Aggressive African Breast Cancers

Background: Population-based incidence rates of breast cancer (BC) that does not express the estrogen receptor (ER), progesterone receptor (PR) or overexpress the human epidermal growth factor 2 HER2/ neu (triple negative breast cancer, TNBC) are higher among Africans compared with white women. However the underlying biologic and genetic differences among different ethnicities are poorly understood and there are currently very few ethnically diverse BC models available for identifying new therapeutic options. Aim: Establish an international collaboration to: i, characterize African breast tumors ii, create models for studying these tumors and iii, identify biomarkers for early detection and treatment personalization. Methods: We have collected tumors from 154 white Americans WA, 76 African Americans, AA, 190 Ethiopians, Eth, and 286 Ghanaian (Gh) BC patients. We then established a unique resource of patient derived xenografts (PDX) from these tumors. The PDXs were then fully characterized using whole exome and RNA sequencing for the primary tumor, matched normal DNA, and corresponding low passage PDXs. Using immunohistochemistry, we evaluated the ER, PR, HER2/ neu, androgen receptor (AR), and ALDH1 (cancer stem cell marker) expression among these tumors. Based on biomarker expression the PDXs were then tested against a panel of IND drugs, either alone or in combinations, in an ex vivo organoid culture system to discover potential new therapeutic options. Results: Mean age at BC diagnosis was 43; 49; 60; and 57 years for the Eth; Gh; AA; and WA patients, respectively. The proportion of TNBC was significantly higher for the AA and Gh patients (41% and 54%, respectively) compared with the WA and Eth patients (23% and 15%, respectively); P < 0.001. Significant differences were observed for distribution of AR positivity, which was 71%; 55%; 42% and 50% for the WA; AA; Gh; and Eth cases, respectively ( P = 0.008). The Gh breast tumors exhibited the highest number of loss of function and missense mutations that are likely to impact therapy with a high frequency of P53, APC, and FGFR mutations. These mutations were maintained in the corresponding PDXs that were developed, and were thus used as biomarkers for drug screening. These tumors exhibited a gene expression signature based on the ethnicity of the patients with 2385 genes differentially expressed between Gh and AA, 1573 between AA and CA and 1317 between GH and CA. Results from our ongoing drug screening and biomarker identification will be available soon. Conclusions: Establishing the molecular and genetic platform of aggressive breast cancers occurring in women with African ancestry will help in identifying biomarkers for early cancer detection and targeted treatment stratification for optimum patient outcome. The availability of tumor models based on tumors from diverse African populations is the important missing pieces that have to be incorporated into current drug discovery efforts.

Copper-Associated Hepatopathy in a Mexican Fruit Bat (Artibeus Jamaicensis) and Establishment of a Reference Range for Hepatic Copper in Bats

Copper toxicity has been described in numerous domestic species. The characteristic lesions include hemoglobinuric nephrosis and piecemeal hepatic necrosis with bile ductular hyperplasia and portal fibrosis. Certain species, such as sheep, are prone to toxicity when exposed to copper in feed, whereas an inherent genetic defect of copper storage is present in some breeds of dogs (Bedlington Terriers, West Highland White Terriers, Doberman Pinschers). In nondomestic species, reference ranges have not been established for copper in internal organs, so the establishment of copper toxicity as a diagnosis is difficult. A case of copper toxicity in a captive Mexican fruit bat is presented. Hepatic copper levels in 16 additional bats, of at least 3 different species, were measured. To the authors' knowledge, this is the first reported case of copper toxicity in a chiropteran.

GATA3 inhibits lysyl oxidase-mediated metastases of human basal triple-negative breast cancer cells

Discovery of mechanisms that impede the aggressive and metastatic phenotype of human basal triple-negative type breast cancers (BTNBC) could provide novel targets for therapy for this form of breast cancer that has a relatively poor prognosis. Previous studies have demonstrated that the expression of GATA3, the master transcriptional regulator of mammary luminal differentiation, can reduce the tumorigenicity and metastatic propensity of the human BTNBC MDA-MB-231 cell line (MB231), although the mechanism for reduced metastases was not elucidated. We demonstrate through gene expression profiling that GATA3 expression in 231 cells resulted in the dramatic reduction in the expression of Lysyl oxidase (LOX), a metastasis-promoting matrix remodeling protein, in part, through methylation of the LOX promoter. Suppression of LOX expression by GATA3 was further confirmed in the BTNBC Hs578T cell line. Conversely, reduction of GATA3 expression by siRNA in luminal BT474 cells increased LOX expression. Reconstitution of LOX expression in 231-GATA3 cells restored metastatic propensity. A strong inverse association between high LOX and low GATA3 expression was confirmed in a panel of 51 human breast cancer cell lines. Similarly, human breast cancer microarray data demonstrated that high LOX/low GATA3 expression is associated with the BTNBC subtype of breast cancer and poor patient prognosis. Expression of GATA3 reprograms BTNBC to a less aggressive phenotype and inhibits a major mechanism of metastasis through inhibition of LOX. Induction of GATA3 in BTNBC cells or novel approaches that inhibit LOX expression or activity could be important strategies for treating BTNBC.

Gene expression and mutation assessment provide clues of genetic and epigenetic mechanisms in liver tumors of oxazepam-exposed mice

Liver tumors from a previous National Toxicology Program study were examined using global gene expression and mutation analysis to define the mechanisms of carcinogenesis in mice exposed to oxazepam. Five hepatocellular adenomas and 5 hepatocellular carcinomas from male B6C3F1 mice exposed to 5000 ppm oxazepam and 6 histologically normal liver samples from control animals were examined. One of the major findings in the study was upregulation of the Wnt/β-catenin signaling pathway. Genes that activate β-catenin, such as Sox4, were upregulated, whereas genes that inhibit Wnt signaling, such as APC and Crebbp, were downregulated. In addition, liver tumors from oxazepam-exposed mice displayed β-catenin mutations and increased protein expression of glutamine synthetase, a downstream target in the Wnt signaling pathway. Another important finding in this study was the altered expression of oxidative stress-related genes, specifically increased expression of cytochrome p450 genes, including Cyp1a2 and Cyp2b10, and decreased expression of genes that protect against oxidative stress, such as Sod2 and Cat. Increased oxidative stress was confirmed by measuring isoprostane expression using mass spectrometry. Furthermore, global gene expression identified altered expression of genes that are associated with epigenetic mechanisms of cancer. There was decreased expression of genes that are hypermethylated in human liver cancer, including tumor suppressors APC and Pten. Oxazepam-induced tumors also exhibited decreased expression of genes involved in DNA methylation (Crebbp, Dnmt3b) and histone modification (Sirt1). These data suggest that formation of hepatocellular adenomas and carcinomas in oxazepam-exposed mice involves alteration of the Wnt signaling pathway, oxidative stress, and potential epigenetic alterations.

Concurrent gastrinoma and somatostatinoma in a 10-year-old Portuguese water dog

Severe hypergastrinaemia in the dog is considered a strong indicator for a gastrin-producing pancreatic islet cell tumour. In human medicine, gastrinomas are described as enteropancreatic neuroendocrine tumours that cause the Zollinger-Ellison syndrome. However, in contrast to the supposed origin of canine gastrinomas in pancreatic islets, gastrinomas in human beings arise predominantly in the duodenum and gastric antrum, and are often a component of the syndrome of multiple endocrine neoplasia type I. This report is of a canine case of multiple endocrine neoplasms, consisting of a pancreatic islet cell somatostatinoma, and a gastrinoma in the mesenteric lymph nodes and liver. From the literature and the authors' findings, it is concluded that the clinical diagnosis of hypergastrinaemia is not pathognomonic for a gastrin-producing islet cell tumour. Furthermore, the presence of an islet cell tumour in the face of hypergastrinaemia does not warrant a diagnosis of an islet cell gastrinoma. Immunohistochemistry is necessary to confirm the diagnosis of a pancreatic islet cell gastrinoma.