Gene amplification is one of the common mechanisms that activate oncogenes. In this study, we used single nucleotide polymorphism array to analyze genome-wide DNA copy number alterations in 31 high-grade ovarian serous carcinomas, the most lethal gynecologic neoplastic disease in women. We identified an amplicon at 19p13.12 in 6 of 31 (19.5%) ovarian high-grade serous carcinomas. This amplification was validated by digital karyotyping, quantitative real-time PCR, and dual-color fluorescence in situ hybridization (FISH) analysis. Comprehensive mRNA expression analysis of all 34 genes within the minimal amplicon identified Notch3 as the gene that showed most significant overexpression in amplified tumors compared with nonamplified tumors. Furthermore, Notch3 DNA copy number is positively correlated with Notch3 protein expression based on parallel immunohistochemistry and FISH studies in 111 high-grade tumors. Inactivation of Notch3 by both γ-secretase inhibitor and Notch3-specific small interfering RNA suppressed cell proliferation and induced apoptosis in the cell lines that overexpressed Notch3 but not in those with minimal amount of Notch3 expression. These results indicate that Notch3 is required for proliferation and survival of Notch3-amplified tumors and inactivation of Notch3 can be a potential therapeutic approach for ovarian carcinomas. (Cancer Res 2006; 66(12): 6312-8)

Notch3 gene amplification and pathway activation have been reported in ovarian serous carcinoma. However, the primary Notch3 ligand that initiates signal transduction in ovarian cancer remains unclear. In this report, we identify Jagged-1 as the highest expressed Notch ligand in ovarian tumor cells as well as in peritoneal mesothelial cells that are in direct contact with disseminated ovarian cancer cells. Cell-cell adhesion and cellular proliferation were reduced in Notch3-expressing ovarian cancer cells that were cocultured with Jagged-1 knockdown mesothelial and tumor feeder cells. Interaction of Notch3-expressing ovarian cancer cells with Jagged-1–expressing feeder cells activated the promoter activity of candidate Notch3 target genes, and this activity was attenuated by Notch3 siRNA. Constitutive expression of the Notch3 intracellular domain significantly suppressed the Jagged-1 shRNA–mediated growth inhibitory effect. In Notch3-expressing ovarian cancer cells, Jagged-1–stimulating peptides enhanced cellular proliferation, which was suppressed by γ-secretase inhibitor and Notch3 siRNA. Taken together, our results show that Jagged-1 is the primary Notch3 ligand in ovarian carcinoma and Jagged-1/Notch3 interaction constitutes a juxtacrine loop promoting proliferation and dissemination of ovarian cancer cells within the intraperitoneal cavity. [Cancer Res 2008;68(14):5716–23]

Notch3 gene amplification has recently been identified in ovarian cancer but the Notch3 effectors that are involved in the development of ovarian cancer remain elusive. In this study, we have identified Pbx1, a proto-oncogene in hematopoietic malignancy, as a Notch3 target gene. Pbx1 expression is transcriptionally regulated by Notch3 activation, and Notch3/CSL protein complex directly binds to the Pbx1 promoter segment harboring the CSL-binding sequence. The growth-inhibitory effect of γ-secretase inhibitor could be partially reversed by ectopic Pbx1 expression. Furthermore, functional studies by Pbx1 short hairpin RNA knockdown show that Pbx1 is essential for cell proliferation and tumorigenicity. Taken together, the above findings indicate that Pbx1 is a direct Notch3-regulated gene that mediates the survival signal of Notch3 in ovarian cancer. [Cancer Res 2008;68(21):8852–60]

Background Pancreas development in zebrafish shares many features with mammals, including the participation of epithelial progenitor cells expressing pancreas transcription factor 1a (ptf1a). However, to date it has remained unclear whether, as in mammals, ptf1a-expressing zebrafish pancreatic progenitors are able to contribute to multiple exocrine and endocrine lineages. To delineate the lineage potential of ptf1a-expressing cells, we generated ptf1a:creERT2 transgenic fish and performed genetic-inducible lineage tracing in developmental, regenerating, and ptf1a-deficient zebrafish pancreas. Results In addition to their contribution to the acinar cell lineage, ptf1a-expressing cells give rise to both pancreatic Notch-responsive-cells (PNCs) as well as small numbers of endocrine cells during pancreatic development. In fish with ptf1a haploinsufficiency, a higher proportion of ptf1a lineage-labeled cells are traced into the PNC and endocrine compartments. Further reduction of ptf1a gene dosage converts pancreatic progenitor cells to gall bladder and other non-pancreatic cell fates. Conclusions Our results confirm the presence of multipotent ptf1a-expressing progenitor cells in developing zebrafish pancreas, with reduced ptf1a dosage promoting greater contributions towards non-acinar lineages. As in mammals, loss of ptf1a results in conversion of nascent pancreatic progenitor cells to non-pancreatic cell fates, underscoring the central role of ptf1a in foregut tissue specification.