Expression of an activated Notch-related int-3 transgene interferes with cell differentiation and induces neoplastic transformation in mammary and salivary glands.

Abstract

Expression of the int-3 locus is activated in mouse mammary tumors as a consequence of insertional mutagenesis by the mouse mammary tumor virus (MMTV). Integration of the MMTV pro virus into the int-3 locus promotes the transcription and translation of flanking cellular int-3 sequences sharing significant homology with the intracellular domain of the neurogenic Notch gene of Drosophila, and with the yeast cell cycle regulatory genes cdclO and SWI6. To determine the in vivo consequences of activated int-3 expression, transgenic mice were generated harboring a genomic tumor DNA fragment consisting of the MMTV LTR and the flanking cellular int-3 sequences. All six int-3 founder transgenic mice and the progeny of one established line exhibited similar dramatic phenotypic abnormalities in tissues in which the transgene was expressed. Focal and often multiple poorly differentiated mammary and salivary adenocarcinomas appeared in the majority of transgenic mice between 2 and 7 months of age. Significantly, mammary glands were arrested in development and were lactation deficient in all female int-3 mice. The salivary glands, glands of the nasal mucosa and maxillary sinus, the extraorbital lacrimal glands, and the Harderian glands of juvenile and adult transgenic mice all contained proliferating immature ductule cells and were incompletely differentiated. In addition, all male int-3 transgenic mice were sterile, apparently the result of severe hyperplasia of the epididymis. These findings demonstrate in vivo that expression of the activated NotcA-related int-3 gene causes deregulation of normal developmental controls and hyperproliferation of glandular epithelia.

The lymphovascular embolus of inflammatory breast cancer exhibits a Notch 3 addiction

“…The effects of Notch 3 knockdown were identical to the effects of g-secretase inhibition in vitro, namely decreased expression of Notch 3 targets and profound apoptosis. It had been shown previously that Notch signaling can regulate apoptosis (Jhappan et al, 1992;Hu et al, 2006;Klinakis et al, 2006). Results of our in vitro studies were cleaner than our in vivo results that relied on the diffusion of a drug, in this case, GSI-I.…”

Identification of a novel NOTCH-4/INT-3 RNA species encoding an activated gene product in certain human tumor cell lines

“…et al (1998) have shown that activated NOTCH-4/INT-3 expression in the mouse mammary epithelial TAC-2 cell line inhibits its capability to undergo branching morphogenesis. In transgenic mouse strains expressing activated NOTCH-4/INT-3 ICD there is a profound alteration in mammary gland development including a 100% penetrance for mammary tumor development (Gallahan et al, 1996;Jhappan et al, 1992;Smith et al, 1995). In Drosophila, signaling by activated Notch is mediated through the interaction between the Notch ICD and the transcription factor, suppressor of hairless (Su(H)) (reviewed in Artavanis-Tsakonas et al, 1999).…”

“…The transforming rearrangement of NOTCH-4/ INT-3 results from the expression of the intracellular domain of the gene product under control of the MMTV promoter and represents a gain-of-function mutation. Expression of this`activated' form of NOTCH-4/INT-3 in transgenic mice under the control of either the MMTV long terminal repeat (LTR) or the Whey Acidic Protein (WAP) promoter leads to a severe impairment of mammary gland function and to the development of mammary adenocarcinomas (Gallahan et al, 1996;Jhappan et al, 1992;Smith et al, 1995).…”

The Notch signaling pathway: Transcriptional regulation at Notch target genes

“…Notch-4 was first identified as a proviral integration sites, named int-3, in retrovirus-induced murine mammary cancer [156]. Whether Notch4 plays a genuine role in normal mammary development remains unclear so far.…”