Project description:cMET is a well known oncogene whose activation is widely implicated in tumorigenesis and metastasis. To investigate the effects of acute inhibitoin of cMET signaling in the mammary tumors, we inhibited cMET activation in xenograft mammary tumors that were derived from a MET amplified mouse mammary tumor cell line and analyzed the transcriptional alteration between vehicle and MET inhibitor treated tumors.
Project description:Gain-of-function mutation of PIK3CA represents one of the most common oncogenic events in human malignancy, making PI3K an attractive target for cancer therapy. Despite the great promise of targeted therapy, drug resistance is likely to develop, causing treatment failure. To elucidate resistance mechanisms to PI3K-targeted therapy, we constructed a mouse model of breast cancer conditionally expressing PIK3CA-H1047R. Surprisingly, the majority of mammary tumors induced by PIK3CA-H1047R expression recurred following PIK3CA-H1047R inactivation. Genomic analyses of recurrent tumors revealed multiple lesions, including spontaneous focal amplification of c-Met or c-Myc. While amplification of c-Met allowed tumor survival dependent on activation of endogenous PI3K, tumors with amplification of c-Myc become independent of the PI3K pathway. Functional analyses further demonstrated that c-Myc contributed to tumors’ independence of oncogene and resistance to PI3K inhibition. Together, our data suggest that MYC elevation in tumors may be a potential mechanism conferring resistance to current PI3K-targeted therapies. Affymetrix SNP array analysis was performed with Mouse Diversity Genotyping Arrays (Affymetrix) on genomic DNA extracted from frozen biopsies of 6 recurrent mouse mammary tumor samples. Copy number analysis was performed for the mouse mammary tumors using genomic DNA from normal mammary tissue as the reference for copy number inference.
Project description:miRNA profiling of normal and tumorigenic mouse mammary tissue. Mouse genotypes consist of wildtype, MMTV-Met, MMTV-Met;Trp53fl/+;Cre, and Trp53fl/+;Cre. One-color design. Samples consist of 2 normal tissues, 7 MMTV-Met tumors, 8 MMTV-Met;Trp53fl/+;Cre tumors, and 8 Trp53;Cre tumors.
Project description:Transcriptional profiling of normal and tumorigenic mouse mammary tissue. Mouse genotypes consist of wildtype, MMTV-Met, MMTV-Met;Trp53fl/+;Cre, and Trp53fl/+;Cre. Two-color common reference design. Samples consist of 11 normal tissues, 8 MMTV-Met tumors, 14 MMTV-Met;Trp53fl/+;Cre tumors, and 8 Trp53;Cre tumors.
Project description:Transcriptional profiling of normal and tumorigenic mouse mammary tissue. Mouse genotypes consist of wildtype, MMTV-Met, MMTV-Met;Trp53fl/+;Cre, and Trp53fl/+;Cre. Two-color common reference design. Samples consist of 4 normal tissues, 8 MMTV-Met tumors, 10 MMTV-Met;Trp53fl/+;Cre tumors, and 8 Trp53;Cre tumors.
Project description:Breast cancer is the second leading cause of cancer related death in American women. Patient care is complicated by inherent tumor heterogeneity that can be classified into at least six intrinsic subtypes. While targeted treatments are standard of care for most subtypes, there remains a clinical need for targeted therapies against basal-like tumors that are typically ‘triple negative breast cancers’. As such, the molecular mechanisms underlying basal-like tumors are under intense investigation to identify genetic drivers and possible drug targets of this subtype. Somatic p53 mutations are one of the most common genetic events in basal-like breast tumors. This genetic foundation primes cells to accumulate secondary genetic aberrations, a subset of which is predicted to promote tumorigenesis. To identify additional drivers of basal-like tumors, a comparative study between human and murine tumors was performed utilizing a p53null mammary transplant murine model. The p53null mammary transplant murine model produced a genomically diverse set of tumors, a subset of which we show resemble the human basal-like subtype. Microarray and sequencing technologies were used to interrogate the secondary genetic aberrations of these murine tumors which were then compared to human basal-like tumors to highlight conserved features. Of the ‘omic’ datasets analyzed, DNA copy number variation produced the largest number of conserved candidate driver genes. These candidate gene lists were further filtered using a DNA-RNA Pearson correlation cutoff of 0.5 and a requirement that the gene was deemed essential in at least one human basal-like cell line from a genome-wide RNA-mediated interference screen database. These steps highlighted seven potential driver genes that are at amplified loci in both murine and human basal-like tumors: Atp11a, Col4a2, Cul4a, Lamp1, Met, Pnpla6, and Tubgcp3. Inhibition of Met using Crizotinib caused Met amplified tumors to regress, confirming that this genetic event is a driver in a subset of p53null transplant mammary tumors. This study identifies MET as a driver of basal-like murine tumors, thus identifying a shared potential driver of human basal-like breast cancer. Our results also highlight the importance of comparative genomic studies for discovering drug targets and for providing models to study whether patient populations are likely to respond to selective targeted treatments.
Project description:SUMMARY: Basal breast cancer has been associated with mutations in a number of specific tumor suppressor genes, however, the mechanism by which these tumors express a basal lineage remains unknown. Notch signaling suppresses mammary stem cell (MaSC) self-renewal, while promoting luminal cell fate specification. Here we show that Lfng, a sugar transferase that facilitates Notch activation, suppresses mammary stem/bipotent progenitor cell proliferation. Targeted deletion of Lfng in mammary epithelium induces basal tumors with reduced expression of Notch targets, amplification of the Met/Caveolin gene locus, and elevated Met and Igf-1R signaling. Human basal breast cancer, a disease associated with elevated MET receptor signaling and Caveolin protein, express low levels of LFNG. Thus, reduced LFNG expression cooperates with a Met/ Caveolin amplicon to promote basal breast disease. SIGNIFICANCE: Anti-Notch therapy is currently being tested for efficacy against basal-like breast cancer in humans. Here we report that LFNG, which controls Notch receptor activation, is consistently expressed at a low level in basal tumors and that deletion of this gene in the mouse mammary gland reduces Notch signaling, increases proliferation and induces basal mammary tumors in cooperation with amplification of the Met/Caveolin gene locus. These mutations interact to promote basal gene expression by decreasing Notch pathway activation, as well as to enhance Met and Igf-1R signaling. These pathways can be targeted at multiple levels in humans harboring basal breast cancer with amplification of MET and CAV1/2 32 array samples
Project description:Tumor recurrence represents a significant clinical challenge in the treatment and management of breast cancer. To investigate whether copy number aberrations (CNAs) facilitate the re-emergence of tumor growth from residual disease we performed array comparative genomic hybridization (aCGH) on primary and recurrent mammary tumors from an inducible mouse model of type-I insulin-like growth factor receptor (IGF-IR) driven breast cancer. This genome-wide analysis revealed primary and recurrent tumors harbored distinct copy number aberrations (CNAs) with relapsed tumors containing an increased number of gene-level gains and losses. Remarkably, CNAs detected in primary tumors were largely devoid of annotated cancer genes while the vast majority of recurrent tumors harbored at least one CNA containing a known oncogene or tumor suppressor. Specifically, a subset of recurrent tumors carried gains at 6qA2 and 9qA2 which encode the Met and Yap1 oncogenes respectively. The most frequent CNA detected was a focal deletion at 4qC5 involving the Cdkn2a and Cdkn2b tumor suppressor genes. Integrative analysis revealed positive correlations between gene copy number and mRNA expression suggesting Met, Yap1 and Cdkn2a/b may serve as potential driver genes that promote tumor recurrence. Together, these findings indicate that tumor recurrence is facilitated by the acquisition of CNAs with oncogenic potential and provide a framework to dissect the molecular mechanisms that mediate tumor escape from dormancy.
Project description:Elevated Met receptor tyrosine kinase (RTK) expression correlates with poor outcome in breast cancer, yet a causal role for Met in the development of breast cancer has not been directly established. To examine this question, we generated a transgenic mouse model that targets expression of an oncogenic Met receptor (MetMut) to the mammary epithelium. We show that MetMut induces mammary tumors with a variety of histopathologies that exhibit gene expression profiles sharing similarities with human basal and luminal breast tumor subtypes. Among all breast cancers, we further demonstrate that the Met receptor is primarily overexpressed in human basal and HER2 positive breast cancers, and that a Met associated gene expression signature identifies patients with poor prognosis. Keywords: Met, mammary, poor outcome, EMT, basal breast cancer
Project description:SUMMARY: Basal breast cancer has been associated with mutations in a number of specific tumor suppressor genes, however, the mechanism by which these tumors express a basal lineage remains unknown. Notch signaling suppresses mammary stem cell (MaSC) self-renewal, while promoting luminal cell fate specification. Here we show that Lfng, a sugar transferase that facilitates Notch activation, suppresses mammary stem/bipotent progenitor cell proliferation. Targeted deletion of Lfng in mammary epithelium induces basal tumors with reduced expression of Notch targets, amplification of the Met/Caveolin gene locus, and elevated Met and Igf-1R signaling. Human basal breast cancer, a disease associated with elevated MET receptor signaling and Caveolin protein, express low levels of LFNG. Thus, reduced LFNG expression cooperates with a Met/ Caveolin amplicon to promote basal breast disease. SIGNIFICANCE: Anti-Notch therapy is currently being tested for efficacy against basal-like breast cancer in humans. Here we report that LFNG, which controls Notch receptor activation, is consistently expressed at a low level in basal tumors and that deletion of this gene in the mouse mammary gland reduces Notch signaling, increases proliferation and induces basal mammary tumors in cooperation with amplification of the Met/Caveolin gene locus. These mutations interact to promote basal gene expression by decreasing Notch pathway activation, as well as to enhance Met and Igf-1R signaling. These pathways can be targeted at multiple levels in humans harboring basal breast cancer with amplification of MET and CAV1/2