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Distinct luminal type mammary carcinomas arise from orthotopic Trp53 null mammary transplantation of juvenile versus adult mice

ABSTRACT: Age and physiological status like menopause are key factors in mammary development and are associated with breast cancer risk. Less clear is what factors influence breast cancer intrinsic subtypes that are associated with prognosis. Here, we investigated the age of the host in a mammary chimera model. The mammary glands of wildtype BALB/c mice were cleared of endogenous epithelium at 3 weeks of age and subsequently transplanted during puberty (5 weeks) or upon maturation (10 weeks) with syngeneic Trp53null mammary fragments. The Trp53null mammary epithelium undergoes a high rate of neoplastic transformation, such that carcinomas arise over the course of a year. Tumors arose more rapidly (p=0.003, log-rank test) when transplanted to adult hosts (AH, n=89) compared to tumors arising following transplantation into juvenile hosts (JH, n=55). However, JH tumors grew several times faster than AH tumors, were more perfused as indicated by 2-fold larger blood vessels (p=0.015), and exhibited a 2-fold higher mitotic index (p=0.009). Transplantation into juvenile hosts (JH) gave rise to 80% ER positive tumors compared to 60% in adult hosts. However, tumor cells were significantly more ER immunoreactive (p=0.0001) in JH tumors compared to those in AH tumors and were more highly positive for insulin like growth factor receptor phosphorylation (p=0.026). Expression profiles of JH (n=15) and AH (n=12) tumors identified 243 differentially expressed genes. The main biological processes enriched in JH tumors were organ morphology, proliferation, and lipid metabolism. An expression profile of juvenile versus adult (JVA) tumors revealed a luminal transcriptional program, characterized by expression of Foxa1, Igf2, Ccnd1 and Fgfr2. The human homologs of JVA genes (JVAh) were used to create two centroids (AHh or JHh) to classify human breast cancers from archival microarray datasets in two-dimensional space. Luminal human breast cancers were more like JH tumors compared to basal-like cancers, whereas luminal A tumors were more like JH tumors than luminal B tumors. Consistent with this, JVAh genes segregated human luminal A from luminal B breast cancers via hierarchical clustering. The distinct biology of tumors arising from tissue undergoing morphogenesis in the context of puberty suggests that young age at neoplastic transformation promotes a luminal tumor phenotype and supports the contention that the tumor intrinsic subtype is influenced by physiological status at the time of putative initiation.

ORGANISM(S): Mus musculus

PROVIDER: GSE56726 | GEO | 2014/12/01

SECONDARY ACCESSION(S): PRJNA244373

REPOSITORIES: GEO

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Project description:Densely ionizing radiation is a major component of the space radiation environment and has potentially greater carcinogenic effect compared to sparsely ionizing radiation that is prevalent in the terrestrial environment. It is unknown to what extent the irradiated microenvironment contributes to the differential carcinogenic potential of densely ionizing radiation. To address this gap, 10-week old BALB/c mice were irradiated with 100 cGy sparsely ionizing g-radiation or 10, 30, or 80 cGy of densely ionizing, 350 MeV/amu Si particles and transplanted 3 days later with syngeneic Trp53 null mammary fragments. Tumor appearance was monitored for 600 days. Tumors arising in Si-particle irradiated mice had a shorter median time to appearance, grew faster and were more likely to metastasize. Most tumors arising in sham-irradiated mice were ER-positive, pseudo-glandular and contained both basal keratin 14 and luminal keratin 8/18 cells (designated K14/18), while most tumors arising in irradiated hosts were K8/18 positive (designated K18) and ER negative. Comparison of K18 vs K14/18 tumor expression profiles showed that genes increased in K18 tumors were associated with ERBB2 and KRAS while decreased genes overlapped with those down regulated in metastasis and by loss of E-cadherin. Consistent with this, K18 tumors grew faster than K14/18 tumors and more mice with K18 tumors developed lung metastases compared to mice with K14/18 tumors. However, K18 tumors arising in Si-particle irradiated mice grew even faster and were more metastatic compared to control mice. A K18 Si-irradiated host profile was enriched in genes involved in mammary stem cells, stroma, and Notch signaling. Thus systemic responses to densely ionizing radiation enriches for a ER-negative, K18-positive tumor, whose biology is more aggressive compared to similar tumors arising in non-irradiated hosts. Key Words: ionizing radiation; breast cancer; heavy ion radiation;initiation; promotion 3 different dose of Si were used. Total RNA was extracted from mammary tumors derived from transplantations of non-irradiated p53null mammary fragments into irradiated hosts. We analyzed a total of 45 Trp53-null tumors: 18 from sham-irradiated hosts, 9 from 10 cGy Si-irradiated hosts, 10 from 30 cGy Si-irradiated hosts, and 8 from irradiated hosts.

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Distinct luminal type mammary carcinomas arise from orthotopic Trp53 null mammary transplantation of juvenile versus adult mice

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