Comparative oncogenomics identifies breast tumors enriched in functional tumor-initiating cells

Abstract

The claudin-low subtype is a recently identified rare molecular subtype of human breast cancer that expresses low levels of tight and adherens junction genes and shows high expression of epithelial-to-mesenchymal transition (EMT) genes. These tumors are enriched in gene expression signatures derived from human tumorinitiating cells (TICs) and human mammary stem cells. Through crossspecies analysis, we discovered mouse mammary tumors that have similar gene expression characteristics as human claudin-low tumors and were also enriched for the human TIC signature. Such claudinlow tumors were similarly rare but came from a number of distinct mouse models, including the p53 null transplant model. Here we present a molecular characterization of 50 p53 null mammary tumors compared with other mouse models and human breast tumor subtypes. Similar to human tumors, the murine p53 null tumors fell into multiple molecular subtypes, including two basallike, a luminal, a claudin-low, and a subtype unique to this model. The claudin-low tumors also showed high gene expression of EMT inducers, low expression of the miR-200 family, and low to absent expression of both claudin 3 and E-cadherin. These murine subtypes also contained distinct genomic DNA copy number changes, some of which are similarly altered in their cognate human subtype counterpart. Finally, limiting dilution transplantation revealed that p53 null claudin-low tumors are highly enriched for TICs compared with the more common adenocarcinomas arising in the same model, thus providing a unique preclinical mouse model to investigate the therapeutic response of TICs. genetically engineered mouse model | gene profiling | array comparative genomic hybridization B reast cancer (BC) is the second leading cause of cancerrelated deaths among women in the United States (1). The large compendium of underlying genetic alterations and the resulting histological and molecular subtypes illustrate the heterogeneous nature of this disease. Both this intertumor heterogeneity and the cellular heterogeneity found within a breast tumor (intratumor heterogeneity) are major obstacles to effective treatments. One common feature of BC (and most cancers) is the loss of the tumor suppressor p53 function. p53 has been shown to be mutated in ≈40% of BCs, associated with poor clinical outcomes, and a higher frequency of mutations occurs in more-aggressive molecular subtypes, including the basal-like subtype of human BC (2).Mice homozygous for p53 loss have been shown to develop lymphomas and sarcomas with a short latency (3, 4). When crossed into the BALB/c background, mammary tumors were observed in p53 +/− mice (5). To circumvent the appearance of other tumor types that occurred with short latency, the model was further modified (6); namely, 6-wk-old p53 −/− glands were removed and transplanted into 3-wk-old wild-type BALB/c recipients. These mice develop mammary tumors stochastically with an average latency of approximately 12 mo. Interestingly, the p53 null epithelium initially forms normal du...

Dimethyl Fumarate Inhibits the Nuclear Factor κB Pathway in Breast Cancer Cells by Covalent Modification of p65 Protein

“…2, A, solid line, and B). IC 50 values for MS inhibition across the different cell lines is ϳ20 M, the same IC 50 value observed for inhibition of the cytokine-induced NFB pathway in adherent monolayer cultures.…”

“…All of these end points were attenuated by DMF or IKK7 to the same extent (Fig. 3, A and B), 50 values were calculated with GraphPad software using normalized data. G, DMF has no effect on estrogen receptor target gene TFF1 and IGFBP4 mRNA, measured in MCF-7 cells pretreated with DMF (20 M) for 2 h, followed by estrogen treatment (E2, 10 nM) for another 2 h. The different letters above bars indicate significant difference between treatments, p Ͻ 0.001. suggesting that DMF can abrogate MS formation by inhibiting the NFB pathway.…”

Reprogramming during epithelial to mesenchymal transition under the control of TGFβ

“…74,75 In agreement with this, molecular analysis of p53-null breast cancers classified them as having the claudin-low tumor gene signature, that is, cancers with dominant EMT and cancer stem cell characteristics. 76 In addition, TGFb directly regulates the majority of the EMT-TFs. 41 We found that TGFb, via Smad signaling, upregulates HMGA2 to drive EMT, 19 and this has been complemented independently in vivo as HMGA2 overexpression causes metastasis, 77 further reinstating the link between EMT and metastasis.…”

Comparative Oncogenomics Implicates the Neurofibromin 1 Gene (NF1) as a Breast Cancer Driver

“…RNA was hybridized to custom murine Agilent microarrays and normalized as described (Herschkowitz et al 2007(Herschkowitz et al , 2012. Data were deposited into the Gene Expression Omnibus (accession no.…”