Clinical/pathological observations of breast tumor heterogeneity have now been confirmed at the gene expression level with the characterization of distinct tumor subtypes. ER-negative cancer comprises at least two distinct subtypes: the Her2+ subtype and the basal-like subtype. The basal-like breast cancer phenotype is more prevalent among premenopausal African-American cancer cases. Our gene expression analysis reveals that many basal-like breast cancers express genes that are known to be regulated by the transcription factor NF-?B. Recently it has been reported that basal-like cancers exhibit activation of PI3K/Akt and loss of p53. The Her2+ subtype of cancer is associated with the expression of a distinct set of NF-?B-dependent genes from that found in basal-like. While Akt is critical for growth and survival of Her2+ cells, our work indicates that Akt is not involved in the activation of NF-?B in Her2+ cells while it is important in basal-like cells. --Our hypothesis is that NF-?B contributes to the oncogenic phenotype and cancer therapy resistance in both basal-like and Her2+ breast cancers through different mechanisms, and that NF-?B activation in these cancers occurs by different pathways. We hypothesize that different forms of NF-?B are activated in these two types of breast cancers leading to different target gene expression. Additionally, we explore the control of Akt in these cells through an IKK1-mTORC2 mechanism. Furthermore, our data demonstrate that mouse breast tumors reflect many of the phenotypes of human tumors. Thus, we propose that these animal models can be used to test genetically the involvement of the IKK/NF-?B pathway in tumor initiation and progression, and used for analysis of therapies that block NF-?B activation or other key regulatory signaling. We are unaware of any study utilizing an animal model of basal-like cancer to address a role for IKK/NF-?B in the disease. There is one very limited knock-in study analyzing an involvement of IKK1 in Her2+ cancer. Drug studies are limited to xenografts and are quite limited regarding specific inhibitors, and do not focus on dual roles of IKK1 and IKK2. --To test our hypotheses, we propose to: (i) analyze basal-like cancer cells, animal models, and human tissue for mechanisms associated with the activation of NF-?B and target gene expression, and determine the effects of inhibitors that target these and other relevant pathways, (ii) characterize Her2+ cancer cell lines, animal tumors, and human tissue for activation of NF-:B, target gene expression, and onco-phenotypes, along with parallel inhibitor studies, with an additional approach to address Herceptin resistance, and (iii) test animal models for basal-like and Her2+ cancers for the roles of NF-?B/IKK components and specific gene targets for the development and progression of the cancers. Determine if highly specific inhibitors of IKK, mTOR, and possibly EGFR can suppress or revert growth of animal-derived tumors and/or sensitize to chemotherapy. These studies will provide insight into the development and oncogenic phenotypes of two key breast tumor subtypes and have the potential for the development of new therapeutic options for these diseases.
While activation of the transcription factor NF-?B is associated with hematologic malignancies and with solid tumors, there are only a few studies using specific inhibitors of the NF-?B pathway in animal models of cancer. NF-?B is activated by both IKK1 and IKK2, and no efforts have been directed at blocking total IKK in tumor cells. Additionally, there are no inhibitor studies directed at targeting the ability of IKK to control other key pro-oncogenic pathways (separate from NF-?B). Our effort is directed towards understanding the role of NF-?B in two breast tumor subtypes with poor prognosis: basal-like cancers and Her2/ErbB2+ cancers. Preliminary data indicate that different forms of NF-?B are activated in these cancers leading to the regulation of distinct sets of genes. Interestingly, genes expressed in human basal-like or Her2+ cancers are also expressed in human cancer cell lines and in animal models for these breast cancer subtypes. We will explore the regulatory pathways associated with NF-?B activation and function in these two types of cancer, with additional studies focused on the ability of IKK to control Akt in these cells. Based on encouraging preliminary data, we will utilize genetic models and we will test highly specific inhibitors of IKK1 and IKK2 (key upstream regulators of NF-?B) in cell lines and in animal models to test the involvement of this pathway in controlling oncogenic development/progression and in regulating resistance to key cancer therapeutics. In this regard, we are hopeful that our experiments will provide new therapeutic options for forms of breast cancer with poor outcome. Additionally, our studies will provide unique insight into the functions of different signaling pathways associated with NF-?B in controlling oncogenic phenotypes.
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