Breast cancer represents the second most commonly diagnosed cancer type amongst women in the United States and Europe. Much is known about the genes that are affected by cancer-causing mutations in breast cancer;however, less is known about molecular events that are crucial for metastasis, which is the major cause of cancer mortality. The triple negative (TN) (i.e. lacking expression [or overexpression] of ER and HER2, as well as progesterone receptor [PR]) breast cancer subtype is highly metastatic. Wnt10b/b- catenin/HMGA2 signaling has been shown by our group to over-activated in triple-negative breast cancers (TNBC) and basal-like cancers. We uncovered in a translational model that Wnt10b/?-catenin signaling triggers high HMGA2 activity and cell cycle proliferation in tumor-initiating cells leading to triple-negative mammary tumors in human and mice. Importantly our group has shown that both WNT10B and HMGA2 have significant correlation with predicting survival outcome and HMGA2 alone could predict metastasis for TNBC. TNBC has a propensity to metastasize, mainly to the brain (30%) and lung (40%). In contrast, other breast cancer subtypes metastasize to liver (30%) and bone (40%). Unlike other subtypes of breast cancer (ER? and HER2 positive tumors) there is no targeted therapy for TNBC. A therapeutic regimen for TNBC remains a major challenge in the clinics because the underlying molecular mechanisms are still not well understood-in particular how it preferentially metastasizes to the lung. MMTV-Wnt10b-IRES-LacZ transgenic mouse mammary gland tumors give rise to rare spontaneous primary lung metastasis (<0.30%). However, Wnt10bLacZ-driven tumor-initiating cells robustly induce pulmonary metastasis (>60%) in syngeneic mice. Isolated Wnt10bLacZ lung metastasis tumors cells with mesenchymal stem-cell properties express epithelial-to- mesenchymal transition (EMT) markers featuring high expression of HMGA2 and factors critical for metastatic colonization. Utilizing both a specific Wnt/?-catenin inhibitor ICG-001 and silencing of HMGA2 blocks proliferation and N-CADHERIN expression with concurrent restoration of E-CADHERIN and WNT7A levels. Preliminary data illustrate that silencing of HMGA2 can block lung metastasis in vivo and can regulate the status of H3K4me3 on a subset of genes that are targeted by b-catenin/CBP HAT-Activity. We will study the underlining mechanism(s) by which HMGA2-mediated epigenetic activity regulates EMT and lung metastasis.
Our first aim i s to study the in vivo role of HMGA2 in lung metastasis using both metastatic mouse Wnt10bLacZTG cells and human triple negative breast cancer cell lines that have been silenced for HMGA2.
Our second aim i s to determine the functional role of HMGA2 in lung metastasis by assessing changes in ?-catenin-CBP/HAT-mediated histone modifications on promoters of EMT-signature, differentiation, proliferation and tumor suppressor genes by ChIP analysis using antibodies to HMGA2, H3K4me3, H3K27me3, and H3K9Ac. Our findings may alter therapeutics for the metastatic TNBC tumors.
Breast cancer has been classified into six-ten subtypes: luminal A, luminal B, ErbB2/Her2, normal breast-like, basal-like and triple negative. The goal of this application is to further develop functional and mechanistic understanding of how the Wnt-pathway alters the triple negative breast cancer (TNBC) subtype, which afflicts African American women at ~3 times the rate as other ethnic groups. TNBC is highly invasive and does not respond to targeted therapeutics;therefore it is necessary to develop new treatments to combat TNBC.