Project 1

Most luminal B breast cancers (LBBC; ER+, HER2-wt, Ki67>14%) carry a good prognosis. However, approximately 20% of LBBC are highly aggressive and resistant to current therapies. There have been many failed attempts to therapeutically target MYC. These attempts have failed, in part, due to our current inability to separate the cancer-promoting activities of MYC, mechanistically or therapeutically, from its normal essential cellular functions. In preliminary data, we show that the cancer-transforming ability of MYC is dependent on three lysine (K) residues of MYC (K149, K158, and K323) that are major substrates for acetylation by the histone acetyltransferases (HATs) p300 and GCN5. Guided by our preliminary data, here we aim to dissect the cofactors and molecular mechanisms by which these MYC acetyl-K (AcK) residues promote cell transformation and initiation and progression of LBBC. Our long-term goal is to identify new “druggable” targets to improve survival of patients most affected by aggressive LBBC. Guided by our preliminary data, we hypothesize that a gene-selective MYC-AcK signaling pathway drives the aggressive tumor cell biology of therapy-resistant LBBC and involves transcription cofactors and epigenetic coregulators that “write” and/or “read” AcK marks on MYC and histones, perhaps including cofactors co-overexpressed with MYC in LBBC, such as PIN1, GCN5, p300, and/or YEATS2. Aim 1 will define the impact of MYC-AcK dependent signaling in mammary epithelial cell transformation and in the aggressive biology of LBBC. Aim 2 will characterize the molecular mechanisms of MYC-AcK dependent gene regulation directly in LBBC from patients.