Overcoming Resistance in HER2-positive Breast Cancer

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 DESCRIPTION (provided by applicant): Overcoming resistance is a central challenge to finding a cure for breast cancer. A number of mechanisms have been suggested for how breast cancer cells escape treatment and survive, indicating potential novel avenues for therapeutic intervention. These mechanisms include the ability of breast cancer cells to turn on pathways to evade apoptotic cell death and to use the catabolic process, autophagy, as a survival mechanism. We have characterized a novel AMPK-related protein kinase, Hunk, to be critical for breast cancer growth and progression by virtue of its ability to mediate tumor cell survival, and provide evidence that Hunk regulates apoptosis and autophagy. Hunk is upregulated by HER2/neu to promote tumorigenesis, and suppresses apoptosis while promoting autophagy in response to stress such as HER2 inhibitor treatment, indicating that targeting Hunk will combat resistance to HER2 inhibition by blocking these escape pathways. The long-term goal of this research is to identify methods to improve breast cancer treatment by overcoming or evading resistance. The overall objective of this proposal is to demonstrate the molecular mechanisms by which Hunk kinase regulates apoptosis and autophagy to delineate Hunk's role in mediating resistance to breast cancer treatment. The rationale for the proposed research is that, once it is understood the mechanism by which Hunk regulates cell survival and how this impacts breast cancer treatment, the activity of this kinase could be manipulated pharmacologically, resulting in a new and innovative approach for the prevention and treatment of resistance in breast cancers. To pursue this rationale, we hypothesize that Hunk facilitates resistance to HER2 inhibition by regulating two cell death pathways: apoptosis and autophagy. Therefore, inhibiting Hunk will overcome resistance by blocking these escape mechanisms. To test this hypothesis, the following specific aims are proposed. Aim 1: Determine the mechanisms by which Hunk regulates cell survival to mediate resistance to HER2 inhibitors by assessing (A) whether Hunk signals through intrinsic or extrinsic apoptotic pathways and canonical or non-canonical routes of autophagy as well as whether Hunk regulates crosstalk between these pathways. (B) Determine if Hunk facilitates resistance in an Akt-dependent manner. Aim 2: To demonstrate that (A) targeting Hunk impairs tumorigenesis in trastuzumab and lapatinib resistant BrCa and (B) evaluate JNK signaling in promoting resistance because we find that targeting JNK is effective in killing resistant breast cancer cells and collaborates with Hunk targeting. The contribution of the proposed research is expected to be the elucidation of novel molecular activities of Hunk that regulate cell survival mechanisms, apoptosis and autophagy, which cause breast cancers to become resistant to treatment. These contributions are significant and conceptually innovative because they provide novel avenues for pharmacologic intervention in preventing and/or overcoming resistance to breast cancer treatment.