PROTAC Targeting of Tip60 in Syngeneic Cancer Models Using Cereblon Knock-in Mice

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Project Summary We will investigate whether therapeutic targeting of Tip60, a histone/protein acetyltransferase essential for the functions and survival of Foxp3+ T-regulatory (Treg) can significantly decrease Treg functions in vivo while preserving conventional T cell responses, leading to inhibition of lung tumor growth in murine models. We will also assess the effects of Tip60 targeting on the DNA damage response within tumors induced by conventional therapies for lung cancer, including irradiation and cisplatin therapy. We have developed Tip60 PROTAC (proteolysis targeting chimeric) molecules that recruit the Cereblon E3 ligase so as to promote Tip60 degradation, and we employ Cereblon knock-in (CrbnI391V) immunocompetent C57BL/6 mice in compound screening and tumor models to facilitate identification of compounds for subsequent clinical development. Aim 1 - Can Tip60i limit growth of tumors in immunocompetent hosts by decreasing Foxp3+ Treg suppressive function? We have developed several Tip60i, including Crbn- and VHL-based PROTAC compounds. We will test if Tip60i PROTAC compounds can modulate Treg function and control growth of experimental lung cancers by (1.1) optimizing Tip60i PROTAC compounds, and testing them (1.2) alone, or in conjunction with (1.3) vaccination or (1.4) checkpoint inhibitor therapy in CrbnI391V mice. We will also assess effects of Tip60i on 1.5) normal human Treg and/or Teff cells, and 1.6) human lung cancer associated Treg cells. Aim 2 – Determine if Tip60i disrupts DDR actions essential for tumor cell survival. Our molecular investigations will explore Tip60-dependent mechanisms that promote cellular resistance to genome instability and normal programmed mechanisms of death, and which underpin cancer initiation and chemotherapeutic resistance crucial for lung cancer cell survival. We will test if Tip60i compounds have direct anti-tumor effects by disrupting 2.1) Tip60-dependent p53 activation and/or 2.2) DNA repair mechanisms. Our studies will facilitate the development of new strategies for immunotherapy in patients with malignancies, given that the new Tip60-directed therapies have dual mechanisms of action, involving targeting Foxp3+ Treg cells and intrinsic tumor cell responses to therapy. The data to be generated will likely lead to clinical trials in patients with lung cancers, and should also have relevance to additional individuals, given the increasingly recognized potential for immunotherapy in the management of many other types of cancers.