Benjamin Jacob Mayro - US grants

ABSTRACT Lung cancer has the highest prevalence of brain metastasis among all other cancer types, occurring in approximately 40% of patients. The presence of lung cancer brain metastases (LCBM) is associated with cognitive decline and a median survival of 4-6 months. Currently utilized therapies for treating LCBMs include whole brain radiation therapy (WBRT), chemotherapies, and targeted therapies aimed at kinases with ?driver? mutations. The use of WBRT increases patient cognitive decline, while targeted therapies have been proven ineffective due to variable responses and the development of drug resistance. Thus, there is an obvious unmet clinical need to better understand the molecular mechanisms that promote LCBM and subsequently use these discoveries to develop new therapeutic strategies. Our laboratory discovered using an in vivo model of brain metastasis that Abelson tyrosine protein kinase 2 (ABL2) promotes LCBM by propagating a feed-forward loop consisting of ABL2, AXL receptor tyrosine kinase, and the TAZ transcriptional co-activator. Recently, my preliminary data revealed an ABL-dependent stabilization and transcriptional activation of hypoxia inducible factor-1? (HIF-1?) and heatshock factor 1 (HSF1) in this model. Activation of the HIF-1? and HSF1 transcription networks in cancer is associated with tumor proliferation, metastasis, and therapy resistance. Therefore, my central hypothesis is that the ABL kinases regulate multiple transcriptional networks that promote lung cancer brain metastasis and therapy resistance. I will examine this hypothesis through the following two aims: 1) Define the ABL-regulated HIF-1? transcription network required for lung cancer brain metastasis, and 2) Identify ABL- dependent HSF1- regulated pathways necessary for lung cancer colonization of the brain. These aims will evaluate whether increased expression of HIF-1?, HSF1, and TAZ can be used as biomarkers for lung cancer patients with brain metastasis and whether blood brain barrier permeable ABL kinase inhibitors might be an effective novel therapy for treating brain metastatic lung cancer.

PROJECT SUMMARY/ ABSTRACT The perturbation of phospho-tyrosine mediated signaling networks is an essential occurrence during the multistep process of tumor development and progression. As a result, the components of these phospho-tyrosine signaling networks, especially tyrosine kinases, have been shown to be a key reservoir of actionable molecular targets for the treatment of cancer. In recent years, it has been revealed that the tumor microenvironment plays a critical role in modulating the signaling pathways that govern tumor progression and metastasis. The features of a tumor's microenvironment have been shown to produce unique sensitivities and resistances to different treatment modalities. One major aspect of the tumor microenvironment which is often overlooked in preclinical studies is oxygen tension. This proposal seeks to understand the impact that oxygen tension has on phosphotyrosine-dependent signaling networks in solid tumors, and how the resultant vulnerabilities can be targeted to improve patient outcome. In Aim 1.1 (prior studies), we sought to identify alterations in signaling networks that occur when lung cancer cells colonize the brain, a hypoxic environment. We showed that brain- metastatic lung cancer cells elevate and have an increased dependence on a non-canonical HSF1-E2F transcriptional program for survival. Importantly, we identified that this transcriptional program is targetable through treatment with allosteric ABL2 tyrosine kinase inhibitors. In Aim 1.2 (proposed studies), using a small molecule screen, I have identified previously unrecognized modulators of the cellular response to hypoxia, a tumor microenvironment feature associated with increased metastasis and lower overall survival in patients with solid tumors. The top uncharacterized hit was the FDA-approved ABL1/2 tyrosine kinase inhibitor Dasatinib and my preliminary investigation has shown that the ABL kinases are critical regulators of HIF-1? protein stability. I will continue mechanistic investigation of the ABL- HIF-1? axis in vitro and in vivo. Finally, in Aim 2 (post-doctoral studies), I will focus on understanding the impact that tumor representative- oxygen tension has on protein tyrosine phosphatase activity. Extensive investigation has demonstrated that tumor hypoxia induces activation of phospho-tyrosine signaling networks, but current work has almost exclusively focused on the role of tyrosine kinases. I show that hypoxia induces inhibitory oxidation of protein tyrosine phosphatases (PTPs). Using mass- spectrometry based approaches, I will identify the oxidized- PTP landscape (ox-PTPome) of tumor samples and cancer cells at oxygen levels observed in tumors. Further, since PTPs restrain cellular signaling, I will employ high-throughput drug screening technologies in vitro to identify emergent sensitivities due to the loss of PTP activity that would not have been captured in the numerous normoxically (tumor-unrepresentative oxygen level) performed screens. Overall, the focus of my career is to understand how the different characteristics of the tumor microenvironment, such as hypoxia, modulates the signaling networks co-opted by cancer cells and translate this to the identification of biological mechanisms that may be amenable to therapeutic exploitation.