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KRAS mutations are the most common activating mutation in lung cancer and are identified in 25-30% of cases of lung adenocarcinoma. The clinical activity of molecularly targeted therapy in KRAS mutant lung cancer has been limited, as most prior approaches focused on downstream targets of the MAPK pathway, an approach which was largely ineffective. KRAS G12C is the most common subtype of activating KRAS mutation in NSCLC. Identification of a binding pocket of KRAS G12C enabled the development of covalent inhibitors (Ostrem et al. Nature, 2013), which selectively bind to the mutant cysteine and spare wild type or other mutant KRAS proteins (hereafter referred to as G12Ci). These drugs bind only to GDP-bound (i.e. inactive) KRAS G12C and trap the oncoprotein in its inactive state by preventing nucleotide exchange (Lito et al. Science, 2016). Of this new class of agents, two drugs (MRTX849 and AMG510) have demonstrated efficacy in early phase clinical trials, representing a remarkable breakthrough in the management of KRAS G12C mutant lung cancer. Acknowledging the limited number of patients treated thus far, response rates of 40-50% have been reported, demonstrating clinical activity far superior to prior molecularly targeted approaches for the management of KRAS mutant lung cancer. Despite this major advance it is clear that resistance to therapy, both primary and acquired, will remain a challenge and may in part be due to upstream receptor tyrosine kinase (RTK) signaling. Understanding the mechanisms of resistance to this new class of therapy is of paramount importance to improve the efficacy and durability of response, and for identifying rational combinatorial therapies for future clinical trials.

Patients with extensive-stage small cell lung cancer (SCLC) have robust responses to first-line platinum and etoposide; however, most patients suffer rapid and chemoresistant relapse. Even with the recent incorporation of immunotherapy into first-line treatment, the majority of SCLC patients will die of therapeutically resistant disease. This leads to great impetus to develop more effective, mechanism-based treatment strategies in both the initial and subsequent-line treatment settings in patients with this devastating disease.

Our laboratory has previously used multiple patient-derived xenografts (PDXs) to define EZH2-mediated SLFN11 gene silencing as a frequent mechanism of acquired chemoresistance in SCLC. Mechanistically, SLFN11 sensitizes cells to chemotherapy-induced replication stress, therefore enhancing the effects of DNA-damaging agents. We found that EZH2 inhibition could re-express SLFN11 and prevent its silencing, which was able to either maintain or re-sensitize SCLC PDXs to chemotherapy, suggesting a potential combinatorial strategy to enhance the effectiveness of current standard chemotherapy. To better understand how epigenetic changes can reverse chemoresistance in a clinical setting involving recurrent SCLC, we aim to conduct a prospective clinical trial with pre-specified tissue and peripheral blood correlative testing. Specifically, on-treatment biopsies and circulating tumor cells (CTCs) will be used to better understand the expected reversal of chemoresistance with the addition of an EZH2 inhibitor. This project will involve testing this broad array of clinical specimens in the well-established translation research program within our lab as well as through pre-existing industry and academic collaborations. Our ultimate goal is to identify more effective therapies for patients with this deadly disease.

The majority of lung cancer patients present with advanced disease that is largely incurable. Efforts to improve the early detection of this disease are critical to decrease lung cancer-related mortality. Low-dose computed tomography (CT) screening in high risk patients has demonstrated reduction in lung cancer related mortality through diagnosis of earlier stage disease at the cost of high false-positive rates and the frequent need for invasive diagnostic testing when indeterminate lung nodules are identified. Detecting tumor specific somatic mutations and/or epigenetic signatures in circulating tumor DNA (ctDNA) represents an attractive non-invasive method for identifying early stage lung cancer. However, to realize this promise for lung cancer screening, where ctDNA from small tumors is miniscule, the development of sensitive, specific, and economical ctDNA based assays is critical. 
The bacterial innate immune system consisting of clustered regularly interspaced short palindromic repeats (CRISPR) and their associated endonucleases (CRISPR-Cas) are specifically adapted to recognize foreign nucleic acids. The recent identification and diagnostic adaptation of certain classes of CRISPR-Cas systems, such as CRISPR-Cas12a and -Cas13a, offer unique platforms on which to develop sensitive, specific, and economical assays for the detection of ctDNA. The goal of the current project is to develop CRISPR-Cas12a and -Cas13a based ctDNA assays that can sensitively detect somatic cancer mutations and aberrant promoter hypermethylation often found in lung cancer patients and to validate these assays in plasma samples of patients with early stage NSCLC and in discriminating between benign and malignant nodules identified by low-dose CT screening studies. 

KRAS mutations activate signaling from downstream effector proteins and are though to be required for tumor formation. Exactly how effector signaling is activated, however, is not fully understood. In addition, whether tumors harboring KRAS mutations depend on this oncogene for growth is unclear.

Dr. Lito and his group will dissect the phenotype of KRAS-mutant lung cancer by using a novel allosteric inhibitor that selectively targets KRAS G12C. They will first utilize biochemical assays in order to determine the mechanism of action of this inhibitor. An emphasis will be placed on evaluating how feedback pathways modulate this process, since this is likely to identify factors that may be used as biomarkers of response to treatment.

They will then determine which effector pathways drive the phenotype of KRAS G12C mutant lung cancer, and whether these exhibit adaptation (or reactivation) over time. If so, they will next explore combination-based interventions in order to establish the most effective antiproliferative strategy.

Finally, they will utilize novel patient-derived xenograft and cell line models, established from patients with lung cancer treated at MSKCC, in order to determine if KRAS G12C mutant lung cancers depend on this oncoprotein for growth. These models will also be used to test the most effective combination strategies determined above, as well as to test the potential benefit of intermittent administration schemes designed to best target tumor adaptation to this novel class of inhibitors.

The grand objective of this project is to establish a mutant KRAS-directed therapy for patients with lung cancer.