Diagnosis of esophageal adenocarcinoma (EAC) at an early stage allows for endoscopic treatment. However, currently 2 out of 3 patients are diagnosed at advanced stages, when treatment includes chemotherapy, radiation and esophagectomy, and prognosis and survival are strongly decreased. Barrett's esophagus (BE), a complication of gastrointestinal reflux disease, is a predisposing condition for EAC and requires patients to undergo regular screening endoscopy and biopsy surveillance. Complementing this approach with fluorescence-guided endoscopy could enhance early detection of cancer lesions by introducing optical contrast, particularly if combined with visualization of a specific molecular target. The DNA repair enzyme Poly(ADP-ribose)Polymerase 1 (PARP1) is highly expressed in tumors and could represent such a target. Here, we have developed the cell permeable, fluorescently labeled small molecule ?PARPi-FL? that binds to nuclear PARP1 with high affinity and specificity. In the proposed preclinical study, I will test the hypothesis that fluorescence-guided imaging of locally applied PARPi-FL is superior to standard-of-care white-light imaging in the detection of early EAC lesions. During the K99 mentored phase, I will characterize PARP1 expression in the progression from BE to EAC in human biospecimens (SA1.1) and identify matching patterns in xenograft tissue and a surgical rat model using an immunohistochemistry approach developed in our laboratory (SA1.2). I will then optimize the topical application of PARPi-FL using a novel applicator device in xenograft models, compare it to systemic application and validate the method using freshly excised human EAC tissue (SA2.1). As an independent investigator (R00), I will apply the method to in vivo imaging of different disease stages of a surgical rat model that closely recapitulates the BE to EAC progression in human disease (SA2.2). In SA3, the accuracy of PARPi-FL imaging as a screening tool for EAC will be quantified by comparing the sensitivity and specificity of fluorescence imaging after topical and systemic application, as well as white-light imaging using methodology adherent to clinical standards. We will also deduct principles on the detection threshold of the probe-device combination to define limits of lesion size and depths than can be detected. Hence, we will develop a targeted imaging approach for EAC lesions under a microdosing protocol using a probe-device combination with an FDA approved imaging platform. This will enable us to predict the success of clinical imaging in EAC and increase the likelihood for achieving our long-term goal of clinical translation. To accomplish this career award, I have carefully assembled a highly complementary advisory team, including my Primary Mentor Dr. Reiner and Co-Mentors Dr. Bradbury and Dr. Patel, my collaborators Dr. Gnen and Dr. Strome, and my advisors Dr. Lewis and Dr. Weber. This dedicated advisory team combines expertise in all areas of the proposal and will provide me with the training and support needed to successfully carry out the described research, complete my career training, and launch my independent research program.
This proposal is dedicated to the development of a targeted fluorescence-guided imaging approach for early detection of esophageal cancer, which could integrate into currently practiced white light surveillance endoscopy in Barrett's esophagus patients. Improved early detection is imperative to increase prognosis and the 5-Year survival rate that remains under 20%, however validated molecular imaging techniques are currently unavailable for this patient population. We aim to show that our innovative imaging approach consisting of topical application of a contrast agent targeted against the nuclear DNA repair enzyme, PARP1, has sensitivity and specificity that is superior to the current standard-of-care detection methods.
