PROJECT SUMMARY/ABSTRACT The major goal of this NCI Clinical and Translational R21 application is to reveal the cancer therapeutic and diagnostic potentials of a novel antibody-like chimeric fusion protein, Avaren-Fc lectibody (AvFc), in mouse tumor models. AvFc consists of the high mannose glycan (HMG)-specific lectin Avaren and the fragment crystallizable (Fc) region of human immunoglobulin (Ig)G1. Recent studies have revealed that HMGs are elevated on the cell surface glycome of various tumors. In normal cells, these glycans are processed into more complex forms in the endomembrane system and therefore rarely found on cell surface. Hence, HMGs may provide a new target for cancer therapy and/or diagnosis. However, there is currently no agent selectively targeting tumor-associated HMGs. Our preliminary data showed that AvFc is capable of binding to a broad spectrum of cancer cell lines, including leukemia, melanoma, and lung, breast, colon and cervical cancers, but not to noncancerous human cells. Additionally, AvFc exhibited strong antibody-dependent cell-mediated cytotoxicity activity against various cancer cells tested. AvFc showed good safety profiles in mice upon repeated systemic administration. Lastly, AvFc is efficiently bioproduced in tobacco plants using a plant virus vector. Given these promising developability profile, we hypothesize that AvFc could be developed as a first-in-class cancer therapeutic and/or diagnostic agent targeting tumor-associated HMGs. To prove this hypothesis we propose two specific aims in this application. In Aim 1, we will investigate AvFc's anti-tumor activity in murine tumor challenge models. We will use well-established syngeneic and human tumor xenograft models to determine the effectiveness of AvFc. In Aim 2, we will employ dynamic positron emission tomography scan and radiolabeled AvFc to determine their in vivo biodistribution and tumor specificity in mice. Additionally, we will attempt to isolate and identify tumor cell-surface glycoproteins targeted by AvFc, using a proteomics approach. Results generated in this project will provide a compelling preclinical data package for the development of AvFc as a novel therapeutic and/or diagnostic agent targeting tumor-associated HMGs. Additionally, our data will provide a new basis and a unique tool to investigate the as-yet-unknown roles and mechanisms of elevated HMGs in tumors.