PROJECT SUMMARY Advances in synthetic biology will play a fundamental role in shaping the future of cancer diagnostics toward earlier and more specific detection of disease. For example, whole-cell biosensors such as bacteria have been genetically engineered to perform complex functions such as signal amplification to detect clinically relevant biomarkers in human urine and serum. In mammalian cells, sense-and-respond components that employ Boolean logic have been demonstrated for multiplexed control of engineered T cell therapies, thereby increasing the specificity of tumor sensing and reducing systemic toxicity. These advances highlight the promise of synthetic biology when applied to cancer, yet the vast majority of these strategies rely on genetic circuits and make use of non-mammalian protein components. Such circuits are complex and raise safety and immunogenicity concerns for regulatory approval, especially in the context of in vivo early cancer detection where repeated administrations of biosensors are likely needed to monitor for nascent disease. This proposal seeks to develop a new class of diagnostics called AND-gated synthetic biomarkers for early detection of cancer metastasis. Synthetic biomarkers are an emerging class of activatable biological sensors that are designed to be administered systemically, query sites of early disease, and harness tumor-dependent activation mechanisms, such as dysregulated protease activity, to drive production of a reporter. These reporters can then be detected noninvasively from blood, urine, or other bodily fluid samples. Proteases play key biological roles across the major hallmarks of metastasis and are particularly potent molecular amplifiers by catalyzing the irreversible hydrolysis of peptide bonds, allowing a single protease to turnover thousands of substrates. AND-gated synthetic biomarkers will be applied for early detection of colorectal cancer (CRC) liver metastasis. Although the liver is a common site for metastatic spread from primary CRC, regional resection of liver-isolated metastases can lead to potentially curative results. Yet early detection of CRC liver metastases at a size when they are most responsive to therapy (1–2 mm) remains challenging by radiographic imaging such as CT and FDA-approved blood test such as the carcinoembryonic antigen (CEA) test. To design AND-gated synthetic biomarkers for CRC liver metastasis, pairwise combinations of proteases will be selected based on differential RNA expression in CRC liver metastases compared to healthy liver tissue. Multivariate mathematical models will be developed to understand how design parameters enhance specificity and cooperativity compared to experimental results. Syngeneic and xenograft models of CRC liver metastasis will be used for preclinical validation studies to allow benchmarking against CT and CEA. This proposal will lay the groundwork for earlier detection of cancer metastasis by programmable synthetic biomarkers.

PROJECT NARRATIVE Advances in synthetic biology will play a fundamental role in shaping the future of cancer diagnostics toward earlier and more specific detection of disease. This proposal seeks to develop a new class of protease- activatable biosensors that implement Boolean AND logic for early detection of colorectal cancer liver metastasis.