B-373 The Development of a Logic-Gate Probe to Investigate Hypoxia in Cancer Stem Cells

Abstract

Abstract Background Cancer stem cells (CSCs) represent only a small fraction of the tumor population, yet they present a profound challenge to cancer treatment. CSCs contribute to tumor complexity via their unique ability to self-renew, develop into multiple lineages, and maintain an unchecked proliferation potential. To identify CSCs, the cytoprotective enzyme aldehyde dehydrogenase 1A1 (ALDH1A1) is a well-annotated biomarker of cancer stemness which is associated with a poor prognosis in patients with gastric and lung cancers when overexpressed. Within CSCs, ALDH1A1 functions to regulate oxidative stress by transforming biological aldehydes into their corresponding non-toxic carboxylic acid counterparts and further is linked to the retinaldehyde signaling pathway. Beyond this enzyme, oxygen availability within the tumor microenvironment (TME) can also influence stemness properties. Specifically, hypoxia, is required to maintain the CSC phenotype by prolonging the undifferentiated state. Methods To study the mechanistic underpinnings of complex relationship in vivo new technologies are needed as current approaches are insufficient. Indeed, probes have been developed to study ALDH1A1 and hypoxia in parallel, however, imaging approaches lack the requisite resolution to ensure they are reporting on the same CSC population. To this end, we have designed a powerful logic-gate probe that links the reporters of ALDH1A1 activity and oxygenation in a unique manner such that different readouts will result (color of light) depending on the TME environment. Results Our lab has previously developed a near-infrared hypoxia-sensing fluorescent probe that is fundamental to our current logic-gate design. This component has been validated in 4T1 murine breast cancer cells, to yield a 1.6-fold increase in ratiometric fluorescence response when incubated under hypoxic conditions as compared to its normoxic controls. Additionally, the ALDH1A1 sensing component has been validated via purified enzyme to yield an increase in bioluminescent signal enabling its use for future in vivo studies. Conclusion This technology has important clinical implications to understand the mechanistic underpinnings between oxygenation and cancer stemness. Further research is being conducted to further test the hypothesis that metformin (anticancer drug) kills cancer by altering oxygen metabolism which in turn depletes the CSC population. Furthermore, this probe has far-reaching implications in monitoring novel therapeutic cancer treatment.