van den Berg, N. S. | bioRxiv Science

bioRxiv2023

Flavinated SDHA Underlies the Change in Intrinsic Optical Properties of Oral Cancers

The molecular basis of reduced autofluorescence in oral squamous cell carcinoma (OSCC) cells relative to normal cells has been speculated to be due to lower levels of free flavin adenine dinucleotide (FAD). This speculation, along with differences in the intrinsic optical properties of extracellular collagen, lie at the foundation of the design of currently-used clinical optical detection devices. Here, we report that free FAD levels may not account for differences in autofluorescence of OSCC cells, but that the differences relate to FAD as a co-factor for flavination. Autofluorescence from a 70 kDa flavoprotein, succinate dehydrogenase A (SDHA), was found to be responsible for changes in optical properties within the FAD spectral region with lower levels of flavinated SDHA in OSCC cells. Since flavinated SDHA is required for functional complexation with succinate dehydrogenase B (SDHB), decreased SDHB levels were observed in human OSCC tissue relative to normal tissues. Accordingly, the metabolism of OSCC cells was found to be significantly altered relative to normal cells, revealing vulnerabilities for both diagnosis and targeted therapy. Optimizing non-invasive tools based on optical and metabolic signatures of cancers will enable more precise and early diagnosis leading to improved outcomes in patients.

cancer biology↗

bioRxiv2020

Design of optical imaging probes by screening of diverse substrate libraries directly in disease tissue extracts

Fluorescently-quenched probes that are specifically activated in the cancer microenvironment have great potential application for diagnosis, early detection and surgical guidance. These probes are often designed to target specific enzymes associated with disease by direct optimization using single purified targets. However, this can result in painstaking chemistry efforts to produce a probe with suboptimal performance when applied in vivo. We describe here an alternate, unbiased activity-profiling approach in which whole tissue extracts are used to directly identify optimal peptide sequences for probe design. Screening of mouse mammary tumor extracts with a hybrid combinatorial substrate library (HyCoSuL) identified a combination of natural and non-natural amino acid residues that could be used to generate highly efficient tumor-specific fluorescently quenched substrate probes. The most effective probe is significantly brighter than any of our previously reported tumor imaging probes designed for specific proteases and robustly discriminates tumor tissue from adjacent healthy tissue in a mouse model of cancer. Importantly, although the probes were developed by screening mouse mammary tumor tissues, they are able to effectively distinguish human ductal carcinomas from normal breast tissue with similar reactivity profiles to those observed in mouse tissues. This new strategy simplifies and enhances the process of probe optimization by direct screening in a tissue of interest without any a priori knowledge of enzyme targets. It has the potential to be applied to advance the development of probes for diverse disease states for which clinical or animal model tissues are available.

bioengineering↗