Ratiometric Fluorescent Chemosensing for Predicting Response to Irinotecan-Based Therapies in Pancreatic Ductal Adenocarcinoma.

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive and devastating disease, with most patients facing fatality due to resistance to chemotherapy. The chemotherapeutic cocktail FOLFIRINOX serves as a first line of therapy, and its success can be predicted by the activity of carboxylesterase 2 (CES2), an enzyme responsible for metabolically activating irinotecan (CPT-11), a component of FOLFIRINOX, where low CES2 activity forecasts resistance. Such predictive power enables clinicians to decide whether FOLFIRNOX is worth pursuing prior to administration. Despite this, current methods to measure CES2 activity are insufficient, and a feasible and translatable method for clinical use remains to be developed. To this end, we use Benz-AP, a CES2 ratiometric fluorescent sensor, to detect CES2 activity toward predicting FOLFIRINOX sensitivity. Leveraging this sensor, we demonstrate strong correlations between Benz-AP readouts of CES2 activity and CES2 expression (R2 = 0.9812, P = 0.0047), CPT-11 response (R2 = 0.9181, P = 0.0417), and FOLFIRINOX sensitivity (R2 = 0.9813, P = 0.0417) in PDAC cell lines. These correlations were not observed with TOPO-1 expression levels, SN-38, or FOLFOX treatment. Likewise, strong and significant correlations between Benz-AP measurements and sensitivity of CES2-activated drugs (R2 = 0.7633, P = 0.0156) were also observed in a panel of primary patient PDAC cell lines. Furthermore, we demonstrate the compatibility of Benz-AP for use in ex vivo biopsy sampling by fine needle aspirates, where we detected a significant difference (P < 0.05) in CES2 activity across samples. Collectively, these results demonstrate the applicability of Benz-AP for predicting FOLFIRINOX prognosis across patient samples ranging in biological complexity and advocate for the translation of such technologies in the clinic to guide clinician choice of chemotherapeutic treatment.