Quantification of fluorophore distribution and therapeutic response in matched in vivo and ex vivo pancreatic cancer model systems

Abstract

Therapeutic resistance plagues cancer outcomes, challenging treatment particularly in aggressive disease. A unique method to decipher drug interactions with their targets and inform therapy is to employ fluorescence-based screening tools; however, to implement productive screening assays, adequate model systems must be developed. Patientderived pancreatic cancer models (e.g., cell culture, patient-derived xenograft mouse models, and organoids) have been traditionally utilized to predict personalized therapeutic response. However, cost, long read out times and the inability to fully recapitulate the tumor microenvironment have rendered most models incompatible with clinical decision making for pancreatic ductal adenocarcinoma (PDAC) patients. Tumor explant cultures, where patient tissue can be kept viable for up to weeks, have garnered interest as a platform for delivering personalized therapeutic prediction on a clinically relevant timeline. To fully explore this ex vivo platform, a series of studies were completed to quantitatively compare in vivo models with tumor explants, examining gemcitabine therapeutic efficacy, small molecule uptake and drug-target engagement using a novel fluorescently-labeled gemcitabine conjugate. This initial work shows promise for patient-specific therapeutic selection, where tumor explant drug distribution and response recapitulated the in vivo behavior and could provide a valuable platform for understanding mechanisms of therapeutic response and resistance.

A Scaffold-Free 3-D Co-Culture Mimics the Major Features of the Reverse Warburg Effect In Vitro

“…For example, there is a considerable lot-to-lot variability, Matrigel is derived from tumor tissue, and it inherently adds specific physicochemical matrix properties [ 48 ]. Furthermore, it has a significant autofluorescence in the green wavelength range [ 49 , 50 ], rendering its use in marker-specific microscopic analyses less efficient. We compared 3-D cultures made with and without BME and experienced issues of autofluorescence.…”

In vivo Mouse Models of Pancreatic Ductal Adenocarcinoma

“…Such an approach generated a dose response in fluorescence intensity that was significantly higher than PDX mice administered the fluorophore alone (no GEM), though highest levels of drug uptake correlated with areas of necrosis as revealed by tissue morphology. And this methodology can also be applied to other drugs for similar evaluations (106). [ 18 F]-FAC metabolic PET imaging was as effective in measuring GEM uptake as [ 14 C]-GEM in 3 individual PDAC PDX mouse models, demonstrating [ 18 F]-FAC metabolic PET as a solid surrogate of GEM uptake (98).…”