Pancreatic cancer is a devastating disease often detected at later stages, necessitating swift and effective chemotherapy treatment. However, chemoresistance is common and its mechanisms are poorly understood. Here, label-free multi-modal nonlinear optical microscopy was applied to study microstructural and functional features of pancreatic tumors in vivo to monitor inter- and intra-tumor heterogeneity and treatment response. Patient-derived xenografts with human pancreatic ductal adenocarcinoma were implanted into mice and characterized over five weeks of intraperitoneal chemotherapy (FIRINOX or Gem/NabP) with known responsiveness/resistance. Resistant and responsive tumors exhibited a similar initial metabolic response, but by week 5 the resistant tumor deviated significantly from the responsive tumor, indicating that a representative response may take up to five weeks to appear. This biphasic metabolic response in a chemoresistant tumor reveals the possibility of intra-tumor spatiotemporal heterogeneity of drug responsiveness. These results, though limited by small sample size, suggest the possibility for further work characterizing chemoresistance mechanisms using nonlinear optical microscopy.

For investigating the potential for personalized treatment of pancreatic cancer, two- and three-photon autofluorescence and second and third harmonic generation images were simultaneously generated from in vivo pancreatic tumor patient-derived xenograft (PDX) mice. Two different treatment regimens were administered to PDX mice for 5 weeks and compared. Control mice were treated only with saline. Mice were classified into three groups according to their response to the treatment: responsive, resistant, and control. Optical redox ratios were calculated from tumor regions which showed differences between the responsive group compared to the resistant and control groups.

Simultaneous label-free autofluorescence multi-harmonic (SLAM) microscopy images of treated and non-treated mice with xenografts derived from human pancreatic tumors were acquired and analyzed for evaluation of chemotherapeutic drug response.