Fig. 2. PDP increases tumor vascular permeability to enhance nal-IRI delivery in an orthotopic PDAC model.

Orthotopic MIA PaCa-2 tumors were exposed to 75 J/cm² of light (100 mW/cm²) one-hour following intravenous injection of nal-BPD (0.25 mg/kg) and a single dose of Dil5-nal-IRI (20 mg/kg). Control tumors were only injected with Dil5-nal-IRI (20 mg/kg) without light treatment. (A) Representative confocal fluorescence microscopy images of control tumors (top row) and PDP-treated tumors (bottom row) obtained 4 hours after intravenous injection Dil5-nal-IRI. In presence of PDP, Dil5-nal-IRI (red) was widely distributed throughout the tumor tissue and extravasated from the blood vessels (tomato lectin staining; green), whereas the signals arising from Dil5-nal-IRI in control tumors were confined to the immediate vicinity of the tumor blood vessels. No Dil5-nal-IRI signal was detected in the tumors treated with PDP alone. Nuclear staining (blue-fluorescence, DAPI); Scale bar 200 μm. (B, C) Quantitative analyses of Dil5-nal-IRI fluorescence intensity (B) and distribution (C) showing PDP significantly enhanced Dil5-nal-IRI accumulation and extravasation within MIA PaCa-2 tumors 4 and 24 hours after Dil5-nal-IRI injection (n ≥ 3 animals per group; n ≥ 19 images per group; ***P<0.001, Bonferroni-corrected Mann-Whitney U test). (D, E) PDP mediated changes in tumor pharmacokinetic profile of nal-IRI. Swiss nude mice bearing orthotopic MIA PaCa-2 tumors were treated with a single cycle of nal-IRI (nal-IRI, 20 mg/kg; IV) (red line; solid square) or a combination of PDP and single cycle nal-IRI (20 mg/kg; IV) (blue line; solid circle). Tumors were collected at various intervals and the irinotecan (d) and SN-38 (e) levels were measured by HPLC analysis (n ≥ 5 per time point; ***P<0.01, **P=0.022, *P<0.05, Bonferroni-corrected Mann-Whitney U test). (F) Carboxylesterase (CES) activities in MIA PaCa-2 tumors were not modulated by PDP at various time posts after treatment (n = 3–9 animals per condition; ns, non-significant, Kruskal–Wallis one-way ANOVA). (G) Comparison of tumoral irinotecan to SN-38 molar ratio at various time-points between ‘single cycle nal-IRI’ monotherapy and ‘PDP + single cycle nal-IRI’ arm. (n ≥ 5 per time point; Solid lines are nonlinear fits; n.s., non-significant, P=0.79, two-way ANOVA PDP·time interaction term). Results are mean ± standard error of the mean (SEM).