Tumors grown in a stroma-rich mouse model resembling clinically advanced bladder
carcinoma with UMUC3 and NIH 3T3 cells have high levels of fibroblasts and an accelerated
tumor growth rate. We used this model to investigate the synergistic effect of combined
gemcitabine monophosphate (GMP) nanoparticles and
Cisplatin nanoparticles (Combo NP) on tumor-associated fibroblasts (TAFs). A single injection of Combo NP had synergistic anti-
tumor effects while the same molar ratio of combined GMP and
Cisplatin delivered as free
drug (Combo Free) fell outside of the synergistic range. Combo NP nearly halted
tumor growth with little evidence of general toxicity while Combo Free had only a modest inhibitory effect at 16mg/kg GMP and 1.6mg/kg
Cisplatin. Combo NP increased levels of apoptosis within the
tumor by approximately 1.3 folds (TUNEL analysis) and decreased α-SMA-positive fibroblast recruitment by more than 87% (immunofluorescence) after multiple
injections compared with Combo Free, GMP NP or
Cisplatin NP alone. The TAF-targeting capability of Combo NP was evaluated by double staining for TUNEL and α-SMA at various time points after a single injection. On day one after injection, 57% of the TUNEL-positive cells were identified as α-SMA-positive fibroblasts. By day four,
tumor stroma was 85% depleted and 87% of the remaining TAFs were TUNEL-positive. Combo NP-treated
tumors became 2.75 folds more permeable than those treated with Combo Free as measured by
Evans Blue. We conclude that the
antineoplastic effect of Combo NP works by first targeting TAFs and is more effective as an anti-
tumor therapy than Combo Free, GMP NP or
Cisplatin NP alone.