Colony forming unit (CFU) enumeration of ST in tumors of mice treated with and without PEGPH20. Mice with 14-day orthotopic KPC tumors (n=3) were given indicated treatment regimens. Tumors were then extracted at indicated time points post-treatment, homogenized in PBS containing a protease inhibitor mix (Roche), plated on LB-0 plates containing appropriate antibiotics, and then incubated at 37ï‚°C overnight. Data is representative of multiple experiments utilizing identical treatments and post-treatment analyses. (A) CFU comparison of mice treated with ST, with and without PEGPH20, at various time points after treatment. (B) Effects of Gr-1 depletion (Gr1-) on accumulation of shIDO-ST in orthotopic KPC tumors in mice treated with and without PEGPH20. Mice were depleted 24hr prior to treatment. Tumors were extracted 48hr post-treatment and homogenized for CFU enumeration. *p<0.05, **p<0.01, 1-way ANOVA.
ARTICLE ABSTRACTBacterial-based therapies are emerging as effective cancer treatments and hold promise for refractory neoplasms, such as pancreatic ductal adenocarcinoma (PDAC), which has not shown significant improvement in therapy for more than 25 years. Using a novel combination of shIDO-ST, a Salmonella-based therapy targeting the immunosuppressive molecule indoleamine 2,3-dioxygenase (IDO), with an enzyme, PEGPH20, which depletes extracellular matrix hyaluronan, we observed extended survival with frequent total regression of autochthonous and orthotopic PDAC tumors. This observation was associated with migration and accumulation of activated polymorphonuclear neutrophils (PMN) from spleens into tumors, which was not seen using a scrambled control (shScr-ST). Purified splenic PMNs from PEGPH20/shIDO-ST-treated mice exhibited significant IDO knockdown and were able to kill tumor targets ex vivo through mechanisms involving FasL and serine proteases. In addition, CD8+ T cells were observed to contribute to late control of pancreatic tumors. Collectively, our data demonstrate that entry of shIDO-ST and PMNs into otherwise impermeable desmoplastic tumors is facilitated by PEGPH20-mediated HA removal, further highlighting an important component of effective treatment for PDAC. Cancer Immunol Res; 3(9); 1096–107. ©2015 AACR.