Abstract 3796: Pegylated human recombinant hyaluronidase PH20 reduces solid tumor hypoxia
Authors: Li Xiaoming , Jiang Ping , Symons Rebecca , Osgood Ryan J. , Shepard H Michael , Maneval Daniel C. , Thompson Curtis B. 
Published: August 2012

Tumor hypoxia, the pathophysiological result of the structural and functional disruption of the tumor microcirculation and the deterioration of normal diffusion geometry, is strongly associated with tumor proliferation and resistance to therapy, both chemotherapy and radiotherapy. Indeed, hypoxia-associated resistance to photon radiotherapy is a severe clinical problem, as the radiation doses required to achieve the same treatment effect in hypoxic tumors can be three times the doses required in normoxic tumors. The extracellular matrix (ECM) glycosaminoglycan hyaluronan (HA) accumulates to high levels in ∼30% of solid tumors. Since HA is highly hydrophilic, ECM HA accumulation is believed to contribute to the elevated interstitial fluid pressure (IFP) and subsequent tumor vessel constriction observed in solid tumors. This vascular constriction contributes to the pathologic hypoxia present in these tumors. PEGPH20, a pegylated human recombinant hyaluronidase PH20, when delivered intravenously in preclinical models has been shown to enzymatically remove tumor HA and decrease both tumor IFP and water, leading to increased tumor vascular perfusion and enhanced chemotherapeutic delivery (Thompson 2010). Here we aimed to extend these observations and determine whether PEGPH20 would both increase tumor blood flow and reduce tumor hypoxia following PEGPH20-mediated HA removal. Nude mice were inoculated with human BxPC-3 pancreatic cancer cells adjacent to the right tibial periosteum. When tumors reached 15-20 mm in diameter (nα8/group), mice were staged into two treatment groups: (1) vehicle control and (2) PEGPH20 monotherapy. Vehicle or PEGPH20 (4.5 mg/kg) was administered to animals intravenously twice weekly for one week. The hypoxyprobe pimonidazole (60 mg/kg, ip) was administered to animals two hours prior to sacrifice, and fluorescent carbocyanine (75 μL, iv) 5 minutes prior to sacrifice. At sacrifice, whole tumors were removed, bisected, embedded in OCT medium, and processed for immunohistochemistry (hypoxyprobe and CD31) or simply imaged microscopically (carbocyanine). Hypoxia, blood vessel position, and tumor perfusion were assessed using pimonidazole, CD31 and carbocyanine, respectively. Compound images were created and the spatial relationship between hypoxia and vasculature perfusion evaluated. Consistent with prior studies, tumor HA was depleted in the PEGPH20-treated tumors. Further, tumor vascular perfusion (carbocyanine) increased 86% (p=0.0007) and tumor hypoxia decreased by 66% (p=0.03) in PEGPH20-treated animals, relative to the vehicle controls. These findings suggest that PEGPH20-mediated reduction in tumor HA increases tumor perfusion, while concomitantly reducing tumor hypoxia.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3796. doi:1538-7445.AM2012-3796