Pancreatic cancer is the 4th leading cause of cancer deaths and the mortality rate matches the incidence. The majority of patients have advanced disease at diagnosis and the 2-year survival is a dismal 6%. A number of factors contribute to the challenges in the treatment. One is the disease's genetic heterogeneity such that "one size fit all" approach to treatment development has yielded limited progress and personalized treatment based on individual patient's cancer biology is needed. The other significant challenge is the poor blood supply and perfusion to pancreatic tumor that inhibits the delivery of effective chemotherapeutic drugs. Tumor stroma is increasingly recognized as a collaborator with malignant cells, establishing the microenvironment that promotes metastasis, invasion, and treatment resistance. Stroma is thus a novel target in the treatment of pancreatic cancer. Here we propose to investigate a novel sequential pharmacologic approach to exploit this potential vulnerability: pretreatment with an anti-stromal agent that breaches the tumor-vascular barrier thereby increasing tumor perfusion and permeability, and then followed by administration of an FDA-approved nanoparticulate carrier. The latter can deposit significant concentrations of drug, thereby establishing a persistent slow-release depot in the tumor enabling continuous cell kill. Previously we have demonstrated in a brain tumor model that this intra-tumor depot leads to progressive compromise of tumor vascular integrity. Our preliminary data establish that inhibitors of Sonic Hedgehog (sHH) signaling mediate an increase in tumor vascular permeability in low-passage, patient-derived pancreatic cancers in SCID mice, which have very low intrinsic vascularization. The intra-tumoral deposition of a sterically-stabilized nano-liposomal formulation containing doxorubicin (SSL-DXR) is dramatically increased in animals pre-treated with an sHH inhibitor, leading to an initial shutdown in vascular permeability/perfusion and subsequent tumor regression. Here we propose to investigate the mechanisms by which this sequential therapy mediates the observed effects, optimize the effectiveness of treatment, and survey a broader range of patent-derived pancreatic cancers to ascertain the general effectiveness of this approach. We will also examine the effects of treatment in a genetically engineered model of pancreatic cancer that faithfully recapitulates the stromal amplification and poor vascular permeability/perfusion that are hallmarks of the human disease. Our objective is to lay the groundwork that would provide strong rationale for clinical evaluation of sequential pharmacologic-based treatment of pancreatic cancer by combining SHH inhibitors in a specific sequence with a first-in-class, FDA- approved, nanoparticulate drug delivery agent.
Pancreatic cancer is a lethal disease to the vast majority of patients for three reasons: first, the disease is advanced when discovered;second, the blood flow to the tumor is so low that drugs cannot easily gain access to the tumor;third, given the range of mutations that have been discovered in the cancer cells, it is usually not possible to anticipate which drugs will be most effective for a particular patent. This project seeks to address the second two factors, which apply to the vast majority of patients who have advanced disease: (i) we have found that a new class of drugs that attacks the normal cells in the tumor matrix, rather than the tumor cells themselves, can increase the amounts of nanoparticle drug carriers that can gain access to the tumor and thereby deposit large amounts of cytotoxic drugs;(ii) we will use authentic patient tumors (implanted in mice) as targets when we develop these therapies, so we will be able to anticipate whether the approaches (and drugs employed) are effective against a majority of patient cancers. The near-term outcome of this project will be to provide strong rationale for clinical trials of the unique combination therapy approach we seek to develop and evaluate in this proposal.