Evaluation of triptolide pro-drug (Minnelide) as an anti-stromal and anti-tumoral therapeutic option for pancreatic cancer.

Abstract

262 Background: In pancreatic cancer, the stromal microenvironment is considered to be the major reason behind the failure of conventional and targeted therapy. The desmoplastic stroma is responsible for compression of vasculature in the tumor resulting in impaired drug delivery. Pancreatic stellate cells contribute extensively to this desmoplastic reaction. Our group has recently evaluated a water-soluble pro-drug of triptolide (Minnelide) in pre-clinical studies for pancreatic cancer with very promising results. The current study evaluates the ability of Minnelide to deplete the stromal architecture and the stellate cell population in pancreatic cancer resulting in increased drug delivery. Methods: Patient tumor xenografts in SCID mice (PDX) and KRASG12DTP53-PDX-Cre spontaneous pancreatic tumor mice (KPC) were treated with 0.42mg/kg Minnelide. Vascular patency was studied by terminal perfusion of mice with 4% PFA following injection with tomato lectin. Drug delivery was determined by quantitating accumulated doxorubicin in the tumor tissue. Cell viability was studied by MTT assay and the invasion of cells in vitro was studied using Boyden Chamber assay. Results: Minnelide treatment decreased Hyaluronic acid (HA) in PDX (48% of control) as well as in KPC model (52% of control). Expression of HA synthase (HAS) genes were decreased in both tumor models in response to Minnelide (22% of control in PDX and 35% of control in KPC tumors). HAS Enzyme activity also consistently decreased in both the models after treatment with Minnelide (28% of control in PDX and 31% of control in KPC). In vitro, triptolide decreased the invasion of the tumor cells towards the stellate cells indicating an inhibition of crosstalk. Treatment with Minnelide resulted in “open” and functional vessels in the treated animals resulting in increased drug delivery. Median survival of animals increased by 38 days after treatment with Minnelide. Conclusions: Our study showed that Minnelide depleted the stromal architecture leading to increased functional vasculature and enhanced drug delivery in the tumor. This is an extremely promising observation for Minnelide that is currently under clinical trial.