S. Modi1, X. Zhao1, A. Nomura1, V. Dudeja1, S. Banerjee1, A. K. Saluja1 1University Of Minnesota,Surgery,Minneapolis, MN, USA
Introduction: Pancreatic cancer (PDA) is an aggressive disease which is resistant to conventional therapeutic approaches. Although there are multitudes of reasons for its aggressiveness, recent studies suggest that cancer stroma and stellate cells play a major role in tumor aggressiveness. PDA is extremely desmoplastic; almost 90% of the tumor is stroma. Pancreatic stellate cells (PSCs) contribute extensively to this desmoplastic reaction. PSCs are activated by cancer cells, and vice versa leading this feedback loop to create a niche for pancreatic cancer in the primary and metastatic lesions. Triptolide (TPL) is a terpenoid compound with therapeutic potential against various cancers including PDA. The aim of this study is to evaluate whether triptolide and its water soluble prodrug, Minnelide (currently in Phase I trials), could inhibit the cancer cell-stellate cell cross talk to effectively suppress pancreatic cancer growth.
Methods: In vitro, we used human PSCs and two human PCC lines: S2-VP10 and MIA PaCa-2. The effect of various chemotherapeutic drugs (Gemcitabine, Paclitaxel, TPL, and TRAIL) on the viability of these cells was evaluated using the WST-8 assay. The PCC-PSC interaction was studied by co-culturing the cells in transwell chambers. Effects of pretreatment of one cell type with TPL were studied on the other cell type in a co-culture setup. . Viability, migration and invasion were measured using the WST-8 and the Boyden chamber assay respectively. Expression of various ECM components (collagen, fibronectin), activation (αSMA, vimentin), and invasion markers (N-cadherin, MMPs) was estimated using qPCR and Western Blot.
In vivo, quantification of desmoplastic reaction in the spontaneous pancreatic cancer murine model (KPC) was done by measuring collagen and αSMA expression in the Minnelide and saline treated tumors. Kaplan-Meier survival curves were obtained for same model comparing the two groups.
Results: Viability of PCCs was significantly decreased by various drugs while PSCs were only affected by TPL treatment. The proliferation of MIA PaCa-2 and S2-VP10 was markedly augmented in co-culture with untreated PSCs while TPL pre-treated PSCs did not show this effect. The invasive phenotype of PCCs, as suggested by their migration and invasion, was significantly augmented by co-culture with untreated PSCs while co-culture with TPL pre-treated PSCs failed to do so. TPL treatment resulted in decreased expression of αSMA, fibronectin HSF-1, HSP 70 and 47 in PSCs and reduced collagen production as compared to other drugs.
Minnelide treated tumors in KPC mice had significantly decreased collagen and αSMA content. Minnelide treatment also increased the survival of these mice significantly as compared to saline arm
Conclusion: Our findings indicate that triptolide/Minnelide effectively targets ductal cancerous compartment and its associated stroma leading to disruption of the tumor-stroma interaction in pancreatic cancer.