Presentation Authors: Justin Penticuff*, Sambantham Shanmugam, Erika Abbott, Benjamin Woolbright, John Taylor, Kansas City, KS
Introduction: PDK4 is a member of the PDK enzyme family which phosphorylate and inactivate the pyruvate dehydrogenase (PDH) complex, promoting aerobic glycolysis, known as the Warburg Effect. Studies indicate that this switch confers growth advantages as well as resistance to chemotherapy. We have previously reported substantial upregulation of PDK4 (33-fold) in high grade, invasive vs. low grade bladder cancers. We hypothesized that inhibition of PDK4 would reduce tumor growth both in vitro and in vivo and sensitize bladder cancer cells to cisplatin.
Methods: Authenticated human high-grade bladder cancer cell lines HTB-9, HT-1376, HTB-5, and HTB-4 were utilized, as well as benign UROtsa cell lines. Animals were housed in a controlled environment with a 12-hour light/12-hour dark cycle and provided food and water ad lib. Pyruvate dehydrogenase (PDH) activity was performed using Sigma PDH Activity Assay (Sigma Aldrich). For the xenograft tumor gowth model, male nude mice (Crl nu/nu) were inoculated on right flank with 2 x106 HTB9 cells in a matrigel (5 mg/mL) suspension (1:1). Treatment with DCA (200 mg/kg/day via oral gavage) and/or cisplatin (6 mg/kg intraperitoneal weekly). For the BBN (N-butyl-N-(4-hydroxybutyl)-nitrosamine) model, 4-5 week old C57Bl/6J mice were given 0.05% BBN in the drinking water for 16 weeks. At this point, normal water was returned and mice were put on treatment.
Results: PDK4 was overexpressed in multiple bladder cancer cell lines. Treatment with dichloroacetate (DCA), a PDK 1-4 inhibitor, significantly increased PDH activity, reduced proliferation, and sensitized HTB-9 and HTB-5 cells to cisplatin induced cell death. Treatment of HTB-9 tumor xenografts with DCA or cisplatin did not reduce tumor volumes, however, co-treatment with both compounds resulted in significant reductions in viable tumor weights. PS10 (PDK2/4 inhibitor) treatment significantly increased PDH activity, sensitized UM-UC3 cells to cisplatin and reduced cellular proliferation. In the BBN model, PS10 alone had no effect. While cisplatin reduced bladder weights, only the PS10 plus cisplatin group resulted in a significant reduction in bladder tumor weight.
Conclusions: Inhibition of PDK4 sensitizes bladder cancers to cisplatin both in vitro and in multiple models in vivo, as well as having direct anti-proliferative effects in vitro. PDK inhibition may be a useful and novel way to enhance cisplatin based therapies in bladder cancer or directly target certain cancer subtypes.
Source of Funding: The Leo and Anne Albert Charitable Trust