Pharmacological Regulation of Tumor Hypoxia in Model Murine Tumors and Spontaneous Canine Tumors

Background: Hypoxia is found in many solid tumors and is associated with increased disease aggressiveness and resistance to therapy. Reducing oxygen demand by targeting mitochondrial oxidative metabolism is an emerging concept in translational cancer research aimed at reducing hypoxia. We have shown that the U.S. Food and Drug Administration (FDA)-approved drug papaverine and its novel derivative SMV-32 are potent mitochondrial complex I inhibitors. Methods: We used a dynamic in vivo luciferase reporter system, pODD-Luc, to evaluate the impact of pharmacological manipulation of mitochondrial metabolism on the levels of tumor hypoxia in transplanted mouse tumors. We also imaged canine patients with blood oxygen level-dependent (BOLD) MRI at baseline and one hour after a dose of 1 or 2 mg/kg papaverine. Results: We showed that the pharmacological suppression of mitochondrial oxygen consumption (OCR) in tumor-bearing mice increases tumor oxygenation, while the stimulation of mitochondrial OCR decreases tumor oxygenation. In parallel experiments in a small series of spontaneous canine sarcomas treated at The Ohio State University (OSU) Veterinary Medical Center, we observed a significant increase in BOLD signals indicative of an increase in tumor oxygenation of up to 10–50 mm HgO2. Conclusion: In both transplanted murine tumors and spontaneous canine tumors we found that decreasing mitochondrial metabolism can decrease tumor hypoxia, potentially offering a therapeutic advantage.

MODL-27. MEK INHIBITION WITH TRAMETINIB SLOWS PROGRESSION OF MEDULLOBLASTOMA AND ATYPICAL TERATOID RHABDOID TUMOR IN ORTHOTOPIC XENOGRAFT MURINE MODEL

BACKGROUND Combination of surgery, chemotherapy, autologous transplantation, irradiation constitutes treatment of CNS embryonal-cell tumors (Medulloblastoma-MBL, atypical teratoid rhabdoid tumor-AT/RT). Targeted agents to improve survival and decrease side effects are necessary. We hypothesize that inhibiting MAPK pathway in MBL and AT/RT may be beneficial. METHODS IHC(pERK) was performed on clinical tumors. Trametinib(MEK inhibitor) was tested on MBL(UW228, D283, DAOY); AT/RT(CHLA06, BT12) cell-lines. Luminescent cell-viability assay was done(72 hrs) and with crystal violet assay(10 days). Orthotopic, xenografts of MBL and AT/RT were made in NOD-Scid gamma mice. Mice were given Trametinib daily by gavage for 6 weeks(0.6mg/kg b.w). Western blot was performed on protein from cell lines and tumor xenografts incubated with Trametinib. H&E staining was done on murine tumors. RESULTS AT/RT(48%) and MBL(57%); Anaplastic(50%), Desmoplastic(40%), Classic(38%); Group 4(66%), Group 3(20%), SHH(55%), WNT(0%) showed presence of pERK(clinical samples). In-vitro, Trametinib completely abrogated the phosphorylation of ERK at 125nM in AT/RT and 50nM in MBL. The IC50 after 10 days exposure was 10nM for AT/RT and 35nM for MBL. Trametinib treated mice showed delay in tumor growth and significant survival advantage in both AT/RT (p=0.00336) and MBL (p=0.0069). Murine tumors showed decreased proliferation (H&E). CONCLUSION Trametinib decreased cell proliferation, increased survival in our murine model in both MBL and AT/RT. Pre-clinical results indicate benefits in subgroups of AT/RT and MBL with active MAPK pathway.