Wells A. Messersmith

Dual pharmacological targeting of the MAP kinase and PI3K/mTOR pathway in preclinical models of colorectal cancer.

Background The activation of the MAPK and PI3K/AKT/mTOR pathways is implicated in the majority of cancers. Activating mutations in both of these pathways has been described in colorectal cancer (CRC), thus indicating their potential as therapeutic targets. This study evaluated the combination of a PI3K/mTOR inhibitor (PF-04691502/PF-502) in combination with a MEK inhibitor (PD-0325901/PD-901) in CRC cell lines and patient-derived CRC tumor xenograft models (PDTX). Materials and Methods The anti-proliferative effects of PF-502 and PD-901 were assessed as single agents and in combination against a panel of CRC cell lines with various molecular backgrounds. Synergy was evaluated using the Bliss Additivity method. In selected cell lines, we investigated the combination effects on downstream effectors by immunoblotting. The combination was then evaluated in several fully genetically annotated CRC PDTX models. Results The in vitro experiments demonstrated a wide range of IC50 values for both agents against a cell line panel. The combination of PF-502 and PD-901 demonstrated synergistic anti-proliferative activity with Bliss values in the additive range. As expected, p-AKT and p-ERK were downregulated by PF-502 and PD-901, respectively. In PDTX models, following a 30-day exposure to PF-502, PD-901 or the combination, the combination demonstrated enhanced reduction in tumor growth as compared to either single agent regardless of KRAS or PI3K mutational status. Conclusions The combination of a PI3K/mTOR and a MEK inhibitor demonstrated enhanced anti-proliferative effects against CRC cell lines and PDTX models.

AGA White Paper: Optimizing Endoscopic Ultrasound–Guided Tissue Acquisition and Future Directions

*Division of Gastroenterology and Hepatology, University of Colorado Anschutz Medical Campus, Aurora, Colorado; Vatche and Tamar Manoukian Division of Digestive Diseases, University of California, Los Angeles, Los Angeles, California; Department of Pathology and Laboratory Medicine, Perelman School of Medicine and University of Pennsylvania Medical Center, Philadelphia, Pennsylvania; kDepartment of Pathology and Cell Biology, Columbia University, New York, New York; Arizona Center for Digestive Health, Gilbert, Arizona; Division of Medical Oncology, University of Colorado Anschutz Medical Campus, Aurora, Colorado; **Division of Gastroenterology, Perelman School of Medicine and the University of Pennsylvania Medical Center, Philadelphia, Pennsylvania; and Division of Gastroenterology and Hepatology, Ochsner Medical Center, New Orleans, Louisiana

Combined inhibition of MEK and Aurora A kinase in KRAS/PIK3CA double-mutant colorectal cancer models

Aurora A kinase and MEK inhibitors induce different, and potentially complementary, effects on the cell cycle of malignant cells, suggesting a rational basis for utilizing these agents in combination. In this work, the combination of an Aurora A kinase and MEK inhibitor was evaluated in pre-clinical colorectal cancer models, with a focus on identifying a subpopulation in which it might be most effective. Increased synergistic activity of the drug combination was identified in colorectal cancer cell lines with concomitant KRAS and PIK3CA mutations. Anti-proliferative effects were observed upon treatment of these double-mutant cell lines with the drug combination, and tumor growth inhibition was observed in double-mutant human tumor xenografts, though effects were variable within this subset. Additional evaluation suggests that degree of G2/M delay and p53 mutation status affect apoptotic activity induced by combination therapy with an Aurora A kinase and MEK inhibitor in KRAS and PIK3CA mutant colorectal cancer. Overall, in vitro and in vivo testing was unable to identify a subset of colorectal cancer that was consistently responsive to the combination of a MEK and Aurora A kinase inhibitor.

Phase I Clinical Trials with Anticancer Agents

Although the term “phase I” is used to describe numerous trial designs, the overarching goal of a phase I study is to determine the optimal dose and/or schedule of a therapy for evaluation in the phase II setting. Phase I trials typically test different doses of an anticancer agent(s) in various neoplastic diseases, with safety evaluation as a main objective. These studies range from first-in-human trials of novel single agents to new combinations of FDA-approved therapies. Frequently, pharmacokinetic studies are incorporated in phase I clinical trials, in order to determine drug exposure and clearance. In addition, phase I studies may include biomarkers of drug effects such as functional imaging or direct measurement of drug effects on either tumor biopsies and/or normal tissue samples.

Abstract C176: Activity of novel indolequinone inhibitors of thioredoxin reductase 1 in pancreatic and colon cancers and in melanomas. Signaling mechanisms underlying antiproliferative activity.

Novel indolequinones (including QG001, 5-methoxy-1-methyl-3-[(2,4,6-trifluorophenoxy)methyl]-1H-indole-4,7-dione and NJ824, 2-(hydroxymethyl)-5-methoxy-1-methyl-3-[(4-nitrophenoxy)methyl]indole-4,7-dione) demonstrated marked anti-proliferative activity in MIAPaCa-2 and BxPC-3 pancreatic cancer cells as well as in colon, melanoma and renal cell lines as indicated by testing in the NCI-60 cell line screen. In studies using MIAPaCa-2 and BxPC-3 cell lines we examined the mechanism of action of lead IQs and results demonstrated inhibition of the selenoprotein thioredoxin reductase 1 (TR1) and induction of apoptosis in pancreatic cell lines at doses approximating their IC50 values obtained from MTT growth inhibition assays. Other selenoproteins such as glutathione peroxidase were not inhibited and the depletion of cellular thiols was not observed following treatment with lead IQs indicating target selectivity. The mechanisms underlying IQ-induced apoptosis were investigated and lead IQs were found to induce oxidation of cellular thioredoxin subsequent to inhibition of thioredoxin reductase 1 and downstream activation of p38 and JNK leading to apoptosis. IQ-induced apoptosis could be inhibited by the use of p38 and JNK inhibitors in MIAPaCa-2 cells confirming the importance of this pathway. The role of ASK1 as an intermediary MAPKKK modulating signaling from oxidation of thioredoxin to activation of p38 and JNK was investigated in MIAPaCa-2 cells overexpressing ASK1 and lead IQs were found to induce ASK1 phosphorylation. Studies were extended to panels of eighteen human colorectal cancers and nineteen pancreatic cancer cell lines and lead IQs were found to exhibit marked growth inhibitory activity with IC50 values ranging from 0.05 to 0.5 micromolar. In vivo studies were performed in xenograft systems and lead IQs demonstrated significant growth inhibitory activity in both pancreatic and melanoma xenografts. These data demonstrate that this class of IQ has marked growth inhibitory activity in pancreatic, colon and melanoma tumors and are worthy of further translational evaluation as potential therapeutics. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr C176.