pd-0325901 and Colonic-Neoplasms

To assess further the tolerability and preliminary antitumor activity of PD-0325901 in previously treated patients with advanced melanoma, breast cancer, and colon cancer.. This pilot study evaluated PD-0325901 on an intermittent dosing schedule. PD-0325901 was administered orally at 20 mg twice daily (BID) for 21 consecutive days followed by 7 days of no treatment. This dose was not well tolerated and consequently changed to 15 mg BID.. Between October and December 2005, 13 patients with metastatic measurable disease were entered into the study (seven melanoma, three breast cancer, and three colon cancer). All patients had received prior systemic therapy and were treated with a total of 61 cycles of PD-0325901 (nine received an initial dose of 20 mg BID, four an initial dose of 15 mg BID). The study was terminated early because of an unexpected high incidence of musculoskeletal and neurological adverse events, including gait disturbance, memory impairment, confusion, mental status changes, mild to moderate visual disturbances, and muscular weakness including neck weakness ("dropped-head syndrome"). Other common toxicities were diarrhea, acneiform rash, fatigue, and nausea. There was no significant hematologic toxicity, and chemistry abnormalities were rare. One patient achieved a confirmed complete response, and five patients had stable disease.. PD-0325901 can cause significant musculoskeletal, neurological, and ocular toxicity at doses ≥ 15 mg BID. Future studies with adaptive designs might evaluate doses ≤ 10 mg BID in tumor types with a high incidence of Ras and Raf mutations. ClinicalTrials.gov identifier NCT00147550.

Topics: Adult; Aged; Aged, 80 and over; Antineoplastic Agents; Benzamides; Breast Neoplasms; Cohort Studies; Colonic Neoplasms; Diphenylamine; Early Termination of Clinical Trials; Extracellular Signal-Regulated MAP Kinases; Eye Diseases; Female; Humans; Male; Melanoma; Middle Aged; Musculoskeletal Diseases; Neoplasm Staging; Neurotoxicity Syndromes; Pilot Projects

MicroRNAs (miRNAs) are small non-coding RNAs, and the deregulated expression of miRNAs is associated with tumor development. Among these, the miR-17-92 cluster, including six mature miRNAs, is known as an oncogenic miRNA cluster because expression of the miR-17-92 cluster is frequently elevated in a variety of malignant tumors.. We investigated whether a mitogen-activated protein kinase kinase (MEK) inhibitor, PD0325901, suppresses expression of the miR-17-92 cluster in HT-29 human colon cancer cells and MIA PaCa-2 pancreatic cancer cells.. PD0325901 inhibited cell growth with G1-phase arrest and suppressed expression of the miR-17-92 cluster. Furthermore, phosphatase and tensin homolog (PTEN), which is a target molecule of the miR-17-92 cluster, was up-regulated by PD0325901. The exogenous expression of miR-17 slightly, but significantly reduced G1-phase arrest by PD0325901.. These results raise the possibility that a MEK inhibitor causes G1-phase arrest, at least partially, through suppression of the miR-17-92 cluster.

Topics: Benzamides; Cell Cycle; Cell Cycle Checkpoints; Cell Line, Tumor; Cell Proliferation; Colonic Neoplasms; Diphenylamine; Down-Regulation; Enzyme Inhibitors; G1 Phase; Gene Expression Regulation, Neoplastic; HT29 Cells; Humans; MAP Kinase Kinase Kinases; MicroRNAs; Multigene Family; Mutation; PTEN Phosphohydrolase; RNA, Long Noncoding

Mutational activation of KRAS is a common event in human tumors. Identification of the key signaling pathways downstream of mutant KRAS is essential for our understanding of how to pharmacologically target these cancers in patients. We show that PD0325901, a small-molecule MEK inhibitor, decreases MEK/ERK pathway signaling and destabilizes cyclin D1, resulting in significant anticancer activity in a subset of KRAS mutant tumors in vitro and in vivo. Mutational activation of PIK3CA, which commonly co-occurs with KRAS mutation, provides resistance to MEK inhibition through reactivation of AKT signaling. Genetic ablation of the mutant PIK3CA allele in MEK inhibitor-resistant cells restores MEK pathway sensitivity, and re-expression of mutant PIK3CA reinstates the resistance, highlighting the importance of this mutation in resistance to therapy in human cancers. In KRAS mutant tumors, PIK3CA mutation restores cyclin D1 expression and G(1)-S cell cycle progression so that they are no longer dependent on KRAS and MEK/ERK signaling. Furthermore, the growth of KRAS mutant tumors with coexistent PIK3CA mutations in vivo is profoundly inhibited with combined pharmacologic inhibition of MEK and AKT. These data suggest that tumors with both KRAS and phosphoinositide 3-kinase mutations are unlikely to respond to the inhibition of the MEK pathway alone but will require effective inhibition of both MEK and phosphoinositide 3-kinase/AKT pathway signaling.

Topics: Alleles; Animals; Benzamides; Cell Growth Processes; Cell Line, Tumor; Class I Phosphatidylinositol 3-Kinases; Colonic Neoplasms; Cyclin D1; Diphenylamine; Extracellular Signal-Regulated MAP Kinases; Gene Knockout Techniques; HCT116 Cells; Humans; Lung Neoplasms; MAP Kinase Kinase Kinases; MAP Kinase Signaling System; Mice; Mutation; Pancreatic Neoplasms; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-akt; Proto-Oncogene Proteins p21(ras); ras Proteins

The RAS pathway is one of the most frequently deregulated pathways in cancer. RAS signals through multiple effector pathways, including the RAF/mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) kinase (MEK)/ERK MAPK and phosphatidylinositol 3-kinase (PI3K)-AKT signaling cascades. The oncogenic potential of these effector pathways is illustrated by the frequent occurrence of activating mutations in BRAF and PIK3CA as well as loss-of-function mutations in the tumor suppressor PTEN, a negative regulator of PI3K. Previous studies have found that whereas BRAF mutant cancers are highly sensitive to MEK inhibition, RAS mutant cancers exhibit a more variable response. The molecular mechanisms responsible for this heterogeneous response remain unclear. In this study, we show that PI3K pathway activation strongly influences the sensitivity of RAS mutant cells to MEK inhibitors. Activating mutations in PIK3CA reduce the sensitivity to MEK inhibition, whereas PTEN mutations seem to cause complete resistance. We further show that down-regulation of PIK3CA resensitizes cells with co-occurring KRAS and PIK3CA mutations to MEK inhibition. At the molecular level, the dual inhibition of both pathways seems to be required for complete inhibition of the downstream mammalian target of rapamycin effector pathway and results in the induction of cell death. Finally, we show that whereas inactivation of either the MEK or PI3K pathway leads to partial tumor growth inhibition, targeted inhibition of both pathways is required to achieve tumor stasis. Our study provides molecular insights that help explain the heterogeneous response of KRAS mutant cancers to MEK pathway inhibition and presents a strong rationale for the clinical testing of combination MEK and PI3K targeted therapies.

Topics: Animals; Antineoplastic Agents; Apoptosis; Benzamides; Cell Division; Cell Line, Tumor; Colonic Neoplasms; Diphenylamine; Doxycycline; Enzyme Activation; Female; Genes, ras; HCT116 Cells; Humans; Mice; Mice, Nude; Mutation; Phosphatidylinositol 3-Kinases; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Transplantation, Heterologous

Current radiotracers for positron emission tomography imaging of choline metabolism have poor systemic metabolic stability in vivo. We describe a novel radiotracer, [(18)F]fluoromethyl-[1,2-(2)H(4)]-choline (D4-FCH), that employs deuterium isotope effect to improve metabolic stability. D4-FCH proved more resistant to oxidation than its nondeuterated analogue, [(18)F]fluoromethylcholine, in plasma, kidneys, liver, and tumor, while retaining phosphorylation potential. Tumor radiotracer levels, a determinant of sensitivity in imaging studies, were improved by deuterium substitution; tumor uptake values expressed as percent injected dose per voxel at 60 min were 7.43 +/- 0.47 and 5.50 +/- 0.49 for D4-FCH and [(18)F]fluoromethylcholine, respectively (P = 0.04). D4-FCH was also found to be a useful response biomarker. Treatment with the mitogenic extracellular kinase inhibitor PD0325901 resulted in a reduction in tumor radiotracer uptake that occurred in parallel with reductions in choline kinase A expression. In conclusion, D4-FCH is a very promising metabolically stable radiotracer for imaging choline metabolism in tumors.

Topics: Animals; Benzamides; Choline; Colonic Neoplasms; Deuterium; Diphenylamine; HCT116 Cells; Humans; Melanoma; Mice; Mice, Inbred BALB C; Mice, Nude; Oxidation-Reduction; Positron-Emission Tomography; Radiopharmaceuticals; Tissue Distribution; Transplantation, Heterologous