mk-2206 and Thyroid-Neoplasms

The BRAF V600E mutation is commonly observed in papillary thyroid cancer (PTC) and predominantly activates the MAPK pathway. Presence of BRAF V600E predicts increasing risk of recurrence and higher mortality rate, and treatment options for such patients are limited. Vemurafenib, a BRAF V600E inhibitor, is initially effective, but cells inevitably develop alternative mechanisms of pathway activation. Mechanisms of primary resistance have been described in short-term cultures of PTC cells; however, mechanisms of acquired resistance have not. In the present study, we investigated possible adaptive mechanisms of BRAF V600E inhibitor resistance in KTC1 thyroid cancer cells following long-term vemurafenib exposure. We found that a subpopulation of KTC1 cells acquired resistance to vemurafenib following 5 months of treatment with the inhibitor. Resistance coincided with the spontaneous acquisition of a KRAS G12D activating mutation. Increases in activated AKT, ERK1/2, and EGFR were observed in these cells. In addition, the resistant cells were less sensitive to combinations of vemurafenib and MEK1 inhibitor or AKT inhibitor. These results support the KRAS G12D mutation as a genetic mechanism of spontaneously acquired secondary BRAF inhibitor resistance in BRAF V600E thyroid cancer cells.

Topics: Aged; Antineoplastic Agents; Benzimidazoles; Carcinoma, Papillary; Cell Line, Tumor; Drug Resistance, Neoplasm; Enzyme Inhibitors; ErbB Receptors; Female; Gain of Function Mutation; Gene Knockdown Techniques; Heterocyclic Compounds, 3-Ring; Humans; Indoles; Male; MAP Kinase Kinase 1; MAP Kinase Signaling System; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; Proto-Oncogene Proteins B-raf; Proto-Oncogene Proteins c-akt; Proto-Oncogene Proteins p21(ras); Pyridones; Pyrimidines; RNA Interference; RNA, Small Interfering; Sulfonamides; Thyroid Cancer, Papillary; Thyroid Neoplasms; Vemurafenib

A major challenge in tumor therapy is the decrease or even the halting of cell proliferation and migration of cancerous cells. In the present study, we have analyzed the impact of a pharmacological blockade of the PI3K/Akt and MAPK/ERK1/2 signaling pathways on cell migration, proliferation and cell death in three human thyroid tumor cell lines that represent the main types of malignant thyroid carcinomas (B-CPAP, follicular; Cal-62, anaplastic; FTC-133, papillary thyroid carcinoma cells) and in which these pathways are constitutively activated. In general, pharmacological perturbation of PI3/Akt (application of MK-2206) and MEK/ERK1/2 (application of PD0325901 or U0126) signaling led to a cell line and drug-specific decrease in the proliferation and migration potential of thyroid carcinoma cells, although to a varying extent. However, one exception became apparent: in Cal-62 cells inhibition of the MEK/ERK1/2 module increased the migration rate up to 50%. This effect could be prevented by a simultaneous suppression of the PI3/Akt pathway, but also by application of the multiple kinase inhibitor sorafenib, a treatment that did not change the activation state of Akt. Thus, a pharmacological perturbation of canonical signaling pathways in thyroid carcinoma may induce drug-dependent yin-yang effects that are characterized by a simultaneous suppression of one (i.e., proliferation) and the activation of another (i.e., migration) cellular process. The appearance of such phenomena should be taken into account when therapy plans are established.

Topics: Benzamides; Carcinoma; Carcinoma, Papillary; Cell Line, Tumor; Cell Movement; Cell Proliferation; Diphenylamine; Gene Expression Regulation, Neoplastic; Heterocyclic Compounds, 3-Ring; Humans; MAP Kinase Signaling System; Phosphatidylinositol 3-Kinases; Proto-Oncogene Proteins c-akt; Signal Transduction; Thyroid Cancer, Papillary; Thyroid Neoplasms; Yin-Yang

Development of targeted therapies for medullary thyroid cancer (MTC) has focused on inhibition of the rearranged during transfection (RET) proto-oncogene. Akt has been demonstrated to be a downstream target of RET via the key mediator phosphoinositide-3-kinase. MK-2206 is an orally administered allosteric Akt inhibitor that has exhibited minimal toxicity in phase I trials. We explored the antitumor effects of this compound in MTC.. Human MTC-TT cells were treated with MK-2206 (0-20 μM) for 8 days. Assays for cell viability were performed at multiple time points with MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide). The mechanism of action, mechanism of growth inhibition, and production of neuroendocrine tumor markers were assessed with Western blot analysis.. MK-2206 suppressed MTC cell proliferation in a dose-dependent manner (p ≤ 0.001). Levels of Akt phosphorylated at serine 473 declined with increasing doses of MK-2206, indicating successful Akt inhibition. The apoptotic proteins cleaved poly (ADP-ribose) polymerase and cleaved caspase-3 increased in a dose-dependent manner with MK-2206, while the apoptosis inhibitor survivin was markedly reduced. Importantly, the antitumor effects of MK-2206 were independent of RET inhibition, as the levels of RET protein were not blocked.. MK-2206 significantly suppresses MTC proliferation without RET inhibition. Given its high oral bioavailability and low toxicity profile, phase II studies with this drug alone or in combination with RET inhibitors are warranted.

Topics: Apoptosis; Basic Helix-Loop-Helix Transcription Factors; Biomarkers, Tumor; Blotting, Western; Carcinoma, Medullary; Caspase 3; Cell Proliferation; Chromogranin A; Heterocyclic Compounds, 3-Ring; Humans; Neuroendocrine Tumors; Phosphorylation; Poly(ADP-ribose) Polymerases; Proto-Oncogene Mas; Proto-Oncogene Proteins c-akt; Thyroid Neoplasms; Tumor Cells, Cultured

The purpose of the study was to explore optimal combinations of currently actively developed drugs for dually targeting the Ras → Raf → MAPK kinase (MEK) → MAPK/ERK (MAPK) and the phosphatidylinositol 3-kinase/Akt pathways as effective treatments for thyroid cancer.. We tested the combinations of the Akt inhibitors MK2206 or perifosine with the BRAF(V600E) inhibitor PLX4032 or the MEK1/2 inhibitor AZD6244 in thyroid cancer cells harboring both the BRAF(V600E) and PIK3CA mutations.. We found that MK2206 could potently, when used alone, and synergistically, when combined with either PLX4032 or AZD6244, inhibit thyroid cancer cell growth with all the combination index values lower than 1. Perifosine could potently inhibit thyroid cancer cell growth when used alone, but a strong antagonism occurred between this drug and PLX4032 or AZD6244 in the inhibition of thyroid cancer cell growth with all combination index values higher than 1. Combinations of MK2206 with PLX4032 or AZD6244 dramatically enhanced G1 cell cycle arrest induced by each drug alone. However, G2 cell cycle arrest uniquely induced by perifosine alone and G1 cell cycle arrest induced by PLX4032 or AZD6244 were both reversed by combination treatments, providing a mechanism for their antagonism. All these drugs could correspondingly inhibit the MAPK and phosphatidylinositol 3-kinase/Akt signalings, confirming their expected target effects.. We demonstrated, unexpectedly, opposite outcomes of MK2206 and perifosine in their combinational treatments with BRAF(V600E)/MEK inhibitors in thyroid cancer cells. The data may help appropriate selection of these prominent drugs for clinical trials of combination therapies for thyroid cancer.

Topics: Antineoplastic Combined Chemotherapy Protocols; Benzimidazoles; Carcinoma; Cell Proliferation; Down-Regulation; Drug Antagonism; Drug Evaluation, Preclinical; Drug Synergism; Glutamic Acid; Heterocyclic Compounds, 3-Ring; Humans; Indoles; Mutant Proteins; Oncogene Protein v-akt; Phosphorylcholine; Protein Kinase Inhibitors; Proto-Oncogene Proteins B-raf; Sulfonamides; Thyroid Neoplasms; Tumor Cells, Cultured; Valine; Vemurafenib

The phosphoinositide 3-kinase (PI3K)/Akt pathway is widely postulated to be an effective therapeutic target in thyroid cancer.. The aim of the study was to test the therapeutic potential of the novel Akt inhibitor MK2206 for thyroid cancer.. We examined the effects of MK2206 on thyroid cancer cells with respect to the genotypes of the PI3K/Akt pathway.. Proliferation of thyroid cancer cells OCUT1, K1, FTC133, C643, Hth7, and TPC1, which harbored PIK3CA, PTEN, Ras, or RET/PTC mutations that could activate the PI3K/Akt pathway, was potently inhibited by MK2206 with IC(50) values mostly below or around 0.5 μm. In contrast, no potent inhibition by MK2206 was seen in most of the Hth74, KAT18, SW1736, WRO, and TAD2 cells that did not harbor mutations in the PI3K/Akt pathway. The inhibition efficacy was also genetic-selective. Specifically, the average inhibition efficacies were 59.2 ± 11.3 vs. 36.4 ± 8.8% (P = 0.005) at 1 μm MK2206 and 64.4 ± 11.5 vs. 38.5 ± 18.9% (P = 0.02) at 3 μm MK2206 for cells with mutations vs. cells without. The SW1736 cell, lacking mutations in the PI3K/Akt pathway, had minimal response to MK2206, but transfection with exogenous PIK3CA mutants, PIK3CA H1047R and E545K, significantly increased its sensitivity to MK2206. MK2206 also completely overcame the feedback activation of Akt from temsirolimus-induced mammalian target of rapamycin suppression, and the two inhibitors synergistically inhibited thyroid cancer cell growth.. Our study demonstrates a genetic selectivity of MK2206 in inhibiting thyroid cancer cells by targeting the PI3K/Akt pathway, supporting a clinical trial in thyroid cancer.

Topics: Adenocarcinoma, Follicular; Antineoplastic Agents; Antineoplastic Combined Chemotherapy Protocols; Cell Line, Tumor; Cell Proliferation; Down-Regulation; Drug Evaluation, Preclinical; Drug Synergism; Heterocyclic Compounds, 3-Ring; Humans; Phosphatidylinositol 3-Kinases; Phosphorylation; Point Mutation; Protein Kinase Inhibitors; Proto-Oncogene Proteins c-akt; Signal Transduction; Sirolimus; Substrate Specificity; Thyroid Carcinoma, Anaplastic; Thyroid Neoplasms