Cotargeting MAPK and PI3K Signaling with Concurrent Radiotherapy as a Strategy for the Treatment of Pancreatic Cancer

Abstract

There is an urgent need for the development of novel therapies to treat pancreatic cancer, which is among the most lethal of all cancers. KRAS activating mutations, which are found in >90% of pancreatic adenocarcinomas, drive tumor dependency on the Ras/MAPK and Akt signaling pathways. Radiation is currently being explored as a component of the standard treatment regimen for pancreatic cancer. This study’s purpose was to test the hypothesis that MEK inhibitors will offer clear therapeutic benefit when integrated into radiotherapy treatment regimens for treatment of this disease. We explored the activation of the MAPK and Akt pathways in response to radiation in multiple pancreatic tumor cell lines. Small molecule inhibitors of MEK (PD0325901) and Akt (API-2) were subsequently evaluated for their radiosensitizing potential alone and in combination. In vivo efficacy was tested in subcutaneous MIA-PaCa2 xenografts. Phosphorylated levels of ERK-1/2 and Akt were found to increase in response to radiation treatment in our pancreatic tumor cell line panel. MEK inhibitor-induced radiosensitization was observed in vitro and in vivo. The further addition of an Akt inhibitor to the MEK inhibitor/radiation regimen resulted in enhanced therapeutic gain as determined by increased radiosensitization and tumor cell death. In conclusion, MEK inhibition results in growth arrest, apoptosis, and radiosensitization of multiple preclinical pancreatic tumor models, and the effects can be enhanced by combination with an Akt inhibitor. These results provide rationale for further testing of a treatment regimen in pancreatic cancer that combines MEK inhibition with radiation, optimally in conjunction with Akt inhibition.

Caveolae-Mediated Endocytosis Is Critical for Albumin Cellular Uptake and Response to Albumin-Bound Chemotherapy

“…Immunoblotting was performed as described before (28). Briefly, cell lysates were prepared in RIPA lysis buffer (1% NP-40, 150mM NaCl, 50mM Tris-HCL pH 7.4, 0.25% Na-deoxycholate, 1 mM EDTA) supplemented with 1× protease inhibitor (Complete, Roche Applied Science) and phosphatase inhibitors (PhosSTOP, Roche Applied Science).…”

“…(28) Briefly, cells were plated in 6 well dishes, and treated with or without 10ng/ml nab-paclitaxel. After 48 hours of treatment, the percentage of apoptotic cells was determined using ApoDETECT™ Annexin V-FITC kit (Invitrogen) according to the manufacturer’s protocol.…”

“…(28) Six to eight week-old male athymic nude mice (Taconic Farms Inc., NY) were caged in groups of five or less, and fed a diet of animal chow and water ad libitum. MIAPaCa-2 and H23 stable cell lines bearing control or Cav-1 shRNA (2–4 × 10 6 cells each) were injected subcutaneously into the flanks of each mouse.…”

Discovery of Bifunctional Oncogenic Target Inhibitors against Allosteric Mitogen-Activated Protein Kinase (MEK1) and Phosphatidylinositol 3-Kinase (PI3K)

“…Additionally, many in vitro and in vivo studies have shown synergistic outcomes in tumor cell death by simultaneous inhibition of these two pathways. 8–10 As the Ras/MEK/ERK and PI3K/Akt/mTor pathways are regulated by different mechanisms, simultaneous co-targeting of these pathways is an attractive anticancer strategy. Current approaches toward multikinase drug targeting involve drug administration as either (a) two or more therapeutics (drug cocktail) or (b) a polyfunctional multitargeting single agent therapeutic.…”

β-elemene enhances both radiosensitivity and chemosensitivity of glioblastoma cells through the inhibition of the ATM signaling pathway

“…In addition, ~40% of patients with GBM have an amplified EGFR gene which results in constitutive activation of AKT and ERK (10). AKT and ERK signaling pathways play vital roles in regulating many fundamental cellular processes and they are associated with resistance to treatment in GBM cells (11,12). β-elemene, a Chinese antitumor medicine extracted from the plant Curcuma wenyujin, has been isolated as a monomeric drug and has a broad-spectrum antitumor effect in various tumor cells, such as lung (13), breast carcinoma (14), leukemia (15), ovarian cancer (16) and GBM (17).…”