In vitro and In vivo Radiosensitization with AZD6244 (ARRY-142886), an Inhibitor of Mitogen-activated Protein Kinase/Extracellular Signal-regulated Kinase 1/2 Kinase

Abstract

Purpose: The mitogen-activated protein (MAP) kinase pathway is important for cell proliferation, survival, and differentiation, and is frequently up-regulated in cancers. The MAP kinase pathway is also activated after exposure to ionizing radiation. We investigated the effects of AZD6244 (ARRY-142886), an inhibitor of MAP kinase/extracellular signal-regulated kinase 1/2, on radiation response. Experimental Design: The effects of AZD6244 on the in vitro radiosensitivity of human cancer cell lines (A549, MiaPaCa2, and DU145) were evaluated using clonogenic assays. DNA damage repair was evaluated using gH2AX, and mitotic catastrophe was measured using nuclear fragmentation. Cell cycle effects were measured with flow cytometry. Growth delay was used to evaluate the effects of AZD6244 on in vivo tumor radiosensitivity. Results: Exposure of each cell line to AZD6244 before irradiation resulted in an increase in radiosensitivity with dose enhancement factors at a surviving fraction of 0.1, ranging from 1.16 to 2.0. No effects of AZD6244 on radiation-induced apoptosis or persistence of gH2AX foci after irradiation were detected. Cells treated with AZD6244 had an increased mitotic index and decreased Chk1phosphorylation at 1and 2 hours after irradiation. Mitotic catastrophe was increased in cells receiving AZD6244 and irradiation compared with the single treatments. In vivo studies revealed that AZD6244 administration to mice bearing A549 tumor xenografts resulted in a greater than additive increase in radiation-induced tumor growth delay (dose enhancement factor of 3.38). Conclusions: These results indicate that AZD6244 can enhance tumor cell radiosensitivity in vitro and in vivo and suggest that this effect involves an increase in mitotic catastrophe.

The Mitogen-Activated Protein/Extracellular Signal-Regulated Kinase Kinase 1/2 Inhibitor AZD6244 (ARRY-142886) Enhances the Radiation Responsiveness of Lung and Colorectal Tumor Xenografts

“…Markers for DNA damage (phosphorylated H2AX) and apoptosis (cleaved caspase-3) were assessed by immunohistochemistry after 5 days of treatment, but did not reveal any significant difference between the combination and other groups (data not shown). This is consistent with other recent data, which also suggested that the interaction between AZD6244 and radiotherapy was independent of the effects on DNA double-strand break repair (from examining phosphorylated H2AX) or apoptosis (quantified with an Annexin V binding assay), but may correlate with an increase in mitotic catastrophe (45). However, unlike the Ras mutant cell lines in the study of Chung et al (45), AZD6244 alone or in combination with radiotherapy had no effect on the cell cycle profile of Calu-6 cells (data not shown).…”

“…5B). Chung et al (45) also observed an enhanced radiotherapeutic response in vivo when a single dose of AZD6244 (50 mg/kg) was administered 4 hours before a single dose of radiotherapy (3 Gy).…”

“…Hamed et al (44) showed that 48-hour pretreatment of mammary tumor cells with the MEK inhibitor PD184352 and anticancer staurosporine analogue UCN-01 followed by 24-hour drug removal before irradiation enhanced cell death compared with either drug or IR alone. Furthermore, very recent studies showed that AZD6244 given 16 hours before radiation treatment enhanced the radiosensitivity of lung (A549), pancreatic (MiaPaCa), and prostate (DU145) cells in vitro (45). The mechanistic basis for this sensitization does not seem to involve enhanced apoptosis, with no change in PARP cleavage observed between cells treated with IR alone or in combination with AZD6244.…”

Cytokinetically quiescent (G0/G1) human multiple myeloma cells are susceptible to simultaneous inhibition of Chk1 and MEK1/2

“…42 Moreover, recent findings suggest a functional role for MEK1/2/ ERK1/2 in cell-cycle checkpoints. 43,44 However, the MEK1/2/ ERK1/2 pathway also mediates multiple survival functions, including down-regulation of proapoptotic proteins such as Bad and Bim. 45 The latter protein, implicated in potentiation of Chk1 inhibitor lethality by inhibitors of the Ras/MEK1/2/ERK1/2 pathway in the bulk population of MM cells, 20 also plays a functional role in the lethality of these regimens toward quiescent (G 0 /G 1 ) MM cells.…”

Mitogen-activated protein kinase pathway inhibitors: inhibitors for diseases?

“…In an LPS-induced acute lung injury mouse model, pretreatment of mice with U0126 significantly reduced lung neutrophilia and diminished levels of TNF-alpha and chemotactic MIP-2 and killer cells in bronchoalveolar fluid, suggesting that the pharmacologic inhibition of ERK provides a promising new therapeutic strategy for lung inflammatory diseases [48]. Currently, some ERK pathway inhibitors, such as PD184352, PD0325901 and AZD6244, are being evaluated in clinical trials [49]. Other research results indicate that the ERK pathway inhibitor BAY43-9006 displays a very promising future in the treatment of cancer [50].…”