azd-6244 and Rhabdomyosarcoma

To test the role of STAT3 in human rhabdomyosarcoma cells, genetic approaches were used to either knockdown the expression of STAT3 and GP130, an upstream activator of STAT3 using short hairpin RNA (shRNA) or express persistently active STAT3 protein. Knockdown expression of GP130 or STAT3 sensitized cells to anti-cancer drugs doxorubicin, cisplatin, and MEK inhibitor AZD6244. On the other hand, expression of the constitutively active STAT3 protein reduced the sensitivity of rhabdomyosarcoma cells to those drugs. In addition, we tested a small molecule STAT3 inhibitor LY5 and a GP130 inhibitor bazedoxifene in rhabdomyosarcoma cells. Our data demonstrated that the combination of LY5 or bazedoxifene with doxorubicin, cisplatin, and AZD6244 showed stronger inhibitory effects than single agent alone. In summary, our results demonstrated that GP130/STAT3 signaling contributes to the resistance of these drugs in rhabdomyosarcoma cells. They also suggested a potentially novel cancer therapeutic strategy using the combination of inhibitors of GP130/STAT3 signaling with doxorubicin, cisplatin, or AZD6244 for rhabdomyosarcoma treatments.

Topics: Antineoplastic Agents; Apoptosis; Benzimidazoles; Cell Line, Tumor; Cell Survival; Cisplatin; Cytokine Receptor gp130; Doxorubicin; Humans; MAP Kinase Signaling System; Phosphorylation; Protein Kinase Inhibitors; Rhabdomyosarcoma; Signal Transduction; STAT3 Transcription Factor

To provide rationale for using phosphoinositide 3-kinase (PI3K) and/or mitogen-activated protein kinase (MAPK) pathway inhibitors to treat rhabdomyosarcomas, a major cause of pediatric and adolescent cancer deaths.. The prevalence of PI3K/MAPK pathway activation in rhabdomyosarcoma clinical samples was assessed using immunohistochemistry. Compensatory signaling and cross-talk between PI3K/MAPK pathways was determined in rhabdomyosarcoma cell lines following p110α short hairpin RNA-mediated depletion. Pharmacologic inhibition of reprogrammed signaling in stable p110α knockdown lines was used to determine the target-inhibition profile inducing maximal growth inhibition. The in vitro and in vivo efficacy of inhibitors of TORC1/2 (AZD8055), MEK (AZD6244), and P13K/mTOR (NVP-BEZ235) was evaluated alone and in pairwise combinations.. PI3K pathway activation was seen in 82.5% rhabdomyosarcomas with coactivated MAPK in 36% and 46% of alveolar and embryonal subtypes, respectively. p110α knockdown in cell lines over the short and long term was associated with compensatory expression of other p110 isoforms, activation of the MAPK pathway, and cross-talk to reactivate the PI3K pathway. Combinations of PI3K pathway and MAP-ERK kinase (MEK) inhibitors synergistically inhibited cell growth in vitro. Treatment of RD cells with AZD8055 plus AZD6244 blocked reciprocal pathway activation, as evidenced by reduced AKT/ERK/S6 phosphorylation. In vivo, the synergistic effect on growth and changes in pharmacodynamic biomarkers was recapitulated using the AZD8055/AZD6244 combination but not NVP-BEZ235/AZD6244. Pharmacokinetic analysis provided evidence of drug-drug interaction with both combinations.. Dual PI3K/MAPK pathway activation and compensatory signaling in both rhabdomyosarcoma subtypes predict a lack of clinical efficacy for single agents targeting either pathway, supporting a therapeutic strategy combining a TORC1/2 with a MEK inhibitor.

Topics: Animals; Antineoplastic Agents; Benzimidazoles; Cell Line, Tumor; Class I Phosphatidylinositol 3-Kinases; Disease Models, Animal; Drug Synergism; Enzyme Activation; Female; Gene Knockdown Techniques; Humans; Mitogen-Activated Protein Kinases; Morpholines; Phosphatidylinositol 3-Kinases; Proto-Oncogene Proteins c-akt; Proto-Oncogene Proteins p21(ras); Rhabdomyosarcoma; Signal Transduction; TOR Serine-Threonine Kinases; Xenograft Model Antitumor Assays