sirolimus and Rhabdomyosarcoma--Alveolar

Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma of childhood. The two most common histologic variants are the embryonal and alveolar subtypes. Although successive collaborative group clinical trials have improved survival rates for many RMS patients, the outcome for those patients with metastatic or recurrent disease remains poor. Recent studies have pointed to a possible mesenchymal stem cell as the progenitor for alveolar RMS. Other studies have implicated several cellular mechanisms and pathways being involved in RMS pathogenesis and survival, such as the cyclin-dependent kinase inhibitors, insulin-like growth factor pathway, and the mammalian target of rapamycin pathway, thus providing potential avenues for targeted therapy. Recent clinical trials have tried to improve risk stratification and prediction of clinical outcome based upon clinical or radiographic response to initial therapy and also to determine the role of high-dose chemotherapy with stem cell rescue in high-risk RMS patients.

Topics: Animals; Antineoplastic Combined Chemotherapy Protocols; Child; Child, Preschool; Clinical Trials as Topic; Combined Modality Therapy; Disease Progression; Female; Humans; Male; Mesenchymal Stem Cells; Mice; Neoplasm Metastasis; Neoplasm Staging; Neoplastic Stem Cells; Prognosis; Protein Kinase Inhibitors; Rhabdomyosarcoma, Alveolar; Rhabdomyosarcoma, Embryonal; Risk Factors; Secondary Prevention; Signal Transduction; Sirolimus; Soft Tissue Neoplasms; Survival Rate; Tomography; TOR Serine-Threonine Kinases

The target of rapamycin, mTOR, acts as a sensor for mitogenic stimuli, such as insulin-like growth factors and cellular nutritional status, regulating cellular growth and division. As many tumors are driven by autocrine or paracrine growth through the type-I insulin-like growth factor receptor, mTOR is potentially an attractive target for molecular-targeted treatment. Further, a rationale for anticipating tumor-selective activity based on transforming events frequently identified in malignant disease is becoming established.

Topics: Animals; Antibiotics, Antineoplastic; Apoptosis; Child; Clinical Trials as Topic; Humans; Insulin-Like Growth Factor I; Neoplasms; Protein Kinases; Receptor, Insulin; Rhabdomyosarcoma, Alveolar; Sirolimus; TOR Serine-Threonine Kinases; Tumor Cells, Cultured

Rapamycin inhibits vascular endothelial growth factor expression. Vascular endothelial growth factor is a tumor-elaborated protein that stimulates neovascularization. This inhibition can cause transient "normalization" of the generally dysfunctional tumor vasculature, resulting in improved tumor perfusion and oxygenation. We hypothesized that this may potentiate the antitumor effects of adjuvant ionizing radiation.. Mice bearing orthotopic Rh30 alveolar rhabdomyosarcomas were treated with rapamycin (5 mg/kg intraperitoneally daily ×5). Tumors were then evaluated for changes in intratumoral oxygenation, perfusion, vessel permeability, and microvessel density. Additional tumor-bearing mice were treated with 5 doses of rapamycin, irradiation (4 Gy), or 5 doses of rapamycin with irradiation administered on the first or sixth day of rapamycin treatment.. Although tumor vessel permeability changed only minimally, microvessel density decreased (3153 ± 932 vs 20,477 ± 3717.9 pixels per high-power field), whereas intratumoral oxygenation increased significantly (0.0385 ± 0.0141 vs 0.0043 ± 0.0023 mm Hg/mm(3)) after 5 doses of rapamycin. Contrast-enhanced ultrasound demonstrated a significantly increased rate of change of signal intensity after 5 days of rapamycin, suggesting improved intratumoral perfusion. Tumor volume 14 days after treatment was smallest in mice treated with the combination of rapamycin given before irradiation.. Combination therapy with rapamycin given before irradiation to normalize the tumor vasculature, thereby improving tumor oxygenation, increased the sensitivity of alveolar rhabdomyosarcoma xenografts to adjuvant irradiation.

Topics: Animals; Antibiotics, Antineoplastic; Combined Modality Therapy; Mice; Mice, SCID; Neoplasm Transplantation; Radiation, Ionizing; Rhabdomyosarcoma, Alveolar; Sirolimus; Transplantation, Heterologous

Alveolar rhabdomyosarcoma (RMS) has a much poorer outcome than embryonal RMS. In this study, we found that IGF-I affected the induction of myogenin and cell cycle progression in alveolar RMS cells, but not in embryonal RMS cells. IGF-I enhanced the induction of myogenin protein in alveolar RMS SJ-Rh30 and KP-RMS-MS cells as it did in myoblast C2C12 cells, but not in embryonal RMS RD or KP-RMS-KH cells. IGF-I induction of myogenin protein was blocked by anti-IGF-IR monoclonal antibody alphaIR-3 and the mTOR-specific inhibitor rapamycin. In Rh30mTOR-rr cells, which stably express a rapamycin-resistant mutant mTOR, rapamycin did not inhibit IGF-I induction of myogenin protein. These data suggest that IGF-I induces myogenin in alveolar RMS cells through the IGF-IR/mTOR pathway. In C2C12 cells, IGF-I induces myogenin protein followed by cell cycle arrest leading to myogenic differentiation. IGF-I promoted G1-S cell cycle progression without any signs of terminal differentiation in alveolar RMS cells. On the other hand, IGF-I promoted neither cell cycle arrest nor G1-S cell cycle progression in embryonal RMS cells. In alveolar RMS SJ-Rh30 cells, 4E-BP1, one of two effectors downstream of mTOR, was continuously hyperphosphorylated by IGF-I, whereas in embryonal RMS RD cells, 4E-BP1 was only transiently hyperphosphorylated. These findings suggest that the different effects of IGF-I on myogenin induction and cell cycle progression in alveolar and embryonal RMS cells are due to a difference of phosphorylation status of 4E-BP1. These different responses to IGF-I help to explain immunohistochemical and clinical behavioral differences between alveolar and embryonal RMS.

Topics: Antibiotics, Antineoplastic; Antibodies, Monoclonal; Cell Cycle; Cell Line, Tumor; Humans; Imidazoles; Insulin-Like Growth Factor I; Muscle Development; Myogenin; Protein Biosynthesis; Protein Kinase Inhibitors; Protein Kinases; Pyridines; Receptor, IGF Type 1; Rhabdomyosarcoma, Alveolar; Rhabdomyosarcoma, Embryonal; Sirolimus; TOR Serine-Threonine Kinases

The protein synthetic machinery is activated by diverse genetic alterations during tumor progression in vivo and represents an attractive target for cancer therapy. We show that rapamycin inhibits the induction of transformed foci in vitro by GLI, a transcription factor that functions in the sonic hedgehog-patched pathway in tumors. In control cells, which were nontransformed epithelioid RK3E cells and derivative c-MYC- or RAS-transformed sister cell lines, rapamycin inhibits mTOR and mTOR-dependent activities but increases global protein synthesis, perhaps by activating a feedback mechanism. In GLI-transformed cells, rapamycin inhibits global protein synthesis and turnover and prevents cellular proliferation. In contrast to its effects on protein synthesis, rapamycin affects bromodeoxyuridine incorporation and cell cycle occupancy of GLI cells and control cells to a similar extent. Rare, variant GLI cells isolated by selection in rapamycin are also drug-resistant for protein metabolism and for cell cycle progression through G1. Our results indicate that sensitivity to rapamycin can be induced by a specific oncogene and that inhibition of global protein metabolism is linked to the rapamycin-sensitive phenotype.

Topics: Animals; Antibiotics, Antineoplastic; Cell Cycle; Cell Transformation, Neoplastic; Cells, Cultured; Clone Cells; Genes, myc; Genes, ras; Immunosuppressive Agents; Mice; Mice, Nude; Neoplasm Transplantation; Oncogene Proteins; Phosphotransferases (Alcohol Group Acceptor); Protein Biosynthesis; Protein Kinases; Rhabdomyosarcoma, Alveolar; Rhabdomyosarcoma, Embryonal; Sirolimus; TOR Serine-Threonine Kinases; Trans-Activators; Transcription Factors; Transfection; Transplantation, Heterologous; Zinc Finger Protein GLI1; Zinc Fingers