In vitro cytotoxicity of the novel antimyeloma agents perifosine, bortezomib and lenalidomide against different cell lines.

The novel AKT inhibitor perifosine, a synthetic alkylphospholipid, is currently being investigated in clinical trials for the treatment of different hematological and oncological malignancies. The in vitro cytotoxicity of perifosine, bortezomib and lenalidomide against 6 cell lines derived from hematological malignancies was investigated using trypan blue staining, flow cytometry-based detection of activated caspases, Annexin V assays, immunohistochemistry studies (KI-67 and caspase-3 staining) and the immature-myeloid-information (IMI) technique. Perifosine and bortezomib induced concentration- and time-dependent cytotoxicity in all cell lines tested. Perifosine together with bortezomib largely exerted additive or synergistic effects with combination indices ranging from 1.13 to 0.22 for combined efficacies of 25% to 75% after 24-hour incubation. Lenalidomide-triggered cytotoxicity was low in all cell lines tested with any assay (less than 10% compared to the negative control). Finally, perifosine, but not bortezomib or lenalidomide, significantly increased the number of cells detected in the IMI channel. Perifosine and bortezomib- but not lenalidomide- trigger substantial cytotoxicity by caspase activation and mainly act additively or synergistically. The IMI technique might be a useful tool for studying cytotoxicity of agents like perifosine that interact mainly with the cellular membrane.

In vitro effects of perifosine, bortezomib and lenalidomide against hematopoietic progenitor cells from healthy donors.

The novel AKT inhibitor perifosine possesses myelopoiesis-stimulating effects in rodents. We studied the in vitro effects of the novel agents perifosine, bortezomib and lenalidomide in addition to adriamycin against normal human hematopoietic progenitor cells (HPC) using different clonogenic and non-clonogenic assays. All agents inhibited colony-forming unit (CFU) formation, perifosine inhibiting mainly CFU-granulocyte/macrophage formation and the other agents burst-forming unit-erythroid formation. Perifosine combined with lenalidomide or adriamycin tended to act antagonistically in suppressing CFU formation. Despite their inhibition of CFU formation, perifosine, bortezomib and lenalidomide induced only slight or moderate cytotoxicity in CD34(+) selected HPC, as assessed using different assays such as flow cytometry-based detection of activated caspases and immunohistochemistry studies (e.g., Ki-67 staining). In contrast to its myelopoiesis-stimulating effects in rodents, perifosine--like bortezomib and lenalidomide--suppresses the clonogenic potential of HPC from healthy donors in vitro and thus probably plays no role in preventing neutropenia or in shorting its duration after intensive chemotherapy. However, all these novel agents typically induce only slight or moderate suppression of the clonogenic potential or loss of viability of normal HPC at clinically achievable plasma concentrations, assuming that hematoxicity is manageable and functional HPC can be collected after treatment with these compounds.

Radiotherapeutic treatment options for oligotopic malignant liver lesions.

BACKGROUND: Several radiotherapeutic approaches for patients with oligotopic malignant liver lesions unfit for surgical resection exist. The most advanced competitive techniques are high-dose-rate (HDR) brachytherapy, Cyberknife, volume-modulated-arc therapy (VMAT) and Tomotherapy. We evaluated the optimal technique by a planning study for a single ablative dose with different lesion sizes. METHODS: We compared dose distributions of HDR-brachytherapy with stereotactic ablative radiotherapy using the Cyberknife, VMAT or Tomotherapy. Tumor-control-probabilities (TCP), normal-tissue-complication-probabilities (NTCP) were determined in a theoretical framework applying a single dose of 20 Gy (demanding 95% coverage) for intrahepatic lesions of 1-5 cm in size. We evaluated therapeutic ratios by TCP (mean dose in the lesion) relative to high-dose (conformality) or low-dose liver exposition in dependency on the lesion size for each technique. In addition, we considered treatment times and accuracy (clinical target volume vs planning target volume). RESULTS: HDR-brachtherapy has the highest therapeutic ratios with respect to high-dose as well as low-dose liver exposition even for extended lesions, and the Cyberknife being suited second best. However, for lesions ≥ 3 cm diameter the therapeutic ratios of all ablative techniques are increasingly converging, and better tolerance and shorter treatment times of noninvasive external techniques become more important. On the other hand, mean tumor doses of HDR-brachytherapy of near 60 Gy are unattainable by the other techniques gaining only 22-34 Gy, and the conformality of HDR-brachytherapy is still rather good for lesions ≥ 3 cm diameter. CONCLUSIONS: HDR-brachytherapy is by far the most effective technique to treat intrahepatic lesions by a single fraction, but sparing of the surroundings declines with increasing lesion size and approaches the benchmarks of external beam radiosurgery techniques. External beam radiotherapy has the advantage to use suitable fractionation schedules.