Zebrafish screen identifies novel compound with selective toxicity against leukemia.

To detect targeted antileukemia agents we have designed a novel, high-content in vivo screen using genetically engineered, T-cell reporting zebrafish. We exploited the developmental similarities between normal and malignant T lymphoblasts to screen a small molecule library for activity against immature T cells with a simple visual readout in zebrafish larvae. After screening 26 400 molecules, we identified Lenaldekar (LDK), a compound that eliminates immature T cells in developing zebrafish without affecting the cell cycle in other cell types. LDK is well tolerated in vertebrates and induces long-term remission in adult zebrafish with cMYC-induced T-cell acute lymphoblastic leukemia (T-ALL). LDK causes dephosphorylation of members of the PI3 kinase/AKT/mTOR pathway and delays sensitive cells in late mitosis. Among human cancers, LDK selectively affects survival of hematopoietic malignancy lines and primary leukemias, including therapy-refractory B-ALL and chronic myelogenous leukemia samples, and inhibits growth of human T-ALL xenografts. This work demonstrates the utility of our method using zebrafish for antineoplastic candidate drug identification and suggests a new approach for targeted leukemia therapy. Although our efforts focused on leukemia therapy, this screening approach has broad implications as it can be translated to other cancer types involving malignant degeneration of developmentally arrested cells.

Discovery of biologically active oncologic and immunologic small molecule therapies using zebrafish: overview and example of modulation of T cell activation.

Zebrafish models continue to gain popularity as in vivo models for drug discovery. Described in this overview are advantages and challenges of zebrafish drug screening, as well as a novel in vivo screen for immunomodulatory compounds using transgenic, T cell reporting zebrafish larvae designed for discovery of compounds targeting T cell leukemia. This assay system allows rapid screening of large numbers of compounds while avoiding the pitfalls of assays based on cell cultures, which lack biologic context and are afflicted by genomic instability. The rationale for this approach is based on similarities of immature normal T cells and developmentally arrested, malignant lymphoblasts in mammalian species. The screening algorithm has been used to identify a nontoxic compound with activity in both acute leukemia models and models of multiple sclerosis, demonstrating the utility of this screening procedure.