Tipifarnib enhances eradication of acute myeloid leukemia by altering CXCL12/CXCR4 signaling in AML and by modifying the bone marrow microenvironment

The prognosis of acute myeloid leukemia (AML) remains poor in part due to the leukemic bone marrow microenvironment. Our lab has found that CXCL12, a chemokine abundant within the leukemic bone marrow microenvironment, induces apoptosis of AML cells expressing CXCR4, the receptor for CXCL12. However, this CXCL12/CXCR4-induced apoptosis is inhibited by differentiating osteoblasts, which protect AML cells from apoptosis in the bone marrow. Tipifarnib is a farnesyltransferase inhibitor shown to increase progression-free survival in AML patients that express high levels of CXCL12. Here, we report that tipifarnib inhibits the CXCL12/CXCR4-directed migration of AML cells via an ERK independent pathway. Furthermore, tipifarnib enhances CXCL12/CXCR4-mediated AML cell apoptosis via a mechanism that alters expression of apoptosis-regulating proteins. In addition, tipifarnib disrupts AML protection by osteoblasts, increasing AML cell apoptosis. Tipifarnib inhibits the osteoblast-mediated protection of AML cells via disrupting COL1A1 and TNAP, proteins essential for extracellular matrix production. In conclusion, tipifarnib alters the bone marrow microenvironment which is predicted to enhance eradication of AML via inhibiting CXCL12/CXCR4 directed cellular migration of AML cells, reducing the protective effects of differentiating osteoblasts by disrupting matrix protection proteins, and increasing CXCL12/CXCR4-mediated apoptosis.

Building the vertebrate codex using the gene breaking protein trap library

One key bottleneck in understanding the human genome is the relative under-characterization of 90% of protein coding regions. We report a collection of 1200 transgenic zebrafish strains made with the gene-break transposon (GBT) protein trap to simultaneously report and reversibly knockdown the tagged genes. Protein trap-associated mRFP expression shows previously undocumented expression of 35% and 90% of cloned genes at 2 and 4 days post-fertilization, respectively. Further, investigated alleles regularly show 99% gene-specific mRNA knockdown. Homozygous GBT animals in ryr1b, fras1, tnnt2a, edar and hmcn1 phenocopied established mutants. 204 cloned lines trapped diverse proteins, including 64 orthologs of human disease-associated genes with 40 as potential new disease models. Severely reduced skeletal muscle Ca²⁺ transients in GBT ryr1b homozygous animals validated the ability to explore molecular mechanisms of genetic diseases. This GBT system facilitates novel functional genome annotation towards understanding cellular and molecular underpinnings of vertebrate biology and human disease.