Using the individualized xenograft mouse model of AML has resulted in seminal insights, e.g., in stem cell biology ; nevertheless, the model has not yet been used extensively for other purposes. First, most Sorafenib Raf inhibitor studies were performed on mice injected with primary patient cells, while Erlotinib EGFR/HER2 inhibitor retransplantation of engrafted AML cells was restricted to studies analyzing stem cell features and self-renewing capacity. Nevertheless, serial retransplantation is highly attractive as it provides a continuous supply of patient-derived xenograft AML cells for repetitive functional and therapeutic studies both in vitro and in vivo, but this approach has not yet been systematically explored. Second, genetic engineering was never reported in established PDX AML cells. Molecular studies were mainly restricted to AML cell lines, which were genetically altered both for in vitro and in vivo studies, and both for knockdown strategies and transgene overexpression, including in vivo imaging. Nevertheless, PDX AML cells represent a highly interesting tool for molecular studies, e.g., on signaling proteins, due to their close relationship to the patient sample, in contrast to established AML cell lines. Thirdly, monitoring the growth characteristics of PDX cells in vivo is an important readout for preclinical studies, yet this remains challenging as PDX cells are detected in mouse peripheral blood only at late disease stages using flow cytometry or polymerase chain reaction, and repetitive bone marrow aspirations are performed infrequently for animal welfare. Analysis of murine inner organs like spleen, liver, and kidney can only be performed post mortem, which constitutes a major disadvantage in preclinical treatment trials. Serial passaging and genetic engineering have already been established in studies using primary tumor cells from patients with acute lymphoblastic leukemia by others and us and have proven to be valuable tools to facilitate preclinical in vivo studies. The aim of the present work was to develop an improved preclinical mouse model of AML, broadening and increasing the use and quality of studies performed in the model, by: performing serial retransplantation of primary AML cells to repetitively provide PDX cells for in vitro and in vivo studies; introducing genetic engineering of PDX cells to express transgenes using lentiviral transduction; introducing repetitive and sensitive disease monitoring in vivo by bioluminescence imaging and; establishing a stringent set of quality controls to monitor the effect of retransplantation and transgene expression on molecular, phenotypic and functional sample characteristics. Due to these advances, our model system will facilitate future studies on AML biology and novel treatment approaches in vivo. Taken together, lentiviral transduction was feasible in 5/6 PDX samples; both lentiviral constructs allowed successful transduction indicating a more general applicability of lentiviral constructs. Cell enrichment allowed generation of t-PDX cells without markedly altering sample characteristics. Successful genetic engineering in PDX AML cells now opens a broad variety of possible molecular studies. A codon-optimized form of firefly luciferase was used which enables intense light emission for sensitive monitoring. BLI is frequently and successfully used in tumor cell lines to monitor growth or treatment response in vivo or to monitor engraftment of human hematopoietic stem cells in mice. We and others have recently established BLI to monitor PDX ALL cells growing in mice, while BLI could not be performed in PDX AML cells so far due to the lack of genetic engineering. 1×105 t-PDX cells of AML-372 were injected into mice and repetitively monitored using BLI.