Characterization of Rare, Dormant, and Therapy-Resistant Cells in Acute Lymphoblastic Leukemia.

Tumor relapse is associated with dismal prognosis, but responsible biological principles remain incompletely understood. To isolate and characterize relapse-inducing cells, we used genetic engineering and proliferation-sensitive dyes in patient-derived xenografts of acute lymphoblastic leukemia (ALL). We identified a rare subpopulation that resembled relapse-inducing cells with combined properties of long-term dormancy, treatment resistance, and stemness. Single-cell and bulk expression profiling revealed their similarity to primary ALL cells isolated from pediatric and adult patients at minimal residual disease (MRD). Therapeutically adverse characteristics were reversible, as resistant, dormant cells became sensitive to treatment and started proliferating when dissociated from the in vivo environment. Our data suggest that ALL patients might profit from therapeutic strategies that release MRD cells from the niche.

Leukemia-initiating cells of patient-derived acute lymphoblastic leukemia xenografts are sensitive toward TRAIL.

Cancer stem cells represent the most important target cells for antitumor therapy. TRAIL (TNF-related apoptosis-inducing ligand) is a potential anticancer agent that induces apoptosis in a wide variety of tumor cells, but its ability to target cancer stem cells is currently unknown. Here we investigated whether TRAIL targets leukemia-initiating cells. Limiting dilution transplantation assays were performed on xenografts from pediatric patients with precursor B-cell acute lymphoblastic leukemia (pre-B ALL) in NSG mice. In vitro treatment of xenograft cells with TRAIL significantly reduced and delayed their engraftment and procrastinated animal death from leukemia. Systemic TRAIL treatment of mice injected with patient-derived pre-B ALL xenograft cells abrogated leukemia in 3 of 5 mice in 1 sample. In conclusion, our data suggest that TRAIL targets leukemia-initiating cells derived from pre-B ALL xenografts in vitro and in vivo, and hence constitutes an attractive candidate drug for treatment of ALL.

In vivo imaging enables high resolution preclinical trials on patients' leukemia cells growing in mice.

BACKGROUND: Xenograft mouse models represent helpful tools for preclinical studies on human tumors. For modeling the complexity of the human disease, primary tumor cells are by far superior to established cell lines. As qualified exemplary model, patients' acute lymphoblastic leukemia cells reliably engraft in mice inducing orthotopic disseminated leukemia closely resembling the disease in men. Unfortunately, disease monitoring of acute lymphoblastic leukemia in mice is hampered by lack of a suitable readout parameter. DESIGN AND METHODS: Patients' acute lymphoblastic leukemia cells were lentivirally transduced to express the membrane-bound form of Gaussia luciferase. In vivo imaging was established in individual patients' leukemias and extensively validated. RESULTS: Bioluminescence in vivo imaging enabled reliable and continuous follow-up of individual mice. Light emission strictly correlated to post mortem quantification of leukemic burden and revealed a logarithmic, time and cell number dependent growth pattern. Imaging conveniently quantified frequencies of leukemia initiating cells in limiting dilution transplantation assays. Upon detecting a single leukemia cell within more than 10,000 bone marrow cells, imaging enabled monitoring minimal residual disease, time to tumor re-growth and relapse. Imaging quantified therapy effects precisely and with low variances, discriminating treatment failure from partial and complete responses. CONCLUSIONS: For the first time, we characterized in detail how in vivo imaging reforms preclinical studies on patient-derived tumors upon increasing monitoring resolution. In the future, in vivo imaging will enable performing precise preclinical studies on a broad range of highly demanding clinical challenges, such as treatment failure, resistance in leukemia initiating cells, minimal residual disease and relapse.

A proinflammatory genetic profile increases the risk for chronic atrophic gastritis and gastric carcinoma.

BACKGROUND & AIMS: Pro-inflammatory polymorphisms within the genes interleukin (IL)-1B and IL-1RN are associated with risk for gastric carcinoma (GC) in Helicobacter pylori-infected individuals. We aimed to determine the association between variation of the tumor necrosis factor (TNF)-alpha gene and the risk for chronic atrophic gastritis (CAG) and GC. We also investigated the extent to which the combined effect of proinflammatory genetic polymorphisms (IL-1B, IL-1RN, and TNF-alpha), and the combined effect of TNF-alpha and bacterial genotypes each influence such a risk. METHODS: In a case-control study including 306 controls, 221 individuals with chronic gastritis, and 287 GC patients, the TNF-alpha-308 and IL-1B-511 bi-allelic polymorphisms, the IL-1RN variable number of tandem repeats (VNTR), and the H. pylori genes vacA (s and m regions) and cagA were genotyped. RESULTS: We found that carriers of the TNF-alpha-308*A allele are at increased risk for GC development with an odds ratio (OR) of 1.9 (95% confidence interval [CI], 1.3-2.7). For both CAG and GC, the odds of developing disease increased with the number of high-risk genotypes. Individuals carrying high-risk genotypes at the 3 loci are at increased risk for CAG and GC with an OR of 5.8 (95% CI, 1.1-31.0) and 9.7 (95% CI, 2.6-36.0), respectively. The risk for GC was not affected significantly by the combination of bacterial and TNF-alpha-308 genotypes. CONCLUSIONS: These findings show that a proinflammatory polymorphism in the TNF-alpha gene is associated with increased risk for GC, and that it is possible to define a specific genetic profile associated with highest risk for CAG and GC.