Suppression of leukemia development caused by PTEN loss.

Multiple genetic or molecular alterations are known to be associated with cancer stem cell formation and cancer development. Targeting such alterations, therefore, may lead to cancer prevention. By crossing our previously established phosphatase and tensin homolog (Pten)-null acute T-lymphoblastic leukemia (T-ALL) model onto the recombination-activating gene 1(-/-) background, we show that the lack of variable, diversity and joining [V(D)J] recombination completely abolishes the Tcrα/δ-c-myc translocation and T-ALL development, regardless of ß-catenin activation. We identify mammalian target of rapamycin (mTOR) as a regulator of ß-selection. Rapamycin, an mTOR-specific inhibitor, alters nutrient sensing and blocks T-cell differentiation from CD4(-)CD8(-) to CD4(+)CD8(+), the stage where the Tcrα/δ-c-myc translocation occurs. Long-term rapamycin treatment of preleukemic Pten-null mice prevents Tcrα/δ-c-myc translocation and leukemia stem cell (LSC) formation, and it halts T-ALL development. However, rapamycin alone fails to inhibit mTOR signaling in the c-Kit(mid)CD3(+)Lin(-) population enriched for LSCs and eliminate these cells. Our results support the idea that preventing LSC formation and selectively targeting LSCs are promising approaches for antileukemia therapies.

Ethics Roundtable: How Much is Too Much?

How should the medical team approach care for a very preterm infant with a significant painful and life-limiting condition when the parents wish to pursue all life-sustaining therapies? Here, we discuss a case of an infant born at 28 weeks' gestation with a diagnosis of Carmi syndrome (junctional epidermolysis bullosa and pyloric atresia). While the medical team felt that a do-not-resuscitate order and redirection to comfort care were appropriate, the family held on to hope for recovery and wished to continue with full intensive care measures.

Correlations between the percentage of tumor cells showing an anaplastic lymphoma kinase (ALK) gene rearrangement, ALK signal copy number, and response to crizotinib therapy in ALK fluorescence in situ hybridization-positive nonsmall cell lung cancer.

BACKGROUND: Fluorescence in situ hybridization (FISH), using break-apart red (3') and green (5') ALK (anaplastic lymphoma kinase) probes, consistently shows rearrangements in <100% of tumor cells in ALK-positive (ALK+) nonsmall cell lung cancer (NSCLC). Increased copy numbers of fused and rearranged signals also occur. Here, correlations are explored between the percentage of ALK+ cells and signal copy number and their association with response to ALK inhibition. METHODS: Ninety ALK+ NSCLC cases were evaluated. The percentage of positive cells, pattern of positivity (split, single red, or both), and copy number of fused, isolated red and green signals were recorded. Thirty patients had received crizotinib. RESULTS: Increased isolated red signal copy number (contributing to both single red and split patterns of positivity) correlated with a higher percentage of ALK+ cells (r = 0.743, P < .0001). Mean fused copy number was negatively associated with isolated red signal copy number (r = -0.409, P < .0001). Neither percentage of positive cells (r = 0.192, P = .3), nor copy number of isolated red signal (r = 0.274, P = .195) correlated with maximal tumor shrinkage with crizotinib. CONCLUSIONS: The strong association between increased copy number of key ALK signals and percentage of positive cells suggests that the <100% rate of cellular positivity in ALK+ tumors is due to technical factors, not biological factors. In ALK+ tumors, neither the percentage of positive cells nor signal copy number appear to be informative variables for predicting benefit from ALK inhibition. The inverse relationship between fused and isolated red copy number suggests ALK+ may be a distinct "near-diploid" subtype of NSCLC that develops before significant chromosomal aneusomy occurs.

Identifying and targeting ROS1 gene fusions in non-small cell lung cancer.

PURPOSE: Oncogenic gene fusions involving the 3' region of ROS1 kinase have been identified in various human cancers. In this study, we sought to characterize ROS1 fusion genes in non-small cell lung cancer (NSCLC) and establish the fusion proteins as drug targets. EXPERIMENTAL DESIGN: An NSCLC tissue microarray (TMA) panel containing 447 samples was screened for ROS1 rearrangement by FISH. This assay was also used to screen patients with NSCLC. In positive samples, the identity of the fusion partner was determined through inverse PCR and reverse transcriptase PCR. In addition, the clinical efficacy of ROS1 inhibition was assessed by treating a ROS1-positive patient with crizotinib. The HCC78 cell line, which expresses the SLC34A2-ROS1 fusion, was treated with kinase inhibitors that have activity against ROS1. The effects of ROS1 inhibition on proliferation, cell-cycle progression, and cell signaling pathways were analyzed by MTS assay, flow cytometry, and Western blotting. RESULTS: In the TMA panel, 5 of 428 (1.2%) evaluable samples were found to be positive for ROS1 rearrangement. In addition, 1 of 48 patients tested positive for rearrangement, and this patient showed tumor shrinkage upon treatment with crizotinib. The patient and one TMA sample displayed expression of the recently identified SDC4-ROS1 fusion, whereas two TMA samples expressed the CD74-ROS1 fusion and two others expressed the SLC34A2-ROS1 fusion. In HCC78 cells, treatment with ROS1 inhibitors was antiproliferative and downregulated signaling pathways that are critical for growth and survival. CONCLUSIONS: ROS1 inhibition may be an effective treatment strategy for the subset of patients with NSCLC whose tumors express ROS1 fusion genes.

Feasibility and relevance of examining lymphoblastoid cell lines to study role of microRNAs in autism.

To assess the feasibility and relevance of using lymphoblastoid cell lines to study the role of noncoding RNAs in the etiology of autism, we evaluated global expression profiling of 470 mature human microRNAs from six subjects with autism compared with six matched controls. Differential expression (either higher or lower) for 9 of the 470 microRNAs was observed in our autism samples compared with controls. Potential target genes for these microRNAs were identified using computer tools, which included several autism susceptibility genes. Our preliminary results indicate microRNAs should be considered and evaluated in the etiology of autism. In addition, analysis of this class of noncoding RNAs in lymphoblastoid cells has the potential to reveal at least a subset of brain-related microRNAs implicated in autism. Subsequently, this model system should allow for detection of complex subtle changes in susceptibility genes/pathways contributing to autism.

Energy expenditure and physical activity in Prader-Willi syndrome: comparison with obese subjects.

Prader-Willi syndrome (PWS) is a complex neurodevelopmental disorder characterized by hypotonia, suck and feeding difficulties, hypogonadism, small hands and feet, developmental delay, hyperphagia and early childhood obesity and a particular facial appearance. The obesity associated with PWS is the result of a chronic imbalance between energy intake and energy expenditure (EE) due to hyperphagia, decreased physical activity, reduced metabolic rate and an inability to vomit. EE is affected by body composition as well as exercise. Individuals with PWS have a lower lean body mass (LBM) compared with controls which may contribute to reduced basal level EE. To determine the relationship among body composition, activity levels and metabolic rates, dual energy X-ray absorptiometry (DEXA) and a whole-room respiration chamber were used to measure body composition, total EE (TEE), resting EE (REE), physical activity, and mechanical work (MW) during an 8 hr monitoring period. The chamber consisted of a live-in whole-room indirect calorimeter equipped with a force platform floor to allow simultaneous measurement of EE, physical activity, and work efficiency during spontaneous activities and standardized exercise. Participants with PWS (27 with 15q11-q13 deletion and 21 with maternal disomy 15 with an average age of 23 years) had significantly decreased TEE by 20% and reduced LBM compared to 24 obese subjects. Similarly, REE was significantly reduced by 16% in the individuals with PWS relative to the comparison subjects. Total MW performed during the 8 hr monitoring period was significantly reduced by 35% in the PWS group. The energy cost of physical activity is related to the duration, intensity and type of activity and the metabolic efficiency of the individual. After adjusting group differences in LBM by analysis of variance, TEE and REE were no longer different between the two groups. Our data indicate that there is a significant reduction of EE in individuals with PWS resulting from reduced activity but also from lower energy utilization due to reduced LBM which consists primarily of muscle.

X-chromosome inactivation patterns in females with Prader-Willi syndrome.

Prader-Willi syndrome (PWS) is a complex neurodevelopmental disorder caused by loss of paternally expressed genes from the 15q11-q13 region generally due to a paternally-derived deletion of the 15q11-q13 region or maternal disomy 15 (UPD). Maternal disomy 15 is usually caused by maternal meiosis I non-disjunction associated with advanced maternal age and after fertilization with a normal sperm leading to trisomy 15, a lethal condition unless trisomy rescue occurs with loss of the paternal chromosome 15. To further characterize the pathogenesis of maternal disomy 15 process in PWS, the status of X-chromosome inactivation was calculated to determine whether non-random skewing of X-inactivation is present indicating a small pool of early embryonic cells. We studied X-chromosome inactivation in 25 females with PWS-UPD, 35 with PWS-deletion, and 50 controls (with similar means, medians, and age ranges) using the polymorphic androgen receptor (AR) gene assay. A significant positive correlation (r = 0.5, P = 0.01) was seen between X-chromosome inactivation and age for only the UPD group. Furthermore, a significantly increased level (P = 0.02) of extreme X-inactivation skewness (>90%) was detected in our PWS-UPD group (24%) compared to controls (4%). This observation could indicate that trisomy 15 occurred at conceptus with trisomy rescue in early pregnancy leading to extreme skewness in several PWS-UPD subjects. Extreme X-inactivation skewness may also lead to additional risks for X-linked recessive disorders in PWS females with UPD and extreme X-chromosome skewness.

Body composition and fatness patterns in Prader-Willi syndrome: comparison with simple obesity.

OBJECTIVE: To characterize the body composition of Prader-Willi syndrome (PWS) subjects and compare with simple obesity. RESEARCH METHODS AND PROCEDURES: Seventy-two individuals (27 PWS deletion, 21 PWS uniparental disomy, and 24 obese controls) 10 to 49 years old were studied with the use of DXA. Body composition measures were obtained, and regional fat and lean mass patterns were characterized. Significant differences were assessed with Student's t test and ANOVA adjusting for age, gender, and BMI. RESULTS: Significant differences between the PWS and obese groups were found for lean measures of the arms, legs, and trunk. Total lean mass was significantly lower in PWS than in obese subjects for arms, trunk, and especially legs. Furthermore, two body regions (legs and trunk) showed significant differences for fat and lean measures between PWS and obese males. However, significant differences between PWS and obese females for these measures were found only for the legs. No significant differences were identified between PWS deletion and uniparental disomy subjects. DISCUSSION: Our results demonstrate that PWS individuals do, in fact, have an unusual body composition and fatness patterns, characterized by reduced lean tissue and increased adiposity, with PWS males contributing most with fat patterns more similar to females.