Control of Glucocorticoid Receptor Levels by PTEN Establishes a Failsafe Mechanism for Tumor Suppression.

The PTEN tumor suppressor controls cell death and survival by regulating functions of various molecular targets. While the role of PTEN lipid-phosphatase activity on PtdIns(3,4,5)P3 and inhibition of PI3K pathway is well characterized, the biological relevance of PTEN protein-phosphatase activity remains undefined. Here, using knockin (KI) mice harboring cancer-associated and functionally relevant missense mutations, we show that although loss of PTEN lipid-phosphatase function cooperates with oncogenic PI3K to promote rapid mammary tumorigenesis, the additional loss of PTEN protein-phosphatase activity triggered an extensive cell death response evident in early and advanced mammary tumors. Omics and drug-targeting studies revealed that PI3Ks act to reduce glucocorticoid receptor (GR) levels, which are rescued by loss of PTEN protein-phosphatase activity to restrain cell survival. Thus, we find that the dual regulation of GR by PI3K and PTEN functions as a rheostat that can be exploited for the treatment of PTEN loss-driven cancers.

Endosome maturation links PI3Kα signaling to lysosome repopulation during basal autophagy.

Autophagy depends on the repopulation of lysosomes to degrade intracellular components and recycle nutrients. How cells co-ordinate lysosome repopulation during basal autophagy, which occurs constitutively under nutrient-rich conditions, is unknown. Here, we identify an endosome-dependent phosphoinositide pathway that links PI3Kα signaling to lysosome repopulation during basal autophagy. We show that PI3Kα-derived PI(3)P generated by INPP4B on late endosomes was required for basal but not starvation-induced autophagic degradation. PI(3)P signals were maintained as late endosomes matured into endolysosomes, and served as the substrate for the 5-kinase, PIKfyve, to generate PI(3,5)P2 . The SNX-BAR protein, SNX2, was recruited to endolysosomes by PI(3,5)P2 and promoted lysosome reformation. Inhibition of INPP4B/PIKfyve-dependent lysosome reformation reduced autophagic clearance of protein aggregates during proteotoxic stress leading to increased cytotoxicity. Therefore under nutrient-rich conditions, PI3Kα, INPP4B, and PIKfyve sequentially contribute to basal autophagic degradation and protection from proteotoxic stress via PI(3,5)P2 -dependent lysosome reformation from endolysosomes. These findings reveal that endosome maturation couples PI3Kα signaling to lysosome reformation during basal autophagy.

The mechanisms of class 1A PI3K and Wnt/ß-catenin coupled signaling in breast cancer.

The class IA PI3K signaling pathway is activated by growth factor stimulation and regulates a signaling cascade that promotes diverse events including cell growth, proliferation, migration and metabolism. PI3K signaling is one of the most commonly hyperactivated pathways in breast cancer, leading to increased tumor growth and progression. PI3K hyperactivation occurs via a number of genetic and epigenetic mechanisms including mutation or amplification of PIK3CA, the gene encoding the p110α subunit of PI3Kα, as well as via dysregulation of the upstream growth factor receptors or downstream signaling effectors. Over the past decade, extensive efforts to develop therapeutics that suppress oncogenic PI3K signaling have been undertaken. Although FDA-approved PI3K inhibitors are now emerging, their clinical success remains limited due to adverse effects and negative feedback mechanisms which contribute to their reduced efficacy. There is an emerging body of evidence demonstrating crosstalk between the PI3K and Wnt/ß-catenin pathways in breast cancer. However, PI3K exhibits opposing effects on Wnt/ß-catenin signaling in distinct tumor subsets, whereby PI3K promotes Wnt/ß-catenin activation in ER+ cancers, but paradoxically suppresses this pathway in ER- breast cancers. This review discusses the molecular mechanisms for PI3K-Wnt crosstalk in breast cancer, and how Wnt-targeted therapies have the potential to contribute to treatment regimens for breast cancers with PI3K dysregulation.

PtdIns(3,4,5)P3-dependent Rac exchanger 1 (P-Rex1) promotes mammary tumor initiation and metastasis.

The Rac-GEF, P-Rex1, activates Rac1 signaling downstream of G protein-coupled receptors and PI3K. Increased P-Rex1 expression promotes melanoma progression; however, its role in breast cancer is complex, with differing reports of the effect of its expression on disease outcome. To address this we analyzed human databases, undertook gene array expression analysis, and generated unique murine models of P-Rex1 gain or loss of function. Analysis of PREX1 mRNA expression in breast cancer cDNA arrays and a METABRIC cohort revealed that higher PREX1 mRNA in ER+ve/luminal tumors was associated with poor outcome in luminal B cancers. Prex1 deletion in MMTV-neu or MMTV-PyMT mice reduced Rac1 activation in vivo and improved survival. High level MMTV-driven transgenic PREX1 expression resulted in apicobasal polarity defects and increased mammary epithelial cell proliferation associated with hyperplasia and development of de novo mammary tumors. MMTV-PREX1 expression in MMTV-neu mice increased tumor initiation and enhanced metastasis in vivo, but had no effect on primary tumor growth. Pharmacological inhibition of Rac1 or MEK1/2 reduced P-Rex1-driven tumoroid formation and cell invasion. Therefore, P-Rex1 can act as an oncogene and cooperate with HER2/neu to enhance breast cancer initiation and metastasis, despite having no effect on primary tumor growth.

Functional and Phenotypic Characterisations of Common Syngeneic Tumour Cell Lines as Estrogen Receptor-Positive Breast Cancer Models.

Estrogen receptor-positive breast cancers (ER+ BCas) are the most common form of BCa and are increasing in incidence, largely due to changes in reproductive practices in recent decades. Tamoxifen is prescribed as a component of standard-of-care endocrine therapy for the treatment and prevention of ER+ BCa. However, it is poorly tolerated, leading to low uptake of the drug in the preventative setting. Alternative therapies and preventatives for ER+ BCa are needed but development is hampered due to a paucity of syngeneic ER+ preclinical mouse models that allow pre-clinical experimentation in immunocompetent mice. Two ER-positive models, J110 and SSM3, have been reported in addition to other tumour models occasionally shown to express ER (for example 4T1.2, 67NR, EO771, D2.0R and D2A1). Here, we have assessed ER expression and protein levels in seven mouse mammary tumour cell lines and their corresponding tumours, in addition to their cellular composition, tamoxifen sensitivity and molecular phenotype. By immunohistochemical assessment, SSM3 and, to a lesser extent, 67NR cells are ER+. Using flow cytometry and transcript expression we show that SSM3 cells are luminal in nature, whilst D2.0R and J110 cells are stromal/basal. The remainder are also stromal/basal in nature; displaying a stromal or basal Epcam/CD49f FACS phenotype and stromal and basal gene expression signatures are overrepresented in their transcript profile. Consistent with a luminal identity for SSM3 cells, they also show sensitivity to tamoxifen in vitro and in vivo. In conclusion, the data indicate that the SSM3 syngeneic cell line is the only definitively ER+ mouse mammary tumour cell line widely available for pre-clinical research.

Deletion of the phosphatase INPP5E in the murine retina impairs photoreceptor axoneme formation and prevents disc morphogenesis.

INPP5E, also known as pharbin, is a ubiquitously expressed phosphatidylinositol polyphosphate 5-phosphatase that is typically located in the primary cilia and modulates the phosphoinositide composition of membranes. Mutations to or loss of INPP5E is associated with ciliary dysfunction. INPP5E missense mutations of the phosphatase catalytic domain cause Joubert syndrome in humans-a syndromic ciliopathy affecting multiple tissues including the brain, liver, kidney, and retina. In contrast to other primary cilia, photoreceptor INPP5E is prominently expressed in the inner segment and connecting cilium and absent in the outer segment, which is a modified primary cilium dedicated to phototransduction. To investigate how loss of INPP5e causes retina degeneration, we generated mice with a retina-specific KO (Inpp5eF/F;Six3Cre, abbreviated as retInpp5e-/-). These mice exhibit a rapidly progressing rod-cone degeneration resembling Leber congenital amaurosis that is nearly completed by postnatal day 21 (P21) in the central retina. Mutant cone outer segments contain vesicles instead of discs as early as P8. Although P10 mutant outer segments contain structural and phototransduction proteins, axonemal structure and disc membranes fail to form. Connecting cilia of retInpp5e-/- rods display accumulation of intraflagellar transport particles A and B at their distal ends, suggesting disrupted intraflagellar transport. Although INPP5E ablation may not prevent delivery of outer segment-specific proteins by means of the photoreceptor secretory pathway, its absence prevents the assembly of axonemal and disc components. Herein, we suggest a model for INPP5E-Leber congenital amaurosis, proposing how deletion of INPP5E may interrupt axoneme extension and disc membrane elaboration.

AKT signaling promotes DNA damage accumulation and proliferation in polycystic kidney disease.

Polycystic kidney disease (PKD) results in the formation of renal cysts that can impair function leading to renal failure. DNA damage accumulates in renal epithelial cells in PKD, but the molecular mechanisms are unclear and are investigated here. Phosphoinositide 3-kinase (PI3K)/AKT signaling activates mammalian target of rapamycin complex 1 (mTORC1) and hyperactivation of mTORC1 is a common event in PKD; however, mTORC1 inhibitors have yielded disappointing results in clinical trials. Here, we demonstrate AKT and mTORC1 hyperactivation in two representative murine PKD models (renal epithelial-specific Inpp5e knockout and collecting duct-specific Pkd1 deletion) and identify a downstream signaling network that contributes to DNA damage accumulation. Inpp5e- and Pkd1-null renal epithelial cells showed DNA damage including double-stranded DNA breaks associated with increased replication fork numbers, multinucleation and centrosome amplification. mTORC1 activated CAD, which promotes de novo pyrimidine synthesis, to sustain cell proliferation. AKT, but not mTORC1, inhibited the DNA repair/replication fork origin firing regulator TOPBP1, which impacts on DNA damage and cell proliferation. Notably, Inpp5e- and Pkd1-null renal epithelial cell spheroid formation defects were rescued by AKT inhibition. These data reveal that AKT hyperactivation contributes to DNA damage accumulation in multiple forms of PKD and cooperates with mTORC1 to promote cell proliferation. Hyperactivation of AKT may play a causal role in PKD by regulating DNA damage and cell proliferation, independent of mTORC1, and AKT inhibition may be a novel therapeutic approach for PKD.

ß-catenin ablation exacerbates polycystic kidney disease progression.

Polycystic kidney disease (PKD) results from excessive renal epithelial cell proliferation, leading to the formation of large fluid filled cysts which impair renal function and frequently lead to renal failure. Hyperactivation of numerous signaling pathways is hypothesized to promote renal epithelial cell hyperproliferation including mTORC1, extracellular signal-regulated kinase (ERK) and WNT signaling. ß-catenin and its target genes are overexpressed in some PKD models and expression of activated ß-catenin induces cysts in mice; however, ß-catenin murine knockout studies indicate it may also inhibit cystogenesis. Therefore, it remains unclear whether ß-catenin is pro- or anti-cystogenic and whether its role is canonical WNT signaling-dependent. Here, we investigate whether ß-catenin deletion in a PKD model with hyperactived ß-catenin signaling affects disease progression to address whether increased ß-catenin drives PKD. We used renal epithelial cell specific Inpp5e-null PKD mice which we report exhibit increased ß-catenin and target gene expression in the cystic kidneys. Surprisingly, co-deletion of ß-catenin with Inpp5e in renal epithelial cells exacerbated polycystic kidney disease and renal failure compared to Inpp5e deletion alone, but did not normalize ß-catenin target gene expression. ß-catenin/Inpp5e double-knockout kidneys exhibited increased cyst initiation, cell proliferation and MEK/ERK signaling compared to Inpp5e-null, associated with increased fibrosis, which may collectively contribute to accelerated disease. Therefore, increased ß-catenin and WNT target gene expression are not necessarily cyst promoting. Rather ß-catenin may play a dual and context-dependent role in PKD and in the presence of other cyst-inducing mutations (Inpp5e-deletion); ß-catenin loss may exacerbate disease in a WNT target gene-independent manner.

Predictive factors for fertility preservation in pediatric and adolescent girls with planned gonadotoxic treatment.

PURPOSE: To characterize female pediatric and adolescent patients seen for fertility preservation consultation at an academic medical center and to describe the association between demographic or clinical factors and the use of fertility preservation treatment (FPT). METHODS: This is a retrospective chart analysis of female pediatric and adolescent patients seen for fertility preservation consultation at an academic fertility center over a 14-year period from 2005 to 2019. RESULTS: One hundred six females aged 3-21 years were seen for fertility preservation consultation with a mean age of 16.6 years. Diagnoses included hematologic malignancies (41.5%), gynecologic malignancies (9.4%), other malignancies (31.1%), non-malignant hematologic disease (14.2%), and non-malignant conditions (3.8%). Overall, 64.2% of subjects pursued fertility preservation, including oocyte cryopreservation (35.8%) and ovarian tissue cryopreservation (23.6%). Overall, age, minority race, diagnosis, time since diagnosis, and median household income were not significantly associated with odds of completing an FPT procedure. Among all patients, those who underwent gonadotoxic therapy prior to consultation had a lower odds of receiving FPT (OR= 0.24, 95% CI 0.10-0.55). Among patients without chemotherapy exposure, no factors were associated with FPT. CONCLUSIONS: Among pediatric and adolescent patients at an academic center undergoing a fertility preservation consultation, there were no socioeconomic or clinical barriers to FPT use in those who had not yet undergone gonadotoxic therapy. The only factor that was negatively associated with odds of pursuing FPT was prior chemotherapy exposure.

The myotubularin MTMR4 regulates phagosomal phosphatidylinositol 3-phosphate turnover and phagocytosis.

Macrophage phagocytosis is required for effective clearance of invading bacteria and other microbes. Coordinated phosphoinositide signaling is critical both for phagocytic particle engulfment and subsequent phagosomal maturation to a degradative organelle. Phosphatidylinositol 3-phosphate (PtdIns(3)P) is a phosphoinositide that is rapidly synthesized and degraded on phagosomal membranes, where it recruits FYVE domain- and PX motif-containing proteins that promote phagosomal maturation. However, the molecular mechanisms that regulate PtdIns(3)P removal from the phagosome have remained unclear. We report here that a myotubularin PtdIns(3)P 3-phosphatase, myotubularin-related protein-4 (MTMR4), regulates macrophage phagocytosis. MTMR4 overexpression reduced and siRNA-mediated Mtmr4 silencing increased levels of cell-surface immunoglobulin receptors (i.e. Fcγ receptors (FcγRs)) on RAW 264.7 macrophages, associated with altered pseudopodal F-actin. Furthermore, MTMR4 negatively regulated the phagocytosis of IgG-opsonized particles, indicating that MTMR4 inhibits FcγR-mediated phagocytosis, and was dynamically recruited to phagosomes of macrophages during phagocytosis. MTMR4 overexpression decreased and Mtmr4-specific siRNA expression increased the duration of PtdIns(3)P on phagosomal membranes. Macrophages treated with Mtmr4-specific siRNA were more resistant to Mycobacterium marinum-induced phagosome arrest, associated with increased maturation of mycobacterial phagosomes, indicating that extended PtdIns(3)P signaling on phagosomes in the Mtmr4-knockdown cells permitted trafficking of phagosomes to acidic late endosomal and lysosomal compartments. In conclusion, our findings indicate that MTMR4 regulates PtdIns(3)P degradation in macrophages and thereby controls phagocytosis and phagosomal maturation.

Navigating the body of literature assessing BRCA1/2 mutations and markers of ovarian function: a systematic review and meta-analysis.

PURPOSE: Twelve percent of women in the USA will develop invasive breast cancer in their lifetime, and that risk increases to 80% if they carry a BRCA1 or BRCA2 mutation. BRCA1/2 mutations are thought to potentially affect ovarian reserve and/or fertility. METHODS: PubMed and PubMed Central were searched for publications on ovarian reserve-related outcomes (i.e., AMH and response to controlled ovarian hyperstimulation (COH) protocols) that were reported in relation to BRCA1 and/or BRCA2 mutations from 1950 through May 2019. A meta-analysis was conducted to create forest plots and summary effect measures using Review Manager 5.3. RESULTS: This article reviews the 16 qualifying publications. There were several fundamental methodological differences in the study designs and outcome details reported in AMH studies. Summary statistics found no difference in AMH levels between BRCA1/2+ women as compared with controls (Z overall test effects p ≥ 0.45). Regarding responses to COH, there were overall non-significantly fewer total and mature numbers of oocytes retrieved in BRCA1/2+ cases as compared with controls (meta-analysis Z overall test effects p ≥ 0.40). CONCLUSIONS: While the summary measures indicate no significant differences in AMH levels between BRCA1/2+ cases and controls, readers should be aware that there are significant methodological differences in the AMH reports. Additionally, the response to COH protocols does not seem to be significantly lower in BRCA1/2 mutation carriers in the existing literature. Continued research on both of these clinical parameters would be beneficial for patient counseling.

PTEN and Other PtdIns(3,4,5)P3 Lipid Phosphatases in Breast Cancer.

The phosphoinositide 3-kinase (PI3K)/AKT signalling pathway is hyperactivated in ~70% of breast cancers. Class I PI3K generates PtdIns(3,4,5)P3 at the plasma membrane in response to growth factor stimulation, leading to AKT activation to drive cell proliferation, survival and migration. PTEN negatively regulates PI3K/AKT signalling by dephosphorylating PtdIns(3,4,5)P3 to form PtdIns(4,5)P2. PtdIns(3,4,5)P3 can also be hydrolysed by the inositol polyphosphate 5-phosphatases (5-phosphatases) to produce PtdIns(3,4)P2. Interestingly, while PTEN is a bona fide tumour suppressor and is frequently mutated/lost in breast cancer, 5-phosphatases such as PIPP, SHIP2 and SYNJ2, have demonstrated more diverse roles in regulating mammary tumourigenesis. Reduced PIPP expression is associated with triple negative breast cancers and reduced relapse-free and overall survival. Although PIPP depletion enhances AKT phosphorylation and supports tumour growth, this also inhibits cell migration and metastasis in vivo, in a breast cancer oncogene-driven murine model. Paradoxically, SHIP2 and SYNJ2 are increased in primary breast tumours, which correlates with invasive disease and reduced survival. SHIP2 or SYNJ2 overexpression promotes breast tumourigenesis via AKT-dependent and independent mechanisms. This review will discuss how PTEN, PIPP, SHIP2 and SYNJ2 distinctly regulate multiple functional targets, and the mechanisms by which dysregulation of these distinct phosphoinositide phosphatases differentially affect breast cancer progression.

Integrating Community-Engagement and a Multiphase Optimization Strategy Framework: Adapting Substance Use Prevention for American Indian Families.

Initiation of substance use often occurs earlier among American Indian (AI) youth than among other youth in the USA, bringing increased risk for a variety of poor health and developmental outcomes. Effective prevention strategies are needed, but the evidence base remains thin for this population. Research makes clear that prevention strategies need to be culturally coherent; programs with an evidence base in one population cannot be assumed to be effective in another. However, guidance on effective adaptation is lacking. This paper reports on cultural adaptation of an evidence-based program utilizing the multiphase optimization strategy (MOST) framework embedded within a community-engaged process to evaluate intervention components. The Strengthening Families Program for Parents and Youth 10-14 was adapted to become the Thiwáhe Gluwás'akapi Program for American Indian youth and families. Three program components were evaluated for their effectiveness with regard to outcomes (youth substance use, theoretical mediators of program effects on substance use, and program attendance) in a sample of 98 families (122 youth and 137 adults). Consistent with the MOST framework, the value of components was also evaluated with regard to efficiency, economy, and scalability. Expanding on the MOST framework for cultural adaptation, we also considered the results of the MOST findings regarding the acceptability of each component from the perspectives of community members and participants. The promise of a strategic component-based approach to adapting evidence-based interventions is discussed, including the benefits of engaging community to ensure relevance and considering both cultural and scientific rationale for each component to enhance impact.

Inpp5e suppresses polycystic kidney disease via inhibition of PI3K/Akt-dependent mTORC1 signaling.

Polycystic kidney disease (PKD) is a common cause of renal failure with few effective treatments. INPP5E is an inositol polyphosphate 5-phosphatase that dephosphorylates phosphoinositide 3-kinase (PI3K)-generated PI(3,4,5)P3 and is mutated in ciliopathy syndromes. Germline Inpp5e deletion is embryonically lethal, attributed to cilia stability defects, and is associated with polycystic kidneys. However, the molecular mechanisms responsible for PKD development upon Inpp5e loss remain unknown. Here, we show conditional inactivation of Inpp5e in mouse kidney epithelium results in severe PKD and renal failure, associated with a partial reduction in cilia number and hyperactivation of PI3K/Akt and downstream mammalian target of rapamycin complex 1 (mTORC1) signaling. Treatment with an mTORC1 inhibitor improved kidney morphology and function, but did not affect cilia number or length. Therefore, we identify Inpp5e as an essential inhibitor of the PI3K/Akt/mTORC1 signaling axis in renal epithelial cells, and demonstrate a critical role for Inpp5e-dependent mTORC1 regulation in PKD suppression.

PtdIns(3,4,5)P3-dependent Rac Exchanger 1 (PREX1) Rac-Guanine Nucleotide Exchange Factor (GEF) Activity Promotes Breast Cancer Cell Proliferation and Tumor Growth via Activation of Extracellular Signal-regulated Kinase 1/2 (ERK1/2) Signaling.

PtdIns(3,4,5)P3-dependent Rac exchanger 1 (PREX1) is a Rac-guanine nucleotide exchange factor (GEF) overexpressed in a significant proportion of human breast cancers that integrates signals from upstream ErbB2/3 and CXCR4 membrane surface receptors. However, the PREX1 domains that facilitate its oncogenic activity and downstream signaling are not completely understood. We identify that ERK1/2 MAPK acts downstream of PREX1 and contributes to PREX1-mediated anchorage-independent cell growth. PREX1 overexpression increased but its shRNA knockdown decreased ERK1/2 phosphorylation in response to EGF/IGF-1 stimulation, resulting in induction of the cell cycle regulators cyclin D1 and p21(WAF1/CIP1) PREX1-mediated ERK1/2 phosphorylation, anchorage-independent cell growth, and cell migration were suppressed by inhibition of MEK1/2/ERK1/2 signaling. PREX1 overexpression reduced staurosporine-induced apoptosis whereas its shRNA knockdown promoted apoptosis in response to staurosporine or the anti-estrogen drug tamoxifen. Expression of wild-type but not GEF-inactive PREX1 increased anchorage-independent cell growth. In addition, mouse xenograft studies revealed that expression of wild-type but not GEF-dead PREX1 resulted in the formation of larger tumors that displayed increased phosphorylation of ERK1/2 but not AKT. The impaired anchorage-independent cell growth, apoptosis, and ERK1/2 signaling observed in stable PREX1 knockdown cells was restored by expression of wild-type but not GEF-dead-PREX1. Therefore, PREX1-Rac-GEF activity is critical for PREX1-dependent anchorage-independent cell growth and xenograft tumor growth and may represent a possible therapeutic target for breast cancers that exhibit PREX1 overexpression.

INPP5E interacts with AURKA, linking phosphoinositide signaling to primary cilium stability.

Mutations in inositol polyphosphate 5-phosphatase E (INPP5E) cause the ciliopathies known as Joubert and MORM syndromes; however, the role of INPP5E in ciliary biology is not well understood. Here, we describe an interaction between INPP5E and AURKA, a centrosomal kinase that regulates mitosis and ciliary disassembly, and we show that this interaction is important for the stability of primary cilia. Furthermore, AURKA phosphorylates INPP5E and thereby increases its 5-phosphatase activity, which in turn promotes transcriptional downregulation of AURKA, partly through an AKT-dependent mechanism. These findings establish the first direct link between AURKA and phosphoinositide signaling and suggest that the function of INPP5E in cilia is at least partly mediated by its interactions with AURKA.

P-Rex1 and P-Rex2 RacGEFs and cancer.

Phosphatidylinositol 3,4,5-trisphosphate-dependent Rac exchanger (P-Rex) proteins are RacGEFs that are synergistically activated by phosphatidylinositol 3,4,5-trisphosphate and Gßγ subunits of G-protein-coupled receptors. P-Rex1 and P-Rex2 share similar amino acid sequence homology, domain structure, and catalytic function. Recent evidence suggests that both P-Rex proteins may play oncogenic roles in human cancers. P-Rex1 and P-Rex2 are altered predominantly via overexpression and mutation, respectively, in various cancer types, including breast cancer, prostate cancer, and melanoma. This review compares the similarities and differences between P-Rex1 and P-Rex2 functions in human cancers in terms of cellular effects and signalling mechanisms. Emerging clinical data predict that changes in expression or mutation of P-Rex1 and P-Rex2 may lead to changes in tumour outcome, particularly in breast cancer and melanoma.

Inositol polyphosphate 4-phosphatase II (INPP4B) is associated with chemoresistance and poor outcome in AML.

Phosphoinositide signaling regulates diverse cellular functions. Phosphoinositide-3 kinase (PI3K) generates PtdIns(3,4,5)P3 and PtdIns(3,4)P2, leading to the activation of proliferative and anti-apoptotic signaling pathways. Termination of phosphoinositide signaling requires hydrolysis of inositol ring phosphate groups through the actions of PtdIns(3,4,5)P3 3-phosphatase (PTEN), PtdIns(3,4,5)P3 5-phosphatases (eg, SHIP), and PtdIns(3,4)P2 4-phosphatases (eg, INPP4B). The biological relevance of most of these phosphoinositide phosphatases in acute myeloid leukemia (AML) remains poorly understood. Mass spectrometry-based gene expression profiling of 3-, 4- and 5-phosphatases in human AML revealed significant overexpression of INPP4B. Analysis of an expanded panel of 205 AML cases at diagnosis revealed INPP4B overexpression in association with reduced responses to chemotherapy, early relapse, and poor overall survival, independent of other risk factors. Ectopic overexpression of INPP4B conferred leukemic resistance to cytosine arabinoside (ara-C), daunorubicin, and etoposide. Expression of a phosphatase inert variant (INPP4B C842A) failed to abrogate resistance of AML cells to chemotherapy in vitro or in vivo. In contrast, targeted suppression of endogenously overexpressed INPP4B by RNA interference sensitized AML cell lines and primary AML to chemotherapy. These findings demonstrate a previously unsuspected and clinically relevant role for INPP4B gain of function as a mediator of chemoresistance and poor survival outcome in AML independent of its phosphoinositide phosphatase function.

Self-Efficacy About Sexual Risk/Protective Behaviors: Intervention Impact Trajectories Among American Indian Youth.

For adolescents, normative development encompasses learning to negotiate challenges of sexual situations; of special importance are skills to prevent early pregnancy, HIV, and other sexually transmitted diseases. Disparities in sexual risk among American Indian youth point to the importance of intervening to attenuate this risk. This study explored the impact of Circle of Life (COL), an HIV prevention intervention based on social cognitive theory, on trajectories of self-efficacy (refusing sex, avoiding sexual situations) among 635 students from 13 middle schools on one American Indian reservation. COL countered a normative decline of refusal self-efficacy among girls receiving the intervention by age 13, while girls participating at age 14 or older, girls in the comparison group, and all boys showed continuing declines.

Heterozygous expression of the oncogenic Pik3ca(H1047R) mutation during murine development results in fatal embryonic and extraembryonic defects.

The phosphoinositide 3-kinase (PI3K)/AKT signalling pathway regulates many cellular functions including proliferation, migration, survival and protein synthesis. Somatic mutations in PIK3CA, the gene encoding the p110α catalytic subunit of PI3K enzyme, are commonly associated with many human cancers as well as recently being implicated in human overgrowth syndromes. However, it is not clear if such mutations can be inherited through the germline. We have used a novel mouse model with Cre recombinase (Cre)-conditional knock-in of the common H1047R mutation into the endogenous Pik3ca gene. Heterozygous expression of the Pik3ca(H1047R) mutation in the developing mouse embryo resulted in failed 'turning' of the embryo and disrupted vascular remodelling within the embryonic and extraembryonic tissues, leading to lethality prior to E10. As vascular endothelial growth factor A (VEGF-A) signalling was disrupted in these embryos, we used Cre under the control of the Tie2 promoter to target the Pik3ca(H1047R) mutation specifically to endothelial cells. In these embryos turning occurred normally but the vascular remodelling defects and embryonic lethality remained, likely as a result of endothelial hyperproliferation. Our results confirm the lethality associated with heterozygous expression of the Pik3ca(H1047R) mutation during development and likely explain the lack of inherited germline PIK3CA mutations in humans.