People with sickle cell disease have a chronically activated coagulation system and display hemostatic perturbations, but it is unknown whether they experience an increased risk of venous thromboembolism. We conducted a case-control study of venous thromboembolism that included 515 hospitalized black patients and 555 black controls obtained from medical clinics. All subjects were assayed for hemoglobin S and hemoglobin C genotypes. The prevalence of the S allele was 0.070 and 0.032 for case patients and controls, respectively (P < .001). The odds that a patient had sickle cell trait were approximately twice that of a control, indicating that the risk of venous thromboembolism is increased approximately 2-fold among blacks with sickle cell trait compared with those with the wild-type genotype (odds ratio = 1.8 with 95% confidence interval, 1.2-2.9). The odds ratio for pulmonary embolism and sickle cell trait was higher, 3.9 (2.2-6.9). The prevalence of sickle cell disease was also increased among case patients compared with controls. We conclude that sickle cell trait is a risk factor for venous thromboembolism and that the proportion of venous thromboembolism among blacks attributable to the mutation is approximately 7%.

Both genetic and treatment-related risk factors contribute to the development of inhibitors in haemophilia. An inhibitor surveillance system piloted at 12 US sites has the goal of assessing risk factors through prospective data collection. This report examines the relationship of genotype and race/ethnicity to history of inhibitor in a large cohort of US haemophilia patients. Mutation analysis was performed on 676 haemophilia A (HA) and 153 haemophilia B (HB) patients by sequencing, Multiplex Ligation-dependent Probe Amplification, and PCR for inversions in F8 introns 22 (inv22) and 1 (inv1). Two HB patients with deletions had history of inhibitor. In severe HA, frequency of history of inhibitor was: large deletion 57.1%, splice site 35.7%, inv22 26.8%, nonsense 24.5%, frameshift 12.9%, inv1 11.1% and missense 9.5%. In HA, 19.6% of 321 White non-Hispanics (Whites), 37.1% of 35 Black non-Hispanics (Blacks) and 46.9% of 32 Hispanics had history of inhibitor (P = 0.0003). Mutation types and novel mutation rates were similar across ethnicities. When F8 haplotypes were constructed, Whites and Hispanics showed only H1 and H2. Within H1, history of inhibitor was 12.4% in Whites, 40.0% in Blacks (P = 0.009) and 32.4% in Hispanics (P = 0.002). Inhibitor frequency is confirmed to vary by mutation type and race in a large US population. White patients with history of inhibitor did not exhibit rare F8 haplotypes. F8 gene analysis did not reveal a cause for the higher inhibitor frequencies in Black and Hispanic patients.

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PHLPP2, a member of the PH-domain leucine-rich repeat protein phosphatase (PHLPP) family, which targets oncogenic kinases, has been actively investigated as a tumor suppressor in solid tumors. Little is known, however, regarding its regulation in hematological malignancies. We observed that PHLPP2 protein expression, but not its mRNA, was suppressed in late differentiation stage acute myeloid leukemia (AML) subtypes. MicroRNAs (miR or miRNAs) from the miR-17-92 cluster, oncomir-1, were shown to inhibit PHLPP2 expression and these miRNAs were highly expressed in AML cells that lacked PHLPP2 protein.Studies showed that miR-17-92 cluster regulation was, surprisingly, independent of transcription factors c-MYC and E2F in these cells; instead all-trans-retinoic acid (ATRA), a drug used for terminally differentiating AML subtypes, markedly suppressed miR-17-92 expression and increased PHLPP2 protein levels and phosphatase activity. Finally, we demonstrate that the effect of ATRA on miR-17-92 expression is mediated through its target, transcription factor C/EBPβ, which interacts with the intronic promoter of the miR-17-92 gene to inhibit transactivation of the cluster. These studies reveal a novel mechanism for upregulation of the phosphatase activity of PHLPP2 through C/EBPβ-mediated repression of the miR-17-92 cluster in terminally differentiating myeloid cells. Phosphatases are pivotal components of intracellular signaling cascades, controlling essential processes like metabolism, apoptosis, proliferation and differentiation. 1 The PH-domain leucine-rich repeat protein phosphatase (PHLPP) family serine-threonine phosphatases are emerging as central factors in cell survival and death regulation. The PHLPP2 is a member of this family. 2,3 To date four PHLPP substrates, Akt, PKC, Mst1 and S6K1, have been identified, all kinases involved in cell survival or apoptosis. 4-7 Dephosphorylation inactivates Akt, S6K1 and PKC, and subsequently cell survival signaling, whereas dephosphorylation of Mst1 activates its apoptotic function.PHLPP protein expression and activity is suppressed through various mechanisms in cancers. Although most studies on PHLPP2 have focused on genetic alterations in solid tumors, 8 PHLPP2 protein expression in small cell lung and colorectal cancers is also restricted through translational suppression 9 and post-transcriptional control by microRNAs (miR or miRNAs), miR-205 and miR-224. 10,11 The PHLPP2 3' untranslated region (3'UTR) harbors complementary binding sites for a subset of miRNAs belonging to the miRNA-17-92 cluster. 12 This cluster comprises six miRNAs on chromosome 13, transcribed as a single polycistronic unit. 13,14 Also known as oncomir-1, the cluster enhances cell proliferation or inhibits apoptosis by suppressing targets such as Bim, E2F1 and PTEN and is markedly overexpressed in human cancers. [15][16][17][18][19][20][21] Reduced levels of PHLPP2 in chemoresistant miR-17-92 overexpressing mantle cell lymphomas had suggested that the phosphatase could be a target of oncomir-1. 12 Kno...