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The phosphatidylinositol 3-kinase (PI3K)/Akt (protein kinase B, PKB)/mammalian Target Of Rapamycin (mTOR) signaling pathway plays a critical role in many cellular functions which are elicited by extracellular stimuli. However, constitutively active PI3K/Akt/mTOR signaling has also been firmly established as a major determinant for cell growth, proliferation, and survival in an wide array of human cancers. Thus, blocking the PI3K/AKT/mTOR signal transduction network could be an effective new strategy for targeted anticancer therapy. Pharmacological inhibitors of this signaling cascade are powerful antineoplastic agents in vitro and in xenografted models of tumors, and some of them are now being tested in clinical trials. Recent studies showed that PI3K/Akt/mTOR axis is frequently activated in acute myelogenous leukemia (AML) patient blasts and strongly contributes to proliferation, survival, and drug-resistance of these cells. Both the disease-free survival and overall survival are significantly shorter in AML cases with PI3K/Akt/mTOR upregulation. Therefore, this signal transduction cascade may represent a target for innovative therapeutic treatments of AML patients. In this review, we discuss the possible mechanisms of activation of this pathway in AML cells and the downstream molecular targets of the PI3K/Akt/mTOR signaling network which are important for blocking apoptosis, enhancing proliferation, and promoting drug-resistance of leukemic cells. We also highlight several pharmacological inhibitors which have been used to block this pathway for targeted therapy of AML. These small molecules induce apoptosis or sensitize AML cells to existing drugs, and might be used in the future for improving the outcome of this hematological disorder.

The serine/threonine kinase Akt, a downstream effector of phosphatidylinositol 3-kinase (PI3K), is known to play an important role in antiapoptotic signaling and has been implicated in the aggressiveness of a number of different human cancers including acute myeloid leukemia (AML). The progression of myelodysplastic syndromes (MDSs) to AML is thought to be associated with abrogation of apoptotic control mechanisms. However, little is known about signal transduction pathways which may be involved in enhanced survival of MDS cells. In this report, we have performed immunocytochemical and flow cytometric analysis to evaluate the levels of activated Akt in bone marrow or peripheral blood mononuclear cells from patients diagnosed with MDS. We observed high levels of Ser473 phosphorylated Akt (p-Akt) staining in 90% of the cases (n ¼ 22) diagnosed as high-risk MDS, whereas mononuclear cells from normal bone marrow or low-risk MDS patients showed low or absent Ser473 p-Akt staining. Furthermore, all high-risk MDS patients also demonstrated high expression of the Class I PI3K p110d catalytic subunit and a decreased expression of PTEN. Taken together, our results suggest that Akt activation might be one of the factors contributing to the decreased apoptosis rate observed in patients with high-risk MDS.

Background and ObjectivesThe haemoglobin level of prospective blood donors is usually performed on blood obtained by from the finger pulp by fingerstick with a lancet and filling a capillary tube with a sample. New noninvasive methods are now available for rapid, noninvasive predonation haemoglobin screening. Materials and MethodsProspective blood donors at our blood centre were tested, in two different trials, as follows: by the NBM 200 (OrSense) test (n = 445 donors) and by the Pronto-7 (Masimo) test (n = 463 donors). The haemoglobin values of each trial and the haemoglobin of finger pulp blood obtained by fingerstick with a lancet (HemoCue) were compared with the haemoglobin values obtained from a venous sample on a Cell Counter (Beckman Coulter).Results Comparison of Beckman Coulter Cell Counter and OrSense and results showed a bias of 0Á29 g/dl, the standard deviation of the differences (SDD) of 0Á98 and 95% limits of agreement from -1Á64 to 2Á21, using Bland and Altman statistical methodology. Comparison of Masimo and Beckman Coulter Cell Counter results showed a bias of -0Á53 g/dl, SDD of 1Á04 and 95% limits of agreement from -2Á57 to 1Á51. Cumulative analysis of all 908 donors, as tested by the usual fingerstick test showed a bias of 0Á83 g/dl, SDD of 0Á70 and 95% limits of agreement from -0Á54 to 2Á20 compared with the Coulter Cell Counter. Compared with the Coulter Counter, the specificity of the methods was 99Á5% for fingerstick, 97% for OrSense and 83% for Massimo, and the sensitivity was 99, 98 and 93%, respectively.Conclusions Analysis of finger pulp blood by either direct sampling by fingerstick and Hemocue, or by noninvasive haemoglobin tests does not replicate the results of cell counter analysis of venous samples. Compared with fingerstick, noninvasive haemoglobin tests eliminate pain and reduce stress, but have a lower level of specificity and sensitivity.

The serine/threonine protein kinase Akt, a downstream effector of phosphoinositide 3-kinase (PI3K), plays a pivotal role in tumorigenesis because it affects the growth and survival of cancer cells. Several laboratories have demonstrated that Akt inhibits transcriptional activation of a number of related forkhead transcription factors now referred to as FoxO1, FoxO3, and FoxO4. Akt-regulated forkhead transcription factors are involved in the control of the expression of both the cyclindependent kinase (cdk) inhibitor p27 Kip1 and proapoptotic Bim protein. Very little information is available concerning the importance of the PI3K/Akt pathway in HL60 human leukemia cells. Here, we present our findings showing that the PI3K/Akt axis regulates cell cycle progression of HL60 cells through multiple mechanisms also involving the control of FoxO1 and FoxO3. To this end, we took advantage of a HL60 cell clone (HL60AR cells) with a constitutively activated PI3K/Akt axis. When compared with parental (PT) HL60 cells, HL60AR cells displayed higher levels of phosphorylated FoxO1 and FoxO3. In AR cells forkhead factors localized predominantly in the cytoplasm, whereas in PT cells they were mostly nuclear. AR cells proliferated faster than PT cells and showed a lower amount of the cdk inhibitor p27 Kip1 , which was mainly found in the cytoplasm and was hyperphosphorylated on threonine residues. AR cells also displayed higher levels of cyclin D1 and phosphorylated p110 Retinoblastoma protein. The protein levels of cdk2, cdk4, and cdk6 were not altered in HL60AR cells, whereas the activities of both ckd2 and cdk6 were higher in AR than in PT cells. These results show that in HL60 cells the PI3K/Akt signaling pathway may be involved in the control of the cell cycle progression most likely through mechanisms involving the activation of forkhead transcription factors.