BET inhibitors enhance embryonic and fetal globin expression in erythroleukemia cell lines

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The histone methyltransferase inhibitor A-366 enhances hemoglobin expression in erythroleukemia cells upon co‐exposure with chemical inducers in culture

Background Erythroleukemia is caused by the uncontrolled multiplication of immature erythroid progenitor cells which fail to differentiate into erythrocytes. By directly targeting this class of malignant cells, the induction of terminal erythroid differentiation represents a vital therapeutic strategy for this disease. Erythroid differentiation involves the execution of a well-orchestrated gene expression program in which epigenetic enzymes play critical roles. In order to identify novel epigenetic mediators of differentiation, this study explores the effects of multiple, highly specific, epigenetic enzyme inhibitors, in murine and human erythroleukemia cell lines. Results We used a group of compounds designed to uniquely target the following epigenetic enzymes: G9a/GLP, EZH1/2, SMYD2, PRMT3, WDR5, SETD7, SUV420H1 and DOT1L. The majority of the probes had a negative impact on both cell proliferation and differentiation. On the contrary, one of the compounds, A-366, demonstrated the opposite effect by promoting erythroid differentiation of both cell models. A-366 is a selective inhibitor of the G9a methyltransferase and the chromatin reader Spindlin1. Investigation of the molecular mechanism of action revealed that A-366 forced cells to exit from the cell cycle, a fact that favored erythroid differentiation. Further analysis led to the identification of a group of genes that mediate the A-366 effects and include CDK2, CDK4 and CDK6. Conclusions A-366, a selective inhibitor of G9a and Spindlin1, demonstrates a compelling role in the erythroid maturation process by promoting differentiation, a fact that is highly beneficial for patients suffering from erythroleukemia. In conclusion, this data calls for further investigation towards the delivery of epigenetic drugs and especially A-366 in hematopoietic disorders.

Overcoming the UCB HSCs –Derived NK Cells Dysfunctionality through Harnessing RAS/MAPK, IGF-1R and TGF-β Signaling Pathways

BackgroundNatural killer (NK) cells differentiated from umbilical cord blood (UCB) hematopoietic stem cells (HSCs) may be more suitable for cell-based immunotherapy compared to NK cells from adult donors. This is due to opportunity to choose alloreactive donors and potentially more robust in vivo expansion. However, the cytotoxicity of UCB-HSC derived NK cells against cancer cells might be suboptimal. To overcome this obstacle, we attempted to generate NK cells with potent antitumor activity by targeting RAS/MAPK, IGF-1R and TGF-β signaling pathways.MethodsThe CD34+ cells isolated from human UCB mononuclear cells through MACS with purity of (≥90%) were used to be differentiated into NK cells. After 21 days of induction with SFTG36, IS721 and IL-15/Hsp70 media, NK cells phenotype was studied and their cytotoxicity against K562 human erythroleukemia cell and SKOV3 ovarian carcinoma cells was analyzed.ResultsThe induced NK cells treated with SFTG36/I721 and SFTG36/IS721 growth factor cocktail expressed a phenotype with CD56+16+CD3- and NKG2D+ with mean fluorescence intensity (MFI) of 92.7%±1.45-168.00±19.20 and 93.23%±0.75-168.66±20.00 respectively. These NK cells once activated by IL-15, demonstrated a higher cytotoxicity against K562 (≥90%) (P ≤ 0.001) and SKOV3 tumor cells (≥65%) (P ≤ 0.001) compared to IL-15/Hsp70 activated NK cells.Conclusion The differentiation of ex vivo-expanded CD34+ cells through manipulation of RAS/MAPK, IGF-1R and TGF-β signaling pathways is an efficient approach for generating functional NK cells that can be used for cancer immunotherapy.

Análisis de líneas celulares eritroleucémicas con deleciones de genes implicados en el desarrollo de enfermedades hematológicas severas

La línea celular murina MEL (Murine Erythroleukemia cell line) deriva de progenitores eritroides transformados con el complejo vírico Friend, formado por el “spleen focus forming virus” (SFFV) y el “Friend murine leukemia virus” (F-MuLV). Un atributo extremadamente útil de las células MEL radica en su capacidad para retomar el programa de diferenciación mediante la utilización de inductores químicos tales como el hexametilen-bisacetamida (HMBA). En un intento por identificar posibles dianas del HMBA se establecieron líneas celulares eritroleucémicas, derivadas de MEL, que son resistentes a la acción del agente inductor (MEL-R). En un estudio reciente, se han identificado los genes Was y Btk con mayor expresión diferencial en MEL respecto a MEL-R3. Estos genes comparten dos características comunes importantes: están implicados en la organización del citoesqueleto de actina y se activan específicamente en el linaje hematopoyético. Las mutaciones producidas en Was y Btk provocan el desarrollo de enfermedades hematológicas severas. La pérdida de función de Was desencadena el desarrollo del síndrome de Wiskott-Aldrich, asociado a defectos en una gran cantidad de procesos celulares que inducen inmunodeficiencias, trombocitopenia y alteraciones autoinmunes. Asimismo, la inhibición de Btk afecta a las vías de señalización TLR2 y TLR4 de células mieloides, la función de la interleuquina 10 y STAT3 de células dendríticas.

BCR-ABL and Src Family Kinases Induce YAP Tyrosine Phosphorylation Resulting in Survivin and Cyclin D1 Expression in Chronic Myeloid Leukemia Cells

Chronic myeloid leukemia (CML) is caused by the BCR-ABL fusion protein. To date, several downstream signaling pathways of BCR-ABL have been reported to underlie the leukemogenesis of CML such as the JAK/STAT pathway, the PI3K/AKT pathway, and the Grb2/MAPK pathway. Furthermore, the Src family kinases (SFKs), especially Hck, Lyn and Fyn, have been suggested to be involved in BCR-ABL-induced transformation. Although these studies have revealed important aspects of the downstream signals of BCR-ABL, the detailed molecular mechanism of CML has not been thoroughly elucidated. Yes-associated protein (YAP) is a transcriptional cofactor that functions as an effector of the Hippo pathway which regulates cell growth and survival. In the classical Hippo pathway, YAP phosphorylated at serine 127 (S127) by LATS1/2 is bound to 14-3-3 and prevented from nuclear translocation. Apart from this serine/threonine phosphorylation, YAP undergoes phosphorylation at several tyrosine residues by various kinases to be activated. SFKs can phosphorylate and activate YAP, which has been demonstrated in some tumors. Among the several possible phosphorylated tyrosine residues, the phosphorylation at Y357 (p-Y357) has been demonstrated to be the most important for tumorigenesis. Therefore, it is possible that BCR-ABL directly or indirectly phosphorylates YAP through SFKs and thus activated YAP is translocated into the nucleus and together with TEAD induces expression of genes necessary for cell growth and survival. In the present study, we investigated the effects of imatinib and an SFK-specific inhibitor RK-20449 on viable cell number, YAP p-Y357 and expression of Survivin as well as Cyclin D1 in CML-derived cell lines in comparison with AML-derived cell lines. Furthermore, we established BCR-ABL stable transfectants and the control lines derived from TF-1, a factor dependent human erythroleukemia cell line, in order to verify our results obtained with CML-derived cell lines. We first checked the phosphorylation status of YAP and found that it was constitutively phosphorylated at tyrosine 357in CML-derived cell lines (TCC-S and K562) but not in AML-derived cell lines (HL-60 and KG-1a). Treatment with imatinib or RK-20449 inhibited cell growth and decreased tyrosine phosphorylation of YAP in both CML lines. Expression of Survivin or Cyclin D1 was decreased at least in TCC-S but not in AML cell lines. Furthermore, we established BCR-ABL stable transfectant and control empty vector transfectant from TF-1, a factor dependent human erythroleukemia cell line, in order to verify our results obtained with CML cell lines. YAP was phosphorylated at Y357 constitutively in BCR-ABL stable transfectant but not in control transfectant, and treatment with imatinib or RK-20449 inhibited cell growth, YAP tyrosine phosphorylation, and expression of Cyclin D1 in BCR-ABL stable transfectant. These results suggest that BCR-ABL induces tyrosine phosphorylation of YAP presumably through Src family kinases, which results in expression of Survivin and Cyclin D leading to leukemogenesis in CML cells. We have not determined which SFK is involved in the downstream signaling of BCR-ABL. Overexpression experiments in HEK293T have indicated that Lck, Lyn and Fyn can phosphorylate YAP at Y357 without BCR-ABL. However, it remains to be determined which SFK is activated by BCR-ABL and practically involved in YAP phosphorylation resulting in leukemogenesis. Further studies are required to specify the relevant SFKs and disclose the downstream signaling from activated YAP. Disclosures No relevant conflicts of interest to declare.

Synthesis of Flavone Derivatives via N-Amination and Evaluation of Their Anticancer Activities

Seventeen new flavone derivatives substituted at the 4′-OH position were designed, synthesized and evaluated for their anticancer and antibacterial activities. Among them, compounds 3, 4, 6f, 6e, 6b, 6c and 6k demonstrated the most potent antiproliferative activities against a human erythroleukemia cell line (HEL) and a prostate cancer cell line (PC3). The results also showed that the IC50 value of compounds 3, 4, 6f, 6e, 6b, 6c and 6k were close to that of the anticancer drug cisplatin (DDP) and lower than that of apigenin. All of the derivatives did not present antibacterial activities. The structure–activity relationships evaluation showed that the configuration of methyl amino acid might affect their biological activities.