Cooperation Between the CD20 Receptor and hIFN-Alpha Receptor in Overriding the Blocked CD20 Cell-Signaling in Rituximab-Resistant B-NHL By the Fusion Protein Anti-CD20-hIFN-Alpha

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 1468-1468
Author(s):  
Gabriel G Vega ◽  
Luz A Franco-Cea ◽  
Sara Huerta-Yepez ◽  
Hector Mayani ◽  
Otoniel Martinez-Maza ◽  
...  
Keyword(s):  
Fusion Protein ◽  
Cell Signaling ◽  
Cell Survival ◽  
Cell Lines ◽  
Conflicts Of Interest ◽  
Specific Inhibitor ◽  
Underlying Mechanism ◽  
Drug Induced ◽  
Drug Sensitization ◽  
Induced Apoptosis

Abstract Introduction: The standard treatment of B-NHL consists of rituximab in combination with CHOP (RCHOP) and results in a significant clinical response. Rituximab inhibits cell-proliferation and inhibits cell survival/anti-apoptic signaling pathways. A subset of patients does not initially respond and a subset of responding patients develops resistance to RCHOP. The genetic engineering of a fusion protein, α-CD20-hIFN-α, was found to be active in the rituximab-resistant B-NHL cell lines. Objective: To investigate the underlying mechanism by which α-CD20-hIFN-α signals in the resistant lines. Hypothesis: We hypothesized that the treatment with the α-CD20-hIFN-α may result in the cooperation of both α-CD20 and hIFN-α and their interactions with corresponding receptors that will result in overriding α-CD20 blocked cell signaling. Methods: Rituximab-resistant cell lines, R-2F7 and R-Ramos, were used as models. Cell signaling was determined by western. Sensitivity to drug-induced apoptosis was done by activation of caspase 3 by flow cytometry. Results: Treatment of the R lines with α-CD20-hIFN-α resulted in the inhibition of cell growth and sensitization to doxorubicin-induced apoptosis. Treatment with single agents alone or combination was not effective. Treatment with the α-CD20-hIFN-α resulted in the inhibition of the NFκB and the p38 MAPK pathways. In addition, the hIFN-mediated signaling pathway, namely, PKC-d, was also inhibited by the α-CD20-hIFN-α.The role of PKC-d in drug sensitization was corroborated by the use of the specific inhibitor, Rotterin, which reversed the drug sensitization by α-CD20-hIFN-α and doxorubicin Conclusion: The ability of the α-CD20-hIFN-α to inhibit cell survival and anti-apoptotic pathways, that was not achieved with single agents or combination, suggested that there may be a crosslinking of the CD20 and hIFN-α receptors by α-CD20-hIFN-α and results in triggering the cells via both receptors and inhibiting intracellular survival pathways and sensitization to drug apoptosis. Clinical Implication: The findings also suggest the potential therapeutic application of the combination of α-CD20-hIFN-α and drugs for the treatment of patients resistant to RCHOP. Disclosures No relevant conflicts of interest to declare.

Rituximab-Mediated Inhibition of the PI3K-Akt Survival Signaling Pathway in B-NHL Cell Lines Leading to Downregulation of Bclxl Expression and Chemosensitization.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 2830-2830
Author(s):  
Eriko Suzuki ◽  
Ali R. Jazirehi ◽  
Benjamin Bonavida
Keyword(s):  
Cell Survival ◽  
Signaling Pathway ◽  
Cell Lines ◽  
Kinase Inhibitor ◽  
Akt Pathway ◽  
Akt Inhibitor ◽  
Drug Induced ◽  
Similar Time ◽  
Cell Lysates ◽  
Induced Apoptosis

Abstract Rituximab (chimeric anti-CD20 monoclonal antibody) has been used in the treatment of B-NHL. We have reported in vitro that rituximab treatment signals B-NHL cell lines Ramos and Daudi and inhibits both the ERK 1/2 MAPK and NF-κB signaling pathways leading to selective inhibition of Bclxl expression and sensitization to drug-induced apoptosis. The inhibition of the NF-κB signaling pathway by rituximab was shown to be due, in part, to the induction of the Raf Kinase Inhibitor Protein (RKIP) (Jazirehi, et al., 2005 Cancer Research 65:264–276). The PI3K-Akt signaling pathway is a key regulator of cell survival and aberrant activation of the PI3K-Akt pathway has been implicated in both drug resistance and resistance to apoptosis-inducing stimuli. Akt can promote cell survival by indirectly activating the proximal transcription factor NF-κB through the phosphorylation of I-kappa B kinase (I-κB) (Ozes et. al. Nature401:82–85, 1999). This study investigated whether NF-κB inhibition by rituximab and downregulation of Bclxl expression was also the result of rituximab-mediated inhibition of the PI3K-Akt pathway. Ramos and Daudi B-NHL cell lines were treated with rituximab (20 ug/ml) and cell lysates were prepared and both Akt and phospho-Akt (p-Akt) expression were examined by western blot. The findings demonstrate that both cell lines show constitutively activated p-Akt and treatment with rituximab significantly inhibited p-Akt but not Akt. Time kinetics analysis demonstrated that inhibition of p-Akt was first detected at 3–6 hours following rituximab treatment and inhibition was maintained up to 24 hours. Concomitantlly, a similar time kinetics revealed inhibition of NF-κB activity as assessed by EMSA. Since the inhibition of NF-kB activity resulted in significant downregulation of Bclxl expression, we also examined the role of the Akt pathway in the regulation of Bclxl expression. Tumor cells were treated with the Akt inhibitor LY294002 and analysis of cell lysates showed significant downregulation of Bclxl expression. Rituximab was previously shown to sensitize B-NHL cells to drug-induced apoptosis via inhibition of NF-κB activity and Bclxl expression. We examined if inhibition of the Akt pathway also chemosensitized the cells. Treatment of Ramos cells with the Akt inhibitor LY294002 significantly sensitized the cells to CDDP-induced apoptosis and synergy was achieved. Altogether, these findings demonstrate, for the first time, that rituximab inhibits the Akt pathway and that this pathway is involved in the regulation of tumor- cell resistance to chemotherapeutic drugs. This study also proposes that the Akt pathway is a potential targeting pathway for therapeutic intervention in the treatment of rituximab and drug-resistant B-NHL.

Inhibition of the Akt Pathway in MM Cell Lines by the Anti-TfR-IgG3-Avidin Fusion Protein (Anti-TfR-IgG3-Av): Role in Chemosensitization to CDDP-Induced Apoptosis

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 4473-4473
Author(s):  
Eriko Suzuki ◽  
Kazuo Umezawa ◽  
Gustavo Helguera ◽  
Tracy R Daniels ◽  
Gary Schiller ◽  
...  
Keyword(s):  
Fusion Protein ◽  
Cell Lines ◽  
Plasma Cells ◽  
Underlying Mechanism ◽  
Akt Pathway ◽  
Gene Products ◽  
Apoptotic Gene ◽  
Iκb Kinase ◽  
Direct Cytotoxicity ◽  
Induced Apoptosis

Abstract Multiple Myeloma (MM) is an incurable disease of monoclonal malignant plasma cells. Treatment of MM with conventional chemotherapeutic drugs has resulted in improved response rates, however, with no sufficient improvement in overall survival. Bortezomib has been recently used and results in significant clinical responses in refractory MM. However, many patients relapse and become refractory to cytotoxic therapies and, hence, the need for new therapies. We have generated an Anti-TfR-IgG3-Avidin Fusion Protein (Anti-TfR-IgG3-Av) that can bind MM which express high levels of transferrin receptor and can deliver biotinylated molecules into cancer cells (Ng et al PNAS2002; 79:10706). We have reported that treatment of MM with Anti-TfR-IgG3-Av results in inhibition of cell proliferation and direct cytotoxicity in few cell lines. Further, we have also found that Anti-TfR-IgG3-Av can sensitize resistant MM cells to drugs (eg. CDDP)-induced apoptosis. Sensitization by Anti-TfR-IgG3-Av resulted in the inhibition of several anti-apoptotic gene products like XIAP, Bid, Bcl-2 and BclXL. Since these gene products are regulated by the NF-κB pathway, we hypothesized that Anti-TfR-IgG3-Av may inhibit the AKT pathway in MM cell lines. The AKT signaling inactivates several pro-apoptotic factors, such as Bad, which is phosphorylated and inhibits its binding and inactivation of BclXL. AKT also activates IκB kinase (IKK) to phosphorylate IκB (inhibitor of NF-κB ) and leading to its proteasomal degradation and NF-κB nuclear localization. The AKT and NF-κB pathways result in the transcription of many anti-apoptotic gene products like XIAP, Bcl-2, survivin and BclXL. Treatment of MM cell lines with Anti-TfR-IgG3-Av resulted in inhibition of phospho-AKT and inhibition of NF-κB activity and downstream inhibition of above anti-apoptotic gene products. We then examined the roles of AKT and NF-κB in Anti-TfR-IgG3-Av-induced sensitization of MM to CDDP-apoptosis. Treatment of IM-9 cells with siRNA AKT, not control siRNA, resulted in inhibition of AKT concomitantly with inhibition of Bcl-2 and survive in. The cells treated with si-RNA AKT were sensitized to CDDP-induced apoptosis. These findings suggested that Anti-Anti-TfR-IgG3-Av-induced sensitization to CDDP may be due, in part, to inhibition of AKT. Likewise, the role of NF-κB inhibition by Anti-TfR-IgG3-Av in the sensitization to CDDP was demonstrated by the use of the specific NF-κB inhibitor, DHMEQ. Thus, both inhibition of AKT and NF-κB pathways by Anti-TfR-IgG3-Av play a major role in Anti-TfR-IgG3-Av-induced sensitization to CDDP. The apoptosis achieved by the combination of Anti-TfR-IgG3-Av and CDDP resulted from the complementation of several gene products modified by each agent alone and resulting in the activation of caspases 9, 8 and 3 and apoptosis. The above findings provide an underlying mechanism of Anti-TfR-IgG3-Av-induced cell signaling modification that renders drug-resistant MM cells sensitive to apoptosis by drugs.

Distinct Apoptotic Responses Imparted by c-myc and max

Blood ◽  
1998 ◽  
Vol 92 (3) ◽  
pp. 1003-1010 ◽  
Author(s):  
Chadd E. Nesbit ◽  
Saijun Fan ◽  
Hong Zhang ◽  
Edward V. Prochownik
Keyword(s):  
Cell Death ◽  
Cell Lines ◽  
Ectopic Expression ◽  
Drug Induced ◽  
Enhanced Sensitivity ◽  
Contrast Enhanced ◽  
Apoptotic Pathways ◽  
American Society ◽  
Induced Apoptosis ◽  
Cytokine Deprivation

Abstract The c-myc oncoprotein accelerates programmed cell death (apoptosis) after growth factor deprivation or pharmacological insult in many cell lines. We have shown that max, the obligate c-myc heterodimeric partner protein, also promotes apoptosis after serum withdrawal in NIH3T3 fibroblasts or cytokine deprivation in interleukin-3 (IL-3)-dependent 32D murine myeloid cells. We now show that c-myc– and max-overexpressing 32D cells differ in the nature of their apoptotic responses after IL-3 removal or treatment with chemotherapeutic compounds. In the presence of IL-3, c-myc overexpression enhances the sensitivity of 32D cells to Etoposide (Sigma, St Louis, MO), Adriamycin (Pharmacia, Columbus, OH), and Camptothecin (Sigma), whereas max overexpression increases sensitivity only to Camptothecin. Drug treatment of c-myc–overexpressing cells in the absence of IL-3 did not alter the spectrum of drug sensitivity other than to additively accelerate cell death. In contrast, enhanced sensitivity to Adriamycin, Etoposide, and Taxol (Bristol-Meyers Squibb, Princeton, NJ) was revealed in max-overexpressing cells concurrently deprived of IL-3. Differential rates of apoptosis were not strictly correlated with the ability of the drugs to promote G1 or G2/M arrest. Ectopic expression of Bcl-2 or Bcl-XL blocked drug-induced apoptosis in both cell lines. In contrast, whereas Bcl-2 blocked apoptosis in both cell lines in response to IL-3 withdrawal, Bcl-XL blocked apoptosis in max-overexpressing cells but not in c-myc–overexpressing cells. These results provide mechanistic underpinnings for the idea that c-myc and max modulate distinct apoptotic pathways. © 1998 by The American Society of Hematology.

Expression of functional interleukin-15 receptor and autocrine production of interleukin-15 as mechanisms of tumor propagation in multiple myeloma

Blood ◽  
2000 ◽  
Vol 95 (2) ◽  
pp. 610-618 ◽  
Author(s):  
Inge Tinhofer ◽  
Ingrid Marschitz ◽  
Traudl Henn ◽  
Alexander Egle ◽  
Richard Greil
Keyword(s):  
Multiple Myeloma ◽  
Cell Survival ◽  
Cell Lines ◽  
Plasma Cells ◽  
Constitutive Expression ◽  
Myeloma Cell ◽  
Myeloma Cells ◽  
Cytotoxic Treatment ◽  
Interleukin 15 ◽  
Induced Apoptosis

Interleukin-15 (IL-15) induces proliferation and promotes cell survival of human T and B lymphocytes, natural killer cells, and neutrophils. Here we report the constitutive expression of a functional IL-15 receptor (IL-15R) in 6 of 6 myeloma cell lines and in CD38high/CD45low plasma cells belonging to 14 of 14 patients with multiple myeloma. Furthermore, we detected IL-15 transcripts in all 6 myeloma cell lines, and IL-15 protein in 4/6 cell lines and also in the primary plasma cells of 8/14 multiple myeloma patients. Our observations confirm the existence of an autocrine IL-15 loop and point to the potential paracrine stimulation of myeloma cells by IL-15 released from the cellular microenvironment. Blocking autocrine IL-15 in cell lines increased the rate of spontaneous apoptosis, and the degree of this effect was comparable to the pro-apoptotic effect of depleting autocrine IL-6 by antibody targeting. IL-15 was also capable of substituting for autocrine IL-6 in order to promote cell survival and vice versa. In short-term cultures of primary myeloma cells, the addition of IL-15 reduced the percentage of tumor cells spontaneously undergoing apoptosis. Furthermore, IL-15 lowered the responsiveness to Fas-induced apoptosis and to cytotoxic treatment with vincristine and doxorubicin but not with dexamethasone. These data add IL-15 to the list of important factors promoting survival of multiple myeloma cells and demonstrate that it can be produced and be functionally active in an autocrine manner.

scholarly journals Luteinizing hormone inhibits Fas-induced apoptosis in ovarian surface epithelial cell lines

2006 ◽  
Vol 188 (2) ◽  
pp. 227-239 ◽  
Author(s):  
K A Slot ◽  
M de Boer-Brouwer ◽  
M Houweling ◽  
A B Vaandrager ◽  
J H Dorrington ◽  
...  
Keyword(s):  
Cell Lines ◽  
Morphological Changes ◽  
Specific Inhibitor ◽  
Ovarian Surface Epithelium ◽  
Surface Epithelium ◽  
Fas Receptor ◽  
Ovarian Surface ◽  
Major Player ◽  
Induced Apoptosis

Gonadotrophins including LH have been suggested to play an important role in the etiology of epithelial ovarian cancers. The goal of the present study was to obtain more insight in the mechanism of gonadotrophin action on ovarian surface epithelium (OSE) cells. As the Fas system is known to be a major player in the regulation of the process of apoptosis in the ovary, we investigated whether LH interfered with Fas-induced apoptosis in the human OSE cancer cell lines HEY and Caov-3. Activation of Fas receptor by an agonistic anti-Fas receptor antibody induced apoptosis, as was evaluated by caspase-3 activation, poly(ADP-ribose) polymerase fragmentation, phosphatidylserine externalization and morphological changes characteristic of apoptosis. Co-treatment with LH reduced the number of apoptotic cells following activation of Fas in a transient manner, while LH by itself did not affect apoptosis or cell proliferation. The anti-apoptotic effect of LH could be mimicked by the membrane-permeable cAMP analog 8-(4-chlorophenylthio) cAMP (8-CPT-cAMP), and blocked by H89, a specific inhibitor of protein kinase A (PKA). In conclusion, these findings suggest that LH protects HEY cells against Fas-induced apoptosis through a signaling cascade involving PKA. Although it is plausible that in vivo LH might also enhance OSE tumor growth through inhibition of apoptosis, further research is necessary to confirm this hypothesis.

scholarly journals Elevated pressure enhanced TRAIL-induced apoptosis in hepatocellular carcinoma cells via ERK1/2-inactivation

2015 ◽  
Vol 20 (4) ◽  
Author(s):  
Eunyoung Hong ◽  
Eunil Lee ◽  
Joonhee Kim ◽  
Daeho Kwon ◽  
Yongchul Lim
Keyword(s):  
Specific Inhibitor ◽  
Underlying Mechanism ◽  
Elevated Pressure ◽  
Mitochondrial Pathway ◽  
Carcinoma Cells ◽  
Intrinsic Resistance ◽  
Hep3b Cells ◽  
Induced Apoptosis

AbstractThe high frequency of intrinsic resistance to TNF-related apoptosisinducing ligand (TRAIL) in tumor cell lines has necessitated the development of strategies to sensitize tumors to TRAIL-induced apoptosis. We previously showed that elevated pressure applied as a mechanical stressor enhanced TRAIL-mediated apoptosis in human lung carcinoma cells in vitro and in vivo. This study focused on the effect of elevated pressure on the sensitization of TRAIL-resistant cells and the underlying mechanism. We observed elevated pressure-induced sensitization to TRAIL-mediated apoptosis in Hep3B cells, accompanied by the activation of several caspases and the mitochondrial signaling pathway. Interestingly, the enhanced apoptosis induced by elevated pressure was correlated with suppression of extracellular signal-regulated protein kinase 1 and 2 (ERK1/2) phosphorylation and CREB without any change to other MAPKs. Phosphorylation of Bcl-2-associated death promoter (BAD) also decreased, leading to inhibition of the mitochondrial pathway. To confirm whether the activation of pERK1/2 plays a key role in the TRAIL-sensitizing effect of elevated pressure, Hep3B cells were pre-treated with the ERK1/2-specific inhibitor PD98059 instead of elevated pressure. Co-treatment with PD98059 and TRAIL augmented TRAIL-induced apoptosis and decreased BAD phosphorylation. The inhibition of ERK1/2 activation by elevated pressure and PD98059 also reduced BH3 interacting-domain death agonist (BID), thereby amplifying apoptotic stress at the mitochondrial level. Our results suggest that elevated pressure enhances TRAIL-induced apoptosis of Hep3B cells via specific suppression of ERK1/2 activation among MAPKs.

Regulation of Chemoresistance and Immune Resistance of B-NHL Cell Lines by Overexpression of YY1 and Bcl-xL, Respectively: Reversal of Resistance by Rituximab.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 1517-1517
Author(s):  
Mario I. Vega ◽  
Ali R. Jazirehi ◽  
Sara Huerta-Yepez ◽  
Benjamin Bonavida
Keyword(s):  
Tumor Cells ◽  
Cell Lines ◽  
Drug Induced ◽  
Direct Role ◽  
No Donor ◽  
Immune Resistance ◽  
Apoptosis Inhibition ◽  
Immune Mediated ◽  
Induced Apoptosis

Abstract We have recently reported that treatment of B-NHL cell lines with rituximab sensitizes the tumor cells to both chemotherapy and Fas-induced apoptosis (Jazirehi and Bonavida, 2005, Oncogene, 24:2121–2145). This study investigated the underlying molecular mechanism of rituximab-mediated reversal of resistance. Treatment of B-NHL cell lines inhibited the constitutively activated NF- κB. Cells expressing dominant active IκB or treated with NF-κB specific inhibitors were sensitized to both drugs and FasL agonist mAb (CH-11)-induced apoptosis. Downregulation of Bcl-xL expression via inhibition of NF-κB activity correlated with chemosensitivity. The direct role of Bcl-xL in chemoresistance was demonstrated by the use of Bcl-xL overexpressing Ramos cells, Ramos HA-BclxL (gift from Genhong Cheng, UCLA), which were not sensitized by rituximab to drug-induced apoptosis. However, inhibition of Bcl-xL in Ramos HA-Bcl-x resulted in sensitization to drug-induced apoptosis. The role of Bcl-xL expression in the regulation of Fas resistance was not apparent as Ramos HA-Bcl cells were as sensitive as the wild type cells to CH-11-induced apoptosis. Several lines of evidence support the direct role of the transcription repressor Yin-Yang 1 (YY1) in the regulation of resistance to CH-11-induced apoptosis. Inhibition of YY1 activity by either rituximab, the NO donor DETANONOate, or following transfection with YY1 siRNA all resulted in upregulation of Fas expression and sensitization to CH-11-induced apoptosis. These findings suggest two complementary mechanisms underlying the chemo-sensitization and immuno-sensitization of B NHL cells by rituximab via inhibition of NF-κB. The regulation of chemoresistance by NF-κB is mediated via Bcl-xL expression whereas the regulation of Fas resistance by NF-κB is mediated via YY1 expression and activity. These findings suggest that drug-resistant NHL tumor cells may be sensitive to immune-mediated therapeutics.

Role of Erythropoietin Receptor in t(12;21) Positive Acute Lymphoblastic Leukemia.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 2792-2792
Author(s):  
Renate Panzer-Gruemayer ◽  
Gerd Krapf ◽  
Dominik Beck ◽  
Gerhard Fuka ◽  
Christian Bieglmayer ◽  
...  
Keyword(s):  
Cell Lines ◽  
Fusion Gene ◽  
Lymphoblastic Leukemia ◽  
Leukemic Cell ◽  
Erythropoietin Receptor ◽  
Molecular Signature ◽  
Leukemic Cells ◽  
Drug Induced ◽  
Induced Apoptosis

Abstract The chromosomal translocation t(12;21)(p13;q22) resulting in the TEL/AML1 (also known as ETV6/ RUNX1) fusion gene is the most frequent translocation in childhood B cell precursor (BCP) ALL. This type of ALL is characterized by a unique molecular signature, which includes the overexpression of the gene for the erythropoietin receptor (EpoR). So far, it is not known what causes the overexpression of the EpoR gene or whether it has any effect on the t(12;21) positive leukemia. We therefore aimed to evaluate potential mechanisms responsible for the upregulation of the EpoR in t(12;21) leukemias and to find out whether signalling via this receptor affects survival or proliferation of leukemic cells. In addition, we planned to explore signalling pathways linked to the respective effects and to elucidate relevant mechanisms that might be essential for cell survival. We first excluded the possibility that the EpoR expression is upregulated as a consequence of high Epo levels in the plasma that are induced by the patients’ low hemoglobin (Hb) levels. While Hb levels from patients with t(12;21)+ ALL were significantly lower compared to those with other subtypes of BCP ALL (median, 6,15g/dL and 7,9g/dL, respectively; p<0.001 Wilcoxon 2- sample test), which correlated with high Epo levels in the plasma, the extent of EpoR mRNA expression of leukemic cells was independent of the respective amount of Epo in the individual patient’s plasma. Next, the influence of Epo on t(12;21) + leukemic cell lines was evaluated and revealed a consistent time and dose dependent increase in proliferation (Epo concentrations 10, 50, 100U/ml for 72 hours) determined by 3H-Thymidine incorporation. This effect was abrogated upon addition of a blocking anti-EpoR antibody thereby confirming the specificity of EpoR signalling. Since Epo may have apoptosis-modulating potential in EpoR expressing malignant cells, we tested its influence on drug-induced apoptosis. For this purpose IC50 concentrations of drugs that are commonly used for the treatment of children with BCP ALL were used. A reduction of glucocorticoid (GC)-induced apoptosis by Epo was demonstrated in t(12;21)+ cell lines while no effect was seen in combination with other drugs or in t(12;21) negative cell lines. Preliminary data indicate that NF-kappa B as well as PI3K/Akt pathways are triggered by Epo, implying that they play a role in this rescue mechanism. Given that cell lines may have intrinsic changes, we are presently evaluating whether the observed results can also be reproduced in primary leukemic cells. In support of this assumption are results in a limited number of primary t(12;21)+ leukemias showing a superior survival (MTT assay) and reduced apoptosis rate to GC when cultured in the presence of Epo. These findings are in contrast to those in t(12;21) negative BCP ALLs. In conclusion, our data indicate that overexpression of EpoR in t(12;21) positive leukemias is not induced by low Hb, a feature that is generally observed in patients with this type of leukemia. Binding of Epo to its receptor in vitro leads to enhanced survival and negatively affects the sensitivity to GCs. Whether these findings have any implications on the treatment and care of patients with t(12;21)+ leukemia needs to be addressed in further studies. Financial support: OENB10720, FWF P17551-B14 and GENAU-CHILD Projekt GZ200.136/1 - VI/1/2005 to RPG.

The AML Prognostic Marker, AF1q, Is Directly Regulated by MiR-29b.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 2603-2603
Author(s):  
Yin Xiong ◽  
Zejuan Li ◽  
Aik Choon Tan ◽  
Judson Bemis ◽  
Xiuyan Xie ◽  
...  
Keyword(s):  
Cell Lines ◽  
Conflicts Of Interest ◽  
Prognostic Biomarker ◽  
Transfection Efficiency ◽  
Inverse Correlation ◽  
Underlying Mechanism ◽  
Fusion Partner ◽  
Stable Transfection ◽  
Elevated Expression ◽  
Normal Cytogenetics

Abstract Abstract 2603 Poster Board II-579 We have consistently shown that elevated expression of AF1q, an MLL fusion partner, is a poor prognostic biomarker for pediatric acute myeloid leukemia (AML), adult AML with normal cytogenetics (NC-AML), and adult myelodysplastic syndrome (MDS). However, the underlying mechanism of how AF1q is regulated in normal and abnormal hematopoiesis is still unclear. Our previous studies suggest that AF1q is highly regulated during hematopoietic cell differentiation and development and it is known that genes related to cell development and differentiation are likely to be regulated by various microRNAs. We used a variety of the web based programs to identify microRNA candidates that may potentially regulate AF1q based on the predicted targeting efficiency. We found the strongest predicted binder to the AF1q 3′untranslated region (3′UTR) was miR-29b, a member of the miR-29 family which has recently been characterized to regulate a member of the Bcl-2 family protein, Mcl-1 and other leukemia related oncogenes. We found that MiR-29b expression had a significantly inverse correlation (p<0.05) with AF1q expression in a cohort of more than 60 AML patients. This relationship is consistent with microRNA/AF1q regulation. In order to determine if miR-29b directly regulates AF1q, we chose H157 and SKMES1 lung cancer cell lines which were known to have high AF1q expression and high transfection efficiency to test if transfection of miR-29b into cells can suppress its endogenous AF1q expression. Our data showed that transfection of miR-29b into these two cell lines could indeed significantly suppress the AF1q expression both in H157 (p=0.001) and SKMES1 (p=0.004) cells. Then we wanted to determine if the miR-29b binding domain is specific in the AF1q 3′UTR region. Two reporter plasmids that contained the germline AF1q 3'UTR (GFP-A3U) and mutant AF1q 3′UTR in its microRNA binding site (GFP-A3U-Mutant) were constructed. We found that GFP readout was significantly suppressed in a stable transfection with native AF1q 3′UTR (GFP-A3U); in contrast, the GFP readout was not suppressed in a stable transfection with GFP-A3U-Mutant, suggesting that miR-29b is able to bind to the germline AF1q 3′UTR but not to the mutated 3′UTR (GFP-A3U-Mutant). These observations proved that miR-29b specifically regulates AF1q expression through its binding to the AF1q 3′UTR. Taking these observations together, we conclude that miR-29b directly regulates the leukemia associated gene AF1q. Elevated AF1q expression was found to have clinical significance in AML, thus, these findings warrant further investigation to determine if miR-29b will be able to serve as a prognostic biomarker for AML patients. Disclosures: No relevant conflicts of interest to declare.

Induction of Apoptosis In Imatinib-Resistant BCR-ABL1-Positive Leukemia Cell Lines by Bortezomib

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 4469-4469
Author(s):  
Hilmar Quentmeier ◽  
Sonja Eberth ◽  
Julia Romani ◽  
Margarete Zaborski ◽  
Hans G. Drexler
Keyword(s):  
Cell Lines ◽  
Kinase Inhibitor ◽  
Conflicts Of Interest ◽  
Lymphoblastic Leukemia ◽  
Philadelphia Chromosome ◽  
Leukemia Cell ◽  
Resistant Cell ◽  
Imatinib Resistance ◽  
Imatinib Resistant ◽  
Induced Apoptosis

Abstract Abstract 4469 The BCR-ABL1 translocation occurs in chronic myeloid leukemia (CML) and in 25% of cases with acute lymphoblastic leukemia (ALL). We screened a panel of BCR-ABL1 positive cell lines to find models for imatinib-resistance studies. Five of 19 BCR-ABL1 positive cell lines were resistant to imatinib-induced apoptosis (KCL-22, MHH-TALL1, NALM-1, SD-1, SUP-B15). None of the five resistant cell lines carried mutations in the kinase domain of BCR-ABL1 and – consequently – all also showed resistance to the second generation kinase inhibitors, nilotinib or dasatinib. All Philadelphia chromosome (Ph)-positive cell lines demonstrated constitutive phosphorylation of STAT5 and S6. Imatinib induced dephosphorylation of both BCR-ABL1 downstream effectors in responsive cell lines, but - remarkably – induced dephosphorylation of STAT5 in resistant cell lines as well. By administering well-described signalling pathway inhibitors we were able to show that activation of mTOR complex 1 was responsible for the constitutive S6 phosphorylation of imatinib-resistant cells. Neither BCR-ABL1 nor Src kinases or Ras/Rac-GTPases underlie tyrosine kinase inhibitor resistance in these cell lines. In conclusion, none of the five TKI-resistant cell lines showed aberrant activation of previously-described oncogenic pathways which would explain their resistance. These findings raise the question whether these cell lines might help to find a novel – alternative – explanation for TKI resistance. Interestingly, the proteasome inhibitor bortezomib induced apoptosis in TKI-resistant and –sensitive Ph+ cell lines. Bortezomib is being used for the treatment of multiple myeloma. Our findings support the notion that bortezomib might also be useful for the treatment of imatinib-resistant CML. Disclosures: No relevant conflicts of interest to declare.

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