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Dysregulation of mRNA translation, including preferential translation of mRNA with complex 5'-UTRs such as the MYC oncogene, is recognized as an important mechanism in cancer. In this study, we show that both human and murine chronic lymphocytic leukemia (CLL) cells display a high translation rate, which can be inhibited by the synthetic flavagline FL3, a prohibitin (PHB)-binding drug. A multiomics analysis consisting of pulsed SILAC, RNA sequencing and polysome profiling performed in CLL patient samples and cell lines treated with FL3 revealed the decreased translation of the MYC oncogene and of proteins involved in cell cycle and metabolism. Furthermore, inhibition of translation was associated with a block of proliferation and a profound rewiring of MYC-driven metabolism. Interestingly, contrary to other models, the RAS-RAF-(PHBs)-MAPK pathway is neither impaired by FL3 nor implicated in translation regulation in CLL cells. Here, we rather show that PHBs are directly associated with the translation initiation complex and can be targeted by FL3. Knock-down of PHBs resembled FL3 treatment. Importantly, inhibition of translation was efficient in controlling CLL development in vivo either alone or combined with immunotherapy. Finally, high expression of translation initiation-related genes and PHBs genes correlated with poor survival and unfavorable clinical parameters in CLL patients. In conclusion, we demonstrated that translation inhibition is a valuable strategy to control CLL development by blocking the translation of several oncogenic pathways including MYC. We also unraveled a new and direct role of PHBs in translation initiation, thus creating new therapeutic opportunities for CLL patients.

Clinical trials have shown activity of the isotype-selective histone deacetylase (HDAC) inhibitor MGCD0103 in different hematologic malignancies. There are data to support the use of HDAC inhibitors in association with other cancer therapies. To propose a rational combination therapy, it is necessary to depict the molecular basis behind the cytotoxic effect of MGCD0103. In this study, we found that MGCD0103 was substantially more toxic in neoplastic B cells relative to normal cells, and we described the death pathways activated by MGCD0103 in B-cell chronic lymphocytic leukemia (CLL) cells from 32 patients. MGCD0103 decreased the expression of Mcl-1 and induced translocation of Bax to the mitochondria, mitochondrial depolarization, and release of cytochrome c in the cytosol. Caspase processing in the presence of the caspase inhibitor Q-VD-OPh and time course experiments showed that caspase-9 was the apical caspase. Thus, MGCD0103 induced the intrinsic pathway of apoptosis in CLL cells. Moreover, MGCD0103 treatment resulted in the activation of a caspase cascade downstream of caspase-9, caspase-dependent amplification of mitochondrial depolarization, activation of calpain, and Bax cleavage. We propose a model whereby the intrinsic pathway of apoptosis triggered by MGCD0103 in CLL is associated with a mitochondrial death amplification loop. Mol Cancer Ther; 9(5); 1349–60. ©2010 AACR.

Supplementary Data from The Histone Deacetylase Inhibitor MGCD0103 Induces Apoptosis in B-Cell Chronic Lymphocytic Leukemia Cells through a Mitochondria-Mediated Caspase Activation Cascade

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Simple Summary Chronic lymphocytic leukemia (CLL) is the most common leukemia in Western countries, mostly affecting the elderly. The survival of leukemic cells depends on multiple soluble factors and on the stimulation of the BCR signaling pathway. Microenvironment-dependent transcription factors also contribute to CLL biology. Here, we generated new transgenic murine conditional knock-out models of CLL to study the role of the two transcription factors HIF-1α and AHR. Unexpectedly, we observed that both factors are dispensable for leukemia development in these models. Abstract Chronic lymphocytic leukemia (CLL) is the most frequent leukemia in the elderly and is characterized by the accumulation of mature B lymphocytes in peripheral blood and primary lymphoid organs. In order to proliferate, leukemic cells are highly dependent on complex interactions with their microenvironment in proliferative niches. Not only soluble factors and BCR stimulation are important for their survival and proliferation, but also the activation of transcription factors through different signaling pathways. The aryl hydrocarbon receptor (AHR) and hypoxia-inducible factor (HIF)-1α are two transcription factors crucial for cancer development, whose activities are dependent on tumor microenvironment conditions, such as the presence of metabolites from the tryptophan pathway and hypoxia, respectively. In this study, we addressed the potential role of AHR and HIF-1α in chronic lymphocytic leukemia (CLL) development in vivo. To this end, we crossed the CLL mouse model Eµ-TCL1 with the corresponding transcription factor-conditional knock-out mice to delete one or both transcription factors in CD19+ B cells only. Despite AHR and HIF-1α being activated in CLL cells, deletion of either or both of them had no impact on CLL progression or survival in vivo, suggesting that these transcription factors are not crucial for leukemogenesis in CLL.

Exosomes are membrane-enclosed vesicles released by different cell types into the extracellular space. As mediators of intercellular communication, they are involved in multiple physiological processes, but they are also associated with the pathogenesis of human malignancies including leukemia. Isolation of exosomes enables the characterization of their role in microenvironment modulation as well as their participation in disease pathology. A variety of strategies and techniques exists to purify exosomes from many biological fluids (e.g., blood, urine, and saliva). Here, we describe the efficient production of large quantities of exosomes from leukemic cell lines by using CELLine bioreactors based on two-compartment technology, as well as their isolation and purification by combining differential centrifugation and ultracentrifugation through a density gradient (17% OptiPrep

Exosomes are membrane-enclosed vesicles released by different cell types into the extracellular space. As mediators of intercellular communication, they are involved in multiple physiological processes, but they are also associated with the pathogenesis of human malignancies including leukemia. Isolation of exosomes enables the characterization of their role in microenvironment modulation as well as their participation in disease pathology. A variety of strategies and techniques exists to purify exosomes from many biological fluids (e.g., blood, urine, and saliva). Here, we describe the efficient production of large quantities of exosomes from leukemic cell lines by using CELLine bioreactors based on two-compartment technology, as well as their isolation and purification by combining differential centrifugation and ultracentrifugation through a density gradient (17% OptiPrep™ cushion). Thus, exosomes are appropriately prepared for characterization by western blotting to detect exosome markers or imaging flow cytometry (ImageStream), and for downstream analyses such as the internalization in microenvironmental cells by confocal imaging or flow cytometry, methods which are also described in this chapter.

TO THE EDITOR: Tissue-infiltrating chronic lymphocytic leukemia (CLL) cells come in direct contact with both accessory stromal and immune cells that compose the tumor microenvironment (TME). The proliferation and survival of CLL cells is highly dependent on complex interactions with nonmalignant

Early cancer detection and disease stratification or classification are critical to successful treatment. Accessible, reliable, and informative cancer biomarkers can be medically valuable and can provide some relevant insights into cancer biology. Recent studies have suggested improvements in detecting malignancies by the use of specific extracellular microRNAs (miRNAs) in plasma. In chronic lymphocytic leukemia (CLL), an incurable hematologic disorder, sensitive, early, and noninvasive diagnosis and better disease classification would be very useful for more effective therapies. We show here that circulating miRNAs can be sensitive biomarkers for CLL, because certain extracellular miRNAs are present in CLL patient plasma at levels significantly different from healthy controls and from patients affected by other hematologic malignancies. The levels of several of these circulating miRNAs also displayed significant differences between zeta-associated protein 70 (ZAP-70) + and ZAP-70 − CLL. We also determined that the level of circulating miR-20a correlates reliably with diagnosis-to-treatment time. Network analysis of our data, suggests a regulatory network associated with BCL2 and ZAP-70 expression in CLL. This hypothesis suggests the possibility of using the levels of specific miRNAs in plasma to detect CLL and to determine the ZAP-70 status.

Clinical trials have shown activity of the isotype-selective histone deacetylase (HDAC) inhibitor MGCD0103 in different hematologic malignancies. There are data to support the use of HDAC inhibitors in association with other cancer therapies. To propose a rational combination therapy, it is necessary to depict the molecular basis behind the cytotoxic effect of MGCD0103. In this study, we found that MGCD0103 was substantially more toxic in neoplastic B cells relative to normal cells, and we described the death pathways activated by MGCD0103 in B-cell chronic lymphocytic leukemia (CLL) cells from 32 patients. MGCD0103 decreased the expression of Mcl-1 and induced translocation of Bax to the mitochondria, mitochondrial depolarization, and release of cytochrome c in the cytosol. Caspase processing in the presence of the caspase inhibitor Q-VD-OPh and time course experiments showed that caspase-9 was the apical caspase. Thus, MGCD0103 induced the intrinsic pathway of apoptosis in CLL cells. Moreover, MGCD0103 treatment resulted in the activation of a caspase cascade downstream of caspase-9, caspase-dependent amplification of mitochondrial depolarization, activation of calpain, and Bax cleavage. We propose a model whereby the intrinsic pathway of apoptosis triggered by MGCD0103 in CLL is associated with a mitochondrial death amplification loop. Mol Cancer Ther; 9(5); 1349–60. ©2010 AACR.

The main challenge in using chemotherapy to treat multiple myeloma (MM) is drug resistance. In order to evaluate the anti-neoplastic properties of a new drug combination in MM, two clinically available drugs, valproic acid (VPA) a histone deacetylase (HDAC) inhibitor and pioglitazone, a peroxisome proliferator-activated receptor gamma (PPARgamma) agonist, were tested in vitro on MM cell lines and MM patient cells. The sensitivity towards VPA alone was observed on several MM cell lines tested and also on primary myeloma cells and peripheral blood mononuclear cells from healthy donors. Importantly, the addition of a PPARgamma agonist to the VPA treatment increased the cytotoxic effect of VPA in a synergistic/additive manner on the different MM cell lines and MM patient cells. This effect was observed at the physiological range of VPA used to treat epileptic patients. The mechanisms underlying this increase induced a cell cycle arrest and caspase-dependent apoptosis. The potentiation of the effect of VPA by pioglitazone was mediated by higher acetylation levels of histones H3 and H4 compared to levels induced by HDAC inhibitors alone. This association reveals a new promising chemotherapeutic combination to be tested in MM.

MicroRNAs (miRNAs) have emerged as promising cancer biomarkers. However, exploiting their informative potential requires careful optimization of their detection. Here, we compared the efficiency of commonly used RNA extraction kits in miRNA recovery from cells, plasma and urine/plasma-derived exosomes, using single-gene RT-qPCR and miRNA profiling. We used increasing amounts of starting material to investigate the impact of the input material size on miRNA extraction. We showed that miRNA recovery was largely influenced by the isolation method and by the amount of input material. In particular, the miRCURY™ kit provided highly pure RNA. However, its columns poorly recovered miRNAs from limiting amounts of cells and plasma and rapidly saturated by large RNA species and plasma components, thus impeding miRNA recovery from high input amounts. Overall, the miRNeasy® kit permitted a better miRNA detection despite a less pure extracted RNA. Nevertheless, some miRNAs were preferentially or exclusively isolated by either of the methods. Trizol® LS resulted in very low purity RNA which affected RT-qPCR efficiency. In general, miRCURY™ biofluids kit efficiently extracted miRNAs from plasma. A careful selection of the RNA isolation method and the consideration of the type and size of input material are highly recommended to avoid biased results.

Rotating-wall vessels allow for the growth of cells in simulated microgravity. Lymphoblastoid cells cultured in rotating-wall vessels exhibited significant differences in the expression of both early and late Epstein-Barr Virus (EBV) antigens. Viral protein expression (as measured by indirect immunofluorescence) was significantly suppressed in cells cultured in simulated microgravity. A significantly greater percentage of P3HR-1 cells and Daudi cells were positive for the expression of BamH1-Z-DNA fragment of Epstein-Barr replication activator (ZEBRA), early antigen restricted (EA-R), and viral capsid antigen (VCA) in cells cultured in static tissue culture flasks as compared to cells cultured in rotating-wall vessels. We observed a 7, 11, and 25-fold reduction, respectively, for EA-R, VCA, and ZEBRA protein in P3HR-1 cells cultured in simulated microgravity. Additionally, suspension cultures of P3HR-1 cells exhibited significantly greater ZEBRA antigen expression than cells cultured in rotating-wall vessels. As an independent confirmation of the reduction in ZEBRA-protein production in simulated microgravity in P3HR-1 cells, ZEBRA-mRNA was quantitated by reverse transcription polymerase chain reaction. We observed between a 4 to 10-fold reduction in ZEBRA-mRNA in cells cultured in simulated microgravity as compared to cells cultured at 1 x g in tissue culture flasks. Rotating-wall vessels, by virtue of providing a simple culture environment triggering marked differences in viral activation, provide a model whereby both host and viral factors involved in regulating the maintenance of EBV latency can be examined.

Cigarette smoking is the major cause of cancers of the respiratory tract, including non-small cell lung cancer (NSCLC) and head and neck cancer (HNC). In order to better understand carcinogenesis of the lung and upper airways, we have compared the gene expression profiles of tumor-distant, histologically normal bronchial biopsy specimens obtained from current smokers with NSCLC or HNC (SC, considered as a single group), as well as nonsmokers (NS) and smokers without cancer (SNC). RNA from a total of 97 biopsies was used for gene expression profiling (Affymetrix HG-U133 Plus 2.0 array). Differentially expressed genes were used to compare NS, SNC, and SC, and functional analysis was carried out using Ingenuity Pathway Analysis (IPA). Smoking-related cancer of the respiratory tract was found to affect the expression of genes encoding xenobiotic biotransformation proteins, as well as proteins associated with crucial inflammation/immunity pathways and other processes that protect the airway from the chemicals in cigarette smoke or contribute to carcinogenesis. Finally, we used the prediction analysis for microarray (PAM) method to identify gene signatures of cigarette smoking and cancer, and uncovered a 15-gene signature that distinguished between SNC and SC with an accuracy of 83%. Thus, gene profiling of histologically normal bronchial biopsy specimens provided insight into cigarette-induced carcinogenesis of the respiratory tract and gene signatures of cancer in smokers.

Evading apoptosis is a hallmark of B-cell chronic lymphocytic leukemia (CLL) cells and an obstacle to current chemotherapeutic approaches. Inhibiting histone deacetylase (HDAC) has emerged as a promising strategy to induce cell death in malignant cells. We have previously reported that the HDAC inhibitor MGCD0103 induces CLL cell death by activating the intrinsic pathway of apoptosis. Here, we show that MGCD0103 decreases the autophagic flux in primary CLL cells. Activation of the PI3K/AKT/mTOR pathway, together with the activation of caspases, and to a minor extent CAPN1, resulting in cleavage of autophagy components, were involved in MGCD0103-mediated inhibition of autophagy. In addition, MGCD0103 directly modulated the expression of critical autophagy genes at the transcriptional level that may contribute to autophagy impairment. Besides, we demonstrate that autophagy is a pro-survival mechanism in CLL whose disruption potentiates cell death induced by anticancer molecules including HDAC and cyclin-dependent kinase inhibitors. In particular, our data highlight the therapeutic potential of MGCD0103 as not only an inducer of apoptosis but also an autophagy suppressor in both combination regimens with molecules like flavopiridol, known to induce protective autophagy in CLL cells, or as an alternative to circumvent undesired immunomodulatory effects seen in the clinic with conventional autophagy inhibitors.

The relationship between hypoxic stress, autophagy, and specific cell-mediated cytotoxicity remains unknown. This study shows that hypoxia-induced resistance of lung tumor to cytolytic T lymphocyte (CTL)–mediated lysis is associated with autophagy induction in target cells. In turn, this correlates with STAT3 phosphorylation on tyrosine 705 residue (pSTAT3) and HIF-1α accumulation. Inhibition of autophagy by siRNA targeting of either beclin1 or Atg5 resulted in impairment of pSTAT3 and restoration of hypoxic tumor cell susceptibility to CTL-mediated lysis. Furthermore, inhibition of pSTAT3 in hypoxic Atg5 or beclin1-targeted tumor cells was found to be associated with the inhibition Src kinase (pSrc). Autophagy-induced pSTAT3 and pSrc regulation seemed to involve the ubiquitin proteasome system and p62/SQSTM1. In vivo experiments using B16-F10 melanoma tumor cells indicated that depletion of beclin1 resulted in an inhibition of B16-F10 tumor growth and increased tumor apoptosis. Moreover, in vivo inhibition of autophagy by hydroxychloroquine in B16-F10 tumor-bearing mice and mice vaccinated with tyrosinase-related protein-2 peptide dramatically increased tumor growth inhibition. Collectively, this study establishes a novel functional link between hypoxia-induced autophagy and the regulation of antigen-specific T-cell lysis and points to a major role of autophagy in the control of in vivo tumor growth. Cancer Res; 71(18); 5976–86. ©2011 AACR.

The main challenge in using chemotherapy to treat multiple myeloma (MM) is drug resistance. In order to evaluate the anti-neoplastic properties of a new drug combination in MM, two clinically available drugs, valproic acid (VPA) a histone deacetylase (HDAC) inhibitor and pioglitazone, a peroxisome proliferator-activated receptor gamma (PPARgamma) agonist, were tested in vitro on MM cell lines and MM patient cells. The sensitivity towards VPA alone was observed on several MM cell lines tested and also on primary myeloma cells and peripheral blood mononuclear cells from healthy donors. Importantly, the addition of a PPARgamma agonist to the VPA treatment increased the cytotoxic effect of VPA in a synergistic/additive manner on the different MM cell lines and MM patient cells. This effect was observed at the physiological range of VPA used to treat epileptic patients. The mechanisms underlying this increase induced a cell cycle arrest and caspase-dependent apoptosis. The potentiation of the effect of VPA by pioglitazone was mediated by higher acetylation levels of histones H3 and H4 compared to levels induced by HDAC inhibitors alone. This association reveals a new promising chemotherapeutic combination to be tested in MM.

Hypoxia is a hallmark of solid tumors. We have recently demonstrated that exposure of tumour targets to hypoxia inhibits CTL induced autologous target cell lysis. Such inhibition is correlated to the cooperative induction of pSTAT3 and HIF-1α. Recent studies show that autophagy plays an important role in protecting cells against hypoxic stress, but the relationship between hypoxic stress and autophagy remains unclear. Here, we provide evidence that hypoxia-dependent impairment of tumor susceptibility to CTL-mediated cell lysis is associated with the induction of autophagy in tumor cells. Interestingly, inhibition of autophagy by targeting Beclin-1 or ATG-5 was sufficient to restore hypoxic tumor susceptibility to CTL and to inhibit the hypoxia-dependent phosphorylation of STAT3 on tyrosine-705 residue (pSTAT3). Furthermore, we show that the inhibition of pSTAT3 in hypoxic Atg5 or beclin-1-targeted tumor cells involves the degradation or the inhibition of the Src family protein kinase by a mechanism that involves the Ubiquitin Proteasome System (UPS). Overall, our data identify a new mechanism of pSTAT3 degradation by cooperate regulation of autophagy and the UPS under hypoxic stress. To our knowledge, this study establishes for the first time a novel functional link between hypoxia induced autophagy and tumour susceptibility to CTL-mediated lysis and highlight the use of autophagy inhibitors in immunotherapy for modulating tumor cell resistance to CTL-mediated lysis.