A retroviral mutagenesis screen reveals strong cooperation between Bc111a overexpression and loss of the Nf1 tumor suppressor gene

Masonic Cancer Center and Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, MN 55455, USA.
Blood (Impact Factor: 10.45). 11/2008; 113(5):1075-85. DOI: 10.1182/blood-2008-03-144436
Source: PubMed


NF1 inactivation occurs in specific human cancers, including juvenile myelomonocytic leukemia, an aggressive myeloproliferative disorder of childhood. However, evidence suggests that Nf1 loss alone does not cause leukemia. We therefore hypothesized that inactivation of the Nf1 tumor suppressor gene requires cooperating mutations to cause acute leukemia. To search for candidate genes that cooperate with Nf1 deficiency in leukemogenesis, we performed a forward genetic screen using retroviral insertion mutagenesis in Nf1 mutant mice. We identified 43 common proviral insertion sites that contain candidate genes involved in leukemogenesis. One of these genes, Bcl11a, confers a growth advantage in cultured Nf1 mutant hematopoietic cells and causes early onset of leukemia of either myeloid or lymphoid lineage in mice when expressed in Nf1-deficient bone marrow. Bcl11a-expressing cells display compromised p21(Cip1) induction, suggesting that Bcl11a's oncogenic effects are mediated, in part, through suppression of p21(Cip1). Importantly, Bcl11a is expressed in human chronic myelomonocytic leukemia and juvenile myelomonocytic leukemia samples. A subset of AML patients, who had poor outcomes, of 16 clusters, displayed high levels of BCL11A in leukemic cells. These findings suggest that deregulated Bcl11a cooperates with Nf1 in leukemogenesis, and a therapeutic strategy targeting the BCL11A pathway may prove beneficial in the treatment of leukemia.

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    • "BCL11A has been identified on human chromosome 2p16.1 (previously mapped at 2p13) where chromosomal abnormalities are associated with human lymphoma [10,11]. Recently, Yin et al. suggested that BCL11A acts as an oncogene and may contribute to leukemogenesis in certain groups of AML patients [12]. BCL11A overexpression is primarily found in B cell lymphoma and B cell leukemia [11,13-16]. "
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    ABSTRACT: Background B cell chronic lymphocytic leukemia/lymphoma 11 A (BCL11A) is associated with human B cell malignancy initiation. Our previous study has shown that downregulation of BCL11A mRNA by small interfering RNA (siRNA) is capable of inducing apoptosis in the SUDHL6 cell line. To further explore the effects of BCL11A siRNA on the enhanced cytotoxicity of a chemotherapeutic drug, we investigated the effects of BCL11A siRNA combined with vincristine (VCR) on SUDHL6 cell proliferation and apoptosis. Methods Chemically synthesized BCL11A siRNA was transfected into SUDHL6 cells using the HiPerFect Transfection Reagent in combination with VCR. Cell proliferation was measured by the CCK8 assay. The morphology of apoptotic cells was observed with Hoechst 33258 staining. The rate of cell apoptosis was determined by annexin V-fluorescein isothiocyanate/propidium iodide double staining using fluorescence-activated cell sorting (FACS) analysis. Results After BCL11A siRNA plus VCR treatment, cell proliferation was significantly decreased in comparison with VCR or BCL11A siRNA treatment alone and negative control siRNA plus VCR treatment (P <0.05). The apoptotic rate of BCL11A siRNA plus VCR treated cells was significantly increased compared with BCL11A siRNA and VCR treatment alone and negative control siRNA plus VCR treatment (P <0.05). Conclusions The combination of BCL11A siRNA and VCR increases apoptosis in SUDHL6 cells. Our study implies that BCL11A siRNA in combination with VCR may be a useful approach for improving effective treatment for B cell lymphoma.
    Full-text · Article · Jun 2014 · European journal of medical research
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    • "The VSV-G and HSV-TK cDNAs were inserted into the retroviral expression vectors pMIGR-his and pMSCV-puro (expressing GFP and puromycin-resistant proteins, respectively), to generate the pMIGR-VSV-G-his and pMSCV-TK-puro constructs, respectively. These constructs or the empty vectors were co-transfected with plasmids encoding packaging protein VSV-G and MuLV gag-pol, by calcium phosphate precipitation into 293T cells, to produce retroviruses, as described before (Yin et al., 2009). Retroviral supernatants were exposed to leukemic cells in the presence of 4 mg/mL polybrene. "
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    ABSTRACT: Refractoriness of acute myeloid leukemia (AML) cells to chemotherapeutics represents a major clinical barrier. Suicide gene therapy for cancer has been attractive but with limited clinical efficacy. In this study, we investigated the potential application of herpes simplex virus thymidine kinase/ganciclovir (HSV-TK/GCV) based system to inhibit chemoresistant AML cells. We first generated Ara-C resistant K562 cells and doxorubicin-resistant THP-1 cells. We found that the HSV-TK/GCV anticancer system suppressed drug resistant leukemic cells in culture. Chemoresistant AML cell lines displayed similar sensitivity to HSV-TK/GCV. Moreover, HSV-TK/GCV killing of leukemic cells was augmented to a mild but significant extent by all-trans retinoic acid (ATRA) with concomitant upregulation of Connexin 43, a major component of gap junctions. Interestingly, HSV-TK/GCV killing was enhanced by expression of vesicular stomatitis virus G glycoprotein (VSV-G), a fusogenic membrane protein, which also increased leukemic cell fusion. Co-culture resistant cells expressing HSV-TK and cells stably transduced with VSV-G showed that expression of VSV-G could promote the bystander killing effect of HSV-TK/GCV. Furthermore, combination of HSV-TK/GCV with VSV-G plus ATRA produced more pronounced antileukemia effect. These results suggest that the HSV-TK/GCV system in combination with fusogenic membrane proteins and/or ATRA could provide a strategy to mitigate the chemoresistance of AML.
    Full-text · Article · Feb 2014 · Biomolecules and Therapeutics
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    • "A previous study reported that enhanced BCL11A expression could repress P21 induction, which correlated with reduced colony formation and cell cycle arrest of leukemic cells [19]. Yin et al. also reported that BCL11A acts as an oncogene and causes leukemia in the absence of NF1 in mice, perhaps through suppression of P21 induction and thus promotion of cell growth [20]. As is well known, the NF1 suppressor gene is also frequently inactivated in NSCLC [21]. "
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    ABSTRACT: Background Aberrant activation of the proto-oncogene B-cell lymphoma/leukemia 11A (BCL11A) has been implicated in the pathogenesis of leukemia and lymphoma. However, the clinical significance of BCL11A in non-small cell lung cancer (NSCLC) remains unknown. Results We examined BCL11A expression at the protein and mRNA levels in a cohort (n = 114) of NSCLC patients and assessed the relationship between BCL11A expression and clinicopathological parameters. Data from array-based Comparative Genomic Hybridization (aCGH) and microRNA transfection experiments were integrated to explore the potential mechanisms of abnormal BCL11A activation in NSCLC. Compared to adjacent non-cancerous lung tissues, BCL11A expression levels were specifically upregulated in NSCLC tissues at both the mRNA (t = 9.81, P < 0.001) and protein levels. BCL11A protein levels were higher in patients with squamous histology (χ2 = 15.81, P = 0.001), smokers (χ2 = 8.92, P = 0.004), patients with no lymph node involvement (χ2 = 5.14, P = 0.029), and patients with early stage disease (χ2 = 3.91, P = 0.048). A multivariate analysis demonstrated that in early stage NSCLC (IA–IIB), BCL11A was not only an independent prognostic factor for disease-free survival (hazards ratio [HR] 0.24, 95% confidence interval [CI] 0.12-0.50, P < 0.001), but also for overall survival (HR = 0.23, 95% CI 0.09-0.61, P = 0.003). The average BCL11A expression level was much higher in SCC samples with amplifications than in those without amplifications (t = 3.30, P = 0.023). Assessing functionality via an in vitro luciferase reporter system and western blotting, we found that the BCL11A protein was a target of miR-30a. Conclusions Our results demonstrated that proto-oncogene BCL11A activation induced by miR-30a and gene amplification may be a potential diagnostic and prognostic biomarker for effective management of this disease.
    Full-text · Article · Jun 2013 · Molecular Cancer
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