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A role for eukaryotic initiation factor 4B overexpression in the pathogenesis of diffuse large B-cell lymphoma.

Horvilleur E, Sbarrato T, Hill K, Spriggs RV, Screen M, Goodrem PJ, Sawicka K, Chaplin LC, Touriol C, Packham G, Potter KN, Dirnhofer S, Tzankov A, Dyer MJ, Bushell M, MacFarlane M, Willis AE - Leukemia (2013)

Bottom Line: This process is driven by signaling through mammalian target of rapamycin, resulting in increased synthesis of eukaryotic initiation factor (eIF) 4B complex (eIF4B), a known activator of the RNA helicase eIF4A.Reducing eIF4B expression alone is sufficient to decrease synthesis of proteins associated with enhanced tumor cell survival, namely DAXX, BCL2 and ERCC5.Our work provides new insights into the mechanisms by which the cancer-promoting translational machinery drives lymphomagenesis.

View Article: PubMed Central - PubMed

Affiliation: Medical Research Council Toxicology Unit, Leicester, UK.

ABSTRACT
Dysregulated expression of factors that control protein synthesis is associated with poor prognosis of many cancers, but the underlying mechanisms are not well defined. Analysis of the diffuse large B-cell lymphoma (DLBCL) translatome revealed selective upregulation of mRNAs encoding anti-apoptotic and DNA repair proteins. We show that enhanced synthesis of these proteins in DLBCL is mediated by the relief of repression that is normally imposed by structure in the 5'-untranslated regions of their corresponding mRNAs. This process is driven by signaling through mammalian target of rapamycin, resulting in increased synthesis of eukaryotic initiation factor (eIF) 4B complex (eIF4B), a known activator of the RNA helicase eIF4A. Reducing eIF4B expression alone is sufficient to decrease synthesis of proteins associated with enhanced tumor cell survival, namely DAXX, BCL2 and ERCC5. Importantly, eIF4B-driven expression of these key survival proteins is directly correlated with patient outcome, and eIF4B, DAXX and ERCC5 are identified as novel prognostic markers for poor survival in DLBCL. Our work provides new insights into the mechanisms by which the cancer-promoting translational machinery drives lymphomagenesis.

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Tissue microarray shows that altered expression of the proteins identified by translational profiling in tumors from patients with B-cell lymphoma corresponds with survival. (a) Tissue microarrays that contained tissues from 362 lymphomas, including 196 DLBCL, 76 FL and 52 chronic lymphocytic leukemias (CLLs) were probed with antibodies against ERCC5 (i) and DAXX (ii), and scored as described in the experimental procedures section. The graphs represent percentage of tumors from each type expressing high levels of the scored protein. The data show that there are differences in expression of DAXX in the DLBCL patient samples compared with the other tumor types, and for ERCC5 a difference in the expression in FL and DLBCL when compared with CLL. Significance between the different categories was assessed by χ2-test (*P<0.05, **P<0.01, ***P<0.001). (b) Patients were separated into groups that have low or high expression of ERCC5 (i) or DAXX (ii), or eIF4B (iii). Survival curves were generated using Kaplan–Meier approximation to compare overall survival in different groups of patients. The significance of the changes in survival was assessed using log-rank P-value. The data show that there are significant decreases in survival in patients that have high expression for ERCC5 (P=0.044), DAXX (P=0.003) and eIF4B (P=0.0081).
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fig6: Tissue microarray shows that altered expression of the proteins identified by translational profiling in tumors from patients with B-cell lymphoma corresponds with survival. (a) Tissue microarrays that contained tissues from 362 lymphomas, including 196 DLBCL, 76 FL and 52 chronic lymphocytic leukemias (CLLs) were probed with antibodies against ERCC5 (i) and DAXX (ii), and scored as described in the experimental procedures section. The graphs represent percentage of tumors from each type expressing high levels of the scored protein. The data show that there are differences in expression of DAXX in the DLBCL patient samples compared with the other tumor types, and for ERCC5 a difference in the expression in FL and DLBCL when compared with CLL. Significance between the different categories was assessed by χ2-test (*P<0.05, **P<0.01, ***P<0.001). (b) Patients were separated into groups that have low or high expression of ERCC5 (i) or DAXX (ii), or eIF4B (iii). Survival curves were generated using Kaplan–Meier approximation to compare overall survival in different groups of patients. The significance of the changes in survival was assessed using log-rank P-value. The data show that there are significant decreases in survival in patients that have high expression for ERCC5 (P=0.044), DAXX (P=0.003) and eIF4B (P=0.0081).

Mentions: It was then important to assess whether the differences in protein expression were also present in patients with DLBCL and whether this was associated with patient survival. It is well established that BCL2 is upregulated in different non-Hodgkin lymphoma types,39, 40, 41 and its elevated expression is associated with poor prognosis in DLBCL;41 hence, the role of this protein in patient survival was not examined further. However, DAXX and ERCC5 expression have not been studied previously in DLBCL in this regard. Therefore, to determine the expression of DAXX and ERCC5 in a large number of patient samples simultaneously, tissue microarrays were used (Supplementary Figure 6, Supplementary Table 4). ERCC5 expression was significantly higher in DLBCL when compared with that in chronic lymphocytic leukemia (Figure 6a(i)). DAXX protein expression in DLBCL was increased significantly when compared with that in FL and chronic lymphocytic leukemia (Figure 6a(ii)). Kaplan–Meier analysis was performed to determine whether there were differences in survival associated with the increased expression of DAXX, ERCC5 and eIF4B (Figures 6b(i–iii)). Importantly, the data show that high DAXX, ERCC5 and eIF4B expression correlated with poor overall survival for all subtypes of DLBCL, providing three new prognostic markers that would identify those with worse outcome for this disease (Figures 6b(i–iii)).


A role for eukaryotic initiation factor 4B overexpression in the pathogenesis of diffuse large B-cell lymphoma.

Horvilleur E, Sbarrato T, Hill K, Spriggs RV, Screen M, Goodrem PJ, Sawicka K, Chaplin LC, Touriol C, Packham G, Potter KN, Dirnhofer S, Tzankov A, Dyer MJ, Bushell M, MacFarlane M, Willis AE - Leukemia (2013)

Tissue microarray shows that altered expression of the proteins identified by translational profiling in tumors from patients with B-cell lymphoma corresponds with survival. (a) Tissue microarrays that contained tissues from 362 lymphomas, including 196 DLBCL, 76 FL and 52 chronic lymphocytic leukemias (CLLs) were probed with antibodies against ERCC5 (i) and DAXX (ii), and scored as described in the experimental procedures section. The graphs represent percentage of tumors from each type expressing high levels of the scored protein. The data show that there are differences in expression of DAXX in the DLBCL patient samples compared with the other tumor types, and for ERCC5 a difference in the expression in FL and DLBCL when compared with CLL. Significance between the different categories was assessed by χ2-test (*P<0.05, **P<0.01, ***P<0.001). (b) Patients were separated into groups that have low or high expression of ERCC5 (i) or DAXX (ii), or eIF4B (iii). Survival curves were generated using Kaplan–Meier approximation to compare overall survival in different groups of patients. The significance of the changes in survival was assessed using log-rank P-value. The data show that there are significant decreases in survival in patients that have high expression for ERCC5 (P=0.044), DAXX (P=0.003) and eIF4B (P=0.0081).
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4017261&req=5

fig6: Tissue microarray shows that altered expression of the proteins identified by translational profiling in tumors from patients with B-cell lymphoma corresponds with survival. (a) Tissue microarrays that contained tissues from 362 lymphomas, including 196 DLBCL, 76 FL and 52 chronic lymphocytic leukemias (CLLs) were probed with antibodies against ERCC5 (i) and DAXX (ii), and scored as described in the experimental procedures section. The graphs represent percentage of tumors from each type expressing high levels of the scored protein. The data show that there are differences in expression of DAXX in the DLBCL patient samples compared with the other tumor types, and for ERCC5 a difference in the expression in FL and DLBCL when compared with CLL. Significance between the different categories was assessed by χ2-test (*P<0.05, **P<0.01, ***P<0.001). (b) Patients were separated into groups that have low or high expression of ERCC5 (i) or DAXX (ii), or eIF4B (iii). Survival curves were generated using Kaplan–Meier approximation to compare overall survival in different groups of patients. The significance of the changes in survival was assessed using log-rank P-value. The data show that there are significant decreases in survival in patients that have high expression for ERCC5 (P=0.044), DAXX (P=0.003) and eIF4B (P=0.0081).
Mentions: It was then important to assess whether the differences in protein expression were also present in patients with DLBCL and whether this was associated with patient survival. It is well established that BCL2 is upregulated in different non-Hodgkin lymphoma types,39, 40, 41 and its elevated expression is associated with poor prognosis in DLBCL;41 hence, the role of this protein in patient survival was not examined further. However, DAXX and ERCC5 expression have not been studied previously in DLBCL in this regard. Therefore, to determine the expression of DAXX and ERCC5 in a large number of patient samples simultaneously, tissue microarrays were used (Supplementary Figure 6, Supplementary Table 4). ERCC5 expression was significantly higher in DLBCL when compared with that in chronic lymphocytic leukemia (Figure 6a(i)). DAXX protein expression in DLBCL was increased significantly when compared with that in FL and chronic lymphocytic leukemia (Figure 6a(ii)). Kaplan–Meier analysis was performed to determine whether there were differences in survival associated with the increased expression of DAXX, ERCC5 and eIF4B (Figures 6b(i–iii)). Importantly, the data show that high DAXX, ERCC5 and eIF4B expression correlated with poor overall survival for all subtypes of DLBCL, providing three new prognostic markers that would identify those with worse outcome for this disease (Figures 6b(i–iii)).

Bottom Line: This process is driven by signaling through mammalian target of rapamycin, resulting in increased synthesis of eukaryotic initiation factor (eIF) 4B complex (eIF4B), a known activator of the RNA helicase eIF4A.Reducing eIF4B expression alone is sufficient to decrease synthesis of proteins associated with enhanced tumor cell survival, namely DAXX, BCL2 and ERCC5.Our work provides new insights into the mechanisms by which the cancer-promoting translational machinery drives lymphomagenesis.

View Article: PubMed Central - PubMed

Affiliation: Medical Research Council Toxicology Unit, Leicester, UK.

ABSTRACT
Dysregulated expression of factors that control protein synthesis is associated with poor prognosis of many cancers, but the underlying mechanisms are not well defined. Analysis of the diffuse large B-cell lymphoma (DLBCL) translatome revealed selective upregulation of mRNAs encoding anti-apoptotic and DNA repair proteins. We show that enhanced synthesis of these proteins in DLBCL is mediated by the relief of repression that is normally imposed by structure in the 5'-untranslated regions of their corresponding mRNAs. This process is driven by signaling through mammalian target of rapamycin, resulting in increased synthesis of eukaryotic initiation factor (eIF) 4B complex (eIF4B), a known activator of the RNA helicase eIF4A. Reducing eIF4B expression alone is sufficient to decrease synthesis of proteins associated with enhanced tumor cell survival, namely DAXX, BCL2 and ERCC5. Importantly, eIF4B-driven expression of these key survival proteins is directly correlated with patient outcome, and eIF4B, DAXX and ERCC5 are identified as novel prognostic markers for poor survival in DLBCL. Our work provides new insights into the mechanisms by which the cancer-promoting translational machinery drives lymphomagenesis.

Show MeSH
Related in: MedlinePlus