Bax has recently been reported [180]. Other studies, however, have found no impact of BH4 deletion on binding of Bcl-2 to Bax, Bak, Bad, Bik or Bim [177]. Accordingly, further work is required to clarify the function of the Bcl-2 BH4 domain and assess the impact of FLassociated Shikonin web mutations in this region.ML240 price Author Manuscript Author Manuscript Author Manuscript Author ManuscriptBiochim Biophys Acta. Author manuscript; available in PMC 2016 July 01.Correia et al.PageComparison of sequential FL biopsies revealed a 4-fold increase in frequency of overtly detectable BCL2 mutations at transformation compared to the same patients at diagnosis [175], suggesting that mutagenesis is ongoing in FL during the course of disease. Mutations identified at transformation had a lower frequency of classical AID signatures, possibly reflecting AID-induced mutation of cytidines outside the context of preferred AID target sequences [181]. Moreover, some of these mutations were clearly nonfunctional, e.g., a BCL2 variant with a premature stop codon [175], again emphasizing that not all BCL2 mutations enhance Bcl-2 function. In accord with studies showing that FL transformation is genetically complex and heterogeneous [166, 169?71], BCL2 mutations can suffer several fates during the course of FL. In cases where there is a linear evolution from an original malignant clone, BCL2 mutations would be maintained throughout the course of the disease, perhaps with the acquisition of additional alterations in the same mutant gene over time. In cases where clones that give rise to the indolent FL and tFL follow divergent paths from a common precursor, mutations present in the dominant clone at diagnosis might not predominate at transformation, where new genetic alterations that confer a stronger proliferation or survival advantage could instead emerge. Conversely, in clones that lack BCL2 mutations initially, BCL2 mutations might emerge at transformation, as reported in our cohort [175]. Whether these are driver or passenger mutations remains to be determined. In comparing recent studies of BCL2 mutations in FL [169?71, 175], several important methodological differences must be kept in mind. First, most of the studies were designed to identify all mutations in the BCL2 locus. These studies not only sequenced the BCL2 promoter and extensive intronic regions in addition to exons, but also counted BCL2 as mutated even when a relatively small percentage of the reads were variant, e.g., as few as three reads out of 85 [169]. In contrast, our recent study, which involved Sanger sequencing of the protein coding exons, was designed to identify mutations that are i) present in predominant clones and ii) capable of altering Bcl-2 protein sequence and function [175]. Second, the studies comprehensively examining genomic changes in FL at transformation relied on the availability of paired FL pathological samples. In contrast, in order to assess the relationship between FL mutations, AID expression and clinical outcome, our recent study relied on a prospectively maintained clinical database and relatively uniform treatment practices at a single institution [175]. To have enough events for survival analysis, however, the vast majority of samples in our study predated the introduction of the anti-CD20 antibody rituximab into clinical FL treatment [182]. Retrospective analyses from the prerituximab era have reported a median survival of only 1? years after FL transformation [167, 168], whe.Bax has recently been reported [180]. Other studies, however, have found no impact of BH4 deletion on binding of Bcl-2 to Bax, Bak, Bad, Bik or Bim [177]. Accordingly, further work is required to clarify the function of the Bcl-2 BH4 domain and assess the impact of FLassociated mutations in this region.Author Manuscript Author Manuscript Author Manuscript Author ManuscriptBiochim Biophys Acta. Author manuscript; available in PMC 2016 July 01.Correia et al.PageComparison of sequential FL biopsies revealed a 4-fold increase in frequency of overtly detectable BCL2 mutations at transformation compared to the same patients at diagnosis [175], suggesting that mutagenesis is ongoing in FL during the course of disease. Mutations identified at transformation had a lower frequency of classical AID signatures, possibly reflecting AID-induced mutation of cytidines outside the context of preferred AID target sequences [181]. Moreover, some of these mutations were clearly nonfunctional, e.g., a BCL2 variant with a premature stop codon [175], again emphasizing that not all BCL2 mutations enhance Bcl-2 function. In accord with studies showing that FL transformation is genetically complex and heterogeneous [166, 169?71], BCL2 mutations can suffer several fates during the course of FL. In cases where there is a linear evolution from an original malignant clone, BCL2 mutations would be maintained throughout the course of the disease, perhaps with the acquisition of additional alterations in the same mutant gene over time. In cases where clones that give rise to the indolent FL and tFL follow divergent paths from a common precursor, mutations present in the dominant clone at diagnosis might not predominate at transformation, where new genetic alterations that confer a stronger proliferation or survival advantage could instead emerge. Conversely, in clones that lack BCL2 mutations initially, BCL2 mutations might emerge at transformation, as reported in our cohort [175]. Whether these are driver or passenger mutations remains to be determined. In comparing recent studies of BCL2 mutations in FL [169?71, 175], several important methodological differences must be kept in mind. First, most of the studies were designed to identify all mutations in the BCL2 locus. These studies not only sequenced the BCL2 promoter and extensive intronic regions in addition to exons, but also counted BCL2 as mutated even when a relatively small percentage of the reads were variant, e.g., as few as three reads out of 85 [169]. In contrast, our recent study, which involved Sanger sequencing of the protein coding exons, was designed to identify mutations that are i) present in predominant clones and ii) capable of altering Bcl-2 protein sequence and function [175]. Second, the studies comprehensively examining genomic changes in FL at transformation relied on the availability of paired FL pathological samples. In contrast, in order to assess the relationship between FL mutations, AID expression and clinical outcome, our recent study relied on a prospectively maintained clinical database and relatively uniform treatment practices at a single institution [175]. To have enough events for survival analysis, however, the vast majority of samples in our study predated the introduction of the anti-CD20 antibody rituximab into clinical FL treatment [182]. Retrospective analyses from the prerituximab era have reported a median survival of only 1? years after FL transformation [167, 168], whe.
