Hodgkin’s lymphoma (NHL) [212, 213]. With the development of ABT-199, studies of navitoclax continue in solid tumors, where it is being used to target Bcl-xL, whereas studies in Bcl-2-dependent hematological malignancies have focused more extensively on ABT-199.Biochim Biophys Acta. Author manuscript; available in PMC 2016 July 01.Correia et al.PageAs of January 2015, 16 clinical trials testing ABT-199 either as a single agent or in combination therapy (www.clinicaltrials.gov) are ongoing. A variety of neoplasms are being studied, including CLL, aggressive NHL, FL, multiple myeloma (MM) and AML (Table 3). In preclinical studies, anti-tumor activity of ABT-199 has also been reported in T-cell ALL, chronic myelogenous leukemia, colorectal and breast cancers [214?17]. Early clinical results suggest that ABT-199 has promising activity in relapsed or refractory (R/R) lymphoid malignancies. In particular, ABT-199 has an overall response rate (ORR) of 56 in R/R NHL [218] and 84 (20 complete response) in R/R CLL and small lymphocytic leukemia (SLL) [219]. Indeed, responses in CLL and SLL have been so risk that tumor lysis syndrome has been a major complication of therapy. In contrast, despite tantalizing activity against AML cells ex vivo [91], ABT-199 has shown disappointing activity (12.5 complete remission rate) in R/R AML [92], perhaps because of elevated Mcl-1 in this setting [120]. Additional studies are investigating ABT-199 in combination with other therapies (Table 3). For example, Roberts et al. reported an 86 OR (31 CR) in R/R CLL treated with ABT-199 and the anti-CD20 antibody rituximab [220]. Other studies in R/R or untreated CLL patients combined ABT-199 with Obinutuzumab, a glycoengineered anti-CD20 antibody [221], or in CLL and NHL with Bendamustine/Rituximab [222, 223]. More mature reports of these promising investigations are awaited with interest.Author Manuscript Author Manuscript Author Manuscript Author Manuscript5.0. An agenda for the futureDespite improvements in understanding signaling through the intrinsic apoptotic pathway over the past 2? years, purchase Abamectin B1a important questions remain. Recent studies have clarified how BH3only proteins induce Bax or Bak activation and provided detailed descriptions of Bax and Bak homodimers, but these results provide limited insight into the mechanism by which Bax and Bak breach the MOM. Further studies of higher order Bax and Bak oligomers, perhaps in the presence of appropriate lipids, are required for progress in this area. Even though the Bcl-2 protein was identified almost 30 years ago, important questions about its structure and function persist. How phosphorylations in the FLD affect ML240 site affinity of the BH3 binding groove for its ligands is entirely unclear. While recent studies suggest that changes in the FLD can affect Bcl-2 conformation [54], an NMR or crystal structure of Bcl-2 with its own loop intact is required to better understand this aspect of Bcl-2 regulation. The consequences of nonsynonymous BCL2 mutations also require further investigation. While these mutations become more prevalent during the course of FL [175], it is unclear whether they are driving FL transformation or are merely bystanders that reflect high AID activity in FLs at highest risk of transformation. Further study is also required to determine which BCL2 mutations affect Bcl-2 protein function and how these amino acid changes, whether in the FLD or elsewhere, alter affinity of the BH3 binding groove. Finally.Hodgkin’s lymphoma (NHL) [212, 213]. With the development of ABT-199, studies of navitoclax continue in solid tumors, where it is being used to target Bcl-xL, whereas studies in Bcl-2-dependent hematological malignancies have focused more extensively on ABT-199.Biochim Biophys Acta. Author manuscript; available in PMC 2016 July 01.Correia et al.PageAs of January 2015, 16 clinical trials testing ABT-199 either as a single agent or in combination therapy (www.clinicaltrials.gov) are ongoing. A variety of neoplasms are being studied, including CLL, aggressive NHL, FL, multiple myeloma (MM) and AML (Table 3). In preclinical studies, anti-tumor activity of ABT-199 has also been reported in T-cell ALL, chronic myelogenous leukemia, colorectal and breast cancers [214?17]. Early clinical results suggest that ABT-199 has promising activity in relapsed or refractory (R/R) lymphoid malignancies. In particular, ABT-199 has an overall response rate (ORR) of 56 in R/R NHL [218] and 84 (20 complete response) in R/R CLL and small lymphocytic leukemia (SLL) [219]. Indeed, responses in CLL and SLL have been so risk that tumor lysis syndrome has been a major complication of therapy. In contrast, despite tantalizing activity against AML cells ex vivo [91], ABT-199 has shown disappointing activity (12.5 complete remission rate) in R/R AML [92], perhaps because of elevated Mcl-1 in this setting [120]. Additional studies are investigating ABT-199 in combination with other therapies (Table 3). For example, Roberts et al. reported an 86 OR (31 CR) in R/R CLL treated with ABT-199 and the anti-CD20 antibody rituximab [220]. Other studies in R/R or untreated CLL patients combined ABT-199 with Obinutuzumab, a glycoengineered anti-CD20 antibody [221], or in CLL and NHL with Bendamustine/Rituximab [222, 223]. More mature reports of these promising investigations are awaited with interest.Author Manuscript Author Manuscript Author Manuscript Author Manuscript5.0. An agenda for the futureDespite improvements in understanding signaling through the intrinsic apoptotic pathway over the past 2? years, important questions remain. Recent studies have clarified how BH3only proteins induce Bax or Bak activation and provided detailed descriptions of Bax and Bak homodimers, but these results provide limited insight into the mechanism by which Bax and Bak breach the MOM. Further studies of higher order Bax and Bak oligomers, perhaps in the presence of appropriate lipids, are required for progress in this area. Even though the Bcl-2 protein was identified almost 30 years ago, important questions about its structure and function persist. How phosphorylations in the FLD affect affinity of the BH3 binding groove for its ligands is entirely unclear. While recent studies suggest that changes in the FLD can affect Bcl-2 conformation [54], an NMR or crystal structure of Bcl-2 with its own loop intact is required to better understand this aspect of Bcl-2 regulation. The consequences of nonsynonymous BCL2 mutations also require further investigation. While these mutations become more prevalent during the course of FL [175], it is unclear whether they are driving FL transformation or are merely bystanders that reflect high AID activity in FLs at highest risk of transformation. Further study is also required to determine which BCL2 mutations affect Bcl-2 protein function and how these amino acid changes, whether in the FLD or elsewhere, alter affinity of the BH3 binding groove. Finally.
