Therapeutic targeting of Bcl-2 family for treatment of B-cell malignancies

Discovery of a Covalent Inhibitor That Overcame Resistance to Venetoclax in AML Cells Overexpressing BFL-1

Clinical and biological studies have shown that overexpression of BFL-1 is one contributing factor to venetoclax resistance. The resistance might be overcome by a potent BFL-1 inhibitor, but such an inhibitor is rare. In this study, we show that 56, featuring an acrylamide moiety, inhibited the BFL-1/BID interaction with a Ki value of 105 nM. More interestingly, 56 formed an irreversible conjugation adduct at the C55 residue of BFL-1. 56 was a selective BFL-1 inhibitor, and its MCL-1 binding affinity was 10-fold weaker, while it did not bind BCL-2 and BCL-xL. Mechanistic studies showed that 56 overcame venetoclax resistance in isogenic AML cell lines MOLM-13-OE and MV4-11-OE, which both overexpressed BFL-1. More importantly, 56 and venetoclax combination promoted stronger apoptosis induction than either single agent. Collectively, our data show that 56 overcame resistance to venetoclax in AML cells overexpressing BFL-1. These attributes make 56 a promising candidate for future optimization.

Long non-coding RNA small nucleolar RNA host gene 29 drives chronic myeloid leukemia progression via microRNA-483-3p/Casitas B-lineage Lymphoma axis-mediated activation of the phosphoinositide 3-kinase/Akt pathway

The aberrant expression of the long non-coding RNA (lncRNA) Small Nucleolar RNA Host Gene 29 (SNHG29) has been associated with various human cancers. However, the role of SNHG29 in chronic myeloid leukemia (CML) remains elusive. Therefore, this study aimed to investigate the function of SNHG29 in CML and unveil its potential underlying mechanisms. Herein, peripheral blood samples from 44 CML patients and 17 healthy subjects were collected. The expressions of SNHG29, microRNA-483-3p (miR-483-3p), and Casitas B-lineage Lymphoma (CBL) were measured using quantitative polymerase chain reaction (qPCR) or Western Blot. Cell viability, apoptosis, and cell cycle progression were evaluated using the Cell Counting Kit-8 assay, 5-ethynyl-2'-deoxyuridine incorporation, and flow cytometry, respectively. Western Blot analysis was employed to assess protein expressions related to cellular proliferation, apoptosis, and oncogenesis. RNA immunoprecipitation and dual-luciferase reporter assays were utilized to verify the interactions among SNHG29, miR-483-3p, and CBL. SNHG29 was significantly overexpressed in both blood samples of CML patients and CML cell lines. In CML, increased expression of SNHG29 was positively correlated with clinical staging, and patients with high SNHG29 expression had poorer survival outcomes. Functionally, knocking down SNHG29 effectively inhibited CML cell proliferation and promoted apoptosis. Mechanistically, SNHG29 acted as a competing endogenous RNA for miR-483-3p to modulate CBL expression, thereby activating the Phosphoinositide 3-Kinase/Akt signaling pathway and mediating CML progression. In summary, these findings reveal that SNHG29 promotes tumorigenesis in CML, offering a potential therapeutic strategy for CML treatment.

Potential Biomarkers for Treatment Response to the BCL-2 Inhibitor Venetoclax: State of the Art and Future Directions

Intrinsic apoptotic pathway dysregulation plays an essential role in all cancers, particularly hematologic malignancies. This role has led to the development of multiple therapeutic agents targeting this pathway. Venetoclax is a selective BCL-2 inhibitor that has been approved for the treatment of chronic lymphoid leukemia and acute myeloid leukemia. Given the reported resistance to venetoclax, understanding the mechanisms of resistance and the potential biomarkers of response is crucial to ensure optimal drug usage and improved patient outcomes. Mechanisms of resistance to venetoclax include alterations involving the BH3-binding groove, BCL2 gene mutations affecting venetoclax binding, and activation of alternative anti-apoptotic pathways. Moreover, various potential genetic biomarkers of venetoclax resistance have been proposed, including chromosome 17p deletion, trisomy 12, and TP53 loss or mutation. This manuscript provides an overview of biomarkers that could predict treatment response to venetoclax.

Combination strategies to overcome resistance to the BCL2 inhibitor venetoclax in hematologic malignancies

Venetoclax has been approved by the United States Food and Drug Administration since 2016 as a monotherapy for treating patients with relapsed/refractory chronic lymphocytic leukemia having 17p deletion. It has led to a breakthrough in the treatment of hematologic malignancies in recent years. However, unfortunately, resistance to venetoclax is inevitable. Multiple studies confirmed that the upregulation of the anti-apoptotic proteins of the B-cell lymphoma 2 (BCL2) family mediated by various mechanisms, such as tumor microenvironment, and the activation of intracellular signaling pathways were the major factors leading to resistance to venetoclax. Therefore, only targeting BCL2 often fails to achieve the expected therapeutic effect. Based on the mechanism of resistance in specific hematologic malignancies, the combination of specific drugs with venetoclax was a clinically optional treatment strategy for overcoming resistance to venetoclax. This study aimed to summarize the possible resistance mechanisms of various hematologic tumors to venetoclax and the corresponding clinical strategies to overcome resistance to venetoclax in hematologic malignancies.

Antiapoptotic Proteins mcl-1 and bcl-2 as well as Growth Factors FGF and VEGF Influence Survival of Peripheral Blood and Bone Marrow Chronic Lymphocytic Leukemia Cells

Apoptosis inhibition in chronic lymphocytic leukemia (CLL) is one of the most important mechanism in the disease onset, progression and therapy response and is dependent of interaction with different microenvironments.

Aim of our paper is to determine expression of antiapoptoic proteins mcl-1 and bcl-2 in CLL cells isolated from two different compartments (peripheral blood and bone marrow) and its relation to percent of apoptotic cells and concentration of growth factors (FGF and VEGF).

Our results showed that peripheral blood CLL lymphocytes have lower apoptotic rate then those isolated from bone marrow, though bone marrow CLL lymphocytes express higher levels of antipoptotic proteins bcl-2 and mcl-1. In bone marrow FGF concentration is 10-fold higher then in patients plasma but has an limited impact on mcl-1 expression. In contrary, VEGF concentration is higher in peripheral blood and corelate with percent of apoptotic cells and mcl-1 expression in this compartment.

CLL cells derived from two different microenvironmets acts differently when tested for apoptosis „ex vivo“. In peripheral blood apoptosis is strongly connected with expression of antiapoptoic proteins (mcl-1 and bcl-2) and growth factors, but not in bone marrow.

Involvement of CHOP in activin A‑induced myeloma NS‑1 cell apoptosis

Activin A, a multifunctional cytokine, is a member of transforming growth factor-β (TGF-β) superfamily. It is associated with a variety of pathophysiological processes, including inflammation, fibrosis, and tumorigenesis. Chronic or prolonged endoplasmic reticulum (ER) stress can lead to cells apoptosis. However, whether ER stress-related proteins, such as CHOP, GADD34 are involved in activin A-induced myeloma cell apoptosis remains unknown. In the present study, it was revealed that activin A inhibited the proliferation of myeloma cell line NS-1 cells and induced NS-1 cell apoptosis. Activin A upregulated the expression of CHOP, GADD34, caspase-3, and caspase-12. Moreover, both Smad3 and p-Smad3 levels were increased with treatment of activin A. Further studies revealed that the overexpression of activin signaling protein Smad3 in NS-1 cells increased the levels of CHOP, caspase-3, and p-Smad3. These data indicated that the CHOP protein of the ER stress pathway may be involved in activin A-induced NS-1 cell apoptosis, and also indicated the potential therapy of activin A-induced apoptosis via CHOP signaling for multiple myeloma.

Targeting BCL2 in Chronic Lymphocytic Leukemia and Other Hematologic Malignancies

Apoptosis, the process of programmed cell death, occurs normally during development and aging. Members of the B-cell lymphoma 2 (BCL2) family of proteins are central regulators of apoptosis, and resistance to apoptosis is one of the hallmarks of cancer. Targeting the apoptotic pathway via BCL2 inhibitors has been considered a promising treatment strategy in the past decade. Initial efforts with small molecule BH3 mimetics such as ABT-737 and ABT-263 (navitoclax) pioneered the development of the first-in-class Food and Drug Administration (FDA)-approved oral BCL2 inhibitor, venetoclax. Venetoclax was approved for the treatment of chronic lymphocytic leukemia and acute myeloid leukemia, and is now being studied in a number of hematologic malignancies. Several other inhibitors targeting different BCL2 family members are now in early stages of development.

Challenges and Opportunities from Basic Cancer Biology for Nanomedicine for Targeted Drug Delivery

Background:

Effective cancer therapy is still a great challenge for modern medical research due to the complex underlying mechanisms of tumorigenesis and tumor metastasis, and the limitations commonly associated with currently used cancer therapeutic options. Nanotechnology has been implemented in cancer therapeutics with immense potential for improving cancer treatment.

Objective:

Through information about the recent advances regarding cancer hallmarks, we could comprehensively understand the pharmacological effects and explore the mechanisms of the interaction between the nanomaterials, which could provide opportunities to develop mechanism-based nanomedicine to treat human cancers.

Methods:

We collected related information and data from articles.

Results:

In this review, we discussed the characteristics of cancer including tumor angiogenesis, abnormalities in tumor blood vessels, uncontrolled cell proliferation markers, multidrug resistance, tumor metastasis, cancer cell metabolism, and tumor immune system that provide opportunities and challenges for nanomedicine to be directed to specific cancer cells and portray the progress that has been accomplished in application of nanotechnology for cancer treatment.

Conclusion:

The information presented in this review can provide useful references for further studies on developing effective nanomedicine for the treatment of cancer.

Dysregulated TRAF3 and BCL2 Expression Promotes Multiple Classes of Mature Non-hodgkin B Cell Lymphoma in Mice

TNF-Receptor Associated Factor (TRAF)-3 is a master regulator of B cell homeostasis and function. TRAF3 has been shown to bind and regulate various proteins involved in the control of innate and adaptive immune responses. Previous studies showed that TRAF3 overexpression renders B cells hyper-reactive to antigens and Toll-like receptor (TLR) agonists, while TRAF3 deficiency has been implicated in the development of a variety of B cell neoplasms. In this report, we show that transgenic mice overexpressing TRAF3 and BCL2 in B cells develop with high incidence severe lymphadenopathy, splenomegaly and lymphoid infiltrations into tissues and organs, which is the result of the growth of monoclonal and oligoclonal B cell neoplasms, as demonstrated by analysis of V_HDJ_H gene rearrangement. FACS and immunohistochemical analyses show that different types of mature B cell neoplasms arise in TRAF3/BCL2 double-transgenic (tg) mice, all of which are characterized by the loss of surface IgM and IgD expression. However, two types of lymphomas are predominant: (1) mature B cell neoplasms consistent with diffuse large B cell lymphoma and (2) plasma cell neoplasms. The Ig isotypes expressed by the expanded B-cell clones included IgA, IgG, and IgM, with most having undergone somatic hypermutation. In contrast, mouse littermates representing all the other genotypes (TRAF3-/BCL2-; TRAF3+/BCL2-, and TRAF3-/BCL2+) did not develop significant lymphadenopathy or clonal B cell expansions within the observation period of 20 months. Interestingly, a large representation of the HCDR3 sequences expressed in the TRAF3-tg and TRAF3/BCL2-double-tg B cells are highly similar to those recognizing pathogen-associated molecular patterns and damage-associated molecular patterns, strongly suggesting a role for TRAF3 in promoting B cell differentiation in response to these antigens. Finally, allotransplantation of either splenocytes or cell-containing ascites from lymphoma-bearing TRAF3/BCL2 mice into SCID/NOD immunodeficient mice showed efficient transfer of the parental expanded B-cell clones. Altogether, these results indicate that TRAF3, perhaps by promoting exacerbated B cell responses to certain antigens, and BCL2, presumably by supporting survival of these clones, cooperate to induce mature B cell neoplasms in transgenic mice.

BCL2-Family Dysregulation in B-Cell Malignancies: From Gene Expression Regulation to a Targeted Therapy Biomarker

BCL2-family proteins have a central role in the mitochondrial apoptosis machinery and their expression is known to be deregulated in many cancer types. Effort in the development of small molecules that selectively target anti-apoptotic members of this family i.e., Bcl-2, Bcl-xL, Mcl-1 recently opened novel therapeutic opportunities. Among these apoptosis-inducing agents, BH3-mimetics (i.e., venetoclax) led to promising preclinical and clinical activity in B cell malignancies. However, several mechanisms of intrinsic or acquired resistance have been described ex vivo therefore predictive markers of response as well as mechanism-based combinations have to be designed. In the present study, we analyzed the expression of the BCL2-family genes across 10 mature B cell malignancies through computational normalization of 21 publicly available Affimetrix datasets gathering 1,219 patient samples. To better understand the deregulation of anti- and pro-apoptotic members of the BCL2-family in hematological disorders, we first compared gene expression profiles of malignant B cells to their relative normal control (naïve B cell to plasma cells, n = 37). We further assessed BCL2-family expression according to tissue localization i.e., peripheral blood, bone marrow, and lymph node, molecular subgroups or disease status i.e., indolent to aggressive. Across all cancer types, we showed that anti-apoptotic genes are upregulated while pro-apoptotic genes are downregulated when compared to normal counterpart cells. Of interest, our analysis highlighted that, independently of the nature of malignant B cells, the pro-apoptotic BH3-only BCL2L11 and PMAIP1 are deeply repressed in tumor niches, suggesting a central role of the microenvironment in their regulation. In addition, we showed selective modulations across molecular subgroups and showed that the BCL2-family expression profile was related to tumor aggressiveness. Finally, by integrating recent data on venetoclax-monotherapy clinical activity with the expression of BCL2-family members involved in the venetoclax response, we determined that the ratio (BCL2+BCL2L11+BAX)/BCL2L1 was the strongest predictor of venetoclax response for mature B cell malignancies in vivo.

TRIM22 knockdown suppresses chronic myeloid leukemia via inhibiting PI3K/Akt/mTOR signaling pathway

Tripartite motif-containing 22 (TRIM22) is reported to participate in numerous cellular activities. Recent studies confirm that TRIM22 is a target gene for P53, and inhibits clonogenic growth of leukemic U-937 cells. The current study aims to discover the effect of TRIM22 in progression of human chronic myeloid leukemia (CML) and explore the related mechanism. TRIM22 was knocked down by siRNA transfection in CML cell K562. We observed that TRIM22 knockdown decreased proliferation and invasion in K562 cells. TRIM22 knockdown significantly induced cell cycle arrest by regulating the level of CDK4, Cyclin D1, P70S6K, and P53 in K562 cell. Moreover, loss of TRIM22 also promoted apoptosis through modulation of Bcl-2, Bax and active Caspase 3 in K562 cell. Furthermore, we demonstrated that TRIM22 knockdown inhibited the activation of PI3K/Akt/mTOR pathway by decreasing the level of the phosphorylated form p-Akt and p-mTOR in K562 cell. In conclusion, loss of TRIM22 suppresses the progression and invasion of CML through regulation of PI3K/Akt/mTOR pathway, suggesting that TRIM22 might be as a potential target for the treatment strategy of CML.

BCL-2 as therapeutic target for hematological malignancies

Disruption of the physiologic balance between cell proliferation and cell death is an important step of cancer development. Increased resistance to apoptosis is a key oncogenic mechanism in several hematological malignancies and, in many cases, especially in lymphoid neoplasias, has been attributed to the upregulation of BCL-2. The BCL-2 protein is the founding member of the BCL-2 family of apoptosis regulators and was the first apoptosis modulator to be associated with cancer. The recognition of the important role played by BCL-2 for cancer development and resistance to treatment made it a relevant target for therapy for many diseases, including solid tumors and hematological neoplasias. Among the different strategies that have been developed to inhibit BCL-2, BH3-mimetics have emerged as a novel class of compounds with favorable results in different clinical settings, including chronic lymphocytic leukemia (CLL). In April 2016, the first inhibitor of BCL-2, venetoclax, was approved by the US Food and Drug Administration for the treatment of patients with CLL who have 17p deletion and had received at least one prior therapy. This review focuses on the relevance of BCL-2 for apoptosis modulation at the mitochondrial level, its potential as therapeutic target for hematological malignancies, and the results obtained with selective inhibitors belonging to the BH3-mimetics, especially venetoclax used in monotherapy or in combination with other agents.

Found in Translation: How Preclinical Research Is Guiding the Clinical Development of the BCL2-Selective Inhibitor Venetoclax

Since the discovery of apoptosis as a form of programmed cell death, targeting the apoptosis pathway to induce cancer cell death has been a high-priority goal for cancer therapy. After decades of effort, drug-discovery scientists have succeeded in generating small-molecule inhibitors of antiapoptotic BCL2 family proteins. Innovative medicinal chemistry and structure-based drug design, coupled with a strong fundamental understanding of BCL2 biology, were essential to the development of BH3 mimetics such as the BCL2-selective inhibitor venetoclax. We review a number of preclinical studies that have deepened our understanding of BCL2 biology and facilitated the clinical development of venetoclax.Significance: Basic research into the pathways governing programmed cell death have paved the way for the discovery of apoptosis-inducing agents such as venetoclax, a BCL2-selective inhibitor that was recently approved by the FDA and the European Medicines Agency. Preclinical studies aimed at identifying BCL2-dependent tumor types have translated well into the clinic thus far and will likely continue to inform the clinical development of venetoclax and other BCL2 family inhibitors. Cancer Discov; 7(12); 1376-93. ©2017 AACR.

Long noncoding RNA HULC promotes cell proliferation by regulating PI3K/AKT signaling pathway in chronic myeloid leukemia

Aberrant expression of long noncoding RNA (lncRNA) HULC is associated with various human cancers. However, the role of HULC in chronic myeloid leukemia (CML) is unknown. In this study, we found that HULC was remarkably overexpressed in both leukemia cell lines and primary hematopoietic cells derived from CML patients. The increase in HULC expression was positively correlated with clinical stages in CML. Moreover, the knockdown of HULC significantly inhibited CML cell proliferation and induced apoptosis by repressing c-Myc and Bcl-2. Furthermore, inhibition of HULC enhanced imatinib-induced apoptosis of CML cells. Further experiments demonstrated that HULC silencing markedly suppressed the phosphorylation of PI3K and AKT, indicating that enhancement of imatinib-induced apoptosis by HULC inhibition is related with the reduction of c-Myc expression and inhibition of PI3K/Akt pathway activity. Furthermore, HULC could modulate c-Myc and Bcl-2 by miR-200a as an endogenous sponge. Taken together, these results reveal that HULC promotes oncogenesis in CML and suggest a potential strategy for the CML treatment.

Ethyl acetate extract of Peperomia tetraphylla induces cytotoxicity, cell cycle arrest, and apoptosis in lymphoma U937 cells

The current study evaluated the cytotoxicity and the mechanism of apoptotic induction by Peperomia tetraphylla in U937 lymphoma cells. The results showed that P. tetraphylla ethyl acetate extract (EAEPT) inhibited the cell growth in U937 cells by MTT assay. After the U937 cells were treated with EAEPT, the cells exhibited marked morphological features of apoptosis (Hoechst 33342 staining) and the number of apoptotic cell (Annexin V-FITC/PI staining) increased. The treatment of EAEPT could induce loss of mitochondrial membrane potential (MMP) and increase the ROS level. Moreover, EAEPT treatment resulted in the accumulation of cells at S phase. We found that EAEPT could induce the cleavage of the caspase 3, caspase 8, caspase 9 and Bid. And the treatment of EAEPT could increase expression of Bax and down-regulate the expression of CCNB1, CCND1 and CDK1. The sub-fraction of EAEPT, namely EASub1 demonstrated the highest cytotoxicity activity on U937 cells. It was confirmed that EAEPT could inhibit the growth of U937 cells by blocking the cell cycle and prompted apoptosis via the ROS-medicated mitochondria pathway in vitro.

Orphan Nuclear Receptor NR4A1 Binds a Novel Protein Interaction Site on Anti-apoptotic B Cell Lymphoma Gene 2 Family Proteins

B cell lymphoma gene 2 (Bcl-2) family proteins are key regulators of programmed cell death and important targets for drug discovery. Pro-apoptotic and anti-apoptotic Bcl-2 family proteins reciprocally modulate their activities in large part through protein interactions involving a motif known as BH3 (Bcl-2 homology 3). Nur77 is an orphan member of the nuclear receptor family that lacks a BH3 domain but nevertheless binds certain anti-apoptotic Bcl-2 family proteins (Bcl-2, Bfl-1, and Bcl-B), modulating their effects on apoptosis and autophagy. We used a combination of NMR spectroscopy-based methods, mutagenesis, and functional studies to define the interaction site of a Nur77 peptide on anti-apoptotic Bcl-2 family proteins and reveal a novel interaction surface. Nur77 binds adjacent to the BH3 peptide-binding crevice, suggesting the possibility of cross-talk between these discrete binding sites. Mutagenesis of residues lining the identified interaction site on Bcl-B negated the interaction with Nur77 protein in cells and prevented Nur77-mediated modulation of apoptosis and autophagy. The findings establish a new protein interaction site with the potential to modulate the apoptosis and autophagy mechanisms governed by Bcl-2 family proteins.