Mutations of the BIK gene in human peripheral B-cell lymphomas

Natural killer cell-related gene signature predicts malignancy of glioma and the survival of patients

Background

Natural killer (NK) cells-based therapies are one of the most promising strategies against cancer. The aim of this study is to investigate the natural killer cell related genes and its prognostic value in glioma.

Methods

The Chinese Glioma Genome Atlas (CGGA) was used to develop the natural killer cell-related signature. Risk score was built by multivariate Cox proportional hazards model. A cohort of 326 glioma samples with whole transcriptome expression data from the CGGA database was included for discovery. The Cancer Genome Atlas (TCGA) datasets was used for validation. GO and KEGG were used to reveal the biological process and function associated with the natural killer cell-related signature. We also collected the clinical pathological features of patients with gliomas to analyze the association with tumor malignancy and patients’ survival.

Results

We screened for NK-related genes to build a prognostic signature, and identified the risk score based on the signature. We found that NK-related risk score was independent of various clinical factors. Nature-killer cell gene expression is correlated with clinicopathological features of gliomas. Innovatively, we demonstrated the tight relation between the risk score and immune checkpoints, and found NK-related risk score combined with PD1/PDL1 patients could predict the patient outcome.

Conclusion

Natural killer cell-related gene signature can predict malignancy of glioma and the survival of patients, these results might provide new view for the research of glioma malignancy and individual immunotherapy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09230-y.

Targeting the Bcl-2 Family in B Cell Lymphoma

Although lymphoma is a very heterogeneous group of biologically complex malignancies, tumor cells across all B cell lymphoma subtypes share a set of underlying traits that promote the development and sustain malignant B cells. One of these traits, the ability to evade apoptosis, is essential for lymphoma development. Alterations in the Bcl-2 family of proteins, the key regulators of apoptosis, is a hallmark of B cell lymphoma. Significant efforts have been made over the last 30 years to advance knowledge of the biology, molecular mechanisms, and therapeutic potential of targeting Bcl-2 family members. In this review, we will highlight the complexities of the Bcl-2 family, including our recent discovery of overexpression of the anti-apoptotic Bcl-2 family member Bcl-w in lymphomas, and describe recent advances in the field that include the development of inhibitors of anti-apoptotic Bcl-2 family members for the treatment of B cell lymphomas and their performance in clinical trials.

LncRNA H19 confers chemoresistance in ERα-positive breast cancer through epigenetic silencing of the pro-apoptotic gene BIK

Breast cancer is a common malignancy in women. Acquisition of drug resistance is one of the main obstacles encountered in breast cancer therapy. Long non-coding RNA (lncRNA) has been demonstrated to play vital roles in both development and tumorigenesis. However, the relationship between lncRNAs and the development of chemoresistance is not well established. In the present study, the high expression of lncRNA H19 was identified as a powerful factor associated with paclitaxel (PTX) resistance in ERα-positive breast cancer cells, but not in ERα-negative breast cancer cells. LncRNA H19 attenuated cell apoptosis in response to PTX treatment by inhibiting transcription of pro-apoptotic genes BIK and NOXA. H19 was further confirmed to suppress the promoter activity of BIK by recruiting EZH2 and by trimethylating the histone H3 at lysine 27. Interestingly, our data showed that lncRNA H19 was one of the downstream target molecules of ERα. Altered ERα expression may therefore change H19 levels to modulate the apoptosis response to chemotherapy in breast cancer cells. Our data suggest that the ERα-H19-BIK signaling axis plays an important role in promoting chemoresistance.

Mutational Analysis of the BH3 Domains of Proapoptotic Bcl-2 Family Genes Bad, Bmf and Bcl-G in Laryngeal Squamous Cell Carcinomas

Aims

There is mounting evidence that deregulation of apoptosis is involved in the mechanisms of cancer development. Somatic mutations of apoptosis-related genes have been reported in many human cancers. The aim of this study was to explore the possibility that mutation of the BH3 domains of the proapoptotic Bcl-2 genes Bad, Bmf and Bcl-G might be involved in the development of laryngeal cancer.

Methods

We analyzed the BH3 domains of Bad, Bmf and Bcl-G for the detection of somatic mutations in 33 squamous cell carcinomas of the larynx by a polymerase chain reaction-based single-strand conformation polymorphism assay.

Results

There were no somatic mutations of the BH3 domains of Bad, Bmf and Bcl-G in the laryngeal squamous cell carcinoma samples.

Conclusions

The data presented here indicate that BH3 domain mutation of the proapoptotic genes Bad, Bmf and Bcl-G is rare in laryngeal squamous cell carcinoma and may not contribute to the apoptosis-resistance mechanisms of laryngeal squamous cell carcinoma.

The pro-apoptotic paradox: the BH3-only protein Bcl-2 interacting killer (Bik) is prognostic for unfavorable outcomes in breast cancer

Breast cancer is the leading cause of cancer-associated deaths in women worldwide. Clinical biomarkers give information on disease progression and identify relevant biological pathways. A confounding factor that uncouples markers from disease outcome is the ability of tumor cells to mutate and evade clinical intervention. Therefore, we focussed on apoptotic genes that modulate tumor regression. Using gene and tissue microarray analyses, we identified an association of Bcl-2 interacting killer (Bik) with poor breast cancer prognosis. Bik prognostic ability was independent of Estrogen Receptor/Progesterone Receptor and Her2 status. Additionally, Bik was independent of anti-apoptotic Bcl-2, Bcl-xL, Mcl-1 and Bcl-w suggesting a complex mechanism of tumor promotion identified by Bik high tumors. Bik also stimulates autophagy, which can contribute to enhanced tumor fitness. We found a significant association between the autophagy marker ATG5 and Bik. Combined high expression level of ATG5 and Bik was a stronger predictor of outcome than either alone. Thus, our study identifies Bik as a novel, independent prognostic biomarker for poor outcomes in breast cancer and suggests that Bik-mediated autophagy contributes to disease recurrence.

Apoptosis-Related Gene Expression Profiling in Hematopoietic Cell Fractions of MDS Patients

Although the vast majority of patients with a myelodysplastic syndrome (MDS) suffer from cytopenias, the bone marrow is usually normocellular or hypercellular. Apoptosis of hematopoietic cells in the bone marrow has been implicated in this phenomenon. However, in MDS it remains only partially elucidated which genes are involved in this process and which hematopoietic cells are mainly affected. We employed sensitive real-time PCR technology to study 93 apoptosis-related genes and gene families in sorted immature CD34+ and the differentiating erythroid (CD71+) and monomyeloid (CD13/33+) bone marrow cells. Unsupervised cluster analysis of the expression signature readily distinguished the different cellular bone marrow fractions (CD34+, CD71+ and CD13/33+) from each other, but did not discriminate patients from healthy controls. When individual genes were regarded, several were found to be differentially expressed between patients and controls. Particularly, strong over-expression of BIK (BCL2-interacting killer) was observed in erythroid progenitor cells of low- and high-risk MDS patients (both p = 0.001) and TNFRSF4 (tumor necrosis factor receptor superfamily 4) was down-regulated in immature hematopoietic cells (p = 0.0023) of low-risk MDS patients compared to healthy bone marrow.

BH3-Only Proteins in Health and Disease

BH3-only proteins are proapoptotic members of the broader Bcl-2 family, which promote cell death by directly or indirectly activating Bax and Bak. The expression of BH3-only proteins is regulated both transcriptionally and posttranscriptionally in a cell type-specific and a tissue-specific manner. Research over the last 20 years has provided significant insights into their roles in tissue homeostasis and various pathologies, which in turn has led to the development of novel therapeutics for numerous diseases. In this review, a snapshot of the progress over this period is given, including our current understanding of their regulation, mode of action, role in mammalian development, and pathology.

Breast cancer cell line MDA-MB-231 miRNA profile expression after BIK interference: BIK involvement in autophagy

B-cell lymphoma 2 (BCL2)-interacting killer (apoptosis inducing) (BIK) has been proposed as a tumor suppressor in diverse types of cancers. However, BIK's overexpression in breast cancer (BC) and in non-small lung cancer cells (NSCLCs), associated with a poor prognosis, suggests its participation in tumor progression. In this study, we evaluated the global expression pattern of microRNAs (miRNAs), messenger RNA (mRNA) expression changes in autophagy, and autophagic flux after BIK interference. BIK gene expression was silenced by small interfering RNA (siRNA) in BC cell MDA-MB-231, and BIK interference efficiency was tested by real-time PCR and by Western blotting. BIK expression levels decreased by 75 ± 18 % in the presence of 600 nM siRNA, resulting in the abolishment of BIK expression by 94 ± 30 %. BIK interference resulted in the overexpression of 17 miRNAs that, according to the DIANA-miRPath v3.0 database, are mainly implied in the control of cell signaling, gene expression, and autophagy. The autophagy array revealed downregulation of transcripts which participate in autophagy, and their interactome revealed a complex network, where hepatocyte growth factor-regulated tyrosine kinase substrate (HGS), α-synuclein (SNCA), unc-51-like autophagy activating kinase 1/2 (ULK1/2), and mitogen-activated protein kinase 3 (MAPK3) were shown to be signaling hubs. LC3-II expression-an autophagy marker-was increased by 169 ± 25 % after BIK interference, which indicates the involvement of BIK in autophagy. Altogether, our results indicate-for the first time-that BIK controls the expression of miRNAs, as well as the autophagic flux in MDA-MB-231 cells.

Repression of the proapoptotic cellular BIK/NBK gene by Epstein-Barr virus antagonizes transforming growth factor β1-induced B-cell apoptosis

The Epstein-Barr virus (EBV) establishes a lifelong latent infection in humans. EBV infection of primary B cells causes cell activation and proliferation, a process driven by the viral latency III gene expression program, which includes EBV nuclear proteins (EBNAs), latent membrane proteins, and untranslated RNAs, including microRNAs. Some latently infected cells enter the long-lived memory B-cell compartment and express only EBNA1 transiently (Lat I) or no EBV protein at all (Lat 0). Targeting the molecular machinery that controls B-cell fate decisions, including the Bcl-2 family of apoptosis-regulating proteins, is crucial to the EBV cycle of infection. Here, we show that BIK (also known as NBK), which encodes a proapoptotic "sensitizer" protein, is repressed by the EBNA2-driven Lat III program but not the Lat I program. BIK repression occurred soon after infection of primary B cells by EBV but not by a recombinant EBV in which the EBNA2 gene had been knocked out. Ectopic BIK induced apoptosis in Lat III cells by a mechanism dependent on its BH3 domain and the activation of caspases. We show that EBNA2 represses BIK in EBV-negative B-cell lymphoma-derived cell lines and that this host-virus interaction can inhibit the proapoptotic effect of transforming growth factor β1 (TGF-β1), a key physiological mediator of B-cell homeostasis. Reduced levels of TGF-β1-associated regulatory SMAD proteins were bound to the BIK promoter in response to EBV Lat III or ectopic EBNA2. These data are evidence of an additional mechanism used by EBV to promote B-cell survival, namely, the transcriptional repression of the BH3-only sensitizer BIK.

IMPORTANCE

Over 90% of adult humans are infected with the Epstein-Barr virus (EBV). EBV establishes a lifelong silent infection, with its DNA residing in small numbers of blood B cells that are a reservoir from which low-level virus reactivation and shedding in saliva intermittently occur. Importantly, EBV DNA is found in some B-cell-derived tumors in which viral genes play a key role in tumor cell emergence and progression. Here, we report for the first time that EBV can shut off a B-cell gene called BIK. When activated by a molecular signal called transforming growth factor β1 (TGF-β1), BIK plays an important role in killing unwanted B cells, including those infected by viruses. We describe the key EBV-B-cell molecular interactions that lead to BIK shutoff. These findings further our knowledge of how EBV prevents the death of its host cell during infection. They are also relevant to certain posttransplant lymphomas where unregulated cell growth is caused by EBV genes.

Bryostatin analogue-induced apoptosis in mantle cell lymphoma cell lines

The anti-cancer effects of bryostatin-1, a potent diacylglycerol analogue, have traditionally been attributed to its action on protein kinase C. However, we previously documented apoptosis in a B non-Hodgkin lymphoma cell line involving diacylglycerol analogue stimulation of Ras guanyl-releasing protein, a Ras activator, and Bim, a proapoptotic Bcl-2 family protein. To further explore the role of Bim, we examined several Bim-deficient B non-Hodgkin lymphoma cells for their responses to pico, a synthetic bryostatin-1-like compound. The Bim(-) mantle cell lymphoma cell lines Jeko-1, Mino, Sp53, UPN1, and Z138 and the Bim(+) cell line Rec-1, as well as the Burkitt lymphoma cells lines BL2 (Bim(-)) and Daudi (Bim(+)), were examined for their response to pico using assays for proliferation and apoptosis as well as biochemical methods for Ras guanyl-releasing proteins and Bcl-2 family members. With the exception of UPN1, mantle cell lymphoma cell lines underwent pico-induced apoptosis, as did BL2. In some cases, hallmarks of apoptosis were substantially diminished in the presence of mitogen-activated protein kinase kinase inhibitors. Pico treatment generally led to increased expression of proapoptotic Bik, although the absolute levels of Bik varied considerably between cell lines. A pico-resistant variant of Z138 exhibited decreased Bik induction compared to parental Z138 cells. Pico also generally decreased expression of anti-apoptotic Bcl-XL and Mcl1. Although, these changes in Bcl-2 family members seem unlikely to fully account for the differential behavior of the cell lines, our demonstration of a potent apoptotic process in most cell lines derived from mantle cell lymphoma encourages a re-examination of diacylglycerol analogues in the treatment of this subset of B non-Hodgkin lymphoma cases.

UNBS1450, a steroid cardiac glycoside inducing apoptotic cell death in human leukemia cells

Cardiac steroids are used to treat various diseases including congestive heart failure and cancer. The aim of this study was to investigate the anti-leukemic activity of UNBS1450, a hemi-synthetic cardenolide belonging to the cardiac steroid glycoside family. Here, we report that, at low nanomolar concentrations, UNBS1450 induces apoptotic cell death. Subsequently, we have investigated the molecular mechanisms leading to apoptosis activation. Our results show that UNBS1450 inhibits NF-κB transactivation and triggers apoptosis by cleavage of pro-caspases 8, 9 and 3/7, by decreasing expression of anti-apoptotic Mcl-1 and by recruitment of pro-apoptotic Bak and Bax protein eventually resulting in cell death.

The landscape of somatic copy-number alteration across human cancers

A powerful way to discover key genes with causal roles in oncogenesis is to identify genomic regions that undergo frequent alteration in human cancers. Here we present high-resolution analyses of somatic copy-number alterations (SCNAs) from 3,131 cancer specimens, belonging largely to 26 histological types. We identify 158 regions of focal SCNA that are altered at significant frequency across several cancer types, of which 122 cannot be explained by the presence of a known cancer target gene located within these regions. Several gene families are enriched among these regions of focal SCNA, including the BCL2 family of apoptosis regulators and the NF-kappaBeta pathway. We show that cancer cells containing amplifications surrounding the MCL1 and BCL2L1 anti-apoptotic genes depend on the expression of these genes for survival. Finally, we demonstrate that a large majority of SCNAs identified in individual cancer types are present in several cancer types.

Targeting the BCL-2 family in malignancies of germinal centre origin

The germinal centre is a dynamic microenvironment where B-cell responses are honed. Antigen-specific cells undergo clonal expansion followed by antibody affinity maturation and class switching through somatic hypermutation and recombination of immunoglobulin genes respectively. The huge proliferative capacity of the B-cells and the potential for generating non-functional or autoreactive immunoglobulins, necessitate strict control measures. Pro-apoptotic signalling pathways via B-cell receptors, FAS and the TGF-beta receptor, ALK5, ensure that apoptosis of germinal centre B-cells is the norm and cells only survive to differentiate fully if they receive sufficient pro-survival signals to overcome their 'primed for death' status. Several of the B-cell signalling pathways converge on the intrinsic apoptotic machinery to control expression of the BCL-2 family of apoptosis regulators including BIM, the pro-survival factor BCL-X(L) and the BH3-only protein, BIK (recently identified as a mediator of a TGF-beta-induced default apoptosis pathway in human B-cells). It is a foreseeable hazard that cells undergoing genetic mutation and recombination events might unintentionally target some of these factors, resulting in defective programmed cell death. Here we discuss the function of BCL-2 family proteins in germinal centre reactions, their deregulation in malignancies of germinal centre origin, and the potential for targeting BCL-2-related proteins therapeutically in lymphomas.

Peptides and peptide mimics as modulators of apoptotic pathways

Programmed cell death is an important and stringently controlled process. Aberrancies in its control mechanisms can lead to disease; overactive apoptosis can cause neurodegenerative disorders, whereas deficient apoptotic activity can lead to cancer. Therefore, controlling apoptotic pathways with peptides is showing increasing promise as a strategy in drug development.Programmed cell death or apoptosis is a noninvasive and strictly regulated cellular process required for organism development and tissue homeostasis. Deficiencies in apoptotic pathways are the source of many diseases such as cancer, neurodegenerative and autoimmune diseases, and disorders related to an inappropriate loss of cells such as heart failure, stroke, and liver injury. Validation of the various points of intervention as targets for drug development has been the subject of a vast number of studies. Peptides are essential tools for drug discovery, as well as preclinical and pharmaceutical drug development.

Bcl2 family proteins in carcinogenesis and the treatment of cancer

Deregulation of Bcl2 family members is a frequent feature of human malignant diseases and causal for therapy resistance. A number of studies have recently shed light onto the role of pro- and anti-apoptotic Bcl2 family members in tumour-pathogenesis and in mediating the effects of classical as well as novel front-line anticancer agents, allowing the development of more efficient and more precisely targeted treatment regimens. Most excitingly, recent progress in our understanding of how Bcl2-like proteins maintain or perturb mitochondrial integrity has finally enabled the development of rational-design based anticancer therapies that directly target Bcl2 regulated events at the level of mitochondria. This review aims to give an overview on the most recent findings on the role of the Bcl2 family in tumour development in model systems of cancer, to relate these findings with observations made in human pathologies and drug-action.

TGF-beta induces apoptosis in human B cells by transcriptional regulation of BIK and BCL-XL

Transforming growth factor-beta (TGF-beta) potently induces apoptosis in Burkitt's lymphoma (BL) cell lines and in explanted primary human B lymphocytes. The physiological relevance and mechanism of TGF-beta-mediated apoptosis induction in these cells remains to be determined. Here we demonstrate the requirement for TGF-beta-mediated regulation of BIK and BCL-X(L) to activate an intrinsic apoptotic pathway in centroblastic BL cells. TGF-beta directly induced transcription of BIK and a consensus Smad-binding element identified in the BIK promoter recruits TGF-beta-activated Smad transcription factor complexes in vivo. TGF-beta also transcriptionally repressed expression of the apoptosis inhibitor BCL-X(L). Inhibition of BCL-X(L) sensitised BL cells to TGF-beta-induced apoptosis whereas overexpression of BCL-X(L) or suppression of BIK by shRNA, diminished TGF-beta-induced apoptosis. BIK and BCL-X(L) were also identified as TGF-beta target genes in purified normal human centroblast B cells and immunohistochemical analyses of tonsil tissue revealed widespread TGF-beta receptor-regulated Smad activation and a focal pattern of BIK expression. Furthermore, using a selective inhibitor of the TGF-beta receptor we provide evidence that autocrine TGF-beta signalling through ALK5 contributes to the default apoptotic programme in normal human centroblasts undergoing spontaneous apoptosis. Our data suggests that TGF-beta may act as a physiological mediator of human germinal centre homoeostasis by regulation of BIK and BCL-X(L).

BIK, the founding member of the BH3-only family proteins: mechanisms of cell death and role in cancer and pathogenic processes

BIK is the founding member of the BH3-only family pro-apoptotic proteins. BIK is predominantly localized in the ER and induces apoptosis through the mitochondrial pathway by mobilizing calcium from the ER to the mitochondria and remodeling the mitochondrial cristae. BIK-mediated apoptosis is mediated by selective activation of BAX. BIK also induces non-apoptotic cell death in certain cell types by unknown mechanisms. BIK is non-essential for animal development, but appears to be functionally redundant for certain developmental functions with BIM. BIK is implicated in the selection of mature B cells in humans. BIK is a pro-apoptotic tumor suppressor in several human tissues and its expression in cancers is prevented by chromosomal deletions encompassing the Bik locus or by epigenetic silencing. BIK appears to be a critical effector in apoptosis induced by toxins, cytokines and virus infection. Several anti-cancer drugs transcriptionally activate Bik gene expression through transcriptional pathways dependent on factors such as E2F and p53 or by removal of epigenetic marks on the chromatin. BIK appears to be a prominent target for anti-cancer drugs that inhibit proteasomal functions. BIK has also been used as a therapeutic molecule in gene therapy-based approaches to treat difficult cancers.

BH3-only proteins in apoptosis and beyond: an overview

BH3-only BCL-2 family proteins are effectors of canonical mitochondrial apoptosis. They discharge their pro-apoptotic functions through BH1-3 pro-apoptotic proteins such as BAX and BAK, while their activity is suppressed by BH1-4 anti-apoptotic BCL-2 family members. The precise mechanism by which BH3-only proteins mediate apoptosis remains unresolved. The existing data are consistent with three mutually non-exclusive models (1) displacement of BH1-3 proteins from complexes with BH1-4 proteins; (2) direct interaction with and conformational activation of BH1-3 proteins; and (3) membrane insertion and membrane remodeling. The BH3-only proteins appear to play critical roles in restraining cancer and inflammatory diseases such as rheumatoid arthritis. Molecules that mimic the effect of BH3-only proteins are being used in treatments against these diseases. The cell death activity of a subclass of BH3-only members (BNIP3 and BNIP3L) is linked to cardiomyocyte loss during heart failure. In addition to their established role in apoptosis, several BH3-only members also regulate diverse cellular functions in cell-cycle regulation, DNA repair and metabolism. Several members are implicated in the induction of autophagy and autophagic cell death, possibly through unleashing of the BH3-only autophagic effector Beclin 1 from complexes with BCL-2/BCL-xL. The Chapters included in the current Oncogene Review issues provide in-depth discussions on various aspects of major BH3-only proteins.

Involvement of BH3-only proteins in hematologic malignancies

The interaction between anti-apoptotic and pro-apoptotic members of the Bcl-2 family proteins determines life or death for cancer cells. In this context, BH3-only proteins (such as Bim), members of the pro-apoptotic Bcl-2 family proteins, act as key initiators of apoptosis by activating Bax and Bak through liberating them from anti-apoptotic Bcl-2 members. This then leads to the disruption of mitochondrial outer membrane, and eventually promotes proteolytic cascades for cellular dismantling. We here review the growing evidence of how BH3-only proteins are involved in tumorigenesis and in apoptosis induced by anti-cancer agents in hematologic malignancies. A deeper understanding of the roles of BH3-only proteins in cell death regulation may yield crucial insights for the further development of more effective and rational cell killing strategies. Recent developments in the direct therapeutic manipulation of Bcl-2 proteins using BH3-mimicking agents, such as ABT-737 or GX15-070, for hematologic malignancies are also summarized.

Expressional and mutational analysis of pro-apoptotic Bcl-2 member PUMA in hepatocellular carcinomas

Deregulation of apoptosis is involved in mechanisms of cancer development. PUMA is a pro-apoptotic member of the Bcl-2 family and mediates p53-dependent and -independent apoptosis. The aim of this study was to investigate whether alterations of PUMA protein expression and somatic mutations of PUMA gene are characteristics of human hepatocellular carcinoma (HCC). We analyzed expression of PUMA protein in 20 HCCs using immunohistochemistry. Also, we analyzed mutation of the Bcl-2 homology 3 (BH3) domain of PUMA gene, which is an important domain in apoptosis function of PUMA by single-strand conformation polymorphism (SSCP) in 69 HCCs. PUMA protein expression was detected in both HCC cells and non-tumor hepatocytes in all of the 20 HCCs. In 10 of these HCCs, cancer cells showed higher PUMA expression than non-tumor (cirrhotic) hepatocytes of the same patients; whereas in the remaining 10, cancer cells and non-tumor hepatocytes showed similar levels. Mutational analysis revealed no PUMA BH3 domain mutation in the 69 HCCs, suggesting that PUMA BH3 domain mutation is not a direct target of inactivation in hepatocellular cancer development. The increased expression of PUMA in malignant hepatocellular cells relative to that in non-tumor hepatocytes suggests that PUMA expression may play a role in HCC development.

BCL-2 family proteins: critical checkpoints of apoptotic cell death

Apoptosis is a morphologically distinct form of programmed cell death essential for normal development and tissue homeostasis. Aberrant regulation of this pathway is linked to multiple human diseases, including cancer, autoimmunity, neurodegenerative disorders, and diabetes. The BCL-2 family of proteins constitutes a critical control point in apoptosis residing immediately upstream of irreversible cellular damage, where family members control the release of apoptogenic factors from mitochondria. The cardinal member of this family, BCL-2, was originally discovered as the defining oncogene in follicular lymphomas, located at one reciprocal breakpoint of the t(14;18) (q32;q21) chromosomal translocation. Since this original discovery, remarkable efforts marshaled by many investigators around the world have advanced our knowledge of the basic biology, molecular mechanisms, and therapeutic targets in the apoptotic pathway. This review highlights findings from many laboratories that have helped uncover some of the critical control points in apoptosis. The emerging picture is that of an intricate cellular machinery orchestrated by tightly regulated molecular interactions and conformational changes within BCL-2 family proteins that ultimately govern the cellular commitment to apoptotic death.

Pro-apoptotic PUMA and anti-apoptotic phospho-BAD are highly expressed in colorectal carcinomas

Several lines of evidence indicate that, together with deregulated growth, alteration of apoptosis plays a pivotal role in tumorigenesis. PUMA, a pro-apoptotic member of Bcl-2 family, mediates p53-dependent and -independent apoptosis. BAD is also a pro-apoptotic Bcl-2 family member and phosphorylation of BAD protein inhibits the pro-apoptosis function of BAD. To see whether the alteration of protein expressions of PUMA and phospho-BAD (p-BAD) are characteristics of human colorectal cancers, we analyzed the expression of these proteins in 103 colorectal carcinomas by immunohistochemistry. Also, we analyzed the mutation of the Bcl-2 homology 3 (BH3) domain of PUMA gene, an important domain in the apoptosis function of PUMA, by single-strand conformation polymorphism (SSCP) in 98 colorectal carcinomas. p-BAD immunostaining was detected in 62 cases (60.1%) of the 103 carcinomas, whereas it was not detected in the normal colonic mucosal epithelial cells. PUMA protein expression was detected in both cancer cells and normal mucosal cells in all of the 103 cases. However, the cancer cells showed higher intensities of PUMA immunostaining than the normal cells of the same patients in 50.4% of the cases. There was no association of the p-BAD expression with the PUMA expression. The mutational analysis revealed no PUMA BH3 domain mutation in the cancers. Our data indicated that expressions of both PUMA and p-BAD were increased in the colorectal cancer cells, and suggested that the increased expression of these proteins in malignant colorectal epithelial cells compared to the normal mucosal epithelial cells may possibly alter the cell death regulation during colorectal tumorigenesis.

Age-related transcription levels of KU70, MGST1 and BIK in CD34+ hematopoietic stem and progenitor cells

Despite the known longevity of human hematopoietic stem and progenitor cells (HSC), numerous functional impairments of these cells can be observed in an age-dependent manner. However, the molecular alterations associated with aging of HSC are largely unknown. Therefore, we scrutinized gene expression patterns of HSC from newborn, young and old healthy donors. CD34+ HSC were isolated via immuno-magnetic separation and evaluated by FACS analysis. We performed cDNA macroarray analyses on a first set of CD34+ samples (n=13). We found the genes encoding KU-antigen 70 kD (KU70), microsomal glutathione S-transferase 1 (MGST1) and BCL2-interacting killer (BIK) to possess age-related mRNA expression levels. KU70 is a DNA repair gene and part of the DNA-dependent protein kinase (DNA-PK) complex. Its expression was negatively correlated with donor age showing highest expression levels in newborn, 2.6-fold lower levels in young and 6.3-fold lower levels in old donors. The transcription levels of MGST1, a gene protecting against oxidative stress, progressively increased with age. Expression was lowest in newborn, 2.6-fold higher in young and 4.3-fold higher in old donors. BIK is a proapoptotic gene and its expression was positively correlated with donor age: lowest in newborn, 1.8-fold higher in young and 4.1-fold higher in old donors. These findings were confirmed with an independent, second set of CD34+ samples (n=16) by means of quantitative real-time RT-PCR. Elucidation of age-dependent molecular alterations in healthy HSC facilitate a better understanding of functional impairments in hematopoiesis and may become valuable for anti-aging drug development and the emerging field of regenerative medicine.

Immunohistochemical analysis of phospho-BAD protein and mutational analysis of BAD gene in gastric carcinomas

Mounting evidence indicates that deregulation of apoptosis contributes to the development of human cancers. BAD, a proapoptotic Bcl-2 family protein, regulates the intrinsic apoptosis pathway. The aim of this study was to explore whether alterations of phospho-BAD (p-BAD) protein that antagonizes apoptosis function of BAD and mutation of BAD gene are characteristics of human gastric cancers. We analyzed expression of p-BAD in 60 gastric adenocarcinomas by immunohistochemistry. Also, we analyzed BAD gene for detection of somatic mutations by single-strand conformation polymorphism (SSCP) assay. p-BAD expression was detected well in normal gastric mucosal epithelial cells, whereas it was detected in only 51% (31 of the 60) of the cancers. There was no somatic mutation of BAD gene in the 60 gastric cancer samples. The decreased expression of p-BAD in malignant gastric epithelial cells compared to normal mucosal epithelial cells suggested that loss of p-BAD expression may play a role in gastric tumorigenesis. The data also suggest that BAD mutation may not be a direct target of inactivation in gastric tumorigenesis.

GRP78/BiP inhibits endoplasmic reticulum BIK and protects human breast cancer cells against estrogen starvation-induced apoptosis

The recent development of hormonal therapy that blocks estrogen synthesis represents a major advance in the treatment of estrogen receptor-positive breast cancer. However, cancer cells often acquire adaptations resulting in resistance. A recent report reveals that estrogen starvation-induced apoptosis of breast cancer cells requires BIK, an apoptotic BH3-only protein located primarily at the endoplasmic reticulum (ER). Searching for novel partners that interact with BIK at the ER, we discovered that BIK selectively forms complex with the glucose-regulated protein GRP78/BiP, a major ER chaperone with prosurvival properties naturally induced in the tumor microenvironment. GRP78 overexpression decreases apoptosis of 293T cells induced by ER-targeted BIK. For estrogen-dependent MCF-7/BUS breast cancer cells, overexpression of GRP78 inhibits estrogen starvation-induced BAX activation, mitochondrial permeability transition, and consequent apoptosis. Further, knockdown of endogenous GRP78 by small interfering RNA (siRNA) sensitizes MCF-7/BUS cells to estrogen starvation-induced apoptosis. This effect was substantially reduced when the expression of BIK was also reduced by siRNA. Our results provide the first evidence that GRP78 confers resistance to estrogen starvation-induced apoptosis in human breast cancer cells via a novel mechanism mediated by BIK. These results further suggest that GRP78 expression level in the tumor cells may serve as a prognostic marker for responsiveness to hormonal therapy based on estrogen starvation and that combination therapy targeting GRP78 may enhance efficacy and reduce resistance.

Immunohistochemical analysis of pro-apoptotic PUMA protein and mutational analysis of PUMA gene in gastric carcinomas

BACKGROUND

Mounting evidence indicates that alteration of apoptosis is involved in the mechanisms of cancer development. PUMA, a pro-apoptotic member of Bcl-2 family, mediates p53-dependent and -independent apoptosis.

AIM

The aim of this study was to explore whether alteration of PUMA protein expression is a characteristic of human gastric carcinomas.

PATIENTS AND METHODS

We analysed expression of PUMA protein in 60 gastric adenocarcinomas by immunohistochemistry. Also, we examined PUMA gene mutation in the same tissues by a single-strand conformation polymorphism.

RESULTS

PUMA protein expression was detected in 44 cases (73%) of the 60 gastric carcinomas, whereas it was not detected in normal gastric mucosal epithelial cells. The mutational analysis revealed no PUMA mutation in the gastric carcinomas.

CONCLUSIONS

Our data suggest that PUMA mutation is not a direct target of inactivation in gastric tumourigenesis. Also, increased expression of PUMA in malignant gastric epithelial cells compared with normal mucosal epithelial cells suggested that PUMA expression may play a role in gastric tumourigenesis.

The major subtypes of human B-cell lymphomas lack mutations in BCL-2 family member BAD

Members of the BCL-2 gene family are well known for their role in the pathogenesis of B-cell lymphomas in humans and in mouse models. A recent report that knockout mice deficient for the proapoptotic BCL-2 family member gene BAD frequently develop B-cell lymphomas prompted us to analyze a large collection of human B-cell lymphomas for inactivating mutations in the BAD gene. All 3 exons of the BAD gene were amplified and directly sequenced. The 81 lymphomas analyzed included 16 cases of B-cell chronic lymphocytic leukemia, 11 mantle-cell lymphomas, 10 follicular lymphomas, 7 MALT lymphomas, 8 Burkitt's lymphoma cell lines, 3 cell lines of multiple myeloma, 15 cases and 4 cell lines of diffuse large B-cell lymphoma and 7 Hodgkin's lymphoma lines. No mutations were found in any of the cases. We conclude that mutations in the BAD gene do not play a role in the pathogenesis of the major subtypes of human B-cell lymphomas.

Expressional analysis of anti-apoptotic phospho-BAD protein and mutational analysis of pro-apoptotic BAD gene in hepatocellular carcinomas

BACKGROUND

It has become clear that, together with proliferation, deregulation of apoptosis plays a pivotal role in tumourigenesis. BAD is a pro-apoptotic Bcl-2 family protein and regulates the intrinsic apoptosis pathway. Phosphorylation of BAD inhibits the apoptosis function of BAD.

AIMS

To investigate whether alteration of the phospho-BAD protein and somatic mutation of BAD gene are characteristics of human hepatocellular carcinoma.

PATIENTS AND METHODS

We analysed the expression of phospho-BAD in 20 hepatocellular carcinomas by immunohistochemistry. Also, we analysed the BAD gene for the detection of somatic mutations by a single-strand conformation polymorphism assay in 69 hepatocellular carcinomas.

RESULTS

Phospho-BAD expression in the non-tumour hepatocytes was seen in all of the hepatocellular carcinomas, while the expression in the cancer cells was observed in 15% (3 of the 20) of the hepatocellular carcinomas. There was no somatic mutation of BAD Bcl-2 homology 3 (BH3) domain in the 69 hepatocellular carcinomas.

CONCLUSIONS

The data showed that loss of phospho-BAD expression, but not BAD gene mutation, is a feature of hepatocellular carcinomas. The decreased expression of phospho-BAD in the hepatocellular carcinoma cells compared to the non-tumour hepatocytes suggests that loss of phospho-BAD expression may play a role in hepatocellular tumourigenesis.

Epigenomic Profiling Reveals Novel and Frequent Targets of Aberrant DNA Methylation-Mediated Silencing in Malignant Glioma

Malignant glioma is the most common central nervous system tumor of adults and is associated with a significant degree of morbidity and mortality. Gliomas are highly invasive and respond poorly to conventional treatments. Gliomas, like other tumor types, arise from a complex and poorly understood sequence of genetic and epigenetic alterations. Epigenetic alterations leading to gene silencing, in the form of aberrant CpG island promoter hypermethylation and histone deacetylation, have not been thoroughly investigated in brain tumors, and elucidating such changes is likely to enhance our understanding of their etiology and provide new treatment options. We used a combined approach of pharmacologic inhibition of DNA methylation and histone deacetylation, coupled with expression microarrays, to identify novel targets of epigenetic silencing in glioma cell lines. From this analysis, we identified >160 genes up-regulated by 5-aza-2'-deoxycytidine and trichostatin A treatment. Further characterization of 10 of these genes, including the putative metastasis suppressor CST6, the apoptosis-inducer BIK, and TSPYL5, whose function is unknown, revealed that they are frequent targets of epigenetic silencing in glioma cell lines and primary tumors and suppress glioma cell growth in culture. Furthermore, we show that other members of the TSPYL gene family are epigenetically silenced in gliomas and dissect the contribution of individual DNA methyltransferases to the aberrant promoter hypermethylation events. These studies, therefore, lay the foundation for a comprehensive understanding of the full extent of epigenetic changes in gliomas and how they may be exploited for therapeutic purposes.

BH3-only proteins in cell death initiation, malignant disease and anticancer therapy

Induction of apoptosis in tumour cells, either by direct activation of the death receptor pathway using agonistic antibodies or recombinant ligands, or direct triggering of the Bcl-2-regulated intrinsic apoptosis pathway by small molecule drugs, carries high hopes to overcome the shortcomings of current anticancer therapies. The latter therapy concept builds on a more detailed understanding of how Bcl-2-like molecules maintain mitochondrial integrity and how BH3-only proteins and Bax/Bak-like molecules can undermine it. Means to unleash the apoptotic potential of BH3-only proteins in tumour cells, or bypass the need for BH3-only proteins by blocking possible interactions of Bcl-2-like prosurvival molecules with Bax and/or Bak allowing their direct activation, constitute interesting options for the design of novel anticancer therapies.

Mutational analysis of proapoptotic caspase-9 gene in common human carcinomas

Mounting evidence indicates that deregulation of apoptosis is involved in the mechanisms of cancer development. Caspase-9 plays a crucial role in the initiation phase of the intrinsic apoptosis pathway. To explore the possibility that the genetic alterations of caspase-9 might be involved in the development of human cancers, we analyzed the entire coding region and all splice sites of the human caspase-9 gene for the detection of somatic mutations in a series of 353 cancers, including 180 gastric, 104 colorectal and 69 lung adenocarcinomas. Overall, we detected three somatic mutations of caspase-9, but all of the mutations were silent mutations. The mutations were observed in 2 of 104 colorectal carcinomas and 1 of 180 gastric carcinomas. These data indicate that the caspase-9 gene is rarely mutated in gastric, colorectal and lung adenocarcinomas, and suggest that caspase-9 gene mutation may not contribute to the pathogenesis of these cancers.

BH3 domain mutation of proapoptotic genes Bad, Bmf and Bcl-G is rare in transitional cell carcinomas of the urinary bladder

AIMS

Mounting evidence indicates that deregulation of apoptosis contributes to the development of human cancers. Bcl-2 family proteins regulate the intrinsic apoptosis pathway. The aim of this study was to explore the possibility that mutation of BH3 domain of proapoptotic Bcl-2 genes Bad, Bmf and Bcl-G might be involved in the development of urinary bladder cancer.

METHODS

We analysed the BH3 domains of Bad, Bmf and Bcl-G genes for the detection of somatic mutations in 43 transitional cell carcinomas (TCCs) of the urinary bladder by a single strand conformation polymorphism assay in this study.

RESULTS

There was no somatic mutation of BH3 domains of Bad, Bmf and Bcl-G genes in the TCC samples.

CONCLUSION

The data presented here indicate that BH3 domain mutation of these genes is rare in TCCs and may not contribute to the pathogenesis of TCCs.

A molecular analysis by gene expression profiling reveals Bik/NBK overexpression in sporadic breast tumor samples of Mexican females

Background

Breast cancer is one of the most frequent causes of death in Mexican women over 35 years of age. At molecular level, changes in many genetic networks have been reported as associated with this neoplasia. To analyze these changes, we determined gene expression profiles of tumors from Mexican women with breast cancer at different stages and compared these with those of normal breast tissue samples.

Methods

³²P-radiolabeled cDNA was synthesized by reverse transcription of mRNA from fresh sporadic breast tumor biopsies, as well as normal breast tissue. cDNA probes were hybridized to microarrays and expression levels registered using a phosphorimager. Expression levels of some genes were validated by real time RT-PCR and immunohistochemical assays.

Results

We identified two subgroups of tumors according to their expression profiles, probably related with cancer progression. Ten genes, unexpressed in normal tissue, were turned on in some tumors. We found consistent high expression of Bik gene in 14/15 tumors with predominant cytoplasmic distribution.

Conclusion

Recently, the product of the Bik gene has been associated with tumoral reversion in different neoplasic cell lines, and was proposed as therapy to induce apoptosis in cancers, including breast tumors. Even though a relationship among genes, for example those from a particular pathway, can be observed through microarrays, this relationship might not be sufficient to assign a definitive role to Bik in development and progression of the neoplasia. The findings herein reported deserve further investigation.

High-resolution genome-wide mapping of genetic alterations in human glial brain tumors

High-resolution genome-wide mapping of exact boundaries of chromosomal alterations should facilitate the localization and identification of genes involved in gliomagenesis and may characterize genetic subgroups of glial brain tumors. We have done such mapping using cDNA microarray-based comparative genomic hybridization technology to profile copy number alterations across 42,000 mapped human cDNA clones, in a series of 54 gliomas of varying histogenesis and tumor grade. This gene-by-gene approach permitted the precise sizing of critical amplicons and deletions and the detection of multiple new genetic aberrations. It has also revealed recurrent patterns of occurrence of distinct chromosomal aberrations as well as their interrelationships and showed that gliomas can be clustered into distinct genetic subgroups. A subset of detected alterations was shown predominantly associated with either astrocytic or oligodendrocytic tumor phenotype. Finally, five novel minimally deleted regions were identified in a subset of tumors, containing putative candidate tumor suppressor genes (TOPORS, FANCG, RAD51, TP53BP1, and BIK) that could have a role in gliomagenesis.

The proteasome inhibitor bortezomib sensitizes cells to killing by death receptor ligand TRAIL via BH3-only proteins Bik and Bim

Previously, we showed that the proteasome inhibitor bortezomib/Velcade (formerly PS-341) synergizes with the protein tumor necrosis factor alpha-related apoptosis-inducing ligand (TRAIL), a ligand for certain death receptors, to induce apoptosis in cell lines derived from prostate and colon cancers. Because apoptosis is often triggered by BH3-only proteins of the Bcl-2 family, we have explored the hypothesis that bortezomib contributes to the apoptosis by up-regulating their levels. Indeed, bortezomib induced increases of Bik and/or Bim in multiple cell lines but not notably of two other BH3-only proteins (Puma and Bid) nor other family members (Bax, Bak, Bcl-2, and Bcl-xL). The increase in Bik levels seems to reflect inhibition by bortezomib of its proteasome-mediated degradation. Importantly, both Bik and Bim seem central to the proapoptotic function of bortezomib, because mouse embryo fibroblasts in which the genes for both Bik and Bim had been disrupted were refractory to its cytotoxic action. Similarly, the synergy between bortezomib and TRAIL in killing human prostate cancer cells was impaired in cells in which both Bik and Bim were down-regulated by RNA interference. Further evidence that bortezomib acts through the mitochondrial pathway regulated by the Bcl-2 family is that deficiency for APAF-1, which acts downstream of Bcl-2, also blocked its apoptotic effect. These results implicate BH3-only proteins, in particular both Bik and Bim, as important mediators of the antitumor action of bortezomib and establish their role in its enhancement of TRAIL-induced apoptosis.

Inactivating mutations of proapoptotic Bad gene in human colon cancers

Evidence exists that deregulation of apoptosis is involved in the mechanisms of cancer development, and the somatic mutations of apoptosis-related genes have been reported in human cancers. Bcl-XL/Bcl-2-associated death promoter (Bad), a proapoptotic member of Bcl-2 family, plays an important role in the intrinsic apoptosis pathway. To explore the possibility that the genetic alterations of Bad might be involved in the development of human cancers, we analyzed the entire coding region and all splice sites of human Bad gene in 47 colon adenocarcinomas. Overall, we detected two somatic missense mutations (4.3%) in Bad gene. Interestingly, both of the Bad mutations were detected in the gene sequences encoding the Bcl-2 homology3 domain of Bad, which has a crucial role in inducing cell death. Transfection study revealed that both of the tumor-derived Bad mutants had decreased apoptosis activities compared with the wild-type Bad, indicating that the Bad mutations reduced the cell death function of Bad. Co-immunoprecipitation assay revealed that binding of one of the tumor-derived Bad mutants with Bcl-2 and Bcl-XL is reduced. This is the first report on Bad gene mutation in human malignancies, and our data suggest that Bad gene is occasionally mutated in colon cancers and that somatic mutation of Bad may contribute to the development of colon cancers.

The Bik BH3-only protein is induced in estrogen-starved and antiestrogen-exposed breast cancer cells and provokes apoptosis

Evidence has been accumulating that some estrogen-dependent human breast cancers require estrogen for not only proliferation but also survival. To obtain insights into the molecular mechanisms of apoptosis of breast cancer cells subjected to estrogen starvation or exposed to antiestrogens, we characterized changes in the gene expression profile of MCF-7/BUS human breast cancer cells and revealed a strong induction of Bik, a member of the BH3-only proapoptotic proteins. The Bik mRNA transcript and protein were strongly induced by estrogen starvation or exposure to fulvestrant, a pure antiestrogen that competes with the natural estrogens for binding to the estrogen receptors. This Bik induction preceded apoptotic cell death, which was blocked by zVAD-fmk, a pancaspase inhibitor. Amounts of the Bcl-2-related proteins, such as Bcl-2, Bcl-XL, or Bax, showed only marginal changes in the presence or absence of estrogens or antiestrogens. Suppression of Bik expression by using the small interfering RNA effectively blocked the fulvestrant-induced breast cancer cell apoptosis. These results indicate that Bik is induced in MCF-7/BUS cells in the absence of estrogen signaling and plays a critical role in the antiestrogen-provoked breast cancer cell apoptosis.

Inactivating mutation of the pro-apoptotic gene BID in gastric cancer

There is evidence that deregulation of apoptosis is mechanistically involved in cancer development and somatic mutations of apoptosis-related genes have been reported in human cancers. BID, a pro-apoptotic member of the Bcl-2 family, interconnects the extrinsic apoptosis pathway initiated by death receptors to the intrinsic apoptosis pathway. To explore the possibility that genetic alterations of BID might be involved in the development of human cancers, this study analysed the entire coding region and all splice sites in the human BID gene in 67 advanced gastric carcinomas. Overall, four BID mutations (6.0%) were detected that consisted of one frameshift and three missense mutations. The tumour-derived BID mutants were expressed in 293T cells and it was found that, compared with wild-type BID, the frequency of apoptosis was significantly reduced in cells expressing the gene containing the frameshift mutation. Furthermore, expression of the inactivating frameshift mutant interfered with cell death by overexpression of death receptors, indicating that this mutant inhibits the extrinsic apoptosis pathway in a dominant-negative fashion. Also, the frameshift mutation rendered cancer cells resistant to apoptosis induced by the anti-cancer drug 5-fluorouracil (5-FU). This is the first report of BID gene mutation in human malignancy. The data suggest that such mutations occur rarely in gastric cancers and that only a small fraction of BID mutations may lead to the loss of its apoptotic function.