MYC-induced myeloid leukemogenesis is accelerated by all six members of the antiapoptotic BCL family

Bcl-xL is translocated to the nucleus via CtBP2 to epigenetically promote metastasis

Nuclear Bcl-xL is found to promote cancer metastasis independently of its mitochondria-based anti-apoptotic activity. How Bcl-xL is translocated into the nucleus and how nuclear Bcl-xL regulates histone H3 trimethyl Lys4 (H3K4me3) modification have yet to be understood. Here, we report that C-terminal Binding Protein 2 (CtBP2) binds to Bcl-xL via its N-terminus and translocates Bcl-xL into the nucleus. Knockdown of CtBP2 by shRNA decreases the nuclear portion of Bcl-xL and reverses Bcl-xL-induced invasion and metastasis in mouse models. Furthermore, knockout of CtBP2 not only reduces the nuclear portion of Bcl-xL but also suppresses Bcl-xL transcription. The binding between Bcl-xL and CtBP2 is required for their interaction with MLL1, a histone H3K4 methyltransferase. Pharmacologic inhibition of the MLL1 enzymatic activity reverses Bcl-xL-induced H3K4me3 and TGFβ mRNA upregulation, as well as invasion. Moreover, the cleavage under targets and release using nuclease (CUT&RUN) assay coupled with next-generation sequencing reveals that H3K4me3 modifications are particularly enriched in the promotor regions of genes encoding TGFβ and its signaling pathway members in cancer cells overexpressing Bcl-xL. Altogether, the metastatic function of Bcl-xL is mediated by its interaction with CtBP2 and MLL1 and this study offers new therapeutic strategies to treat Bcl-xL-overexpressing cancer.

MYC Oncogene: A Druggable Target for Treating Cancers with Natural Products

Various diseases, including cancers, age-associated disorders, and acute liver failure, have been linked to the oncogene, MYC. Animal testing and clinical trials have shown that sustained tumor volume reduction can be achieved when MYC is inactivated, and different combinations of therapeutic agents including MYC inhibitors are currently being developed. In this review, we first provide a summary of the multiple biological functions of the MYC oncoprotein in cancer treatment, highlighting that the equilibrium points of the MYC/MAX, MIZ1/MYC/MAX, and MAD (MNT)/MAX complexes have further potential in cancer treatment that could be used to restrain MYC oncogene expression and its functions in tumorigenesis. We also discuss the multifunctional capacity of MYC in various cellular cancer processes, including its influences on immune response, metabolism, cell cycle, apoptosis, autophagy, pyroptosis, metastasis, angiogenesis, multidrug resistance, and intestinal flora. Moreover, we summarize the MYC therapy patent landscape and emphasize the potential of MYC as a druggable target, using herbal medicine modulators. Finally, we describe pending challenges and future perspectives in biomedical research, involving the development of therapeutic approaches to modulate MYC or its targeted genes. Patients with cancers driven by MYC signaling may benefit from therapies targeting these pathways, which could delay cancerous growth and recover antitumor immune responses.

Integrated Analysis of Single-Cell RNA-Seq and Bulk RNA-Seq Unravels the Molecular Feature of Tumor-Associated Macrophage of Acute Myeloid Leukemia

Background

The association between acute myeloid leukemia (AML) and macrophage remains to be deeply explored.

Methods

Gene expression profiles and clinical variable characteristics of AML patients were collected from TCGA, GEO, and TARGET databases. Consensus clustering was employed to construct the macrophage-related clusters. The macrophage-related index (MRI) was constructed using the LASSO and multivariate Cox analysis. The GSE71014 and TARGET datasets were utilized as external validation sets. Single-cell sequencing data for AML (GSE116256) was adopted to analyze modeled gene expression levels in cells.

Results

Two macrophage-related clusters with different prognostic and immune infiltration characteristics were constructed in AML. Cluster B had a poorer prognosis, more cancer-promoting pathway enrichment, and an immunosuppressive microenvironment. Relied on the MRI, patients of different groups showed different levels of immune infiltration, different mutations, and prognoses. LGALS1 and BCL2A1 may play roles in promoting cancer in AML, while ELANE may have a significant effect on suppressing cancer.

Conclusion

Macrophage-related genes (MRGs) had significant impacts on the occurrence and progression of AML. MRI may better evaluate the prognosis and immune features of AML patients.

BCL-W makes only minor contributions to MYC-driven lymphoma development

The BH3-mimetic drug Venetoclax, a specific inhibitor of anti-apoptotic BCL-2, has had clinical success for the treatment of chronic lymphocytic leukaemia and acute myeloid leukaemia. Attention has now shifted towards related pro-survival BCL-2 family members, hypothesising that new BH3-mimetic drugs targeting these proteins may emulate the success of Venetoclax. BH3-mimetics targeting pro-survival MCL-1 or BCL-XL have entered clinical trials, but managing on-target toxicities is challenging. While increasing evidence suggests BFL-1/A1 is a resistance factor for diverse chemotherapeutic agents and BH3-mimetic drugs in haematological malignancies, few studies have explored the role of BCL-W in the development, expansion, and therapeutic responses of cancer. Previously, we found that BCL-W was not required for the ongoing survival and growth of various established human Burkitt lymphoma and diffuse large B cell lymphoma cell lines. However, questions remained about whether BCL-W impacts lymphoma development. Here, we show that BCL-W appears dispensable for MYC-driven lymphomagenesis, and such tumours arising in the absence of BCL-W show no compensatory changes to BCL-2 family member expression, nor altered sensitivity to BH3-mimetic drugs. These results demonstrate that BCL-W does not play a major role in the development of MYC-driven lymphoma or the responses of these tumours to anti-cancer agents.

Apoptotic cell death in disease-Current understanding of the NCCD 2023

Apoptosis is a form of regulated cell death (RCD) that involves proteases of the caspase family. Pharmacological and genetic strategies that experimentally inhibit or delay apoptosis in mammalian systems have elucidated the key contribution of this process not only to (post-)embryonic development and adult tissue homeostasis, but also to the etiology of multiple human disorders. Consistent with this notion, while defects in the molecular machinery for apoptotic cell death impair organismal development and promote oncogenesis, the unwarranted activation of apoptosis promotes cell loss and tissue damage in the context of various neurological, cardiovascular, renal, hepatic, infectious, neoplastic and inflammatory conditions. Here, the Nomenclature Committee on Cell Death (NCCD) gathered to critically summarize an abundant pre-clinical literature mechanistically linking the core apoptotic apparatus to organismal homeostasis in the context of disease.

Bcl-xL is translocated to the nucleus via CtBP2 to epigenetically promote metastasis

Besides its mitochondria-based anti-apoptotic role, Bcl-xL also travels to the nucleus to promote cancer metastasis by upregulating global histone H3 trimethyl Lys4 (H3K4me3) and TGFβ transcription. How Bcl-xL is translocated into the nucleus and how nuclear Bcl-xL regulates H3K4me3 modification are not understood. Here, we report that C-terminal Binding Protein 2 (CtBP2) binds Bcl-xL via its N-terminus and translocates Bcl-xL into the nucleus. Knockdown of CtBP2 by shRNA decreases the nuclear portion of Bcl-xL and reverses Bcl-xL-induced cell migration and metastasis in mouse models. Furthermore, knockout of CtBP2 suppresses Bcl-xL transcription. The binding between Bcl-xL and CtBP2 is required for their interaction with MLL1, a histone H3K4 methyltransferase. Pharmacologic inhibition of MLL1 enzymatic activity reverses Bcl-xL-induced H3K4me3 and TGFβ mRNA upregulation as well as cell invasion. Moreover, cleavage under targets and release using nuclease (CUT&RUN) coupled with next generation sequencing reveals that H3K4me3 modifications are particularly enriched in the promotor region of genes encoding TGFβ and its signaling pathway in the cancer cells overexpressing Bcl-xL. Altogether, the metastatic function of Bcl-xL is mediated by its interaction with CtBP2 and MLL1.

Therapeutic advancements in targeting BCL-2 family proteins by epigenetic regulators, natural, and synthetic agents in cancer

Cancer is amongst the deadliest and most disruptive disorders, having a much higher death rate than other diseases worldwide. Human cancer rates continue to rise, thereby posing the most significant concerns for medical health professionals. In the last two decades, researchers have gone past several milestones in tackling cancer while gaining insight into the role of apoptosis in cancer or targeting various biomarker tools for prognosis and diagnosis. Apoptosis which is still a topic full of complexities, can be controlled considerably by B-cell lymphoma 2 (BCL-2) and its family members. Therefore, targeting proteins of this family to prevent tumorigenesis, is essential to focus on the pharmacological features of the anti-apoptotic and pro-apoptotic members, which will help to develop and manage this disorder. This review deals with the advancements of various epigenetic regulators to target BCL-2 family proteins, including the mechanism of several microRNAs (miRNAs) and long non-coding RNAs (lncRNAs). Similarly, a rise in natural and synthetic molecules' research over the last two decades has allowed us to acquire insights into understanding and managing the transcriptional alterations that have led to apoptosis and treating various neoplastic diseases. Furthermore, several inhibitors targeting anti-apoptotic proteins and inducers or activators targeting pro-apoptotic proteins in preclinical and clinical stages have been summarized. Overall, agonistic and antagonistic mechanisms of BCL-2 family proteins conciliated by epigenetic regulators, natural and synthetic agents have proven to be an excellent choice in developing cancer therapeutics.

Last but not least: BFL-1 as an emerging target for anti-cancer therapies

BFL-1 is an understudied pro-survival BCL-2 protein. The expression of BFL-1 is reported in many cancers, but it is yet to be clarified whether high transcript expression also always correlates with a pro-survival function. However, recent applications of BH3-mimetics for the treatment of blood cancers identified BFL-1 as a potential resistance factor in this type of cancer. Hence, understanding the role of BFL-1 in human cancers and how its up-regulation leads to therapy resistance has become an area of great clinical relevance. In addition, deletion of the murine homologue of BFL-1, called A1, in mice showed only minimal impacts on the well-being of these animals, suggesting drugs targeting BFL-1 would exhibit limited on-target toxicities. BFL-1 therefore represents a good clinical cancer target. Currently, no effective BFL-1 inhibitors exist, which is likely due to the underappreciation of BFL-1 as a potential target in the clinic and lack of understanding of the BFL-1 protein. In this review, the roles of BFL-1 in the development of different types of cancers and drug resistant mechanisms are discussed and some recent advances in the generation of BFL-1 inhibitors highlighted.

Chk1 inhibitor-induced DNA damage increases BFL1 and decreases BIM but does not protect human cancer cell lines from Chk1 inhibitor-induced apoptosis

V158411 is a potent, selective Chk1 inhibitor currently in pre-clinical development. We utilised RNA-sequencing to evaluate the gene responses to V158411 treatment. BCL2A1 was highly upregulated in U2OS cells in response to V158411 treatment with BCL2A1 mRNA increased > 400-fold in U2OS but not HT29 cells. Inhibitors of Chk1, Wee1 and topoisomerases but not other DNA damaging agents or inhibitors of ATR, ATM or DNA-PKcs increased BFL1 and decreased BIM protein. Increased BFL1 appeared limited to a subset of approximately 35% of U2OS cells. Out of 24 cell lines studied, U2OS cells were unique in being the only cell line with low basal BFL1 levels to be increased in response to DNA damage. Induction of BFL1 in U2OS cells appeared dependent on PI3K/AKT/mTOR/MEK pathway signalling but independent of NF-κB transcription factors. Inhibitors of MEK, mTOR and PI3K effectively blocked the increase in BFL1 following V15841 treatment. Increased BFL1 expression did not block apoptosis in U2OS cells in response to V158411 treatment and cells with high basal expression of BFL1 readily underwent caspase-dependent apoptosis following Chk1 inhibitor therapy. BFL1 induction in response to Chk1 inhibition appeared to be a rare event that was dependent on MEK/PI3K/AKT/mTOR signalling.

Bcl-2-like protein-10 increases aggressive features of melanoma cells

Aim:

B-cell lymphoma-2 (Bcl-2)-like protein-10 (Bcl2L10) is the less studied member of Bcl-2 family proteins, with the controversial role in different cancer histotypes. Very recently, Bcl2L10 expression in melanoma tumor specimens and its role in melanoma response to therapy have been demonstrated. Here, the involvement of Bcl2L10 on the in vitro and in vivo properties associated with melanoma aggressive features has been investigated.

Methods:

Endogenous Bcl2L10 protein expression was detected by western blotting analysis in a panel of patient-derived and commercially available human melanoma cells. In vitro assays to evaluate clonogenicity, cell proliferation, cell migration, cell invasion, and in vitro capillary-like structure formation [vasculogenic mimicry (VM)] have been performed by using human melanoma cells stably overexpressing Bcl2L10 or transiently transfected for loss/gain function of Bcl2L10, grown under two- or three-dimensional (3D) conditions Xenograft melanoma model was employed to evaluate in vivo tumor growth and angiogenesis.

Results:

Results demonstrated that Bcl2L10 acts as an inducer of in vitro cell migration, invasion, and VM, while in vitro cell proliferation, in vivo tumor growth, as well as colony formation properties were not affected. Dissecting different signaling pathways, it was found that Bcl2L10 positively affects the phosphorylation of extracellular-signal-regulated kinase (ERK) and the expression of markers of cell invasion, such as urokinase plasminogen activator receptor (uPAR) and matrix metalloproteinases (MMPs). Of note, Bcl2L10-dependent in vitro migration, invasion, and VM are linked to uPAR. Bcl2L10 also negatively regulates the intracellular calcium level. Finally, reduced invasion capability in 3D spheroid invasion assay of melanoma cells transiently overexpressing Bcl2L10 was observed after treatment with inhibitors of MMPs and uPAR.

Conclusions:

Overall, data reported in this paper provide evidence supporting a positive role of Bcl2L10 in melanoma aggressive features.

Targeting the BCL-2-regulated apoptotic pathway for the treatment of solid cancers

The deregulation of apoptosis is a key contributor to tumourigenesis as it can lead to the unwanted survival of rogue cells. Drugs known as the BH3-mimetics targeting the pro-survival members of the BCL-2 protein family to induce apoptosis in cancer cells have achieved clinical success for the treatment of haematological malignancies. However, despite our increasing knowledge of the pro-survival factors mediating the unwanted survival of solid tumour cells, and our growing BH3-mimetics armamentarium, the application of BH3-mimetic therapy in solid cancers has not reached its full potential. This is mainly attributed to the need to identify clinically safe, yet effective, combination strategies to target the multiple pro-survival proteins that typically mediate the survival of solid tumours. In this review, we discuss current and exciting new developments in the field that has the potential to unleash the full power of BH3-mimetic therapy to treat currently recalcitrant solid malignancies.

BH3 Mimetics in Hematologic Malignancies

Hematologic malignancies (HM) comprise diverse cancers of lymphoid and myeloid origin, including lymphomas (approx. 40%), chronic lymphocytic leukemia (CLL, approx. 15%), multiple myeloma (MM, approx. 15%), acute myeloid leukemia (AML, approx. 10%), and many other diseases. Despite considerable improvement in treatment options and survival parameters in the new millennium, many patients with HM still develop chemotherapy-refractory diseases and require re-treatment. Because frontline therapies for the majority of HM (except for CLL) are still largely based on classical cytostatics, the relapses are often associated with defects in DNA damage response (DDR) pathways and anti-apoptotic blocks exemplified, respectively, by mutations or deletion of the TP53 tumor suppressor, and overexpression of anti-apoptotic proteins of the B-cell lymphoma 2 (BCL2) family. BCL2 homology 3 (BH3) mimetics represent a novel class of pro-apoptotic anti-cancer agents with a unique mode of action—direct targeting of mitochondria independently of TP53 gene aberrations. Consequently, BH3 mimetics can effectively eliminate even non-dividing malignant cells with adverse molecular cytogenetic alterations. Venetoclax, the nanomolar inhibitor of BCL2 anti-apoptotic protein has been approved for the therapy of CLL and AML. Numerous venetoclax-based combinatorial treatment regimens, next-generation BCL2 inhibitors, and myeloid cell leukemia 1 (MCL1) protein inhibitors, which are another class of BH3 mimetics with promising preclinical results, are currently being tested in several clinical trials in patients with diverse HM. These pivotal trials will soon answer critical questions and concerns about these innovative agents regarding not only their anti-tumor efficacy but also potential side effects, recommended dosages, and the optimal length of therapy as well as identification of reliable biomarkers of sensitivity or resistance. Effective harnessing of the full therapeutic potential of BH3 mimetics is a critical mission as it may directly translate into better management of the aggressive forms of HM and could lead to significantly improved survival parameters and quality of life in patients with urgent medical needs.

MYC: a multipurpose oncogene with prognostic and therapeutic implications in blood malignancies

MYC oncogene is a transcription factor with a wide array of functions affecting cellular activities such as cell cycle, apoptosis, DNA damage response, and hematopoiesis. Due to the multi-functionality of MYC, its expression is regulated at multiple levels. Deregulation of this oncogene can give rise to a variety of cancers. In this review, MYC regulation and the mechanisms by which MYC adjusts cellular functions and its implication in hematologic malignancies are summarized. Further, we also discuss potential inhibitors of MYC that could be beneficial for treating hematologic malignancies.

HOXA9 promotes MYC-mediated leukemogenesis by maintaining gene expression for multiple anti-apoptotic pathways

HOXA9 is often highly expressed in leukemias. However, its precise roles in leukemogenesis remain elusive. Here, we show that HOXA9 maintains gene expression for multiple anti-apoptotic pathways to promote leukemogenesis. In MLL fusion-mediated leukemia, MLL fusion directly activates the expression of MYC and HOXA9. Combined expression of MYC and HOXA9 induced leukemia, whereas single gene transduction of either did not, indicating a synergy between MYC and HOXA9. HOXA9 sustained expression of the genes implicated in the hematopoietic precursor identity when expressed in hematopoietic precursors, but did not reactivate it once silenced. Among the HOXA9 target genes, BCL2 and SOX4 synergistically induced leukemia with MYC. Not only BCL2, but also SOX4 suppressed apoptosis, indicating that multiple anti-apoptotic pathways underlie cooperative leukemogenesis by HOXA9 and MYC. These results demonstrate that HOXA9 is a crucial transcriptional maintenance factor that promotes MYC-mediated leukemogenesis, potentially explaining why HOXA9 is highly expressed in many leukemias.

Correlation Between BCL2 and Mcl1 Single Nucleotide Polymorphisms and Chemotherapy Response in Jordanian Patients with Colorectal Cancer

BACKGROUND

Colorectal cancer is one of the most common types of cancer worldwide and a leading cause of death in Jordan. BCL-2 and MCL-1 are anti-apoptotic proteins that inhibit programmed cell death and their over-expression has been shown to be associated with reduced sensitivity to chemotherapy and poor survival in cancer patients.

OBJECTIVES

In the present study, three SNPs in the promoter region of antiapoptotic genes were investigated in an effort to inspect the occurrences of SNPs (rs2279115, rs4987852) in the promoter region of BCL2 and SNP (rs9803935) in the promoter region of MCL1 in Jordanian patients with CRC, and investigate correlations between BCL2 and MCL1 SNPs and clinical outcomes.

METHODS

PCR-restriction fragment length polymorphism (RFLP)-based analysis was used for samples genotyping.

RESULTS

The BCL2 rs2279115 and MCL1 rs9803935 SNPs showed significant distribution where mutant and hetero genotypes are more prominent in CRC patients. Additionally, the rs2279115 genotypes and alleles were associated with stages of disease, its recurrence and metastasis. The MCL1 rs9803935 genotypes were associated disease metastasis. However, for BCL2 rs4987852 SNP, there was no association of genotypes or alleles with any of the disease variables.

CONCLUSION

The BCL2 SNPs (rs2279115) and MCL1 SNP (rs9803935) present as important determinants of the progress of CRC in Jordanian patients.

Inhibitors of BCL2A1/Bfl-1 protein: Potential stock in cancer therapy

The Bcl-2 family members rigorously regulate cell endogenous apoptosis, and targeting anti-apoptotic members is a hot topic in design of anti-cancer drugs. At present, FDA and EMA have approved Bcl-2 inhibitor Venetoclax (ABT-199) for treating chronic lymphocytic leukemia (CLL). However, inhibitors of anti-apoptotic protein BCL2A1/Bfl-1 have not been vigorously developed, and no molecule with ideal activity and selectivity has been found yet. Here we review the biological function and protein structure of Bfl-1, discuss the therapeutic potential and list the currently reported inhibitory peptides and small molecules. This will provide a reference for Bfl-1 targeting drug discovery in the future.

Berberine Exerts Anti-cancer Activity by Modulating Adenosine Monophosphate- Activated Protein Kinase (AMPK) and the Phosphatidylinositol 3-Kinase/ Protein Kinase B (PI3K/AKT) Signaling Pathways

Background

The antagonistic relationship between adenosine monophosphate-activated protein kinase (AMPK) and phosphatidylinositol 3-kinase/protein kinase B (PI3K/AKT) signaling play a vital role in cancer development. The anti-cancer effects of berberine have been reported as a main component of the traditional Chinese medicine Rhizoma coptidis, although the roles of these signaling pathways in these effects have not been systematically reviewed.

METHODS

We searched the PubMed database for studies with keywords including ["berberine"] and ["tumor" or "cancer"] and ["AMPK"] or ["AKT"] published between January 2010 and July 2020, to elucidate the roles of the AMPK and PI3K/AKT pathways and their upstream and downstream targets in the anti-cancer effects of berberine.

RESULTS

The anti-cancer effects of berberine include inhibition of cancer cell proliferation, promotion of apoptosis and autophagy in cancer cells, and prevention of metastasis and angiogenesis. The mechanism of these effects involves multiple cell kinases and signaling pathways, including activation of AMPK and forkhead box transcription factor O3a (FOXO3a), accumulation of reactive oxygen species (ROS), and inhibition of the activity of PI3K/AKT, rapamycin (mTOR) and nuclear factor-κB (NF-κB). Most of these mechanisms converge on regulation of the balance of AMPK and PI3K/AKT signaling by berberine.

CONCLUSION

This evidence supports the possibility that berberine is a promising anti-cancer natural product, with pharmaceutical potential in inhibiting cancer growth, metastasis and angiogenesis via multiple pathways, particularly by regulating the balance of AMPK and PI3K/AKT signaling. However, systematic preclinical studies are still required to provide scientific evidence for further clinical studies.

Combination of PKCδ Inhibition with Conventional TKI Treatment to Target CML Models

Simple Summary

The tyrosine kinase inhibitor (TKI) imatinib was the first targeted therapy to show clinical efficacy against chronic myeloid leukemia (CML) through inhibition of the breakpoint cluster region–Abelson murine leukemia viral oncogene homolog (BCR-ABL), which is responsible for the disease. Two other generations of TKIs have succeeded imatinib, offering additional therapeutic solutions for a growing number of patients with imatinib-resistant CML. However, these clinical approaches although very effective, generate many unwanted side effects because of their daily administration. Attempts to stop TKI when the disease is no longer detectable at the molecular level, unfortunately result in relapses in more than half of cases. This highlights the presence of undetectable leukemia cells, recognized as leukemic stem cells (LSCs) that are TKI insensitive. It therefore appears necessary to identify new biochemical pathways in LSCs, the targeting of which would make re-sensitization to TKIs possible. The results presented here demonstrate that targeting the protein kinase Cδ (PKCδ) pathway represents a valid alternative for LSC elimination.

Abstract

Numerous combinations of signaling pathway blockades in association with tyrosine kinase inhibitor (TKI) treatment have been proposed for eradicating leukemic stem cells (LSCs) in chronic myeloid leukemia (CML), but none are currently clinically available. Because targeting protein kinase Cδ (PKCδ) was demonstrated to eliminate cancer stem cells (CSCs) in solid tumors, we evaluated the efficacy of PKCδ inhibition in combination with TKIs for CML cells. We observed that inhibition of PKCδ by a pharmacological inhibitor, by gene silencing, or by using K562 CML cells expressing dominant-negative (DN) or constitutively active (CA) PKCδ isoforms clearly points to PKCδ as a regulator of the expression of the stemness regulator BMI1. As a consequence, inhibition of PKCδ impaired clonogenicity and cell proliferation for leukemic cells. PKCδ targeting in K562 and LAMA-84 CML cell lines clearly enhanced the apoptotic response triggered by any TKI. A strong synergism was observed for apoptosis induction through an increase in caspase-9 and caspase-3 activation and significantly decreased expression of the Bcl-xL Bcl-2 family member. Inhibition of PKCδ did not modify BCR-ABL phosphorylation but acted downstream of the oncogene by downregulating BMI1 expression, decreasing clonogenicity. PKCδ inhibition interfered with the clonogenicity of primary CML CD34⁺ and BCR-ABL-transduced healthy CD34⁺ cells as efficiently as any TKI while it did not affect differentiation of healthy CD34⁺ cells. LTC-IC experiments pinpointed that PKCδ inhibition strongly decreased the progenitors/LSCs frequency. All together, these results demonstrate that targeting of PKCδ in combination with a conventional TKI could be a new therapeutic opportunity to affect for CML cells.

Co-Operativity between MYC and BCL-2 Pro-Survival Proteins in Cancer

B-Cell Lymphoma 2 (BCL-2), c-MYC and related proteins are arguably amongst the most widely studied in all of biology. Every year there are thousands of papers reporting on different aspects of their biochemistry, cellular and physiological mechanisms and functions. This plethora of literature can be attributed to both proteins playing essential roles in the normal functioning of a cell, and by extension a whole organism, but also due to their central role in disease, most notably, cancer. Many cancers arise due to genetic lesions resulting in deregulation of both proteins, and indeed the development and survival of tumours is often dependent on co-operativity between these protein families. In this review we will discuss the individual roles of both proteins in cancer, describe cancers where co-operativity between them has been well-characterised and finally, some strategies to target these proteins therapeutically.

Increased level of long non coding RNA H19 is correlated with the downregulation of miR-326 and BCL-2 genes in pediatric acute lymphoblastic leukemia, a possible hallmark for leukemogenesis

Long non-coding RNAs (lncRNAs) and their role in competitive endogenous RNA (ceRNA) networks have emerged as fundamental debates in the biological processes of initiation and progression of cancer. This study aimed to identify and measure the expression levels of relevant ceRNA regulatory genes contributing to acute lymphoblastic leukemia (ALL). lncRNA H19 and BCL-2 mRNA were chosen based on in silico studies and their interactions with miR-326. Subsequently, the aforementioned coding/non-coding gene expression profiles were measured using qRT-PCR in 50 bone marrow samples, including 33 cases with pediatric ALL and 17 controls with no evidence of malignancy. lncRNA H19 was identified as an oncogenic factor which was noticeably increased in the newly diagnosed patients (P = 0.0019, AUC = 0.84) and negatively associated with miR-326 (r = -0.6, P = 0.02). Furthermore, a negative correlation was introduced between the transcriptional levels of miR-326 and the anti-apoptotic BCL-2 gene (r = -0.6, P = 0.028). The novel experimental and bioinformatic results achieved in this study may provide new insights into the molecular leukemogenesis of pediatric ALL.

Chronic Myeloid Leukemia: A Model Disease of the Past, Present and Future

Chronic myeloid leukemia (CML) has been a "model disease" with a long history. Beginning with the first discovery of leukemia and the description of the Philadelphia Chromosome and ending with the current goal of achieving treatment-free remission after targeted therapies, we describe here the journey of CML, focusing on molecular pathways relating to signaling, metabolism and the bone marrow microenvironment. We highlight current strategies for combination therapies aimed at eradicating the CML stem cell; hopefully the final destination of this long voyage.

DNA Methylation Clusters and Their Relation to Cytogenetic Features in Pediatric AML

Acute Myeloid Leukemia (AML) is characterized by recurrent genetic and cytogenetic lesions that are utilized for risk stratification and for making treatment decisions. In recent years, methylation dysregulation has been extensively studied and associated with risk groups and prognosis in adult AML, however, such studies in pediatric AML are limited. Moreover, the mutations in epigenetic genes such as DNMT3A, IDH1 or IDH2 are almost absent or rare in pediatric patients as compared to their abundance in adult AML. In the current study, we evaluated methylation patterns that occur with or independent of the well-defined cytogenetic features in pediatric AML patients enrolled on multi-site AML02 clinical trial (NCT00136084). Our results demonstrate that unlike adult AML, cytosine DNA methylation does not result in significant unique clusters in pediatric AML, however, DNA methylation signatures correlated significantly with the most common and recurrent cytogenetic features. Paired evaluation of DNA methylation and expression identified genes and pathways of biological relevance that hold promise for novel therapeutic strategies. Our results further demonstrate that epigenetic signatures occur complimentary to the well-established chromosomal/mutational landscape, implying that dysregulation of oncogenes or tumor suppressors might be leveraging both genetic and epigenetic mechanisms to impact biological pathways critical for leukemogenesis.

High-level MYC expression associates with poor survival in patients with acute myeloid leukemia and collaborates with overexpressed p53 in leukemic transformation in patients with myelodysplastic syndrome

INTRODUCTION

Patients with mutated and overexpressed p53 have an aggressive course in acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS). Studies on the impact of MYC expression in AML are limited. This is the first study to evaluate MYC expression and p53 status in AML and MDS.

METHODS

We identified 214 patients, 101 AML, 79 MDS, and 34 negative control patients. We retrospectively assessed p53 and MYC expression by immunohistochemistry and correlated MYC expression with p53 expression and aberrational status of TP53.

RESULTS

The level of both p53 and MYC expression was significantly higher in AML (mean: 9.7%; 12.1%) and MDS (mean: 5.2%; 5.5%) patients compared with control cases (mean: 0.18%; 2.3%; P = .001-0.02). p53 and MYC expression levels were even more elevated in AML when compared to MDS patients (P < .001). MYC expression was significantly associated with p53 expression and TP53 aberration in AML patients but not in MDS patients (P < .001). p53 expression and >20% MYC expression showed an adverse impact on overall survival (OS) (P < .05) in AML patients while p53 but not MYC expression showed an adverse impact on OS in MDS patients. MYC and p53 dual expression, as well as combined MYC expression and TP53 aberration, showed negative impact on OS in AML patients. MDS patients with leukemic transformation revealed an interval increase in expression of both p53 and MYC.

CONCLUSION

High-level MYC expression associates with p53 abnormality and poor survival in AML. MYC may provide proliferative advantage for leukemic progression in p53 dependent and independent manner.

Targeting of BCL-2 Family Members during Anticancer Treatment: A Necessary Compromise between Individual Cell and Ecosystemic Responses?

The imbalance between BCL-2 homologues and pro-death counterparts frequently noted in cancer cells endows them with a cell autonomous survival advantage. To eradicate ectopic cells, inhibitors of these homologues (BH3 mimetics) were developed to trigger, during anticancer treatment, full activation of the canonical mitochondrial apoptotic pathway and related caspases. Despite efficiency in some clinical settings, these compounds do not completely fulfill their initial promise. We herein put forth that a growing body of evidence indicates that mitochondrial integrity, controlled by BCL-2 family proteins, and downstream caspases regulate other cell death modes and influence extracellular signaling by committed cells. Moreover, intercellular communications play a key role in spreading therapeutic response across cancer cell populations and in engaging an immune response. We thus advocate that BH3 mimetics administration would be more efficient in the long term if it did not induce apoptosis in all sensitive cells at the same time, but if it could instead allow (or trigger) death signal production by non-terminally committed dying cell populations. The development of such a trade-off strategy requires to unravel the effects of BH3 mimetics not only on each individual cancer cell but also on homotypic and heterotypic cell interactions in dynamic tumor ecosystems.

Ubiquilin Networking in Cancers

Ubiquilins or UBQLNs, members of the ubiquitin-like and ubiquitin-associated domain (UBL-UBA) protein family, serve as adaptors to coordinate the degradation of specific substrates via both proteasome and autophagy pathways. The UBQLN substrates reveal great diversity and impact a wide range of cellular functions. For decades, researchers have been attempting to uncover a puzzle and understand the role of UBQLNs in human cancers, particularly in the modulation of oncogene's stability and nucleotide excision repair. In this review, we summarize the UBQLNs' genetic variants that are associated with the most common cancers and also discuss their reliability as a prognostic marker. Moreover, we provide an overview of the UBQLNs networks that are relevant to cancers in different ways, including cell cycle, apoptosis, epithelial-mesenchymal transition, DNA repairs and miRNAs. Finally, we include a future prospective on novel ubiquilin-based cancer therapies.

BCL-w: apoptotic and non-apoptotic role in health and disease

The BCL-2 family of proteins integrates signals that trigger either cell survival or apoptosis. The balance between pro-survival and pro-apoptotic proteins is important for tissue development and homeostasis, while impaired apoptosis contributes to several pathologies and can be a barrier against effective treatment. BCL-w is an anti-apoptotic protein that shares a sequence similarity with BCL-X_L, and exhibits a high conformational flexibility. BCL-w level is controlled by a number of signaling pathways, and the repertoire of transcriptional regulators largely depends on the cellular and developmental context. As only a few disease-relevant genetic alterations of BCL2L2 have been identified, increased levels of BCL-w might be a consequence of abnormal activation of signaling cascades involved in the regulation of BCL-w expression. In addition, BCL-w transcript is a target of a plethora of miRNAs. Besides its originally recognized pro-survival function during spermatogenesis, BCL-w has been envisaged in different types of normal and diseased cells as an anti-apoptotic protein. BCL-w contributes to survival of senescent and drug-resistant cells. Its non-apoptotic role in the promotion of cell migration and invasion has also been elucidated. Growing evidence indicates that a high BCL-w level can be therapeutically relevant in neurodegenerative disorders, neuron dysfunctions and after small intestinal resection, whereas BCL-w inhibition can be beneficial for cancer patients. Although several drugs and natural compounds can bi-directionally affect BCL-w level, agents that selectively target BCL-w are not yet available. This review discusses current knowledge on the role of BCL-w in health, non-cancerous diseases and cancer.

Glucocorticoids uncover a critical role for ASH2L on BCL-X expression regulation in leukemia cells

Targeting the apoptosis machinery is a promising therapeutic approach in myeloid malignancies. BCL2L1 is a well-known glucocorticoid-responsive gene and a key apoptosis regulator that, when over-expressed, can contribute to tumor development, progression and therapeutic resistance. Moreover, synthetic glucocorticoids, like dexamethasone, are frequently used in the treatment of hematopoietic diseases due to its pro-apoptotic properties. We report here that the trithorax protein ASH2L, considered one of the core subunits of H3K4-specific MLL/SET methyltransferase complexes, contributes to anti-apoptotic BCL-X_L over-expression and cell survival in patient-derived myeloid leukemia cells. We find that the unliganded glucocorticoid receptor (uGR) and ASH2L interact in a common protein complex through a chromatin looping determined by uGR and ASH2L binding to BCL2L1 specific +58 HRE and promoter region, respectively. Upon addition of dexamethasone, GR and ASH2L recruitment is reduced, BCL-X_L expression diminishes and apoptosis is induced consequently. Overall, our findings indicate that uGR and ASH2L may act as key regulatory players of BCL- X_L upregulation in AML cells.

GCN5 HAT inhibition reduces human Burkitt lymphoma cell survival through reduction of MYC target gene expression and impeding BCR signaling pathways

GCN5, the catalytic subunit in the acetyltransferase modules of SAGA and ATAC, functions as a coactivator of gene transcription. The SAGA complex is recruited to chromatin by transcription factors such as MYC and E2F1 to facilitate acetylation of histones, especially H3 at lysine 9 (H3K9). Burkitt lymphoma is an aggressive subtype of Non-Hodgkin lymphoma driven by the overexpression of MYC. Comparison of GCN5 expression in normal human B cells versus human Burkitt Lymphoma cell lines indicates overexpression of GCN5 in lymphoma. Treatment of Burkitt lymphoma cell lines with a specific inhibitor indicates that decreased GCN5 HAT activity reduces viability and proliferation of these cells. Inhibition of GCN5 HAT activity also induces apoptosis in lymphoma cells. Expression of MYC target genes as well as genes associated with B cell receptor signaling are significantly downregulated upon inhibition of GCN5 enzymatic activity. This downregulation leads to diminished PI3K signaling, a critical pathway in lymphomagenesis. Our data indicate that inhibition of GCN5 HAT activity reduces the tumorigenic properties of human Burkitt lymphoma cells by attenuating BCR signaling and that GCN5 may be a viable target for lymphoma drug therapy.

Cellular demolition: Proteins as molecular players of programmed cell death

Apoptosis, a well-characterized and regulated cell death programme in eukaryotes plays a fundamental role in developing or later-life periods to dispose of unwanted cells to maintain typical tissue architecture, homeostasis in a spatiotemporal manner. This silent cellular death occurs without affecting any neighboring cells/tissue and avoids triggering of immunological response. Furthermore, diminished forms of apoptosis result in cancer and autoimmune diseases, whereas unregulated apoptosis may also lead to the development of a myriad of neurodegenerative diseases. Unraveling the mechanistic events in depth will provide new insights into understanding physiological control of apoptosis, pathological consequences of abnormal apoptosis and development of novel therapeutics for diseases. Here we provide a brief overview of molecular players of programmed cell death with discussion on the role of caspases, modifications, ubiquitylation in apoptosis, removal of the apoptotic body and its relevance to diseases.

The PKR-Like Endoplasmic Reticulum Kinase Promotes the Dissemination of Myc-Induced Leukemic Cells

Hyperactive oncogenic Myc stimulates protein synthesis that induces the unfolded protein response, which requires the function of the eukaryotic translation initiation factor 2-alpha kinase 3, also known as protein kinase R (PKR)-like endoplasmic reticulum kinase (PERK). Activated PERK acts to limit mRNA translation, enable proper protein folding, and restore the homeostasis in the endoplasmic reticulum. Given that Myc activation contributes to many types of lymphoid and myeloid human leukemias, we used a mouse model to examine the importance of PERK in development and progression of Myc-induced leukemias. We found that genetic ablation of Perk does not suppress the generation of the leukemic cells in the bone marrow. However, the cell-autonomous Perk deficiency restricts the dissemination of leukemic cells into peripheral blood, lymph nodes, and vital peripheral organs. Whereas the loss of the IFNAR1 chain of type I IFN receptor stimulated leukemia, Perk ablation did not stabilize IFNAR1, suggesting that PERK stimulates the leukemic cells' dissemination in an IFNAR1-independent manner. We discuss the rationale for using PERK inhibitors against Myc-driven leukemias. IMPLICATIONS: The role of PERK in dissemination of Myc-induced leukemic cells demonstrated in this study argues for the use of PERK inhibitors against leukemia progression.

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.

Treatment with DHA Modifies the Response of MDA-MB-231 Breast Cancer Cells and Tumors from nu/nu Mice to Doxorubicin through Apoptosis and Cell Cycle Arrest

Background

Docosahexaenoic acid (DHA) has been shown to reduce growth of breast cancer cells in vitro and in vivo; it may also benefit the action of cytotoxic cancer drugs. The mechanisms for these observations are not completely understood.

Objectives

We sought to explore how pretreatment of MDA-MB-231 breast cancer cells with DHA alters gene expression with doxorubicin (DOX) treatment and confirm that feeding DHA to tumor-bearing nu/nu mice improves the efficacy of DOX.

Methods

MDA-MB-231 cells were subjected to 4 conditions: a control mixture of 40 μM linoleic and 40 μM oleic acid (OALA), DHA (60 μM plus OALA), OALA DOX (0.41 μM), or DHA DOX (plus OALA) and assessed for effects on viability and function. Female nu/nu mice (6 wk old) bearing MDA-MB-231 tumors were randomly assigned to a nutritionally complete diet (20 g ± 2.8 g DHA/100 g diet) containing a polyunsaturated:saturated fat ratio of 0.5, with or without injections 2 times/wk of 5 mg DOX/kg for 4 wk.

Results

Microarray and protein analysis indicated that DHA DOX cells, compared with OALA DOX, had upregulated expression of apoptosis genes, Caspase-10 (1.3-fold), Caspase-9 (1.4-fold), and Receptor (TNFRSF)-interacting serine-threonine kinase 1 (RIPK1) (1.2-fold), while downregulating cell cycle genes, Cyclin B1 (-2.1-fold), WEE1 (-1.6-fold), and cell division cycle 25 homolog C (CDC25C) (-1.8-fold) (P < 0.05). DHA DOX-treated mice had 50% smaller tumors than control mice (P < 0.05). Analysis of proapoptotic proteins from tumors of DHA DOX mice showed increased Caspase-10 (by 68%) and BH3 interacting domain death agonist (Bid) (by 50%), decreased B-cell CLL/lymphoma 2 (BCL2) (by 24%), and decreased cell cycle proteins Cyclin B1 and Cdc25c (both by 42%), compared with control mice (P < 0.05).

Conclusions

Supplementation with DHA facilitates the action of DOX in MDA-MB-231 cells and in nu/nu mice, which may occur via amplification of the effect of DOX on apoptosis and cell cycle genes.

Differential effects of Vav-promoter-driven overexpression of BCLX and BFL1 on lymphocyte survival and B cell lymphomagenesis

Overexpression of BCLX and BFL1/A1 has been reported in various human malignancies and is associated with poor prognosis and drug resistance, identifying these prosurvival BCL2 family members as putative drug targets. We have generated transgenic mice that express human BFL1 or human BCLX protein throughout the haematopoietic system under the control of the Vav gene promoter. Haematopoiesis is normal in both the Vav-BFL1 and Vav-BCLX transgenic (TG) mice and susceptibility to spontaneous haematopoietic malignancies is not increased. Lymphoid cells from Vav-BCLX TG mice exhibit increased resistance to apoptosis in vitro while most blood cell types form Vav-BFL1 TG mice were poorly protected. Both transgenes significantly accelerated lymphomagenesis in Eμ-MYC TG mice and, surprisingly, the Vav-BFL1 transgene was the more potent. Unexpectedly, expression of transgenic BFL1 RNA and protein is significantly elevated in B lymphoid cells of Vav-BFL1/Eμ-MYC double-transgenic compared to Vav-BFL1 mice, even during the preleukaemic phase, providing a rationale for the potent synergy. In contrast, Vav-BCLX expression was not notably different. These mouse models of BFL1 and BCLX overexpression in lymphomas should be useful tools for the testing the efficacy of novel human BFL1- and BCLX-specific inhibitors.

The Antiarrhythmic Drug, Amiodarone, Decreases AKT Activity and Sensitizes Human Acute Myeloid Leukemia Cells to Apoptosis by ABT-263

BACKGROUND

Successful treatment of leukemia requires new medications to combat drug resistance, but the development of novel therapies is an arduous and risky endeavor. Repurposing currently approved drugs or those already in clinical development to treat other indications is a more practical approach. Moreover, combinatorial therapeutics are often more efficacious than single agent therapeutics because the former can simultaneously target multiple pathways that mitigate tumor aggressiveness and induce cancer cell death.

MATERIAL AND METHODS

In this study, we combined the class III antiarrhythmic agent amiodarone and the BH3 mimetic ABT-263 based on data from a prior drug screen to assess the degree of apoptotic induction in 2 human leukemia cell lines.

RESULTS

The combination yielded statistically significant increases in apoptosis in both cell lines by downregulating AKT activity and increasing cleaved caspase-3.

CONCLUSIONS

Overall, our findings suggest that combining K⁺ channel blockers with prosurvival Bcl-2 family inhibitors is a promising therapeutic approach in treating leukemia.

Myeloid cell leukemia 1 (MCL-1), an unexpected modulator of protein kinase signaling during invasion

Myeloid cell leukemia-1 (MCL-1), closely related to B-cell lymphoma 2 (BCL-2), has a well-established role in cell survival and has emerged as an important target for cancer therapeutics. We have demonstrated that inhibiting MCL-1 is efficacious in suppressing tumour progression in pre-clinical models of breast cancer and revealed that in addition to its role in cell survival, MCL-1 modulated cellular invasion. Utilizing a MCL-1-specific genetic antagonist, we found two possible mechanisms; firstly MCL-1 directly binds to and alters the phosphorylation of the cytoskeletal remodeling protein, Cofilin, a protein important for cytoskeletal remodeling during invasion, and secondly MCL-1 modulates the levels SRC family kinases (SFKs) and their targets. These data provide evidence that MCL-1 activities are not limited to endpoints of extracellular and intracellular signaling culminating in cell survival as previously thought, but can directly modulate the output of SRC family kinases signaling during cellular invasion. Here we review the pleotropic roles of MCL-1 and discuss the implications of this newly discovered effect on protein kinase signaling for the development of cancer therapeutics.

BCL-W has a fundamental role in B cell survival and lymphomagenesis

Compromised apoptotic signaling is a prerequisite for tumorigenesis. The design of effective therapies for cancer treatment depends on a comprehensive understanding of the mechanisms that govern cell survival. The antiapoptotic proteins of the BCL-2 family are key regulators of cell survival and are frequently overexpressed in malignancies, leading to increased cancer cell survival. Unlike BCL-2 and BCL-XL, the closest antiapoptotic relative BCL-W is required for spermatogenesis, but was considered dispensable for all other cell types. Here, however, we have exposed a critical role for BCL-W in B cell survival and lymphomagenesis. Loss of Bcl-w conferred sensitivity to growth factor deprivation-induced B cell apoptosis. Moreover, Bcl-w loss profoundly delayed MYC-mediated B cell lymphoma development due to increased MYC-induced B cell apoptosis. We also determined that MYC regulates BCL-W expression through its transcriptional regulation of specific miR. BCL-W expression was highly selected for in patient samples of Burkitt lymphoma (BL), with 88.5% expressing BCL-W. BCL-W knockdown in BL cell lines induced apoptosis, and its overexpression conferred resistance to BCL-2 family-targeting BH3 mimetics. Additionally, BCL-W was overexpressed in diffuse large B cell lymphoma and correlated with decreased patient survival. Collectively, our results reveal that BCL-W profoundly contributes to B cell lymphoma, and its expression could serve as a biomarker for diagnosis and aid in the development of better targeted therapies.

Epistatic mutations in PUMA BH3 drive an alternate binding mode to potently and selectively inhibit anti-apoptotic Bfl-1

Overexpression of anti-apoptotic Bcl-2 family proteins contributes to cancer progression and confers resistance to chemotherapy. Small molecules that target Bcl-2 are used in the clinic to treat leukemia, but tight and selective inhibitors are not available for Bcl-2 paralog Bfl-1. Guided by computational analysis, we designed variants of the native BH3 motif PUMA that are > 150-fold selective for Bfl-1 binding. The designed peptides potently trigger disruption of the mitochondrial outer membrane in cells dependent on Bfl-1, but not in cells dependent on other anti-apoptotic homologs. High-resolution crystal structures show that designed peptide FS2 binds Bfl-1 in a shifted geometry, relative to PUMA and other binding partners, due to a set of epistatic mutations. FS2 modified with an electrophile reacts with a cysteine near the peptide-binding groove to augment specificity. Designed Bfl-1 binders provide reagents for cellular profiling and leads for developing enhanced and cell-permeable peptide or small-molecule inhibitors.

MYC and RAF: Key Effectors in Cellular Signaling and Major Drivers in Human Cancer

The prototypes of the human MYC and RAF gene families are orthologs of animal proto-oncogenes that were originally identified as transduced alleles in the genomes of highly oncogenic retroviruses. MYC and RAF genes are now established as key regulatory elements in normal cellular physiology, but also as major cancer driver genes. Although the predominantly nuclear MYC proteins and the cytoplasmic RAF proteins have different biochemical functions, they are functionally linked in pivotal signaling cascades and circuits. The MYC protein is a transcription factor and together with its dimerization partner MAX holds a central position in a regulatory network of bHLH-LZ proteins. MYC regulates transcription conducted by all RNA polymerases and controls virtually the entire transcriptome. Fundamental cellular processes including distinct catabolic and anabolic branches of metabolism, cell cycle regulation, cell growth and proliferation, differentiation, stem cell regulation, and apoptosis are under MYC control. Deregulation of MYC expression by rearrangement or amplification of the MYC locus or by defects in kinase-mediated upstream signaling, accompanied by loss of apoptotic checkpoints, leads to tumorigenesis and is a hallmark of most human cancers. The critically controlled serine/threonine RAF kinases are central nodes of the cytoplasmic MAPK signaling cascade transducing converted extracellular signals to the nucleus for reshaping transcription factor controlled gene expression profiles. Specific mutations of RAF kinases, such as the prevalent BRAF(V600E) mutation in melanoma, or defects in upstream signaling or feedback loops cause decoupled kinase activities which lead to tumorigenesis. Different strategies for pharmacological interference with MYC- or RAF-induced tumorigenesis are being developed and several RAF kinase inhibitors are already in clinical use.

Approach to the diagnosis and treatment of high-grade B-cell lymphomas with MYC and BCL2 and/or BCL6 rearrangements

High-grade B-cell lymphomas (HGBLs) with MYC and BCL2 and/or BCL6 rearrangements, so-called "double-hit" lymphomas (HGBL-DH), are aggressive lymphomas that form a separate provisional entity in the 2016 revised World Health Organization Classification of Lymphoid Tumors. Fluorescence in situ hybridization (FISH) will be required to identify HGBL-DH and will reclassify a subset of diffuse large B-cell lymphomas (DLBCLs) and HGBLs with features intermediate between DLBCL and Burkitt lymphoma into this new category. Identifying patients with HGBL-DH is important because it may change clinical management. This poses a challenge for centers that may not be ready to handle the additional workload and financial burden associated with the increase in requests for FISH testing. Herein, we review the mechanisms of deregulation of these oncogenes. We identify the factors associated with a poor prognosis and those that can guide diagnostic testing. Restricting FISH analysis to the 10% of DLBCL patients who have a germinal center B-cell phenotype and coexpress MYC and BCL2 proteins would be cost-effective and would identify the subset of patients who are at highest risk of experiencing a relapse following conventional therapy. These patients may benefit from intensified chemotherapy regimens or, ideally, should enroll in clinical trials investigating novel regimens.

MYC selects against reduced BCL2A1/A1 protein expression during B cell lymphomagenesis

Rearrangements of MYC or ABL proto-oncogenes lead to deregulated expression of key-regulators of cell cycle and cell survival, thereby constituting important drivers of blood cancer. Members of the BCL-2 family of apoptosis regulators contribute to oncogenic transformation downstream of these oncogenes, but the role of anti-apoptotic BCL2A1/A1 in transformation and drug resistance caused by deregulation of these oncogenes remains enigmatic. Here we analyzed the role of A1 in MYC as well as ABL kinase-driven blood cancer in mice, employing in vivo RNAi. We report that overexpression of either oncogene leads to a significant increase in A1 protein levels in otherwise A1-negative B cell progenitors, indicating a key role downstream of these oncogenes to secure survival during transformation. Knockdown of A1 by RNAi, however, did not impact on tumor latency in v-Abl-driven pre-B-ALL. In contrast, A1 knockdown in premalignant Eμ-MYC mice caused a significant reduction of transgenic pre-B cells without impacting on tumor latency as the emerging lymphomas escaped silencing of A1 expression. These findings identify A1 as a MYC target that can be induced prematurely during B cell development to aid expansion of otherwise cell-death-prone MYC transgenic pre-B cells. Hence, A1 should be considered as a putative drug target in MYC-driven blood cancer.

BCL-B (BCL2L10) is overexpressed in patients suffering from multiple myeloma (MM) and drives an MM-like disease in transgenic mice

Luciano et al. generate transgenic mice expressing the Bcl-B gene under the control of the VH promoter and Eµ enhancer and show that these mice recapitulate the characteristic features of human MM.

Multiple myeloma (MM) evolves from a premalignant condition known as monoclonal gammopathy of undetermined significance (MGUS). However, the factors underlying the malignant transformation of plasmocytes in MM are not fully characterized. We report here that Eµ-directed expression of the antiapoptotic Bcl-B protein in mice drives an MM phenotype that reproduces accurately the human disease. Indeed, with age, Eµ-bcl-b transgenic mice develop the characteristic features of human MM, including bone malignant plasma cell infiltration, a monoclonal immunoglobulin peak, immunoglobulin deposit in renal tubules, and highly characteristic bone lytic lesions. In addition, the tumors are serially transplantable in irradiated wild-type mice, underlying the tumoral origin of the disease. Eµ-bcl-b plasmocytes show increased expression of a panel of genes known to be dysregulated in human MM pathogenesis. Treatment of Eµ-bcl-b mice with drugs currently used to treat patients such as melphalan and VELCADE efficiently kills malignant plasmocytes in vivo. Finally, we find that Bcl-B is overexpressed in plasmocytes from MM patients but neither in MGUS patients nor in healthy individuals, suggesting that Bcl-B may drive MM. These findings suggest that Bcl-B could be an important factor in MM disease and pinpoint Eµ-bcl-b mice as a pertinent model to validate new therapies in MM.

Functional role of DNA mismatch repair gene PMS2 in prostate cancer cells

DNA mismatch repair (MMR) enzymes act as proofreading complexes that maintains genomic integrity and MMR-deficient cells show an increased mutation rate. MMR has also been shown to influence cell signaling and the regulation of tumor development. MMR consists of various genes and includes post-meiotic segregation (PMS) 2 which is a vital component of mutL-alpha. In prostate, the functional role of this gene has never been reported and in this study, our aim was to investigate the effect of PMS2 on growth properties of prostate cancer (PCa) cells. Previous studies have shown PMS2 to be deficient in DU145 cells and this lack of expression was confirmed by Western blotting whereas normal prostatic PWR-1E and RWPE-1 cells expressed this gene. PMS2 effects on various growth properties of DU145 were then determined by creating stable gene transfectants. Interestingly, PMS2 caused decreased cell proliferation, migration, invasion, and in vivo growth; and increased apoptosis as compared to vector control. We further analyzed genes affected by PMS2 expression and observe the apoptosis-related TMS1 gene to be significantly upregulated whereas anti-apoptotic BCL2A1 was downregulated. These results demonstrate a functional role for PMS2 to protect against PCa progression by enhancing apoptosis of PCa cells.

The epigenetic modifier JMJD6 is amplified in mammary tumors and cooperates with c-Myc to enhance cellular transformation, tumor progression, and metastasis

Background

Oncogene overexpression in primary cells often triggers the induction of a cellular safeguard response promoting senescence or apoptosis. Secondary cooperating genetic events are generally required for oncogene-induced tumorigenesis to overcome these biologic obstacles. We employed comparative genomic hybridization for eight genetically engineered mouse models of mammary cancer to identify loci that might harbor genes that enhance oncogene-induced tumorigenesis.

Results

Unlike many other mammary tumor models, the MMTV-Myc tumors displayed few copy number variants except for amplification of distal mouse chromosome 11 in 80 % of the tumors (syntenic to human 17q23-qter often amplified in human breast cancer). Analyses of candidate genes located in this region identified JMJD6 as an epigenetic regulatory gene that cooperates with Myc to enhance tumorigenesis. It suppresses Myc-induced apoptosis under varying stress conditions through inhibition of p19ARF messenger RNA (mRNA) and protein, leading to reduced levels of p53. JMJD6 binds to the p19ARF promoter and exerts its inhibitory function through demethylation of H4R3me2a. JMJD6 overexpression in MMTV-Myc cell lines increases tumor burden, induces EMT, and greatly enhances tumor metastasis. Importantly, we demonstrate that co-expression of high levels of JMJD6 and Myc is associated with poor prognosis for human ER+ breast cancer patients.

Conclusions

A novel epigenetic mechanism has been identified for how JMJD6 cooperates with Myc during oncogenic transformation. Combined high expression of Myc and JMJD6 confers a more aggressive phenotype in mouse and human tumors. Given the pleiotropic pro-tumorigenic activities of JMJD6, it may be useful as a prognostic factor and a therapeutic target for Myc-driven mammary tumorigenesis.

Electronic supplementary material

The online version of this article (doi:10.1186/s13148-016-0205-6) contains supplementary material, which is available to authorized users.

Differential expression of EBV proteins LMP1 and BHFR1 in EBV‑associated gastric and nasopharyngeal cancer tissues

Epstein-Barr virus (EBV) infection is associated with the development of T cell lymphoma, nasopharyngeal cancer (NPC), and EBV-associated gastric cancer (EBVaGC). This study assessed the expression of the EBV-associated proteins latent membrane protein 1 (LMP1) and BamHI-A rightward frame 1 (BARF1) in NPC and EBVaGC tissue specimens and determined their association with clinicopathological data, microvessel density (MVD) and micro-lymphatic vessel density (MLVD). This study collected 600 gastric cancer and 75 NPC tissue samples. EBV infection was assessed using in situ hybridization, and LMP1 and BARF1 expression was assessed using immunohistochemistry. The levels of MVD and MLVD were assessed using immunostaining of vascular endothelial growth factor (VEGF)-C, CD34, and lymphatic vessel endothelial receptor 1 (LYVE-1). Among the 600 gastric cancer cases, 30 were positive for EBV infection, which was shown to be associated with the age of patients (P=0.073), tumor differentiation (P<0.0001), tumor location (P<0.0001) and lymph node metastasis (P<0.0001). In these 30 EBVaGC cases, only one case was weakly positive for LMP1, but 17 cases were BARF1 positive. BARF1 expression was associated with lymph node metastasis of EBVaGC and the level of MLVD. Furthermore, 61 (81%) of 75 NPC patients were EBV positive, among which 38 cases were LMP-1 positive (62.3%) and LMP1 expression was associated with tumor-node-metastasis stage (P=0.011) and lymph node metastasis (P=0.041). MLVD was significantly higher in LMP1-positive cases than LMP1-negative cases. There were only 8 (13.3%) cases positive for BARF1 expression. In conclusion, EBV infection exhibits a role in gastric cancer and NPC development; however, expression of EBV-associated proteins LMP1 and BARF1 have differential functions during tumorigenesis of these two types of cancer.

Murine Stem Cell-Based Retrovirus Production for Marking Primary Mouse Mammary Cells for Metastasis Studies

Since the introduction of retroviral vector technology, permanent genetic marking of cells has considerably contributed to the understanding of different physiological and disease processes in vivo. Recent marking strategies aim to elucidate the contribution of cells on the clonal level, and the advent of fluorescent proteins has opened new avenues for the in vivo analysis of gene-marked cells. Gene-modified cells are easily identifiable (e.g., via the introduced fluorescent protein) within whole organ structures, allowing one to measure the contribution of transduced cells to malignant outgrowth. In our laboratory, we use the tetracycline-inducible system to study oncogene cooperation in metastatic progression. We use bicistronic retroviruses expressing the tetracycline transactivator (tTA) and the candidate gene (MIT-gene) or the tTA alone (MIT-Rx) to infect primary mammary cells from mice harboring tetracycline-inducible transgenes. This allows for constitutive expression of the candidate gene and tTA-dependent expression of the inducible oncogene. We also use MIG-based vectors, which allow for constitutive expression of the candidate gene and a green fluorescent protein. Here we describe how to produce retroviral particles carrying both MIT- and MIG-based vectors. Because of the fragility of the retroviral envelope, we do not attempt to concentrate the virus, and we directly use packaging cell media to infect primary epithelial cells (either normal or tumor). Infected cells can be transplanted into recipient mice to investigate metastatic colonization.

Low expression of pro-apoptotic Bcl-2 family proteins sets the apoptotic threshold in Waldenström macroglobulinemia

Waldenström macroglobulinemia (WM) is a proliferative disorder of IgM-secreting, lymphoplasmacytoid cells that inhabit the lymph nodes and bone marrow. The disease carries a high prevalence of activating mutations in MyD88 (91%) and CXCR4 (28%). Because signaling through these pathways leads to Bcl-xL induction, we examined Bcl-2 family expression in WM patients and cell lines. Unlike other B-lymphocyte-derived malignancies, which become dependent on expression of anti-apoptotic proteins to counter expression of pro-apoptotic proteins, WM samples expressed both pro- and anti-apoptotic Bcl-2 proteins at low levels similar to their normal B-cell and plasma cell counterparts. Three WM cell lines expressed pro-apoptotic Bcl-2 family members Bim or Bax and Bak at low levels, which determined their sensitivity to inducers of intrinsic apoptosis. In two cell lines, miR-155 upregulation, which is common in WM, was responsible for the inhibition of FOXO3a and Bim expression. Both antagonizing miR-155 to induce Bim and proteasome inhibition increased the sensitivity to ABT-737 in these lines indicating a lowering of the apoptotic threshold. In this manner, treatments that increase pro-apoptotic protein expression increase the efficacy of agents treated in combination in addition to direct killing.

Molecular Cell Biology of Apoptosis and Necroptosis in Cancer

Cell death is a major mechanism to eliminate cells in which DNA is damaged, organelles are stressed, or oncogenes are overexpressed, all events that would otherwise predispose cells to oncogenic transformation. The pathways that initiate and execute cell death are complex, genetically encoded, and subject to significant regulation. Consequently, while these pathways are often mutated in malignancy, there is considerable interest in inducing cell death in tumor cells as therapy. This chapter addresses our current understanding of molecular mechanisms contributing to two cell death pathways, apoptotic cell death and necroptosis, a regulated form of necrotic cell death. Apoptosis can be induced by a wide variety of signals, leading to protease activation that dismantles the cell. We discuss the physiological importance of each apoptosis pathway and summarize their known roles in cancer suppression and the current efforts at targeting each pathway therapeutically. The intricate mechanistic link between death receptor-mediated apoptosis and necroptosis is described, as well as the potential opportunities for utilizing necroptosis in the treatment of malignancy.