Regulation of Bcl-XL by non-canonical NF-κB in the context of CD40-induced drug resistance in CLL

IL-33-dependent NF-κB activation inhibits apoptosis and drives chemoresistance in acute myeloid leukemia

BACKGROUND

Despite recent advances in therapeutic regimens, the prognosis of acute myeloid leukemia (AML) remains poor. Following our previous finding that interleukin-33 (IL-33) promotes cell survival along with activated NF-κB in AML, we further investigated the role of NF-κB during leukemia development.

METHODS

Flow cytometry was performed to value the apoptosis and proliferation. qRT-PCR and western blot were performed to detect the expression of IL-6, active caspase 3, BIRC2, Bcl-2, and Bax, as well as activated NF-κB p65 and AKT. Finally, xenograft mouse models and AML patient samples were used to verify the findings observed in AML cell lines.

RESULTS

IL-33-mediated NF-κB activation in AML cell lines contributes to a reduction in apoptosis, an increase in proliferation rate as well as a decrease in drug sensitivity, which were reversed by NF-κB inhibitor, Bay-117085. Moreover, IL-33 decreased the expression of active caspase-3 while increasing the levels of BIRC2, Bcl-2, and Bax, and these effects were blocked by Bay-117085. Additionally, NF-κB activation induced by IL-33 increases the production of IL-6 and autocrine activation of AKT. Co-culture of bone marrow stroma with AML cells resulted in increased IL-33 expression by leukemia cells, along with decreased apoptosis level and reduced drug sensitivity. Finally, we confirmed the in vivo pro-tumor effect mediated by IL-33/ NF-κB axis using a xenograft model of AML.

CONCLUSION

Our data indicate that IL-33/IL1RL1-dependent signaling contributes to AML cell activation of NF-κB, which in turn causes autocrine IL-6-induced activation of pAKT, supporting IL-33/NF-κB/pAKT as a potential target for AML therapy.

Molecular mechanism of co-stimulatory domains in promoting CAR-T cell anti-tumor efficacy

Chimeric antigen receptor (CAR)-engineered T cells have been defined as 'living drug'. Adding a co-stimulatory domain (CSD) has enhanced the anti-hematological effects of CAR-T cells, thereby elevating their viability for medicinal applications. Various CSDs have helped prepare CAR-T cells to study anti-tumor efficacy. Previous studies have described and summarized the anti-tumor efficacy of CAR-T cells obtained from different CSDs. However, the underlying molecular mechanisms by which different CSDs affect CAR-T function have been rarely reported. The role of CSDs in T cells has been significantly studied, but whether they can play a unique role as a part of the CAR structure remains undetermined. Here, we summarized the effects of CSDs on CAR-T signaling pathways based on the limited references and speculated the possible mechanism depending on the specific characteristics of CAR-T cells. This review will help understand the molecular mechanism of CSDs in CAR-T cells that exert different anti-tumor effects while providing potential guidance for further interventions to enhance anti-tumor efficacy in immunotherapy.

Blockage of BCL-XL overcomes venetoclax resistance across BCL2+ lymphoid malignancies irrespective of BIM status

ABSTRACT

Venetoclax (VEN), a B-cell lymphoma 2 (BCL2) inhibitor, has a promising single-agent activity in mantle cell lymphoma (MCL), acute lymphoblastic leukemia (ALL), and large BCLs, but remissions were generally short, which call for rational drug combinations. Using a panel of 21 lymphoma and leukemia cell lines and 28 primary samples, we demonstrated strong synergy between VEN and A1155463, a BCL-XL inhibitor. Immunoprecipitation experiments and studies on clones with knockout of expression or transgenic expression of BCL-XL confirmed its key role in mediating inherent and acquired VEN resistance. Of note, the VEN and A1155463 combination was synthetically lethal even in the cell lines with lack of expression of the proapoptotic BCL2L11/BIM and in the derived clones with genetic knockout of BCL2L11/BIM. This is clinically important because BCL2L11/BIM deletion, downregulation, or sequestration results in VEN resistance. Immunoprecipitation experiments further suggested that the proapoptotic effector BAX belongs to principal mediators of the VEN and A1155463 mode of action in the BIM-deficient cells. Lastly, the efficacy of the new proapoptotic combination was confirmed in vivo on a panel of 9 patient-derived lymphoma xenografts models including MCL (n = 3), B-ALL (n = 2), T-ALL (n = 1), and diffuse large BCL (n = 3). Because continuous inhibition of BCL-XL causes thrombocytopenia, we proposed and tested an interrupted 4 days on/3 days off treatment regimen, which retained the desired antitumor synergy with manageable platelet toxicity. The proposed VEN and A1155463 combination represents an innovative chemotherapy-free regimen with significant preclinical activity across diverse BCL2+ hematologic malignancies irrespective of the BCL2L11/BIM status.

Nuclear factor-κB activation by transforming growth factor-β1 drives tumour microenvironment-mediated drug resistance in neuroblastoma

BACKGROUND

Intrinsic and extrinsic factors in the tumour microenvironment (TME) contribute to therapeutic resistance. Here we demonstrate that transforming growth factor (TGF)-β1 produced in the TME increased drug resistance of neuroblastoma (NB) cells.

METHODS

Human NB cell lines were tested in vitro for their sensitivity to Doxorubicin (DOX) and Etoposide (ETOP) in the presence of tumour-associated macrophages (TAM) and mesenchymal stromal cells/cancer-associated fibroblasts (MSC/CAF). These experiments were validated in xenotransplanted and primary tumour samples.

RESULTS

Drug resistance was associated with an increased expression of efflux transporter and anti-apoptotic proteins. Upregulation was dependent on activation of nuclear factor (NF)-κB by TGF-β-activated kinase (TAK1) and SMAD2. Resistance was reversed upon pharmacologic and genetic inhibitions of NF-κB, and TAK1/SMAD2. Interleukin-6, leukaemia inhibitory factor and oncostatin M were upregulated by this TGF-β/TAK1/NF-κB/SMAD2 signalling pathway contributing to drug resistance via an autocrine loop activating STAT3. An analysis of xenotransplanted NB tumours revealed an increased presence of phospho (p)-NF-κB in tumours co-injected with MSC/CAF and TAM, and these tumours failed to respond to Etoposide but responded if treated with a TGF-βR1/ALK5 inhibitor. Nuclear p-NF-κB was increased in patient-derived tumours rich in TME cells.

CONCLUSIONS

The data provides a novel insight into a targetable mechanism of environment-mediated drug resistance.

Role of the tumor microenvironment in CLL pathogenesis

Chronic lymphocytic leukemia (CLL) cells extensively interact with and depend on their surrounding tumor microenvironment (TME). The TME encompasses a heterogeneous array of cell types, soluble signals, and extracellular vesicles, which contribute significantly to CLL pathogenesis. CLL cells and the TME cooperatively generate a chronic inflammatory milieu, which reciprocally reprograms the TME and activates a signaling network within CLL cells, promoting their survival and proliferation. Additionally, the inflammatory milieu exerts chemotactic effects, attracting CLL cells and other immune cells to the lymphoid tissues. The intricate CLL-TME interactions also facilitate immune evasion and compromise leukemic cell surveillance. We also review recent advances that have shed light on additional aspects that are substantially influenced by the CLL-TME interplay.

Metabolic signature and response to glutamine deprivation are independent of p53 status in B cell malignancies

The tumor suppressor p53 has been described to control various aspects of metabolic reprogramming in solid tumors, but in B cell malignancies that role is as yet unknown. We generated pairs of p53 functional and knockout (KO) clones from distinct B cell malignancies (acute lymphoblastic leukemia, chronic lymphocytic leukemia, diffuse large B cell lymphoma, and multiple myeloma). Metabolomics and isotope tracing showed that p53 loss did not drive a common metabolic signature. Instead, cell lines segregated according to cell of origin. Next, we focused on glutamine as a crucial energy source in the B cell tumor microenvironment. In both TP53 wild-type and KO cells, glutamine deprivation induced cell death through the integrated stress response, via CHOP/ATF4. Lastly, combining BH3 mimetic drugs with glutamine starvation emerged as a possibility to target resistant clones. In conclusion, our analyses do not support a common metabolic signature of p53 deficiency in B cell malignancies and suggest therapeutic options for exploration based on glutamine dependency.

Decreased apoptotic priming and loss of BCL-2 dependence are functional hallmarks of Richter's syndrome

Richter's syndrome (RS) is the transformation of chronic lymphocytic leukemia (CLL) into a high-grade B-cell malignancy. Molecular and functional studies have pointed out that CLL cells are close to the apoptotic threshold and dependent on BCL-2 for survival. However, it remains undefined how evasion from apoptosis evolves during disease transformation. Here, we employed functional and static approaches to compare the regulation of mitochondrial apoptosis in CLL and RS. BH3 profiling of 17 CLL and 9 RS samples demonstrated that RS cells had reduced apoptotic priming and lower BCL-2 dependence than CLL cells. While a subset of RS was dependent on alternative anti-apoptotic proteins and was sensitive to specific BH3 mimetics, other RS cases harbored no specific anti-apoptotic addiction. Transcriptomics of paired CLL/RS samples revealed downregulation of pro-apoptotic sensitizers during disease transformation. Albeit expressed, effector and activator members were less likely to colocalize with mitochondria in RS compared to CLL. Electron microscopy highlighted reduced cristae width in RS mitochondria, a condition further promoting apoptosis resistance. Collectively, our data suggest that RS cells evolve multiple mechanisms that lower the apoptotic priming and shift the anti-apoptotic dependencies away from BCL-2, making direct targeting of mitochondrial apoptosis more challenging after disease transformation.

Comprehensive review of Bcl-2 family proteins in cancer apoptosis: Therapeutic strategies and promising updates of natural bioactive compounds and small molecules

Cancer has a considerably higher fatality rate than other diseases globally and is one of the most lethal and profoundly disruptive ailments. The increasing incidence of cancer among humans is one of the greatest challenges in the field of healthcare. A significant factor in the initiation and progression of tumorigenesis is the dysregulation of physiological processes governing cell death, which results in the survival of cancerous cells. B-cell lymphoma 2 (Bcl-2) family members play important roles in several cancer-related processes. Drug research and development have identified various promising natural compounds that demonstrate potent anticancer effects by specifically targeting Bcl-2 family proteins and their associated signaling pathways. This comprehensive review highlights the substantial roles of Bcl-2 family proteins in regulating apoptosis, including the intricate signaling pathways governing the activity of these proteins, the impact of reactive oxygen species, and the crucial involvement of proteasome degradation and the stress response. Furthermore, this review discusses advances in the exploration and potential therapeutic applications of natural compounds and small molecules targeting Bcl-2 family proteins and thus provides substantial scientific information and therapeutic strategies for cancer management.

Electron transport chain and mTOR inhibition synergistically decrease CD40 signaling and counteract venetoclax resistance in chronic lymphocytic leukemia

CD40 signaling upregulates BCL-XL and MCL-1 expression in the chronic lymphocytic leukemia (CLL) lymph node microenvironment, affording resistance to the BCL-2 inhibitor, venetoclax. Venetoclax resistance in the therapeutic setting and after long-term laboratory selection has been linked to metabolic alterations, but the underlying mechanism(s) are unknown. We aimed here to discover how CD40 stimulation as a model for tumor microenvironment-mediated metabolic changes, affects venetoclax sensitivity/resistance. CD40 stimulation increased oxidative phosphorylation and glycolysis, but only inhibition of oxidative phosphorylation countered venetoclax resistance. Furthermore, blocking mitochondrial import of pyruvate, glutamine or fatty acids affected CLL metabolism, but did not prevent CD40-mediated resistance to venetoclax. In contrast, inhibition of the electron transport chain (ETC) at complex I, III or V attenuated CLL activation and ATP production, and downregulated MCL-1 and BCL-XL, correlating with reduced CD40 surface expression. Moreover, ETC inhibition equaled mTOR1/2 but not mTOR1 inhibition alone for venetoclax resistance, and all three pathways were linked to control of general protein translation. In line with this, ETC plus mTOR inhibition synergistically counteracted venetoclax resistance. These findings link oxidative CLL metabolism to CD40 expression and cellular signaling, and may hold clinical potential.

Signaling via a CD28/CD40 chimeric costimulatory antigen receptor (CoStAR™), targeting folate receptor alpha, enhances T cell activity and augments tumor reactivity of tumor infiltrating lymphocytes

Transfer of autologous tumor infiltrating lymphocytes (TIL) to patients with refractory melanoma has shown clinical efficacy in a number of trials. However, extending the clinical benefit to patients with other cancers poses a challenge. Inefficient costimulation in the tumor microenvironment can lead to T cell anergy and exhaustion resulting in poor anti-tumor activity. Here, we describe a chimeric costimulatory antigen receptor (CoStAR) comprised of FRα-specific scFv linked to CD28 and CD40 intracellular signaling domains. CoStAR signaling alone does not activate T cells, while the combination of TCR and CoStAR signaling enhances T cell activity resulting in less differentiated T cells, and augmentation of T cell effector functions, including cytokine secretion and cytotoxicity. CoStAR activity resulted in superior T cell proliferation, even in the absence of exogenous IL-2. Using an in vivo transplantable tumor model, CoStAR was shown to improve T cell survival after transfer, enhanced control of tumor growth, and improved host survival. CoStAR could be reliably engineered into TIL from multiple tumor indications and augmented TIL activity against autologous tumor targets both in vitro and in vivo. CoStAR thus represents a general approach to improving TIL therapy with synthetic costimulation.

Expression and Activity of the NF-κB Subunits in Chronic Lymphocytic Leukaemia: A Role for RelB and Non-Canonical Signalling

BACKGROUND

Canonical NF-κB signalling by p65 (RelA) confers chemo-resistance and poor survival in chronic lymphocytic leukaemia (CLL). The role of non-canonical NF-κB signalling (leading to RelB and p52 subunit activation) in CLL is less understood, but given its importance in other B-cell tumour types, we theorised that RelB and p52 may also contribute to the pathology of CLL.

METHODS

DNA binding activity of all five NF-kB subunits, p65, p50, RelB, p52, and c-Rel, was quantified using ELISA and correlated to ex vivo chemoresistance, CD40L-stimulated signalling (to mimic the lymph node microenvironment), and clinical data.

RESULTS

Importantly, we show for the first time that high basal levels of RelB DNA binding correlate with nuclear RelB protein expression and are associated with del(11q), ATM dysfunction, unmutated IGHV genes, and shorter survival. High levels of nuclear p65 are prevalent in del(17p) cases (including treatment-naïve patients) and also correlate with the outcome. CD40L-stimulation resulted in rapid RelB activation, phosphorylation and processing of p100, and subsequent CLL cell proliferation.

CONCLUSIONS

These data highlight a role for RelB in driving CLL cell tumour growth in a subset of patients and therefore strategies designed to inhibit non-canonical NF-κB signalling represent a novel approach that will have therapeutic benefit in CLL.

Characterization of the Intraclonal Complexity of Chronic Lymphocytic Leukemia B Cells: Potential Influences of B-Cell Receptor Crosstalk with Other Stimuli

Chronic lymphocytic leukemia (CLL) clones contain subpopulations differing in time since the last cell division ("age"): recently born, proliferative (PF; CXCR4DimCD5Bright), intermediate (IF; CXCR4IntCD5Int), and resting (RF; CXCR4BrightCD5Dim) fractions. Herein, we used deuterium (2H) incorporation into newly synthesized DNA in patients to refine the kinetics of CLL subpopulations by characterizing two additional CXCR4/CD5 fractions, i.e., double dim (DDF; CXCR4DimCD5Dim) and double bright (DBF; CXCR4BrightCD5Bright); and intraclonal fractions differing in surface membrane (sm) IgM and IgD densities. Although DDF was enriched in recently divided cells and DBF in older cells, PF and RF remained the most enriched in youngest and oldest cells, respectively. Similarly, smIgMHigh and smIgDHigh cells were the youngest, and smIgMLow and smIgDLow were the oldest, when using smIG levels as discriminator. Surprisingly, the cells closest to the last stimulatory event bore high levels of smIG, and stimulating via TLR9 and smIG yielded a phenotype more consistent with the in vivo setting. Finally, older cells were less sensitive to in vivo inhibition by ibrutinib. Collectively, these data define additional intraclonal subpopulations with divergent ages and phenotypes and suggest that BCR engagement alone is not responsible for the smIG levels found in vivo, and the differential sensitivity of distinct fractions to ibrutinib might account, in part, for therapeutic relapse.

Role of YY1 in the Regulation of Anti-Apoptotic Gene Products in Drug-Resistant Cancer Cells

Cancer is a leading cause of death among the various diseases encountered in humans. Cancer is not a single entity and consists of numerous different types and subtypes that require various treatment regimens. In the last decade, several milestones in cancer treatments were accomplished, such as specific targeting agents or revitalizing the dormant anti-tumor immune response. These milestones have resulted in significant positive clinical responses as well as tumor regression and the prolongation of survival in subsets of cancer patients. Hence, in non-responding patients and non-responding relapsed patients, cancers develop intrinsic mechanisms of resistance to cell death via the overexpression of anti-apoptotic gene products. In parallel, the majority of resistant cancers have been reported to overexpress a transcription factor, Yin Yang 1 (YY1), which regulates the chemo-immuno-resistance of cancer cells to therapeutic anticancer cytotoxic agents. The relationship between the overexpression of YY1 and several anti-apoptotic gene products, such as B-cell lymphoma 2 protein (Bcl-2), B-cell lymphoma extra-large (Bcl-xL), myeloid cell leukemia 1 (Mcl-1) and survivin, is investigated in this paper. The findings demonstrate that these anti-apoptotic gene products are regulated, in part, by YY1 at the transcriptional, epigenetic, post-transcriptional and translational levels. While targeting each of the anti-apoptotic gene products individually has been examined and clinically tested for some, this targeting strategy is not effective due to compensation by other overexpressed anti-apoptotic gene products. In contrast, targeting YY1 directly, through small interfering RNAs (siRNAs), gene editing or small molecule inhibitors, can be therapeutically more effective and generalized in YY1-overexpressed resistant cancers.

Possible correlated signaling pathways with chronic urate nephropathy: A review

Hyperuricemia nephropathy, also known as gouty nephropathy, refers to renal damage induced by hyperuricemia caused by excessive production of serum uric acid or low excretion of uric acid. the persistence of symptoms will lead to changes in renal tubular phenotype and accelerate the progress of renal fibrosis. The existence and progressive aggravation of symptoms will bring a heavy burden to patients, their families and society, affect their quality of life and reduce their well-being. With the increase of reports on hyperuricemia nephropathy, the importance of related signal pathways in the pathogenesis of hyperuricemia nephropathy is becoming more and more obvious, but most studies are limited to the upper and lower mediating relationship between 1 or 2 signal pathways. The research on the comprehensiveness of signal pathways and the breadth of crosstalk between signal pathways is limited. By synthesizing the research results of signal pathways related to hyperuricemia nephropathy in recent years, this paper will explore the specific mechanism of hyperuricemia nephropathy, and provide new ideas and methods for the treatment of hyperuricemia nephropathy based on a variety of signal pathway crosstalk and personal prospects.

NF-κB fingerprinting reveals heterogeneous NF-κB composition in diffuse large B-cell lymphoma

Introduction

Improving treatments for Diffuse Large B-Cell Lymphoma (DLBCL) is challenged by the vast heterogeneity of the disease. Nuclear factor-κB (NF-κB) is frequently aberrantly activated in DLBCL. Transcriptionally active NF-κB is a dimer containing either RelA, RelB or cRel, but the variability in the composition of NF-κB between and within DLBCL cell populations is not known.

Results

Here we describe a new flow cytometry-based analysis technique termed "NF-κB fingerprinting" and demonstrate its applicability to DLBCL cell lines, DLBCL core-needle biopsy samples, and healthy donor blood samples. We find each of these cell populations has a unique NF-κB fingerprint and that widely used cell-of-origin classifications are inadequate to capture NF-κB heterogeneity in DLBCL. Computational modeling predicts that RelA is a key determinant of response to microenvironmental stimuli, and we experimentally identify substantial variability in RelA between and within ABC-DLBCL cell lines. We find that when we incorporate NF-κB fingerprints and mutational information into computational models we can predict how heterogeneous DLBCL cell populations respond to microenvironmental stimuli, and we validate these predictions experimentally.

Discussion

Our results show that the composition of NF-κB is highly heterogeneous in DLBCL and predictive of how DLBCL cells will respond to microenvironmental stimuli. We find that commonly occurring mutations in the NF-κB signaling pathway reduce DLBCL's response to microenvironmental stimuli. NF-κB fingerprinting is a widely applicable analysis technique to quantify NF-κB heterogeneity in B cell malignancies that reveals functionally significant differences in NF-κB composition within and between cell populations.

Ibrutinib sensitizes CLL cells to venetoclax by interrupting TLR9-induced CD40 upregulation and protein translation

Chronic lymphocytic leukemia (CLL) cells upregulate Bcl-2 proteins within the lymph node (LN) microenvironment. Signaling via B-cell receptor, Toll-like receptors and CD40 collectively reduce sensitivity to the BCL-2 inhibitor venetoclax. Time-limited treatment with venetoclax plus the BTK-inhibitor ibrutinib results in deep remissions, but how this combination affects LN-related signaling is not yet completely clear. Therefore, samples obtained from the HOVON141/VISION phase 2 clinical trial were used to analyze this. Two cycles of lead-in ibrutinib monotherapy resulted in decreased protein expression of Bcl-2 proteins in circulating CLL cells. Strikingly, at this timepoint CD40-induced venetoclax resistance was strongly attenuated, as was expression of CD40. Since CD40 signaling occurs within the CLL LN, we tested various LN-related signals that could affect CD40 signaling. While BCR stimulation had only a minor effect, TLR9 stimulation via CpG led to significantly increased CD40 expression and importantly, reverted the effects of ibrutinib treatment on venetoclax sensitivity by inducing overall protein translation. Together, these findings identify a novel effect of ibrutinib: interruption of TLR9-induced CD40 upregulation and translation of pro-survival proteins. This mechanism may potentially further inhibit priming of CLL cells in the LN microenvironment for venetoclax resistance.

IL-1β stimulates a novel, IKKα -dependent, NIK -independent activation of non-canonical NFκB signalling

In this study, we examined the activation of non-canonical nuclear factor Kappa B (NFκB) signalling in U2OS cells, a cellular metastatic bone cancer model. Whilst Lymphotoxin α1β2 (LTα₁β₂) stimulated the expected slow, delayed, sustained activation of serine 866/870 p100 phosphorylation and increased cellular expression of p52 NFκB, we found that canonical agonists, Interleukin-1β (IL-1β) and also Tumour necrosis factor-α (TNFα) generated a rapid transient increase in pp100, which was maximal by 15-30 min. This rapid phosphorylation was also observed in other cells types, such as DU145 and HCAECs suggesting the phenomenon is universal. IKKα deletion using CRISPR/Cas9 revealed an IKKα-dependent mechanism for serine 866/870 and additionally serine 872 p100 phosphorylation for both IL-1β and LTα₁β₂. In contrast, knockdown of IKKβ using siRNA or pharmacological inhibition of IKKβ activity was without effect on p100 phosphorylation. Pre-incubation of cells with the NFκB inducing-kinase (NIK) inhibitor, CW15337, had no effect on IL-1β induced phosphorylation of p100 however, the response to LTα₁β₂ was virtually abolished. Surprisingly IL-1β also stimulated p52 nuclear translocation as early as 60 min, this response and the concomitant p65 translocation was partially reduced by IKKα deletion. Furthermore, p52 nuclear translocation was unaffected by CW15337. In contrast, the response to LTα₁β₂ was essentially abolished by both IKKα deletion and CW15337. Taken together, these finding reveal novel forms of NFκB non-canonical signalling stimulated by ligands that activate the canonical NFκB pathway strongly such as IL-1β.

Deacetylation induced nuclear condensation of HP1γ promotes multiple myeloma drug resistance

Acquired chemoresistance to proteasome inhibitors is a major obstacle in managing multiple myeloma but key regulators and underlying mechanisms still remain to be explored. We find that high level of HP1γ is associated with low acetylation modification in the bortezomib-resistant myeloma cells using SILAC-based acetyl-proteomics assay, and higher HP1γ level is positively correlated with poorer outcomes in the clinic. Mechanistically, elevated HDAC1 in the bortezomib-resistant myeloma cells deacetylates HP1γ at lysine 5 and consequently alleviates the ubiquitin-mediated protein degradation, as well as the aberrant DNA repair capacity. HP1γ interacts with the MDC1 to induce DNA repair, and simultaneously the deacetylation modification and the interaction with MDC1 enhance the nuclear condensation of HP1γ protein and the chromatin accessibility of its target genes governing sensitivity to proteasome inhibitors, such as CD40, FOS and JUN. Thus, targeting HP1γ stability by using HDAC1 inhibitor re-sensitizes bortezomib-resistant myeloma cells to proteasome inhibitors treatment in vitro and in vivo. Our findings elucidate a previously unrecognized role of HP1γ in inducing drug resistance to proteasome inhibitors of myeloma cells and suggest that targeting HP1γ may be efficacious for overcoming drug resistance in refractory or relapsed multiple myeloma patients.

Venetoclax resistance induced by activated T cells can be counteracted by sphingosine kinase inhibitors in chronic lymphocytic leukemia

The treatment of chronic lymphocytic leukemia (CLL) patients with venetoclax-based regimens has demonstrated efficacy and a safety profile, but the emergence of resistant cells and disease progression is a current complication. Therapeutic target of sphingosine kinases (SPHK) 1 and 2 has opened new opportunities in the treatment combinations of cancer patients. We previously reported that the dual SPHK1/2 inhibitor, SKI-II enhanced the in vitro cell death triggered by fludarabine, bendamustine or ibrutinib and reduced the activation and proliferation of chronic lymphocytic leukemia (CLL) cells. Since we previously showed that autologous activated T cells from CLL patients favor the activation of CLL cells and the generation of venetoclax resistance due to the upregulation of BCL-XL and MCL-1, we here aim to determine whether SPHK inhibitors affect this process. To this aim we employed the dual SPHK1/2 inhibitor SKI-II and opaganib, a SPHK2 inhibitor that is being studied in clinical trials. We found that SPHK inhibitors reduce the activation of CLL cells and the generation of venetoclax resistance induced by activated T cells mainly due to a reduced upregulation of BCL-XL. We also found that SPHK2 expression was enhanced in CLL cells by activated T cells of the same patient and the presence of venetoclax selects resistant cells with high levels of SPHK2. Of note, SPHK inhibitors were able to re-sensitize already resistant CLL cells to a second venetoclax treatment. Our results highlight the therapeutic potential of SPHK inhibitors in combination with venetoclax as a promising treatment option for the patients.

Nuclear factor-kappaB mediates the survival of rat kidney cells after cadmium exposure via promoting autophagy and inhibiting apoptosis

Cadmium (Cd) is a heavy metal pollutant in the environment, and the kidney is one of the target organs after Cd exposure. Previous studies have shown that apoptosis and autophagy disorders are the main mechanisms of Cd-induced nephrotoxicity in rats. As a transcription factor that balances cell survival and death, nuclear factor-kappaB (NF-κB) protein plays dual regulatory effects on apoptosis and autophagy in multiple renal diseases. However, the regulatory mechanisms of NF-κB in Cd-induced kidney injury remain unclear. Therefore, the normal rat kidney cell line (NRK-52E cells) was applied to investigate the above questions in this study. Here, we found that Cd promotes the nuclear translocation and activation of NF-κB in a concentration-dependent manner, and activated NF-κB mediates NRK-52E cells survival after Cd exposure. Next, our study elaborated the mechanisms of NF-κB in antagonizing Cd-induced renal cytotoxicity. Inhibition of NF-κB by inhibitor BAY 11-7082 (BAY) and NF-κB p65 siRNA (siNF-κB p65) exacerbate Cd-induced apoptosis and autophagy inhibition, and then aggravate Cd-induced NRK-52E cells injury. Activation of NF-κB by activator phorbol-12-myristate-13-acetate (PMA) alleviates Cd-induced apoptosis and autophagy inhibition, and then attenuates Cd-induced NRK-52E cells injury. In conclusion, Cd exposure promotes the activation of NF-κB, and activated NF-κB mediates the survival of NRK-52E cells after Cd exposure via promoting autophagy and inhibiting apoptosis.

Macrophage Sprouty4 deficiency diminishes sepsis-induced acute lung injury in mice

OBJECTIVE

Inflammation and oxidative stress play critical roles in sepsis-induced acute lung injury (ALI). Sprout4 (Spry4) is involved in regulating inflammation and tissue injury; however, its role and mechanism in sepsis-induced ALI remain elusive.

METHODS

Macrophage-specific Spry4 knockout (Spry4^MKO), transgenic (Spry4^MTG) mice and matched control littermates were generated and exposed to cecum ligation and puncture (CLP) surgery to establish bacterial sepsis-induced ALI. Bone marrow-derived macrophages (BMDMs) from Spry4^MKO or Spry4^MTG mice were isolated and subjected to lipopolysaccharide (LPS) stimulation to further validate the role of Spry4 in vitro. To verify the necessity of AMP-activated protein kinase (AMPK), Spry4 and AMPK double knockout mice and compound C were used in vivo and in vitro. BMDMs were treated with STO-609 to inhibit calcium/calmodulin-dependent protein kinase kinase 2 (CaMKK2).

RESULTS

We found that macrophage Spry4 was increased in CLP mice and positively correlated with sepsis-induced ALI. Macrophage Spry4 deficiency prevented, while macrophage Spry4 overexpression exacerbated sepsis-induced inflammation, oxidative stress and ALI in mice and BMDMs. Mechanistic studies revealed that macrophage Spry4 deficiency alleviated sepsis-induced ALI through activating CaMKK2/AMPK pathway.

CONCLUSION

Our study identify macrophage Spry4 as a promising predictive and therapeutic target of sepsis-induced ALI.

Bcl-2 Family Members Bcl-xL and Bax Cooperatively Contribute to Bortezomib Resistance in Mantle Cell Lymphoma

Mantle cell lymphoma (MCL) is an aggressive non-Hodgkin lymphoma with poor prognosis, due to the inevitable development of drug resistance. Despite being the first-in-class proteasome inhibitor for relapsed/refractory MCL, resistance to bortezomib (BTZ) in MCL patients remains a major hurdle of effective therapy, and relapse following BTZ is frequent. Understanding the mechanisms underlying BTZ resistance is, therefore, important for improving the clinical outcome and developing novel therapeutic strategies. Here, we established de novo BTZ-resistant human MCL-derived cells with the highest resistance index of 300-fold compared to parental cells. We provided compelling evidence that both Bcl-xL and Bax are key mediators in determining BTZ sensitivity in MCL cells. Overexpression of antiapoptotic Bcl-xL and depletion of proapoptotic Bax cooperatively protected MCL cells against BTZ-induced apoptosis, causing acquired BTZ resistance, likely by tilting the balance of Bcl-2 family proteins toward antiapoptotic signaling. Bioinformatics analyses suggested that high BCL2L1 (encoded Bcl-xL) and low BAX were, in part, associated with poor prognosis of MCL patients, e.g., when combined with low OGT, which regulates cellular O-GlcNAcylation. Our findings support recent strategies in small molecule drug discovery co-targeting antiapoptotic Bcl-2 family proteins using BH3 mimetics and Bax using Bax activators to overcome cancer drug resistance.

Immunomodulatory effects of two recombinant arginine kinases in Sarcoptes Scabiei on host peripheral blood mononuclear cells

Background

As an important zoonotic parasitic disease with global distribution, scabies causes serious public health and economic problems. Arginine kinase (AK) is involved in cell signal transduction, inflammation, and apoptosis. Two AKs were identified in Sarcoptes scabiei, but their functions in the host immune response remain unclear.

Methods

rSsAK-1 and rSsAK-2 were expressed, purified, and immunolocalized. The effects of rSsAK-1 and rSsAK-2 on rabbit PBMC proliferation, apoptosis, and migration; Bcl-2, Bcl-xl, Fas, Bax, and NF-κB transcription levels; and IL-2, IFN-γ, IL-4, IL-10, TGF-β1, and IL-17 secretion were detected.

Results

rSsAK-1 and rSsAK-2 were cloned and expressed successfully. Both enzymes were ~57 kDa and contained 17-kDa tagged proteins, and had good catalytic activity and immunoreactivity. The proteins were located in the S. scabiei exoskeleton, chewing mouthparts, legs, stomach, and intestine. SsAK-1 and SsAK-2 were secreted in the pool and epidermis of the skin lesions, which may be involved in S. scabiei–host interaction. rSsAK-1 and rSsAK-2 significantly promoted cell proliferation, induced cell migration, inhibited apoptosis, and increased Bcl-2, Bcl-xl and NF-κB (p65) transcription levels concentration-dependently, and inhibited IL-2, IFN-γ, and IL-10 secretion and promoted IL-4 and IL-17 secretion.

Conclusion

rSsAK-1 and rSsAK-2 might increase Bcl-2 and Bcl-xl expression by activating the NF-κB signaling pathway to promote cell proliferation and inhibit apoptosis, which induced PBMC survival. By inducing PBMC migration to the infection site, rSsAK-1 and rSsAK-2 shifted the Th1/Th2 balance toward Th2 and changed the Th17/Treg balance, which indicated their immune role in S. scabiei allergic inflammation.

Targeting Mitochondrial Metabolism to Reverse Radioresistance: An Alternative to Glucose Metabolism

Radiotherapy failure and poor tumor prognosis are primarily attributed to radioresistance. Improving the curative effect of radiotherapy and delaying cancer progression have become difficult problems for clinicians. Glucose metabolism has long been regarded as the main metabolic process by which tumor cells meet their bioenergetic and anabolic needs, with the complex interactions between the mitochondria and tumors being ignored. This misconception was not dispelled until the early 2000s; however, the cellular molecules and signaling pathways involved in radioresistance remain incompletely defined. In addition to being a key metabolic site that regulates tumorigenesis, mitochondria can influence the radiation effects of malignancies by controlling redox reactions, participating in oxidative phosphorylation, producing oncometabolites, and triggering apoptosis. Therefore, the mitochondria are promising targets for the development of novel anticancer drugs. In this review, we summarize the internal relationship and related mechanisms between mitochondrial metabolism and cancer radioresistance, thus exploring the possibility of targeting mitochondrial signaling pathways to reverse radiation insensitivity. We suggest that attention should be paid to the potential value of mitochondria in prolonging the survival of cancer patients.

Targeting the immune microenvironment in mantle cell lymphoma: implications for current and emerging therapies

Mantle cell lymphoma (MCL) is a morphologically and phenotypically heterogeneous subtype of non-Hodgkin lymphoma, and has historically been associated with poor outcomes. However, recent advances in our understanding of this disease have yielded new targeted and immune-based therapies with promising activity. Immune-based therapies such as monoclonal antibodies, immunomodulators, and CAR T cells have significantly improved outcomes and are now standard of care in MCL. In this review, we describe our current understanding of the immune microenvironment of MCL, discuss current immunotherapeutic approaches, and highlight promising novel immune-based therapies and combination therapies that may further improve outcomes for patients with MCL.

Approach to a patient with "double refractory" chronic lymphocytic leukemia: "Double, double toil and trouble" (Shakespeare)

As patients continue to live longer with chronic lymphocytic leukemia, it has become evident that there is an unmet treatment need for patients who have progressed on multiple lines of therapy. In this article, we attempt to define the "double refractory" patient as resistant to both Bruton's tyrosine kinase inhibitors (BTKi) and venetoclax for which prognosis is poor and there remains no standard of care. We further examine the mechanism of resistance to these targeted agents and discuss the current landscape for managing this patient population. Finally, we explore data supporting promising new agents, including non-covalent BTKi, chimeric antigen receptor T cells, and additional classes of agents currently in development.

SOHO State of the Art Updates and Next Questions | Mechanisms of Resistance to BCL2 Inhibitor Therapy in Chronic Lymphocytic Leukemia and Potential Future Therapeutic Directions

Chronic lymphocytic leukaemia (CLL) constitutively overexpresses B-cell lymphoma 2 (BCL2) with consequent dysregulation of intrinsic apoptosis leading to abnormal cellular survival. Therapeutic use of BCL2 inhibitors (BCL2i, eg, venetoclax) in CLL, as both continuous monotherapy or in fixed duration combination, has translated scientific rationale into clinical benefit with significant rates of complete responses, including those without detectable minimal residual disease. Unlike with chemotherapy, response rates to venetoclax do not appear to be influenced by pre-existing chromosomal abnormalities or somatic mutations present, although the duration of response observed remains shorter for those with traditional higher risk genetic aberrations. This review seeks to describe both the disease factors that influence primary venetoclax sensitivity/resistance and those resistance mechanisms that may be acquired secondary to BCL2i therapy in CLL. Baseline venetoclax-sensitivity or -resistance is influenced by the expression of BCL2 relative to other BCL2 family member proteins, microenvironmental factors including nodal T-cell stimulation, and tumoral heterogeneity. With selection pressure applied by continuous venetoclax exposure, secondary resistance mechanisms develop in oligoclonal fashion. Those mechanisms described include acquisition of BCL2 variants, dynamic aberrations of alternative BCL2 family proteins, and mutations affecting both BAX and other BH3 proteins. In view of the resistance described, this review also proposes future applications of BCL2i therapy in CLL and potential means by which BCL2i-resistance may be abrogated.

Revealing β-TrCP activity dynamics in live cells with a genetically encoded biosensor

The F-box protein beta-transducin repeat containing protein (β-TrCP) acts as a substrate adapter for the SCF E3 ubiquitin ligase complex, plays a crucial role in cell physiology, and is often deregulated in many types of cancers. Here, we develop a fluorescent biosensor to quantitatively measure β-TrCP activity in live, single cells in real-time. We find β-TrCP remains constitutively active throughout the cell cycle and functions to maintain discreet steady-state levels of its substrates. We find no correlation between expression levels of β-TrCP and β-TrCP activity, indicating post-transcriptional regulation. A high throughput screen of small-molecules using our reporter identifies receptor-tyrosine kinase signaling as a key axis for regulating β-TrCP activity by inhibiting binding between β-TrCP and the core SCF complex. Our study introduces a method to monitor β-TrCP activity in live cells and identifies a key signaling network that regulates β-TrCP activity throughout the cell cycle.

Modulation of Ca2+ signaling by antiapoptotic Bcl-2 versus Bcl-xL: From molecular mechanisms to relevance for cancer cell survival

Members of the Bcl-2-protein family are key controllers of apoptotic cell death. The family is divided into antiapoptotic (including Bcl-2 itself, Bcl-xL, Mcl-1, etc.) and proapoptotic members (Bax, Bak, Bim, Bim, Puma, Noxa, Bad, etc.). These proteins are well known for their canonical role in the mitochondria, where they control mitochondrial outer membrane permeabilization and subsequent apoptosis. However, several proteins are recognized as modulators of intracellular Ca²⁺ signals that originate from the endoplasmic reticulum (ER), the major intracellular Ca²⁺-storage organelle. More than 25 years ago, Bcl-2, the founding member of the family, was reported to control apoptosis through Ca²⁺ signaling. Further work elucidated that Bcl-2 directly targets and inhibits inositol 1,4,5-trisphosphate receptors (IP₃Rs), thereby suppressing proapoptotic Ca²⁺ signaling. In addition to Bcl-2, Bcl-xL was also shown to impact cell survival by sensitizing IP₃R function, thereby promoting prosurvival oscillatory Ca²⁺ release. However, new work challenges this model and demonstrates that Bcl-2 and Bcl-xL can both function as inhibitors of IP₃Rs. This suggests that, depending on the cell context, Bcl-xL could support very distinct Ca²⁺ patterns. This not only raises several questions but also opens new possibilities for the treatment of Bcl-xL-dependent cancers. In this review, we will discuss the similarities and divergences between Bcl-2 and Bcl-xL regarding Ca²⁺ homeostasis and IP₃R modulation from both a molecular and a functional point of view, with particular emphasis on cancer cell death resistance mechanisms.

Characterization of metabolic alterations of chronic lymphocytic leukemia in the lymph node microenvironment

Altered metabolism is a hallmark of both cell division and cancer. Chronic lymphocytic leukemia (CLL) cells circulate between peripheral blood (PB) and lymph nodes (LNs), where they receive proliferative and prosurvival signals from surrounding cells. However, insight into the metabolism of LN CLL and how this may relate to therapeutic response is lacking. To obtain insight into CLL LN metabolism, we applied a 2-tiered strategy. First, we sampled PB from 8 patients at baseline and after 3-month ibrutinib (IBR) treatment, which forces egress of CLL cells from LNs. Second, we applied in vitro B-cell receptor (BCR) or CD40 stimulation to mimic the LN microenvironment and performed metabolomic and transcriptomic analyses. The combined analyses indicated prominent changes in purine, glucose, and glutamate metabolism occurring in the LNs. CD40 signaling mostly regulated amino acid metabolism, tricarboxylic acid cycle (TCA), and energy production. BCR signaling preferably engaged glucose and glycerol metabolism and several biosynthesis routes. Pathway analyses demonstrated opposite effects of in vitro stimulation vs IBR treatment. In agreement, the metabolic regulator MYC and its target genes were induced after BCR/CD40 stimulation and suppressed by IBR. Next, 13C fluxomics performed on CD40/BCR-stimulated cells confirmed a strong contribution of glutamine as fuel for the TCA cycle, whereas glucose was mainly converted into lactate and ribose-5-phosphate. Finally, inhibition of glutamine import with V9302 attenuated CD40/BCR-induced resistance to venetoclax. Together, these data provide insight into crucial metabolic changes driven by the CLL LN microenvironment. The prominent use of amino acids as fuel for the TCA cycle suggests new therapeutic vulnerabilities.

The Therapeutic Potential of Targeting NIK in B Cell Malignancies

NF-κB-inducing kinase (NIK) is a key player in non-canonical NF-κB signaling, involved in several fundamental cellular processes, and is crucial for B cell function and development. In response to certain signals and ligands, such as CD40, BAFF and lymphotoxin-β activation, NIK protein stabilization and subsequent NF-κB activation is achieved. Overexpression or overactivation of NIK is associated with several malignancies, including activating mutations in multiple myeloma (MM) and gain-of-function in MALT lymphoma as a result of post-translational modifications. Consequently, drug discovery studies are devoted to pharmacologic modulation of NIK and development of specific novel small molecule inhibitors. However, disease-specific in vitro and in vivo studies investigating NIK inhibition are as of yet lacking, and clinical trials with NIK inhibitors remain to be initiated. In order to bridge the gap between bench and bedside, this review first briefly summarizes our current knowledge on NIK activation, functional activity and stability. Secondly, we compare current inhibitors targeting NIK based on efficacy and specificity, and provide a future perspective on the therapeutic potential of NIK inhibition in B cell malignancies.

BCL2 inhibitor ABT-199 and BCL2L1 inhibitor WEHI-539 coordinately promote NOXA-mediated degradation of MCL1 in human leukemia cells

Human leukemia U937 cells that were continuously treated with hydroquinone (HQ) were transformed into U937/HQ cells with increased MCL1 and BCL2L1 expression. Compared with their parental cells, U937/HQ cells were less sensitive to ABT-263 (BCL2/BCL2L1 inhibitor)/ABT-199 (BCL2 inhibitor) cytotoxicity. The combination of WEHI-539 (BCL2L1 inhibitor) with either ABT-199 or ABT-263 showed synergistic cytotoxicity to U937 and U937/HQ cells. Therefore, we further investigated the cytotoxic mechanism induced by the combination of WEHI-539 and ABT-199. The combined treatment of WEHI-539 and ABT-199 induced NOX4/ROS/p38 MAPK axis-mediated autophagy, which in turn accelerated β-TrCP mRNA turnover. Downregulation of β-TrCP increased Sp1 expression, thereby promoting Sp1-mediated NOXA transcription, which in turn induced NOXA-dependent MCL1 degradation. Enforced expression of MCL1 alleviated the cytotoxicity of WEHI-539 plus ABT-199 to induce the loss of mitochondrial membrane potential and cell viability. WEHI-539 alone induced Sp1/NOXA axis-mediated MCL1 downregulation, while ABT-199 significantly decreased the dose of WEHI-539 by approximately 350- and 50-fold to induce MCL1 suppression in parental and HQ-selected cells, respectively. Furthermore, WEHI-539 sensitized ABT-199-resistant U937 cells to ABT-199 cytotoxicity by inducing NOXA-mediated degradation of MCL1. Collectively, the data in this study indicate that ABT-199 and WEHI-539 cooperatively induce NOXA-dependent MCL1 degradation, and the inhibition of MCL1 mainly explains their combined cytotoxicity in parental, HQ-selected, and ABT-199-resistant U937 cells.

Effective tumor cell abrogation via Venetoclax-mediated BCL-2 inhibition in KMT2A-rearranged acute B-lymphoblastic leukemia

Dysregulation of the intrinsic BCL-2 pathway-mediated apoptosis cascade is a common feature of hematological malignancies including acute B-lymphoblastic leukemia (B-ALL). The KMT2A-rearranged high-risk cytogenetic subtype is characterized by high expression of antiapoptotic protein BCL-2, likely due to the direct activating binding of KMT2A fusion proteins to the BCL2 gene. The BCL-2 inhibitor venetoclax (VEN) has proven great clinical value in other blood cancers, however, data on B-ALL is sparse and past studies have not so far described the effects of VEN on gene and protein expression profiles. Using cell lines and patient-derived in vivo xenograft models, we show BCL-2 pathway-mediated apoptosis induction and decelerated tumor cell counts in KMT2A-rearranged B-ALL but not in other cytogenetic subtypes. VEN treatment of cell line- and patient-derived xenografts reduced blast frequencies in blood, bone marrow, and spleen, and tumor cell doubling times were increased. Growth rates are further correlated with VEN concentrations in blood. In vitro incubation with VEN resulted in BCL-2 dephosphorylation and targeted panel RNA sequencing revealed reduced gene expression of antiapoptotic pathway members BCL2, MCL1, and BCL2L1 (BCL-XL). Reinforced translocation of BAX proteins towards mitochondria induced caspase activation and cell death commitment. Prolonged VEN application led to upregulation of antiapoptotic proteins BCL-2, MCL-1, and BCL-XL. Interestingly, the extrinsic apoptosis pathway was strongly modulated in SEM cells in response to VEN. Gene expression of members of the tumor necrosis factor signaling cascade was increased, resulting in canonical NF-kB signaling. This possibly suggests a previously undescribed mechanism of BCL-2-independent and NF-kB-mediated upregulation of MCL-1 and BCL-XL. In summary, we herein prove that VEN is a potent option to suppress tumor cells in KMT2A-rearranged B-ALL in vitro and in vivo. Possible evasion mechanisms, however, must be considered in subsequent studies.

In Vitro and In Vivo Models of CLL–T Cell Interactions: Implications for Drug Testing

Simple Summary

Chronic lymphocytic leukemia (CLL) cells in the peripheral blood and lymphoid microenvironment display substantially different gene expression profiles and proliferative capaci-ty. It has been suggested that CLL–T-cell interactions are key pro-proliferative stimuli in immune niches. We review in vitro and in vivo model systems that mimic CLL-T-cell interactions to trigger CLL proliferation and study therapy resistance. We focus on studies describing the co-culture of leukemic cells with T cells, or supportive cell lines expressing T-cell factors, and simplified models of CLL cells’ stimulation with recombinant factors. In the second part, we summarize mouse models revealing the role of T cells in CLL biology and implications for generating patient-derived xenografts by co-transplanting leukemic cells with T cells.

Abstract

T cells are key components in environments that support chronic lymphocytic leukemia (CLL), activating CLL-cell proliferation and survival. Here, we review in vitro and in vivo model systems that mimic CLL–T-cell interactions, since these are critical for CLL-cell division and resistance to some types of therapy (such as DNA-damaging drugs or BH3-mimetic venetoclax). We discuss approaches for direct CLL-cell co-culture with autologous T cells, models utilizing supportive cell lines engineered to express T-cell factors (such as CD40L) or stimulating CLL cells with combinations of recombinant factors (CD40L, interleukins IL4 or IL21, INFγ) and additional B-cell receptor (BCR) activation with anti-IgM antibody. We also summarize strategies for CLL co-transplantation with autologous T cells into immunodeficient mice (NOD/SCID, NSG, NOG) to generate patient-derived xenografts (PDX) and the role of T cells in transgenic CLL mouse models based on TCL1 overexpression (Eµ-TCL1). We further discuss how these in vitro and in vivo models could be used to test drugs to uncover the effects of targeted therapies (such as inhibitors of BTK, PI3K, SYK, AKT, MEK, CDKs, BCL2, and proteasome) or chemotherapy (fludarabine and bendamustine) on CLL–T-cell interactions and CLL proliferation.

Tipping the balance: toward rational combination therapies to overcome venetoclax resistance in mantle cell lymphoma

Mantle cell lymphoma (MCL), an aggressive, but incurable B-cell lymphoma, is genetically characterized by the t(11;14) translocation, resulting in the overexpression of Cyclin D1. In addition, deregulation of the B-cell lymphoma-2 (BCL-2) family proteins BCL-2, B-cell lymphoma-extra large (BCL-X_L), and myeloid cell leukemia-1 (MCL-1) is highly common in MCL. This renders these BCL-2 family members attractive targets for therapy; indeed, the BCL-2 inhibitor venetoclax (ABT-199), which already received FDA approval for the treatment of chronic lymphocytic leukemia (CLL) and acute myeloid leukemia (AML), shows promising results in early clinical trials for MCL. However, a significant subset of patients show primary resistance or will develop resistance upon prolonged treatment. Here, we describe the underlying mechanisms of venetoclax resistance in MCL, such as upregulation of BCL-X_L or MCL-1, and the recent (clinical) progress in the development of inhibitors for these BCL-2 family members, followed by the transcriptional and (post-)translational (dys)regulation of the BCL-2 family proteins, including the role of the lymphoid organ microenvironment. Based upon these insights, we discuss how rational combinations of venetoclax with other therapies can be exploited to prevent or overcome venetoclax resistance and improve MCL patient outcome.

Targeting the Non-Canonical NF-κB Pathway in Chronic Lymphocytic Leukemia and Multiple Myeloma

In this study, we evaluated an NF-κB inducing kinase (NIK) inhibitor, CW15337, in primary chronic lymphocytic leukemia (CLL) cells, CLL and multiple myeloma (MM) cell lines and normal B- and T-lymphocytes. Basal NF-κB subunit activity was characterized using an enzyme linked immunosorbent assay (ELISA), and the effects of NIK inhibition were then assessed in terms of cytotoxicity and the expression of nuclear NF-κB subunits following monoculture and co-culture with CD40L-expressing fibroblasts, as a model of the lymphoid niche. CW15337 induced a dose-dependent increase in apoptosis, and nuclear expression of the non-canonical NF-κB subunit, p52, was correlated with sensitivity to CW15337 (p = 0.01; r² = 0.39). Co-culture on CD40L-expressing cells induced both canonical and non-canonical subunit expression in nuclear extracts, which promoted in vitro resistance against fludarabine and ABT-199 (venetoclax) but not CW15337. Furthermore, the combination of CW15337 with fludarabine or ABT-199 showed cytotoxic synergy. Mechanistically, CW15337 caused the selective inhibition of non-canonical NF-κB subunits and the transcriptional repression of BCL2L1, BCL2A1 and MCL1 gene transcription. Taken together, these data suggest that the NIK inhibitor, CW15337, exerts its effects via suppression of the non-canonical NF-κB signaling pathway, which reverses BCL2 family-mediated resistance in the context of CD40L stimulation.

Aberrantly expressed Wnt5a in nurse-like cells drives resistance to Venetoclax in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is characterized by the accumulation of neoplastic B lymphocytes with high levels of Wnt5a in the plasma. Currently, the cell source of Wnt5a remains controversial. The receptor of Wnt5a is ROR1, whose expression is associated with disease progression and resistance to venetoclax, a BCL-2 inhibitor approved for the treatment of CLL. In this study, we found that the levels of Wnt5a in the plasma of CLL patients were positively correlated with absolute monocyte counts, but not lymphocyte counts. We cultured monocyte-derived nurse-like cells (NLCs) from patients with CLL, and detected Wnt5a expressed in NLCs. Flow cytometry and transwell assays showed that the antibody neutralizing Wnt5a inhibited the enhanced survival and migration in CLL cells co-cultured with NLCs. Furthermore, we performed a drug screening with CLL cells cultured with or without NLCs with a library containing 133 FDA-approved oncology drugs by using high-throughput flow cytometry. We observed a significant resistance to venetoclax in CLL cells co-cultured with NLCs. Immunoblot revealed the activation of NF-κB with enhanced expression of MCL-1 and BCL-XL in CLL cells co-cultured with NLCs. Neutralizing Wnt5a or blocking NF-κB pathway significantly decreased the expression of MCL-1 and BCL-XL, which leads to enhanced sensitivity to venetoclax in CLL cells co-cultured with NLCs. In conclusion, our data showed that NLCs could be one of the sources of Wnt5a detected in patients with CLL, and Wnt5a-induced NF-κB activation in the CLL microenvironment results in resistance to venetoclax in CLL cells.

IAP and HDAC inhibitors interact synergistically in myeloma cells through noncanonical NF-κB- and caspase-8-dependent mechanisms

Interactions between the inhibitor of apoptosis protein antagonist LCL161 and the histone deacetylase inhibitor panobinostat (LBH589) were examined in human multiple myeloma (MM) cells. LCL161 and panobinostat interacted synergistically to induce apoptosis in diverse MM cell lines, including those resistant to bortezomib (PS-R). Similar interactions were observed with other histone deacetylase inhibitors (MS-275) or inhibitors of apoptosis protein antagonists (birinapant). These events were associated with downregulation of the noncanonical (but not the canonical) NF-κB pathway and activation of the extrinsic, caspase-8-related apoptotic cascade. Coexposure of MM cells to LCL161/LBH589 induced TRAF3 upregulation and led to TRAF2 and NIK downregulation, diminished expression of BCL-XL, and induction of γH2A.X. Ectopic expression of TRAF2, NIK, or BCL-XL, or short hairpin RNA TRAF3 knock-down, significantly reduced LCL161/LBH589 lethality, as did ectopic expression of dominant-negative FADD. Stromal/microenvironmental factors failed to diminish LCL161/LBH589-induced cell death. The LCL161/LBH589 regimen significantly increased cell killing in primary CD138+ cells (N = 31) and was particularly effective in diminishing the primitive progenitor cell-enriched CD138-/19+/20+/27+ population (N = 23) but was nontoxic to normal CD34+ cells. Finally, combined LCL161/LBH589 treatment significantly increased survival compared with single-agent treatment in an immunocompetent 5TGM1 murine MM model. Together, these findings argue that LCL161 interacts synergistically with LBH589 in MM cells through a process involving inactivation of the noncanonical NF-κB pathway and activation of the extrinsic apoptotic pathway, upregulation of TRAF3, and downregulation of TRAF2/BCL-XL. Notably, this regimen overcomes various forms of resistance, is active against primary MM cells, and displays significant in vivo activity. This strategy warrants further consideration in MM.

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.

Biological significance of monoallelic and biallelic BIRC3 loss in del(11q) chronic lymphocytic leukemia progression

BIRC3 is monoallelically deleted in up to 80% of chronic lymphocytic leukemia (CLL) cases harboring del(11q). In addition, truncating mutations in the remaining allele of this gene can lead to BIRC3 biallelic inactivation, which has been shown to be a marker for reduced survival in CLL. Nevertheless, the biological mechanisms by which these lesions could contribute to del(11q) CLL pathogenesis and progression are partially unexplored. We implemented the CRISPR/Cas9-editing system to generate isogenic CLL cell lines harboring del(11q) and/or BIRC3 mutations, modeling monoallelic and biallelic BIRC3 loss. Our results reveal that monoallelic BIRC3 deletion in del(11q) cells promotes non-canonical NF-κB signaling activation via RelB-p52 nuclear translocation, being these effects allelic dose-dependent and therefore further enhanced in del(11q) cells with biallelic BIRC3 loss. Moreover, we demonstrate ex vivo in primary cells that del(11q) cases including BIRC3 within their deleted region show evidence of non-canonical NF-κB activation which correlates with high BCL2 levels and enhanced sensitivity to venetoclax. Furthermore, our results show that BIRC3 mutations in del(11q) cells promote clonal advantage in vitro and accelerate leukemic progression in an in vivo xenograft model. Altogether, this work highlights the biological bases underlying disease progression of del(11q) CLL patients harboring BIRC3 deletion and mutation.

Sonapatha (Oroxylum indicum) mediates cytotoxicity in cultured HeLa cells by inducing apoptosis and suppressing NF-κB, COX-2, RASSF7 and NRF2

Oroxylum indicum (Sonapatha) is traditionally used to cure several human ailments. Therefore, the cell killing effect of chloroform, ethanol, and water extracts of Sonapatha was studied in cultured HeLa cells treated with 0-100 µg/mL of these extracts/doxorubicin by MTT assay. Since ethanol extract was most cytotoxic its effect was further investigated by clonogenic, apoptosis, necrosis, and lactate dehydrogenase assays. The mechanism of cytotoxicity of Sonapatha was determined at the molecular level by estimation of caspase 8 and 3 activities and Western blot analysis of NF-κB, COX-2, Nrf2, and RASSF7 which are overexpressed in neoplastic cells. HeLa cells treated with Sonapatha extract exhibited a concentration and time-dependent rise in the cytotoxicity as indicated by the MTT assay. Ethanol extract of Sonapatha (0, 20, 40, and 80 μg/mL) reduced clonogenicity, increased DNA fragmentation, apoptotic and necrotic indices, lactate dehydrogenase release, caspase 8 and 3 activities and inhibited the overexpression of NF-κB, COX-2, Nrf2, and RASSF7 in HeLa cells concentration-dependently.