Characterization of Stealth Liposome-Based Nanoparticles Encapsulating the ACAT1/SOAT1 Inhibitor F26: Efficacy and Toxicity Studies In Vitro and in Wild-Type Mice.

Cholesterol homeostasis is pivotal for cellular function. Acyl-coenzyme A:cholesterol acyltransferase 1 (ACAT1), also abbreviated as SOAT1, is an enzyme responsible for catalyzing the storage of excess cholesterol to cholesteryl esters. ACAT1 is an emerging target to treat diverse diseases including atherosclerosis, cancer, and neurodegenerative diseases. F12511 is a high-affinity ACAT1 inhibitor. Previously, we developed a stealth liposome-based nanoparticle to encapsulate F12511 to enhance its delivery to the brain and showed its efficacy in treating a mouse model for Alzheimer's disease (AD). In this study, we introduce F26, a close derivative of F12511 metabolite in rats. F26 was encapsulated in the same DSPE-PEG2000/phosphatidylcholine (PC) liposome-based nanoparticle system. We employed various in vitro and in vivo methodologies to assess F26's efficacy and toxicity compared to F12511. The results demonstrate that F26 is more effective and durable than F12511 in inhibiting ACAT1, in both mouse embryonic fibroblasts (MEFs), and in multiple mouse tissues including the brain tissues, without exhibiting any overt systemic or neurotoxic effects. This study demonstrates the superior pharmacokinetic and safety profile of F26 in wild-type mice, and suggests its therapeutic potential against various neurodegenerative diseases including AD.

Genome-scale clustered regularly interspaced short palindromic repeats screen identifies nucleotide metabolism as an actionable therapeutic vulnerability in diffuse large B-cell lymphoma.

Diffuse large B-cell lymphoma (DLBCL) is the most common malignancy that develops in patients with ataxia-telangiectasia, a cancer-predisposing inherited syndrome characterized by inactivating germline ATM mutations. ATM is also frequently mutated in sporadic DLBCL. To investigate lymphomagenic mechanisms and lymphoma-specific dependencies underlying defective ATM, we applied ribonucleic acid (RNA)-seq and genome-scale loss-offunction clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 screens to systematically interrogate B-cell lymphomas arising in a novel murine model (Atm-/-nu-/-) with constitutional Atm loss, thymic aplasia but residual T-cell populations. Atm-/-nu-/-lymphomas, which phenotypically resemble either activated B-cell-like or germinal center Bcell-like DLBCL, harbor a complex karyotype, and are characterized by MYC pathway activation. In Atm-/-nu-/-lymphomas, we discovered nucleotide biosynthesis as a MYCdependent cellular vulnerability that can be targeted through the synergistic nucleotidedepleting actions of mycophenolate mofetil (MMF) and the WEE1 inhibitor, adavosertib (AZD1775). The latter is mediated through a synthetically lethal interaction between RRM2 suppression and MYC dysregulation that results in replication stress overload in Atm-/-nu-/-lymphoma cells. Validation in cell line models of human DLBCL confirmed the broad applicability of nucleotide depletion as a therapeutic strategy for MYC-driven DLBCL independent of ATM mutation status. Our findings extend current understanding of lymphomagenic mechanisms underpinning ATM loss and highlight nucleotide metabolism as a targetable therapeutic vulnerability in MYC-driven DLBCL.

Putting the STING back into BH3-mimetic drugs for TP53-mutant blood cancers.

TP53-mutant blood cancers remain a clinical challenge. BH3-mimetic drugs inhibit BCL-2 pro-survival proteins, inducing cancer cell apoptosis. Despite acting downstream of p53, functional p53 is required for maximal cancer cell killing by BH3-mimetics through an unknown mechanism. Here, we report p53 is activated following BH3-mimetic induced mitochondrial outer membrane permeabilization, leading to BH3-only protein induction and thereby potentiating the pro-apoptotic signal. TP53-deficient lymphomas lack this feedforward loop, providing opportunities for survival and disease relapse after BH3-mimetic treatment. The therapeutic barrier imposed by defects in TP53 can be overcome by direct activation of the cGAS/STING pathway, which promotes apoptosis of blood cancer cells through p53-independent BH3-only protein upregulation. Combining clinically relevant STING agonists with BH3-mimetic drugs efficiently kills TRP53/TP53-mutant mouse B lymphoma, human NK/T lymphoma, and acute myeloid leukemia cells. This represents a promising therapy regime that can be fast-tracked to tackle TP53-mutant blood cancers in the clinic.

Loss-of-Function but Not Gain-of-Function Properties of Mutant TP53 Are Critical for the Proliferation, Survival, and Metastasis of a Broad Range of Cancer Cells.

Mutations in the tumor suppressor TP53 cause cancer and impart poor chemotherapeutic responses, reportedly through loss-of-function, dominant-negative effects and gain-of-function (GOF) activities. The relative contributions of these attributes is unknown. We found that removal of 12 different TP53 mutants with reported GOFs by CRISPR/Cas9 did not impact proliferation and response to chemotherapeutics of 15 human cancer cell lines and colon cancer-derived organoids in culture. Moreover, removal of mutant TP53/TRP53 did not impair growth or metastasis of human cancers in immune-deficient mice or growth of murine cancers in immune-competent mice. DepMap mining revealed that removal of 158 different TP53 mutants had no impact on the growth of 391 human cancer cell lines. In contrast, CRISPR-mediated restoration of wild-type TP53 extinguished the growth of human cancer cells in vitro. These findings demonstrate that LOF but not GOF effects of mutant TP53/TRP53 are critical to sustain expansion of many tumor types. SIGNIFICANCE: This study provides evidence that removal of mutant TP53, thereby deleting its reported GOF activities, does not impact the survival, proliferation, metastasis, or chemotherapy responses of cancer cells. Thus, approaches that abrogate expression of mutant TP53 or target its reported GOF activities are unlikely to exert therapeutic impact in cancer. See related commentary by Lane, p. 211 . This article is featured in Selected Articles from This Issue, p. 201.

Genome-wide CRISPR screening identifies a role for ARRDC3 in TRP53-mediated responses.

Whole-genome screens using CRISPR technologies are powerful tools to identify novel tumour suppressors as well as factors that impact responses of malignant cells to anti-cancer agents. Applying this methodology to lymphoma cells, we conducted a genome-wide screen to identify novel inhibitors of tumour expansion that are induced by the tumour suppressor TRP53. We discovered that the absence of Arrestin domain containing 3 (ARRDC3) increases the survival and long-term competitiveness of MYC-driven lymphoma cells when treated with anti-cancer agents that activate TRP53. Deleting Arrdc3 in mice caused perinatal lethality due to various developmental abnormalities, including cardiac defects. Notably, the absence of ARRDC3 markedly accelerated MYC-driven lymphoma development. Thus, ARRDC3 is a new mediator of TRP53-mediated suppression of tumour expansion, and this discovery may open new avenues to harness this process for cancer therapy.

Age-Appropriate Cancer Screenings Through a Dermatology Len.

BACKGROUND: Primary care physicians are often the first to identify signs and symptoms concerning for cancer. An important aspect of cancer screening is thorough skin examinations and subsequent referral to a dermatologist for atypical cutaneous presentations, which may be associated with an underlying visceral malignancy. Diagnostic considerations for pruritus without dermatitis ("itch without rash") in adults include senile pruritus, medication reaction, and paraneoplastic syndrome. Recognition of cutaneous manifestations of cancer should prompt cancer screening by primary care providers. OBJECTIVE: To update practicing physicians on current cancer screening guidelines with a specific focus on cutaneous clues to prompt further workup. METHODS: American Cancer Society and United States Preventive Services Task Force guidelines were systematically reviewed using PubMed and organizational websites during August and September, 2021, with review of Task Force Guidelines during October, 2022. RESULTS: Colorectal, cervical, breast, lung, skin, prostate, ovarian, hematologic, pancreatic, thyroid, testicular, bladder, oral, and gastric cancer screening guidelines are summarized. CONCLUSIONS: Primary care physicians can recognize atypical cutaneous conditions and facilitate referral to a dermatologist for evaluation and/or directly order tests themselves to initiate appropriate cancer screening.

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.

Effectiveness of Body Mass Index-Based Prophylactic Enoxaparin Dosing in Bariatric Surgery Patients.

INTRODUCTION: Enoxaparin is administered for venous thromboembolic (VTE) prophylaxis in bariatric surgery patients. There is concern whether body mass index (BMI)-based enoxaparin dosing consistently achieves prophylactic targets in patients with severe obesity. METHODS: This retrospective study included patients who underwent bariatric surgery at an academic medical center from Jan 2015-May 2021 and had an anti-Xa level drawn 2.5-6 h after ≥3 doses of BMI-based prophylactic enoxaparin. The primary outcome was the percentage of patients who achieved a target anti-Xa level. Secondary outcomes were prevalence of venous thromboembolic and bleeding events within 30 d post-operatively. RESULTS: Overall, 137 patients were included. Mean BMI was 59.1 ± 10.4 kg/m2, mean age was 43.9 ± 13.3 y and 110 patients (80.3%) were female. Target anti-Xa levels were achieved in 116 patients (84.7%); 14 (10.2%) were above target and 7 (5.1%) were below target. Patients with above target anti-Xa levels were significantly shorter in height than those within target range (167.1 versus 159.8 cm, P = 0.003). Five patients (3.6%) had a bleeding event; no thromboembolisms occurred. Anti-Xa levels correlated more strongly with enoxaparin dose per unit estimated blood volume (EBV) than dose per unit BMI (Rho = 0.54 versus Rho = 0.33). CONCLUSIONS: Target range anti-Xa levels were achieved in 85% of patients using BMI-based enoxaparin dosing. Patients with above target anti-Xa levels were significantly shorter by nearly 3 inches, suggesting an increased risk of overdosing enoxaparin in shorter, obese patients. An EBV-based dosing regimen may better account for patient height and is supported by a greater correlation with anti-Xa levels with dosing based on EBV than BMI.

The anti-cancer agent APR-246 can activate several programmed cell death processes to kill malignant cells.

Mutant TP53 proteins are thought to drive the development and sustained expansion of cancers at least in part through the loss of the wild-type (wt) TP53 tumour suppressive functions. Therefore, compounds that can restore wt TP53 functions in mutant TP53 proteins are expected to inhibit the expansion of tumours expressing mutant TP53. APR-246 has been reported to exert such effects in malignant cells and is currently undergoing clinical trials in several cancer types. However, there is evidence that APR-246 may also kill malignant cells that do not express mutant TP53. To support the clinical development of APR-246 it is important to understand its mechanism(s) of action. By establishing isogenic background tumour cell lines with different TP53/TRP53 states, we found that APR-246 can kill malignant cells irrespective of their TP53/TRP53 status. Accordingly, RNAseq analysis revealed that treatment with APR-246 induces expression of the same gene set in Eµ-Myc mouse lymphoma cells of all four possible TRP53 states, wt, wt alongside mutant, knockout and knockout alongside mutant. We found that depending on the type of cancer cell and the concentration of APR-246 used, this compound can kill malignant cells through induction of various programmed cell death pathways, including apoptosis, necroptosis and ferroptosis. The sensitivity of non-transformed cells to APR-246 also depended on the cell type. These findings reveal that the clinical testing of APR-246 should not be limited to cancers expressing mutant TP53 but expanded to cancers that express wt TP53 or are TP53-deficient.

Large-Volume Fat Grafting: Identifying Risk Factors for Fat Necrosis.

BACKGROUND: Fat necrosis is a well-recognized complication following autologous fat grafting. The purpose of this study was to evaluate the incidence of fat necrosis after large-volume fat grafting and identify risk factors for fat necrosis. METHODS: A retrospective review was performed on 83 consecutive patients who underwent large-volume fat grafting (>100 cc) to the breast performed by the senior author (L.P.B.) between September of 2011 and May of 2016. Fat necrosis was defined as palpable nodules, or nodules seen on imaging. RESULTS: A total of 148 breasts underwent 170 autologous fat transplantations. Indications included the following: 72 reconstructions after surgical therapy and 98 cosmetic augmentations. Mean age was 48 years, median graft volume was 300 cc, and median length of follow-up 423 days. Overall incidence of necrosis was 32.9 percent, with 47.8 percent in previously irradiated patients. Increased incidence of necrosis was associated with increasing fat graft volumes (OR, 1.002; p = 0.032), increasing body mass index (OR, 1.13; p = 0.04), and simultaneous implant exchange with fat ( p = 0.003). Fat grafting volumes greater than 450 cc in a single breast were also associated with an increase in fat necrosis ( p = 0.04). Within a group of six patients who had bilateral fat grafting with unilateral radiation therapy, there was a significant increase in necrosis on the irradiated side ( p = 0.015). In a cohort of non-BRAVA patients, reconstruction (compared to augmentation) was associated with fat necrosis ( p = 0.039). CONCLUSIONS: Increased rates of fat necrosis were associated with volumes greater than 450 cc, patients undergoing concurrent implant exchange with fat grafting, and fat grafting after a history of lumpectomy or mastectomy without preexpansion. In addition, radiation therapy may be associated with a higher rate of complications. CLINICAL QUESTION/LEVEL OF EVIDENCE: Risk, III.

Flow cytometric single cell-based assay to simultaneously detect cell death, cell cycling, DNA content and cell senescence.

Cell death, cell cycle arrest and cellular senescence are three distinct cellular responses that can be induced by oncogene activation and diverse anti-cancer agents, and this often requires the action of the tumour suppressor TP53. Within a cell population, or even within an individual cell, these processes are not necessarily mutually exclusive. It is therefore important to measure all these processes simultaneously. However, current assays generally visualise only one or at best two responses, often only detecting the dominant one. Here, we present a novel flow cytometric assay that allows simultaneous assessment of cell viability and cell cycling through measurement of DNA content and DNA synthesis, and markers of cell senescence at the single cell level. We demonstrate that this assay can be performed on both human and murine cells, that are either cancerous or non-transformed, and can help to dissect complex cell fate decisions. We believe that this experimental tool will be useful for the study of diverse biological processes.

Facile method to incorporate high-affinity ACAT/SOAT1 inhibitor F12511 into stealth liposome-based nanoparticle and demonstration of its efficacy in blocking cholesteryl ester biosynthesis without overt toxicity in neuronal cell culture.

BACKGROUND: Acyl-CoA:cholesterol acyltransferase (ACAT) inhibitors have been considered as potential therapeutic agents to treat several diseases, including Alzheimer's disease, atherosclerosis, and cancer. While many ACAT inhibitors are readily available, methods to encapsulate them as nanoparticles have not been reported. NEW METHOD: We report a simple method to encapsulate ACAT inhibitors, using the potent hydrophobic ACAT inhibitor F12511 as an example. By mixing DSPE-PEG2000, egg phosphatidylcholine (PC), and F12511 in ethanol, followed by drying, resuspension and sonication in buffer, we show that F12511 can be encapsulated as stealth liposomes at high concentration. RESULTS: We successfully incorporated F12511 into nanoparticles and found that increasing PC in the nanoparticles markedly increased the amount of F12511 incorporated in stealth liposomes. The nanoparticles containing F12511 (Nanoparticle F) exhibit average size of approximately 200 nm and are stable at 4 ºC for at least 6 months. Nanoparticle F is very effective at inhibiting ACAT in human and mouse neuronal and microglial cell lines. Toxicity tests using mouse primary neuronal cells show that F12511 alone or Nanoparticle F added at concentrations from 2 to 10 µM for 24-, 48-, and 72-hours produces minimal, if any, toxicity. COMPARISON WITH EXISTING METHOD(S): Unlike existing methods, the current method is simple, cost effective, and can be expanded to produce tagged liposomes to increase specificity of delivery. This also offers opportunity to embrace water soluble agent(s) within the aqueous compartment of the nanoparticles for potential combinatorial therapy. CONCLUSIONS: This method shows promise for delivery of hydrophobic ACAT inhibitors at high concentration in vivo.

Poor T-cell receptor ß repertoire diversity early posttransplant for severe combined immunodeficiency predicts failure of immune reconstitution.

BACKGROUND: Development of a diverse T-cell receptor ß (TRB) repertoire is associated with immune recovery following hematopoietic cell transplantation (HCT) for severe combined immunodeficiency (SCID). High-throughput sequencing of the TRB repertoire allows evaluation of clonotype dynamics during immune reconstitution. OBJECTIVES: We investigated whether longitudinal analysis of the TRB repertoire would accurately describe T-cell receptor diversity and illustrate the quality of T-cell reconstitution following HCT or gene therapy for SCID. METHODS: We used high-throughput sequencing to study composition and diversity of the TRB repertoire in 27 infants with SCID at 3, 6, and 12 months and yearly posttreatment(s). Total RNA from peripheral blood was used as template to amplify TRB rearrangements. RESULTS: TRB sequence analysis showed poor diversity at 3 months, followed by significant improvement by 6 months after cellular therapies. Kinetics of development of TRB diversity were similar in patients with a range of underlying gene defects. However, in patients with RAG and DCLRE1C defects, HCT with no conditioning or immune suppression only resulted in lower diversity than did HCT with conditioning. HCT from a matched donor correlated with higher diversity than did HCT from a mismatched donor. Naive CD4+ T-cell count at 6 months post-HCT correlated with higher TRB diversity. A Shannon index of diversity of 5.2 or lower 3 months after HCT predicted a need for a second intervention. CONCLUSIONS: TRB repertoire after hematopoietic cell therapies for SCID provides a quantitative and qualitative measure of diversity of T-cell reconstitution and permits early identification of patients who may require a second intervention.

Proteome plasticity in response to persistent environmental change.

Temperature is a variable component of the environment, and all organisms must deal with or adapt to temperature change. Acute temperature change activates cellular stress responses, resulting in refolding or removal of damaged proteins. However, how organisms adapt to long-term temperature change remains largely unexplored. Here we report that budding yeast responds to long-term high temperature challenge by switching from chaperone induction to reduction of temperature-sensitive proteins and re-localizing a portion of its proteome. Surprisingly, we also find that many proteins adopt an alternative conformation. Using Fet3p as an example, we find that the temperature-dependent conformational difference is accompanied by distinct thermostability, subcellular localization, and, importantly, cellular functions. We postulate that, in addition to the known mechanisms of adaptation, conformational plasticity allows some polypeptides to acquire new biophysical properties and functions when environmental change endures.

Intact TP-53 function is essential for sustaining durable responses to BH3-mimetic drugs in leukemias.

Selective targeting of BCL-2 with the BH3-mimetic venetoclax has been a transformative treatment for patients with various leukemias. TP-53 controls apoptosis upstream of where BCL-2 and its prosurvival relatives, such as MCL-1, act. Therefore, targeting these prosurvival proteins could trigger apoptosis across diverse blood cancers, irrespective of TP53 mutation status. Indeed, targeting BCL-2 has produced clinically relevant responses in blood cancers with aberrant TP-53. However, in our study, TP53-mutated or -deficient myeloid and lymphoid leukemias outcompeted isogenic controls with intact TP-53, unless sufficient concentrations of BH3-mimetics targeting BCL-2 or MCL-1 were applied. Strikingly, tumor cells with TP-53 dysfunction escaped and thrived over time if inhibition of BCL-2 or MCL-1 was sublethal, in part because of an increased threshold for BAX/BAK activation in these cells. Our study revealed the key role of TP-53 in shaping long-term responses to BH3-mimetic drugs and reconciled the disparate pattern of initial clinical response to venetoclax, followed by subsequent treatment failure among patients with TP53-mutant chronic lymphocytic leukemia or acute myeloid leukemia. In contrast to BH3-mimetics targeting just BCL-2 or MCL-1 at doses that are individually sublethal, a combined BH3-mimetic approach targeting both prosurvival proteins enhanced lethality and durably suppressed the leukemia burden, regardless of TP53 mutation status. Our findings highlight the importance of using sufficiently lethal treatment strategies to maximize outcomes of patients with TP53-mutant disease. In addition, our findings caution against use of sublethal BH3-mimetic drug regimens that may enhance the risk of disease progression driven by emergent TP53-mutant clones.

The Impact of Bariatric Surgery Compared to Metformin Therapy on Pregnancy Outcomes in Patients with Polycystic Ovarian Syndrome: a Systematic Review and Meta-analysis.

BACKGROUND: Polycystic ovarian syndrome (PCOS) is a leading cause of infertility among women of reproductive age. The interplay between hyperinsulinemia and obesity results in many of the reproductive and hormonal changes seen in PCOS including abnormal menses, infertility, and pregnancy loss. While bariatric surgery has been found to be an effective treatment strategy for morbid obesity, its role in the management of PCOS-related infertility compared to standard therapy (metformin) is less clear. AIMS: To assess the impact of bariatric surgery on pregnancy outcomes in women with PCOS compared to metformin therapy in a systematic review and meta-analysis. METHODS: MEDLINE, EMBASE, PubMed, and Google Scholar were searched from inception to August 2019. Studies that reported quantitative data on pregnancy outcomes on women of reproductive age with PCOS with at least a 3-month follow-up and a minimum of 5 or more sample size were included. The primary outcome was pregnancy rate, expressed as an event rate and 95% confidence interval (95% CI). RESULTS: Ten studies with a total of 587 patients were included in the final analyses (Metformin: 5 studies, n = 192; Bariatric surgery (BS): 5 studies (2 Roux-en-Y gastric bypass, 2 sleeve gastrectomy, 1 Roux-en-Y gastric bypass + sleeve gastrectomy), n = 186). The average time to follow-up was 18.25 months (range 3-36) with a shorter time to follow-up in the metformin group compared to the bariatric surgery group (Metformin: 11.2 vs BS: 24.5 months). While metformin increased the likelihood of pregnancy compared to placebo or non-surgical interventions (OR = 3.08, 95% CI 1.29-7.37, p = 0.01), the pregnancy rate after bariatric surgery was greater than metformin (34.9%, 95% CI 0.20-0.53 vs 17.1%, 95% CI 0.12-0.23, p = 0.026 for the difference). Additionally, there was a trend to a greater improvement in menstrual irregularity in the bariatric group compared to the metformin group with a reduction of 92% in the bariatric cohort compared to a reduction of 54% in the metformin cohort, but the data was limited. CONCLUSION: Bariatric surgery appears to be a more effective treatment strategy for patients with PCOS and class 3 obesity compared to metformin alone. Women with PCOS and infertility should consider bariatric surgery for weight loss and improvement in pregnancy outcomes.

BCL-XL inhibition by BH3-mimetic drugs induces apoptosis in models of Epstein-Barr virus-associated T/NK-cell lymphoma.

Epstein-Barr virus (EBV)-associated T- and natural killer (NK)-cell malignancies, such as extranodal NK-/T-cell lymphoma (ENKTL), exhibit high chemoresistance and, accordingly, such patients have a poor prognosis. The rare nature of such cancers and nonmalignant T/NK lymphoproliferative disorders, such as chronic active EBV (CAEBV), has limited our understanding of the pathogenesis of these diseases. Here, we characterize a panel of ENKTL- and CAEBV-derived cell lines that had been established from human tumors to be used as preclinical models of these diseases. These cell lines were interleukin-2 dependent and found to carry EBV in a latency II gene-expression pattern. All cell lines demonstrated resistance to cell death induction by DNA damage-inducing agents, the current standard of care for patients with these malignancies. This resistance was not correlated with the function of the multidrug efflux pump, P-glycoprotein. However, apoptotic cell death could be consistently induced following treatment with A-1331852, a BH3-mimetic drug that specifically inhibits the prosurvival protein BCL-XL. A-1331852-induced apoptosis was most efficacious when prosurvival MCL-1 was additionally targeted, either by BH3-mimetics or genetic deletion. Xenograft models established from the ENKTL cell line SNK6 provided evidence that A-1331852 treatment could be therapeutically beneficial in vivo. The data here suggest that therapeutic targeting of BCL-XL would be effective for patients with EBV-driven T/NK proliferative diseases, however, MCL-1 could be a potential resistance factor.