Impact of cost sharing exemption for hospitalized children under the age of six on healthcare utilization

Background: Childhood health conditions are important to learning, prospective health, and future human resources. In January 2006, the government implemented a policy of cost sharing exemption for hospitalized children under the age of six, as part of their efforts to reduce the burden of healthcare expenditure and support children’s health from a social perspective. This study aimed to analyze the effect of cost sharing exemption for hospitalized children under the age of six in terms of National Health Insurance (NHI) beneficiaries’ healthcare utilization and healthcare expenditure and the quantity of healthcare services per episode. Methods: The data for this study was taken from the National Health Insurance Database (NHID) between 2004 and 2007 covering the entire population of South Korea. Considering that the cost sharing exemption policy was applied to children below six years of age, children classified as 1–5-year-olds who were enrolled in NHI from 2004 to 2007 were used as the case group, and the 7-year-olds were the control group. To investigate the NHI beneficiaries’ healthcare utilization, the case group (1–5-year-olds) included 2,720,180, 2,572,633, 2,333,808, and 2,230,946 subjects in 2004, 2005, 2006, and 2007, respectively. The control group (7-year-olds) included 649,225, 616,091, 584,144, and 600,370 subjects in 2004, 2005, 2006, and 2007, respectively. The dependent variables included the annual healthcare expenditure per NHI beneficiary, annual length of stay per NHI beneficiary, and annual number of admissions per NHI beneficiary. To investigate the healthcare expenditure and the quantity of healthcare services per episode, the case group (episodes from 1–5-year-olds) included 620,611 episodes in the before policy intervention (2004–2005) and 771,371 episodes in the after policy intervention (2006–2007) categories. The control group (episodes from 7-year-olds) included 52,315 episodes in the before policy intervention (2004–2005), and 59,953 episodes in the after policy intervention (2006–2007) categories. The dependent variables included the healthcare expenditure per episode, the length of stay per episode, and the healthcare expenditure per day per episode. Difference in differences was used to examine any changes in healthcare utilization among the case group (1–5-year-olds) in the before (2004–2005) and after (2006–2007) intervention periods, relative to changes in healthcare utilization of the control group (7-year-olds). This study constructed an interaction term between the case group in the after policy intervention period and applied generalized linear models using the GENMOD procedure. Results: The cost sharing exemptions for hospitalized children under the age of six were associated with an increase in healthcare utilization. Regarding the NHI beneficiaries’ healthcare utilization, the mean annual healthcare expenditure per NHI beneficiary for inpatient service before and after intervention were KRW 57,002 and KRW 90,611, respectively, in the case group, and KRW 24,416 and KRW 32,570, respectively, in the control group. The mean annual number of admissions per NHI beneficiary for inpatient service before and after intervention were 0.12 and 0.17, respectively, in the case group, and 0.04 and 0.05, respectively, in the control group. The mean annual length of stay per NHI beneficiary for inpatient service before and after intervention were 0.64 and 0.95, respectively, in the case group, and 0.22 and 0.27, respectively, in the control group. The cost sharing exemption was found to be significantly associated with an increased annual healthcare expenditure per NHI beneficiary, annual number of admissions per NHI beneficiary, and the annual length of stay per NHI beneficiary (annual healthcare expenditure: β = 0.1474, exp(β)=1.1588, SE = 0.0176, P = <.0001; annual number of admission: β = 0.1535, exp(β)=1.1659, SE = 0.0068, P = <.0001; annual length of stay: β = 0.1497, exp(β)=1.1615, SE = 0.0079, P = <.0001). There were no significant substitute effects were found between inpatient and outpatient services. Regarding healthcare service and expenditure per episode, the mean expenditure per inpatient episode before and after intervention were KRW 486,139 and KRW 536,212, respectively, in the case group, and KRW 590,545 and KRW 643,494, respectively, in the control group. The mean lengths of stay per episode for inpatient service before and after intervention were 5.42 and 5.62, respectively, in the case group, and 5.30 and 5.42, respectively, in the control group. The mean healthcare expenditure per day per episode for inpatient service before and after intervention were KRW 101,539 and KRW 106,328, respectively, in the case group, and KRW 137,087 and KRW 144,697, respectively, in the control group. The cost sharing exemption was found to be slightly associated with increased healthcare expenditure per episode for inpatient services (healthcare expenditure per episode: β = 0.0111, exp(β)=1.0112, SE = 0.0036, P = 0.0018). Results of inpatient service for mild disease analysis showed that the cost sharing exemption was associated with a decrease in healthcare expenditure per episode and length of stay per episode. Conclusions: Overall, the cost sharing exemption for hospitalized children under the age of six had increased the cost of healthcare services, mainly due to an increase in the quantity of healthcare services rather than the price of the service. While planning a cost sharing policy, it is crucial to consider all possible outcomes of how this policy will change healthcare utilization. This study has made a meaningful contribution to Korea’s health insurance policy by identifying the relationship between price and quantity responses to cost sharing exemptions. 서론: 아동의 건강은 미래 인적자본을 형성하는 핵심적 가치로서 평생 건강의 초석이 된다. 2006년 1월 1일부터 정부는 아동의 의료비용에 대한 가계부담을 덜어주고, 아동의 건강에 대한 사회적 지원여건 조성을 위해 만 6세미만 입원 아동이 요양기관에 입원할 경우 보험급여 적용 의료비 중 법정본인부담금을 면제하는 정책을 시행하였다. 그러나 건강보험재정 악화로 인해 2008년 1월부터 6세 미만 아동의 입원에 대해 10% 본인부담금을 부과하였다. 이 연구는 6세미만 입원본인부담 면제 정책 도입에 따른 소아 의료이용 변화를 분석하였다. 연구방법: 이 연구는 국민건강보험공단 맞춤형 데이터 2004-2007년 자료를 활용하여 한국 소아 인구 전수 자료를 활용하였다. 입원본인부담 면제 정책 대상이 만 6세 미만 건강보험 가입인구라는 점을 고려하여 2004-2007년 1-5세 건강보험 인구를 실험군으로, 2004-2007년 7세 건강보험 연구를 대조군으로 설정하였다. 정책 도입에 따른 6세미만 건강보험 가입자의 의료이용 변화를 분석하기 위해 실험군(1-5세 인구)은 2004년 2,720,180명, 2,572,633명, 2006년 2,333,808명, 2007년에 2,230,946명을 포함하였다. 대조군(7세 인구)은 2004년 649,225명, 2005년 616,091명, 2006년 584,144명, 2007년 600,370명을 포함하였다. 종속변수는 건강보험 가입자당 연간 진료비, 건강보험 가입자당 연간 재원일수와 건강보험 가입자당 연간 의료이용 횟수를 포함하였다. 정책도입에 따른 진료건당 의료비와 의료서비스량 변화를 분석하기 위해 실험군(1-5세 인구)의 입원진료건은 정책도입 이전(2004-2005년) 620,611건, 정책도입 이후(2006-2007년) 771,371건을 포함하였다. 대조군(7세 인구)의 입원진료건은 정책도입 이전(2004-2005년) 52,315건, 정책 도입 이후(2006-2007년) 59,953건이 포함되었다. 종속변수는 진료건 당 진료비, 진료건당 재원일수와 진료건당 일당 진료비가 포함되었다. 이중차분법(difference in differences)을 활용하여 실험군과 대조군에서 6세미만 입원본인부담 면제 정책 도입 전과 후 소아 의료이용 변화를 분석하였다. 연구결과: 6세 미만 입원본인부담 면제 정책은 소아의료이용 증가와 관련 있었다. 6세미만 입원본인부담 면제 정책 도입 전, 후 건강보험 가입자당 연간 입원 진료비 평균은 실험군에서 51,002원과 90,611원이었고, 대조군에서 24,415원과 32,570원이었다. 정책 도입 전, 후 건강보험 가입자당 연간 입원건수 평균은 실험군에서 0.12회와 0.17회, 대조군에서 0.04회와 0.05회였고, 건강보험 가입자당 연간 재원일수 평균은 실험군에서 0.64일과 0.95일, 대조군에서 각각 0.22일 및 0.27일이었다. 이중차분법 분석결과 6세미만 입원본인부담면제는 건강보험 가입자당 연간 입원 진료비 증가, 건강보험 가입자당 연간 입원건수 증가 및 건강보험 가입자당 연간 재원일수 증가와 관련 있는 것으로 확인되었다 (연간 입원진료비: β = 0.1474, exp(β)=1.1588, SE = 0.0176, P = <.0001; 연간 입원건수: β = 0.1535, exp(β)=1.1659, SE = 0.0068, P = <.0001; 연간 재원일수: β = 0.1497, exp(β)=1.1615, SE = 0.0079, P = <.0001). 전체(입원과 외래) 의료서비스에서 건강보험 가입자당 연간 진료비가 실험군이 대조군에 비해 증가하였고, 외래서비스에서 약간 증가한 것을 통해 입원과 외래의 대체재 효과는 관찰되지 않았다 (전체 의료서비스 건강보험 가입자당 연간 진료비: β = 0.0916, exp(β)=1.0959, SE = 0.0009, P = <.0001; 외래서비스 건강보험 가입자당 연간 진료비: β = 0.0115, exp(β)=1.0116, SE = 0.0014, P = <.0001). 6세미만 입원본인부담 면제 정책 전, 후 입원건당 진료비 평균은 실험군에서 486, 139원과 536,212원, 대조군에서 각각 590,545원, 643,494원이었다. 정책 도입 전, 후 입원건당 재원일수 평균은 실험군에서 5.42일 및 5.62일이었고, 대조군에서 5.30일 및 5.42일이었다. 정책 도입 전, 후 입원건당 일당 진료비 평균은 실험군에서 101,539원과 106,328원, 대조군에서 각각 137,087원 및 144,697원이었다. 이중차분법 분석결과 6세 미만 입원본인부담면제 도입 이후 실험군에서 입원건당 의료비 평균이 약간 증가하였다 (입원건당 진료: β= 0.0111, exp(β)=1.0112, SE = 0.0036, P = 0.0018). 경증질환 입원건당 분석 결과 정책 도입 후 실험군에서 진료건당 의료비와 진료건당 재원일수가 약간 감소하였다. 결론: 전반적으로 6세미만 입원본인부담 면제정책은 전체적인 의료서비스 비용을 증가시켰고, 이는 의료서비스 가격 측면보다 정책대상자의 의료서비스 이용량 증가에서 비롯된 결과임을 확인하였다. 건강보험의 본인부담금 설정 시 다양한 연구를 통해 본인부담 정도에 따른 가능한 의료이용 반응을 고려할 필요가 있다. 이 연구는 6세미만 입원본인부담 면제정책을 의료서비스 가격과 의료이용량 측면에서 나누어 분석함으로써 한국의 건강보험 보장성 강화정책 설계에 참고자료를 마련하였다. 추후 본인부담과 소아의료이용에 대한 활발한 연구를 통해 소아가 건강을 위한 다양하고 발전적인 건강보험 보장성 강화 정책 근거들이 제시되기를 기대한다.open박

KRAS 돌연변이 대장암세포주에서 분비된 MIF가 세툭시맙 내성에 미치는 기전 연구

학위논문 (박사)-- 서울대학교 대학원 : 의과대학 협동과정 종양생물학전공, 2018. 8. 김태유.The tumor microenvironment is recognized as a developing crosstalk between different cells by secretion of growth factors and cytokines thus providing oncogenic signals enhancing tumor progression and drug resistance. Here, I hypothesized that tumor cells carrying KRAS mutation-induced cytokines may have critical roles in intercellular communication between microenvironment and tumor cells. I first investigated biological evidence of secreted cytokines in KRAS mutant-type (KRASMT) cell lines. I explored the roles of cytokine that cell morphology, proliferation, colony formation, wound healing, and invasion ability were enhanced when KRAS wild-type (KRASWT) cells were exposed to conditioned media (CM) from KRASMT cells and I found macrophage migration inhibitory factor (MIF) was highly expressed in KRASMT cells by analysis of proteomics. I also observed secreted MIF level between KRASWT and KRASMT cells, and it was highly secreted in KRASMT cells. In addition, compared with colorectal cancer patients whose KRAS mutation was not harbored, MIF expression was higher in patients who have KRAS mutation. The predictive marker of KRAS mutation in colorectal cancer patients is associated with resistance to anti-epidermal growth factor receptor (EGFR) antibodies cetuximab (CTX). Following the hypothesis, I investigated that secreted cytokines from KRASMT cells have an effect on the cetuximab resistance to the surrounding cells including KRASWT cells. Treatment of CM led to cetuximab resistance in KRASWT cells and MIF blockade prevented cetuximab resistance. Moreover, CM from MIF knocked out KRASMT cells by using CRISPR/Cas9 system resulted in sensitizing to cetuximab resistance compared with treatment of CM from KRASMT cells. In conclusion, I demonstrated for the first time that MIF promoted the cetuximab resistance of KRASWT colorectal cancer cells, and this effect was mediated by paracrine and autocrine signaling-induced activation of the intracellular AKT signaling pathways and regulated by NF-kB transcription factor through oncogenic KRAS mutation. These findings suggest that MIF may be a promising predictive biomarker for the cetuximab resistance of KRAS wild-type colorectal cancer patients. INTRODUCTION 1 METERIALS AND METHODS 4 RESULTS - 12 DISCUSSION 55 REFERENCES 60 ABSTRACT IN KOREAN 65Docto

Event-Driven Simulation Methodology for Analog/Mixed-Signal Systems

학위논문 (박사)-- 서울대학교 대학원 : 전기·컴퓨터공학부, 2015. 8. 김재하.Recent system-on-chip's (SoCs) are composed of tightly coupled analog and digital components. The resulting mixed-signal systems call for efficient system-level behavioral simulators for fast and systematic verifications. As the system-level verifications rely heavily on digital verification tools, it is desirable to build the mixed-signal simulator based on a digital simulator. However, the existing solutions in digital simulators suffer from a trade-off between simulation speed and accuracy. This work breaks down the trade-off and realizes a fast and accurate analog/mixed-signal behavior simulation in a digital simulator SystemVerilog. The main difference of the proposed methodology from existing ones is its way of representing continuous-time signals. Specifically, a clock signal expresses accurate timing information by carrying an additional real-value time offset, and an analog signal represents its continuous-time waveform in a functional form by employing a set of coefficients. With these signal representations, the proposed method accurately simulates mixed-signal behaviors independently of a simulator's time-step and achieves a purely event-driven simulation without involving any numerical iteration. The speed and accuracy of the proposed methodology are examined for various types of analog/mixed-signal systems. First, timing-sensitive circuits (a phase-locked loops and a clock and data recovery loop) and linear analog circuits (a channel and linear equalizers) are simulated in a high-speed I/O interface example. Second, a switched-linear-behavior simulation is demonstrated through switching power supplies, such as a boost converter and a switched-capacitor converter. Additionally, the proposed method is applied to weakly nonlinear behaviors modeled with a Volterra series for an RF power amplifier and a high-speed I/O linear equalizer. Furthermore, the nonlinear behavior simulation is extended to three different types of injection-locked oscillators exhibiting time-varying nonlinear behaviors. The experimental results show that the proposed simulation methodology achieved tens to hundreds of speed-ups while maintaining the same accuracy as commercial analog simulators.ABSTRACT I CONTENTS III LIST OF FIGURES V LIST OF TABLES XII CHAPTER 1 INTRODUCTION 1 1.1 BACKGROUND 1 1.2 MAIN CONTRIBUTION 6 1.3 THESIS ORGANIZATION 8 CHAPTER 2 EVENT-DRIVEN SIMULATION OF ANALOG/MIXED-SIGNAL BEHAVIORS 9 2.1 PROPOSED CLOCK AND ANALOG SIGNAL REPRESENTATIONS 10 2.2 SIGNAL TYPE DEFINITIONS IN SYSTEMVERILOG 14 2.3 EVENT-DRIVEN SIMULATION METHODOLOGY 16 CHAPTER 3 HIGH-SPEED I/O INTERFACE SIMULATION 21 3.1 CHARGE-PUMP PHASE-LOCKED LOOP 23 3.2 BANGBANG CLOCK AND DATA RECOVERY 37 3.3 CHANNEL AND EQUALIZERS 45 3.4 HIGH-SPEED I/O SYSTEM SIMULATION 52 CHAPTER 4 SWITCHING POWER SUPPLY SIMULATION 55 4.1 BOOST CONVERTER 57 4.2 TIME-INTERLEAVED SWITCHED-CAPACITOR CONVERTER 66 CHAPTER 5 VOLTERRA SERIES MODEL SIMULATION 72 5.1 VOLTERRA SERIES MODEL 74 5.2 CLASS-A POWER AMPLIFIER 79 5.3 CONTINUOUS-TIME EQUALIZER 84 CHAPTER 6 INJECTION-LOCKED OSCILLATOR SIMULATION 89 6.1 PPV-BASED ILO MODEL 91 6.2 LC OSCILLATOR 99 6.3 RING OSCILLATOR 104 6.4 BURST-MODE CLOCK AND DATA RECOVERY 109 CONCLUSION 116 BIBLIOGRAPHY 118 초 록 126Docto

Lenalidomide for anemia correction in lower-risk del(5q) myelodysplastic syndrome patients of Asian ethnicity

Background: To estimate real-world outcomes in East Asian populations, we conducted a nationwide retrospective analysis of the efficacy and safety of lenalidomide for del(5q) myelodysplastic syndrome (MDS) patients with transfusion-dependent anemia in Korea. Methods: Patients aged ≥19 years who had received lenalidomide for the treatment of lower-risk, red blood cell (RBC) transfusion-dependent del(5q) MDS were selected. A filled case report form (CRF) with information from electronic medical records was requested from members of the acute myeloid leukemia (AML)/MDS Working Party of the Korean Society of Hematology. All the CRFs were gathered and analyzed. Results: A total of 31 patients were included in this study. Of 28 evaluable patients, 19 (67.9%) achieved RBC transfusion independence (RBC-TI). Female sex and the development of thrombocytopenia during treatment were associated with achieving RBC-TI. The most common non-hematologic toxicities were pruritus, fatigue, and rashes. All non-hematologic toxicities of grades ≥3 were limited to rash (12.9%) and pruritus (6.5%). Dose reduction was required in 15 of the 19 responders (78.9%). The most common final stable dosing schedule for the responders was 5 mg once every other day (31.6%). Conclusion: Lenalidomide efficacy and tolerability were similar in the Asian del(5q) MDS patients and western patients. Dose reduction during treatment was common, but it was not associated with inferior outcomes.ope

Survey for Government Policies Regarding Strategies for the Commercialization and Globalization of Digital Therapeutics

Purpose: This study was conducted to build a direction for government policies regarding strategies for the commercialization of digital therapeutics in Korea, as well as its globalization. Materials and methods: The study included 37 participants from the Korea Digital Health Industry Association (KODHIA). The data was based on a survey conducted in 2020 targeting employees of companies engaged in the digital health industry in Korea. Participants were asked about their involvement in product development of digital therapeutics and their opinion about the growing motivator for digital therapeutics in Korea and the global market. Results: According to our data, among subjects not involved in making digital therapeutics products, the main reason for not being involved was the lack of experts (73.9%) and difficulty in licensing (73.9%). Responses concerning the priority area in need of national support were R&amp;D funding (43.2%), and the next was licensing guidance and simplifying regulations (24.3%). Possible difficulties of overseas market expansion were the unfamiliarity in digital therapeutics technology verification and licensing structures of foreign countries (73%), and concerns regarding the level of recognition of clinical trials and technology in Korea from overseas (70.3%). Overall, respondents were hesitant in starting a related business due to the lack of government support and the complexity of the regulation process. Moreover, concerns about global market entry were similar. Being unfamiliar with the novel process and worrying about the achievement despite existing challenges were the biggest drawback. Conclusion: For the digital therapeutics industry to evolve domestically and internationally, government support and guidance are essential.ope

Single monosomy as a relatively better survival factor in acute myeloid leukemia patients with monosomal karyotype

Monosomal karyotype (MK) defined by either ⩾2 autosomal monosomies or single monosomy with at least one additional structural chromosomal abnormality is associated with a dismal prognosis in patients with acute myeloid leukemia (AML). It was detected in 174 of 3041 AML patients in South Korean Registry. A total of 119 patients who had received induction therapy were finally analyzed to evaluate the predictive factors for a positive prognosis. On multivariate analysis, single monosomy, the absence of abn(17p), ⩾10% of cells with normal metaphase and the achievement of a complete remission (CR) after induction therapy were significant factors for more favorable outcomes. Especially, single monosomy remained as a significantly independent prognostic factor for superior survival in both patients who received allogeneic hematopoietic stem cell transplantation (allo-HSCT) in CR and who did not. Allo-HSCT in CR improved overall survival significantly only in patients with a single monosomy. Our results suggest that MK-AML may be biologically different according to the karyotypic subtype and that allo-HSCT in CR should be strongly recommended to patients with a single monosomy. For other patients, more prudent treatment strategies should be examined. Furthermore, the biological mechanism by which a single monosomy influences survival should be investigated.ope

A scoping review on population-centered indicators for cancer care continuum

Purpose: The purpose of this study was to develop prioritized cancer indicators and measure the population-based monitoring of the entire life cycle of cancer care, guiding the improvement of care delivery systems. Methods: Scoping review was performed based on the Joanna Briggs Institute's methodology. Electronic databases were searched in PubMed, Cochrane Library, EMBASE, Ovid Medline, RISS, KISS, and KoreaMed. The searches were limited to articles published in English between 2010 and 2020. No restrictions were applied regarding the publication status or country of origin, and all study designs were included. Gray literature was used to broaden the search's scope, identify new recommendations, need to be in connect with subject experts, and explore pertinent websites. The process and selected indicators were analyzed based on their frequency distribution and percentage. Results: The literature search yielded 6,202 works. In addition, national and international cancer guidelines were obtained from official database reports. A total of 35 articles and 20 reports regarding cancer indicators were finally selected for data synthesis. Based on them, 254 core sets of cancer indicators were identified. The selected indicators were classified into six domains based on the continuum of cancer care and survivor's life cycle, namely, primary prevention (61, 24.0%), secondary prevention (46, 18.1%), treatment (85, 33.5%), quality of care (33, 13.0%), survivor management (33, 13.0%), and end-of-life care (14, 5.5%). Conclusion: There is a growing interest in developing specific areas of cancer care. Cancer indicators can help organizations, care providers, and patients strive for optimal care outcomes. The identified indicators could guide future innovations by identifying weaknesses in cancer prevention and management.ope

Unmet Healthcare Needs Status and Trend of Korea in 2017

Unmet healthcare needs are being used as an important indicator of the accessibility of healthcare services worldwide. To examine current status and trends of unmet needs in Korea, we used data from four sources: the Korea National Health and Nutrition Examination Survey (KNHANES, 2007–2017); the Community Health Survey (CHS 2008–2017); the Korea Health Panel Survey (KHP 2011– 2015); and the Korean Welfare Panel Study (KOWEPS 2006–2017). The proportion of individual reporting unmet healthcare needs as of 2017 was 8.8% (KNHANES), 10.6% (CHS), and 12.4% (KHP as of 2015). The proportion of households reporting unmet healthcare needs due to cost was 0.5% (KOWEPS). Annual percentage change was -19.2%, -13.3%, -5.8%, and -13.3% respectively. Low income populations had more unmet healthcare needs than high income populations. However, unlike the last two studies, the main reason for unmet medical reasons was that there was no time regardless of income level.open22Nkc

Therapy-related Acute Lymphoblastic Leukaemia has a Unique Genetic Profile Compared to De Novo Acute Lymphoblastic Leukaemia

Background: Unlike therapy-related myeloid neoplasms, therapy-related acute lymphoblastic leukaemia (tr-ALL) is poorly defined due to its rarity. However, increasing reports have demonstrated that tr-ALL is a distinct entity with adverse genetic features and clinical outcomes. Methods: We compared the clinicopathological characteristics and outcomes of patients diagnosed with tr-ALL (n = 9) or de novo ALL (dn-ALL; n = 162) at a single institution from January 2012 to March 2021. The mutational landscapes of eight tr-ALL and 63 dn-ALL patients were compared from a comprehensive next-generation sequencing panel. Results: All tr-ALL patients had the B-cell phenotype. The most frequently mutated genes were IKZF1 (37%), CDKN2A (14%), SETD2 (13%), and CDKN2B (11%) in dn-ALL, whereas TP53 (38%) and RB1 (25%) mutations were most common in tr-ALL. tr-ALL patients did not show a statistically significant difference in overall survival (p = 0.70) or progression-free survival (p = 0.94) compared to dn-ALL patients. Conclusions: In this study, we determined the clinical and genetic profiles of Korean patients with tr-ALL. We found alterations in genes constituting the TP53/RB1 pathway are more frequent in tr-ALL. Due to the rarity of the disease, multi-institutional studies involving a larger number of patients are required in future study.ope

Arsenic trioxide synergistically promotes the antileukaemic activity of venetoclax by downregulating Mcl-1 in acute myeloid leukaemia cells

Background: The evasion of apoptosis through dysregulated Bcl-2 family members is a hallmark of leukaemia stem cells (LSCs) in acute myeloid leukaemia (AML). Therefore, targeting Bcl-2 with venetoclax has been suggested as an attractive strategy for inducing apoptosis in AML LSCs. However, the selective inhibition of Bcl-2 in AML often leads to upregulation of Mcl-1, another dominant anti-apoptotic Bcl-2 family protein conferring venetoclax resistance. Methods: We assessed the combined effect of venetoclax and arsenic trioxide (ATO) on leukaemic cell viability, apoptosis, combination index, and cell cycle in the human LSC-like KG1 and KG1a cells. The synergistic effect of venetoclax and ATO on apoptosis was also examined in primary CD34+ and CD34+CD38- LSCs from the bone marrow (BM) of AML patients, and compared with those from healthy donors. Results: Venetoclax efficiently impaired cell viability and dose-dependently promoted apoptosis when combined with ATO; their synergism was aptly represented by the combination index. The combination of venetoclax and ATO impaired cell cycle progression by restricting cells within the sub-G1 phase and facilitating caspase-dependent apoptotic cell death associated with the loss of mitochondrial membrane potential, while sparing healthy BM haematopoietic stem cells. Mechanistically, ATO mitigated venetoclax-induced upregulation of Mcl-1 by the inhibition of AKT and ERK, along with activation of GSK-3β. This led to the Mcl-1 destabilisation, triggering Noxa and Bim to facilitate apoptosis and the consequent activation of the apoptosis executioner protein Bak. Moreover, the combination promoted phosphorylation of ATM, Chk2, p38, and H2AX, indicating an active DNA damage response. Conclusions: Our findings demonstrate the synergistic, preferential antileukaemic effects of venetoclax and ATO on LSCs, providing a rationale for preclinical and clinical trials by combining these agents already being used in clinical practice to treat acute leukaemia.ope