Prognostic value of metabolic tumor volume of extranodal involvement in diffuse large B cell lymphoma.

Extranodal involvement predicts poor outcomes of diffuse large B cell lymphoma (DLBCL), but the impact of the metabolic tumor burden (MTV) of extranodal sites using positron emission tomography has not been clarified. This study aimed to assess the impact of extranodal MTV on overall survival (OS). We retrospectively analyzed 145 newly diagnosed DLBCL patients and verified the prognostic impact of each extranodal and nodal MTV. Multivariate Cox hazards modelling using both extranodal and nodal MTV as covariables identified extranodal MTV as a significant factor for OS (hazard ratio [HR] 1.072, 95% confidence interval [CI] 1.019-1.129, P = 0.008), but not nodal MTV. Multivariate Cox modelling using restricted cubic splines demonstrated that the impact of total MTV depends on the MTV of extranodal sites, not of nodal sites. When both the number and MTV of extranodal involvements were used as covariables, extranodal MTV remained a significant predictor of OS (HR 1.070, 95%CI 1.017-1.127, P = 0.009), but the number of extranodal sites did not. Extranodal MTV potentially had a more significant role on prognosis than nodal MTV. When considering prognostic impacts, the MTV of extranodal involvement is significantly more important than the number.

Estimated excretion and clearance of uric acid as optimal surrogate indices for daily urinary uric acid excretion.

OBJECTIVES: Daily uric acid excretion is an essential index for patients with gout/hyperuricemias. We identified alternative indices most correlated with 24-hour uric acid clearance (Cua 24h) and 24-hour uric acid excretion (Eua 24h) using data from the reference interval of urinary clearance and excretion of urate study. METHODS: The subjects were indoor workers aged 20 to 65 who met the Clinical and Laboratory Standards Institute Guidelines C28-A3c. Alternative indices using spot urine were urine uric acid creatinine ratio, uric acid clearance - creatinine clearance ratio (Cua/Ccr), uric acid excretion - creatinine clearance ratio (Eua/Ccr), estimated uric acid clearance (eCua), and estimated uric acid excretion (eEua). eCua and eEua are the values obtained by multiplying Cua/Ccr and Eua/Ccr by the estimated glomerular filtration rate. RESULTS: The final number of subjects analyzed was 739. Among the indices using spot urine, eCua and eEua showed the highest correlation with Cua 24h and Eua 24h, respectively. Compared with Cua 60min and Eua 60min obtained from 60-minute urine collection, eCua and eEua showed lower root means squared error, lower bias, and significantly higher accuracy of within 30% and within 15%. CONCLUSIONS: The newly proposed eCua and eEua may be appropriate from a practical perspective.

Prognostic utility of a geriatric nutritional risk index in combination with a comorbidity index in elderly patients with diffuse large B cell lymphoma.

Reflecting the increasing risk in elderly patients with diffuse large B cell lymphoma (DLBCL), prognostic predictors other than the International Prognostic Index have attracted more attention. This study presents the first analysis of the prognostic utility of the Geriatric Nutritional Risk Index (GNRI) in combination with the Charlson Comorbidity Index (CCI) for overall survival (OS) in elderly DLBCL patients. A multicentre retrospective was conducted on a cohort of 451 patients (≥65 years). The GNRI and CCI were independent predictors in a multivariate Cox proportional hazard model. There was a nonlinear correlation between the GNRI and OS in a Cox model with restricted cubic spline. Multivariate receiver operating characteristic curves showed a significant improvement in prediction accuracy when the GNRI was added to CCI. Adding the GNRI to CCI yielded a significant category-free net reclassification improvement (0·556; 95% CI: 0·378-0·736, P < 0·001) and integrated discrimination improvement (0·094; 95% CI: 0·067-0·122, P < 0·001). The decision curve analysis demonstrated the clinical net benefit associated with the adoption of the GNRI. The GNRI was not only a predictor of OS but also remarkably improved the prognosis prediction accuracy when incorporated with the CCI, having the ability to stratify the prognosis of elderly DLBCL patients.

Association of the Geriatric 8 with treatment intensity and prognosis in older patients with diffuse large B-cell lymphoma.

Because of the heterogeneity among older patients with diffuse large B-cell lymphoma (DLBCL), the establishment of an easy-to-use geriatric assessment tool is an unmet need. We verified the impact of the Geriatric 8 (G8) on treatment stratification and overall survival (OS). We conducted a retrospective, multicentre analysis of older patients (≥65 years) with DLBCL. The primary endpoint was OS. The total average relative dose intensity (tARDI) was defined as the average delivered dose intensity divided by the planned dose intensity through all cycles. A total of 451 patients were diagnosed with DLBCL from 2007 to 2017, and 388 patients received standard regimens. A multivariate Cox model confirmed that the G8 was a significant predictor of OS (hazard ratio 0·88, 95% confidence interval 0·828-0·935). A Cox model with restricted cubic spline showed a linear association between the G8 and the mortality risk. The G8 had a significant impact on OS in elderly patients with DLBCL. The upper limit of tARDI for standard regimens to improve OS might be appropriate at ≥80% for patients with high G8 scores and 60% for patients with low G8 scores. However, the standard regimens should be given to all patients regardless of the G8 score to improve OS.

Utility of the Geriatric 8 for the Prediction of Therapy-Related Toxicity in Older Adults with Diffuse Large B-Cell Lymphoma.

BACKGROUND: The management of severe adverse events (AEs) is important in safely and effectively providing chemotherapy to older adults with diffuse large B-cell lymphoma (DLBCL). However, reports on simple and DLBCL-specific predictive models for treatment-related toxicity in elderly individuals are scarce. The aim of this study was to examine the usefulness of Geriatric 8 (G8) in predicting treatment-related severe AEs, nonhematological toxicity, and febrile neutropenia in older adults with DLBCL in real-world practice. MATERIALS AND METHODS: We conducted a multicenter, retrospective study on 398 consecutive patients with DLBCL (aged ≥65 years) who received standard therapy at three centers in Japan (University of Fukui Hospital, the Fukui Prefectural Hospital, and the Japanese Red Cross Fukui Hospital), between 2007 and 2017. RESULT: Multivariate logistic analysis demonstrated that the G8 score was an independent predictive factor for severe AEs. Moreover, a logistic regression model with restricted cubic spline showed a nonlinear association between the incidence of severe AEs and the G8 score. According to receiver operating characteristic analysis, the most discriminative cutoff value of the G8 for the incidence of severe AEs was 11, with an area under the curve value of 0.670. AEs occurred most often in the first course of chemotherapy and decreased as the course progressed. CONCLUSION: The G8 score, an easy-to-use geriatric assessment tool, can be a useful prediction model of treatment-related severe AEs during standard therapy in older adults with DLBCL. IMPLICATIONS FOR PRACTICE: In older patients with diffuse large B-cell lymphoma (DLBCL), to accurately predict the risk of severe adverse events (AEs) in advance is essential for safe and effective treatment. This study demonstrated that the Geriatric 8 score, a simple and established geriatric assessment tool, indicated a high predictive ability for occurrence of therapy-related severe AEs in elderly patients with DLBCL who were treated with standard treatment.

The impact of diagnostic wait time on the survival of patients with diffuse large B-cell lymphoma: effect modification by the International Prognostic Index.

Despite the importance of a prompt diagnosis to improve cancer patients' survival, little has been reported on diagnostic delay in diffuse large B-cell lymphoma (DLBCL). A single-centre, retrospective study was conducted to examine the association between diagnostic wait time (DWT), the interval from the initial hospital visit to diagnosis, and survival in patients with DLBCL. A total of 193 patients were enrolled from 2007 to 2017 in our institution. A covariate-adjusted Cox proportional hazards model with restricted cubic spline was used to evaluate the impact of DWT on survival, with a subgroup analysis according to the International Prognostic Index (IPI). DWT was not associated with survival in the entire DLBCL population, but the impact of DWT on survival differed between IPI < 3 and ≥ 3; prolongation of DWT steadily exacerbated the prognosis in patients with IPI ≥ 3, whereas there was a patient population with IPI < 3 who had a high mortality rate despite rather early diagnosis. The opposite trend in the effect of DWT on survival between patients with IPI < 3 and ≥ 3 offset survival in all DLBCL patients. DWT had no observable impact on outcomes in the entire DLBCL population, but longer DWT worsened the prognosis, particularly in patients with IPI ≥ 3.

[Evaluation of Chemotherapy-Induced Nausea and Vomiting in Patients with Hematological Malignancies Using MASCC Antiemesis Tool(MAT)].

Chemotherapy-induced nausea and vomiting(CINV)were prospectively evaluated using MASCC Antiemesis Tool(MAT) in patients with hematological malignancies in our institution. A total of 33 patients receiving 46 chemotherapy courses were evaluated. Although vomiting was not observed in the acute phase, nausea was seen in 22.6% and 32.3% of the patients in the acute and delayed phases, respectively. Thirty percent(25 cases)of the patients receiving highly emetogenic chemotherapy presented nausea in both the phases, while 40%(18 cases)of the patients receiving moderately emetogenic chemotherapy presented nausea in the delayed phase. The oral intake was quantitated retrospectively in 31 patients with non- Hodgkin's lymphoma, who were hospitalized and received CHOP±R. Prior to the initiation of the chemotherapy, 13 patients received the first generation 5-HT3 receptor antagonist granisetron, while 18 patients received the second generation palonosetron. Oral intake was greater in the patients who were administered palonosetron. Thus, the present study suggested that antiemetic treatment could be improved at our institution.

Combination of panobinostat with ponatinib synergistically overcomes imatinib-resistant CML cells.

The major mechanism of imatinib (IM) resistance of CML is the reactivation of ABL kinase either through BCR-ABL gene amplification or mutation. We investigated the cytotoxicity of a pan-ABL tyrosine kinase inhibitor, ponatinib, and a pan-histone deacetylase inhibitor, panobinostat, against IM-resistant CML cells in vitro. Two different IM-resistant cell lines, K562/IM-R1 and Ba/F3/T315I were evaluated in comparison with their respective, parental cell lines, K562 and Ba/F3. K562/IM-R1 overexpressed BCR-ABL due to gene amplification. Ba/F3/T315I was transfected with a BCR-ABL gene encoding T315I-mutated BCR-ABL. Ponatinib inhibited the growth of both K562/IM-R1 and Ba/F3/T315I as potently as it inhibited their parental cells with an IC50 of 2-30 nM. Panobinostat also similarly inhibited the growth of all of the cell lines with an IC50 of 40-51 nM. This was accompanied by reduced histone deacetylase activity, induced histone H3 acetylation, and an increased protein level of heat shock protein 70, which suggested disruption of heat shock protein 90 chaperone function for BCR-ABL and its degradation. Importantly, the combination of ponatinib with panobinostat showed synergistic growth inhibition and induced a higher level of apoptosis than the sum of the apoptosis induced by each agent alone in all of the cell lines. Ponatinib inhibited phosphorylation not only of BCR-ABL but also of downstream signal transducer and activator of transcription 5, protein kinase B, and ERK1/2 in both K562/IM-R1 and Ba/F3/T315I, and the addition of panobinostat to ponatinib further inhibited these phosphorylations. In conclusion, panobinostat enhanced the cytotoxicity of ponatinib towards IM-resistant CML cells including those with T315I-mutated BCR-ABL.

Efficacy and safety of febuxostat for prevention of tumor lysis syndrome in patients with malignant tumors receiving chemotherapy: a phase III, randomized, multi-center trial comparing febuxostat and allopurinol.

BACKGROUND: Control of serum uric acid (sUA) levels is very important during chemotherapy in patients with malignant tumors, as the risks of tumor lysis syndrome (TLS) and renal events are increased with increasing levels of sUA. We investigated the efficacy and safety of febuxostat, a potent non-purine xanthine oxidase inhibitor, compared with allopurinol for prevention of hyperuricemia in patients with malignant tumors, including solid tumors, receiving chemotherapy in Japan. METHODS: An allopurinol-controlled multicenter, open-label, randomized, parallel-group comparative study was carried out. Patients with malignant tumors receiving chemotherapy, who had an intermediate risk of TLS or a high risk of TLS and were not scheduled to be treated with rasburicase, were enrolled and then randomized to febuxostat (60 mg/day) or allopurinol (300 or 200 mg/day). All patients started to take the study drug 24 h before chemotherapy. The primary objective was to confirm the non-inferiority of febuxostat to allopurinol based on the area under the curve (AUC) of sUA for a 6-day treatment period. RESULTS: Forty-nine and 51 patients took febuxostat and allopurinol, respectively. sUA decreased over time after initiation of study treatment. The least squares mean difference of the AUC of sUA between the treatment groups was -33.61 mg h/dL, and the 95 % confidence interval was -70.67 to 3.45, demonstrating the non-inferiority of febuxostat to allopurinol. No differences were noted in safety outcomes between the treatment groups. CONCLUSION: Febuxostat demonstrated an efficacy and safety similar to allopurinol in patients with malignant tumors receiving chemotherapy. TRIAL REGISTRY: http://www.clinicaltrials.jp ; Identifier: JapicCTI-132398.

Evaluation of staging and early response to chemotherapy with whole-body diffusion-weighted MRI in malignant lymphoma patients: A comparison with FDG-PET/CT.

BACKGROUND: To examine the utility of diffusion-weighted MRI (DW-MRI) for staging and early response to chemotherapy assessment in lymphoma patients as compared with fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT). METHODS: Twenty-eight patients with histologically confirmed malignant lymphoma underwent both MRI and FDG-PET/CT before (pretreatment) and after two courses of chemotherapy (mid-treatment). Staging with MRI (DW-MRI alone and with T2-weighted images) and FDG-PET was compared visually, and the concordance rate (kappa value, κ) was calculated. To evaluate early response to chemotherapy, patients were divided into two groups, lesion-positive (LP) and lesion-negative (LN), based on a proposed original criterion. Progression-free survival (PFS) was compared between the groups using the Kaplan-Meier method. RESULTS: The stage diagnosed with DW-MRI alone and with FDG-PET/CT was concordant in 22 patients (κ = 0.71; P < 0.05), and by adding T2-weighted images, the number of concordant patients increased to 26 (κ = 0.90; P < 0.05). On mid-treatment imaging, 19 patients were diagnosed as LN from both modalities. PFS differed significantly between LP and LN on both DW-MRI (P = 0.0013) and FDG-PET/CT (P = 0.037). CONCLUSION: DW-MRI is a promising tool for staging and evaluation of early response to chemotherapy in patients with lymphoma.

Effects of febuxostat on serum urate level in Japanese hyperuricemia patients.

OBJECTIVE: We assessed the efficacy and adverse effects of febuxostat in male hyperuricemia patients. SUBJECTS AND METHODS: This was a 12-week, multicenter, open-label, uncontrolled study. The enrolled subjects were 89 hyperuricemic male patients (12 overexcretors, 56 normal excretors, and 21 underexcretors). The endpoint was percent change in serum urate level. RESULTS: The concentration of urate in serum before and 12 weeks after beginning administration of febuxostat in the overexcretors was 9.34 ± 1.48 and 5.59 ± 1.17 mg/dl, respectively, while those were 8.59 ± 1.24 and 5.41 ± 1.35 mg/dl, respectively, in the normal excretors, and 8.29 ± 1.01and 5.11 ± 1.71 mg/dl, respectively, in the underexcretors. After 12 weeks, the rate of change in serum urate after beginning administration of febuxostat was - 0.384 ± 0.186 in the overexcretors, - 0.368 ± 0.128 in the normal excretors, and - 0.365 ± 0.217 in the underexcretors, with no significant differences among them. A common adverse event related to febuxostat was gout flare. CONCLUSION: Febuxostat effectively reduced the concentration of urate in serum in hyperuricemic patients regardless of the level of uric acid excreted in urine without severe adverse effects.

Significantly higher cytokine and chemokine levels in patients with Japanese spotted fever than in those with Tsutsugamushi disease.

Tetracyclines are administered to cure Japanese spotted fever (JSF) and tsutsugamushi disease (TD). It is generally said that the clinical course of JSF is worse than that of TD despite antibiotic treatment. The precise mechanism underlying the more severe clinical course of JSF is not fully understood. We therefore examined whether the differential cytokine profile between these two infectious diseases contributes to the difference in clinical severity. The serum concentrations of various cytokines (tumor necrosis factor alpha [TNF-α], interleukin-6 [IL-6], and gamma interferon [IFN-γ]) and chemokines (IL-8, interferon-inducible protein 10 [IP-10], monocyte chemoattractant protein 1 [MCP-1], macrophage inflammatory protein 1α [MIP-1α], MIP-1ß, and eotaxin) were measured in 32 TD and 21 JSF patients. The results showed that serum levels of TNF-α in the acute phases of TD and JSF were significantly increased, with a higher concentration of TNF-α in patients with JSF (mean, 39.9 pg/ml) than in those with TD (mean, 13.8 pg/ml). Comparatively higher levels of other cytokines and chemokines (IL-6, IFN-γ, IL-8, IP-10, MCP-1, MIP-1α, and MIP-1ß) were also observed in the acute phase of JSF. The clinical severity score (3.67 ± 1.71) of JSF patients was higher than that of TD patients (1.47 ± 0.77). Our findings revealed that the cytokine and chemokine levels in the acute phase of JSF were significantly higher than those in the acute phase of TD. The differential cytokine levels may be related to the difference in clinical severity between JSF and TD.

Reduced drug incorporation into DNA and antiapoptosis as the crucial mechanisms of resistance in a novel nelarabine-resistant cell line.

BACKGROUND: Nine-beta-D-arabinofuranosylguanine (ara-G), an active metabolite of nelarabine, enters leukemic cells through human Equilibrative Nucleoside Transporter 1, and is then phosphorylated to an intracellular active metabolite ara-G triphosphate (ara-GTP) by both cytosolic deoxycytidine kinase and mitochondrial deoxyguanosine kinase. Ara-GTP is subsequently incorporated into DNA, thereby inhibiting DNA synthesis. METHODS: In the present study, we developed a novel ara-G-resistant variant (CEM/ara-G) of human T-lymphoblastic leukemia cell line CCRF-CEM, and elucidated its mechanism of ara-G resistance. The cytotoxicity was measured by using the growth inhibition assay and the induction of apoptosis. Intracellular triphosphate concentrations were quantitated by using HPLC. DNA synthesis was evaluated by the incorporation of tritiated thymidine into DNA. Protein expression levels were determined by using Western blotting. RESULTS: CEM/ara-G cells were 70-fold more ara-G-resistant than were CEM cells. CEM/ara-G cells were also refractory to ara-G-mediated apoptosis. The transcript level of human Equilibrative Nucleoside Transporter 1 was lowered, and the protein levels of deoxycytidine kinase and deoxyguanosine kinase were decreased in CEM/ara-G cells. The subsequent production of intracellular ara-GTP (21.3 pmol/107 cells) was one-fourth that of CEM cells (83.9 pmol/107 cells) after incubation for 6 h with 10 µM ara-G. Upon ara-G treatment, ara-G incorporation into nuclear and mitochondrial DNA resulted in the inhibition of DNA synthesis of both fractions in CEM cells. However, DNA synthesis was not inhibited in CEM/ara-G cells due to reduced ara-G incorporation into DNA. Mitochondrial DNA-depleted CEM cells, which were generated by treating CEM cells with ethidium bromide, were as sensitive to ara-G as CEM cells. Anti-apoptotic Bcl-xL was increased and pro-apoptotic Bax and Bad were reduced in CEM/ara-G cells. CONCLUSIONS: An ara-G-resistant CEM variant was successfully established. The mechanisms of resistance included reduced drug incorporation into nuclear DNA and antiapoptosis.

[Sudden blast crisis of chronic myeloid leukemia after a 13-year durable remission following allogeneic bone marrow transplantation and donor lymphocyte infusion].

We describe a rare case of sudden blast crisis of chronic myeloid leukemia that occurred after a 13-year durable remission, following allogeneic bone marrow transplantation and donor lymphocyte infusion. A 55-year-old Japanese man was diagnosed with chronic-phase chronic myeloid leukemia 24 years previously. He underwent allogeneic bone marrow transplantation 2 years after diagnosis. Although the disease recurred 6 years after transplantation, the patient achieved remission again by a donor lymphocyte infusion. Despite a 13-year durable remission, the disease later relapsed into a sudden blast crisis. Prednisolone and vincristine combined with imatinib mesylate effectively achieved a major molecular response. However, the disease relapsed repeatedly with central nervous system infiltration. Dasatinib and intrathecal methotrexate, cytarabine, and dexamethasone administration via the Ommaya reservoir controlled disease progression. Nevertheless, the disease became refractory to treatment with the emergence of a T315I Bcr-Abl gene mutation. The patient eventually died 43 months post crisis.

[Chemotherapy].

The progress of cancer chemotherapy has made a large contribution to the significant improvement of cure rate in patients with hematological malignancy including malignant lymphoma. Interpatient variability characterizes the disposition of many drugs. In the case of drugs with a wide therapeutic index, such variability is unlikely to affect either clinical efficacy or toxicity. With anticancer drugs, however, there is much less margin for error, due to their very narrow therapeutic index. Therefore, it is crucially important to understanding the mechanism of action, pharmacokinetics and pharmacodynamics of each anticancer drug in order to give chemotherapy in safety. Overview of the pharmacological functions of anticancer agent using in malignant lymphoma is the subject of this chapter.

Clinical Features of Clonal Cytogenetic Abnormalities in Philadelphia-negative Cells Developed During Tyrosine Kinase Inhibitor Treatment.

Most clonal cytogenetic abnormalities of Philadelphia-negative cells (CCA/Ph-) occurring during tyrosine kinase inhibitor (TKI) treatment are transient, and the development of secondary myelodysplastic syndrome (MDS)/acute myeloid leukemia (AML) is rare, but the frequency and clinical significance in Japanese patients are still unknown. We herein report four patients who developed CCA/Ph- during TKI therapy and were diagnosed with secondary MDS/AML. The duration from TKI therapy initiation to MDS/AML onset ranged from 3 to 48 months, and the survival ranged from 5 to 84 months. The occurrence of CCA/Ph- with MDS/AML may be associated with a poor prognosis, and careful follow-up is recommended for patients who receive TKI therapy.

Estimate hidden dynamic profiles of siRNA effect on apoptosis.

BACKGROUND: For the representation of RNA interference (RNAi) dynamics, several mathematical models based on systems of ordinary differential equations (ODEs) have been proposed. These models consist of equations for each molecule that are involved in RNAi phenomena. Therefore, many real-value parameters must be optimized to identify the models. They also have many 'hidden variables', which cannot be observed directly through experimentation. Calculation of the values of the hidden variables is generally very difficult, if not impossible in some special cases. Identification of the ODE models is also quite difficult. RESULTS: We show that the simplified logistic Lotka-Volterra model, a well-established ODE model for biological and biochemical phenomena, can represent RNAi dynamics as a predator-prey system. Although a hidden variable exists in the model, its values can be determined and made visible as dynamic profiles of RNA-decomposing effects of siRNAs. Correlation analysis shows that the model parameters correlate highly with the total effect of the siRNA. CONCLUSIONS: The results suggest that analyses using our model are useful to estimate dynamic profiles of siRNA effects on apoptosis and to score siRNA by its effects on apoptosis, namely 'phenotypic scoring'.

Novel leukemic cell lines resistant to clofarabine by mechanisms of decreased active metabolite and increased antiapoptosis.

Clofarabine (CAFdA) is incorporated into leukemic cells by human equilibrative nucleoside transporters (hENT) 1 and 2 and human concentrative nucleoside transporter (hCNT) 3. CAFdA is then phosphorylated to the active metabolite CAFdA triphosphate (CAFdATP) by deoxycytidine kinase (dCK) and deoxyguanosine kinase (dGK). Two novel CAFdA-resistant variants were established and their mechanism of resistance was elucidated. The two variants (HL/CAFdA20, HL/CAFdA80) were 20-fold and 80-fold more CAFdA-resistant than HL-60, respectively. mRNA levels of hENT1, hENT2 and hCNT3 were 53.9, 41.8 and 17.7% in HL/CAFdA20, and 30.8, 13.9 and 7.9% in HL/CAFdA80, respectively, compared with HL-60. Thus, the total nucleoside transport capacity of CAFdA was reduced in both variants. dCK protein levels were 1/2 in HL/CAFdA20 and 1/8 in HL/CAFdA80 of that of HL-60. dGK protein levels were 1/2 and 1/3, respectively. CAFdATP production after 4-h incubation with 10 µM CAFdA was 20 pmol/10(7) cells in HL/CAFdA20 and 3 pmol/10(7) cells in HL/CAFdA80 compared with 63 pmol/10(7) cells in HL-60. The decreased CAFdATP production attenuated drug incorporation into both mitochondrial and nuclear DNA. In addition, the two variants were resistant to CAFdA-induced apoptosis due to Bcl2 overexpression and decreased Bim. A Bcl2 inhibitor, ABT737, acted synergistically with CAFdA to inhibit the growth with combination index values of 0.27 in HL/CAFdA20 and 0.23 in HL/CAFdA80, compared with 0.65 in HL-60. Thus, the mechanism of resistance primarily included not only reduced CAFdATP production, but also increased antiapoptosis. The combination of CAFdA and ABT737 may be effective against CAFdA resistance.

Combination of guanine arabinoside and Bcl-2 inhibitor YC137 overcomes the cytarabine resistance in HL-60 leukemia cell line.

Cytarabine (ara-C) is the key agent for treating acute myeloid leukemia. After being transported into leukemic cells, ara-C is phosphorylated, by several enzymes including deoxycytidine kinase (dCK), to ara-C triphosphate (ara-CTP), an active metabolite, and then incorporated into DNA, thereby inhibiting DNA synthesis. Therefore, the cytotoxicity of ara-C depends on the production of ara-CTP and the induction of apoptosis. Here, we established a new ara-C-resistant acute myeloid leukemia cell line (HL-60/ara-C60) with dual resistance characteristics of the anti-antimetabolic character of decreased ara-CTP production and an increase in the antiapoptotic factors Bcl-2 and Bcl-XL. We further attempted to overcome resistance by augmenting ara-CTP production and stimulating apoptosis. A relatively new nucleoside analog, 9-ß-d-arabinofuranosylguanine (ara-G), and the small molecule Bcl-2 antagonist YC137 were used for this purpose. HL-60/ara-C60 was 60-fold more ara-C-resistant than the parental HL-60 cells. HL-60/ara-C60 cells exhibited low dCK protein expression, which resulted in decreased ara-CTP production. HL-60/ara-C60 cells were also refractory to ara-C-induced apoptosis due to overexpression of Bcl-2 and Bcl-XL. Combination treatment of ara-C with ara-G augmented the dCK protein level, thereby increasing ara-CTP production and subsequent cytotoxicity. Moreover, the combination of ara-C with YC137 produced a greater amount of apoptosis than ara-C alone. Importantly, the three-drug combination of ara-C, ara-G and YC137 provided greater cytotoxicity than ara-C+ara-G or ara-C+YC137. These findings suggest possible combination strategies for overcoming ara-C resistance by augmenting ara-CTP production and reversing refractoriness against the induction of apoptosis in ara-C resistant leukemic cells.