First-line Treatment Of Chronic Myeloid Leukemia Research Articles

Global DNA Methylation analysis of imatinib resistant and sensitive K562 cells

OBJECTIVE: Chronic myeloid leukemia (CML) is a hematological disease which is known by the presence of Philadelphia chromosome (Ph+). BCR-ABL protein is expressed by Ph+ chromosome, represents constant increased tyrosine kinase activity. Imatinib (IMA) is a tyrosine kinase inhibitor (TKI) which is utilized as a first line treatment in CML. Emergence of IMA resistance at some point of therapy leads to treatment failure. DNA methylation is considered to be the most stable epigenetic change and several studies have shown that epigenetic changes may play a role in drug resistance. We investigated the global methylation profile of IMA-sensitive K562S, IMA-resistant K562R and IMA-resistant and adherent K562R (K562R-adh) cells to determine whether epigenetic reprogramming is involved in the resistance to IMA and the change in phenotype due to this resistance. MATERIAL AND METHODS: In this study, morphologically distinct, IMA-sensitive K562S and 5µM IMA-resistant K562R and K562R-adh in-vitro CML cell models were used to analyze the global DNA methylation profile. After DNA was isolated from the cells, global 5mC DNA methylation profiles were investigated by ELISA using equal amounts of DNA. RESULTS: Compared to K562S, the global methylation of K562R showed an increase in DNA methylation profile, but this increase in methylation was not statistically significant. Whereas, a slight hypermethylation was observed in the DNA of the K562R-adh vs K562S and K562R-adh vs K562R which is statistically significant. We observed slight hypermethylation in IMA-resistant cells lines versus to the IMA-sensitive cell line. CONCLUSION: Our observed differences in 5methyl-Cytosine on CpG islands (5mC) in K562S versus K562R and K562R-adh cell lines suggest that the DNA methylation alteration in resistant cells may partly contributed in phenotype switching.

The Impact of Pretransplant Use of Tyrosine Kinase Inhibitors on Allogeneic Stem Cell Transplantation in Patients with Chronic Myeloid Leukemia - A Single-institution Retrospective Study.

Objective Chronic myeloid leukemia (CML) is a malignant hematological disorder, and allogeneic stem cell transplantation (allo-SCT) was its only curative treatment until the introduction of tyrosine kinase inhibitors (TKIs). Allo-SCT is still considered for CML patients who are resistant to TKIs and in an advanced phase. Currently, second- and third-generation (2/3G TKIs are typically incorporated into the first-line treatment of CML. However, the impact of 2/3G TKIs on subsequent allo-SCT remains unclear. We therefore evaluated the effect of 2/3G TKIs on allo-SCT. Methods We retrospectively evaluated the effect of pretransplant therapy with TKIs on the outcome of allo-SCT for CML using clinical data at our institution. Patients Thirty-two CML patients who received their first allo-SCT procedure at our institute from 2001 to 2020 were included. We divided the patients into three subgroups based on TKI treatment before allo-SCT. Patients receiving no TKIs, only imatinib (IM), and 2/3G TKIs were classified into the Non-TKI, IM, and 2/3G TKI groups, respectively. Results In a univariate analysis, the pretransplant use of 2/3G TKIs was significantly associated with a higher 5-year overall survival (91.7%) and relapse-free survival (75.0%) than the use of IM (37.5% and 12.5%) in patients presenting with or progressing to the advanced phase. In addition, pretransplant use of 2/3G TKIs did not increase the incidence of graft-versus-host disease (GVHD). Conclusion We demonstrated that the pretransplant use of 2/3G TKIs was safe and improved the outcome of CML patients who presented with or progressed to the advanced phase without increasing the frequency of GVHD.

Therapeutic Drug Monitoring of Imatinib and N-Desmethyl Imatinib in Chronic Myeloid Leukemia Patients Using LC-MS/MS in a Cohort Study.

Imatinib is an oral tyrosine kinase inhibitor (TKI) and first-line therapy for patients with chronic myeloid leukemia (CML). There is a positive correlation between serum imatinib concentrations and treatment response. However, the specific relationship between the blood concentration of imatinib and its influencing factors remains unclear. This study collected basic information from 102 patients using imatinib as first-line treatment for CML. Further, we analyzed the individual differences in imatinib concentration and explored its influencing factors. Through intra-day and inter-day precision studies, we found that the precision for the imatinib assay methodology was within ±13% and that the recovery rate was above 85%. There is notable individual variation in the blood concentration of imatinib; the recommended treatment concentration is 860-1500ng/mL, with only 41.40% of patients achieving this concentration. Also, there was a negative correlation between age and imatinib trough concentration (Ctrough ), as is observed between age and N-desmethyl imatinib. Moreover, compared with the adolescent group, the serum imatinib Ctrough for groups aged 17-47 and 48-68years was significantly reduced. Further analysis shows that imatinib Ctrough values reaching therapeutic concentrations (59%) increased dramatically for patients with CML aged 17-47years. Moreover, groups dosed with 400mg/day resulted in therapeutic imatinib concentrations for 68% of patients with CML, which was the best performance. The established method was validated, with acceptable accuracy, precision, linearity, and stability, as required, and then successfully applied to the therapeutic drug monitoring of imatinib. Age, dose, and metabolites can influence the imatinib concentration and its therapeutic effect in patients with CML.

COVID-19 Impact on Chronic Myeloid Leukemia Patients.

(1) Background: Chronic myeloid leukemia (CML) is a blood dyscrasia that accounts for about 20% of all leukemia cases. Tyrosine kinase inhibitors (TKIs) are used as first line treatment of CML. The 2019 SARS-CoV-2 outbreak raised new concerns for CML patients, such as whether CML increases the risk of contracting COVID-19, whether TKIs increase that risk, whether these drugs are safe to use during the infection, and whether any other hematologic parameters influence infection outcomes. (2) Methods: In our study we addressed these intriguing questions by using a retrospective analysis of 51 CML patients treated at the Ion Chiricuta Cancer Center, Cluj-Napoca, Romania. Furthermore, we investigated the effects of currently approved COVID-19 vaccines in our CML patients treated with tyrosine kinase inhibitors. (3) Results: Our results have shown that hemoglobin level upon diagnosis of CML has been the only hematologic parameter correlated to the risk of contracting COVID-19 in our CML patients. (4) Conclusions: TKI treatment did not negatively influence COVID-19 risk or the response to the vaccine in our patients. The safety profile of the currently approved COVID-19 vaccines was similar to that of the general population.

Evaluation of the combined effect of naringin and imatinib in philadelphia positive chronic myeloid leukemia

The combined effect of Naringin (NAR) and Imatinib mesylate (IMT) in Philadelphia positive chronic myeloid leukaemia was studied in vitro and in silico in this study. The chronic myeloid leukemia (CML) is a myeloproliferative hematopoietic cancer caused by a chromosomal translocation t (9;22). (q34; q11). IMT, a Tyrosine Kinase inhibitor that targets the BCR-ABL oncoprotein, is a first-line treatment for CML. IMT is related with the development of resistance due to mutation of Abl kinase domain. Natural compounds generated from plants have been linked to enhanced therapeutic efficacy and fewer adverse effects in cancer patients. Flavonoids, for example, are physiologically active substances with anti-cancer capabilities that influence a number of cellular signalling pathways suppressing a variety of malignancies. The primary goal of combining synthetic medications with phytochemicals is to achieve a therapeutic activity with the greatest pharmacological efficacy. Targeting AKT with flavonoid (NAR) compounds in conjunction with IMT treatment could be extremely beneficial in CML through additive processes. The combined effect of IMT and NAR in the treatment of CML was assessed using a silico molecular docking and long-term in vitro cytotoxicity assay on K562 cells.

Impact of Variants in the ATIC and ARID5B Genes on Therapeutic Failure with Imatinib in Patients with Chronic Myeloid Leukemia.

Chronic myeloid leukemia (CML) is a myeloproliferative neoplasm derived from the balanced reciprocal translocation of chromosomes 9 and 22 t (9q34 and 22q11), which leads to the formation of the Philadelphia chromosome and fusion of the BCR-ABL genes. The first-line treatment for CML is imatinib, a tyrosine kinase inhibitor that acts on the BCR-ABL protein. However, even though it is a target-specific drug, about 25% of patients do not respond to this treatment. The resistance mechanisms involved in this process have been investigated and studies have shown that germinal alterations can influence this mechanism. The aim of this work was to investigate 32 polymorphisms in 24 genes of carcinogenic pathway to verify the influence of these genetic variants on the response to treatment with imatinib. Our results demonstrated that individuals with the recessive GG genotype for the rs2372536 variant in the ATIC gene are approximately three times more likely to experience treatment failure with imatinib (p = 0.045, HR = 2.726, 95% CI = 0.9986–7.441), as well as individuals with the TT genotype for the rs10821936 variant in the ARID5B gene, who also have a higher risk for treatment failure with imatinib over time (p = 0.02, HR = 0.4053, IC 95% = 0.1802–0.911). In conclusion, we show that variants in the ATIC and ARIDB5 gene, never screened in previous studies, could potentially influence the therapeutic response to imatinib in patients treated for CML.

Patient characteristics and management practices in chronic myeloid leukemia in Turkey: reflections from an expert meeting

ABSTRACT Introduction The therapeutic landscape of chronic myeloid leukemia (CML) has evolved significantly since the introduction of imatinib. The European LeukemiaNet (ELN) recommendations serve as a guide for diagnosis, treatment, and monitorization of CML, but availability and accessibility of diagnostic tools and medications affect their applicability. Areas covered This article provides an overview of the current clinical management of CML in Turkey with reference to the key outputs of the online expert meeting held in November 2020. The applicability of the ELN 2020 recommendations for treating CML in clinical practice was also discussed. Expert opinion Imatinib is the only reimbursed and the most preferred first-line treatment in CML restricting the upfront use of second-generation tyrosine kinase inhibitors (TKIs), thereby limiting the applicability of treatment-free remission approach in Turkey. The ELN recommendations about using the EUTOS Long-Term Survival (ELTS) score for risk assessment and focusing on patient reported outcomes and quality of life can be enhanced with educational activities. The widespread availability of standardized technical infrastructure for diagnosing and monitoring CML will contribute to better disease management. Establishing a sustainable national database for CML is valuable for observing patient characteristics and disease outcomes as well as the impact of treatment patterns over time.

A narrative review on adverse effects of dasatinib with a focus on pharmacotherapy of dasatinib-induced pulmonary toxicities.

Chronic myeloid leukemia (CML), a myeloproliferative disorder caused by the over activity of BCR-ABL1 (breakpoint cluster region-Abelson), has been successfully treated by Tyrosine kinase inhibitors (TKIs). While imatinib is known as the first-line treatment of CML, in some cases other TKIs including dasatinib, nilotinib, bosutinib, and ponatinib may be preferred. Dasatinib, a second-generation TKI, inhibits multiple family kinases including BCR-ABL, SRC family kinases, receptor kinases, and TEC family kinases. It is effective against most imatinib-resistant cases except T315I mutation. Despite the superiority of dasatinib in its hematologic and cytogenetic responses in CML compared to imatinib, its potentially harmful pulmonary complications including pleural effusion (PE) and pulmonary arterial hypertension (PAH) may limit its use. Appropriate management of these serious adverse reactions is critical in both improving the quality of life and the outcome of the patient. In this narrative review, we will scrutinize the pulmonary complications of dasatinib and focus on the management of these toxicities.

Imatinib Efficacy, Safety and Resistance in Iranian Patients with Chronic Myeloid Leukemia: A Review of Literature.

Background: Imatinib is the gold standard in the treatment of chronic myeloid leukemia (CML) patients. Resistance to imatinib is interfering with patients’ responses and their survivals.Materials and Methods: We designed a systematic search to find relevant studies by applying appropriate keywords in PubMed, Web of science, Scopus, Ovid, ProQuest, Science direct and Google scholar for English studies. We also investigated the aforementioned terms’ correspondence in Magiran, Scientific information database (SID) and Google scholar for Persian articles. Results: 25 studies were selected for final analysis. Reported hematologic responses from adult studies ranged 86-99% and major molecular responses were estimated in 38.84% of our patients within 12 months of treatment. The most frequent reported adverse drug reactions (ADRs) were edema (n=5 studies, 100%) and fatigue and nausea (n=4 studies, 80%); ADR per capita ratio was 1.46. Only one study informed ADRs in pediatrics demonstrating 93% of patients experienced ADRs after receiving imatinib. Most of the Studies (n=4, 67% from 7 studies) considered BCR/ABL point mutation as main reason of imatinib resistance. Drug-binding site and P-loop regions were two common sites for BCR/ABL point mutation.Conclusion: Imatinib as the first line treatment for CML has been associated with proper and durable responses in Iranian adults and children CML patients. Moreover, Imatinib life-threatening adverse effects were reported uncommon. Various responses to modified regimens have been reported in resistant patients; therefore, individualized treatment based on mutation type could be recommended.

Discovery of a highly potent kinase inhibitor capable of overcoming multiple imatinib-resistant ABL mutants for chronic myeloid leukemia (CML)

As the critical driving force for chronic myeloid leukemia (CML), BCR gene fused ABL kinase has been extensively explored as a validated target of drug discovery. Although imatinib has achieved tremendous success as the first-line treatment for CML, the long-term application ultimately leads to resistance, primarily via various acquired mutations occurring in the BCR-ABL kinase. Although dasatinib and nilotinib have been approved as second-line therapies that could overcome some of these mutants, the most prevalent gatekeeper T315I mutant remains unconquered. Here, we report a novel type II kinase inhibitor, CHMFL-48, that potently inhibits the wild-type BCR-ABL (wt) kinase as well as a panel of imatinib-resistant mutants, including T315I, F317L, E255K, Y253F, and M351T. CHMFL-48 displayed great inhibitory activity against ABL wt (IC50: 1 nM, 70-fold better than imatinib) and the ABL T315I mutant (IC50: 0.8 nM, over 10,000-fold better than imatinib) in a biochemical assay and potently blocked the autophosphorylation of BCR-ABL wt and BCR-ABL mutants in a cellular context, which further affected downstream signalling mediators, including signal transducer and activator of transcription 5 (STAT5) and CRK like proto-oncogene (CRKL), and led to the cell cycle progression blockage as well as apoptosis induction. CHMFL-48 also exhibited great anti-leukemic efficacies in vivo in K562 cells and p210-T315I-transformed BaF3 cell-inoculated murine models. This discovery extended the pharmacological diversity of BCR-ABL kinase inhibitors and provided more potential options for anti-CML therapies.

Cardiovascular Toxicities of Tyrosine Kinase Inhibitor in CML

Background: Cardiovascular (CV) toxicity is a known toxicity of tyrosine kinase inhibitors (TKI) used for chronic myeloid leukemia (CML). Imatinib, dasatinib, nilotinib and bosutinib are all approved for first line treatment for CML. We did a retrospective analysis on adverse effects (AE) of TKIs that has been made available to public by the FDA. Methods: The FDA has made the data on AEs of various treatments available to general public through the FDA Adverse Events Reports System (FAERS) public dashboard. We investigated the CV AEs of various TKIs for the years 2017-2019. Results: The percentage of CV AE compared to total AEs reported for Imatinib, Dasatinib, Bosutinib , Nilotinib and Ponatinib were 7.2%, 10.5%, 15.8%, 23.4% and 23.5% respectively. The percentage of CV AE leading to death for Imatinib, Dasatinib, Bosutinib , Nilotinib and Ponatinib were 8.3%, 9.1%, 9.1%, 13.7 % and 18.6% respectively. Conclusions: Out of the reported cases of AEs to TKIs approved for front line CML, nilotinib appears to have more CV AE compared to imatinib, dasatinib and bolutinib. Imatinib appears to have least CV AE out of the total AEs reported Disclosures No relevant conflicts of interest to declare.

Analysis of the cost-effectiveness of treatment strategies for CML with incorporation of treatment discontinuation

AbstractThe cost of tyrosine kinase inhibitors (TKIs) in the treatment of chronic myeloid leukemia (CML) is a substantial economic burden. In Japan, imatinib, dasatinib, and nilotinib are now approved as first-line treatment of CML in chronic phase. Recent “stop TKI” trials have shown that TKIs can be safely discontinued in nearly one-half of patients with sustained deep molecular response (DMR). In this study, we analyzed the cost-effectiveness of a simulated 10 years of CML treatment including stop TKI in both the United States and Japan. We constructed Markov models to compare 4 strategies in which treatment was initiated with imatinib, dasatinib, nilotinib, or any of these TKIs at the physician's discretion. Treatment was switched to another TKI in the case of intolerance or resistance to the initial TKI, and TKIs were discontinued if DMR persisted for 2 years. “Imatinib first” offered 7.34 quality-adjusted life years (QALYs) at the cost of $1 022 148 in the United States (US dollars) and ¥32 526 785 in Japan (Japanese yen). In comparison with imatinib first, the incremental cost-effectiveness ratio per QALY of “dasatinib first” (7.68 QALY, $1 236 052, ¥51 506 254), “nilotinib first” (7.64 QALY, $1 245 667, ¥39 635 598), and “physician's choice” (7.55 QALY, $1 167 818, ¥41 187 740) was $641 324, $696 717, and $666 634 in the United States and ¥54 456 325, ¥23 154 465, and ¥39 635 615 in Japan, respectively. None of the 3 strategies met the willingness-to-pay threshold. The results were robust to univariate and multivariate sensitivity analyses. Imatinib first was shown to be the most cost-effective approach even with the incorporation of stop TKI.

MiR-96 acts as a tumor suppressor via targeting the BCR-ABL1 oncogene in chronic myeloid leukemia blastic transformation

MicroRNA-mediated posttranscriptional regulation is an important epigenetic regulatory mechanism of gene expression, and its dysregulation is involved in the development and progression of a variety of malignancies, including chronic myeloid leukemia (CML). The BCR-ABL1 fusion gene is not only the initiating factor of CML, but it is also an important driving factor for blastic transformation. Tyrosine kinase inhibitors (TKIs) targeting BCR-ABL1 tyrosine kinase activity, represented by imatinib, are currently the first-line treatment for CML. However, due to primary resistance or secondary resistance caused by mutations in the BCR-ABL1 kinase domain, TKIs cannot completely prevent the progression of CML; thus, the study of BCR-ABL1 gene expression regulation is of great significance. In this study, bioinformatics analysis and our results showed that miR-96 could directly bind to the 3'UTR region of BCR-ABL1 to regulate fusion protein expression, thereby regulating its downstream signaling pathway activity. We also found that miR-96 was downregulated during the progression from the chronic phase (CML-CP) to the blast crisis (CML-BC). Downregulation of miR-96 could promote the proliferation and participate in the cell differentiation of CML-BC cells. Additionally, we found that the novel histone deacetylase drug chidamide and the DNA methyltransferase inhibitor decitabine could restore the low expression of miR-96 in CML cells, and there were two abnormal hypermethylated sites in the promoter region of miR-96 in CML, suggesting that its low expression might be at least partially regulated by epigenetic mechanisms. In addition, re-expression of miR-96 could increase the sensitivity of CML-BC cells to imatinib. Thus, miR-96 functions as a tumor suppressor, and re-expression of this microRNA might have therapeutic benefits in CML blastic transformation.

Mechanisms of resistance to tyrosine kinase inhibitors in chronic myeloid leukemia

In recent years, treatment of chronic myeloid leukemia(CML)keeps making progresses, which includes chemotherapy, splenectomy, interferon, hematopoietic stem cell transplantation (HSCT)and several other methods. The first generation of tyrosine kinase inhibitors (TKI) imatinib, which improved the overall survival (OS) and event free survival (EFS)rates of patients, has become the first-line treatment of CML. However, primary or secondary resistance to TKI has become the main cause of treatment failure in some CML patients. Exploring the mechanisms of drug resistance and searching for new strategies to deal with drug resistance have become a hot research topic in CML. The mechanisms of TKI resistance are complex, which relate to a variety of gene products and intracellular signaling molecules, and mainly divide into breakpoint cluster region/Abelson leukemia virus (BCR/ABL) dependent pathways and non-BCR/ABL dependent pathways.Some studies have found that these resistance mechanisms can exist alone or simultaneously in the same CML patient. With researches on the mechanisms of TKI resistance in CML patients have made great progress, the authors intend to make a brief overview of the research progress. Key words: Leukemia, myelogenous, chronic, BCR-ABL positive; Drug resistance, neoplasm; Tyrosine kinase inhibitor

Time-series analysis in imatinib-resistant chronic myeloid leukemia K562-cells under different drug treatments.

SummaryChronic myeloid leukemia (CML) is characterized by the accumulation of active BCR-ABL protein. Imatinib is the first-line treatment of CML; however, many patients are resistant to this drug. In this study, we aimed to compare the differences in expression patterns and functions of time-series genes in imatinib-resistant CML cells under different drug treatments. GSE24946 was downloaded from the GEO database, which included 17 samples of K562-r cells with (n=12) or without drug administration (n=5). Three drug treatment groups were considered for this study: arsenic trioxide (ATO), AMN107, and ATO+AMN107. Each group had one sample at each time point (3, 12, 24, and 48 h). Time-series genes with a ratio of standard deviation/average (coefficient of variation) >0.15 were screened, and their expression patterns were revealed based on Short Time-series Expression Miner (STEM). Then, the functional enrichment analysis of time-series genes in each group was performed using DAVID, and the genes enriched in the top ten functional categories were extracted to detect their expression patterns. Different time-series genes were identified in the three groups, and most of them were enriched in the ribosome and oxidative phosphorylation pathways. Time-series genes in the three treatment groups had different expression patterns and functions. Time-series genes in the ATO group (e.g. CCNA2 and DAB2) were significantly associated with cell adhesion, those in the AMN107 group were related to cellular carbohydrate metabolic process, while those in the ATO+AMN107 group (e.g. AP2M1) were significantly related to cell proliferation and antigen processing. In imatinib-resistant CML cells, ATO could influence genes related to cell adhesion, AMN107 might affect genes involved in cellular carbohydrate metabolism, and the combination therapy might regulate genes involved in cell proliferation.

Predictive parameters for imatinib failure in patients with chronic myeloid leukemia

ABSTRACTObjective: Until recently, imatinib was the standard first-line treatment in chronic myeloid leukemia (CML). The inclusion of nilotinib and dasatinib as first-line options in CML raised a debate on treatment selection. The aim of our study was to analyze predictive parameters for imatinib response as the first-line treatment of CML patients.Methods: The study included 168 consecutive patients with chronic phase Philadelphia-positive CML who were diagnosed and treated with Imatinib 400 mg once daily at a single university hospital. Numerous parameters were analyzed in terms of imatinib response including comorbidities as well as occurrence of second malignancies.Results: After the median follow-up of 87 months in 61 patients (36.3%), the imatinib failure was verified. Cox regression analysis identified hepatomegaly (p = 0.001), leukocytosis ≥ 100 × 109/l (p = 0.001), blood blasts ≥ 1% (p = 0.002), and the presence of additional cytogenetic aberrations (p = 0.002) as predictors of Imatinib failure. Based on these findings, a new prognostic model was developed according to which imatinib failure had 17% (8/47) of patients in low risk, 34.9% (30/86) of patients in intermediate risk, and 76.7% (23/30) of patients in high-risk group (HR = 3.973, 95% CI for HR 2.237–7.053, p < 0.001).Conclusion: The new score allows better selection of patients who are suitable for treatment with imatinib and may guideline the clinical decision for front-line treatment of CML.

4-methylumbelliferone and imatinib combination enhances senescence induction in chronic myeloid leukemia cell lines.

Chronic myeloid leukemia (CML) is a myeloproliferative syndrome characterized by the presence of the Philadelphia chromosome which encodes a constitutively activated tyrosine kinase (BCR-ABL). The first line treatment for CML consists on BCR-ABL inhibitors such as Imatinib. Nevertheless, such treatment may lead to the selection of resistant cells. Therefore, it is of great value to find molecules that enhance the anti-proliferative effect of first-line drugs. Hyaluronan is the main glycosaminglican of the extracellular matrix which is involved in tumor progression and multidrug resistance. We have previously demonstrated that the inhibition of hyaluronan synthesis by 4-methylumbelliferone (4MU) induces senescence and can revert Vincristine resistance in CML cell lines. However, the effect of 4MU on Imatinib therapy remains unknown. The aim of this work was to determine whether the combination of 4MU with Imatinib is able to modulate the proliferation as well as apoptosis and senescence induction in human CML cell lines. For this purpose the ATCC cell line K562, and its multidrug resistant derivate, Kv562 were used. Cells were exposed to 4MU, Imatinib or a combination of both. We demonstrated that 4MU and Imatinib co-treatment abrogated the proliferation of both cell lines. However, such co-treatment did not increase the levels of apoptosis when compared with the treatment with Imatinib alone. For both cell lines the mechanisms of tumor suppression involved was senescence, since the combination of 4MU and Imatinib arrested the cell cycle and increased senescence associated β-galactosidase activity and senescence associated heterochromatin foci presence when compared to each drug alone. Moreover, 4MU, Imatinib and 4MU+Imatinib decreased pAkt/Akt ratio in both cell lines and reduced the pERK/ERK ratio only in K562 cells. These findings highlight the potential use of 4MU together with Imatinib for CML therapy.

Pathogenesis and treatment of chronic myeloid leukemia: current status

Chronic myeloid leukemia (CML) is a malignant clonal proliferative disease, which originates from multifunctional hematopoietic stem cells of bone marrow. Imatinib is used as the first-line treatment for CML currently, owing to its obvious curative effect for patients in chronic phase and survival time prolonged significantly for patients in accelerated phase and blast crisis. With the long-term application of imatinib in clinic, the drug resistance and intolerance gradually appear, resulting in decreased long-term effects of CML. This paper will review the current status of the pathogenesis and treatment of CML. Key words: Leukemia, myelogenous, chronic; Tyrosine kinase inhibitors; bcr-abl

MicroRNA-1301-Mediated RanGAP1 Downregulation Induces BCR-ABL Nuclear Entrapment to Enhance Imatinib Efficacy in Chronic Myeloid Leukemia Cells.

Chronic myeloid leukemia (CML) is a myeloproliferative disease. Imatinib (IM), the first line treatment for CML, is excessively expensive and induces various side effects in CML patients. Therefore, it is essential to investigate a new strategy for improving CML therapy. Our immunoblot data revealed that RanGTPase activating protein 1 (RanGAP1) protein levels increased by approximately 30-fold in K562 cells compared with those in normal cells. RanGAP1 is one of the important components of RanGTPase system, which regulates the export of nuclear protein. However, whether RanGAP1 level variation influences BCR-ABL nuclear export is still unknown. In this report, using shRNA to downregulate RanGAP1 expression level augmented K562 cell apoptosis by approximately 40% after treatment with 250 nM IM. Immunofluorescence assay also indicated that three-fold of nuclear BCR-ABL was detected. These data suggest that BCR-ABL nuclear entrapment induced by RanGAP1 downregulation can be used to improve IM efficacy. Moreover, our qRT-PCR data indicated a trend of inverse correlation between the RanGAP1 and microRNA (miR)-1301 levels in CML patients. MiR-1301, targeting the RanGAP1 3′ untranslated region, decreased by approximately 100-fold in K562 cells compared with that in normal cells. RanGAP1 downregulation by miR-1301 transfection impairs BCR-ABL nuclear export to increase approximately 60% of cell death after treatment of 250 nM IM. This result was almost the same as treatment with 1000 nM IM alone. Furthermore, immunofluorescence assay demonstrated that Tyr-99 of nuclear P73 was phosphorylated accompanied with nuclear entrapment of BCR-ABL after transfection with RanGAP1 shRNA or miR-1301 in IM-treated K562 cells. Altogether, we demonstrated that RanGAP1 downregulation can mediate BCR-ABL nuclear entrapment to activate P73-dependent apoptosis pathway which is a novel strategy for improving current IM treatment for CML.

Molecular Detection of BCR-ABL in Chronic Myeloid Leukemia.

All chronic myeloid leukemia (CML) patients have the BCR-ABL fusion gene. The constitutively activated BCR-ABL tyrosine kinase is a critical pathogenetic event in CML. Tyrosine kinase inhibitors (TKIs), such as imatinib, are synthesized small molecules that primarily target BCR-ABL tyrosine kinases and have become a first-line treatment for CML. Detection of BCR-ABL transcript level by real-time quantitative polymerase chain reaction (RQ-PCR) is a clinical routine for evaluating TKI treatment efficacy and predicting long-term response. Furthermore, because they are a main TKI resistance mechanism, the BCR-ABL tyrosine kinase domain (TKD) point mutations that are detected by Sanger sequencing can help clinicians make decisions on subsequent treatment selections. Here, we present protocols for the two abovementioned molecular methods for CML analysis.