Abstract
The tyrosine kinase inhibitors (TKIs) have improved overall survival of CML (chronic myeloid leukemia) patients and allow them to experience normal life expectancy. However, relapse and drug resistance remain the main challenges in the clinical treatment of CML. The B-cell lymphoma 6 (BCL6) is essential to regulation of multiple function such as immune response and lymphomagenesis in lymph node germinal cells. Recent studies have shown that BCL6 is required for the maintenance of leukemia stem cells in CML, but the expression of Bcl-6 in response to Imatinib and the underlying mechanism are still unclear. Here, we found that BCL6 is expressed at high levels in primary CML bone marrow samples and CML TKI-resistance cell lines. CML cells with higher levels of BCL6 were generally sensitive to treatment with BCL6 inhibitors, BI-3812. Treatment of CML cells with BCL6 inhibitor and TKIs suggested enhanced anti-leukemia activity. In summary, our findings suggest BCL6 as a therapeutic target for the treatment of CML.
Keywords: Chronic myeloid leukemia, Resistance, Imatinib, BI-3812, Bcl6 inhibitor
1. Introduction
Chronic myeloid leukemia (CML) is anunique myeloproliferative neoplasm characterized by a Philadelphia chromosome (Ph), which resulting from a t(9:22)(q34; q11) chromosomal translocation. The translocationcauses the BCR::ABLfusion gene, resulting in the expression of the oncogenic tyrosine kinase BCR-ABL1 [1,2]. BCR-ABL1 is a non-receptor tyrosine kinase that abnormally activate various downstream signaling pathways, reprogramming normal hematopoietic cells, causing uncontrolled proliferation and survival of tumor cells, inhibiting transformed cell apoptosis, and playing a significant role in the pathogenesis of CML [3].
Treatment with Tyrosine kinase inhibitors (TKIs) induces persistent deep molecular responses by targeting the tyrosine kinase activity region of BCR-ABL1 and finally reduces BCR-ABL1 transcription levels in CML patients. TKIs significantly altered the natural course of the disease and improved the survival rate of CML patients from to 80%–90 % [4]. However, more than 20 % of patients will unfortunately acquire resistance or intolerance to first-line TKI therapy. Thus, there is a pressing need to explore novel treatment modalities to improve the persistence of response and avoid the development of TKI resistance.
B-cell lymphoma 6 (BCL6), which is a transrepression factor and is a member of the BTB/POZ family. BCL6 drives the malignant phenotype by regulating hundreds of target genes involved in proliferation and DNA damage such as TP53, ARF [[5], [6], [7]]. Recent studies also unveiled the critical functions of BCL6 in the pathogenesis and/or therapeutic response of diffuse large B-cell lymphoma and other lymphomas. In addition to hematopoietic cancer cells, the role of BCL6 in solid tumors such as non-small cell lung cancer, breast cancer, and gastric cancer is gradually being discovered [[8], [9], [10]]. More importantly, BCL6 upregulation is involved in the survival and self-renewal of Ph-positive acute lymphoblastic leukemia and CML stem cells during TKI treatment [11,12]. However, the biological function of BCL6 in BCR-ABL resistance remains unclear.
BI-3812 is a novel and efficient BCL6 inhibitor that binds to the BTB domain of BCL6 and causes derepression of BCL6-bound genes and has anti-proliferative effects, making it a potentially better BCL6 inhibitor. Thus, we investigated pharmacologic inhibition of Bcl-6 using BI-3812 in CML. Our data revealed that the expression of BCL6 was significantly increased in resistant CML patients and TKIs-resistant cell lines. Up-regulation of BCL6 in response to TKI treatment represents a novel defense mechanism, which enables leukemia cells to survive TKI treatment. BI-3812 can inhibit cell proliferation, and promote apoptosis by targeting the BCL6-Arf signaling axis.
2. Methods
2.1. Reagents and antibodies
BI-3812(purity >99 %) and Imatinib (IM) were purchased from MCE (USA, HY-111381 and HY-15463). DMSO was purchased from Solarbio (Shanghai, China, D8371). BI-3812 and IM were dissolved in DMSO, respectively. The antibodies were used in this paper as followed: Anti-BCL2 (A19693), anti-Mcl-1 (A0250), anti-BCL6 (A7173), anti-c-ABL(A0282), anti-p-Abl (AP1060), anti-TP53 (A0263), anti-p-P38 (AP0526), anti-CD56 (A7913) and anti-ARF1 (A9195) were all purchased from ABclonal (Wuhan, China). Anti-P38 (WL00764) was purchased from Wanleibio (Shenyang, China). Anti-tubulin antibody was provided by proteintech(Japan).
2.2. Cell lines and culture
The human chronic myeloid cell lines K562(Cell Bank of Shanghai Institute of Cell Biology, Chinese Academy of Sciences) were maintained with RPMI-1640 medium(Gibco, USA) with 10 % fetal bovine serum(Gibco), and 1 % penicillin/streptomycin. The K562R cell line was generated from K562 by treating cells with gradually increasing concentrations of TKIs. All cells were maintained in incubators at 37 °C in a moist environment of 5 % CO2. The cells were extended in a liquid medium for 1–3 weeks and were routinely checked for mycoplasma contamination using the mycoplasma (Biyuntian, China) detection kit before proceeding to the experiment.
2.3. Clinical samples
Information on bone marrow specimens from 57 CML clinical patients with complete medical records from 2020 to 2023 at the Second Affiliated Hospital of Chongqing Medical University and 13 healthy human bone marrow samples as controls were collected. Intracellular Flow Cytometry was performed to detect the expression level of BCL6.
2.4. Flow cytometry
Cells were harvested as described above. Experiments that included primary CML tumor cells were stained with APC-Bcl6 (Clone, K112-91), PE-Cy7-CD34 (Clone, 581), FITC-CD15 (Clone, MMA), and APC-H7-CD45 (Clone, 2D1) antibodies. All of mentioned flow cytometry antibodies were purchased from BD Biosciences. CML samples and CML cell lines were analyzed for each condition on a Beckman flow cytometer.
2.5. Cell viability assay
Log phase K562 cells and K562R were collected, the cell suspension concentration (5000 cells/well) was adjusted and inoculated in 96-well culture plates at increasing concentrations of BI-3812, then 10 μL CCK-8 solution was added at selected time points (0–72 h) and the absorbance at 450 nm was measured using a multifunctional enzyme marker (Thermo Scientific, USA).
2.6. Western blotting
Pre-experimental results show that the lethal effect of imatinib on K562 cells was stronger than that of drug-resistant K562 cells, therefore, we treated K562 and K562 drug-resistant cells with imatinib and obtained enough proteins for Western blot at different periods (0–48 h). In addition, preliminary tests also showed that the lethal effect of BI-3812 on K562 drug-resistant strains was stronger than that on K562 cells. Therefore, we treated K562 and K562 drug-resistant cells with different concentrations of BI-3812 to obtain enough protein for western blotting. And then incubated with the corresponding primary antibody overnight, including Anti-BCL2, anti-BCL6, anti-P-Bcr-Abl, anti-TP53 were all purchased from ABclonal (Wuhan, China), anti-P38, anti-p-P38, anti-CD56 were purchased from Wanleibio (Shenyang, China). Anti-tubulin antibody was provided by proteintech(Japan). The diluent primary antibody and antibody were diluted at a ratio of 1:1000 and incubated with the corresponding target protein at 4°, and then incubated with the second antibody and identified by ECL reagent.
2.7. Clone formation assay
Collected concentrations of 10 μL/μM BI-3812 treated 72 h of K562 and K562R, 500 cells were taken from each group and placed in six-well plates. Replenish the medium to 2 ml, mark it back into the thermostat to continue cultivation, 8 days later with a fluorescent microscope to count and photograph the cell colony.
2.8. Cell apoptosis assay
An Annexin V-FITC Apoptosis Detection Kit (Beyotime, Shanghai) was used to detect the percentage of apoptotic cells. K562 and K562 resistant cells (1 × 10^6 cells) were treated with different doses of imatinib and/or BI-3812 for 24 h and 48 h, and then stained with Annexin-V/PI. Apoptosis was then detected by flow cytometry (Beckman Coulter, USA).
2.9. Statistical analysis
All data including results of all cell lines are presented as mean ± standard error. The CML patients’ sample data were demonstrated equivocal variance. All in vitro results generated from cell line including Western Blotting and Flow cytomertry data are representative of at least 3 independent experiments. The statistical significance was assigned when P values were<0.05(*).
3. Results
3.1. BCL6 is highly expressed in CML patients bone marrow cells
In CML, BCL6 is necessary for maintaining the leukemia stem cells, but its expression levels in CML patients' bone marrow cells are unclear. We evaluated the expression level of BCL6 and its relationship with the clinical prognosis of CML patients. Our flow cytometry results showed that BCL6 is highly expressed in bone marrow cells of CML-resistant patients compared to untreated chronic phase (CP) CML patients(71.34 %–7.49 %) (Fig. 1.1A–C). We also found that BCL6 expression is significantly increased in bone marrow CD34+ cells of CML-resistant patients compared to healthy individuals and CML-CP patients (98.52 %–1.49 %) (Fig. 1.1E–G). According to the follow-up outcome after TKI treatment for 12 months, 57 CML patients were assigned to IM resistant (kinase-independent) group (n = 21) and the non-resistant group (n = 36). We found that CML patients with IM-induced TKIs resistance had increased Bcl6 expression in bone marrow cells compared with healthy donors and CP-CML. There was also no significant difference between CP-CML patients and healthy donors (1D and 1H). These results indicate that BCL6 is highly expressed in CML patient specimens and is associated with CML resistance.
Fig. 1.
The gate was set based on the surface markers of granulocytes and stem cells, and the expression levels of Bcl6 were compared between healthy individuals and patients with initial diagnosis of chronic phase (A-C and E-G). Collected prognosis information from 48 clinical CML patients for statistical analysis of the relationship between Bcl6 expression and prognosis (D, H).
3.2. BCL6 is upregulated in CML cells in response to TKI treatment
To clarify the function of BCL6 on CML cells, we detected BCL6 expression through flowcytometry and found that K562R cells exhibited a higher level of BCL6 expression compared to CML K562 cells (as shown in Fig. 2A and B). To confirm the relationship between BCR-ABL1 tyrosine kinase and BCL6, K562and K562R cells were treated with the tyrosine kinase inhibitor Imatinib (IM). As shown in Figures C, and D, after treatment with IM (5 μM), BCL6 and BCL2 were both expressed at higher levels in K562R cells. Our Western blot results also showed that after treatment with IM (2.5 μM), the expression of BCL6 in K562R cells was higher compared to the K562 group. These results indicate that BCL6 may exert a vital role in the TKI-resistance of CML. The inhibitory effect of IM on the proliferation of resistant K562R cells is weaker, and the expression of BCL6 and BCL2 is not directly regulated by the BCR-ABL1 tyrosine kinase.
Fig. 2.
Flow cytometry was used to detect the expression levels of BCL6 in CML cell lines (A, B). After a 48-h treatment with imatinib, the expression levels of BCL6 and BCL2 were examined in both sensitive and resistant CML cell lines (C, D). Western blot analysis was performed to assess the expression levels of BCL6 in CML cells at different time points following treatment with IM (E, F). The full, non-adjusted images as Supplementary Fig. S2.
3.3. Arf was activated in K562-resistance cells in response to IM
CD56 and P38 are potential upstream signaling factors for Bcl6 [13,14]. We treated K562 and K562R cells with different concentrations of IM (0 μM, 1 μM, 2.5 μM, 5 μM, and 8 μM) for 48 h and found that IM significantly downregulated p-Bcl-Abl, Bcl-Abl, and Bcl2 in both K562 and K562R cells. However, treatment with Imatinib resulted in strong up-regulation of BCL6 protein expression as concentrations increased (as shown in Fig. 3 A, B, C). Under the same treatment conditions, the pro-apoptotic protein TP53 was significantly downregulated in K562 cells but significantly upregulated in K562R cells (as shown in Fig. 3 F). The anti-apoptotic protein Mcl-1 was upregulated in K562R cells (as shown in Fig. 3 D). Compared with the control group, the expression of the pro-apoptotic protein Arf did not change significantly in K562 cells (as shown in Fig. 3 E) but was significantly reduced in K562R cells. These results suggest that the Bcl6-Arf signaling pathway may be an unique resistance mechanism in CML.
Fig. 3.
After treating CML cells with different concentrations of imatinib, the protein expression levels of molecules related to the BCL6-Arf signaling pathway were examined using Western blot analysis (A–F). The full, non-adjusted images as Supplementary Fig. S3.
3.4. BI-3812 exerts potent inhibitory effects on IM-resistant CML cells
We investigated the effect of BI-3812 on the proliferation of K562 and K562R cells. Our results showed that BI-3812 had a time- and dose-dependent inhibitory effect on CML cell viability. When treated with different concentrations of BI-3812 for 24 h, 48 h, and 72 h, the proliferation rate of K562 cells steadily increased with time, but there was no significant difference compared to the control group. However, the proliferation of K562R cells showed significant differences under the same conditions, with higher concentrations of BI-3812 resulting in weaker cell proliferation, and the untreated group showing the strongest proliferation capacity (as shown in Fig. 4A and B). BI-3812 could induce Bcl6 degradation, so we verified its effect on the protein expression levels of Bcl6. After treating with different concentrations of BI-3812 for 48 h, the expression levels of Bcl6 in K562 and K562R cells were decreased (as shown in Fig. 4C). At the same time, after treating the cells with BI-3812 for different periods (24 h, 48 h, 72 h), the expression of Bcl6 was significantly downregulated (as shown in Fig. 4D). In addition, we found that BI-3812 had a more significant effect on the degradation of Bcl6 in K562R cells. The clone formation experiment also showed that BI-3812 had a significant inhibitory effect on the number of cell colonies formed by CML cell lines, and the inhibitory effect of the same dose of BI-3812 on the formation of cell colonies by K562R cells was stronger than that on K562 cells after 72 h of treatment (as shown in Fig. 4E). The column chart showed that BI-3812 had an inhibitory effect on the proliferation of CML cells, and the inhibitory effect on K562R was stronger (as shown in Fig. 4F). To investigate the effect of BI-3812 on the apoptosis of CML cell lines, we analyzed the apoptosis index of K562 and K562R cells treated with BI-3812 for 24 h and 48 h and found that the degree of apoptosis in K562 cells did not change significantly with the same dose of BI-3812(4G-H), however, BI-3812 has a strong pro-apoptotic effect on K562R.
Fig. 4.
After treating CML cells with different concentrations of BI-3812 at various time points, the cell proliferation status was assessed (A, B). Additionally, the protein expression levels of BCL6 were examined (C, D). The results of the colony formation assay after treating cells with BI-3812 for 72 h were obtained (E, F). The changes in cell apoptosis were evaluated at different time points following treatment with BI-3812 (G, H). The full, non-adjusted images as Supplementary Fig. S4.
3.5. BI-3812 promotes apoptosis in CML cells through the Bcl6-Arf pathway
To explore the potential mechanism by which BI-3812 promotes apoptosis and inhibits malignant proliferation of CML-resistant cells, we used Western blotting to detect the effect of BI-3812 on CML cells. The experimental results showed that after treating with BI-3812 for 24 h, 48 h, and 72 h, the expression levels of Mcl-1, phospho-Bcr-Abl1, and TP53 in K562 and K562R cells decreased in a time-dependent manner (as shown in Fig. 5C and D), while the expression of Arf and phospho-p-p38-MAPK increased significantly (as shown in Fig. 5A), and the increase in Arf expression was more pronounced in K562R cells (as shown in Fig. 5B). Next, we further verified the protein expression levels of Arf and its related pathways in CML cells treated with different concentrations of BI-3812. Western blotting showed that TP53 generally increased, and the trend was more pronounced in K562 cells. The expression of Bcl2 and Mcl-1 decreased, indicating that they are regulated independently of Bcr-Abl1. The expression of our target protein, Arf, showed no significant change in K562 cells but showed a significant increase in K562R cells, which also illustrates that the pro-apoptotic protein Arf has a stronger effect in the higher Bcl6-expressing K562R cells. The results showed that BI-3812 could target and induce the degradation of Bcl6, inhibit the proliferation of CML-resistant cells, and promote apoptosis.
Fig. 5.
After treating CML cells with 10 μM of BI-3812 for various periods, the protein expression levels of molecules related to the BCL6-Arf signaling pathway were examined (A–D). Additionally, the changes in the expression of these molecules were assessed after treating the cells with different concentrations of BI-3812 (E).The full, non-adjusted images as Supplementary Fig. S5.
3.6. BI-3812 combination with Imatinib induces apoptosis of CML cells
To investigate whether BI3812 has a synergistic effect with IM in promoting apoptosis and inhibiting proliferation of CML cells, we treated K562 and K562R cells with 1.5 μM IM, 10 μM BI-3812, or the combination of both. And CCK-8 assays were performed at 0 h, 24 h, and 48 h. The results showed that in K562 cells, the inhibitory effect of IM alone was not significantly different from that of BI-3812 alone or the combined treatment group (as shown in Fig. 6A), while in K562R cells, the combined treatment group showed a significantly stronger inhibitory effect on cell growth than IM or BI-3812 alone (as shown in Fig. 6B). This indicates that these two drugs have a synergistic effect in inhibiting the growth of resistant cells.To investigate the effect of the synergistic action of BI-3812 and IM on the apoptosis of CML cell lines, we treated K562 and K562R cells with BI-3812 alone or in combination with IM and analyzed the apoptosis index of each group of cells after 24 h and 48 h of treatment compared to the control group. Upon treating cells with the same dosage of BI-3812, no significant change in apoptosis level was observed in K562 cells. The apoptosis rate at 24 h was 7.29 %, which decreased to 5.3 % at 48 h. However, in the combination treatment group, a significant increase in apoptosis level was observed after 48 h, with the apoptosis rate escalating from 9.07 % at 24 h to 39.3 % at 48 h (Fig. 6C–G). Furthermore, in the K562R group, the addition of the BI-3812 inhibitor significantly increased the apoptosis level after 48 h, with the apoptosis index rising from 8.56 % to 30.34 %. The combination treatment group showed no change in apoptosis after 24 h of treatment, but a significant increase in cell apoptosis was observed at 48 h, with the rate rising from 8.76 % to 47.23 % (Fig. 6H–L). Statistical analysis was conducted to assess the effects of BI-3812, IM, and their combination on the apoptosis rates of K562 and K562R cells. There was a statistically significant difference in the apoptosis percentages of CML cells after 48 h of drug treatment. However, no significant change was observed in cell apoptosis at 24 h (Fig. 6 M). The K562R cells treated with BI-3812 alone exhibited a significant increase in late-stage apoptosis compared to K562 cells, and the late-stage apoptosis rate was higher than early-stage apoptosis. In the combination treatment group, the late-stage apoptosis percentage in K562R cells was significantly higher than early-stage apoptosis, while in K562 cells, the early-stage apoptosis rate was higher than late-stage apoptosis, and both observations were statistically significant (Fig. 6 N). These results indicate that BI-3812 enhances the induction of CML cell apoptosis by IM. The above results indicate that BI-3812 and imatinib have a synergistic effect in inhibiting tumor cell growth and inducing apoptosis. The combination of imatinib and BI-3812 is a novel and potential treatment combinations for addressing TKI resistance in CML therapy.
Fig. 6.
Different concentrations of BI-3812 were applied to the cells, and cell proliferation in K562 (A) and K562R (B) cell lines was measured using the CCK-8 assay. The changes in apoptosis status were evaluated after treating the cells with different concentrations of BI-3812 in both K562 and K562R cell lines (C–L). Statistical analysis was performed to assess the apoptosis status of CML cells after treatment with BI-3812, IM, or their combination, either individually or in combination (M − N).
4. Discussion
Chronic myeloid leukemia is a bone marrow proliferative hematologic malignancy. Although the advent of small molecule inhibitors targeting the BCR-ABL1 fusion gene tyrosine kinase has made significant progress in the treatment of CML, widespread clinical use of TKI has led to insensitivity of hematopoietic stem cells to tyrosine kinase inhibitors, failing to eradicate the disease, and relapse and resistance remain major challenges in CML clinical treatment [15].
BCL6, a key oncogene regulated by several pathways, can inhibit the transcription of 41,200 potential target genes [16]. The proto-oncogene BCL6 belongs to the anti-apoptotic family and can promote tumor development in CML leukemia stem cells by inhibiting the functions of Arf and TP53, thereby inhibiting cell apoptosis. Therefore, targeting the BCL6 function may be a possible approach to treat CML and overcome IM resistance. Meanwhile, a study has shown that BCL6 inhibitors can induce LICs (Leukemia-initiating cells) apoptosis and effectively prevent the development of leukemia induced by allograft transplantation of CML cells [17]. Therefore, using BCL6 inhibitors is a promise strategy to eradicate CML LICs and may reduce the risk of malignancy transformation [17]. Interrupting the interaction between inhibitors and transcriptional repressors can also interfere with BCL6 oncogenic activity [18]. BCL6 upregulation in TKI therapy reflects a new defense mechanism that allows leukemia cells to survive TKI therapy. We propose that the combination of TKI therapy and a novel Bcl6 inhibitor can significantly inhibit the proliferation of BCR-ABL1 CML cells.
In this study, we found BI-3812 is a potential solution to the CML treatment problem, which has not been explored in the treatment of CML. BI-3812, as a novel and efficient BCL6 inhibitor, can inhibit the BTB domain of BCL6 and degrade BCL6 by ubiquitination and proteasome-dependent degradation. This inhibitor reduces BCL6 transcriptional inhibition by interfering with the binding of the BCL6 to the co-inhibitor [19]. Previous studies have revealed the relationship between Bcl6 inhibitors and various hematological malignancies or solid tumors, such as diffuse large B-cell lymphoma and breast cancer, but the role and mechanism of BCL6 in CML resistance are currently unknown. Therefore, this study preliminarily explored the effects and mechanisms of BCL6 and its novel inhibitor BI-3812 on CML resistance. We have demonstrated that BI-3812 is a safe BCL6 inhibitor with BCR-ABL-specific inhibitory effects.
We found that the expression of BCL6 was higher in IM-resistant patients or cell lines than in newly diagnosed patients or sensitive cell lines, indicating that BCL6 is highly correlated with IM resistance in CML. Furthermore, BI-3812 and imatinib have synergistic effects in inhibiting growth and inducing apoptosis. Notably, BI-3812 has a stronger anti-tumor effect on K562R cells than on K562 cells. The experiment verified the proliferation inhibition effect of BI-3812 on K562 cells sensitive to IM and K562R cells resistant to IM, demonstrating that BI-3812 has a strong inhibitory ability against K562R. We also preliminarily validated that the BCL6-Arf signaling pathway may play an important role in CML resistance. Therefore, when IM is used in combination with BI-3812, their synergistic effects are more effective on K562R. This suggests that combining BI-3812 with imatinib may be a new strategy to overcome TKI resistance in chronic myeloid leukemia. However, the exact mechanism of BI-3812 on K562R still needs to be further elucidated, and more detailed evidence is needed to substantiate our speculation. Some studies showed that HSF1 may be involved in Bcl6-induced chemo-resistance. HSF1 is a major regulator of stress response, and it controls the expression of many stress proteins. Increased HSF1 expression has been found in several tumor types, and HSF1 depletion leads to decreased cell viability, as well as greater sensitivity to chemical agents. The above discovery has led researchers to speculate that the tolerance of solid tumors to chemo-radiotherapy may be achieved by HSF1 stress conditions and then regulating the high expression of BCL6. In the solid tumour patient with poor prognosis for clinical treatment, the high expression of BCL6 was accompanied by the high expression of HSF1. And they also confirmed that HSF1 and BCL6 interact directly, and it is indeed HSF1 that drives BCL6 expression. The researchers also found that one of the reasons that cancer cells with high expression of HSF1 and BCL6 are not insensitive to DNA damage caused by chemo-therapy is related to the fact that high expression of BCL6 inhibits the activity of TOX. This inhibition will promote cancer cells to adapt the repair of DNA damage caused by chemo-therapy [[20], [21], [22], [23]].
Overall, our study has demonstrated that BI-3812 can effectively inhibit both imatinib-sensitive and resistant CML cells at the cellular level, and enhance the sensitivity of these cells to imatinib. Our study suggests that targeting cancer proteins through auxiliary proteins is a promising therapeutic approach, providing a promising treatment target for BI-3812 in the treatment of IM-resistant patients.
5. Conclusions
Our study has revealed for the first time the mechanism of action of the BCL6 inhibitor BI-3812 in CML. Both cells and cell lines from CML patients showed overexpression of BCL6. Inhibiting the expression of BCL6 with BI-3812 can suppress the malignant proliferation ability of K562 and K562R cells. It has been demonstrated that BI-3812 has anti-cancer effects on both imatinib-sensitive and resistant CML cells. We have also shown that BI-3812 may potentially increase the sensitivity of CML cells to imatinib. These results provide new directions for the treatment of TKI-resistant patients with BCR/ABL amplification.
Ethics approval and consent to participate
This study was carried out in accordance with the recommendations of Good Clinical Practice. The protocol was approved by the Biomedical Ethics Committee of The Second Affiliated Hospital of Chongqing Medical University (2021209). All subjects gave written informed consent in accordance with the Declaration of Helsinki.
Data availability statement
The data associated with our study are all included in article/suppmaterial/referenced in article.
CRediT authorship contribution statement
Yingying Xiao: Investigation. Fang Deng: Supervision. Yun Luo: Funding acquisition. Teng Wang: Writing – review & editing, Supervision, Funding acquisition.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Footnotes
Supplementary data to this article can be found online at https://doi.org/10.1016/j.heliyon.2024.e36640.
Appendix A. Supplementary data
The following are the Supplementary data to this article:
figs1.
References
- 1.Huntly B.J., Reid A.G., Bench A.J., et al. Deletions of the derivative chromosome 9 occur at the time of the Philadelphia translocation and provide a powerful and independent prognostic indicator in chronic myeloid leukemia. Blood. 2001;98(6):1732–1738. doi: 10.1182/blood.v98.6.1732. [DOI] [PubMed] [Google Scholar]
- 2.Rowley J.D. Letter: a new consistent chromosomal abnormality in chronic myelogenous leukemia identified by quinacrine fluorescence and Giemsa staining. Nature. 1973;243(5405):290–293. doi: 10.1038/243290a0. [DOI] [PubMed] [Google Scholar]
- 3.Jamieson C.H., Ailles L.E., Dylla S.J., et al. Granulocyte-macrophage progenitors as candidate leukemic stem cells in blast-crisis CML. N. Engl. J. Med. 2004;351(7):657–667. doi: 10.1056/NEJMoa040258. [DOI] [PubMed] [Google Scholar]
- 4.Huang X., Cortes Jkantarjian H. Estimations of the increasing prevalence and plateau prevalence of chronic myeloid leukemia in the era of tyrosine kinase inhibitor therapy. Cancer. 2012;118(12):3123–3127. doi: 10.1002/cncr.26679. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 5.Basso K., Saito M., Sumazin P., et al. The integrated biochemical and computational approach identifies BCL6 direct target genes controlling multiple pathways in normal germinal center B cells. Blood. 2010;115(5):975–984. doi: 10.1182/blood-2009-06-227017. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 6.Hatzi KMelnick A. Breaking bad in the germinal center: how deregulation of BCL6 contributes to lymphomagenesis. Trends Mol. Med. 2014;20(6):343–352. doi: 10.1016/j.molmed.2014.03.001. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 7.Ci W., Polo J.M., Cerchietti L., et al. The BCL6 transcriptional program features repression of multiple oncogenes in primary B cells and is deregulated in DLBCL. Blood. 2009;113(22):5536–5548. doi: 10.1182/blood-2008-12-193037. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 8.Guo J., Liu Y., Lv J., et al. BCL6 confers KRAS-mutant non-small-cell lung cancer resistance to BET inhibitors. J. Clin. Investig. 2021;131(1) doi: 10.1172/JCI133090. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 9.Hirata Y., Ogasawara N., Sasaki M., et al. BCL6 degradation caused by the interaction with the C-terminus of pro-HB-EGF induces cyclin D2 expression in gastric cancers. Br. J. Cancer. 2009;100(8):1320–1329. doi: 10.1038/sj.bjc.6605010. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 10.Logarajah S., Hunter P., Kraman M., et al. BCL-6 is expressed in breast cancer and prevents mammary epithelial differentiation. Oncogene. 2003;22(36):5572–5578. doi: 10.1038/sj.onc.1206689. [DOI] [PubMed] [Google Scholar]
- 11.Brunet A., Bonni A., Zigmond M.J., et al. Akt promotes cell survival by phosphorylating and inhibiting a Forkhead transcription factor. Cell. 1999;96(6):857–868. doi: 10.1016/s0092-8674(00)80595-4. [DOI] [PubMed] [Google Scholar]
- 12.Kawabata K.C., Zong H., Meydan C., et al. BCL6 maintains the survival and self-renewal of primary human acute myeloid leukemia cells. Blood. 2021;137(6):812–825. doi: 10.1182/blood.2019001745. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 13.Huth T.K., Staines Dmarshall-Gradisnik S. ERK1/2, MEK1/2, and p38 downstream signaling molecules impaired in CD56 dim CD16+ and CD56 bright CD16 dim/- natural killer cells in Chronic Fatigue Syndrome/Myalgic Encephalomyelitis patients. J. Transl. Med. 2016;14:97. doi: 10.1186/s12967-016-0859-z. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 14.Luo F., Shi J., Shi Q., et al. ERK and p38 upregulation versus Bcl-6 downregulation in Rat kidney epithelial cells exposed to prolonged hypoxia. Cell Transplant. 2017;26(8):1441–1451. doi: 10.1177/0963689717720296. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 15.O'Hare T., Zabriskie M.S., Eiring A.M., et al. Pushing the limits of targeted therapy in chronic myeloid leukemia. Nat. Rev. Cancer. 2012;12(8):513–526. doi: 10.1038/nrc3317. [DOI] [PubMed] [Google Scholar]
- 16.Basso Kdalla-Favera R. BCL6: master regulator of the germinal center reaction and key oncogene in B cell lymphomagenesis. Adv. Immunol. 2010;105:193–210. doi: 10.1016/S0065-2776(10)05007-8. [DOI] [PubMed] [Google Scholar]
- 17.Hurtz C., Hatzi K., Cerchietti L., et al. BCL6-mediated repression of p53 is critical for leukemia stem cell survival in chronic myeloid leukemia. J. Exp. Med. 2011;208(11):2163–2174. doi: 10.1084/jem.20110304. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 18.Kerres N., Steurer S., Schlager S., et al. Chemically induced degradation of the oncogenic transcription factor BCL6. Cell Rep. 2017;20(12):2860–2875. doi: 10.1016/j.celrep.2017.08.081. [DOI] [PubMed] [Google Scholar]
- 19.Cardenas M.G., Yu W., Beguelin W., et al. Rationally designed BCL6 inhibitors target activated B cell diffuse large B cell lymphoma. J. Clin. Investig. 2016;126(9):3351–3362. doi: 10.1172/JCI85795. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 20.Akerfelt M., Morimoto R.I., Sistonen L., et al. Heat shock factors: integrators of cell stress, development and lifespan. Nat. Rev. Mol. Cell Biol. 2010;11(8):545–555. doi: 10.1038/nrm2938. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 21.Whitesell L., Lindquist S. Inhibiting the transcription factor HSF1 as an anticancer strategy. Expert Opin. Ther. Targets. 2009;13(4):469–478. doi: 10.1517/14728220902832697. [DOI] [PubMed] [Google Scholar]
- 22.Dai C., Whitesell L., Rogers A.B., et al. Heat shock factor 1 is a powerful multifaceted modifier of carcinogenesis. Cell. 2007;130(6):1005–1018. doi: 10.1016/j.cell.2007.07.020. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 23.Zhao Y., Liu H., Liu Z., et al. Overcoming trastuzumab resistance in breast cancer by targeting dysregulated glucose metabolism. Cancer Res. 2011;71(13):4585–4597. doi: 10.1158/0008-5472.CAN-11-0127. [DOI] [PMC free article] [PubMed] [Google Scholar]
Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
Data Availability Statement
The data associated with our study are all included in article/suppmaterial/referenced in article.