Regulatory Molecules and Corresponding Processes of BCR-ABL Protein Degradation

The BCR-ABL fusion protein with strong tyrosine kinase activity is one of the molecular biological bases of leukemia. Imatinib (Gleevec), a specific targeted drug for the treatment of chronic myeloid leukemia (CML), was developed for inhibiting the kinase activity of the BCR-ABL fusion protein. Despite the positive clinical efficacy of imatinib, the proportion of imatinib resistance has gradually increased. The main reason for the resistance is a decrease in sensitivity to imatinib caused by mutation or amplification of the BCR-ABL gene. In response to this phenomenon, the new generation of tyrosine kinase inhibitors (TKIs) targeting the BCR-ABL fusion protein was developed to solve the problem. However this strategy only selectively inhibits the tyrosine kinase activity of the BCR-ABL protein without eliminating the BCR-ABL protein, it does not fundamentally cure the BCR-ABL-positive leukemia patients. With the accumulation of the knowledge of cellular molecular biology, it has become possible to specifically eliminate certain proteins by cellular proteases in a specific way. Therefore, the therapeutic strategy to induce the degradation of the BCR-ABL fusion protein is superior to the strategy of inhibiting its activity. The protein degradation strategy is also a solution to the TKI resistance caused by different BCR-ABL gene point mutations. In order to provide possible exploration directions and clues for eliminating the BCR-ABL fusion protein in tumor cells, we summarize the significant molecules involved in the degradation pathway of the BCR-ABL protein, as well as the reported potent compounds that can target the BCR-ABL protein for degradation.

[Mechanisms of recombinant adenovirus-mediated SD-HA fusion protein proliferation inhibition and induced apoptosis of K562 cells]

Objective: To investigate whether fusion protein SD-HA could regulate its downstream signaling molecule activity by competing with the phospho-BCR-ABL Y177 site, and its mechanisms to inhibit proliferation and induce apoptosis of K562 cells. Methods: Co-immunoprecipitation interaction technology analysis of fusion protein SD-HA functioned by potently binding to the phospho-BCR-ABL Y177 site, Ras, MAPK and Akt activities were observed in the Ad5F35-SD-HA-treated cells. Western blot analyses of SD-HA fusion protein on cell membrane receptor pathway to death cascade caspase-8, caspase-3 and PRAP were performed. Results: Exploration into the underlying mechanisms revealed that Ad5F35-SD-HA infection functioned by binding to the phospho-BCR-ABL Y177 site, which lead to a complex with Grb2. competitively disrupted the Grb2 SH2-phospho-BCR-ABL Y177 formation. The fusion protein SD-HA could reduce the activation of Ras and phosphorylation of MAPK (p-MAPK) and the expression level of p-ELK, inhibition of Ras-MAPK signaling pathway; SD-HA fusion protein could reduce p-Akt and Akt substrate p-GSK with inhibition of PI3K-Akt signaling pathway, thereby inhibiting the proliferation of K562 cells. Caspases-8-induced apoptosis signal could be activated by DED protein binding to DED domain of precursor caspases-8. Conclusions: The strategy of fusion protein SD-HA inhibiting-Y177 BCR-ABL and Grb2 binding could be used as a novel entry point for the treatment of chronic myeloid leukemia.

BCR-ABL1 tyrosine kinase inhibitors for the treatment of chronic myeloid leukemia

The management of chronic myeloid leukemia with BCR-ABL1 tyrosine kinase inhibitors has evolved chronic myeloid leukemia into a chronic, manageable disease. A patient-centered approach is important for the appropriate management of chronic myeloid leukemia and optimization of long-term treatment outcomes. The pharmacist plays a key role in treatment selection, monitoring drug–drug interactions, identification and management of adverse events, and educating patients on adherence. The combination of tyrosine kinase inhibitors with unique safety profiles and individual patients with unique medical histories can make managing treatment difficult. This review will provide up-to-date information regarding tyrosine kinase inhibitor-based treatment of patients with chronic myeloid leukemia. Management strategies for adverse events and considerations for drug–drug interactions will not only vary among patients but also across tyrosine kinase inhibitors. Drug–drug interactions can be mild to severe. In instances where co-administration of concomitant medications cannot be avoided, it is critical to understand how drug levels are impacted and how subsequent dose modifications ensure therapeutic drug levels are maintained. An important component of patient-centered management of chronic myeloid leukemia also includes educating patients on the significance of early and regular monitoring of therapeutic milestones, emphasizing the importance of adhering to treatment in achieving these targets, and appropriately modifying treatment if these clinical goals are not being met. Overall, staying apprised of current research, utilizing the close pharmacist–patient relationship, and having regular interactions with patients, will help achieve successful long-term treatment of chronic myeloid leukemia in the age of BCR-ABL1 tyrosine kinase inhibitors.

Reconsideration of BCR-ABL protein flow cytometric immunobead assay: how potent to diagnose and monitor chronic myeloid leukemia?

INTRODUCTION

Chronic myeloid leukemia (CML) is typically associated with the Philadelphia chromosome, resulting in the production of BCR-ABL fusion oncoprotein with upregulated tyrosine kinase activity. We aimed to evaluate a new flow cytometric immunobead assay to detect BCR-ABL protein in a group of patients with CML.

METHODS

We enrolled 49 patients with CML, whose qRT-PCR and/or cytogenetic analysis of Philadelphia chromosome aberration was available, including tyrosine kinase inhibitors (TKIs)-naïve and (TKIs)-treated patients with various levels of response. Twenty Philadelphia-negative healthy individuals were also enrolled to obtain analytical negative controls. Peripheral blood samples were analyzed for BCR-ABL fusion protein by flow cytometry.

RESULTS

The BCR-ABL fusion protein flow cytometric assay seemed efficacious to both diagnose the presence (P-value <0.0001) and distinguish the levels (P-value = 0) of the Philadelphia chromosome aberration. Groups of TKI-naïve and TKI-treated patients as well as levels of molecular/cytogenetic response to TKI-therapy were effectively discriminated (P-value <0.01). The receiver operating characteristic (ROC) curve analysis indicated the diagnostic value of the assay as excellent (AUC = 0.95, P-value = 0).

CONCLUSIONS

The evaluated BCR-ABL fusion protein assay might be useful for diagnosing and monitoring Philadelphia chromosome aberration.