Cx43-Mediated Bone Marrow Stromal Cells Affect the Imatinib Resistance of K562 Cells Via Ca 2+ -Dependent Gap Junction Intercellular Communication (GJIC)

Background: Imatinib resistance is an emergent problem for CML patients. We noticed that in some haematological malignancies, the deficiency of GJIC in the haematopoietic microenvironment seemed to decrease chemotherapeutic efficacy and induce drug resistance. Previous study found that increased expression of Connexin43(Cx43) on stromal cells promote leukemia apoptosis. However, the effect and mechanism on reversing imatinib resistance of CML cells are unknown. Method: Firstly the expression of Cx43 and HIF-1α in BM biopsy specimens of CML patients were measured by immunohistochemical assay. Then co-cultured/Transwell model of Cx43 gene-modified BMSCs and K562 cells with/without imatinib were generated, survival state of K562 cells were measured by flow cytometer and CCK8 assay. Thirdly ATP and Ca2+ concentration were tested in K562 cells with flow cytometer and luminometer respectively, and Ca2+ related apoptotic signalling pathways were tested by western blot. Finally we used nude mouse with bearing tumor to verified our hypothesis. Founding: Our findings demonstrated that Cx43 deficiency in bone marrow protects CML from imatinib, leads to MRD and ultimately induces drug resistance. Enhancing Cx43 expression in the haematopoietic microenvironment may be a new strategy to eliminate MRD and enhance the killing effects of chmotherapeutics. Interpretation: This study provides a promising direction to eliminate MRD and reverse imatinib resistance for CML patients by repairing GJIC functions in haematopoietic microenvironment. Funding: National Key Research Program, National Natural Science Foundation of China and the Foundation of Xinqiao Hospital. Declaration of Interest: The authors have no conflicts of interest to declare. Ethical Approval: This study was approved by the Ethics Committee of Third Military Medical University, and all procedures were performed in accordance with the ethical standards of the Ethics Committee of Third Military Medical University and the Declaration of Helsinki.