BACKGROUND: Imatinib mesylate (IM) resistance is an emerging problem for chronic myeloid leukemia (CML). Previous studies found that connexin 43 (Cx43) deficiency in the hematopoietic microenvironment (HM) protects minimal residual disease (MRD), but the mechanism remains unknown. METHODS: Immunohistochemistry assays were employed to compare the expression of Cx43 and hypoxia-inducible factor 1α (HIF-1α) in bone marrow (BM) biopsies of CML patients and healthy donors. A coculture system of K562 cells and several Cx43-modified bone marrow stromal cells (BMSCs) was established under IM treatment. Proliferation, cell cycle, apoptosis, and other indicators of K562 cells in different groups were detected to investigate the function and possible mechanism of Cx43. We assessed the Ca 2+ -related pathway by Western blotting. Tumor-bearing models were also established to validate the causal role of Cx43 in reversing IM resistance. RESULTS: Low levels of Cx43 in BMs were observed in CML patients, and Cx43 expression was negatively correlated with HIF-1α. We also observed that K562 cells cocultured with BMSCs transfected with adenovirus-short hairpin RNA of Cx43 (BMSCs-shCx43) had a lower apoptosis rate and that their cell cycle was blocked in G0/G1 phase, while the result was the opposite in the Cx43-overexpression setting. Cx43 mediates gap junction intercellular communication (GJIC) through direct contact, and Ca 2+ is the key factor mediating the downstream apoptotic pathway. In animal experiments, mice bearing K562, and BMSCs-Cx43 had the smallest tumor volume and spleen, which was consistent with the in vitro experiments. CONCLUSIONS Cx43 deficiency exists in CML patients, promoting the generation of MRD and inducing drug resistance. Enhancing Cx43 expression and GJIC function in the HM may be a novel strategy to reverse drug resistance and promote IM efficacy.
Animals ; Humans ; Mice ; Apoptosis ; Bone Marrow Cells ; Cell Communication ; Connexin 43/genetics* ; Gap Junctions/metabolism* ; Imatinib Mesylate/therapeutic use* ; K562 Cells ; Leukemia, Myelogenous, Chronic, BCR-ABL Positive/pathology* ; Mesenchymal Stem Cells/metabolism* ; Tumor Microenvironment ; Calcium/metabolism*

Objective To investigate the clinicopathological features of undifferentiated pancreatic carcinoma with osteoclast-like giant cells (UOC).Methods Clinical and pathological data of 6 patients with UOC admitted in Navy Medical University affiliated Changhai Hospital from April 2011 to December 2017 were retrospectively analyzed.The expressions of Cam5.2,EMA,CD68,vimentin,lysozyme,E-cad,C-erbB-2,p53,MUC1,MLH1,MSH2,MSH6,Osteoponin and Ki-67 were detected by immunohistochemistry,and Kras gene mutations was measured by fluorescence quantitative PCR method.Results There were two main types of UOC cells.One type was oval or spindle mononuclear tumor cells,and the other was osteoclast-like giant cells scattered among mononuclear cells.Immunohistochemical staining results showed that the epithelial markers like CAM5.2,EMA,E-cad,MLH1,MSH2,MSH6 and Ki-67 of the components of ductal adenocarcinoma in 6 UOC patients were all positively expressed,and the mesenchymal markers like vimentin,CD68,lysozyme and tumor-related markers like Her-2,p53 and MUC1 were all negatively expressed.Vimentin,CD68,lysozyme and Osteoponin were positively expressed in osteoclast-like giant cells,but epithelial markers like Cam5.2,EMA,E-cad,MLH1,MSH2 and MSH6 were negatively expressed.6 UOC patients all had K-ras codon 12 mutation,and the mutant type was GGT ＞ TGT,GGT ＞ GTT,GGT ＞ GCT,and no codon 13 mutation was observed.Conclusions Osteoclast-like giant cells may be reactive multinucleated giant cells rather than neoplastic components.