Figure 3. CDH2-Cx43 interaction and colocalization in BM biopsies of BC patients.

(A) Representative images of tissue sections from biopsies of BC patients (A and S2), hematological malignancy (S3), and benign tumor (S3). The slides were colabeled with anti–CDH2-PE (red), anti–Cx43-AF488 (green), and anti–pan-cytokeratin-AF405 (blue). Images were acquired with EVOS FL Auto 2, 200× magnification. Black arrows show colocalized Cx43 and CDH2 in the white areas (red + green + blue). Inset, zoomed regions of colocalized proteins. (B) Table summarizes the total number of sections positive for colocalized CDH2, Cx43 in pan-cytokeratin + cells. ImageJ software was used to count the colocalized cells in 10 fields/slide. The last column shows the percentages of colocalized CDH2-Cx43. See also Table S1 and Figs S2 and S3. (C, D) Computational and functional prediction of CDH2–Cx43 interaction using ZDOCK (C) and STRING (D), respectively. CDH2, Cadherin-2 (N-cadherin); TJP1, tight junction protein 1; CTNNB1, β catenin; GJA1, gap junction alpha protein 1(Cx43); JUP, junction plakoglobin; NEDD4, neural precursor cell expressed, developmentally down-regulated 4. (E) Whole cell lysates from MDA-MB-231 and T47D were immunoprecipitated with anti-CDH2 or IgG and then electrophoresed on 12% SDS–PAGE. The membranes were blotted with anti-Cx43 (light band at 43 kD). (F) Whole-cell lysated from MDA-MB-231 cells were subjected to immunoprecipitation (IP) with anti-CDH2 or anti-Cx43. The membrane was blotted with anti-CDH2. (G) MDA-MB-231 was transfected with pCMV2-CDH2 Flag and pcDNA 3.2-Cx43-HA. Protein lysates were immunoprecipitated with anti-Flag or anti-IgG and blotted with anti-Flag or anti-HA. (H) Lysates from cancer stem cells, isolated from MDA-MB-231 were immunoprecipitated with anti-IgG, anti-Cx43, or anti-CDH2. The samples were electrophoresed and then blotted with anti-CDH2. (I) BM biopsy from BC patient (#3) was subjected Proximity Ligation Assay with anti-CDH2 and anti-Cx43. The proximity of the two antibodies was determined using EVOS FL Auto 2, 600× magnification. Control slide was labeled with isotype control.

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