Fig. 4: The phosphorylation of CD37Y¹³ inhibits phagocytosis.

A CD37 null cells (MCF7) were transfected with kinase-dead (Y¹³A, Y²⁷⁴A) and constitutively active (Y¹³E, Y²⁷⁴E) CD37 alleles, and cells were collected and subjected to Immunoblot detecting p-CD37Y¹³ and p-CD37Y²⁷⁴. B Macrophages derived from different cancer species were collected and subjected to immunoblot detecting p-CD37Y¹³ and p-CD37Y²⁷⁴. CD37 null cell (MCF7) transfected with constitutively active (Y¹³E, Y²⁷⁴E) CD37 alleles were applied as a positive control. C Macrophages derived from different cancer species were collected and subjected to cytometry to detect the proportion of p-CD37Y¹³ and p-CD37Y²⁷⁴ positive cells. D The statistical analysis of p-CD37Y¹³⁺ cells in CD37⁺ macrophages, BRCA breast cancer, GBM glioblastoma, CRC colon-rectum cancer, LC lung cancer, PDAC pancreatic ductal adenocarcinoma, n = 30 for each cancer species, data were shown as mean and individual dots. E The statistical analysis of p-CD37Y²⁷⁴⁺ cells in CD37⁺ macrophages, BRCA breast cancer, GBM glioblastoma, CRC colon-rectum cancer, LC lung cancer, PDAC pancreatic ductal adenocarcinoma, n = 30 for each cancer species, data were shown as mean and individual dots. F CD37-positive phagocytes were sorted from the in vitro phagocytosis assay, and immunoblotting detecting p-CD37Y¹³ and p-CD37Y²⁷⁴ in CD37⁺ phagocytes was applied, CD37 null cell (MCF7) transfected with constitutively active (Y¹³E, Y²⁷⁴E) CD37 alleles were applied as positive control. G Cytometry detecting the proportion of p-CD37Y¹³ and p-CD37Y²⁷⁴ positive cells in CD37⁺ phagocytes as described. H The statistical analysis of (G), n = 3, data were presented as mean ± SD, two-tailed unpaired T-test, ***p < 0.0001. I CD37-negative and -positive THP1 and U937 cells were sorted. CD37-positive cells were treated with Naratuximab, or transfected with CD37Y²⁷⁴E, CD37-negative cells were transfected with CD37Y¹³E, in vitro phagocytosis assay was applied. J The statistical analysis of the percentage of phagocytosis in cells with modifications, n = 3, data were presented as mean ± SD, two-tailed unpaired T-test, p < 0.0001 for all the statistical analyses. K CD37-negative and -positive THP1 and U937 cells were sorted and subjected to immunoblot detecting p-CD37Y¹³ and p-CD37Y²⁷⁴. L Macrophages derived from different cancer species were divided into CD37-negative and -positive subgroups, immunoblot detecting p-CD37Y¹³ and p-CD37Y²⁷⁴ was applied. All the experiments were repeated at least three times with similar results.