Double-edged Sword Role of Iron-loaded Ferritin in Extracellular Vesicles

Human epidemiological and animal studies have demonstrated that excess iron is a risk for cancer. The responsible mechanisms are: 1) increased intracellular iron catalyzes the Fenton reaction to generate hydroxyl radicals, leading to mutagenic oxidative DNA lesions; 2) iron is necessary for cellular proliferation as cofactors of many enzymes. Thus, iron-excess milieu promotes selecting cellular evolution to ferroptosis-resistance, a major basis for carcinogenesis. Ferritin is a 24-subunit nanocage protein required for iron storage under the regulation of the iron-regulatory protein (IRP)/iron-responsive element (IRE) system. Ferritin is a serum marker, representing total body iron storage. However, how ferritin is secreted extracellularly has been unelucidated. We recently discovered that an exosomal marker CD63 is regulated by the IRP/IRE system and that iron-loaded ferritin is secreted as extracellular vesicles under the guidance of nuclear receptor coactivator 4 (NCOA4). On the other hand, we found that macrophages under asbestos-induced ferroptosis emit ferroptosis-dependent extracellular vesicles (FedEVs), which are received by nearby mesothelial cells, resulting in significant mutagenic DNA damage. Therefore, cells, including macrophages, can share excess iron with other cells, via iron-loaded ferritin packaged in extracellular vesicles as safe non-catalytic iron. However, similar process, such as one involving FedEVs, may cause accumulation of excess iron in other specific cells, which may eventually promote carcinogenesis.

Development and identification of mouse anti-human S100 A9 natural protein / 中国免疫学杂志

Objective:To prepare and identify the mouse anti-human monoclonal antibodies ( mAbs) using leukocytes as im-munogens. Methods: The mice were immunized using human peripheral blood leukocytes. Then, use of B lymphocyte hybridoma technology preparation of mAbs,followed screening by immunocytochemistry and limited dilution. The secreted mAbs were identified by immunoprecipitation,mass spectrometry,Western blot,ELISA and immunohistochemistry. Results:The 35 positive polyclonal cells were obtained,of which 11 strains secreted mAbs against S100A9. And one strain was used to prepare monoclonal antibody. The purified mAb against S100A9 were purified and identified as IgG1 subtype,with the titer,purity and affinity constant was 1∶3. 18×105,95% and 3. 54×108 L/mol,respectively. This mAb generally had 0. 12% crossed reactivity to S100A8 ,and showed little or no cross reactivity to S100A12 and S100A13. The prepared monoclonal antibodies can specifically recognizes the S100A9 antigen in human breast cancer tissues. Conclusion:Successful preparation of mAb against S100A9,which can secrete specific mAb against S100A9 protein with high titers and specificity have been established successfully,which laid the foundation for the immunology application.