[The Role and Possible Mechanism of T Cell Costimulatory Molecule CD28 Activation in Pathogenesis of Multiple Myeloma].

Objective: To investigate the effect of signals mediated by activated CD28 in promoting survival of multiple myeloma (MM) cells and metabolic fitness and its possible mechanism.

Methods: The expression of CD28 on 4 MM cell lines (XG2, XG1, RPMI 8226 and U266) was determined by flow cytometry. Two cell lines with the highest or lowest CD28 expression were selected. The proliferation, cell cycle, migration and apoptosis of MM cells in vitro were determined in medium containing high glucose concentration or CD28 agonist monoclonal antibody with different bioassays. shRNA interference assay was used to knock down the expression of CD28 on U266 cells. Then, the effect of activated CD28 on glucose uptake rate and drug resistance in MM cells were analyzed using fluorescent glucose analogues (2-NBDG). The expression of Glut1/4, HkII and Fasn was determined with real time quantitative PCR.

Results: Flow cytometry analysis showed that all the four tested MM cell lines expressed CD28 and U266 cells had the highest positive rate. The results of in vitro experiment showed that CD28 activation could significantly up-regulate the expression of Glut4 and HkII, promote MM cell metabolic remodeling, enhance 2-NBDG/glucose uptake, increase energy metabolism, thereby elevating cell proliferation and migration abilities, leading to an increase in the number of cells in S- and G₂-phases. Meanwhile, activated CD28 subsequently up-regulated resistance of MM cells to bortezomib or dexamethasone.

Conclusion: MM cells express high levels of CD28 abnormally, and activation of CD28 can promote up-regulation of glucose uptake in MM cells, thereby promoting cell proliferation and enhancing drug resistance.