I'm looking at surface LDLR expression in huh7 cells by flow cytometry. As known as, sterol deficiency-induced LDLR up-regulation. Therefore, the cells were treated with 5% LPDS for 24 hours. And then, scraped the cell, was fixed with 2% PFA for 10min on ice, wash twice, and incubated with primary antibody (cayman, 1:100) for 1 hour at room temperature, wash twice, and incubated with secondary antibody (1:500) for 1 hour at room temperature. However, LPDS-induced LDLR up-regulation was not stable. Sometimes LPDS could increase LDLR expression, and sometimes could not. Could anyone give me some recommendations to induce LDLR expression stably? Thanks.