Expression of p110δ in MM cell lines and in patient MM cells. (A) Expression of p110α, β, γ, and δ in multiple myeloma (MM) cell lines was detected by immunoblotting using specific Abs. Anti–α-tubulin monoclonal antibody served as a loading control. (B) p110δ in patient MM cells was detected by immunoblotting using anti-p110δ Ab. Anti-GAPDH monoclonal antibody served as a loading control.