INDUCIBLE KNOCKOUT OF THE INTERLEUKIN-2 RECEPTOR ALPHA CHAIN - EXPRESSION OF THE HIGH-AFFINITY IL-2 RECEPTOR IS NOT REQUIRED FOR THE IN VITRO GROWTH OF HTLV-I-TRANSFORMED CELL LINES

摘要

Adult T cell leukemia (ATL) is an aggressive malignancy that is associated with HTLV-I infection and characterized by constitutive expression of the high-affinity interleukin-2 receptor. The cu subunit of the high-affinity receptor (IL-2R alpha), which is normally present only on activated T cells, is specifically upregulated by HTLV-I and constitutively expressed on fresh leukemic cells from ATL patients as well as cell lines transformed by HTLV-I in vitro. Here we directly address the functional significance of IL-2R alpha expression in HTLV-I transformed cell lines by using an endoplasmic reticulum-targeted single-chain antibody to inhibit the cell surface expression of IL-2 alpha. Using constitutive and tetracycline-repressible systems to express the ER-targeted antibody against IL-2R alpha, we have reduced cell surface expression of IL-2R alpha by more that 2 logs of mean fluorescence intensity to virtually undetectable levels in the IL-2-independent HTLV-I-transformed cell lines C8166-45 and HUT102. No toxicity was associated with the intracellular retention of IL-2R alpha, and the growth rate of the IL-2R alpha-negative cells was in each case comparable to that of the parental cell line. We conclude that cell surface expression of IL-2R alpha is dispensable for the in vitro growth of these HTLV-l-transformed cells.