MOLECULAR ANALYSIS OF THE IL-2 RECEPTOR-BETA CHAIN GENE EXPRESSED IN HUMAN TUMOR-CELLS

Interleukin-2 (IL-2) is recognized as a T cell growth factor. We have previously reported that human carcinoma cell lines are inhibited in g rowth by exogenous IL-2, which binds to the IL-2 receptor beta (IL-2R beta) chain ubiquitously expressed on the surface of tumor cells. A po ssibility was considered that IL-2R beta on carcinomas responsible for negative signaling was different from that expressed on hematopoietic cells. To investigate this possibility, mRNA for the IL-2R beta chain was amplified and compared in carcinoma and lymphoid cells. Using RT- PCR with pairs of sense-antisense oligonucleotide primers specific for the various regions of extracellular, transmembrane and intracellular domains of the IL-2R beta chain, we amplified mRNA obtained from thre e human carcinoma cell lines and human lymphoid cells as controls. The identity of the amplicons was confirmed by Southern analysis with the P-32-labeled cDNA probe coding for the entire span of the IL-2R beta chain. In addition, genomic DNA obtained from the tumor cell lines was sequenced to examine the possibility that a mutation is present in th e gene coding for the intracellular IL-2R beta chain domain. No mutati ons or deletions were detected. The message for all three domains of t he beta chain was identical in tumor cells and in normal lymphoid cell s used as controls. Also, by Western blot and northern analyses no dif ferences between IL-2R beta chain in tumors vs that expressed in lymph oid cells were demonstrable. The IL-2R gamma chain, which participates in IL-2/IL-2R signaling pathway, was expressed in tumor cells. Expres sion of JAK1 transcripts in these cells was comparable to that in lymp hocytes. However, RT-PCR analysis identified differences in expression of JAK3 splice variants (B and M) in tumor cells. These differences m ay be responsible for altered downstream signaling by IL-2. Overall, o ur data indicate that the same IL-2/IL-2R pathway is operative in huma n carcinomas and in normal epithelial or lymphoid cells.