Abstracts
2000 Digestive Disease Week

# 2456 Functional Interleukin-4 Receptor (IL-4R) and Interleukin-2 Receptor Common Gamma Chain (IL-2R-c) on Human Gastric Carcinomas: A Possible Mechanism for Cytokine Based Therapy.
Richard Essner, Tung Nguyen, Young Huynh, D. Michael Rose, Dave S. B. Hoon, Santa Monica, CA

Interleukins 2 and 4 play a critical role in the regulation of the immune response. Both of the receptors for these cytokines have been found on non-hematopoietic cells, including human gastric carcinoma cell lines and tissue specimens. IL-4 causes G1 phase cell-cycle arrest of gastric carcinoma cells expressing IL-4R; the effect directly correlates with the expression of IL-4R and is seen within 48 hr after treatment. Cells lacking IL-4R are unaffected by IL-4. We examined signal transduction pathways employed by IL-4 that may account for cell-cycle arrest of an established human gastric carcinoma cell line CRL 1739. Western blot analysis was performed on CRL 1739 cultured up to 48 hr in the presence of IL-4 (500 U/ml). Cells were lysed, protein-extracted, and electroblotted; blots were then probed with murine monoclonal antibodies to specific intracellular proteins. Western blotting of CRL 1739 with anti-phosphotyrosine antibody (4G10) demonstrated multiple (140 kDa, 100-130 kDa and 65 kDa) phosphoproteins seen only in IL-4 treated CRL 1739. Immunoprecipitation and blotting of CRL 1739 with specific secondary antibodies demonstrated that the 140 kDa phosphoprotein was the IL-4R, the 100 kDa phosphoprotein was the nuclear transcription factor STAT 6, the 130 kDa phosphoprotein was the janus kinase (JAK-1), the 120 kDa phosphoprotein was JAK-3, and the 65 kDa phosphoprotein was the IL-2R?c. RT-PCR with specific primers demonstrated CRL 1739 did not express the lymphocyte marker CD45, or IL-2Ra or IL- 2Rß chains. These results suggest that human gastric carcinomas may express functional cytokine receptors, including the IL-2R?c commonly found in association with the lymphocyte IL-2R. These receptors may be novel targets for directing cytokine-based therapy.