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A variety of human carcinoma cells express high levels of interleukin-13 receptorα2 chain, a primary binding subunit of IL-13R complex in vitro and in vivo. These receptors could be targeted by a chimeric fusion protein consisting of Interleukin-13 and a truncated form of Pseudomonas exotoxin (IL-13PE38). Microarray analysis of adrenomedullin (AM) transfected human prostate tumor PC-3 cells showed that human and rat AM up-regulated the IL-13Rα2 chain gene. We now demonstrate that IL-13Rα2 chain is also up regulated in two human breast tumor cell lines (MCF-7 and MDA-MB-231) and one prostate carcinoma (PC-3) cell line after treatment with AM. RT-PCR results confirmed that mRNAs for IL-13Rα2 were enhanced 2.5 to 4 fold in 24 and 48 hr AM treated cells, respectively compared to control cells. Indirect immunofluorescence assay (IFA) revealed that protein level of IL-13Rα2 were also increased in AM treated breast and prostate carcinoma cells. To understand the mechanism of up-regulation, actinomycin-D treatment studies were performed, which showed that new transcripts of IL-13Rα2 and AM genes were transcribed post-AM treatment. Similarly, cycloheximide treatment blocked 50% protein synthesis for both genes within 8 and 12 hr. To evaluate the biological function of the overexpressed IL-13Rα2 protein, AM treated cells were exposed with IL-13PE38. IC50 values (concentration at which IL13-PE38 inhibits protein synthesis by 50%) were found to be lower in adrenomedullin treated tumor cells compared to untreated cells. IFA showed that both proteins were co-localized within tumor cells indicating that AM may be responsible in molecular cross talk for the up-regulation of IL-13Rα2 chain protein. These studies suggest that IL13R2 chain can be up-regulated and this property can be exploited for breast and prostate cancer therapy.

[Proc Amer Assoc Cancer Res, Volume 45, 2004]

American Association for Cancer Research
2004