Human breast carcinoma cells express type IIIL-4 receptors and are sensitive to antitumor activity of a chimeric IL-4-Pseudomonas exotoxin fusion protein in vitro and in vivo

Background: Human breast carcinoma cell lines express high-affinity interle ukin-4 receptors (IL-4R). We examined the expression and structure of these receptors on primary and cultured breast carcinoma cell lines and normal b reast epithelial cells. We also tested the antitumor activity in vitro and in vivo of a fusion protein comprised of circular permuted IL-4 and truncat ed Pseudomonas exotoxin, termed IL-4(38-37)-PE38KDEL. Materials and Methods: Eight different primary cell cultures and cell lines of human breast carcinomas were examined for the expression of IL-4R by ra diolabeled binding, reverse transcription polymerase chain reaction (RT-PCR ) and Northern analyses, and subunit structure by crosslinking studies. The antitumor activity of IL-4 toxin was tested in vitro by cytotoxicity assay s and in vivo in a xenograft model in immunodeficient animals. Results: I-125-IL-4 specifically bound to primary cell cultures and cell li nes with a Iid ranging between 0.2 and 1 nM. Breast tumor cells were found to express IL-4R beta and IL-13R alpha' chains, but not IL-2R gamma(c) chai n. These cells were highly sensitive to the cytotoxic effect of IL-4(38-37) -PE38KDEL. The IC,, (concentration inhibiting protein synthesis by 50%) ran ged between approximately 0.005-1.5 nM. A normal breast epithelial cell cul ture was not sensitive to the cytotoxic activity of IL-4(38-37)PE38KDEL. MD A-MB231 human breast carcinoma cell line formed a rapidly growing tumor in nude mice. Intratumor and intraperitoneal administration of IL-4(38-37)-PE3 8KDEL caused a dose dependent regression of established tumors. A control t oxin, anti-Tac(Fv)-PE38KDEL, targeted to the IL-2 receptor a chain did not cause regression of these tumors. Conclusions: These results suggest that I L-4(38-37)-PE38KDEL may be a useful agent for targeting of IL-4 receptor po sitive human breast carcinomas and further studies should be performed to e xplore fully its potential.