IL-4 receptors on human medulloblastoma tumours serve as a sensitive target for a circular permuted IL-4-Pseudomonas exotoxin fusion protein.
Cytotoxins directed to interleukin-4 receptors have shown to mediate relatively selective cytotoxicity against a variety of human cancer cells in vitro and in vivo. In an ongoing Phase I clinical trial, a recombinant protein comprised of circularly permuted IL-4 fused to a mutated form of Pseudomonas exotoxin (the fusion protein termed IL-4(38-37)-PE38KDEL or cpIL4-PE) has shown antitumour activity against malignant glioma. Human medulloblastomas are neuroectodermal tumours that occur in children and have a poor prognosis. The goal of this study was to determine whether human medulloblastoma derived cell lines express interleukin-4 receptor and whether interleukin-4 receptor expression is accompanied by sensitivity to cpIL4-PE. Medulloblastoma cell lines express interleukin-4 receptor at the protein and mRNA levels as determined by binding, indirect immunofluorescence and RT--PCR studies. These cells expressed IL-4Ralpha (also known as IL-4Rbeta) and IL-13Ralpha1 (also known as IL-13Ralpha') chains, however common gamma(c), a component of the interleukin-4 receptor system in immune cells was not detected. Consistent with the expression of IL-4R, cpIL4-PE was found to be highly and specifically cytotoxic to four of five medulloblastoma cell lines. Susceptibility of medulloblastoma cell lines to cpIL4-PE seemed to correlate closely to the functional IL-4 binding sites in general as demonstrated by 125I-IL-4 binding, but did not seem to correlate with mRNA or cell surface immunoreactive receptor protein expression. The sensitivity of medulloblastoma cells to cpIL4-PE could be eliminated by concurrent incubation with IL-4 or IL-13, but not with IL-2. None of these cell lines showed any change in proliferation upon treatment with exogenous IL-4. These studies establish the interleukin-4 receptor as a medulloblastoma-associated target for possible tumour-directed cancer therapy. Further studies are warranted to investigate interleukin-4 receptor expression in primary medulloblastoma tumours and sensitivity to cpIL-4PE in vitro and in vivo.
Joshi
B H
BH
Laboratory of Molecular Tumour Biology, Division of Cellular and Gene Therapies, Center for Biologics, Evaluation and Research, Food and Drug Administration, NIH Building 29B, Room 2NN10, 29 Lincoln Dr., Bethesda, Maryland, MD 20892, USA.
Leland
P
P
Silber
J
J
Kreitman
R J
RJ
Pastan
I
I
Berger
M
M
Puri
R K
RK
D036002:ADP Ribose Transferases; D001427:Bacterial Toxins; D001932:Brain Neoplasms / Q000188:drug therapy* / Q000503:physiopathology; D005098:Exotoxins / Q000493:pharmacokinetics* / Q000627:therapeutic use*; D005455:Fluorescent Antibody Technique; D006801:Humans; D018796:Immunoconjugates / Q000493:pharmacokinetics / Q000627:therapeutic use; D008527:Medulloblastoma / Q000188:drug therapy* / Q000503:physiopathology; D012333:RNA, Messenger / Q000032:analysis; D019948:Receptors, Interleukin-4 / Q000096:biosynthesis / Q000187:drug effects* / Q000502:physiology; D011993:Recombinant Fusion Proteins; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A
D036002:ADP Ribose Transferases; D001427:Bacterial Toxins; D005098:Exotoxins; D018796:Immunoconjugates; D012333:RNA, Messenger; D019948:Receptors, Interleukin-4; D011993:Recombinant Fusion Proteins; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A