Combined effects of radiation and interleukin-13 receptor-targeted cytotoxin on glioblastoma cell lines.
OBJECTIVE
Interleukin-13 receptor-targeted cytotoxin (IL13-PE38) is highly cytotoxic to human glioblastoma (GBM) cells. Although this molecule is being tested in a multicenter Phase III clinical trial (PRECISE Study) in patients with recurrent disease, the activity of IL13-PE38 when combined with radiation therapy has not been investigated.


METHODS
Cytotoxicity of IL13-PE38 to GBM cell lines was assessed by protein synthesis inhibition and clonogenic assays, and the growth of GBM cells receiving radiation was assessed by thymidine uptake assays. Expression of IL-13 receptor alpha2 (IL-13Ralpha2) messenger ribonucleic acid (mRNA) in GBM cells exposed to radiation was assessed by quantitative reverse transcriptase/polymerase chain reaction (RT-PCR) and IL-13R density by radiolabeled IL-13 binding assays.


RESULTS
Prior irradiation of GBM cell lines followed by IL13-PE38 treatment did not enhance cytotoxicity; however, concomitant 5 Gy irradiation and IL13-PE38 treatment was highly cytotoxic to T98G, M059K, A172, and LN-229 cell lines as determined by cell viability assays. There was a statistically significant decrease in number of viable cells in IL13-PE38 and irradiated cells compared with irradiated cells alone (p < 0.05) or IL13-PE38 treated cells alone (p < 0.05). In contrast, U251, SN19, and U87MG cell lines did not show any combined effect. These results were confirmed by clonogenic assays. Although three GBM cell lines-U251, SN19, and A172-showed 2.8- to 13.9-fold upregulation of IL-13Ralpha2 mRNA expression at 6-24 h after exposure to 5 Gy radiation, specific binding of radiolabeled IL-13 to these cell lines did not improve.


CONCLUSIONS
Our results suggest that concomitant radiation therapy and IL13-PE38 treatment may be beneficial for the treatment of patients with GBM. This strategy may be worth exploring in animal models of human glioma.
Kawakami
Koji
K
Laboratory of Molecular Tumor Biology, Division of Cellular and Gene Therapies, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, MD 20892, USA.
Kawakami
Mariko
M
Liu
Qi
Q
Puri
Raj K
RK
D001427:Bacterial Toxins / Q000627:therapeutic use*; D003131:Combined Modality Therapy; D005098:Exotoxins / Q000627:therapeutic use; D005909:Glioblastoma / Q000188:drug therapy* / Q000378:metabolism / Q000532:radiotherapy*; D006801:Humans; D000922:Immunotoxins / Q000627:therapeutic use*; D053661:Interleukin-13 Receptor alpha1 Subunit; D012333:RNA, Messenger / Q000378:metabolism; D011829:Radiation Dosage; D018123:Receptors, Interleukin / Q000187:drug effects* / Q000378:metabolism; D053660:Receptors, Interleukin-13; D011993:Recombinant Fusion Proteins / Q000627:therapeutic use*; D014407:Tumor Cells, Cultured / Q000378:metabolism / Q000528:radiation effects; D014410:Tumor Stem Cell Assay / Q000379:methods; D015854:Up-Regulation
D001427:Bacterial Toxins; D005098:Exotoxins; C508181:IL13RA1 protein, human; D000922:Immunotoxins; D053661:Interleukin-13 Receptor alpha1 Subunit; D012333:RNA, Messenger; D018123:Receptors, Interleukin; D053660:Receptors, Interleukin-13; D011993:Recombinant Fusion Proteins