Tumor-targeting A1-R Suppressed an Imatinib-resistant Gastrointestinal Stromal Tumor with C-kit Exon 11 and 17 Mutations

Gastrointestinal stromal tumor (GIST) is a refractory disease in need of novel efficacious therapy. The aim of our study was to evaluate the effectiveness of tumor-targeting A1-R ( A1-R) using on a patient derived orthotopic xenograft (PDOX) model of imatinib-resistant GIST. The GIST was obtained from a patient with regional recurrence, and implanted in the anterior gastric wall of nude mice. The GIST PDOX mice were randomized into 3 groups of 6 mice each when the tumor volume reached 60 mm: G1, control group; G2, imatinib group (oral administration [p.o.], daily, for 3 weeks); G3, A1-R group (intravenous [i.v.] injection, weekly, for 3 weeks). All mice from each group were sacrificed on day 22. Relative tumor volume was estimated by laparotomy on day 0 and day 22. Body weight of the mouse was evaluated 2 times per week. We found that A1-R significantly reduced tumor growth in contrast to the untreated group ( = 0.001). In addition, we found that A1-R was more effective compared to imatinib ( = 0.013). Furthermore, Imatinib was not significantly effective compared to the control group (P = 0.462). These results indicate that A1-R may be new effective therapy for imatinib-resistant GIST and therefore a good candidate for clinical development of this disease.