Quantitative real time-PCR of CD133 mRNA: A potential surrogate angiogenic marker of response for patients with metastatic sarcoma

20034 Background: CD133 antigen is a specific surface marker for circulating endothelial progenitor cells (CEPs), pivotal in post-natal angiogenesis. We hypothesize that changes in levels of the CD133 mRNA expression and vascular endothelial growth factor (VEGF) may correlate with tumor response. Methods: After informed consent, we obtained 48 peripheral blood samples from patients with metastatic sarcoma including gastrointestinal stroma tumors (GIST). There were 16-paired samples before and after treatment including chemotherapy, or surgery, or imatinib. Of 24 patients with metastatic GIST enrolled, seven were paired samples. We measured CD133 mRNA levels by method (Lin E et al AACR 2003# 5392) and VEGF levels by ELISA (Genzyme, MA). The measurements were done in duplicates in two experiments. Results: The mean CD133 levels and VEGF levels before and after treatment was in Table 1 . The treatment resulted in significant reduction of CD133 mRNA expression (p = 0.035) as well as the level of VEGF (p = 0.014). Three patients experienced increase in CD133 expression had progressive disease. Among the paired GIST patients, there was a trend of increased CD133 mRNA expression levels in patients with progressive disease, death, or tumor recurrence. CD133 mRNA levels appeared elevated among the imatinib naïve patients and imatinib appeared to reset CD133 mRNA levels among the responding GIST patients to that of healthy volunteers. Conclusion: CD133 mRNA expression levels in sarcoma patients measured by real time-PCR assay appeared to correlate with tumor response. Unpublished independent work with NASBA assay platform in other solid tumors supported our findings ( www.primagen.com ). Further work is needed to reduce assay variability, and to determine the sensitivity and specificity of assay comparing to flow cytometry and to test assay’s applicability in the antiangiogenic therapy of cancer and the angiogenic therapy of cardiovascular diseases. [Table: see text] No significant financial relationships to disclose.