Elevated expression of VEGFR-2 and VEGFA in desmoplastic small round cell tumor (DSRCT) and activity of bevacizumab and irinotecan in a xenograft model of DSRCT

Abstract

10016 Background: Desmoplastic small round cell tumor (DSRCT) is an aggressive tumor with poor response to multimodality therapies. Given the vascular nature of many DSRCT, we sought to determine if VEGF targeting could be effective in a preclinical model of DSRCT. Methods: RNA was extracted from frozen tumor samples (DSRCT, alveolar soft part sarcoma, alveolar rhabdomyosarcoma, synovial sarcoma, and Ewing sarcoma) and a human DSRCT cell line, JN-DSRCT. Microarray profiling utilized Affymetrix U133A/B or Affymetrix U133 Plus 2.0 chips. DSRCT xenografts were established by intramuscular injection of 20 million JN-DSRCT cells into the lower extremity of SCID/bg mice. A primary tumor developed within 8 - 12 weeks with concomitant development of abdominal metastases. Mice were treated during primary tumor growth with bevacizumab (5ug/kg IP weekly), irinotecan (2.5mg/kg IP ×10 days q3 weeks), or a combination of both. Results: Microarray data demonstrated an average of 4.5 times higher RNA expression of VEGFR-2 (KDR) in DSRCT tumor samples as compared to the other translocation-associated sarcomas (p = 3.6 E-12). VEGFR-2 was highly expressed in the JN-DSRCT line as compared to other sarcoma lines. VEGFA was also highly overexpressed in the DSRCT line and tumor samples when compared to the other translocation-associated sarcomas (2.5 times, p = 1.1E-10). Xenografts treated with bevacizumab had slowed growth over 100 days compared to control groups (volume of 0.52 mm3 vs 1.52, p = 0.002). Marked long term regressions were evident following treatment with the combination of irinotecan plus bevacizumab compared with irinotecan alone (0.12mm3 vs 0.44 at 100 days, p < 0.0001). Conclusions: VEGFR-2 and VEGFA are overexpressed in DSRCT. DSRCT xenografts were highly responsive to bevacizumab or bevacizumab plus irinotecan. Taken together, the expression data and the sustained response of DSRCT xenografts to bevacizumab suggest that VEGF-dependent angiogenesis is important for DSRCT tumor biology and represents an attractive target for therapy. These studies suggest that irinotecan and bevacizumab should be considered for inclusion in clinical trials for the treatment of DSRCT. No significant financial relationships to disclose.