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Research Articles: Therapeutics, Targets, and Development

Novel in vivo imaging shows up-regulation of death receptors by paclitaxel and correlates with enhanced antitumor effects of receptor agonist antibodies

Departments of ¹ Experimental Therapeutics, ² Experimental Diagnostic Imaging, and ³ Biostatistics and ⁴ Division of Cancer Medicine Phase I Program, University of Texas M.D. Anderson Cancer Center, Houston, Texas and ⁵ Human Genome Sciences, Inc., Rockville, Maryland

Requests for reprints: Razelle Kurzrock, Division of Cancer Medicine Phase I Program, University of Texas M.D. Anderson Cancer Center, Box 4221515, Holcombe Boulevard, Houston, TX 77230-1402. Phone: 713-794-1226; Fax: 713-563-0236. E-mail: rkurzroc{at}mdanderson.org

Abstract

Susceptibility to apoptosis by tumor necrosis factor–related apoptosis-inducing ligand (TRAIL) is mediated through cognate death receptor signaling. We hypothesized that auto-amplification of this apparatus would enhance antitumor effects in vivo and could be optimized using the results obtained from novel imaging techniques. We therefore imaged mice bearing human colorectal cancer (Colo205) tumor xenografts with HGS-ETR1 and HGS-ETR2 agonist antibodies to TRAIL receptor-1 (TRAIL-R1) and TRAIL-R2, respectively, after radiolabeling the antibodies. Paclitaxel significantly increased in vivo expression of TRAIL-R1 and TRAIL-R2 in a time-dependent manner. The imaging results were confirmed by immunoblots for steady-state protein levels (>20-fold increase in TRAIL-R1 and TRAIL-R2 levels in tumor xenografts by 48 h after paclitaxel administration). TRAIL-R1 and TRAIL-R2 mRNA expression did not change, suggesting that these effects were posttranscriptional. Sequential treatment with paclitaxel followed by HGS-ETR1 or HGS-ETR2 after 48 h resulted in markedly enhanced antitumor activity against Colo205 mouse xenografts. Our experiments suggest that sequential taxane treatment followed by TRAIL-R agonist antibodies could be applied in the clinic, and that novel imaging techniques using radiolabeled receptor antibodies may be exploitable to optimize sequence timing and patient selection. [Mol Cancer Ther 2006;5(12):2991–3000]

Grant support: M.D. Anderson Cancer Center CORE grant NIH CA-16672.

The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

Received 4/ 5/06; revised 9/ 8/06; accepted 10/10/06.