Quantitative analysis of biomarkers defines an optimal biological dose for recombinant human endostatin in primary human tumors.
OBJECTIVE
In a recent study, we presented preliminary evidence for biological activity in a Phase I dose-finding study (15-600 mg/m(2)) of recombinant human endostatin in patients with refractory solid tumors. Here, we conducted additional biomarker analyses to correlate changes in tumor biology with dose.


METHODS
Excisional tumor biopsies were obtained at baseline and after 56 days of endostatin therapy. Laser scanning cytometry (LSC) was used to quantify biomarker levels in whole tissue sections. Apoptosis in tumor cells (TCs) and tumor-associated endothelial cells (ECs) was quantified by fluorescent three-color anti-CD31/terminal deoxynucleotidyl transferase-mediated nick end labeling staining. Microvessel densities were measured by LSC-guided vessel contouring. Levels of tumor-associated EC BCL-2 and hypoxia-inducible factor 1alpha were determined by immunofluorescence and LSC quantification. The results, including tumor blood flow measured by positron emission tomography, were analyzed using a quadratic polynomial model.


RESULTS
Significant increases in EC death and decreases in tumor microvessel density were observed, with maximal effects of endostatin at a dose of 249 mg/m(2) (95% confidence interval, 159-338) and 257 mg/m(2) (95% confidence interval, 183-331), respectively. In contrast, levels of TC death were uniformly low and did not correlate with endostatin dose. Maximal nuclear hypoxia-inducible factor 1alpha and minimal EC Bcl-2 levels were observed at approximately 250 mg/m(2), although the changes did not reach statistical significance.


CONCLUSIONS
The data suggest that endostatin had optimal biological activity at doses approximately 250 mg/m(2) in our cohort of patients. Endostatin's failure to induce high levels of TC death may explain its lack of significant clinical activity in this Phase I trial.
Davis
Darren W
DW
Department of Cancer Biology, The University of Texas M. D. Anderson Cancer Center, Houston, Texas, USA.
Shen
Yu
Y
Mullani
Nizar A
NA
Wen
Sijin
S
Herbst
Roy S
RS
O'Reilly
Michael
M
Abbruzzese
James L
JL
McConkey
David J
DJ
D020533:Angiogenesis Inhibitors / Q000008:administration & dosage*; D017209:Apoptosis / Q000187:drug effects*; D015415:Biomarkers / Q000032:analysis*; D015331:Cohort Studies; D003952:Diagnostic Imaging; D004305:Dose-Response Relationship, Drug; D043169:Endostatins / Q000008:administration & dosage*; D042783:Endothelial Cells / Q000473:pathology; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D020287:In Situ Nick-End Labeling; D009369:Neoplasms / Q000098:blood supply* / Q000737:chemistry / Q000473:pathology; D009389:Neovascularization, Pathologic / Q000188:drug therapy*; D019408:Platelet Endothelial Cell Adhesion Molecule-1 / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D011994:Recombinant Proteins / Q000008:administration & dosage; D014055:Tomography, Emission-Computed; D014157:Transcription Factors / Q000378:metabolism
D020533:Angiogenesis Inhibitors; D015415:Biomarkers; D043169:Endostatins; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D019408:Platelet Endothelial Cell Adhesion Molecule-1; D019253:Proto-Oncogene Proteins c-bcl-2; D011994:Recombinant Proteins; D014157:Transcription Factors