Epidermal growth factor receptor-targeted radioimmunotherapy of human head and neck cancer xenografts using 90Y-labeled fully human antibody panitumumab

Abstract

Panitumumab (ABX-EGF or Vectibix), the first fully human monoclonal antibody targeting epidermal growth factor receptor (EGFR), was approved by the Food and Drug Administration for treatment of patients with metastatic colorectal cancer. Here, we report for the first time the radioimmunotherapy (RIT) of EGFR-positive human head and neck cancer in a nude mouse model using pure beta(-) emitter (90)Y-labeled panitumumab. Biodistribution and planar gamma-imaging studies were carried out with (111)In-DOTA-panitumumab. The RIT efficacy of (90)Y-DOTA-panitumumab was evaluated in UM-SCC-22B tumor model. CD31, Ki67, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling, and H&E staining were done on UM-SCC-22B tumor sections after treatment. The tumor uptake of (111)In-DOTA-panitumumab in UM-SCC-22B tumor-bearing nude mice was 26.10 +/- 4.93, 59.11 +/- 7.22, 44.57 +/- 9.80, 40.38 +/- 7.76, and 14.86 +/- 7.23 % injected dose per gram of tissue at 4, 24, 72, 120, and 168 hours after injection, respectively. Immunotherapy with cold panitumumab (four doses of 10 mg/kg) did not cause significant antitumor effect. RIT with a single dose of 100 microCi (90)Y-DOTA-panitumumab caused significant tumor growth delay and improved the survival in UM-SCC-22B tumor model. A single dose of 200 microCi (90)Y-DOTA-panitumumab led to almost complete tumor regression (tumor volumes were 34.83 +/- 11.11 mm(3) and 56.02 +/- 39.95 mm(3) on days 0 and 46 after treatment, respectively). Histopathologic analysis of tumors and normal organs further validated the therapeutic efficacy and limited systemic toxicity of (90)Y-DOTA-panitumumab. The high tumor uptake and prolonged tumor retention, as well as effective therapy, reveal that (90)Y-DOTA-panitumumab may be a promising radioimmunotherapeutic agent to treat EGFR-positive solid tumors.

Figure 1

A, immunofluorescence staining of UM-SCC-22B tumor cells and tissues for EGFR using panitumumab as the primary antibody. B, saturation binding of ¹²⁵I-panitumumab on UM-SCC-22B cells. C, in vitro inhibition of ¹²⁵I-panitumumab binding to EGFR on UM-SCC-22B human head and neck cancer cells by DOTA-panitumumab and panitumumab. Points, mean (n = 3); bars, SD.

Figure 2

A, biodistribution of ¹¹¹In-DOTA-panitumumab in BALB/c nude mice bearing UM-SCC-22B tumors at 4 h, 1 d, 3 d, 5 d, and 7 d after injection. Columns, mean % ID/g (n = 4); bars, SD. B, the time–% ID/g uptake of ¹¹¹In-DOTA-panitumumab in tumor, blood, liver, kidney, and muscle. Points, mean (n = 4); bars, SD. Data were obtained from A.

Figure 3

Representative γ-images of BALB/c nude mice bearing the UM-SCC-22B human head and neck xenografts administered ~13 MBq ¹¹¹In-DOTA-panitumumab at 1, 3, and 4 d after injection. Arrows indicate the location of tumors (n = 2 per group).

Figure 4

A, growth curves of UM-SCC-22B tumors in six groups of mice after i.v. injection of 7.4 MBq ⁹⁰Y-DOTA-panitumumab, 3.7 MBq ⁹⁰Y-DOTA-panitumumab, 3.7 MBq ⁹⁰Y-hIgG, cold panitumumab (~6 μg), four doses of cold panitumumab (10 mg/kg) every 3 d, and saline. Points, mean (n = 5–6 per group); bars, SD. B, Kaplan-Meier survival curves of UM-SCC-22B tumor-bearing nude mice that received 7.4 MBq ⁹⁰Y-DOTA-panitumumab, 3.7 MBq ⁹⁰Y-DOTA-panitumumab, 3.7 MBq ⁹⁰Y-hIgG, cold panitumumab (~6 μg), four doses of cold panitumumab (10 mg/kg) every 3 d, and saline. The mice were sacrificed when the tumor size reached ≥1,500 mm³ (n = 5–6 per group).

Figure 5

A, mean body weight over time of the BALB/c nude mice administrated with 7.4 MBq ⁹⁰Y-DOTA-panitumumab, 3.7 MBq ⁹⁰Y-DOTA-panitumumab, 3.7 MBq ⁹⁰Y-hIgG, panitumumab, or saline. Points, mean (n = 5–6 per group); bars, SD. B, growth curves of the low EGFR-expressing MDA-MB-435 tumors in BALB/c nude mice after i.v. injection of 3.7 MBq ⁹⁰Y-DOTA-panitumumab or saline. Points, mean (n = 6 per group); bars, SD.

Figure 6

Immunofluorescence staining of CD31, Ki67, and TUNEL for UM-SCC-22B tumor tissues from groups treated with ⁹⁰Y-DOTA-panitumumab (3.7 MBq), ⁹⁰Y-DOTA-IgG (3.7 MBq), panitumumab, and saline (control). Scale bar, 100 μm.