1. ¹Department of Veterinary Biosciences, The Ohio State University, Columbus, OH 43210, USA
2. ²Medical Sciences, Indiana University School of Medicine, Bloomington, IN 47405, USA
3. ³Department of Dermatology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
4. ⁴Department of Biochemistry & Molecular Biology, Indianapolis University School of Medicine, Indianapolis, IN 46202, USA
5. ⁵Department of Pathology and Laboratory Medicine, Indianapolis School of Medicine, Indianapolis, IN 46202, USA
6. ⁶Department of Human Cancer Genetics, The Ohio State University, Columbus, OH 43210, USA

Correspondence: Dr G Lorch, Department of Veterinary Biosciences, The Ohio State University, Goss Labs, 1925 Coffey Road, Columbus, OH 43210, USA. E-mail: lorch.2@osu.edu

⁷These two authors contributed equally to this paper.

Received 12 March 2007; Revised 2 May 2007; Accepted 7 May 2007; Published online 29 May 2007.

Abstract

The purpose of this study was to evaluate the role of the epidermal growth factor receptor (EGFR) in parathyroid hormone-related protein (PTHrP) expression and humoral hypercalcaemia of malignancy (HHM), using two different human squamous-cell carcinoma (SCC) xenograft models. A randomised controlled study in which nude mice with RWGT2 and HARA xenografts received either placebo or gefitinib 200 mg kg^-1 for 3 days after developing HHM. Effectiveness of therapy was evaluated by measuring plasma calcium and PTHrP, urine cyclic AMP/creatinine ratios, and tumour volumes. The study end point was at 78 h. The lung SCC lines, RWGT2 and HARA, expressed high levels of PTHrP mRNA as well as abundant EGFR protein, but very little erbB2 or erbB3. Both lines expressed high transcript levels for the EGFR ligand, amphiregulin (AREG), as well as, substantially lower levels of transforming growth factor- (TGF-), and heparin binding-epidermal growth factor (HB-EGF) mRNA. Parathyroid hormone-related protein gene expression in both lines was reduced 40–80% after treatment with 1 M of EGFR tyrosine kinase inhibitor PD153035 and precipitating antibodies to AREG. Gefitinib treatment of hypercalcaemic mice with RWGT2 and HARA xenografts resulted in a significant reduction of plasma total calcium concentrations by 78 h. Autocrine AREG stimulated the EGFR and increased PTHrP gene expression in the RWGT2 and HARA lung SCC lines. Inhibition of the EGFR pathway in two human SCC models of HHM by an anilinoquinazoline demonstrated that the EGFR tyrosine kinase is a potential target for antihypercalcaemic therapy.