Growth inhibition of xenotransplanted human carcinomas by a monoclonal antibody directed against the epidermal growth factor receptor.

In the athymic nude mice model with xenotransplanted human carcinomas, the effect of a monoclonal antibody (MAb 425), directed against the human epidermal growth factor (EGFR), on tumour growth was studied. Five different solid human breast carcinomas and one vulvar epidermoid cancer cell line (A431) were transplanted in nude mice, and treated with MAb 425 2.2 mg intraperitoneally (i.p.) on day 7 post-transplantation. Tumours with EGFR concentrations of > or = 16 fmol/mg soluble cytosolic protein showed growth inhibition, whereas the growth pattern of EGFR-negative tumours was unaffected. Variation of MAb 425 dosage (1.1 versus 2.2 mg) revealed no difference in the growth inhibiting effect. Different application schedules (application on day 0, 12 or 26) showed different onsets and durations of tumour growth inhibition. Repeated application (1.1 mg, day 0 and 12) was followed by a prolonged inhibitory effect. Our results suggest that growth inhibition of EGFR-positive tumours by MAb 425 may lead to an additional treatment option for patients with EGFR-positive cancer.