The combination of two targeted drug therapies results in dramatic reduction in breast cancer cell growth in vitro, indicating a potentially powerful new approach to treating the condition. The two drug agents - trastuzumab and ZD1839 were found to work synergistically to inhibit the action of two different growth factors receptors, HER2 and epidermal growth factor receptor (EGFR).
Previous research has shown that these growth factor receptors are involved in 20 and 70 per cent of breast cancers, respectively, and it has been suggested that they interact with one another to ensure cell proliferation and survival. Trastuzumab and ZD1839 have been specifically developed to target these receptors.
The agents were tested singly and then in combination. Individually, the drugs inhibited cell growth by between 30 and 55 per cent. Working together, trastuzumab and ZD1839 reduced cell proliferation by 70 per cent.
The findings suggest that simultaneous inhibition of the action of both growth factor receptors exerts a greater anti-tumour effect. The approach could be expanded to treat other types of cancer. Eventually, these combinations of drugs may be used with conventional cell-killing drugs. Alternatively, conventional chemotherapy may be used for short courses at times when the disease is more aggressive and targeted therapy used at other times.