Detection methods of overexpression of HER2

By immunochemistry, it is possible to illustrate the presence of abnormal quantities of erb-B2 receptors on the surface of cancer cells and to develop a semiquantitative evaluation which is used in daily clinical practice.

HER-2 0+	HER-2 1+	HER-2 2+	HER-2 3+

HER2 3+: high magnification. The anti-erb-B2 antibody is blocked by receptors at the membrane surface, giving improved delimitation of each cancer cell carrying this abnormality (almost like plant cells).

(Documents courtesy of the Centre François Baclesse - Dr Denoux)

Using the FISH technique (Fluorescence In Situ Hybridisation), we can study the direct gene amplification.

Normal aspect	Weak amplification	Strong amplification
On the left picture (normal aspect), two genes (one from each parent chromosome) are detected in green or red according to the staining procedure. On the right picture, a strong amplification of the red gene may be observed with other genes (in green) in normal numbers.

For patients with a 2+ reaction in immunochemistry, for which the pathologist is uncertain as to the potential indication of treatment by trastuzumab (Herceptin™), the FISH technique proves to be very useful. Tumours among patients with a strong amplification will very probably be sensitive to antibody treatment.