Focus on HER2 in breast cancer

Slide Deck

View the HER2 slide deck

Several large clinical studies have shown a relationship between the frequency of HER2 overexpression/amplification and breast cancer.

Source	N	Definition of HER2 overexpression/HER2 amplification	Percentage of tumors with HER2 overexpression/HER2 amplification
Slamon et al, Science, 1987¹²	189	Two-fold or greater amplification of HER2 gene by Southern blot	30%
Paik et al, J Natl Cancer Inst, 2000¹⁵	2034	Definite membrane staining by IHC in any tumor cell	29%
Owens et al, Clin Breast Cancer, 2004¹⁶	16,092 (FISH) 116,736 (IHC)	Two-fold or greater amplification of HER2 gene by FISH 2+ or higher result by IHC	23% 20%
Seshadri et al, J Clin Oncol, 1993¹¹	1056	Two-fold or greater amplification of HER2 gene by slot blot	21%
Andrulis et al, J Clin Oncol, 1998¹³	580	Two-fold or greater amplification of HER2 gene by Southern blot, slot blot, and/or RT-PCR	20%

HER3 is frequently co-expressed with HER2 in breast cancer, as shown in tumor cell lines, mouse transgenic tumors, and human primary breast cancers¹⁷

Interestingly, HER2 overexpression has been significantly correlated with overexpression of other tumor markers in breast cancer. These include:

Vascular endothelial growth factor (VEGF)¹⁸
- VEGF is responsible for tumor angiogenesis, the growth of new blood vessels that supply the tumor with oxygen and nutrients^18,19
- A 2004 study of 611 patients with primary breast cancer showed a significant correlation between overexpression of HER2 and 2 VEGF isoforms (P<0.001)
- The aggressive phenotype of HER2-overexpressing tumors may be due in part to VEGF
- For more information on VEGF in breast cancer, visit www.ResearchVEGF.com
Estrogen (ER) and progesterone receptors (PR)
- In a 1993 study (N=1056), HER2 overexpression was significantly associated with negative ER and PR status (P<0.00001 and P<0.0006, respectively)¹¹
- Hormones such as estrogen and progesterone may suppress HER2 expression, so that hormone-receptor–positive tumors are less likely to be HER2-positive²⁰
- This interaction may explain why many HER2-positive tumors are unresponsive to hormone therapy²⁰