HER3 and downstream pathways are involved in colonization of brain metastases from breast cancer

• Published in: Breast cancer research : BCR Vol. 12; no. 4; p. R46
• Main Authors: Da Silva, Leonard, Simpson, Peter T, Smart, Chanel E, Cocciardi, Sibylle, Waddell, Nic, Lane, Annette, Morrison, Brian J, Vargas, Ana Cristina, Healey, Sue, Beesley, Jonathan, Pakkiri, Pria, Parry, Suzanne, Kurniawan, Nyoman, Reid, Lynne, Keith, Patricia, Faria, Paulo, Pereira, Emilio, Skalova, Alena, Bilous, Michael, Balleine, Rosemary L, Do, Hongdo, Dobrovic, Alexander, Fox, Stephen, Franco, Marcello, Reynolds, Brent, Khanna, Kum Kum, Cummings, Margaret, Chenevix-Trench, Georgia, Lakhani, Sunil R
• Format: Journal Article
• Language: English
• Published: England BioMed Central Ltd 01-01-2010; National Library of Medicine - MEDLINE Abstracts; BioMed Central
• Subjects: Blotting, Western; Brain cancer; Brain Neoplasms - genetics; Brain Neoplasms - metabolism; Brain Neoplasms - secondary; Breast cancer; Breast Neoplasms - genetics; Breast Neoplasms - metabolism; Breast Neoplasms - pathology; Class I Phosphatidylinositol 3-Kinases; Development and progression; ErbB Receptors - genetics; Female; Gene Expression Profiling; Gene Expression Regulation, Neoplastic; Gene mutations; Genetic aspects; Health aspects; Humans; Immunohistochemistry; Mitogen-Activated Protein Kinases - metabolism; Mutation; Oligonucleotide Array Sequence Analysis; Phosphatidylinositol 3-Kinases - genetics; Proto-Oncogene Proteins c-akt; ras Proteins - genetics; Receptor, ErbB-3 - genetics; Receptor, ErbB-3 - metabolism; Risk factors; Signal Transduction; Australia; Czech Republic
• ISSN: 1465-542X; 1465-5411; 1465-542X
• DOI: 10.1186/bcr2603

Metastases to the brain from breast cancer have a high mortality, and basal-like breast cancers have a propensity for brain metastases. However, the mechanisms that allow cells to colonize the brain are unclear.
We used morphology, immunohistochemistry, gene expression and somatic mutation profiling to analyze 39 matched pairs of primary breast cancers and brain metastases, 22 unmatched brain metastases of breast cancer, 11 non-breast brain metastases and 6 autopsy cases of patients with breast cancer metastases to multiple sites, including the brain.
Most brain metastases were triple negative and basal-like. The brain metastases over-expressed one or more members of the HER family and in particular HER3 was significantly over-expressed relative to matched primary tumors. Brain metastases from breast and other primary sites, and metastases to multiple organs in the autopsied cases, also contained somatic mutations in EGFR, HRAS, KRAS, NRAS or PIK3CA. This paralleled the frequent activation of AKT and MAPK pathways. In particular, activation of the MAPK pathway was increased in the brain metastases compared to the primary tumors.
Deregulated HER family receptors, particularly HER3, and their downstream pathways are implicated in colonization of brain metastasis. The need for HER family receptors to dimerize for activation suggests that tumors may be susceptible to combinations of anti-HER family inhibitors, and may even be effective in the absence of HER2 amplification (that is, in triple negative/basal cancers). However, the presence of activating mutations in PIK3CA, HRAS, KRAS and NRAS suggests the necessity for also specifically targeting downstream molecules.