Does the molecular classification of breast cancer point the way for biomarker identification in prostate cancer?

Table 1 A summary of some of the key similarities between breast and prostate cancer

CaP	Breast cancer
Incidence - 134 per 100000/yr (United Kingdom)	Incidence - 164 per 100000/yr (United Kingdom)
Risks - Increasing age, ethnicity (Black African and Black Caribbean men have highest risk), family history, obesity	Risks - Increasing age, family history, smoking, obesity
AR - Prostate epithelial cells are primarily androgen dependent and AR mutation, promiscuity and hypersensitivity are key stages in cancer progression	AR - Certain subgroups of triple negative breast cancers express the AR. These patients have been shown to have worse prognosis than AR - ve groups
BRCA1 and BRCA2 - Epidemiological studies have demonstrated a link between breast and CaP within families. However only a small proportion of CaPs can be linked to these gene mutations	BRACA1 and BRACA2 - Extremely important genes involved in cell cycle regulation. Responsible for many breast cancers - particularly in younger patients
ESCs - Genetic signatures associated with ESCs have been linked to poorly differentiated CaP. Loss of action of PTEN and P53 and TMPRSS-ERG fusions are frequently observed in these cells	ESC - The ESC signature has recently been demonstrated to be present in some high grade breast cancers
HER2 - The HER2 oncogene is expressed in 20% of localised CaP. This rises to 60% of metastatic CaP. It has been associated with increased cell proliferation and poorer outcomes in some studies, however the use of anti HER2 antibodies has not demonstrated improved patient outcomes	HER2 - HER2 expression has been clearly demonstrated to define a molecular sub group of breast cancer with characteristic survival. An example of early success in the development of “targeted therapy” anti-HER2 antibodies such as trastuzumab (Herceptin) have revolutionised HER2 positive breast cancer treatment

CaP: Prostate cancer; AR: Androgen receptor; BRACA: Breast cancer; ESC: Embryonic stem cell; HER2: Human epidermal growth factor receptor 2.