ESR1 and cancer: Here, the chaperon interacts with different proto-oncogenes essential for the growth and survival of such cancer cells, eg., progesterone receptor (PR), tumor suppressor proteins P5, estrogen receptor (ER), angiogenesis transcription factor HIF-l alpha, anti-apoptopic kinase AKT, RAF-1 MAP kinase and variety of kinases of ErbB family including Her2/neu, as well as proteins downstream of Her2/neu [71,83].