PTEN and breast cancer: MiR-26a directly targets several anti-apoptotic proteins, such as E2F Transcription Factor 3 (E2F3), myeloid cell leukaemia-1 (Mcl-1), metadherin (MTDH), enhancer of zeste homolog 2 (EZH2), and phosphatase and tensin homolog (PTEN) which are up-regulated in breast cancer.