A dickens tale of the treatment of advanced breast cancer: the past, the present, and the future

Metastatic breast cancer (MBC), a usually incurable disease, continues to vex physicians and patients. Recent decades have seen great improvements in the treatment of MBC, based on the availability of novel targeted therapeutics and more standard chemotherapeutic agents. This article describes the goals of therapy for MBC, the progress made against MBC in recent decades, the current standard of care, and the ongoing efforts of basic and translational researchers to transfer the fruits of modern scientific discovery to patients in the clinic.

ERα-dependent E2F transcription can mediate resistance to estrogen deprivation in human breast cancer

Most estrogen receptor α (ER)-positive breast cancers initially respond to antiestrogens, but many eventually become estrogen-independent and recur. We identified an estrogen-independent role for ER and the CDK4/Rb/E2F transcriptional axis in the hormone-independent growth of breast cancer cells. ER downregulation with fulvestrant or small interfering RNA (siRNA) inhibited estrogen-independent growth. Chromatin immunoprecipitation identified ER genomic binding activity in estrogen-deprived cells and primary breast tumors treated with aromatase inhibitors. Gene expression profiling revealed an estrogen-independent, ER/E2F-directed transcriptional program. An E2F activation gene signature correlated with a lesser response to aromatase inhibitors in patients' tumors. siRNA screening showed that CDK4, an activator of E2F, is required for estrogen-independent cell growth. Long-term estrogen-deprived cells hyperactivate phosphatidylinositol 3-kinase (PI3K) independently of ER/E2F. Fulvestrant combined with the pan-PI3K inhibitor BKM120 induced regression of ER(+) xenografts. These data support further development of ER downregulators and CDK4 inhibitors, and their combination with PI3K inhibitors for treatment of antiestrogen-resistant breast cancers.