High levels of proliferation regulators and an impaired senescence response pathway to identify early-stage breast tumors with a poor prognosis.

43 Background: Predicting the risk of tumour recurrence, and thus the need for chemotherapy, for lymph node-negative breast cancer patients is a significant problem for clinicians and patients. Methods: We have identified a ‘core proliferation signature,’ which is consistently high in proliferating primary cultures, and is downregulated during cellular senescence. Using a reverse engineering approach on a breast cancer-specific regulatory network, and confirmed by ChIP-seq analysis, we have identified a hierarchy of several highly interconnected Master Transcriptional Regulators upstream of these core proliferation genes. Results: Further analysis of the expression of these factors in breast cancer cohorts at the mRNA and protein levels reveals a remarkable ability to reliably predict recurrence risk for early-stage breast cancer. Strikingly, in our analyses, a combination of just two of these factors outperforms the currently used clinical biomarkers for breast cancer recurrence risk, as well as recently developed multi-gene prognostic assays. Moreover, the addition of the senescence regulator p16INK4A to this panel further increases its prognostic capability. Conclusions: We propose that this novel approach has succeeded in identifying ‘drivers’ of breast cancer proliferation which, when combined with a marker of senescence such as p16INK4A, successfully identify actively proliferating tumours with an impaired senescence response pathway. Furthermore, we suggest that this gene combination has the potential to become an improved prognostic assay for early-stage breast cancer.