The devil is in the methods: lineage tracing, functional screens and sequencing, hormones, tumour-stroma interactions, and expansion of human breast tumours as xenografts

The third international meeting of the European Network for Breast Development and Cancer (ENBDC) again promoted the sharing of protocols and ideas between groups working on breast development and cancer. Graduate students, postdocs and research associates were encouraged to attend. The following topics were covered in depth: functional screens and sequencing, hormones, lineage tracing, the propagation of human breast tumours as xenografts and tumour-stroma interactions.Chris Lord from the Breakthrough Breast Cancer Research Centre at the Institute of Cancer Research in London presented examples of the power of genome-wide functional screens. First, his group combined tamoxifen treatment of breast cancer cells in vitro and a small interfering RNA (siRNA) screen for kinases in an approach to identify events leading to tamoxifen sensitivity and tamoxifen resistance. They identified low cyclin-dependent kinase (CDK)10 expression as an important mediator of resistance to endocrine therapy in breast cancer. Knockdown of CDK10 blocked its inhibitory effect on ETS2, which in turn induced transcription of c-Raf and led to activation of the ERK/mitogen-activated protein kinase (MAPK) pathway and resistance to tamoxifen [1]. They also used a pooled genome-wide small hairpin RNA (shRNA) screen in the presence or absence of tamoxifen, coupled with massively parallel sequencing, and identified groups of genes the silencing of which increased sensitivity (for example C10orf72, C15orf55/NUT, EDF1, ING5, KRAS) or resistance (for example, BAP1, CLPP, GPRC5D, NAE1, NF1) to tamoxifen [2]. Second, they used a synthetic lethal unbiased shRNA screen for identifying sensitizers to a poly (ADP-ribose) polymerase (PARP) inhibitor in BRCA1 wild-type breast cancer cells. Knockdown of RAD51D, a novel ovarian cancer susceptibility gene, dramatically increased cell death upon PARP inhibition [3]. Third, they used a kinome-wide siRNA screen to identify genetic dependencies of breast cancer cell l