NRG1 and cancer: We needed both the DNA and RNA sequencing to detect the fusions in cancers: there were too few supporting reads in the RNA sequencing to call them from RNA alone, while prediction from the DNA rearrangements alone would only have been provisional, particularly in our 14 examples where there were multiple breaks in NRG1. MDA-MB-175 itself is a case in point: with 7 breakpoints called within NRG1 (Fig. 2), prediction of a fusion would have been very difficult and uncertain.