Second, we investigated the association between EXO1 expression and inherent signalling / transcription factor activity of MYC and E2F transcription factors in a panel of breast cancer cell lines comprising few higher level EXO1 expressing cells (HBL100, SKBR3 and MDA-MB-231) and a couple of lower level EXO1 expressing cells (MCF7 and T47D) by in vitro reporter assay (Figure 3E). The gene discussed is EXO1; the disease is breast cancer.