HMGA1 and breast cancer: To test in vivo the effect of HMGA1 on the DSB repair, we used the low HMGA1-expressing breast cancer MCF7 cells stably transfected with a plasmid expressing a HA-tagged HMGA1a (MCF7_HMGA1a) and control cells transfected with the empty vector (MCF7_CTRL) (S1 Fig, panel A).