These splice variants signify a significant source of functional diversity in the proteome (Heckler and Riggins 2015); for instance, the expression of the ERRβL splice variant can augment ERα-dependent gene activation (Bombail et al. 2010), and activated ERRβ2 splice variants are potent inhibitors of karyokinesis in breast carcinoma cells, including TNBC (Heckler et al. 2016). This evidence concerns the gene ESR1 and breast carcinoma.