H19 and breast cancer: For example, nuclear lincRNAs need to be associated with chromatin-remodeling complexes to regulate transcription, e.g., HOTAIR.38 In addition, cytoplasmic lincRNAs mostly function as endogenous ‘sponges' for miRNAs and act as post-transcriptional regulators,39 such as LincROR.40 Recent findings revealed that cytoplasmic H19 functions as an endogenous sponge for the let-7 family of microRNAs to regulate cancer metastasis41 and muscle metabolism.42 In our study, H19 localized in the cytoplasm is associated with AGO2 and acts to sponge let-7 to inhibit its bioactivity in breast cancer cells.