LMO2 regulates STAT3 localization to the nucleus in breast cancer cells.

STAT3 phosphorylation and transcriptional activity promote breast cancer growth and metastasis. We have previously reported that the transcriptional adaptor LMO2 is required for metastasis in breast cancer and promotes STAT3-JAK2 interaction, leading to STAT3 phosphorylation in metastasis-initiating cells. Here, we find that constitutively activated STAT3 is insufficient to drive metastasis in the absence of LMO2. Mechanistically, we find that LMO2 is required not only for STAT3 phosphorylation in the cytoplasm but also for STAT3 translocation to the nucleus. These data suggest that LMO2 promotes STAT3 activation and localization to the nucleus in breast cancer cells.