MicroRNA 345 (miR345) regulates KISS1-E-cadherin functional interaction in breast cancer brain metastases

Brain metastases manifest the advanced stage of breast cancer disease with poor prognosis for patient survival. Recent reports demonstrate that some therapeutic agents can activate the expression of several breast cancer-associated genes, whose products are involved in the onset and development of brain metastases. In this study, we discovered a functional link between KISS1 and E-cadherin that could be observed in both primary brain metastatic lesions and paired cell lines, such as parental CN34TGL and MDA-MB-231 and their respective brain metastatic subclones CN34Brm2Ctgl and MDA-MB-231Br. Remarkably, expression of KISS1 and E-cadherin genes consistently showed an inverse correlation in all of the above cell/tissue types. While E-cadherin expression was strongly upregulated in metastatic clones isolated from blood and brain, the levels of this protein in parental MDA-MB-231 cell line was low. Furthermore, E-cadherin upregulation can be artificially induced in MDA-MB-231Br and CN34Brm2Ctgl cell populations by knocking down KISS1 expression directly or through overexpressing the miR345 mimic. In the aggregate, our data suggest that the tumor microenvironment, which controls breast cancer spreading via miR345-regulated KISS1 expression, might modulate metastatic spreading by a mechanism(s) involving upregulation of E-cadherin production.