TRAF3 and cancer: This is consistent with our recent report that TGFβ1 degrades TRAF3 in MSCs to increase RANKL production through activation of NF-κB17 and that expression of RANKL by MSCs (OBs/fibroblasts) mediates the interactions of circulating cancer cells with the host microenvironment not only in bone13,14, but also in lung18,40 to promote cancer metastasis.