To determine the contribution of Cx31 to breast tumorigenesis in vivo, we transplanted each of the HS578T and HCC1143 Cx31 partial depletion lines into the mammary fat pad of immune-compromised NOD-SCID/gamma (NSG) female mice and assayed for time of tumor onset and ethical endpoint (when the tumor reaches 2 cm in any dimension). This evidence concerns the gene GJB3 and neoplasm.