ADAM12 belongs to the family of ADAMs (A Disintegrin And Metalloproteases), which are multidomain proteins involved in a variety of biological processes (for review see Wewer et al., 2005). Human ADAM12 exists in two splice variants; a long form, ADAM12-L encompassing pro-, metalloprotease, disintegrin, cysteine-rich, EGF-like, transmembrane, and cytoplasmic domains, as well as a secreted form, ADAM12-S, lacking the transmembrane and cytoplasmic part. ADAM12 is an active metalloprotease and holds cell adhesion activities through complex interactions with the cell surface receptors, integrins and syndecans. Importantly, ADAM12 is upregulated in several human tumors and the level of ADAM12 in urine from breast cancer patients correlates with disease stage. Also, we recently reported that ADAM12 increases tumor aggressiveness in a mouse model of breast cancer, i.e. time to tumor burden was reduced, whereas tumor burden, metastasis, and histological grade were all increased (Kveiborg et al., 2005). Moreover, tumors from mice overexpressing ADAM12 exhibit decreased tumor cell apoptosis, whereas stromal cell apoptosis was increased. Supporting these findings, in vitro studies showed that ADAM12 protects malignant cells from apoptosis while conferring increased apoptotic sensitivity in non-malignant cells. In many cancers abnormal events lead to elevated activity of the non-receptor tyrosine kinase c-Src (henceforth Src), thereby inducing transformation and metastasis. Interestingly, mouse ADAM12 has previously been shown to bind Src, become phosphorylated by the oncogenic form of Src, and co-localize with Src to actin structures in vitro. We here report the detailed mapping of the molecular interaction between the cytoplasmic tail of human ADAM12-L and Src. Extensive deletion and mutation analysis localized the interaction site to the SH3-binding site proximal to the transmembrane domain of ADAM12 and the SH3-domain of Src. Also, mutant forms of the Src SH3-domain that are not able to bind to proline-rich regions were used to validate the direct interaction. Based on these findings, we hypothesize that ADAM12 interacts with Src in tumor cells and thus might play mutual roles in cancer. Wewer, U.M., Engvall, E. and Albrechtsen, R. (2005) ADAM12: the long and the short of it. In: The ADAM Family of Proteases (Hooper, N.M. and Lendeckel, U., Eds.), Proteases in Biology and Disease, Vol. 4, Springer, The Netherlands. Kveiborg, M., Frohlich, C., Albrechtsen, R., et al. A role for ADAM12 in breast tumor progression and stromal cell apoptosis. Cancer Res. 65:4754-61, 2005.

[Proc Amer Assoc Cancer Res, Volume 47, 2006]