Research Interests

Breast Cancer Bone Metastasis. : (A) Osteolytic lesions (arrow) in knee bones generated by i.c.-injected MDA-MD-231 breast cancer cells (notice: pathological fracture of distal femoral conyle due to destructive tumor growth); (B) Histological section of knee joint: osteolytic cancer in distal femoral and proximal tibial metaphyses as well as tibial epiphysis (asterisk). (C) Blood vessels at the growth plate/metaphyseal interface stained positively with a-mCLCA1 pAb; (D) RT-PCR with mCLCA1-specific primers; pT: proximal tibia; mT mid-portion of tibia; (E) RT-PCR with hCLCA2 specific primers; BM: marrow; BMEC: bone marrow-derived endothelial cells; (F) hCLCA2 protein extracted from surface-biotinylated BMEM: IP with pre-immune rabbit IgG (1), a-hCLCA2 pAb4 (2), and a-hCLCA2 pAb18 (3); WB-detection with streptavidin-HRP; (G) Serum-starved (S-S; 24h in medium alone) MDA-MB-231 plated onto hCLCA2- (1&5), placental laminin- (2), fibronectin- (3), and PLL (4)-coated dishes (30';37C), then lysed: IP: a-FAK; WB: a-FAK and a-pY (notice: FAK is activated by hCLCA2 (1) and fibronectin (3), but not laminin (2) and PLL (4); activation by hCLCA2 is blocked by a-hCLCA2 pAb18 (5); (H) S-S MDA-MB-231 plated on hCLCA-coated dishes (30';37C), then lysed: IP: a-Met, a-b4; WB: a-Met; a-pY (notice neither b4 nor Met are activated by hCLCA2-ligation to b4); (I) S-S BMEC plated onto b4 integrin- (1) or PLL (2)-coated dishes (30';37C), then lysed: IP: a-AKT; WB: a-AKT; a-pS473 (notice: AKT is activated by b4/hCLCA2), but not PLL). T. I: Bone colony assay.

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Research in my laboratory focuses on cellular and molecular aspects of cancer metastasis. Specifically, our interests are directed towards understanding the contribution of endothelial cell adhesion molecules (addessins) to site-specific metastasis. Two addressins constitutively expressed by endothelia of select lung and bone vascular branches have been identified, isolated, purified, and cloned by our laboratory. The first is hCLCA2 a member of a newly discovered family of Ca⁺⁺-dependent chloride channel proteins (CLCAs). hCLCA2 mediates adhesion of breast and other cancer cells via tumor cell surface-associated b4 integrin under both static and flow conditions. The interacting binding domains comprise a conserved decapeptide located at the C-terminus of the von Willebrand A-domain of hCLCA2 and the SDL-domain of the b4 integrin. Anti-adhesive, anti-hCLCA2 and b4-integrin antibodies as well as peptides comprising the binding domains protect lungs and bone from metastatic colonization. The hCLCA2/b4 adhesion triggers signaling cascades that are essential to tumor cell extravasation and lung and bone colonization (activation of FAK and its downstream effectors MAPK and PI3K in breast cancer cells). The second adhesion molecule is dipeptidyl peptidase IV (DPP IV), which binds polymeric fibronectin (FN) [via a consensus sequence in FNIII13, -14, and -15] associated with the surface of lung- and bone-metastatic breast cancer cells by a domain distinct from its substrate binding site. Binding of breast cancer cells to DPP IV is blocked effectively by anti-DPP IV mAb 6A3, anti-fibronectin antibodies and, competitively, by soluble DPP IV, but not by soluble fibronectin. Current studies are directed to identifying the interaction of these addressins in mediating pulmonary and bone vascular arrest of blood-borne cancer cells, to elucidating the signaling events that promote adhesion-dependent signaling cascades responsible for early metastatic intravascular tumor cell growth and for the initiation of angiogenesis in emerging metastatic colonies, and to generating a mouse model with conditional knockout of the mouse hCLCA2 orthologue (mCLCA5) in adult mouse endothelium. New therapeutical modalities (e.g., aptamers binding to adhesion domains) are tested for anti-metastatic efficacy.