Osteopontin induces growth of metastatic tumors in a preclinical model of non-small lung cancer

Abstract

Osteopontin (OPN), also known as SPP1 (secreted phosphoprotein), is an integrin binding glyco-phosphoprotein produced by a variety of tissues. In cancer patients expression of OPN has been associated with poor prognosis in several tumor types including breast, lung, and colorectal cancers. Despite wide expression in tumor cells and stroma, there is limited evidence supporting role of OPN in tumor progression and metastasis. Using phage display technology we identified a high affinity anti-OPN monoclonal antibody (hereafter AOM1). The binding site for AOM1 was identified as SVVYGLRSKS sequence which is immediately adjacent to the RGD motif and also spans the thrombin cleavage site of the human OPN. AOM1 efficiently inhibited OPNa binding to recombinant integrin αvβ3 with an IC50 of 65 nM. Due to its unique binding site, AOM1 is capable of inhibiting OPN cleavage by thrombin which has been shown to produce an OPN fragment that is biologically more active than the full length OPN. Screening of human cell lines identified tumor cells with increased expression of OPN receptors (αvβ3 and CD44v6) such as mesothelioma, hepatocellular carcinoma, breast, and non-small cell lung adenocarcinoma (NSCLC). CD44v6 and αvβ3 were also found to be highly enriched in the monocyte, but not lymphocyte, subset of human peripheral blood mononuclear cells (hPBMCs). In vitro, OPNa induced migration of both tumor and hPBMCs in a transwell migration assay. AOM1 significantly blocked cell migration further validating its specificity for the ligand. OPN was found to be enriched in mouse plasma in a number of pre-clinical tumor model of non-small cell lung cancers. To assess the role of OPN in tumor growth and metastasis and to evaluate a potential therapeutic indication for AOM1, we employed a KrasG12D-LSLp53fl/fl subcutaneously implanted in vivo model of NSCLC which possesses a high capacity to metastasize into the lung. Our data indicated that treatment of tumor bearing mice with AOM1 as a single agent or in combination with Carboplatin significantly inhibited growth of large metastatic tumors in the lung further supporting a role for OPN in tumor metastasis and progression.

New Blocking Antibodies Impede Adhesion, Migration and Survival of Ovarian Cancer Cells, Highlighting MFGE8 as a Potential Therapeutic Target of Human Ovarian Carcinoma

“…Thus rather than inducing migration by inducing acquisition of a mesenchymal state [9], or by binding to phosphatidylserine at the cell surface, as described for intestinal epithelial cells [22], MFGE8 here is instead a chemoattractant for tumor cells. How this function is regulated, and whether the receptors involved are also αvβ3/5 integrins will have to be evaluated, but it seems similar to a recently described effect of another ligand of αvβ3/5 integrins, osteopontin, on lung cancer [23]. …”

Role of osteopontin in the pathophysiology of cancer

“…In each of the studies, abrogating the expression of OPN resulted in decreased proliferation and/or survival, malignant and/or metastatic potential. In NSCLC, the use of a monoclonal antibody AOM1 identified using phage display technology was shown to be effective in significantly inhibiting growth of large metastatic tumors in the lung when used as a single agent or in combination with Carboplatin (Shojaei et al, 2012). …”

SPP1 targeted by miR-4262 in gastric cancer functions as an enhancer of cell growth and correlates with dismal prognosis

“…Evidence for the involvement of SPP1 in human malignancies indicates SPP1 as one of the promotors in multiple cancers. For instance, in colon cancer, SPP1 is highly expressed and significantly promotes tumor cell proliferation and angiogenesis (24); in non-small lung cancer, high expression of SPP1 induces tumor growth and enhances cell mobility (25). Recently, several studies have observed and suggested SPP1 as an indicator of the prognosis in GC (26)(27)(28).…”