Shafaat A. Rabbani

Selective Inhibition of Matrix Metalloproteinase-14 Blocks Tumor Growth, Invasion, and Angiogenesis

Inhibition of specific matrix metalloproteinases (MMP) is an attractive noncytotoxic approach to cancer therapy. MMP-14, a membrane-bound zinc endopeptidase, has been proposed to play a central role in tumor growth, invasion, and neovascularization. Besides cleaving matrix proteins, MMP-14 activates proMMP-2 leading to an amplification of pericellular proteolytic activity. To examine the contribution of MMP-14 to tumor growth and angiogenesis, we used DX-2400, a highly selective fully human MMP-14 inhibitory antibody discovered using phage display technology. DX-2400 blocked proMMP-2 processing on tumor and endothelial cells, inhibited angiogenesis, and slowed tumor progression and formation of metastatic lesions. The combination of potency, selectivity, and robust in vivo activity shows the potential of a selective MMP-14 inhibitor for the treatment of solid tumors.

Expression of RANKL/RANK/OPG in primary and metastatic human prostate cancer as markers of disease stage and functional regulation.

Late‐stage prostate cancer patients are refractory to hormone therapy and exhibit a high propensity to develop skeletal metastasis. In this regard, the role of a novel cytokine system belonging to the tumor necrosis factor (TNF) family that is critical for osteoclastic osteolysis and that consists of receptor activator of NF‐κB ligand (RANKL), its receptor (RANK), and decoy receptor osteoprotegerin (OPG) is of potential interest.

A Src/Abl Kinase Inhibitor, SKI-606, Blocks Breast Cancer Invasion, Growth, and Metastasis In vitro and In vivo

The central role of Src in the development of several malignancies, including breast cancer, and the accumulating evidence of its interaction with receptor tyrosine kinases, integrins, and steroid receptors have identified it as an attractive therapeutic target. In the current study, we have evaluated the effect of a Src/Abl kinase inhibitor, SKI-606, on breast cancer growth, migration, invasion, and metastasis. Treatment of human breast cancer cells MDA-MB-231 with SKI-606 caused a marked inhibition of cell proliferation, invasion, and migration by inhibiting mitogen-activated protein kinase and Akt phosphorylation. For in vivo studies, MDA-MB-231 cells transfected with the plasmid encoding green fluorescent protein (GFP; MDA-MB-231-GFP) were inoculated into the mammary fat pads of female BALB/c nu/nu mice. Once tumor volume reached 30 to 50 mm(3), animals were randomized and treated with vehicle alone or 150 mg/kg SKI-606 by daily oral gavage. Experimental animals receiving SKI-606 developed tumors of significantly smaller volume (45-54%) compared with control animals receiving vehicle alone. Analysis of lungs, liver, and spleen of these animals showed a significant decrease in GFP-positive tumor metastasis in animals receiving SKI-606 at a dose that was well tolerated. Western blot analysis and immunohistochemical analysis of primary tumors showed that these effects were due to the ability of SKI-606 to block tumor cell proliferation, angiogenesis, growth factor expression, and inhibition of Src-mediated signaling pathways in vivo. Together, the results from these studies provide compelling evidence for the role of Src inhibitors as therapeutic agents for blocking breast cancer growth and metastasis.

A non–RGD-based integrin binding peptide (ATN-161) blocks breast cancer growth and metastasis in vivo

Purpose: Integrins are expressed by numerous tumor types including breast cancer, in which they play a crucial role in tumor growth and metastasis. In this study, we evaluated the ability of ATN-161 (Ac-PHSCN-NH2), a 5-mer capped peptide derived from the synergy region of fibronectin that binds to α5β1 and αvβ3 in vitro, to block breast cancer growth and metastasis. Experimental design: MDA-MB-231 human breast cancer cells were inoculated s.c. in the right flank, or cells transfected with green fluorescent protein (MDA-MB-231-GFP) were inoculated into the left ventricle of female BALB/c nu/nu mice, resulting in the development of skeletal metastasis. Animals were treated with vehicle alone or by i.v. infusion with ATN-161 (0.05–1 mg/kg thrice a week) for 10 weeks. Tumor volume was determined at weekly intervals and tumor metastasis was evaluated by X-ray, microcomputed tomography, and histology. Tumors were harvested for histologic evaluation. Result: Treatment with ATN-161 caused a significant dose-dependent decrease in tumor volume and either completely blocked or caused a marked decrease in the incidence and number of skeletal as well as soft tissue metastases. This was confirmed histologically as well as radiographically using X-ray and microcomputed tomography. Treatment with ATN-161 resulted in a significant decrease in the expression of phosphorylated mitogen-activated protein kinase, microvessel density, and cell proliferation in tumors grown in vivo. Conclusion: These studies show that ATN-161 can block breast cancer growth and metastasis, and provides a rationale for the clinical development of ATN-161 for the treatment of breast cancer. [Mol Cancer Ther 2006;5(9):2271–80]

A peptide derived from the nonreceptor binding region of urokinase plasminogen activator (uPA) inhibits tumor progression and angiogenesis and induces tumor cell death in vivo

Urokinase plasminogen activator (uPA) plays an important role in the progression of several malignancies including breast cancer. We have identified a noncompetitive antagonist of the uPA‐uPAR interaction derived from a nonreceptor binding region of uPA (amino acids 136‐143). This 8‐mer capped peptide (Å6) inhibited breast cancer cell invasion and endothelial cell migration in a dose‐dependent manner in vitro without altering cell doubling time. Intraperitoneal administration of Å6 resulted in a significant inhibition of tumor growth and suppressed the development of lymph node metastases in several models of breast cancer cell growth and metastasis. Large areas of tumor necrosis and extensive positive staining by TUNEL were observed on histological and immunohistochemical analysis of experimental tumor sections from Å6‐treated animals. Å6 treatment also resulted in a decrease in factor VIII‐positive tumor microvessel hot‐spots. These results identify a new epitope in uPA that is involved in the uPA‐uPAR interaction and indicate that an antagonist based on this epitope is able to inhibit tumor progression by modulating the tumor microenvironment in the absence of direct cytotoxic effects in vivo.—Guo, Y., Higazi, A. A., Arakelian, A., Sachais, B. S., Cines, D., Goldfarb, R. H., Jones, T. R., Kwaan, H., Mazar, A. P., Rabbani, S. A. A peptide derived from the nonreceptor binding region of urokinase plasminogen activator (uPA) inhibits tumor progression and angiogenesis and induces tumor cell death in vivo. FASEB J. 14, 1400–1410 (2000)

Regulation of DNA Methylation in Human Breast Cancer EFFECT ON THE UROKINASE-TYPE PLASMINOGEN ACTIVATOR GENE PRODUCTION AND TUMOR INVASION

Urokinase-type plasminogen activator (uPA) is a member of the serine protease family and can break down various components of the extracellular matrix to promote growth, invasion, and metastasis of several malignancies including breast cancer. In the current study we examined the role that the DNA methylation machinery might be playing in regulating differential uPA gene expression in breast cancer cell lines. uPA mRNA is expressed in the highly invasive, hormone-insensitive human breast cancer cell line MDA-MB-231 but not in hormone-responsive cell line MCF-7. Using methylation-sensitive PCR, we show that 90% of CpG dinucleotides in the uPA promoter are methylated in MCF-7 cells, whereas fully demethylated CpGs were detected in MDA-MB-231 cells. uPA promoter activity, which is directly regulated by the Ets-1 transcription factor, is inhibited by methylation as determined by uPA promoter-luciferase reporter assays. We then tested whether the state of expression and methylation of the uPA promoter correlates with the global level of DNA methyltransferase and demethylase activities in these cell lines. We show that maintenance DNA methyltransferase activity is significantly higher in MCF-7 cells than in MDA-MB-231 cells, whereas demethylase activity is higher in MDA-MB-231 cells. We suggest that the combination of increased DNA methyltransferase activity with reduced demethylase activity contributes to the methylation and silencing of uPA expression in MCF-7 cells. The converse is true in MDA-MB-231 cells, which represents a late stage highly invasive breast cancer. The histone deacetylase inhibitor, Trichostatin A, induces the expression of the uPA gene in MDA-MB-231 cells but not in MCF-7 cells. This supports the hypothesis that DNA methylation is the dominant mechanism involved in the silencing of uPA gene expression. Taken together, these results provide insight into the mechanism regulating the transcription of the uPA gene in the complex multistep process of breast cancer progression.

Overexpression of urokinase receptor in breast cancer cells results in increased tumor invasion, growth and metastasis.

We have examined the role of urokinase receptor (uPAR) in tumor invasion and metastasis by developing a homologous model of uPAR overexpression in a rat breast cancer cell line (Mat B III) using gene transfer technique. Control (pRc‐CMV) and experimental plasmid (pRc‐uPAR‐S) were transfected into Mat B III cells by using Lipofectin reagent. Levels of uPAR production were accessed by Northern blotting, immunofluorescence, receptor binding and ELISA. At least 3 experimental clones (pRc‐uPAR‐S), expressing 3‐ to 5‐fold higher levels of uPAR than control (pRc‐CMV), were selected for further analysis. Experimental cells overexpressing uPAR showed a 4‐ to 5‐fold higher invasive capacity compared with control cells in a Boyden chamber invasion assay. Both control and experimental cells (1 × 106 cells) were injected into the mammary fat pad of syngeneic female Fischer rats. Animals were sacrificed at timed intervals and evaluated for the development of tumor growth and metastasis. Animals receiving cells overexpressing uPAR had significantly larger tumor volume and weight throughout our study. Furthermore, due to increased uPAR expression, experimental animals developed large metastatic lesions in liver, spleen and lymph nodes. Our results therefore demonstrate the role of uPAR in tumor progression, due to its ability to localize uPA within the tumor cell milieu.

A vitamin D analogue (EB1089) inhibits parathyroid hormone-related peptide production and prevents the development of malignancy-associated hypercalcemia in vivo.

We have examined the effects of 1,25 dihydroxyvitamin D3 (1,25[OH]2D3) and a low calcemic analogue EB1089 on parathyroid hormone-related peptide (PTHRP) production and on the development of hypercalcemia in Fischer rats implanted with the Leydig cell tumor H-500. Leydig cell tumors were implanted subcutaneously into male Fischer rats, which received constant infusions intraperitoneally of either 1,25(OH)2D3 (50-200 pmol/24 h), EB1089 (50-400 pmol/24 h), or vehicle for up to 4 wk. A control group of animals received similar infusions without tumor implantation. Plasma calcium, plasma levels of immunoreactive iPTHRP, and tumor PTHRP mRNA levels were determined as well as tumor size, animal body weight, and animal survival time. Non-tumor-bearing animals receiving > 50 pmol/24 h of 1,25(OH)2D3 became hypercalcemic, whereas no significant change in plasma calcium was observed in animals receiving < or = 200 pmol/24 h of EB1089. Tumor-bearing animals receiving vehicle alone or > 50 pmol/24 h of 1,25(OH)2D3 became severely hypercalcemic within 15 d. However, animals treated with low dose 1,25(OH)2D3 and all doses of EB1089 maintained near-normal or normal levels of plasma calcium for up to 4 wk. Additionally, reduced levels of tumor PTHRP mRNA and of plasma iPTHRP were observed compared with controls in both vitamin D- and EB1089-treated rats. Infusion of 50 pmol/24 h of 1,25(OH)2D3 and 200 pmol/24 h of EB1089 significantly reduced tumor volume by the end of experiment. The analogue but not 1,25(OH)2D3 substantially prolonged survival time in tumor-bearing animals with longer survival achieved at the highest dose, 400 pmol/24 h, of EB1089. These studies demonstrate that 1,25(OH)2D3 and a low calcemic vitamin D analogue are potent inhibitors of PTHRP production in vivo. Low calcemic analogues may therefore represent important alternative therapy for malignancy-associated hypercalcemia.

Methylation status of uPA promoter as a molecular mechanism regulating prostate cancer invasion and growth in vitro and in vivo

Urokinase plasminogen activator (uPA) promotes tumor invasion and metastasis in several malignancies including prostate cancer, one of the most commonly detected male cancers that result in a high incidence of mortality. In the present study we have examined the differential regulation of uPA gene expression in different stages of prostate cancer by DNA methylation. We determined levels of uPA expression in normal prostate epithelial cells (PrEC) and in hormone‐responsive (LNCaP) and ‐insensitive (PC‐3) prostate cancer cell lines. We found that uPA is expressed only in the highly invasive PC‐3 cells where the uPA promoter is unmethylated. The lack of uPA expression in PrEC and LNCaP cells, where uPA promoter is highly methylated, is due to suppression of uPA gene transcription by DNA methylation. Treatment of LN‐CaP cells with 5′‐azacytidine, a potent demethylating agent, resulted in induction of uPA mRNA expression, uPA activity, and higher invasive capacity in vitro. Additionally, a marked increase in tumor volume was observed after inoculation of these cells into the flank of male BALB/c (nu/nu) mice. Collectively these studies have demonstrated that DNA methylation is the underlying molecular mechanism responsible for uPA gene silencing in normal and early stages of prostate cancer, which has a direct effect on tumor cell invasion and growth in vitro and in vivo.—Pakneshan, P., Xing, R. M., Rabbani, S. A. Methylation status of uPA promoter as a molecular mechanism regulating prostate cancer invasion and growth in vitro and in vivo.—Pakneshan, P., Xing, R. M., Rabbani, S. A. Methylation status of uPA promoter as a molecular mechanism regulating prostate cancer invasion and growth in vitro and in vivo. FASEB J. 17, 1081–1088 (2003)

Over-production of parathyroid hormone-related peptide results in increased osteolytic skeletal metastasis by prostate cancer cells in vivo.

Prostate carcinoma is one of the most common malignancies affecting males, resulting in a high rate of morbidity and mortality. This hormone‐dependent malignancy is characteristically associated with a high incidence of osteoblastic skeletal lesions. However, osteolytic lesions invariably accompany blastic ones. In the current study, we assessed the role of parathyroid hormone–related peptide (PTHRP), a potent bone‐resorbing agent, in contributing to bone breakdown and prostatic skeletal metastasis using a syngeneic rat prostate cancer model. The full‐length cDNA encoding rat PTHRP was subcloned as a Hind III insert in the sense orientation into the mammalian expression vector pRc‐CMV to generate the expression vector pRc‐PTHRP‐S. Both control and experimental plasmids were stably transfected into low PTHRP‐producing Dunning R3227, Mat Ly Lu rat prostate cancer cells. Following antibiotic selection, monoclonal cell lines expressing the highest amount of PTHRP mRNA and immunoreactive PTHRP were selected as experimental tumor cells for further analysis. Increased PTHRP production by these cells had no significant effect in vitro on the invasive capacity of these cells. Control and experimental cells were inoculated s.c. into the right flank or by the intracardiac (i.c.) route into the left ventricle of inbred male Copenhagen rats. No skeletal metastases occurred after s.c. injection with either cells. In contrast, i.c. inoculation led to lumbar vertebra metastasis and consequent hind‐limb paralysis. Furthermore, histological examination of skeletal metastases in experimental animals showed a marked increase in osteoclastic activity. Our results demonstrate that PTHRP can increase osteoclastic osteolysis in the presence of focal osseous prostate cancer metastases and may contribute to the lytic lesions which generally accompany osteoblastic lesions in prostate cancer. Int. J. Cancer 80:257–264, 1999.