cathepsin-g and Osteolysis

IL-20 is a proinflammatory cytokine involved in rheumatoid arthritis, atherosclerosis, and stroke. However, little is known about its role in breast cancer. We explored the function of IL-20 in tumor growth and metastasis, as well as in clinical outcome. Tumor expression of IL-20 was assessed by immunohistochemical staining among 198 patients with invasive ductal carcinoma of the breast, using available clinical and survival data. IL-20 expression was associated with advanced tumor stage, greater tumor metastasis, and worse survival. Reverse transcription quantitative polymerase chain reaction showed that clinical breast tumor tissue expressed higher levels of IL-20 and its receptors than did nontumorous breast tissue. IL-20 was also highly expressed in breast cancer bone-metastasis tissue. In vitro, IL-20 upregulated matrix metalloproteinase-9, matrix metalloproteinase-12, cathepsin K, and cathepsin G, and enhanced proliferation and migration of breast cancer cells, which were inhibited by anti-IL-20 mAb 7E. In vivo, we generated murine models to evaluate the therapeutic potential of 7E, using luminescence intensity, radiological scans, and micro-computed tomography. 7E reduced tumor growth, suppressed bone colonization, diminished tumor-mediated osteolysis, and lessened bone density decrement in mice injected with breast cancer cells. In conclusion, our results suggest that IL-20 plays pivotal roles in the tumor progression of breast cancer. IL-20 expression in breast cancer tissue is associated with a poor clinical outcome. Anti-IL-20 mAb 7E suppressed bone colonization and decreased osteolytic bone lesions. Therefore, IL-20 may be a novel target in treating breast tumor-induced osteolysis.

Topics: Animals; Antibodies, Monoclonal; Bone and Bones; Bone Neoplasms; Breast; Breast Neoplasms; Carcinoma, Ductal, Breast; Cathepsin G; Cathepsin K; Cell Line, Tumor; Cell Movement; Cell Proliferation; Disease Progression; Female; Humans; Interleukins; Matrix Metalloproteinase 12; Matrix Metalloproteinase 9; Mice; Mice, Inbred BALB C; Neoplasm Metastasis; Osteolysis

Increased transforming growth factor-beta (TGF-beta) signaling has been observed at the tumor-bone interface of mammary tumor-induced osteolytic lesions despite no observed transcriptional up-regulation of TGF-beta. To this point, the mechanism for enhanced TGF-beta signaling remains unclear. The bulk of TGF-beta that is released at the tumor-bone interface is in an inactive form secondary to association with beta-latency-associated protein and latency TGF-beta binding protein. We hypothesized that the observed increase in TGF-beta signaling is due to increased cathepsin G-dependent, matrix metalloproteinase 9 (MMP9)-mediated activation of latent TGF-beta. MMP9 is capable of activating latent TGF-beta, and we observed that decreased production of MMP9 was associated with reduced TGF-beta signaling. Similar to TGF-beta, MMP9 is released in an inactive form and requires proteolytic activation. We showed that cathepsin G, which we have previously shown to be up-regulated at the tumor-bone interface, is capable of activating pro-MMP9. Inhibition of cathepsin G in vivo significantly reduced MMP9 activity, increased the ratio of latent TGF-beta to active TGF-beta, and reduced the level of TGF-beta signaling. Our proposed model based on these results is that cathepsin G is up-regulated through tumor-stromal interactions and activates pro-MMP9, active MMP9 cleaves and releases active TGF-beta, and active TGF-beta can then promote tumor growth and enhance osteoclast activation and subsequent bone resorption. Thus, for the first time, we have identified cathepsin G and MMP9 as proteases involved in enhanced TGF-beta signaling at the tumor-bone interface of mammary tumor-induced osteolytic lesions and have identified these proteases as potential therapeutic targets.

Topics: Animals; Bone and Bones; Bone Neoplasms; Cathepsin G; Enzyme Activation; Enzyme Precursors; Mammary Tumor Virus, Mouse; Matrix Metalloproteinase 2; Matrix Metalloproteinase 9; Mice; Oligonucleotides, Antisense; Osteolysis; RANK Ligand; Signal Transduction; Transforming Growth Factor beta

Breast cancer commonly causes osteolytic metastases in bone, a process that is dependent on tumor-stromal interaction. Proteases play an important role in modulating tumor-stromal interactions in a manner that favors tumor establishment and progression. Whereas several studies have examined the role of proteases in modulating the bone microenvironment, little is currently known about their role in tumor-bone interaction during osteolytic metastasis. In cancer-induced osteolytic lesions, cleavage of receptor activator of nuclear factor-kappaB ligand (RANKL) to a soluble version (sRANKL) is critical for widespread osteoclast activation. Using a mouse model that mimics osteolytic changes associated with breast cancer-induced bone metastases, we identified cathepsin G, cathepsin K, matrix metalloproteinase (MMP)-9, and MMP13 to be proteases that are up-regulated at the tumor-bone interface using comparative cDNA microarray analysis and quantitative reverse transcription-PCR. Moreover, we showed that cathepsin G is capable of shedding the extracellular domain of RANKL, generating active sRANKL that is capable of inducing differentiation and activation of osteoclast precursors. The major source of cathepsin G at the tumor-bone interface seems to be osteoclasts that up-regulate production of cathepsin G via interaction with tumor cells. Furthermore, we showed that in vitro osteoclastogenesis is reduced by inhibition of cathepsin G in a coculture model and that in vivo inhibition of cathepsin G reduces mammary tumor-induced osteolysis. Together, our data indicate that cathepsin G activity at the tumor-bone interface plays an important role in mammary tumor-induced osteolysis and suggest that cathepsin G is a potentially novel therapeutic target in the treatment of breast cancer bone metastasis.

Topics: Animals; Bone Neoplasms; Cathepsin G; Cathepsins; Cell Line, Tumor; Gene Expression Regulation, Neoplastic; Mammary Neoplasms, Animal; Matrix Metalloproteinase 13; Matrix Metalloproteinase 9; Mice; Mice, Inbred BALB C; Neoplasm Metastasis; Neoplasm Transplantation; NF-kappa B; Osteoclasts; Osteolysis; RANK Ligand; Serine Endopeptidases