Secretion of MCP-1 and other paracrine factors in a novel tumor-bone coculture model

BackgroundThe bone-tumor microenvironment encompasses unique interactions between the normal cells of the bone and marrow cavity and the malignant cells from a primary or metastasized cancer. A multitude of paracrine factors within this microenvironment such as the growth factor, TGF-beta, and the chemokine, MCP-1, are secreted by many of these cell types. These factors can act in concert to modulate normal and malignant cell proliferation, malignant cell migration and invasion and, often, mediate bone cancer pain. Although many valuable in vitro and in vivo models exist, identifying the relevant paracrine factors and deciphering their interactions is still a challenge. The aim of our study is to test an ex vivo coculture model that will allow monitoring of the expression, release and regulation of paracrine factors during interactions of an intact femur explant and tumor cells.MethodsIntact or marrow-depleted neonatal mouse femurs and select murine and human sarcoma or carcinoma cell lines were incubated singly or in coculture in specialized well plates. Viability of the bone and cells was determined by immunohistochemical stains, microscopy and marrow cytopreps. Secretion and mRNA expression of paracrine factors was quantitated by ELISA and real-time RT-PCR.ResultsCompartments of the bone were optimally viable for up to 48 h in culture and tumor cells for up to 4 days. Bone was the major contributor of TGF-beta and MMP2 whereas both bone and sarcoma cells secreted the chemokine MCP-1 in cocultures. Synergistic interaction between the femur and sarcoma resulted in enhanced MCP-1 secretion and expression in cocultures and was dependent on the presence of the hematopoietic component of the bone as well as other bone cells. In contrast, coculturing with breast carcinoma cells resulted in reduction of TGF-beta and MCP-1 secretion from the bone.ConclusionThese studies illustrate the feasibility of this model to examine paracrine interactions between intact bone and tumor cells. Further study of unique regulation of MCP-1 secretion and signaling between these cell types in different types of cancer will be possible using this simulated microenvironment

β3-Integrin Expression on Tumor Cells Inhibits Tumor Progression, Reduces Metastasis, and Is Associated with a Favorable Prognosis in Patients with Ovarian Cancer

The role of the vitronectin receptor (αvβ3-integrin) as a tumor promoter seems well established, and, consequently, therapies that block this integrin are currently in clinical testing. We undertook the current study to determine whether αvβ3-integrin is an appropriate target in ovarian cancer treatment. Expression of β3-integrin in SKOV3ip1 ovarian cancer cells led to the overexpression of αvβ3-integrin on the cell surface and increased adhesion. However, αvβ3-integrin-overexpressing cells showed impaired invasion, protease expression, and colony formation. These results were recapitulated in xenograft studies: αvβ3-integrin-expressing cells showed increased adhesion to mouse peritoneum, but the overall number of metastatic nodules (105 versus 68 tumors) and tumor weight were significantly lower than those in the parental SKOV3ip1 cells. The αvβ3-integrin-overexpressing cells had a decreased proliferation rate mediated by inhibition of cyclin B1 and induction of phospho-Cdc2 and p53 expression, consistent with a G2M cell cycle arrest. Confirming the above results, inhibition of β3-integrin in cultured or primary OvCa cells decreased adhesion but increased invasion and proliferation. Patients with tumors expressing high β3-integrin had significantly better disease-free and overall survival (52 months versus 27 months, P < 0.05). This study shows that αvβ3-integrin expression on tumor cells actually slows tumor progression and acts as a tumor suppressor. Therefore, the vitronectin receptor might not be an appropriate therapeutic target in ovarian cancer