Breast cancer cells induce osteoclast formation by stimulating host IL‐11 production and downregulating granulocyte/macrophage colony‐stimulating factor

Abstract

Breast cancer cells frequently metastasize to the skeleton, where they induce OCL formation and activity, resulting in extensive bone destruction. However, the mechanisms by which breast cancer cells mediate increased osteolysis remain unclear. To elucidate this point, we investigated how 3 human breast cancer cell lines, MDA-MB-231, MDA-MB-435 and MCF-7, induce OCL formation using a murine osteoblast-spleen cell coculture system and compared their effects with a human colorectal cancer cell line, HCT-15; a human lung cancer cell line, HT-1080; and a normal human breast cell line, HME. The breast cancer cell lines supported OCL formation only when osteoblasts were present in spleen cell cocultures, whilst the non-breast cancer cell lines and the normal breast cell line, HME, had no effect. Fractionation of BCCM by ultrafiltration established that osteoclastogenic activity was associated with factors having m.w. >3 kDa. Breast cancer cell lines produced primarily PTHrP, with lesser amounts of IL-6 , IL-11 and TNF-␣. The effect of BCCM on OCL formation in osteoblast-spleen cell cocultures was partially prevented by a neutralising antibody to human PTHrP and completely prevented by a neutralising antibody to either murine IL-11 or the murine IL-11 receptor; neutralising antibodies to human IL-6, IL-11 or TNF-␣ were without effect. BCCM or human PTHrP induced an increase in murine osteoblast IL-11 mRNA and protein production, effects that were prevented in the presence of a neutralising antibody to human PTHrP. The osteoclastogenic activity of IL-11 was mediated by enhancing osteoblast production of PGE 2 effects, which were abrogated by an inhibitor of cyclooxygenase. PGE 2 apparently enhanced OCL formation by downregulating GM-CSF production by spleen cells since recombinant murine GM-CSF inhibited OCL formation and a neutralising antibody to murine GM-CSF blocked these inhibitory effects. We conclude that breast cancer cells induce OCL formation by stimulating osteoblastic production of IL-11. The subsequent release of PGE 2 followed by inhibition of GM-CSF production by cells within the bone microenvironment plays an important part in mediating the effects of breast cancer cells on OCL formation and their resorptive activity. © 2004 Wiley-Liss, Inc. Key words: breast cancer cells; osteoclast formation; IL-11Breast cancer cells preferentially metastasize to bone and induce bone destruction. 1-3 Skeletal destruction by breast cancer cells is thus one of the most distressing hallmarks of advanced malignant disease, and 70% of women who die from breast cancer have bone metastases at autopsy. Upon infiltrating the skeleton, breast cancer cells grow and induce extensive bone destruction. The osteolytic lesions result in considerable morbidity, such as bone pain, hypercalcaemia, pathologic fracture and debilitating neurologic symptoms. Although current therapies control tumour progression in the breast tissue, patients die as a result of metastatic cancer. Therefore, treatment that prevents tumour cell-induced bone los...

Breast cancer bone metastasis mediated by the Smad tumor suppressor pathway

“…It is important to note that IL-11 (and CTGF) can only be considered candidate bone metastasis genes at present. IL-11 is known to stimulate osteoclastic bone resorption in vitro (27)(28)(29), but it has complex effects on bone formation, including positive effects (37). Its role as a mediator of bone metastasis in humans remains to be established.…”

“…We recently identified a set of genes that mediate osteolytic bone metastasis by MDA-MB-231 cells (17). Among these genes, IL-11 was of interest because it has been proposed to play a role in osteoclast differentiation (27) and as a mediator of osteolysis in breast cancer bone metastasis (28,29). Enforced expression of IL-11 in MDA-MB-231 cells increases their bone-metastatic activity (17).…”

The binding characteristics of a cyclic nonapeptide, c(CGRRAGGSC), in LNCaP human prostate cancer cells

“…A number of studies proved that IL-11, as a cytokine with multi-biological effects, when specifically bound with the α-chain of its receptor, becomes a complex with high affinity for the intermembrane signal transduction glycoprotein 130. The complex activates the Jak-STAT signal pathway and facilitates the phosphorylation of p-hydroxyphenylalanine kinase, thus exerting related biological effects (6,13,14). Using phage display peptide library screening technology, it was revealed that the nonapeptide c(CGRRAGGSC), as an analog of IL-11, is able to specificically target to the prostate tumor.…”

COX-2 involvement in breast cancer metastasis to bone

“…We chose to investigate the effect of COX-2 in breast cancer metastasis to bone because (1) COX-2 is expressed in poor-prognosis human breast cancers including those overexpressing HER2 and (2) studies with cell lines and mouse models indicate that COX-2 overexpression in breast cancer cells inhibits apoptosis of breast cancer cells and promotes metastasis (Liu et al, 2001;Basu et al, 2004;Singh et al, 2005). Other in vitro studies have shown that breast cancer cells can stimulate osteoblasts and stromal cells to produce PGE 2 , which in turn induces osteoclastogenesis thus causing osteolytic bone metastasis (Ono et al, 2002;Morgan et al, 2004). Our cumulative evidence for the role of COX-2 in bone metastasis is based upon: (1) increased bone metastasis upon COX-2 transfection of breast cancer cells (Figure 1), (2) inhibition of bone metastasis (in both prevention and treatment regimens) by MFtricyclic (Figures 3 and 4) and (3) demonstration that BSCs of breast cancer cells produce higher levels of PGE 2 than the parental cell population (Figure 2), perhaps reflecting that PGE 2 confers an advantage on breast cancer cells for bone metastasis.…”