Human tumour-associated macrophages are capable of bone resorption.

Na Athanasou,Jmw Quinn

doi:10.1038/bjc.1992.108

Abstract

Cellular mechanisms of bone resorption associated with skeletal metastasis are poorly understood. Human tumour-associated macrophages (TAMs) isolated from primary lung carcinomas were incubated on bone slices where they formed resorption lacunae after 14 days co-culture with a mouse marrow-derived stromal cell line (ST2) with added 1 alpha, 25-dihydroxy Vitamin D3 and dexamethasone. These co-cultures were associated with the formation of increased numbers of tartrate resistant acid phosphatase positive mononuclear and multinucleated cells. Similar cocultures of ST2 cells with normal alveolar macrophages did not result in lacunar resorption. Both in the presence and absence of ST2 cells, TAMs and normal alveolar macrophages produced roughening of the bone surface with exposure of mineralised collagen fibres. TAMs are capable of both low-grade surface resorption and high-grade lacunar resorption of bone, and a specific interaction with stromal cells is necessary for the latter to occur. TAMs may thus directly contribute to the bone resorption associated with skeletal metastasis.

Highlights

Adherent mononuclear cells cultured on coverslips in the absence of ST2 cells were identified after 2 h and 24 h in culture as macrophages (TAMs) on the basis that they were acid phosphatase positive, TRAP negative, expressed monocyte/macrophage markers CD14 and CD68 and were negative for cytokeratins
Isolated tumour-associated macrophages (TAMs) co-cultured with ST2 cells showed more marked staining and earlier development of TRAP positivity with formation of a few small, relatively well-defined clusters of TRAP positive mononuclear cells which first appeared at about day 5 (Figure 1)
This study has shown that TAMs are capable of bone resorption

Summary

Methods

TAMs were isolated from five pneumoonectomy specimens for lung carcinoma (three adenocarcinomas; two squamous carcinomas) by collagenase digestion and substrate adherence from 2 x 2 x 2 cm portion of tumour (McGee & Myrvik, 1981), and alveolar macrophages (AMs) from equal portions of lung uninvolved by tumour (Haskill, 1981). TAM or AM-containing cell suspensions in alpha minimal essential medium plus 10% foetal calf serum (Gibco) (MEM/FCS) were added to 6mm wells (500cells/well) containing either bone slices or glass coverslips, half of which had been seeded (1,000 cells/well) 24 h earlier with the mouse marrow stromal cell line ST2 (Riken cell bank, Japan) (Athanasou et al, 1989). Dexamethasone (Sigma, UK) (10-7 M) and 1,25 dihydroxy Vitamin D3 (Roche, UK) (10-8 M) were added at the beginning of co-cultures with ST2 cells and at each change of medium (every 3 days). Adherent cells on bone slices were cultured for 24 h, 3, 7 and 14 days after which evidence of bone resorption was sought by scanning electron microscopy (SEM) (Chambers et al, 1984). Received September 1991; and in revised form December 1991

Results

Discussion

Conclusion