Macrophage-colony stimulating
factor (M-CSF)

Colony stimulating factor-1 (CSF-1)

Gene: CSF1 maps to 1p21-p13 (Saltman D.L. et al., 1992). It spans approximately 20 kb and contains 10 exons and 9 introns (Ladner M.B. et al., 1987).
mRNA: sizes: several mRNAs, from about 1.5 to 4.5 kb.
Protein: the glycoprotein M-CSF is a homodimer the subunits of which are linked by disulfide bonds. The sugar moiety is not required for the full spectrum of biological activities. At least two forms of M-CSF exist, with lengths of 256 (M-CSF-alpha) and 554 (M-CSF-beta) amino acids. M-CSF-beta is a secreted protein that does not occur in a membrane-bound form. M-CSF-alpha is expressed as an integral membrane protein that is slowly released by proteolytic cleavage. The membrane-bound form of M-CSF can interact with receptors on near-by cells and therefore mediates specific cell-to-cell contacts.

Cell lines:
- M-CSF increased invasiveness 6-fold (using a human amnionic basement membrane invasion model) in BT-20 breast cancer cells (BCC) induced by glucocorticoids to express high levels of M-CSF receptor (CSF-1R), in comparison to control cells not exposed to glucocorticoids or M-CSF. In contrast, M-CSF had no effect on invasion in the CSF-1R-negative MCF-7 BCC line (Filderman A.E. et al., 1992).

- In a series of 196 breast cancers (median age of the patients was 54 years, and median follow-up was 7.3 years), M-CSF was expressed significantly in 74% of the tumors and the M-CSF receptor (CSF-1R) in more than 50% of the tumors. Tumors with high percentages of M-CSF expressing cells also had marked monocyte infiltrates. The presence of marked CD45RO-positive (activated memory but noncytotoxic) T-cell infiltrates and apparent nuclear staining of M-CSF in tumor cells were associated with the more frequent occurrence of metastases and with poor survival (Scholl S.M. et al., 1994).

- Expression of a mutant Ets2 transcription factor in BT20 BCC completely inhibited the formation of soft agar colonies and abolished the M-CSF-stimulated invasion of these cells through a barrier of reconstituted basement membrane (Matrigel). The expression of this Ets2 mutant was capable of interrupting the M-CSF receptor (CSF-1R)-regulated intracellular signaling pathways by inhibiting M-CSF-induced c-myc, c-fos, and c-jun expression in BT20 BCC (Sapi E. et al., 1998).

Tumors:
- M-CSF was detected by immunohistochemical techniques (IHC) at the level of invasive breast cancer cells in 46/50 tumours but not at the level of in-situ (pre-invasive) cancer. A mosaic staining pattern was usually observed, with a very high expression in areas of obvious stromal invasion (90% cells positive) and absent or trace staining in intraductal carcinoma. Macrophages and plasma cells are equally intensely positive. In-situ hybridisation experiments confirm the production of M-CSF (mRNA) by tumour cells and show the same pattern of expression. Expression of the M-CSF receptor protein (fms) was also observed by IHC in 41/48 invasive tumours, albeit at weaker intensities than in tumour infiltrating monocytes/macrophages. A concomitant expression of both M-CSF and fms in in-situ carcinoma was never seen (n = 14). The associated expression of M-CSF and its receptor might be linked to the invasive potential of breast cancer, the monocytic infiltrate being an indication of the quantitative importance of M-CSF production by the tumour.(Tang R. et al., 1992).

- Serum samples from 118 primary breast cancer patients and 75 patients with metastatic disease were assayed by radio-immuno-assay (RIA) for circulating M-CSF. Mean serum levels were significantly higher in the metastatic population (9.7 ng/ml +/- 0.8) as compared to the patients with primary tumors (4.2 +/- 0.2). Patients with early stage tumors (T0/T1/T2) had significantly lower levels than patients with tumors of larger size (T3/T4). Relapse and survival statistics were analyzed using Kaplan-Meier estimates. Samples from 118 primary breast cancer patients were available to study. The median follow up was 85 months (range: 1-108). An elevated M-CSF concentration (> 6.6 ng/ml or > 550 Units/ml) was associated with a shorter disease free interval. In a multivariate analysis, including T (clinical tumor size), N (clinical node status), histological grade, and hormone receptor status, M-CSF remained significantly associated with a poorer outcome (relative risk of relapse: RR: 3.3 [1.3-8.5]), together with tumor size (RR: 2.8[1-8.2]) and clinically involved nodes (RR: 4.1[2.1-8]). These results were not modified following adjustment for type of treatment. We conclude that raised circulating M-CSF levels may be an indicator of early metastatic relapse (Scholl S.M. et al., 1996).

Filderman A.E. et al. (1992) Macrophage colony-stimulating factor (CSF-1) enhances invasiveness in CSF-1 receptor-positive carcinoma cell lines. Cancer Res. 52, 3661-3666.
Kawasaki E.S. et al. (1985) Molecular cloning of a complementary DNA encoding human macrophage-specific colony stimulating factor (CSF-1). Science 230, 291-296.
Ladner M.B. et al. (1987) Human CSF-1: gene structure and alternative splicing of mRNA precursors. EMBO J. 6, 2693-2698.
Morris S.W. et al. (1991) Reassignment of the human CSF1 gene to chromosome 1p13-p21. Blood 78, 2013-2020.
Saltman D.L. et al. (1992) Reassignment of the human macrophage colony stimulating factor gene to chromosome 1p13-21. Biochem. Biophys. Res. Commun. 182, 1139-1143.
Sapi E. et al. (1998) Ets-2 transdominant mutant abolishes anchorage-independent growth and macrophage colony-stimulating factor-stimulated invasion by BT20 breast carcinoma cells. Cancer Res. 58, 1027-1033.
Scholl S.M. et al. (1994) Anti-colony-stimulating factor-1 antibody staining in primary breast adenocarcinomas correlates with marked inflammatory cell infiltrates and prognosis. J. Natl. Cancer Inst. 86, 120-126.
Scholl S.M. et al. (1996) Circulating levels of the macrophage colony stimulating factor CSF-1 in primary and metastatic breast cancer patients. A pilot study. Breast Cancer Res. Treat. 39, 275-283.
Tang R. et al. (1992) M-CSF (monocyte colony stimulating factor) and M-CSF receptor expression by breast tumour cells: M-CSF mediated recruitment of tumour infiltrating monocytes? J. Cell Biochem. 50, 350-356.
Wong G.G. et al. (1987) Human CSF-1: molecular cloning and expression of 4-kb cDNA encoding the human urinary protein. Science 235, 1504-1508.