The location of acidic fibroblast growth factor in the breast is dependent on the activity of proteases present in breast cancer tissue

Abstract

Summary Acidic fibroblast growth factor (FGF1) and two of its receptors, FGFR1 and FGFR4, were localized in cryostat sections of normal, benign and malignant human breast tissue by immunohistochemistry. Without pretreatment, FGF1 staining was mainly seen in normal epithelial cells. However, polymerase chain reaction (PCR) analysis and immunoblotting of isolated normal epithelial and myoepithelial cells showed FGF1 mRNA and protein to be present in both cell types. Following incubation of frozen sections at 370C in phosphate-buffered saline, FGF1 staining was also revealed in myoepithelial cells and basement membrane adjacent to carcinoma cells. Treatment with protease inhibitors demonstrated that this effect was due to the activity of an endogenous protease. In contrast, FGF1 staining was found to be associated with the stroma adjacent to malignant cells only in the presence of protease inhibitors. FGFR1 and FGFR4 immunostaining was localized to both normal and malignant epithelial cells and to a lesser extent to myoepithelial cells. There was no difference in the staining intensity for the FGF receptors between normal and cancer samples. The change in location of FGF1 between normal and malignant tissues and the sensitivity of stored FGF1 to the action of endogenous proteases raises the possibility of both autocrine and paracrine roles for FGF1 in the normal and malignant human breast.Keywords: breast cancer; fibroblast growth factor 1; protease; immunohistochemistry Fibroblast growth factor 1 (FGF1) belongs to a family of multifunctional polypeptides that are involved in a wide array of biological processes, which include cellular proliferation and differentiation, angiogenesis, chemotaxis, embryonal development and tissue repair (Basilico and Moscatelli, 1992). To date, the FGFs consist of a family of nine homologous polypeptide growth factors that include FGF1 (acidic FGF), FGF2 (basic FGF), FGF3 (int-2), FGF4 (hst-l/Kaposi FGF), FGF5, FGF6 (hst-2), FGF7 (keratinocyte growth factor), FGF8 (androgen-induced growth factor) and FGF9 (glial-activating factor) (Basilico and Moscatelli, 1992;Tanaka et al, 1992;Miyamoto et al, 1993). These proteins share 35-50% overall homology of their amino acid sequences (Basilico and Moscatelli, 1992;Givol and Yayon, 1992).Unlike other members of the family, FGF1, FGF2 and FGF9 are synthesized without a signal peptide sequence and thus may remain sequestered in the cell (Basilico and Moscatelli, 1992;Cao and Pettersson, 1993). However, release of FGF may occur through leakage from damaged cells or from viable cells via a novel mechanism (Mignatti et al, 1992;Cao and Pettersson, 1993). Yeoman (1993) has postulated that proteoglycan-bound FGF may be released from the cell surface or extracellular matrix by the action of proteases, and Briozzo et al (1991) have shown that Received 10 June 1996 Revised 26 November 1996 Accepted 3 December 1996 Correspondence to: J Gomm MCF7 breast cancer cells secrete cathepsin D, which is able to digest the extracellular matrix and releas...

Increased expression of fibroblast growth factor 8 in human breast cancer

“…Previous work has shown that FGF1 and FGF2 are present in large amounts in the normal breast, implying roles for these growth factors in maintaining the structure of the normal ducts (Gomm et al, 1991Coope et al, 1997). In breast cancer, there is a decrease in the amount of FGF1 and FGF2 present in breast tissue (Bansal et al, 1995;Yiangou et al, 1997a).…”

“…In breast cancer, there is a decrease in the amount of FGF1 and FGF2 present in breast tissue (Bansal et al, 1995;Yiangou et al, 1997a). However, in the case of FGF1, there is evidence for some remaining in a more functionally available form in breast cancers (Smith et al, 1994;Coope et al, 1997). FGF7 is found in similar amount in both malignant and non-malignant breast tissue.…”

Fibroblast growth factor 8 is expressed at higher levels in lactating human breast and in breast cancer

“…All four of the FGFRs are expressed to some degree in breast cell lines (McLeskey et al, 1994;Johnston et al, 1995). Although amplification of the fgfr4 gene has been found in 10% of breast cancers, we have previously shown that equivalent levels of FGFR-4 are present in the epithelial cells of malignant and non-malignant breast sections (Jaakkola et al, 1993;Coope et al, 1997). In the case of FGFR-1, significant changes in the isoform of FGFR-1 expressed occur on malignant transformation although the level of expression appears to stay the same Yiangou et al, 1997b).…”

“…Previous work has shown that FGF1 and FGF2 are expressed in the normal breast, implying roles for these growth factors in maintaining the structure of the normal ducts (Gomm et al, 1991Coope et al, 1997). In breast cancer, there is a decrease in the amount of FGF1 and FGF2 present in breast tissue (Bansal et al, 1995;Yiangou et al, 1997a).…”

“…In breast cancer, there is a decrease in the amount of FGF1 and FGF2 present in breast tissue (Bansal et al, 1995;Yiangou et al, 1997a). However, in the case of FGF1, there is evidence for some remaining in a more functionally available form in breast cancers (Smith et al, 1994;Coope et al, 1997). FGF7 is found in similar amount in both malignant and nonmalignant breast tissues.…”