Growth-stimulatory effects of androgen, high concentration of glucocorticoid or fibroblast growth factors on a cloned cell line from Shionogi carcinoma 115 cells in a serum-free medium

New Insights in the Interaction of FGF/FGFR and Steroid Receptor Signaling in Breast Cancer

Luminal breast cancer (BrCa) has a favorable prognosis compared with other tumor subtypes. However, with time, tumors may evolve and lead to disease progression; thus, there is a great interest in unraveling the mechanisms that drive tumor metastasis and endocrine resistance. In this review, we focus on one of the many pathways that have been involved in tumor progression, the fibroblast growth factor/fibroblast growth factor receptor (FGFR) axis. We emphasize in data obtained from in vivo experimental models that we believe that in luminal BrCa, tumor growth relies in a crosstalk with the stromal tissue. We revisited the studies that illustrate the interaction between hormone receptors and FGFR. We also highlight the most frequent alterations found in BrCa cell lines and provide a short review on the trials that use FGFR inhibitors in combination with endocrine therapies. Analysis of these data suggests there are many players involved in this pathway that might be also targeted to decrease FGF signaling, in addition to specific FGFR inhibitors that may be exploited to increase their efficacy.

Androgen inducibility ofFgf8 in Shionogi carcinoma 115 cells correlates with an adjacent t(5;19) translocation

Fgf8 (fibroblast growth factor 8) was initially cloned from a mouse mammary tumor cell line derived from the androgen-dependent Shionogi carcinoma 115. The androgen-inducible expression of Fgf8 in this tumor controls its androgen-dependent phenotype, thus stimulating interest in this gene as a possible factor in human prostate cancer and other androgen-sensitive cancers. However, apart from Shionogi carcinoma 115, the androgen inducibility of Fgf8 is controversial. In the present study, having not detected androgen-inducible expression of Fgf8 in other mouse mammary cell lines or mouse prostate, we examined the Shionogi carcinoma 115-derived S115 cell line for mouse mammary tumor virus (MMTV) insertions or other nearby DNA rearrangements that might explain the androgen inducibility of Fgf8 in these cells. Southern blotting did not detect MMTV insertions near Fgf8 but did reveal a specific DNA rearrangement 3.7 kb upstream of Fgf8 in S115 cells and in other cells (SC115) independently derived from Shionogi carcinoma 115. Spectral karyotyping of S115 cells and sequencing of the cloned rearrangement junctions indicate that Fgf8 is involved in a t(5;19) translocation. The chromosome 5 sequence joined to Fgf8 is immediately adjacent to Smr2 (submaxillary gland androgen-regulated protein 2) and includes Muc10 (mucin 10), two genes that we show are testosterone inducible in S115 cells, suggesting that the androgen-dependent expression of Fgf8 in Shionogi carcinoma 115 and derivative cells results from this translocation. Together, these results suggest that androgen inducibility is not an inherent property of the Fgf8 gene, which has implications regarding this gene's proposed role in the etiology of hormone-responsive cancers.

Sulfated derivatives of Escherichia coli K5 polysaccharides as modulators of fibroblast growth factor signaling

Heparan sulfate (HS) proteoglycans are intimately involved in the regulation of fibroblast growth factor (FGF) signaling. HS and the related glycosaminoglycan heparin interact with FGFs and FGF receptors (FGFRs), and it is believed that both interactions are required for productive FGF signaling. Attempts to inhibit FGF activity have been made with modified heparin preparations, various heparin-like polysaccharide analogues and other polyanionic molecules, which may all act by interfering with the physiological HS-FGF-FGFR interactions on the cell surface. Here, we have studied the potential of sulfated derivatives of a bacterial polysaccharide (capsular polysaccharide from Escherichia coli K5 (K5PS)) in the modulation of FGF-heparin/HS interactions and FGF signaling. We demonstrate that O-sulfated and N,O-sulfated species of K5PS, with high degrees of sulfation, displaced FGF-1, FGF-2, and FGF-8b from heparin. However, only O-sulfated K5PS efficiently inhibited the FGF-induced proliferation of S115 mammary carcinoma cells and 3T3 fibroblasts, whereas N,O-sulfated K5PS had little or no inhibitory effect. Studies with CHO677 cells lacking endogenous HS, as well as with chlorate-treated S115 cells expressing undersulfated HS, indicated that whereas exogenously administered heparin and N,O-sulfated K5PS restored the cellular response toward FGF stimulation, O-sulfated K5PS was largely devoid of such stimulatory activity. Our data suggest that highly O-sulfated species of K5PS may be efficient inhibitors of FGF signaling.

Testosterone-induced growth of S115 mouse mammary tumor cells is dependent on heparan sulfate

The androgen-induced proliferation of S115 mouse mammary tumor cells has been suggested to involve autocrinic fibroblast growth factor signaling. Heparan sulfate proteoglycans are required for fibroblast growth factor signaling, presumably due to their ability to alter binding of fibroblast growth factors to their receptors. We have investigated the role of heparan sulfate proteoglycans in the testosterone-induced proliferation of S115 cells. We demonstrate that when the cells are treated with sodium chlorate, which inhibits the sulfation of endogenous heparan sulfate proteoglycans, cell growth becomes dependent on exogenous heparin. The shortest heparin oligosaccharides supporting cell growth were octasaccharides, whereas dodecasaccharides were almost as effective as native heparin. The N-, 2-O-, and 6-O-sulfate groups of heparin were all required for full testosterone response. Treatment of S115 cells with chlorate or testosterone did not alter the expression of fibroblast growth factor receptors 1 or 3, whereas the expression of fibroblast growth factor receptor 2 was down-regulated. We have previously shown that overexpression of syndecan-1 heparan sulfate proteoglycan renders S115 cells insensitive to testosterone and now demonstrate that this effect can be overcome by sodium chlorate treatment in combination with exogenous heparin. Our results suggest that heparin-like molecules are intimately involved in the androgen-mediated proliferation of S115 cells.

Effect of social housing condition on heat shock protein (HSP) expression in the Shionogi mouse mammary carcinoma (SC115)

Our previous studies have shown that social housing conditions can significantly alter the growth rate of the Shionogi mouse mammary carcinoma (SC115). The present study extended our investigations to the molecular level by examining stressor effects on the expression of a group of stress-responsive proteins, the heat shock proteins (HSPs). We hypothesized that HSP expression in SC115 cells may be altered by (a) different social housing conditions in vivo and (b) steroid hormone and growth factor exposure in vitro. Mice were reared in groups (G) or as individuals (I). Immediately following tumor cell injection, mice were rehoused from group to individual (GI), from individual to group (IG), or they remained in groups (GG). Tumor tissue was resected at 0.8 g or 3.0 g, as evidence suggests that tumor size affects HSP expression, which in turn affects proliferation. The data demonstrate that expression of HSP25, 70, and 90 was increased in tumors from mice in the IG compared to GG and GI mice, at both tumor weights examined. In addition, in IG mice, HSP90 expression was greater in 0.8 g compared to 3.0 g tumors. Under controlled culture conditions, hormones known to stimulate SC115 growth both in vivo and in vitro altered HSP expression. Physiological levels of dihydrotestosterone (DHT) and pharmacological levels of hydrocortisone (HC) upregulated expression of HSP25, whereas physiological levels of beta-estradiol (E2) upregulated expression of HSP90. These data are the first to demonstrate that a psychosocial stressor, a change in social housing condition, can induce differential HSP expression. Further, these data show that hormones that regulate SC115 tumor growth, also alter HSP expression.

Psychosocial stressors and mammary tumor growth: an animal model

Stressful life events and the ability to cope with stress may play a role in the progression of breast cancer; however, the complex relationship between stressors and tumor growth is difficult to investigate in humans. Our studies have utilized the androgen-responsive Shionogi mouse mammary carcinoma (AR SC115) in male mice to investigate the effects of social housing condition on tumor growth rates and responses to chemotherapy. We demonstrate that, depending on social housing condition, mammary tumor growth and response to chemotherapy can both increase and decrease. We have examined the possible role(s) of 1) psychosocial variables, 2) testosterone and corticosterone, hormones altered by stress and known to stimulate SC115 cells in vivo and in vitro, 3) NK cells, one of the body's first lines of defense against tumor cells, 4) stress proteins, in mediating the differential tumor growth rates observed in our model. This review discusses the investigations we have undertaken to elucidate the mechanisms through which a psychosocial stressor, social housing condition, can alter tumor growth rate.

Molecular mechanism of androgen-dependent growth in transformed cells. Pathway from basic science to clinical application

Shionogi carcinoma 115 (SC 115) has been extensively used to analyze the mechanism of androgen-dependent cancer growth. This tumor exhibits marked androgen-dependent growth in vivo and one cell line whose growth is markedly stimulated by androgen in serum-free culture condition is isolated from SC 115 tumor. This androgen-dependent growth is mediated through an induction of heparin binding growth factor termed as androgen-induced growth factor (AIGF). In addition, fibroblast growth factor receptor 1 (FGFR 1) is identified as a receptor for AIGF. The expression of FGFR 1 mRNA is up-regulated by androgen in SC 115 cells, indicating that this androgen-inducible autocrine loop is potentiated at two sites by androgen. An androgen-independent cell line is also established from this androgen-dependent SC 115 tumor. The growth of these androgen-independent cells is stimulated by AIGF, indicating that AIGF acts not only as an autocrine growth factor to androgen-dependent cells but also as a paracrine growth factor to androgen-independent cells. In addition, transfection of AIGF expression vector into androgen-dependent cells results in a facilitation of conversion from androgen-dependent to -independent phenotype. Thus, AIGF might play a role from tumor progression. These results indicate that a blockade of AIGF activity is an important therapeutic target. Actually, some compounds such as heparin and suramin are found to inhibit this androgen-induced autocrine loop. These basic observations will be discussed in relation to their possible clinical application.

Progression to steroid autonomy is accompanied by altered sensitivity to growth factors in S115 mouse mammary tumour cells

Progression to steroid autonomy is a major clinical problem in the treatment of steroid-sensitive tumours. Molecular mechanisms remain unknown but recent hypotheses imply a role for growth factors in this progression. Since S115 + A androgen-responsive mouse mammary tumour cells provide a model system to study this phenomenon in vitro, we have used this model to investigate growth factor gene expression and sensitivity during progression from a steroid sensitive to insensitive state. S115 + A androgen-responsive cells showed a positive proliferative response, morphological response and increased saturation density to various forms of fibroblast growth factor (FGF) and transforming growth factor beta (TGF beta) in both monolayer and suspension culture. A marked synergy was noted, however, between FGF and TGF beta in promoting growth in suspension culture. S115 + A cells possessed mRNA for both acidic FGF (aFGF) and TGF beta 1, both of which were increased by testosterone. Progression to androgen insensitivity was associated with a reversal of growth factor response such that all growth factor responses became generally inhibitory on growth of the unresponsive cells but with a particularly striking synergistic action between FGF and TGF beta 1 on inhibition of both monolayer and suspension growth. Levels of aFGF and TGF beta 1 mRNAs remained low in steroid-insensitive S115-A cells, indicating that loss of response was not associated with any constitutive upregulation of endogenous production of one of these growth factors. The scientific and clinical implications are discussed.

Thyroid hormone inhibits androgen-enhanced DNA synthesis in Shionogi carcinoma 115 cells without affecting autocrine growth factor mRNA expression

The growth of the mouse mammary Shionogi carcinoma 115 (SC 115)-derived cell line (SC-3) is markedly stimulated by androgen through induction of a heparin-binding growth factor termed androgen-induced growth factor (AIGF). This androgen-induced growth is partly blocked by thyroid hormone(s) such as triiodothyronine (T3). Transforming growth factor beta 1 (TGF beta 1) also inhibits the growth of SC-3 cells. Thus, we have investigated the possibility that T3 exerts its inhibitory effects on SC-3 cell growth through an alteration in AIGF or TGF beta 1 mRNA expression. Unexpectedly, T3 failed to modulate the expression of AIGF mRNA. T3 was also unable to significantly affect TGF beta 1 mRNA levels in androgen-stimulated SC-3 cells. More importantly, a neutralizing antibody against TGF beta 1 could not block T3-dependent inhibition of androgen-induced SC-3 cell growth. However, the inhibitory ability of T3 was potentiated by TGF beta 1. In addition, T3 treatment resulted in a significant inhibition of AIGF-induced DNA synthesis. Thus, T3 treatment renders SC-3 cells somehow refractory to AIGF. The signal pathway for T3 to reduce AIGF responsiveness may be shared by TGF beta 1.

Suramin interrupts androgen-inducible autocrine loop involving heparin binding growth factor in mouse mammary cancer (Shionogi carcinoma 115) cells

The androgen-dependent clonal cell line SC-3, derived from Shionogi carcinoma 115, secretes a fibroblast growth factor (FGF)-like autocrine growth factor in response to androgen, which is able to bind to FGF receptors. In SC-3 cells, FGF receptor expression is upregulated by the SC-3-derived growth factor, providing a means of amplifying an autocrine loop of cell growth. In the present investigations, the effects of the polysulfonated naphthylurea suramin on this autocrine loop and its amplification in SC-3 cells were studied. Suramin inhibited androgen-dependent growth of SC-3 cells in a concentration-dependent fashion: approximately 50% inhibition was observed at 25 microM. [3H]Thymidine incorporation into the cells stimulated with partially purified SC-3-derived growth factor was inhibited by suramin in a similar way. Additionally, suramin inhibited acidic (a) or basic (b) FGF-induced cell proliferation, though relatively high concentrations were necessary to achieve the maximal inhibition. Pretreatment of SC-3 cells with suramin decreased cell surface 125I-bFGF binding without altering dissociation constant (Kd) of the binding sites. When the cells were incubated with 250 microM suramin for 24 h, the maximum binding (Bmax) decreased to almost 50% of the control. Treatment with suramin also decreased the levels of FGF receptor-1 mRNA to a similar extent, whereas it appeared not to affect the levels of beta-actin mRNA. Moreover, suramin completely blocked androgen- or bFGF-induced accumulation of FGF receptor-1 mRNA. The inhibitory effects of suramin on FGF receptor expression were reversed by simultaneous addition of high concentrations of bFGF. These results indicate that suramin exerts its potent antiproliferative action on SC-3 cells through inhibition of an androgen-inducible autocrine loop involving SC-3-derived growth factor and FGF receptor.

Non-classical androgenic actions of RU38486 in androgen-responsive Shionogi carcinoma 115 cells in serum-free culture

Antiglucocorticoid and antiprogestin RU38486 (RU486) stimulated the growth of highly androgen- and moderately glucocorticoid-sensitive SC-3 cells (a cloned cell line from Shionogi mouse mammary carcinoma 115) in a dose-dependent manner. A maximal 8-fold stimulation of growth by RU486 has been observed at 10(-7) M in a serum-free medium and its potency has been found to be almost the same as that of dexamethasone (Dex). The growth rate of SC-3 cells treated by triamcinolone acetonide (TA) or Dex combined with RU486 at 10(-9)-10(-7) M was enhanced compared to cells treated by TA or Dex alone, indicating that RU486 had additive rather than antagonistic effects. Our previous study revealed that RU486 could compete with the specific uptake of [3H]testosterone in intact SC-3 cells at relatively low affinity and the present study showed that the stimulatory effect of RU486 on the growth of SC-3 cells was significantly inhibited by pure antiandrogen flutamine and that half-maximal inhibition by flutamine was achieved at 10(-6) M. Moreover, we demonstrated that the conditioned medium from RU486-stimulated SC-3 cells contained growth-promoting activity which caused a 3.5-fold increase in DNA synthesis by SC-3 cells in the absence of RU486 and which was abolished by treatment with heparin-Sepharose. These results indicate that RU486-induced growth of SC-3 cells may be expressed as an androgenic activity through androgen receptor and mediated by a heparin-binding growth factor.

Heparin inhibits autocrine stimulation but not fibroblast growth factor stimulation of cell proliferation of androgen-responsive Shionogi carcinoma 115

An androgen-responsive cloned cell line (SC-3) derived from Shionogi carcinoma 115 (SC115) has been shown to secrete fibroblast growth factor (FGF)-like peptide in response to androgen, which binds to FGF receptor and promotes the proliferation of SC-3 cells in an autocrine mechanism. Since the androgen-induced autocrine factor has a property to bind heparin, we examined the effects of heparin on the growth of SC-3 cells. Heparin was found to exhibit significant inhibition of testosterone-induced growth in a concentration-dependent manner: Approximately 50% inhibition was found at a concentration of 0.1 micrograms/ml. DNA synthesis of SC-3 cells induced by testosterone was also inhibited strongly by heparin, and less strongly by heparan sulfate and dermatan sulfate. Proliferation of SC-3 cells induced by acidic (a) or basic (b) FGF appeared not to be modulated by heparin. In contrast, heparin efficiently blocked DNA synthesis stimulated with androgen-induced growth factor in the conditioned medium from testosterone-treated cells. These results indicate that heparin inhibits autocrine loop in SC-3 cells induced by androgen. Thus, the autocrine growth factor possesses a different characteristic from aFGF and bFGF in that its bioactivities are negatively modulated by the glycosaminoglycan.

Up-regulation of fibroblast growth factor (FGF) receptor mRNA levels by basic FGF or testosterone in androgen-sensitive mouse mammary tumor cells

Since we had previously shown that both basic fibroblast growth factor (bFGF) and testosterone stimulate the growth of mouse mammary carcinoma cells (SC-3) in serum-free culture, we tested the effect of bFGF or testosterone on FGF receptor mRNA levels. Northern blot analyses revealed that stimulation with bFGF resulted in a 5-fold increase in FGF receptor mRNA levels at 6-8 h followed by a decline to the unstimulated levels at 24 h. Simultaneous addition of cycloheximide blocked bFGF-induced accumulation of FGF receptor mRNA, although exposure of SC-3 cells to cycloheximide alone caused marginal increase in its basal level. Neither phorbol ester nor forskolin stimulated FGF receptor mRNA expression, but testosterone could raise FGF receptor mRNA levels. To obtain the maximum stimulation, however, testosterone required the longer stimulation period (12 h) than bFGF, suggesting that testosterone-induced FGF receptor mRNA accumulation is mediated through an induction of FGF-like growth factor.

Effects of antiandrogens on growth of androgen-dependent mouse mammary tumor (Shionogi carcinoma 115) in vivo and in vitro

Binding affinities of modified steroidal anthrasteroids, 3 beta-hydroxy-3a beta,6-dimethyl-2,3,3a,4,5,8,9,10,10a beta,11,11a beta, 11b alpha-dodecahydro-1H-cyclopenta[a]anthracene-8-one (1) and 3a beta,6-dimethyl-2,3,3a,4,5,8,9,10,10a beta,11,11a beta,11b alpha-dodecahydro-1H-cyclopenta[a]anthracene-3,8-dione (2), the steroid oxendolone and the nonsteroid AA560, for the androgen receptor (AR) of Shionogi carcinoma 115 (SC115) and their effects on the growth of SC115 were investigated in vivo and in vitro. The inhibitory effects of these compounds on testosterone 5 alpha-reductase of SC115 tissues were also measured. The relative binding affinities of these compounds were 3.17-0.03% of that of dihydrotestosterone, and their rank order was (1) greater than AA560 greater than oxendolone much greater than (2). In the presence of 10(-9) M testosterone, anthrasteroids and AA560 inhibited the growth of SC115 cells at 10(-7) M in a serum-free medium, but oxendolone did not. In the absence of testosterone, (1), (2) and oxendolone promoted cell growth at 10(-6), 10(-7) and 10(-7) M, respectively. However, AA560 nearly completely blocked cell growth at 10(-5) M. At a 2 mg daily dose for 13 days, (1) and AA560 powerfully inhibited tumor growth in castrated DS mice treated with testosterone propionate but oxendolone had almost no effect. Anthrasteroids and oxendolone showed weak but significant agonistic activity in vivo. Anthrasteroids markedly inhibited 5 alpha-reductase activity of SC115, oxendolone weakly and AA560 not at all. The remarkable antiandrogenic activities of (1) and AA560 may partially result from their higher affinities for the AR of SC115 but other yet unknown mechanisms may also contribute to these activities.

Growth stimulation by androgens, glucocorticoids or fibroblast growth factors and the blocking of the stimulated growth by antibody against basic fibroblast growth factor in protein-free culture of Shionogi carcinoma 115 cells

Shionogi carcinoma 115 (SC115) has been accepted for 20 years as an androgen-responsive mouse mammary tumor. We have established an androgen-dependent cloned cell line (SC-3) from a SC115 tumor. In a serum-free medium, testosterone (T) or fibroblast growth factors (FGFs) markedly stimulate the growth of SC-3 cells, and the T-induced growth was shown to be mediated through FGF-like peptide(s) in an autocrine mechanism. Since we used the serum-free culture including 0.1% bovine serum albumin (BSA), a partially serum-containing condition, putative roles of BSA- or serum-borne growth factors in growth stimulation of autocrine production of FGF-like peptide(s) could not be excluded. This paper reports findings performed in a protein-free medium including plating [Ham's F-12:MEM (1:1; v/v)]. In the protein-free culture, the growth of SC-3 cells was significantly stimulated by the addition of greater than or equal to 10(-10) M T (up to 20-fold), greater than or equal to 10(-7) M dexamethasone (Dex; up to 7-fold) or greater than or equal to 1 ng/ml basic (b) or acidic FGF (up to 10-fold); other various growth factors had no such effects. Furthermore, DNA synthesis of SC-3 cells induced by T, Dex or bFGF was similarly and markedly inhibited by bFGF neutralizing antibody IgG. Therefore, the present findings seem to demonstrate that androgens or high levels of glucocorticoids induce the production and secretion of FGF-like peptide(s) from SC-3 cells for their growth even in the absence of additional support by other factors.

Acquired expression of hst-1 in an autonomous subline (Chiba subline 2) derived from androgen-responsive mouse mammary tumor (Shionogi carcinoma 115)

Since growth of Shionogi Carcinoma 115 (SC 115) and its autonomous subline (CS 2) were regulated by fibroblast growth factor-like peptide, expression of int-2 and hst-1 was examined in these cell lines. Hybridization of genomic DNA with long terminal repeat of mouse mammary tumor virus (MMTV) revealed the same pattern of restriction fragments, showing the same integration of MMTV. Although weak expression of int-2 was noticed in the two cells, clear expression of hst-1 was seen only in CS 2 cultured with/without testosterone. It is suggested that autonomous growth of androgen-unresponsive CS 2 is connected with expression of hst-1.