Studies on the expression of fibroblast growth factors and fibroblast growth factor receptors in human prostate cancer

PURPOSE: We tried to clarify the role of fibroblast growth factors (FGFs) and those receptors (FGF-Rs) in cell proliferation of human prostate cancer. METHODS: The mRNA expression of FGF1, FGF2, FGF7, FGF-R1, FGF-R2 (IIIb), and FGF-R2 (IIIc) was investigated by RT-PCR in androgen sensitive cells (LNCaP), androgen-independent cells (PC3) and primary cultured stromal (PS) and epithelial cells (PE) from benign prostatic hyperplasia (BPH). Expression of the mRNA of FGF-R1, FGF-R2 (IIIb) and FGF-R2 (IIIc) in human prostate cancer tissue was similarly analyzed. Furthermore, the level of FGF-R1 expression in human prostate cancer was measured by semi-quantitative RT-PCR. RESULTS: FGF-R1 mRNA was detected in LNCaP, PC3 and the primary cultured stromal cells of BPH. FGF-R2 (IIIb) was seen in LNCaP cells and the primary cultured epithelial cells of BPH, while FGF-R2 (IIIc) was only observed in PC3. FGF1 mRNA was expressed in LNCaP and PC3, while FGF2 mRNA was in PC3 alone. The expression of FGF7 mRNA was detected only in the primary cultured stromal cells. Of 17 patients with human prostate cancer, FGF-R2 (IIIb) was detected in 2 and FGF-R2 (IIIc) in 15. Histological type of two cases having FGF-R2 (IIIb) were well differentiated adenocarcinoma. The mRNA levels of FGF-R1 in poorly and moderately differentiated types were significantly higher than those in well differentiated ones (p < 0.05). CONCLUSION: These findings suggest that several changes of expression in FGFs and FGF-Rs may correlate with malignant progression of human prostate cancer.     

Immunolocalization of basic fibroblast growth factor and fibroblast growth factor receptor-1 and receptor-2 in rat cranial sutures

Craniosynostosis is a common disorder with an unknown etiology. Recent genetic mapping studies have demonstrated a strong linkage between several familial craniosynostotic syndromes and mutations in fibroblast growth factor receptor 1 (FGF-R1) and 2 (FGF-R2). The purpose of this experiment was to investigate by immunohistochemistry the protein production of these receptors as well as of their most prevalent ligand, basic fibroblast growth factor (bFGF), before, during, and after sutural fusion in rat cranial sutures. The posterior frontal (normally fuses between postnatal days 12 and 22) and sagittal (remains patent) sutures of embryonic day 20 and neonatal days 6, 12, 17, 22, and 62 (n = 3 per group) were harvested, fixed, and decalcified. Five-micrometer sections were stained with polyclonal antibodies against bFGF, FGF-R1, and FGF-R2, and patterns of immunohistochemical staining were assessed by independent reviewers. Our results indicate that increased bFGF production correlates temporally with suture fusion, with increased staining of the dura underneath the fusing suture prior to fusion followed by increased staining within osteoblasts and sutural cells during fusion. FGF-R1 and, to a lesser extent FGF-R2 immunostaining revealed a different pattern of localization with increased immunostaining within the patent sagittal suture at these time points. These results implicate bFGF in the regulation of sutural fusion and may imply autoregulatory mechanisms in fibroblast growth factor receptor expression.     

Basic fibroblast growth factor receptors and their prognostic value in human breast cancer

We performed a saturation binding study with 125I-labeled FGF (fibroblast growth factor)-2 in a nonselected series of 250 human primary breast cancers. Two hundred twenty-five breast cancer biopsies possessed bFGFR (basic FGF receptor). The median dissociation constant was 0.35 nM (range, 0.014-1.9), and the median concentration was 1126 fmol/mg protein (range, 49-7328). FGFR-1 was localized, using a specific monoclonal antibody, in cancerous cells and in epithelial cells in normal breast or in benign tumors. In all of the tissues studied, light stromal cell staining was also observed. Thus, the localization of FGFR-1 in carcinoma cells supports the hypothesis that an important part of FGF-2 binding reflects binding to FGFR-1. bFGFR concentrations were positively correlated to estrogen receptor and progesterone receptor levels. Cox univariate analyses showed that the bFGFR (> or = upper quartile) was associated to longer relapse-free survival [P = 0.004; RR (risk ratio), 0.46] and overall survival (P = 0.001; RR, 0.35); age, estrogen receptor levels, progesterone receptor levels, node involvement, tumor diameter, and histoprognostic grading were prognostic, also. In Cox multivariate analyses, only the bFGFR, age, node involvement, and histoprognostic grading were prognostic factors; the bFGFR was associated with longer relapse-free survival (P = 0.03; RR, 0.4) and overall survival (P = 0.009; RR, 0.3). The present study confirms that FGF could be an important regulator of human breast cancer growth and that patients with a high level of bFGFR had a better prognosis.     

Expression of receptors for basic fibroblast growth factor on human periodontal ligament cells

Basic fibroblast growth factor (FGF-2; bFGF) is a major mitogen for connective tissue cells, and participates in the healing process. It has already been reported that FGF-2 could be applicable to enhance periodontal regeneration. In the present study, we examined FGF receptor (FGFR) expression on human periodontal ligament (PDL) cells. The binding of [125I]-labeled FGF-2 to human PDL cells was studied by radioreceptor assay. The binding of [125I]-FGF-2 to PDL cells reached a plateau after 2.5 h incubation at 4 degrees C and was inhibited by the addition of unlabeled FGF-2 and acidic FGF (FGF-1; aFGF), but not insulin-like growth factor-I, platelet-derived growth factor and transforming growth factor-beta 1. Scatchard analysis revealed the presence of approximately 1.0 x 10(5) FGF-2 binding sites per cell with an apparent Kd of 1.2 x 10(-10) M. Interestingly, the binding of [125I]-FGF-2 on PDL cells reached its maximum at d 6 of the culture and then gradually decreased. Scatchard analysis also demonstrated that the number of FGFRs on a PDL cell was altered during the course of the culture, while the affinity between FGF-2 and its receptor was not. The responsiveness of PDL cells to FGF-2, which was monitored by the inhibitory effect on alkaline phosphatase activity, was reduced in proportion to the decrease in the number of FGFRs on the PDL cells. The present study suggests that PDL cells alter the responsiveness to FGF-2 during the course of the culture by changing the density of its receptor, and that the density of FGFR expression might be a marker of the cytodifferentiation of PDL cells into mineralized tissue forming cells.     

Size exclusion HPLC method for the determination of acidic fibroblast growth factor in viscous formulations

A size exclusion HPLC method has been developed to determine the protein concentration of pharmaceutical formulations of recombinant acidic fibroblast growth factor (aFGF). These topical aFGF formulations not only contain low levels of protein mass (50 micrograms ml-1), but also include buffer ions, polysaccharide polyanions to conformationally stabilize aFGF and 1% hydroxyethylcellulose to increase the solution's viscosity. A cesium chloride mobile phase is utilized during SEC-HPLC to dissociate aFGF from the pharmaceutical excipients and to minimize nonspecific interaction of the protein with the column matrix. The protein content of a viscous aFGF formulation is determined by comparison of aFGF peak areas to standards of known concentration. Fluorescence spectroscopy was utilized to directly demonstrate that the protein remains in its native conformation during sample preparation and analysis.     

Basic fibroblast growth factor and insulinlike growth factor I support the growth of human septal chondrocytes in a serum-free environment

OBJECTIVE: To determine if insulinlike growth factor I (IGF-I) and basic fibroblast growth factor (bFGF), individually or in combination, support the growth and viability of human septal chondrocytes in a serum-free medium (SFM) and a serum-enhanced culture medium. DESIGN: Chondrocytes were recovered from enzymatically digested human septal cartilage and were plated for monolayer culture in a newly developed medium. The medium included Dulbecco modified Eagle medium mixed 1:1 with Ham F12 medium and a supplement of known amounts of 2 growth factors-bFGF (100 ng/mL) and IGF-I (100 ng/mL)-used in combination and separately. RESULTS: The combination of IGF-I and bFGF enhanced chondrocyte growth and maintained a high degree of viability in SFM and 10% fetal calf serum. After an initial lag, the SFM, augmented with both growth factors, produced a comparable number of viable cells (4.25+/-0.31 x 10(4)) to that of the medium with 10% fetal calf serum (4.64+/-0.35 x 10(4)) by the seventh day of the experiment. Combined with the 2 growth factors, 10% fetal calf serum provided the greatest proliferation by the end of the experiment. However, the overall mean cell counts for the IGF-I- and bFGF-enhanced SFM were not statistically different. CONCLUSIONS: The combination of IGF-I and bFGF in a serum-free and a serum-supplemented environment supports the growth and viability of human septal chondrocytes in short-term culture. In an SFM, the results obtained approximate those produced in a medium enhanced with 10% fetal calf serum.     

Effects of acidic fibroblast growth factor on neuronal activity of the parvocellular part in rat paraventricular nucleus

The effects of acidic fibroblast growth factor (aFGF) and its amino-terminal and carboxyl-terminal fragments (aFGF(1-15) and aFGF(114-140), respectively were examined on the neuronal activity in the parvocellular part of the paraventricular nucleus. As well known, this part contains a lot of corticotropin-releasing factor (CRF)-immunoreactive neurons. Application of 1 pg/ml and 2 pg/ml aFGF produced responses in 29.7% and 46.7% of neurons tested, respectively. Half or more than half of the responding neurons increased their discharge rate. Application of 0.2 ng/ml and 0.4 ng/ml aFGF(1-15) (1-15) also elicited response in 46.2% and 68.8% of neurons tested, respectively. Of these responding neurons, more than two third increased their firing rate. However, most of neurons tested for 0.67 ng/ml and 1.33 ng/ml aFGF(114-140) did not respond. Results suggest that aFGF and aFGF(1-15) promote the release of CRF through the activation of CRF-containing neurons.     

FGF6 modulates the expression of fibroblast growth factor receptors and myogenic genes in muscle cells

A recent policy change by the University of California (UC) provides a unique natural experiment for investigating how consumers respond to financial incentives when choosing health plans. In 1994 UC went from a premium contribution policy that subsidized more costly plans to a policy of contributing a constant dollar amount. As a result, employee premium contributions increased for roughly one-third of university employees. The response to this change in relative prices was strong. Whereas only 5 percent of employees facing constant premium contributions switched plans, roughly one-quarter of those facing premium contribution increases of less than $10 per month switched to lower-cost plans. Higher price increases led to even greater rates of plan switching.     

Vascular endothelial growth factor, placenta growth factor and their receptors in isolated human trophoblast

The expression of the angiogenic growth factors, vascular endothelial cell growth factor (VEGF) and placenta growth factor (PIGF) was demonstrated in isolated human term cytotrophoblast and in vitro differentiated syncytiotrophoblast. RNase protection assays demonstrated VEGF expression in both cytotrophoblast and syncytiotrophoblast while prominent PIGF expression was detected in both types of trophoblast by Northern blot analyses. VEGF expression increased approximately eightfold in trophoblast cultured under hypoxic conditions (1 per cent O2) yet PIGF expression decreased 73 +/- 5.5 per cent in the same trophoblast. These results suggest distinct regulatory mechanisms govern expression of VEGF and PIGF in trophoblast. Characterization of the VEGF/PIGF receptors, KDR and flt-1, revealed the presence of flt-1 mRNA in isolated cytotrophoblast and in vitro differentiated syncytiotrophoblast. KDR was not detected in the isolated trophoblast. Exogenous rhVEGF induced c-Jun N-terminal kinase (JNK) activity in the normal trophoblast indicating that the flt-1 receptors on trophoblast are functional. Trophoblast-derived VEGF/PIGF could act in a paracrine fashion to promote uterine angiogenesis and vascular permeability within the placental bed. In addition, presence of function flt-1 on normal trophoblast suggests that VEGF/PIGF functions in an autocrine manner to perform an as yet undefined role in trophoblast invasion, differentiation, and/or metabolic activity during placentation.     

Basic fibroblast growth factor promotes the proliferation of human megakaryocyte progenitor cells

Basic fibroblast growth factor (bFGF), a multifunctional growth factor produced by bone marrow stromal cells, is known to be a potent modulator of hematopoiesis. Because bFGF is present in both human megakaryocytes (MKs) and platelets, we have hypothesized that this growth factor might affect human megakaryocytopoiesis. To test this hypothesis, either low density bone marrow (BM) cells (LDBM), a human BM subpopulation (CD34+ DR+) enriched for the colony-forming unit megakaryocyte (CFU-MK) or a BM subpopulation (CD34+ DR-) enriched for the more primitive burst-forming unit megakaryocyte (BFU-MK) were assayed in the presence of this growth factor. The effect of bFGF on MK colony formation differed according to the cell population assayed. bFGF alone had on MK colony-stimulating activity (MK-CSA) when either CD34+ DR+ or CD34+ DR- BM cells were cloned, but exhibited MK-CSA equivalent to that of interleukin-3 (IL-3) when LDBM cells were used as the target cell population. The MK-CSA of bFGF was inhibited by the addition of neutralizing antisera to either IL-3 and/or granulocyte-macrophage colony-stimulating factor (GM-CSF) but not IL-6. The addition of excess amounts of either IL-3 or GM-CSF to cultures containing bFGF plus anti-IL-3 or anti-GM-CSF reversed the inhibition by the corresponding antisera. The addition of bFGF and IL-3 to assays containing CD34+ DR+ or CD34+ DR- cells increased the size of both CFU-MK- and BFU-MK-derived colonies, respectively, when compared with assays containing IL-3 alone. This increase in MK colony size mediated by bFGF was not affected by addition of either an anti-GM-CSF or anti-IL-6 neutralizing antisera. When LDBM cells were assayed, bFGF alone increased CFU-MK-derived colony size when compared with control values. However, this potentiation of MK colony size by bFGF could be reversed by the addition of either anti-IL-3 or anti-GM-CSF but not anti-IL-6 antisera. In addition, the effects of bFGF and IL-3 on the size of MK colonies cloned from LDBM were not additive. These results suggest that bFGF affects human megakaryocytopoiesis by directly promoting MK progenitor cell proliferation and stimulating BM accessory cells to release growth factor(s) with MK-CSA, such as IL-3 and GM-CSF. We conclude that bFGF, likely produced by cellular components of the BM microenvironment, plays an important role in the control of human megakaryocytopoiesis.     

Targeted delivery of DNA encoding cytotoxic proteins through high-affinity fibroblast growth factor receptors

Nonviral DNA delivery strategies for gene therapy have generally been limited by a lack of specificity and efficacy. However, ligand-mediated endocytosis can specifically deliver DNA in vitro to cells bearing the appropriate cognate receptors. Similarly, in order to circumvent problems related to efficacy, DNA must encode proteins with high intrinsic activities. We show here that the ligand basic fibroblast growth factor (FGF2) can target FGF receptor-bearing cells with DNA encoding therapeutic proteins. Delivery of genes encoding saporin, a highly potent ribosomal inactivating protein, or the conditionally cytotoxic herpes simplex virus thymidine kinase, a protein that can kill cells by activating the prodrug ganciclovir, is demonstrated. The saporin gene was codon optimized for mammalian expression and demonstrated to express functional protein in a cell-free assay. FGF2-mediated delivery of saporin DNA or thymidine kinase DNA followed by ganciclovir treatment resulted in a 60 and 75% decrease in cell number, respectively. Specificity of gene delivery was demonstrated in competition assays with free FGF2 or with recombinant soluble FGF receptor. Alternatively, when histone H1, a ligand that binds to cell surface heparan sulfate proteoglycans ("low-affinity" FGF receptors), was used to deliver DNA encoding thymidine kinase, no ganciclovir sensitivity was observed. These findings establish the feasibility of using ligands such as FGF2 to specifically deliver genes encoding molecular chemotherapeutic agents to cells.     

Localization of hepatocyte growth factor and tubulointerstitial lesions in IgA nephropathy

We report a 59-year-old male with abdominal aortic coarctation presented as paraplegia due to spinal hemorrhage caused by the rupture of abnormally dilated spinal artery. In coarctation of aorta, coarctation is usually located in the aortic isthmus which could be the cause of cervical and upper thoracic myelopathy. However, there has been no report of abdominal aortic coarctation with hemorrhagic transverse myelopathy. In this case hemorrhage occurred after surgical treatment and prescribed warfarin may have exaggerated the outcome.     

Levels of vascular endothelial growth factor, hepatocyte growth factor/scatter factor and basic fibroblast growth factor in human gliomas and their relation to angiogenesis

Angiogenesis is a possible target in the treatment of human gliomas. To evaluate the role of 3 growth factors, vascular endothelial growth factor (VEGF), hepatocyte growth factor/scatter factor (HGF/SF) and basic fibroblast growth factor (bFGF), in the angiogenic cascade, we determined their levels in extracts of 71 gliomas by enzyme-linked immunosorbent assay (ELISA). The levels of bFGF were only marginally different between gliomas of World Health Organization (WHO) grade II (low grade) and grades III and IV (high grade). In contrast, the mean concentrations of VEGF were 11-fold higher in high-grade tumors and those of HGF/SF 7-fold, respectively. Both were highly significantly correlated with microvessel density (p < 0.001) as determined by immunostaining for factor VIII-related antigen. In addition, VEGF and HGF/SF appeared to be independent predictive parameters for glioma microvessel density as determined by multiple regression analysis. We measured the capacity of all 3 factors to induce endothelial tube formation in a collagen gel. In this assay, bFGF was found to be an essential cofactor with which VEGF as well as HGF/SF were able to synergize independently. According to the concentrations of angiogenic factors, extracts from high-grade tumors were significantly more potent in the tube formation assay than the low-grade extracts (p = 0.02). Adding neutralizing antibodies to bFGF, VEGF and HGF/SF together with the extracts, tube formation was inhibited by up to 98%, 62% and 54%, respectively. Our findings suggest that bFGF is an essential cofactor for angiogenesis in gliomas, but in itself is insufficient as it is present already in the sparsely vascularized low-grade tumors. Upon induction of angiogenesis in high-grade tumors, bFGF may synergize with rising levels of not only VEGF but possibly also with HGF/SF, which appears here to be an independent angiogenic factor.     

Induction of basic fibroblast growth factor mRNA by basic fibroblast growth factor in Müller cells

PURPOSE: To investigate the induction of basic fibroblast growth factor (bFGF) gene expression in cultured rat Müller cells by bFGF and to study the mechanism of induction. METHODS: Müller cells from 1- to 3-day-old Sprague-Dawley rats were isolated and cultured with Dulbecco's modified Eagle's medium with 10% fetal calf serum. Cultured cells were identified by immunocytochemistry using antibodies against vimentin, carbonic anhydrase II, and glutamine synthetase. Cells of passages 1 through 4 were treated with bFGF, the protein kinase C (PKC) inhibitor, H-7; calphostin C, or the PKC activator, PMA; and protein kinase A (PKA) inhibitor, H-89; as well as the adenylate cylase activator, forskolin; or the adenylate cyclase inhibitor, SQ22536. Northern blot analysis was performed to determine the mRNA expression of bFGF, ciliary neurotrophic factor (CNTF) and brain-derived neurotrophic factor (BDNF). RESULTS: Addition of bFGF to culture medium induced bFGF gene expression in a dose- and time-dependent manner. Induction of bFCF mRNA started at a bFGF concentration of 0.1 ng/ml. The bFGF mRNA level was elevated by 2-fold at 1 ng/ml of bFGF, 2.8-fold at 5 ng/ml, and reached a peak of 4-fold at 10 ng/ml and 3.7-fold at 50 ng/ml. At 10 ng/ml of bFGF, induction of bFGF mRNA was observed as early as 2 hours (2-fold) after treatment. The bFGF mRNA level continued to increase to 3.7-fold by 4 hours, and reached a maximum of 4.4-fold by 8 hours. A slow decline of the bFGF mRNA level was observed after 8 hours of bFGF treatment (3.5-fold by 12 hours, and 3-fold by 24 hours). This induction of bFGF gene expression was blocked by PKC inhibitors H-7 (30 microM). The PKC activator PMA (0.1 microM) also upregulated bFGF gene expression, but the effects of bFGF and PMA were not additive. An adenylate cyclase inhibitor, SQ22536 (100 microM), did not inhibit bFGF-induced bFGF gene expression. Although forskolin (5 microM), an adenylate cyclase activator, also upregulated the level of bFGF mRNA, the effects of forskolin and bFGF were additive. In addition, no inhibitory effect on bFGF-induced expression of bFGF mRNA was found using H-89 (1 microM). Exogenous bFGF did not alter the mRNA levels of CNTF and BDNF. CONCLUSIONS: These results indicate that bFGF induces bFGF gene expression in cultured rat Müller cells through PKC activation. The authors' findings raise the possibility that Müller cells in vivo also respond to available bFGF (for example, that released from the endogenous reservoirs in the case of injury) or to exogenous bFGF by producing more bFGF, which could in turn promote photoreceptor survival.     

Transforming growth factor betas and their receptors in human liver cirrhosis

BACKGROUND: Transforming growth factor betas (TGF-betas) are a group of homologous polypeptides that exert pleiotropic effects on various cell types and stimulate the formation of extracellular matrix and fibrosis. To evaluate whether TGF-beta isoforms (TGF-beta1, TGF-beta2 and TGF-beta3) and their receptors (types I-III) are also of importance in the pathophysiology of liver cirrhosis, we analysed their concomitant expression and localization in human liver cirrhosis. PATIENTS: Cirrhotic liver tissue samples were obtained from 17 patients (four women, 13 men) with a median age of 41 years (range 22-67). Normal liver tissues from ten patients (seven women, three men) with a median age of 55 years (range 45-75) served as controls. METHODS: The tissues were fixed in Bouin's solution and paraffin-embedded for histological analysis. For RNA analysis, freshly obtained tissue samples were snap-frozen in liquid nitrogen and stored at -80 degrees C until analysed. Northern blot analysis was used to examine the expression of TGF-beta1, beta2 and beta3 and their receptors, type I (TbetaR-I), type II (TbetaR-II) and type III (TbetaR-III). Immunohistochemistry was performed to determine the localization of the corresponding proteins in the normal and the cirrhotic liver. RESULTS: Northern blot analysis revealed enhanced expression (P < 0.05) of TGF-beta1 (twofold increase), TGF-beta2 (threefold increase) and TGF-beta3 (8.5-fold increase) and of TbetaR-II (threefold increase) mRNA in liver cirrhosis in comparison with normal controls. In contrast, TbetaR-I (ALK-5) and TbetaR-III mRNA expression showed no significant changes. No TGF-beta isoform immunoreactivity was present in hepatocytes in either normal livers or in liver cirrhosis. However, in liver cirrhosis, intense TGF-beta1 immunoreactivity was present in bile duct and ductular epithelial cells (including ductular proliferations) and in inflammatory cells. In a few sinusoidal lining cells, faint TGF-beta1 and moderate TGF-beta2 immunoreactivity was present. TGF-beta3 immunostaining was present in bile duct and ductular epithelial cells, in inflammatory cells and in fibroblast-like spindle cells in liver cirrhosis. For TbetaR-I and TbetaR-II, the immunoreactivity was localized in hepatocytes and biliary cells in normal and cirrhotic liver tissues, with higher intensity for TbetaR-II in the cirrhotic liver. CONCLUSION: Enhanced expression of all three TGF-bea isoforms and of TbetaR-II in liver cirrhosis suggests their involvement in this fibrotic disorder. The higher immunoreactivity of the three TGF-beta isoforms in the bile duct epithelial cells in cirrhotic tissues suggests a possible role of these cells in the pathogenesis of liver cirrhosis.     

Pleiotropic features of syndromic craniosynostoses correlate with differential expression of fibroblast growth factor receptors 1 and 2 during human craniofacial development

Partners in romantic relationships provided reports on perceived changes in their love, commitment, and satisfaction and completed contemporaneous scales on the same relationship phenomena multiple times over several years. At each wave of the longitudinal study, participants whose relationships had remained intact perceived that their love and related phenomena had increased since they had last participated in the study. However, their scores on contemporaneous scales did not generally increase over time. Analyses indicated that participants' reports of change were related to actual change in love, commitment, and satisfaction scores and with future relationship stability. Furthermore, participants who experienced a breakup during the longitudinal study reported an overall decrease in their positive affect in the months prior to the breakup.     

Keratinocyte growth factor and fibroblast growth factor action on DNA synthesis in rat and human hepatocytes: modulation by heparin

Keratinocyte growth factor (KGF/FGF-7) is a member of the fibroblast growth factor (FGF) superfamily. Unlike other members of the family, the biological activity of KGF appears to be restricted to epithelial cells. Here we have tested the activity of KGF, acidic fibroblast growth factor (aFGF), and basic fibroblast growth factor (bFGF) on normal adult rat and human hepatocytes and their modulation by heparin. Although more modest than the growth response to epidermal growth factor (EGF) and hepatocyte growth factor (HGF), recombinant KGF enhanced DNA synthesis in rat hepatocytes by two- to threefold. This stimulation occurred in the absence of serum and of other exogenous growth factors. Addition of heparin inhibited the KGF response. Although basic FGF showed little activity on rat hepatocytes, acidic FGF stimulated DNA synthesis by approximately twofold and was substantially enhanced by heparin. In contrast to rat cells, human hepatocytes consistently failed to respond to KGF, aFGF, or bFGF with or without heparin, under conditions where EGF and HGF stimulated DNA synthesis up to sixfold. These results indicate that KGF is capable of acting as a complete mitogen for rat hepatocytes in culture and that the activity is consistent with expression by these cells of a type II FGF receptor subtype, the KGF receptor. These observations suggest that KGF/aFGF together with proteoglycans may help regulate rat but not human liver growth.