Co-expression of hepatocyte growth factor and its receptor in human prostate cancer

RasGRP3 contributes to formation and maintenance of the prostate cancer phenotype

RasGRP3 mediates the activation of the Ras signaling pathway that is present in many human cancers. Here, we explored the involvement of RasGRP3 in the formation and maintenance of the prostate cancer phenotype. RasGRP3 expression was elevated in multiple human prostate tumor tissue samples and in the human androgen-independent prostate cancer cell lines PC-3 and DU 145 compared with the androgen-dependent prostate cancer cell line LNCaP. Downregulation of endogenous RasGRP3 in PC-3 and DU 145 cells reduced Ras-GTP formation, inhibited cell proliferation, impeded cell migration, and induced apoptosis. Anchorage-independent growth of the PC-3 cells and tumor formation in mouse xenografts of both cell lines were likewise inhibited. Inhibition of RasGRP3 expression reduced AKT and extracellular signal-regulated kinase 1/2 phosphorylation and sensitized the cells to killing by carboplatin. Conversely, exogenous RasGRP3 elevated Ras-GTP, stimulated proliferation, and provided resistance to phorbol 12-myristate 13-acetate-induced apoptosis in LNCaP cells. RasGRP3-overexpressing LNCaP cells displayed a markedly enhanced rate of xenograft tumor formation in both male and female mice compared with the parental line. Suppression of RasGRP3 expression in these cells inhibited downstream RasGRP3 responses, caused the cells to resume the LNCaP morphology, and suppressed growth, confirming the functional role of RasGRP3 in the altered behavior of these cells. We conclude that RasGRP3 contributes to the malignant phenotype of the prostate cancer cells and may constitute a novel therapeutic target for human prostate cancer.

Serum active hepatocyte growth factor (AHGF) in benign prostatic disease and prostate cancer

BACKGROUND

Hepatocyte growth factor (HGF) is secreted as an inactive single-chain precursor called pro-HGF. Pro-HGF is converted to an active two-chain form by HGF activator and matriptase. We attempted to clarify whether serum levels of active HGF (AHGF) could be used as a marker of prostate cancer.

METHODS

Serum levels of AHGF and total HGF (THGF; pro-HGF + AHGF) were measured by enzyme-linked immunosorbent assay in 38 patients with benign prostatic disease and 160 patients with prostate cancer.

RESULTS

Serum levels of AHGF in patients with untreated prostate cancer (0.37 +/- 0.12 ng/ml) were significantly higher than those in patients with benign prostatic disease (0.28 +/- 0.08 ng/ml) (P = 0.0001). Serum AHGF levels were increased in patients with stage D or D3 compared with stage B. In addition, there were significant differences in serum AHGF levels between patients with well-differentiated and poorly differentiated adenocarcinoma. Furthermore, the mean serum AHGF/THGF ratio in patients with stage D3 prostate cancer was significantly higher than that in patients with stage B.

CONCLUSIONS

AHGF may be a potential tumor marker for prostate cancer. Further studies in large groups of patients are needed to define the clinical value of AHGF.

Prognostic significance of plasma scatter factor/hepatocyte growth factor levels in patients with metastatic hormone- refractory prostate cancer: results from cancer and leukemia group B 150005/9480

BACKGROUND

Scatter factor, also known as hepatocyte growth factor (SF/HGF), is a polypeptide growth factor thought to be important in the growth and spread of prostatic carcinoma.

PATIENTS AND METHODS

Scatter factor/HGF levels in pretreatment plasma samples from 171 men with metastatic hormone-refractory prostate cancer enrolled in CALGB 9480 were quantified by solid-phase, enzyme-linked immunosorbent assay.

RESULTS

The Cox proportional hazards model was used to assess the prognostic importance of SF/HGF with adjustment for established prognostic factors. Median SF/HGF was 991 pg/mL (range, 212-2733 pg/mL). In a univariate analysis, although plasma SF/HGF levels above versus below the median value did not reach statistical significance (P = 0.0862), the cutoff point of > 935 pg/mL was associated with a significant reduction in overall survival (P = 0.0334). Patients with SF/HGF levels > 935 pg/mL experienced a median survival of 15 months compared with 19 months for men with SF/HGF levels < or = 935 pg/mL. In a multivariate analysis, adjusting for SF/HGF, prostate-specific antigen, lactate dehydrogenase, and performance status, only plasma alkaline phosphatase was significantly associated with overall survival (hazard ratio, 1.7; 95% confidence interval, 1.2-2.5; P = 0.0017).

CONCLUSION

Higher plasma levels of SF/HGF in men with hormone-refractory prostate cancer are associated with a decreased patient survival. Currently, SF/HGF levels do not appear to be of value as a contributor to multivariate models for prediction of outcome, but the association with decreased survival suggests that SF/HGF might be a potential target for therapy.

Met-Independent Hepatocyte Growth Factor-mediated regulation of cell adhesion in human prostate cancer cells

BACKGROUND

Prostate cancer cells communicate reciprocally with the stromal cells surrounding them, inside the prostate, and after metastasis, within the bone. Each tissue secretes factors for interpretation by the other. One stromally-derived factor, Hepatocyte Growth Factor (HGF), was found twenty years ago to regulate invasion and growth of carcinoma cells. Working with the LNCaP prostate cancer progression model, we found that these cells could respond to HGF stimulation, even in the absence of Met, the only known HGF receptor. The new HGF binding partner we find on the cell surface may help to clarify conflicts in the past literature about Met expression and HGF response in cancer cells.

METHODS

We searched for Met or any HGF binding partner on the cells of the PC3 and LNCaP prostate cancer cell models, using HGF immobilized on agarose beads. By using mass spectrometry analyses and sequencing we have identified nucleolin protein as a novel HGF binding partner. Antibodies against nucleolin (or HGF) were able to ameliorate the stimulatory effects of HGF on met-negative prostate cancer cells. Western blots, RT-PCR, and immunohistochemistry were used to assess nucleolin levels during prostate cancer progression in both LNCaP and PC3 models.

RESULTS

We have identified HGF as a major signaling component of prostate stromal-conditioned media (SCM) and have implicated the protein nucleolin in HGF signal reception by the LNCaP model prostate cancer cells. Antibodies that silence either HGF (in SCM) or nucleolin (on the cell surfaces) eliminate the adhesion-stimulatory effects of the SCM. Likewise, addition of purified HGF to control media mimics the action of SCM. C4-2, an LNCaP lineage-derived, androgen-independent human prostate cancer cell line, responds to HGF in a concentration-dependent manner by increasing its adhesion and reducing its migration on laminin substratum. These HGF effects are not due to shifts in the expression levels of laminin-binding integrins, nor can they be linked to expression of the known HGF receptor Met, as neither LNCaP nor clonally-derived C4-2 sub-line contain any detectable Met protein. Even in the absence of Met, small GTPases are activated, linking HGF stimulation to membrane protrusion and integrin activation. Membrane-localized nucelolin levels increase during cancer progression, as modeled by both the PC3 and LNCaP prostate cancer progression cell lines.

CONCLUSION

We propose that cell surface localized nucleolin protein may function in these cells as a novel HGF receptor. Membrane localized nucleolin binds heparin-bound growth factors (including HGF) and appears upregulated during prostate cancer progression. Antibodies against nucleolin are able to ameliorate the stimulatory effects of HGF on met-negative prostate cancer cells. HGF-nucleolin interactions could be partially responsible for the complexity of HGF responses and met expression reported in the literature.

Serum hepatocyte growth factor activator (HGFA) in benign prostatic hyperplasia and prostate cancer

OBJECTIVES

Hepatocyte growth factor activator (HGFA) is responsible for proteolytic activation of the precursor form of hepatocyte growth factor (HGF). We attempted to clarify whether serum levels of HGFA could be used as a marker for prostate cancer.

MATERIAL AND METHODS

Serum levels of total HGF and HGFA were measured by enzyme-linked immunosorbent assay in 99 healthy controls, 27 patients with benign prostatic hyperplasia (BPH) and 119 patients with prostate cancer.

RESULTS

: The mean+/-S.D. serum levels of HGFA in untreated prostate cancer and BPH cases were 0.42+/-0.24 and 0.50+/-0.26 ng/ml, respectively (no significant difference). Serum HGFA was significantly elevated in hormone-refractory prostate cancer (stage D3) compared to other stages, while HGF did not significantly differ with regard to clinical stage.

CONCLUSIONS

Serum HGFA tends was elevated in patients with advanced stage prostate cancer. Further studies in large groups of patients are needed to clarify the clinical value of HGFA.

Phenotypic switch from paracrine to autocrine role of hepatocyte growth factor in an androgen-independent human prostatic carcinoma cell line, CWR22R

Support mechanisms involved in growth of androgen-independent prostate cancer are primarily unknown. Hepatocyte growth factor (HGF)/Met has been suggested to be one of them based primarily on immunohistochemical studies. We conducted a series of experiments to assess the role of the HGF/Met system in an androgen-dependent human prostate carcinoma, CWR22 and its androgen-independent derivative, CWR22R. We found that action of HGF changed from paracrine to autocrine in progression to androgen-independent state. CWR22 tumors did not express HGF but expressed Met, whereas prostate stromal cells expressed HGF at a high level. Growth of CWR22 was stimulated either by addition of HGF to the culture or by the presence of prostate stromal cells. On the other hand, CWR22R cells expressed both HGF and Met. Knockdown of Met expression by RNA interference method suppressed the growth of CWR22R cells. Our data suggest that HGF is intimately involved in growth of human prostate cancer and that progression from the androgen-dependent to the androgen-independent state is associated with an adaptive switch in support mechanism from paracrine to autocrine. Our data offer one mechanism to account for androgen-independent human cancer growth.

Preventing diseases of the prostate in the elderly using hormones and nutriceuticals

The prostate has only one function, namely to secrete fluid containing substances that are needed for reproduction. This requires an extremely high concentration of androgens in the tissues. Benign prostatic hypertrophy (BPH) seems to be related to the long-term exposure of the prostate to the strong androgen 5alpha-dihydrotestosterone (DHT) and, possibly, to estrogens. The relation between prostate cancer and androgens is suggested to be U-shaped, with both extremes of androgen concentrations being associated with increased risk of invasive cancer. In the treatment of patients with BPH, the lipidic liposterolic extracts of Serenoa repens were as effective as the pharmaceutical inhibitors of the 5alpha-reductase enzyme or alpha1-adrenergic blockers in relieving urinary symptoms. In addition to moderately inhibiting the 5alpha-reductase activity, Serenoa seems to exert anti-inflammatory and complementary cellular actions with beneficial effects on the prostate. Unlike the pharmaceutical 5alpha-reductase inhibitors, finasteride and dutasteride, Serenoa does not suppress serum PSA, facilitating the follow-up and the early detection of prostate cancer. We suggest a strategy to prevent prostate cancer that aims at providing men with partial androgen deficiency correct testosterone substitution with a sustained release buccal bio-adhesive tablet. In addition, food supplementation with extracts of Serenoa repens and a combination of the antioxidants selenium, (cis)-lycopene and natural vitamin E, together with fish oil rich in long-chain polyunsaturated essential fatty acids of the omega-3 group seems warranted. Clearly, a holistic approach including careful clinical and biological monitoring of the aging man and his prostate remains mandatory.

Coexpression of hepatocyte growth factor and its receptor c-Met correlates with high MIB-1 proliferative index in malignant fibrous histiocytoma

Hepatocyte growth factor (HGF) is a multifunctional cytokine that variably affects cell motility, proliferation, and morphogenesis. Little information is currently available on the HGF and its receptor c-Met expression in malignant fibrous histiocytoma (MFH). We immunohistochemically investigated the HGF and c-Met expression in 43 MFH tissue specimens. Furthermore, the correlation of the HGF and c-Met expression with tumor proliferative activity assessed by MIB-1 indices was analyzed. Our results showed that positive cytoplasmic immunoreactivity for HGF and c-Met was identified in tumor cells in 36 (84%) and 20 (47%) of the 43 MFH cases analyzed, respectively. Coexpression of HGF and c-Met was observed in 20 (47%) of the 43 MFHs, and was correlated with high MIB-1 proliferative indices (p = 0.0446). These findings strongly indicate that the HGF/c-Met signaling system plays an important role in promoting cell proliferation of human MFHs via an autocrine loop.

The tumour-stromal interaction between intratumoral c-Met and stromal hepatocyte growth factor associated with tumour growth and prognosis in non-small-cell lung cancer patients

Immunohistochemical analyses of the effects of hepatocyte growth factor (HGF) and c-Met expression on tumour growth and angiogenesis were performed on 88 patients with non-small-cell lung cancers (NSCLCs). In all, 22 carcinomas (25.0%) were intratumoral HGF-positive, 14 carcinomas (15.9%) were stromal HGF-positive, and 36 carcinomas (40.9%) were intratumoral c-Met-positive. None of the carcinomas were stromal c-Met-positive. Examination of tumour growth revealed that the frequency of tumours with a high Ki-67 index was significantly greater for stromal HGF-positive tumours than for stromal HGF-negative tumours (P=0.0197). The frequency of tumours with a high Ki-67 index was also significantly greater for intratumoral c-Met-positive tumours than for intratumoral c-Met-negative tumours (P=0.0301). However, there was no significant difference in tumour vascularity with relation to intratumoral HGF status, stromal HGF status, and intratumoral c-Met status. The survival rate of patients with intratumoral c-Met-positive tumours was significantly lower than for patients with c-Met-negative tumours (P=0.0095). Furthermore, the survival rate of patients with both intratumoral c-Met-positive and stromal HGF-positive tumours was significantly lower than for patients with either positive tumours, and that of patients with both negative tumours (P=0.0183 and P=0.0011, respectively). A univariate analysis revealed that intratumoral c-Met expression was a significant prognostic factor of NSCLC patients (relative risk=2.642, P=0.0029). The present study demonstrates that tumour-stromal interaction between tumour cell-derived c-Met and stromal cell-derived HGF affects tumour growth and the prognosis of NSCLC patients.

Human prostate cancer risk factors

Prostate cancer has the highest prevalence of any nonskin cancer in the human body, with similar likelihood of neoplastic foci found within the prostates of men around the world regardless of diet, occupation, lifestyle, or other factors. Essentially all men with circulating androgens will develop microscopic prostate cancer if they live long enough. This review is a contemporary and comprehensive, literature-based analysis of the putative risk factors for human prostate cancer, and the results were presented at a multidisciplinary consensus conference held in Crystal City, Virginia, in the fall of 2002. The objectives were to evaluate known environmental factors and mechanisms of prostatic carcinogenesis and to identify existing data gaps and future research needs. The review is divided into four sections, including 1) epidemiology (endogenous factors [family history, hormones, race, aging and oxidative stress] and exogenous factors [diet, environmental agents, occupation and other factors, including lifestyle factors]); 2) animal and cell culture models for prediction of human risk (rodent models, transgenic models, mouse reconstitution models, severe combined immunodeficiency syndrome mouse models, canine models, xenograft models, and cell culture models); 3) biomarkers in prostate cancer, most of which have been tested only as predictive factors for patient outcome after treatment rather than as risk factors; and 4) genotoxic and nongenotoxic mechanisms of carcinogenesis. The authors conclude that most of the data regarding risk relies, of necessity, on epidemiologic studies, but animal and cell culture models offer promise in confirming some important findings. The current understanding of biomarkers of disease and risk factors is limited. An understanding of the risk factors for prostate cancer has practical importance for public health research and policy, genetic and nutritional education and chemoprevention, and prevention strategies.

Hepatocyte growth factor is essential for migration of myogenic cells and promotes their proliferation during the early periods of tongue morphogenesis in mouse embryos

Temporal and spatial occurrence of hepatocyte growth factor (HGF) and its cognate receptor c-Met in the mouse mandibular development was investigated by immunohistochemistry and quantitative reverse transcriptase-polymerase chain reaction. HGF was first recognized in the mesenchymal cells of the first branchial arch at the 10th day of gestation (E10), before tongue formation, whereas HGF receptor (c-Met) -positive myogenic cells first appeared at E11 in the center of mandibles. By E12, HGF turned to be colocalized with c-Met in the differentiating tongue myoblasts. Between E14 and E16, HGF disappeared, whereas c-Met remained, in the tongue myoblasts. The levels of HGF mRNA in the developing tongue decreased in accordance with the increase of desmin mRNA levels from E11 to E17. These in vivo results strongly suggest that the HGF/c-Met system takes part in the earlier stages of tongue development. To elucidate this hypothesis, the antisense oligodeoxyribonucleotide (A-ODN) for mouse HGF mRNA was added to the organ culture system of mandible with serumless, defined medium. Mandibular arches from E10 mouse embryos were cultured at 37 degrees C for 10 days in the absence or presence of A-ODN, control (sense) oligonucleotide (C-ODN), or A-ODN plus recombinant HGF. In the control mandibular explants cultured without HGF or ODN, the anterior two-third of the tongue derived from the first branchial arch was formed. It contained abundant desmin-positive myoblasts and was equivalent to the tongue of E14-E15. In contrast, in the presence of A-ODN in the medium, neither the swelling nor myogenic cells were found in the tongue-forming region of explants, and myogenic cells accumulated behind the tongue-forming region. Such dysplasia of tongue was never induced in the presence of C-ODN or A-ODN plus recombinant HGF in the medium. The effect of A-ODN appeared to be developmental stage-specific, because tongue dysplasia occurred when A-ODN was present during the earlier 4 days but not during the later 4 days of the culture. Furthermore, recombinant HGF added to the culture without ODNs during the earlier 4 days caused elevation in the number of mitotic myoblasts. These results suggest that HGF regulates both the migration and proliferation of myogenic cells during the earlier stages of tongue development.

Scatter factor-hepatocyte growth factor elevation in the serum of patients with prostate cancer

PURPOSE

Scatter factor (SF), also known as hepatocyte growth factor (HGF), has been shown to induce proliferation, scattering and invasiveness in human prostate cancer cell lines. In this study we determined the serum level of SF-HGF in men with metastatic prostate cancer compared to those with localized prostate cancer and without prostate cancer.

MATERIALS AND METHODS

Serum samples were obtained from men with biopsy proved adenocarcinoma of the prostate and radiographic evidence of metastatic disease, those with biopsy proved adenocarcinoma of the prostate and clinically localized disease, and those with negative sextant prostate biopsies. Serum SF-HGF was determined using a commercially available enzyme-linked immunosorbent assay kit.

RESULTS

Of the 108 men enrolled in our study 52 had negative sextant biopsies, 36 had clinically localized cancer and 20 had metastatic disease. The serum level in men with metastatic disease was significantly elevated (mean 2,117 pg./ml., range 820 to 6,403) compared to that in men with localized cancer and without prostate cancer (mean 974 pg./ml., range 437 to 2,132 and 700, range 272 to 1,875, respectively, p = 9.5 x 10(-15)). Logistic regression analysis demonstrated that the association of ln (SF-HGF) with prostate cancer persisted after controlling for patient age and ln (prostate specific antigen) (p = 3.1 x 10(-4)).

CONCLUSIONS

Serum SF-HGF is increased in men with metastatic prostate cancer. SF-HGF levels are associated with metastatic prostate cancer independent of the prostate specific antigen level and patient age. These data imply that SF-HGF may be an important serum marker for prostate cancer.

Expression of the hepatocyte growth factor/c-Met pathway is increased at the cancer front in breast carcinoma

Expression of hepatocyte growth factor (HGF) and c-Met (HGF receptor) has been reported in many neoplasms. We investigated coexpression of HGF and c-Met to determine the role of the HGF/c-Met pathway in breast carcinoma, especially at the cancer front. Eighty-eight cases of carcinoma of the breast were studied by immunohistochemistry and by in situ hybridization for HGF and c-Met expression. The staining pattern was termed "front accentuation pattern" when it was most conspicuous at the cancer front. HGF and c-Met proteins were expressed in cancer and stromal cells, with autocrine and paracrine patterns. The front accentuation pattern of c-Met was observed in cancer cells, but not in stromal cells. The front accentuation pattern was not observed in HGF. Coexpression of HGF and c-Met at the cancer front was correlated with histologic grade, reduced patient survival and a high Ki-67 labeling index. Our findings suggest that the HGF/c-Met pathway acts primarily as a mitogen, especially at the cancer front, in a paracrine manner and affects some clinical factors, including patient survival.

Overexpression and regulation of expression of scatter factor/hepatocyte growth factor in prostatic carcinoma

OBJECTIVES

Scatter factor (hepatocyte growth factor) (SF/HGF) is a multifunctional polypeptide growth factor that has been implicated in tumor proliferation, angiogenesis, invasiveness, and metastasis. Little is known of the expression of SF/HGF in human prostatic carcinoma. The aims of this investigation were to quantitate the level of SF/HGF expression in benign versus malignant human prostatic tissues and to assess regulation of SF/HGF expression by human prostatic stromal myofibroblasts.

METHODS

We determined the level of SF/HGF expression in 10 human prostatic tissue samples (5 benign, 5 carcinoma) by Western blot analysis. Five purified growth factors-basic fibroblast growth factor (bFGF), interleukin-1beta (IL-1beta), platelet-derived growth factor (PDGF), vascular endothelial growth factor (VEGF), and endothelial growth factor (EGF)-were tested for their capacity to induce SF/HGF expression by a human prostatic stromal myofibroblastic cell line, as assessed by enzyme-linked immunosorbent assay. Supernatant from the normal PrEC prostatic epithelial cell line and the DU 145 carcinoma cell line were assayed for SF/HGF-inducing activity.

RESULTS

SF/HGF exhibited a mean fourfold overexpression in carcinoma tissues compared with benign prostatic tissue. Significant stimulation of SF/HGF expression by prostatic stromal myofibroblasts was detected for IL-1beta (8.1-fold), PDGF (6.2-fold), bFGF (4.0-fold), VEGF (3. 7-fold), and EGF (2.9-fold). DU 145-conditioned media, but not the PrEC-conditioned media, contained SF/HGF-inducing activity, which was determined to include IL-1beta, bFGF, and PDGF by antibody-blocking experiments.

CONCLUSIONS

SF/HGF is overexpressed in human prostatic carcinoma tissues. Prostatic carcinoma cell stimulation of SF/HGF expression by adjacent benign myofibroblastic cells as a type of epithelial-stromal paracrine interaction could potentially influence prostatic carcinoma cell behaviors.

Hepatocyte growth factor secreted by prostate-derived stromal cells stimulates growth of androgen-independent human prostatic carcinoma cells

The objective of the present study is to examine the role of prostate stromal cells on growth and progression of prostate cancer. Co-inoculation of androgen-independent carcinoma cells (PC-3 and CA-7T2) with prostate-derived stromal (P-ST) cells significantly enhanced the growth of carcinoma cells in athymic nude mice. For the in vitro study, a three-dimensional co-culture system was used. It consisted of two layers of collagen gel. Stromal cells were suspended in the lower layer, whereas cancer cells were suspended in the upper layer. Compared to the control culture, the presence of P-ST cells in the lower collagen layer significantly stimulated the growth of carcinoma cells. Such an effect was not demonstrated when carcinoma cells were co-cultured with either bone marrow-derived or skin-derived stromal cells. We identified hepatocyte growth factor (HGF) as the principal growth factor released by P-ST cells but not by bone marrow-derived or skin-derived stromal cells. Neutralizing antibodies against HGF completely abrogated the stimulatory effect of P-ST cells. Exogenous HGF likewise stimulated the growth of carcinoma cells in vitro and in vivo. These results suggest that HGF produced by P-ST cells is a paracrine growth factor that stimulates the growth of androgen-independent prostate cancer cell lines.

Expression of membrane-type 1 matrix metalloproteinase (MT1-MMP) on prostate cancer cell lines

Membrane-type metalloproteinase-1 (MT1-MMP) is a transmembrane metalloproteinase, which activates proMMP-2 and expressed on the cell surface in many invasive cancer cells. We investigated the expression of MT1-MMP in prostate cancer cell lines. MT1-MMP protein and mRNA were expressed in PC-3, DU-145 and TSU-pr1 cells (androgen-independent prostate cancer cell lines), but in LNCaP cells (androgen-dependent prostate cancer cell line). MT1-MMP protein was negative and mRNA was low to detect by RT-PCR. Cell lysate of PC-3 cleaved proMMP-2 to the active form. In addition, both hepatocyte growth factor (HGF) and gastrin-releasing peptide (GRP) increased Matrigel invasion and induced the expression of MT1-MMP protein in DU-145 prostate cancer cells. These results suggest that MT1-MMP is indeed the tumor-specific activator of proMMP-2 in androgen-independent prostate cancer cells and plays an important role in the invasive properties of prostate cancer cells.

Expression of hepatocyte growth factor (HGF)/scatter factor and its receptor c-MET correlates with poor prognosis in synovial sarcoma

The hepatocyte growth factor (HGF)/c-MET signaling system plays an important role in the carcinogenesis of various organs. We investigated the expression of HGF and its receptor c-MET by immunohistochemistry (IHC) in 69 cases of synovial sarcoma and compared the findings with clinicopathologic parameters, proliferating activities evaluated by MIB-1 labeling index (MIB-1 LI), and patients' prognosis. Furthermore, mRNA analysis of HGF, c-MET, and SYT-SSX fusion gene was performed by reverse transcriptase-polymerase chain reaction (RT-PCR) in 22 concordant frozen materials. Twenty-one of 69 (30.4%) tumors showed positive reaction for c-MET, whereas 22 tumors (31.9%) were positive for HGF. In 10 cases, co-expression of HGF and c-MET was observed; however, there was no significant correlation between HGF and c-MET expression. HGF expression was correlated with female patients, large tumors (more than 5 cm), the presence of rhabdoid cells, low frequency of mast cells (<20/10 HPF), high nuclear grade (grade III), and high American Joint Committee (AJC) stage (III and IV). Conversely, c-MET expression was only correlated with large tumors. However, the coexpression of HGF and c-MET was significantly correlated with large tumor size, the existence of rhabdoid cells, and high AJC stage. Both the expression of HGF and the co-expression of HGF and c-MET showed a significantly high MIB-1 LI and were correlated with poor prognosis according to univariate analysis. Multivariate Cox analysis showed that high AJC stage, the expression of HGF, and a high MIB-1 LI (12.0>) independently had a negative impact on overall survival. In 22 frozen material cases evaluated by both IHC and RT-PCR, a statistically significant correlation was found between the 2 techniques. SYT-SSX fusion transcripts were detected in all 22 cases. Three tumors had SYT-SSX2 fusion transcripts, whereas 19 had SYT-SSX1 phenotype. Our results suggest that HGF/c-MET paracrine signaling may contribute to tumorigenesis and progression in synovial sarcoma.

Progression-linked overexpression of c-Met in prostatic intraepithelial neoplasia and latent as well as clinical prostate cancers

The c-met proto-oncogene encoding the receptor for the hepatocyte growth factor is expressed in several cancers. In the present study, c-met protein (c-Met) was detected in eight of 22 (36%) cases of prostatic intraepithelial neoplasia (PIN), five of 15 (33%) latent and 17 of 21 (81%) clinical prostate cancers, including seven metastatic lesions, using an immunohistochemical method. All seven (100%) metastatic lesions investigated demonstrated strong staining, and a correlation between c-Met expression and histology was observed. These results suggest a significant relationship between c-Met expression and progression of prostate neoplasms, including latent cancers.

Osteomimetic properties of prostate cancer cells: a hypothesis supporting the predilection of prostate cancer metastasis and growth in the bone environment

BACKGROUND

Unlike most other malignancies, prostate cancer metastasizes preferentially to the skeleton and elicits osteoblastic reactions.

METHODS

We present a hypothesis, based upon results obtained from our laboratory and others, on the nature of progression of prostate cancer cells and their predilection to growth and metastasis in the bone microenvironment. We propose the hypothesis that osseous metastatic prostate cancer cells must be osteomimetic in order to metastasize, grow, and survive in the skeleton. The reciprocal interaction between prostate cancer and bone stromal growth factors, including basic fibroblast growth factor (bFGF), hepatocyte growth factor/scatter factor (HGF/SF), and especially the insulin growth factor (IGF) axis initiates bone tropism, and is enhanced by prostate secreted endothelin-1 (ET-1) and urokinase-type plasminogen activator (uPA). Growth factors and peptides that have differentiating activity, such as transforming growth factor beta (TGF-beta), parathyroid hormone-related protein (PTH-rp), and the bone morphogenetic proteins (BMPs), can shift local homeostasis to produce the characteristic blastic phenotype, via interaction with prostate-secreted human kalikrein 2 (hK2), and prostate-specific antigen (PSA). This proposal asserts that altering the expression of certain critical transcription factors, such as Cbfa and MSX in prostate cancer cells, which presumably are under the inductive influences of prostate or bone stromal cells, can confer profiles of gene expression, such as osteopontin (OPN), osteocalcin (OC), and bone sialoprotein (BSP), that mimic that of osteoblasts.

RESULTS AND CONCLUSIONS

Elucidation of common proteins, presumably driven by the same promoters, expressed by both prostate cancer and bone stromal cells, could result in the development of novel preventive and therapeutic strategies for the treatment of prostate cancer skeletal metastasis. Agents developed using these strategies could have the potential advantage of interfering with growth and enhancing apoptosis in both prostate cancer and bone stromal compartments. The selective application of gene therapy strategy, driven by tissue-specific and tumor-restricted promoters for the safe delivery and expression of therapeutic genes in experimental models of prostate cancer metastasis, is discussed.