Adenovirus-mediated expression of a soluble fibroblast growth factor receptor inhibits in vitro growth of prostate DU145 cells

Colony-stimulating factor 1 potentiates lung cancer bone metastasis

Colony-stimulating factor 1 (CSF1) is essential for osteoclastogenesis that mediates osteolysis in metastatic tumors. Patients with lung cancer have increased CSF1 in serum and high levels are associated with poor survival. Adenocarcinomas metastasize rapidly and many patients suffer from bone metastasis. Lung cancer stem-like cells sustain tumor growth and potentiate metastasis. The purpose of this study was to determine the role of CSF1 in lung cancer bone metastasis and whether inhibition of CSF1 ameliorates the disease. Human lung adenocarcinoma A549 cells were examined in vitro for CSF1/CSF1R. A549-luc cells were injected intracardiac in NOD/SCID mice and metastasis was assessed. To determine the effect of CSF1 knockdown (KD) in A549 cells on bone metastasis, cells were stably transfected with a retroviral vector containing short-hairpin CSF1 (KD) or empty vector (CT). Results showed that A549 cells express CSF1/CSF1R; CSF1 increased their proliferation and invasion, whereas soluble CSF1R inhibited invasion. Mice injected with A549-luc cells showed osteolytic bone lesions 3.5 weeks after injection and lesions increased over 5 weeks. Tumors recapitulated adenocarcinoma morphology and showed osteoclasts along the tumor/bone interface, trabecular, and cortical bone loss. Analyses of KD cells showed decreased CSF1 protein levels, reduced colony formation in soft agar assay, and decreased fraction of stem-like cells. In CSF1KD mice, the incidence of tumor metastasis was similar to controls, although fewer CSF1KD mice had metastasis in both hind limbs. KD tumors showed reduced CSF1 expression, Ki-67+ cells, and osteoclasts. Importantly, there was a low incidence of large tumors >0.1 mm(2) in CSF1KD mice compared with control mice (10% vs 62.5%). This study established a lung osteolytic bone metastasis model that resembles human disease and suggests that CSF1 is a key determinant of cancer stem cell survival and tumor growth. Results may lead to novel strategies to inhibit CSF1 in lung cancer and improve management of bone metastasis.

WITHDRAWN: Interaction of FGF1 with a novel anti-angiogenic drug SSR128129E

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Antitumor activity of a recombinant soluble ectodomain of mutant human fibroblast growth factor receptor-2 IIIc

The fibroblast growth factor (FGF) signaling pathway is a recognized target of cancer therapy. We have developed a strong inhibitor (S252W mutant soluble ectodomain of FGF recptor-2 IIIc, msFGFR2) that binds FGFs and blocks the activation of FGFRs. Thermodynamic binding studies indicated that msFGFR2 bound FGF-2 16.9 times as strongly as wild-type soluble FGFR2IIIc ectodomain (wsFGFR2). It successfully suppressed the growth, angiogenesis, and metastasis of two tumor cell lines in vitro and in vivo, and it potently inhibited cancer cell proliferation but not normal cell proliferation. Therefore, msFGFR2 is a useful probe for FGF-dependent signaling pathways and a potential broad-spectrum antitumor agent.

The effect of tyrosine kinase inhibitors, tyrphostins: AG1024 and SU1498, on autocrine growth of prostate cancer cells (DU145)

It is well established that autocrine growth of human prostate cancer cell line DU145 is dependent on TGF (EGF)/EGFR loop. However, the participation of several other growth factors in proliferation of DU145 cells has been also proposed. We employed two selective tyrosine kinase inhibitors (tyrphostins): AG1024 (an IGFIR inhibitor) and SU1498 (a VEGFR2 inhibitor) for growth regulation of DU145 cells, cultured in chemically defined DMEM/F12 medium. Both the tested compounds inhibited autocrine growth of DU145 cells at similar concentration values (IC50 approximately 2.5 microM). The tyrphostins arrested cell growth of DU145 in G1 phase, similarly as inhibitors of EGFR. However, in contrast to selective inhibitors of EGFR, neither AG1024, nor SU1498 (at concentration < or =10 microM) decreased the viability of the investigated cells. These results strongly suggest that autocrine growth of DU145 cells is stimulated by, at least, three autocrine loops: TGFalpha(EGF)/EGFR, IGFII/IGFIr and VEGF/VEGFR2(VEGFR1). These data support the hypothesis of multi-loops growth regulation of metastatic prostate cancer cell lines.

Androgen-response elements in hormone-refractory prostate cancer: implications for treatment development

Many attempts have been made to derive genetic signatures for progressive prostate cancer for both prognostic and therapeutic purposes. These investigations have resulted in the discovery of many pathways, but the signatures exhibit heterogeneity and restricted reproducibility. A thorough and disciplined analysis of genes with androgen-response elements that are expressed in progressive, castration-resistant prostate cancer is an integral step towards the development of new therapeutic or diagnostic targets. We discuss the effects of bona-fide downstream targets of the androgen receptor on cellular proliferation, evasion of apoptosis, and angiogenesis, and consider the clinical potential of these targets.

Identification of a fibroblast growth factor receptor 1 splice variant that inhibits pancreatic cancer cell growth

Fibroblast growth factor receptors (FGFR) play important roles in many biological processes. Nothing is presently known about possible roles of the human FGFR1-IIIb mRNA splice variant. In this study, we characterized for the first time the effects of FGFR1-IIIb expression on the transformed phenotype of human pancreatic cancer cells. The full-length FGFR1-IIIb cDNA was generated and stably expressed in PANC-1 and MIA PaCa-2 pancreatic cancer and TAKA-1 pancreatic ductal cells. FGFR1-IIIb-expressing cells synthesized a glycosylated 110-kDa protein enhancing tyrosine phosphorylation of FGFR substrate-2 on FGF-1 stimulation. The basal anchorage-dependent and anchorage-independent cell growth was significantly inhibited. These effects were associated with a marked reduction of p44/42 mitogen-activated protein kinase (MAPK) phosphorylation in combination with enhanced activity of p38 MAPK and c-Jun NH(2)-terminal kinase. FGFR1-IIIb expression inhibited single-cell movement and in vitro invasion as determined by time-lapse microscopy and Boyden chamber assay as well as in vivo tumor formation and growth in nude mice. Microscopic analysis of the xenograft tumors revealed a reduced Ki-67 labeling and a lower amount of tumor necrosis in FGFR1-IIIb-expressing tumors. Our results show that FGFR1-IIIb is a functional FGFR that inhibits the transformed phenotype of human pancreatic cancer cells.

Specific positive and negative effects of FLIP on cell survival in human prostate cancer

We demonstrate here for the first time novel positive and negative effects of the FLICE-like inhibitory protein (FLIP) on human prostate cancer cell survival. A proteaosome inhibitor, MG132, mediated cell cycle arrest at G2/M and apoptosis through p38 activation. Interestingly, FLIP was stabilized by MG132 and interacted with Raf-1, resulting in enhancement of p38 signals and cytotoxicity. In contrast, overexpression of FLIP inhibited ubiquitylation and proteasomal degradation of beta-catenin, resulting in increase of the target gene cyclin D1, colony formation and invasive activity. Immunohistochemical analysis and in vitro experiments in primary culture showed FLIP to be overexpressed, statistically associated with expression of beta-catenin/cyclin D1 in metastatic cells, the FLIP/beta-catenin/cyclin D1 signals contributing to colony formation and invasion, which were canceled by FLIP knock down. In contrast, MG132-induced cytotoxicity including apoptosis was strongly inhibited by reduction of FLIP. Taken together, the results indicate that FLIP plays an important role in development of metastatic prostate cancer by inhibiting proteasomal degradation of beta-catenin, whereas it is mainly involved in proteasome inhibitior-mediated cell cycle arrest and apoptosis through activating the Raf-1/p38 pathway. Furthermore, proteasome inhibitors may be effective drugs for advanced prostate cancers overexpressing FLIP.

Gene delivery and gene therapy of prostate cancer

Surgery, radiation or hormonal therapy are not adequate to control prostate cancer. Clearly, other novel treatment approaches, such as gene therapy, for advanced/recurrent disease are desperately needed to achieve long-term local control and particularly to develop effective systemic therapy for metastatic prostate cancer. In the last decade, significant progress in gene therapy for the treatment of localised prostate cancer has been demonstrated. A broad range of different gene therapy approaches, including cytolytic, immunological and corrective gene therapy, have been successfully applied for prostate cancer treatment in animal models, with translation into early clinical trials. In addition, a wide variety of viral and nonbiological gene delivery systems are available for basic and clinical research. Gene therapy approaches that have been developed for the treatment of prostate cancer are summarised.

Evaluation of the fibroblast growth factor system as a potential target for therapy in human prostate cancer

Overexpression of fibroblast growth factors (FGFs) has been implicated in prostate carcinogenesis. FGFs function via their high-affinity interactions with receptor tyrosine kinases, FGFR1–4. Expression of FGFR1 and FGFR2 in prostate cancer (CaP) was not found to be associated with clinical parameters. In this report, we further investigated for abnormal FGFR expression in prostate cancer and explore their significance as a potential target for therapy. The expression levels of FGFR3 and FGFR4 in CaP were examined and corroborated to clinical parameters. FGFR3 immunoreactivity in benign prostatic hyperplasia (BPH) and CaP (n=26 and 57, respectively) had similar intensity and pattern. Overall, FGFR4 expression was significantly upregulated in CaP when compared to BPH. A significant positive correlation between FGFR4 expression and Gleason score was noted: Gleason score 7–10 tumours compared to BPH (P<0.0001, Fisher's exact test), Gleason score 4–6 tumours compared to BPH (P<0.0004), and Gleason 7–10 compared to Gleason 4–6 tumours (P<0.005). FGFR4 overexpression was associated with an unfavourable outcome with decreased disease-specific survival (P<0.04, log rank test). FGF-induced signalling is targeted using soluble FGF receptor (sFGFR), potent inhibitor of FGFR function. We have previously shown that sFGFR expression via a replication-deficient adenoviral vector (AdlllcRl) suppresses in vitro FGF-induced signalling and function in human CaP DU145 cells. We tested the significance of inhibiting FGF function along with conventional therapeutic modalities in CaP, and confirmed synergistic effects on in vitro cell growth (proliferation and colony formation) by combining sFGFR expression and treatment with either Paclitaxel (Taxol®) or γ-irradiation. In summary, our data support the model of FGF system as valid target for therapy in CaP.