Stromal Expression of Connective Tissue Growth Factor Promotes Angiogenesis and Prostate Cancer Tumorigenesis

Abstract

Our previous studies have defined reactive stroma in human prostate cancer and have developed the differential reactive stroma (DRS) xenograft model to evaluate mechanisms of how reactive stroma promotes carcinoma tumorigenesis. Analysis of several normal human prostate stromal cell lines in the DRS model showed that some rapidly promoted LNCaP prostate carcinoma cell tumorigenesis and others had no effect. These differential effects were due, in part, to elevated angiogenesis and were transforming growth factor (TGF)-B1 mediated. The present study was conducted to identify and evaluate candidate genes expressed in prostate stromal cells responsible for this differential tumor-promoting activity. Differential cDNA microarray analyses showed that connective tissue growth factor (CTGF) was expressed at low levels in nontumorpromoting prostate stromal cells and was constitutively expressed in tumor-promoting prostate stromal cells. TGF-B1 stimulated CTGF message expression in nontumor-promoting prostate stromal cells. To evaluate the role of stromalexpressed CTGF in tumor progression, either engineered mouse prostate stromal fibroblasts expressing retroviral-introduced CTGF or 3T3 fibroblasts engineered with mifepristoneregulated CTGF were combined with LNCaP human prostate cancer cells in the DRS xenograft tumor model under different extracellular matrix conditions. Expression of CTGF in tumorreactive stroma induced significant increases in microvessel density and xenograft tumor growth under several conditions tested. These data suggest that CTGF is a downstream mediator of TGF-B1 action in cancer-associated reactive stroma and is likely to be one of the key regulators of angiogenesis in the tumor-reactive stromal microenvironment. (Cancer Res 2005; 65(19): 8887-95)

Fibroblast growth factor-2 mediates transforming growth factor-β action in prostate cancer reactive stroma

“…Concordantly, TGF-b1 induced smooth muscle a-actin filament formation in TbRII CT control cells; however, TbRII KO cells were refractory to TGF-b-induced filament formation (Figure 1b). Attenuated stromal TGF-b signaling in LNCaP þ stroma xenografts Construction of LNCaP/prostate stromal cell xenografts and evaluation time points followed protocols identical to what we have published previously (Tuxhorn et al, 2002b, c;Yang et al, 2005). Xenografts that were constructed with LNCaP plus TbRII KO stromal cells resulted in a 44.1% decrease in microvessel density (Po0.0001, n ¼ 72 fields from 12 xenografts in each group) and a 49.8% decrease in tumor mass compared to LNCaP plus TbRII CT control stromal cells ( Figure 3a) (Figures 7a and b) with subsequent experiments, Figure 7 shows histology for all xenografts in this study.…”

“…We believe that it is highly unlikely that FGF-2 is the only pathway downstream of TGF-b in stroma promoting LNCaP tumor growth, but that it does partially mediate the angiogenic action of TGF-b. In addition to FGF-2, TGF-b stimulates expression of many other growth factors in stromal cells including vascular endothelial growth factor, heparin-binding-epidermal growth factor, interleukin-6 TGF-b signaling in prostate cancer reactive stroma F Yang et al and CTGF (Igarashi et al, 1993;Pertovaara et al, 1994;Story et al, 1996;Uchiyama-Tanaka et al, 2002;Hayashi et al, 2004;Yang et al, 2005), some of which, similar to FGF2, are Smad3 regulated. Hence, focal overexpression of TGF-b at sites of early cancer might be expected to initiate a local reactive stroma, typified by matrix remodeling, induction of myofibroblasts, collagen deposition and induced angiogenesis, similar to the initiation of these events at sites of wound repair, where platelets release TGF-b.…”

“…In these studies we have shown that reactive stroma promotes experimental prostate cancer progression and much of this was due to stromal regulation of angiogenesis (Tuxhorn et al, 2002b). Using this same experimental xenograft model, we have also reported that both TGF-b and connective tissue growth factor (CTGF), a downstream mediator of TGF-b action, stimulate angiogenesis and promote tumorigenesis (Tuxhorn et al, 2002c;Yang et al, 2005). In contrast, under different conditions with different models and carcinoma/stromal cell lines, other studies showed that loss of TGF-b signaling in stroma resulted in elevated expression of tumor-promoting factors (TGF-a and HGF) and a net tumor progression (Bhowmick et al, 2004;Cheng et al, 2005).…”

“…We also showed that TGF-b could induce human prostate fibroblasts to a myofibroblast phenotype in vitro with elevated expression of tenascin, a marker of reactive stroma (Tuxhorn et al, 2002a). Our previous studies have developed a xenograft model (differential reactive stroma, DRS) that recombines LNCaP prostate carcinoma cells with engineered prostate stromal cells (Tuxhorn et al, 2002b, c;Yang et al, 2005). In these studies we have shown that reactive stroma promotes experimental prostate cancer progression and much of this was due to stromal regulation of angiogenesis (Tuxhorn et al, 2002b).…”

Connective tissue growth factor linked to the E7 tumor antigen generates potent antitumor immune responses mediated by an antiapoptotic mechanism

“…26 Its presence has been shown to be a survival factor for different cell types. 27,28 Previous studies have demonstrated that CTGF may also be a useful therapeutic agent in human rhabdomyosarcoma.…”