Laura Possati

Basic fibroblast growth factor overexpression in endothelial cells: an autocrine mechanism for angiogenesis and angioproliferative diseases

Basic fibroblast growth factor (bFGF) is expressed in vascular endothelium during tumor neovascularization and angioproliferative diseases. The ultimate significance of this observation is poorly understood. We have investigated the biological consequences of endothelial cell activation by endogenous bFGF in a mouse aortic endothelial cell line stably transfected with a retroviral expression vector harboring a human bFGF cDNA. Selected clones expressing M(r) 24,000, M(r) 22,000, and/or M(r) 18,000 bFGF isoforms were characterized by a transformed morphology and an increased saturation density. bFGF transfectants showed invasive behavior and sprouting activity in three-dimensional fibrin gels and formed a complex network of branching cord-like structures connecting foci of infiltrating cells when seeded on laminin-rich basement membrane matrix (Matrigel). The invasive and morphogenetic behavior was prevented by anti-bFGF antibody, revealing the autocrine modality of the process. The biological consequences of this autocrine activation were investigated in vivo. bFGF-transfected cells gave rise to highly vascularized lesions resembling Kaposis sarcoma when injected in nude mice and induced angiogenesis in avascular rabbit cornea. When injected into the allantoic sac of the chick embryo, they caused an increase in vascular density and formation of hemangiomas in the chorioallantoic membrane. In conclusion, bFGF-overexpressing endothelial cells acquired an angiogenic phenotype and recruit quiescent endothelium originating angioproliferative lesions in vivo. These findings demonstrate that bFGF overexpression exerts an autocrine role for endothelial cells and support the notion that tumor neovascularization and angioproliferative diseases can be triggered by stimuli that induce vascular endothelium to produce its own autocrine factor(s).

An overview of the effect of linoleic and conjugated-linoleic acids on the growth of several human tumor cell lines.

Both n‐6 and n‐3 polyunsaturated fatty acids are dietary fats important for cell function, being involved in several physiologic and pathologic processes, such as tumorigenesis. Linoleic acid and conjugated linoleic acid, its geometrical and positional stereoisomer, were tested on several human tumor cell lines originating from different tissues and with different degrees of malignancy. This was to provide the widest possible view of the impact of dietary lipids on tumor development. While linoleic acid exerted different effects, ranging from inhibitory to neutral, even promoting growth, conjugated linoleic acid inhibited growth in all lines tested and was particularly effective against the more malignant cells, with the exception of mammary tumor cells, in which behavior was the opposite, the more malignant cell line being less affected. The inhibitory effect of conjugated linoleic acid on growth may be accompanied by different contributions from apoptosis and necrosis. The effects of conjugated linoleic acid on growth or death involved positive or negative variations in PPARs. The important observation is that a big increase of PPARα protein occurred in cells undergoing strong induction of apoptosis, whereas PPARβ/δ protein decreased. Although PPARα and PPARβ/δ seem to be correlated to execution of the apoptotic program, the modulation of PPARγ appears to depend on the type of tumor cell, increasing as protein content, when inhibition of cell proliferation occurred. In conclusion, CLA may be regarded as a component of the diet that exerts antineoplastic activity and its effect may be antiproliferative or pro‐apoptotic.

Cloning and characterization of a senescence inducing and class II tumor suppressor gene in ovarian carcinoma at chromosome region 6q27.

Cytogenetic, molecular and functional analysis has shown that chromosome region 6q27 harbors a senescence inducing gene and a tumor suppressor gene involved in several solid and hematologic malignancies. We have cloned at 6q27 and characterized the RNASE6PL gene which belongs to a family of cytoplasmic RNases highly conserved from plants, to man. Analysis of 55 primary ovarian tumors and several ovarian tumor cell lines indicated that the RNASE6PL gene is not mutated in tumor tissues, but its expression is significantly reduced in 30% of primary ovarian tumors and in 75% of ovarian tumor cell lines. The promoter region of the gene was unaffected in tumors cell lines. Transfection of RNASE6PL cDNA into HEY4 and SG10G ovarian tumor cell lines suppressed tumorigenicity in nude mice. When tumors were induced by RNASE6PL-transfected cells, they completely lacked expression of RNASE6PL cDNA. Tumorigenicity was suppressed also in RNASE6PL-transfected pRPcT1/H6cl2T cells, derived from a human/mouse monochromosomic hybrid carrying a human chromosome 6 deleted at 6q27. Moreover, 63.6% of HEY4 clones and 42.8% of the clones of XP12ROSV, a Xeroderma pigmentosum SV40-immortalized cell line, transfected with RNASE6PL cDNA, developed a marked senescence process during in vitro growth. We therefore propose that RNASE6PL may be a candidate for the 6q27 senescence inducing and class II tumor suppressor gene in ovarian cancer.

Promotion of tumour metastases and induction of angiogenesis by native HIV-1 Tat protein from BK virus/tat transgenic mice

ObjectiveTo characterize the T53 cell line and its clones derived from an adenocarcinoma of BK virus (BKV)/tat transgenic mice and to establish the role of native Tat in tumorigenicity, induction of metastases and angiogenesis. Design and methodsTat was quantified by flow cytometry and chloramphenicol acetyltransferase (CAT) assays. Tumorigenicity and metastatic ability of cell lines were assayed in nude mice. Production of proteases was evaluated by a plasmin chromogenic assay and gelatinase zymography. The angiogenic effect was studied in vivo with conditioned medium from tumour cell lines. ResultsTat protein was detected in tumour cell lines in amounts from 600–7000 molecules/cell. Conditioned medium from tumour cell lines was able to transactivate an LTR-CAT in HL3T1 cells, indicating release of extracellular Tat. Tumour cell lines, inoculated into nude mice, induced angiogenic tumours with remarkable recruitment of host endothelial cells. Metastases were detected in lymph nodes, lungs, kidneys, and heart. Cell lines produced relevant amounts of proteases. Conditioned medium implanted in mice with matrigel induced an angiogenic response, enhanced by addition of heparin. Preincubation with an anti-Tat antibody abolished the angiogenic effect. ConclusionsTat from cells from BKV/tat transgenic mice promotes tumorigenesis and formation of metastases and induces angiogenic activity. Angiogenesis occurs at physiological concentrations of Tat lower than 20 ng/ml. The effects of Tat on induction of metastases and angiogenesis appear to be mediated by activation of proteases.

Stable Transformation of Mouse, Rabbit and Monkey Cells and Abortive Transformation of Human Cells by BK Virus, a Human Papovavirus

Semi-permissive mouse, rabbit and monkey cells were stably transformed by BK virus (BKV). The specificity of transformation was demonstrated by the presence of BKV tumour (T) antigen in nuclei of transformed cells and by virus rescue with Sendai virus-mediated fusion or transfection. Two out of seven BKV-transformed cell lines were oncogenic. Permissive human cells were only abortively transformed by BKV, since morphologically modified cells persisted in culture for a few passages and eventually died.

Growth arrest and suppression of tumorigenicity of bladder carcinoma cell lines induced by the P16/CDKN2 (p16INK4A, MTS1) gene and other loci on human chromosome 9

Wild‐type P16/CDKN2 (p16INK4A, MTSI) cDNA, directed by the cytomegalovirus (CMV) immediate early promoter, was transfected into RT4 and RT112 bladder‐carcinoma cell lines bearing a mutated endogenous P16/CDKN2 gene and lacking endogenous P16/CDKN2 respectively. In both cases, only transfected clones with rearranged exogenous P16/CDKN2 cDNA could be grown and propagated in cell culture. This result is reminiscent of transfection of wild‐type p53 into cells with a deleted or mutated endogenous gene and suggests that P16/CDKN2, over‐expressed under control of the strong CMV promoter, induces growth arrest in RT4 and RT112 cells. Transfer of human chromosome 9 to RT4 cells produced RT4/H9 hybrid clones retaining the P16/CDKN2 gene, since in RT4/H9 cell clones P16/CDKN2‐gene expression is modulated by the physiological control of chromosomal regulatory sequences. All the RT4/H9 clones lost the entire chromosome 9, except clone 4 and clone 5, which maintained a deleted and an intact chromosome 9 respectively. Loss of several loci in 9p21, including P16/CDKN2, in tumors induced in nude mice by clone 4 and clone 5 suggests that P16/CDKN2 or other genes in 9p21 suppress tumorigenicity in bladder‐carcinoma cells. Tumors induced by clone 4 and clone 5 show loss of markers in 9q. The regions 9q22.3, 9q32–33 and 9q34.2, which were maintained in the 2 clones and lost in their derived tumors, may contain tumor‐suppressor genes relevant in bladder carcinoma. The results of this study suggest that the P16/CDKN2 gene controls growth of bladder‐carcinoma cells when it is over‐expressed, and may be involved in the development of bladder carcinoma, but other genes in 9p21 and 9q may participate in bladder‐cancer progression.

The role of peroxisome proliferator-activated receptor γ in bladder cancer in relation to angiogenesis and progression

Peroxisome proliferator-activated receptor gamma (PPAR gamma) immunohistochemical expression was analyzed in 75 human bladder tumor specimens, where the expression of some angiogenic factors, such as vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), platelet-derived endothelial cell growth factor (PDECGF), and tumor progression markers, such as epidermal growth factor receptor (EGFr), p16, mutated p53, and normal pRB, were also analyzed. The results were then compared to the clinical and pathological characteristics of the disease. PPAR gamma was expressed more significantly in papillary tumors than in solid cancers, and its presence was associated with statistical significance to low incidence of tumor recurrence or progression. This significant association was observed also when PPAR gamma was expressed in the presence of PDECGF, which resulted, when considered alone, to an angiogenic factor typical of solid cancers and appeared related to poor prognosis. In the presence of bFGF, on the contrary, PPAR gamma expression no longer resulted to a significant association with low incidence of tumor recurrence or progression, suggesting a possible worsening role of this angiogenic factor, typical of papillary cancers, in its interaction with PPAR gamma.

Antiangiogenic, antitumoural and antimetastatic effects of two distamycin A derivatives with anti-HIV-1 Tat activity in a Kaposi's sarcoma-like murine model

The antiangiogenic, antitumoural and antimetastatic effects of two novel sulphonic derivatives of distamycin A, PNU145156E and PNU153429, were studied in a Kaposi’s sarcoma-like tumour model obtained by injecting nude mice with cells releasing extracellular HIV-Tat protein, derived from a tumour which developed in a BK virus/tat transgenic mouse. Both PNU145156E and PNU153429 were administered intraperitoneally every fourth day for three weeks at doses of 100 or 50 mg/kg of body weight respectively, starting one day after injecting the tumour cells. Both drugs delayed tumour growth in nude mice, preventing neovascularization induced by the Tat protein. PNU153429 also significantly reduced the number and size of spontaneous tumour metastases. Both effects on tumour growth and metastases were augmented by treating simultaneously nude mice with 7.5 mg/kg of body weight of minocycline given per os daily for four weeks starting four days after injecting the tumour cells. Neither acute nor chronic toxic side-effects were observed during the life span of treated nude mice. Due to their antiangiogenic and anti-Tat effects, these drugs are promising for the treatment of Kaposi’s sarcoma in AIDS patients.

Antiangiogenic drugs for chemotherapy of bladder tumours.

Background: Bladder cancers have different angiogenic pathways distinguishing not only papillary from solid tumours, but even papillary superficial from papillary invasive ones, thus representing selective targets for antiangiogenic drugs. Methods: The bacterial wall component tecogalan, inhibiting basic fibroblast growth factor (bFGF), the fumagillin derivative TNP-470, inhibiting vascular endothelial growth factor (VEGF), the distamycin A derivative PNU153429, and the tetracycline minocycline were administered to nude mice injected with the human bladder cancer cell lines 639V, causing bFGF-expressing papillary superficial tumours, or T24, causing VEGF-expressing papillary invasive tumours. Results: Tecogalan had no effect even on 639V tumour growth, where bFGF was unaffected. TNP-470 only had an effect on T24 tumours, delaying tumour appearance and growth and lowering VEGF; these effects were augmented by adding minocycline. PNU153429 had no effect on 639V tumours, and a slight effect on T24 tumours. Conclusion: TNP-470 may represent a selective drug for the treatment of VEGF-expressing invasive papillary bladder tumours.