The three-dimensional microvascular architecture of the human Kaposi sarcoma implanted in nude mice: a SEM corrosion casting study.

The human Kaposi sarcoma represents one of the most common skin lesions associated with AIDS. Its clinical presentation and anatomopathological structure seem to demonstrate a particularly rich vascularity. The latest therapies aim to limit its intrinsic angiogenic activity in an attempt to reduce vascular density and the formation of new vessels. For these reasons, we decided to study the microvascular architecture of Kaposi sarcoma in three dimensions. We used a corrosion casting technique applied to nude mice previously transplanted subcutaneously with human modified neoplastic Kaposi sarcoma cells. The cooption of host vessels made by the tumor was demonstrated by three-dimensional scanning electron microscopy (SEM) images. At high magnification several angiogenic patterns were observed in the form of potato-shaped vessels, sprouts, intussusceptions and mouse tailed end tipped capillaries along with some ultrastructural features such as intercellular extravasations and endothelial cell modifications. Our investigation allowed us to build a detailed map of tumor vasculature in human Kaposi sarcoma. Furthermore, this study want to shed light on the sharp morphological three-dimensional conformation of angiogenic sprouts so to be able to better understand their modifications occurred during time and after antiangiogenic experimental therapies, by now observed only by immunohistochemical or immunofluorescent assays.

TRAIL inhibits angiogenesis stimulated by VEGF expression in human glioblastoma cells.

Tumour growth is tightly related to new blood vessel formation, tissue remodelling and invasiveness capacity. A number of tissular factors fuel the growth of glioblastoma multiforme, the most aggressive brain neoplasm. In fact, gene array analyses demonstrated that the proapoptotic cytokine tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) inhibited mRNA expression of VEGF, along with those of matrix metalloproteinase-2 (MMP-2), its inhibitor tissue inhibitor of matrix metalloproteinases-2 (TIMP-2), as well as the tumour invasiveness-related gene secreted protein acid rich in cysteine (SPARC) in different human glioblastoma cell lines. Particularly, VEGF mRNA and protein expression and release from glioblastoma cells were also inhibited by TRAIL. The latter also exerted antimitogenic effects on human umbilical vein endothelial cells (HUVECs). With the same cells, TRAIL inhibited new vessel formation in the in vitro matrigel model, as well as it exerted powerful inhibition of blood vessel formation induced by an angiogenic cocktail administered in subcutaneous pellets in vivo in the C57 mouse. Moreover, the expression of MMP-2, its inhibitor TIMP-2 and the tumour invasiveness-related protein SPARC were effectively inhibited by TRAIL in glioblastoma cell lines. In conclusion, our data indicate that TRAIL inhibits the orchestra of factors contributing to glioblastoma biological aggressiveness. Thus, the TRAIL system could be regarded as a molecular target to exploit for innovative therapy of this type of tumour.

Are there CAG repeat expansion-related disorders outside the central nervous system?

Expansions of poly-glutamine tracts in proteins that are expressed in the central nervous system cause neurodegenerative diseases. The altered proteins accumulate over long periods of time, forming nuclear inclusions, and lead to neuronal cell death. A similar mechanism could also be operant in non-dividing cells outside the central nervous system because nuclear inclusions are not limited to neurons. In addition, variations of the repeat length within the normal range may affect cellular function as it has been shown for the androgen receptor that is involved in neoplastic degeneration of several tissues. We have identified a poly-glutamine/poly-proline repeat in the homeobox gene DLX6. DLX genes are expressed in non-proliferative cells of the apical ectodermal ridge of developing limbs. Ablation of these cells leads to limb malformation. We propose that CAG triplet expansions in this gene could lead to cell death in the apical ectodermal ridge causing limb malformations. Indeed, autosomal dominant limb malformations with increasing severity in successive generations have been linked to the chromosomal region that contains DLX6. The analysis of a limited number of patients affected by split hand/foot malformation so far revealed only a slight modifier effect of repeat length within the normal range and no expansions have been detected.

The coding region of the human DLX6 gene contains a polymorphic CAG/CCG repeat.

The region on chromosome 7q21-22 is frequently altered in several human neoplasias such as uterine leiomyoma, myeloid leukemia and breast cancer. The same region has also been linked to split hand/split foot malformation type 1 and to involutional osteoporosis. Our analysis of genes that map to this region has led to the identification of the so far unknown first exon of the homeobox gene DLX6, a mammalian homologue of the Drosophila distal-less gene. Distal-less is a downstream target of the trithorax transcription factors. Translocations involving the mammalian homologue of trithorax, ALL-1, leading to its constitutive activation cause leukemia. We describe here that the first exons of human and mouse DLX6 genes contain a multiple trinucleotide repeat region. We have analyzed the CAG repeat length in 90 subjects and were able to identify five alleles with 11 to 20 CAG repeats.

Somatic alterations of the androgen receptor CAG repeat in human colon cancer delineate a novel mutation pathway independent of microsatellite instability.

The human androgen receptor gene contains a polymorphic CAG repeat region ranging from 8 to about 35 repeats in the normal human population. The repeat length is inversely related to the transactivation potential of the receptor. We have analyzed the repeat length in 50 sporadic colon cancer samples in comparison to surrounding healthy mucosa and have found somatic reductions of up to 10 repeats in 5 cases (10%), 3 of which were complex, probably involving both alleles. Alterations occurred in tumors with and without microsatellite instability indicating that they follow an independent mutation pathway. The similar repeat of the huntingtin gene did not show any somatic alterations in the same cases. No correlation to sex, tumor stage, location, or histology was evident. In the tumors that showed somatic reductions, the reduced allele was present in at least half of the cells and thus in most, if not all, of the tumor component of the sample. Somatic reductions of the androgen receptor CAG repeat thus occur frequently, through a pathway distinct from microsatellite instability and early during colon carcinogenesis. The receptor is expressed in most normal and neoplastic tissue samples analyzed. Apparent growth selection of cells bearing shortened AR alleles suggests that androgens contribute to colon carcinogenesis in a yet unknown way.