Expression of fibronectin and its integrin receptor alpha 5 beta 1 in canine mammary tumours

An Update on Molecular Pathways Regulating Vasculogenic Mimicry in Human Osteosarcoma and Their Role in Canine Oncology

Canine tumors are valuable comparative models for human counterparts, especially to explore novel biomarkers and to understand pathways and processes involved in metastasis. Vasculogenic mimicry (VM) is a unique property of malignant cancer cells which promote metastasis. Thus, it represents an opportunity to investigate both the molecular mechanisms and the therapeutic targets of a crucial phenotypic malignant switch. Although this biological process has been largely investigated in different human cancer types, including osteosarcoma, it is still largely unknown in veterinary pathology, where it has been mainly explored in canine mammary tumors. The presence of VM in human osteosarcoma is associated with poor clinical outcome, reduced patient survival, and increased risk of metastasis and it shares the main pathways involved in other type of human tumors. This review illustrates the main findings concerning the VM process in human osteosarcoma, search for the related current knowledge in canine pathology and oncology, and potential involvement of multiple pathways in VM formation, in order to provide a basis for future investigations on VM in canine tumors.

The relationship between clinicopathological features and expression of epithelial and mesenchymal markers in spontaneous canine mammary gland tumors

It is known that epithelial mesenchymal transition (EMT) contributes to the acquisition of malignant property in human cancers. However, the role of EMT in canine tumors remains to be elucidated. To evaluate the correlation between expression levels of protein markers involved in EMT and clinicopathological characteristics in canine mammary gland tumors, immunohistochemistry using antibodies against ZO-1, E-cadherin, vimentin, N-cadherin and fibronectin was performed on 119 clinical tissue samples. Consequently, loss of ZO-1 and E-cadherin, and gain of vimentin and N-cadherin were more frequently observed in malignant tumors than in benign tumors. However, there was no correlation among expression of these molecules. Univariate and multivariate analysis identified that loss of E-cadherin independently had a low one-year survival rate (adjusted odds ratio: 2.3, P=0.02). These results suggested that EMT might relate to acquisition of malignancy, and additionally, E-cadherin was strongly correlated with malignant behavior in canine mammary gland tumors.

Autocrine laminin-5 ligates alpha6beta4 integrin and activates RAC and NFkappaB to mediate anchorage-independent survival of mammary tumors

Invasive carcinomas survive and evade apoptosis despite the absence of an exogenous basement membrane. How epithelial tumors acquire anchorage independence for survival remains poorly defined. Epithelial tumors often secrete abundant amounts of the extracellular matrix protein laminin 5 (LM-5) and frequently express alpha6beta4 integrin. Here, we show that autocrine LM-5 mediates anchorage-independent survival in breast tumors through ligation of a wild-type, but not a cytoplasmic tail-truncated alpha6beta4 integrin. alpha6beta4 integrin does not mediate tumor survival through activation of ERK or AKT. Instead, the cytoplasmic tail of beta4 integrin is necessary for basal and epidermal growth factor-induced RAC activity, and RAC mediates tumor survival. Indeed, a constitutively active RAC sustains the viability of mammary tumors lacking functional beta1 and beta4 integrin through activation of NFkappaB, and overexpression of NFkappaB p65 mediates anchorage-independent survival of nonmalignant mammary epithelial cells. Therefore, epithelial tumors could survive in the absence of exogenous basement membrane through autocrine LM-5-alpha6beta4 integrin-RAC-NFkappaB signaling.

Expression of beta1 integrin in relation to histological features in normal and neoplastic canine testicles

The expression of the beta1 common chain of the VLA integrin subfamily was evaluated immunohistochemically in a series of five normal and 30 neoplastic canine testicles. The tumours, consisting of seminomas or Sertoli cell tumours, were classified according to WHO criteria as intraductal without signs of invasion, intraductal with signs of invasion, or diffuse. Expression of beta1 integrin decreased progressively from intraductal tumours without signs of invasion, to the diffuse type, in which immunolabelling was generally absent. In a few cases of diffuse neoplasia, groups of neoplastic cells exhibited strong positivity that was not restricted to the basal pole of the cell membrane. These results suggest that the expression of beta1 integrin was related to the histological tumour type, possibly reflecting a specific requirement for a reduction in integrin by neoplastic cells with infiltrative and metastatic potential.

Role of actin stress fibres in the development of the intervertebral disc: cytoskeletal control of extracellular matrix assembly

Orientation of collagen fibrils is a key event in the development of many tissues. In the intervertebral disc, the outer annulus fibrosus comprises lamellae of parallel collagen fibres, the direction of orientation of the long axis of which alternates in angle between lamellae. In development, this organisation is preceded by the formation of sheets of oriented fibroblasts, which then deposit the oriented lamellae. Here, using fluorescent labelling, confocal and electron microscopic techniques on developmental series, we show that the orientation of cells in lamellae is associated with the formation of adherens junctions intercellularly, involving cadherins and vinculin, and longitudinal stress fibres (label for filamentous actin and tropomyosin) intracellularly. The stress fibres direct the initial elongation of cells and control the deposition of oriented extracellular matrix via junctional complexes with the matrix involving vinculin and alpha 5 beta 1 integrins, which in turn promote the formation of oriented fibronectin at the cell surface; oriented collagen is deposited between cells at the same stages. Shortly after birth, the stress fibres disappear, probably because cells now gain orientational cues from the matrix, and are undergoing differentiation-related changes to form fibrocartilage cells. Dev Dyn 1999;215:179-189.

Developmental regulation of murine integrin beta 1 subunit- and Hsc73-encoding genes in mammary gland: sequence of a new mouse Hsc73 cDNA

A partial integrin beta 1 subunit-encoding cDNA (Itg beta 1) and a new heat-shock protein 70-like-encoding cDNA (Hsc73) homologous to rat Hsc73 were cloned by differential display and RT-PCR from mouse mammary gland. Their developmental regulation during pregnancy, lactation and involution is reported. The Itg beta 1 mRNA content was stable in the first half of gestation, decreased to a minimum during lactation and increased markedly in early involution. Hsc73 gene expression was high in the first half of gestation and decreased to a minimum during lactation. The possible significance of the two observed patterns of expression is discussed.