Abstract
BackgroundSarcoids are peculiar equine benign tumours. Their onset is associated with Bovine Papillomavirus type -1 or -2 (BPV-1/2) infection. Little is known about the molecular interplay between viral infection and neoplastic transformation. The data regarding papillomavirus infections in human species show the inactivation of a number of tumour suppressor genes as basic mechanism of transformation. In this study the putative role of the tumour suppressor gene Fragile Histidine Triad (FHIT) in sarcoid tumour was investigated in different experimental models. The expression of the oncosuppressor protein was assessed in normal and sarcoid cells and tissue.ResultsNine paraffin embedded sarcoids and sarcoid derived cell lines were analysed for the expression of FHIT protein by immunohistochemistry, immunofluorescence techniques and western blotting. These analyses revealed the absence of signal in seven out of nine sarcoids. The two sarcoid derived cell lines too showed a reduced signal of the protein. To investigate the causes of the altered protein expression, the samples were analysed for the DNA methylation profile of the CpG island associated with the FHIT promoter. The analysis of the 32 CpGs encompassing the region of interest showed no significative differential methylation profile between pathological tissues and cell lines and their normal counterparts.ConclusionThis study represent a further evidence of the role of a tumour suppressor gene in equine sarcoids and approaches the epigenetic regulation in this well known equine neoplasm. The data obtained in sarcoid tissues and sarcoid derived cell lines suggest that also in horse, as in humans, there is a possible involvement of the tumour suppressor FHIT gene in BPV induced tumours. DNA methylation seems not to be involved in the gene expression alteration. Further studies are needed to understand the basic molecular mechanisms involved in reduced FHIT expression.
Highlights
In order to obtain new insights into BPV-mediated carcinogenesis, we investigated the status of Fragile Histidine Triad (FHIT) protein expression in equine sarcoid cell lines and sarcoid tumours
Sarcoids may exist as six different clinical types [5]; we have examined a limited number of samples, we suggest a lack of correlation between down-regulation of FHIT expression and clinical appearance, indicating a common mechanism underlying the reduction of protein expression acting early during the development of equine sarcoids
Biochemical and immunohistochemical analyses suggest that FHIT protein is often reduced in sarcoid tissues and cell lines
Summary
Their onset is associated with Bovine Papillomavirus type -1 or -2 (BPV-1/2) infection. Sarcoids are benign tumours of fibroblastic origin affecting the skin of horses, mules and donkeys and are considered to be the most common equine cutaneous neoplasm worldwide [1]. They are histologically characterized by disorganized dermal proliferation of spindleshaped fibroblasts that form whorls and by epidermal hyperplasia, hyperkeratosis, and rete peg formation [2,3]. FHIT is a well characterized tumour suppressor gene involved in the neoplastic transformation associated to the PVs infection [11]
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