VEGF and 17-β-estradiol levels after tamoxifen administration in canine hepatoid gland adenomas and hepatoid gland epitheliomas.

The aim of the present study was to determine the serum levels of vascular endothelial growth factor in animals in the course of pharmacological treatment against perianal gland neoplasms. Research material comprised of tumor tissue samples obtained from 30 dogs and blood drawn from dogs with tumors and control group animals. The neoplasm type was determined in accordance with the relevant WHO classification. Immunoenzimatic determination of VEGF levels in the blood sera was performed. In all studied animals suffering from tumors, pharmacological tamoxifen treatment was administered, at a dosage of 2 mg/kg bodyweight. The medication was administered for one month. In order to monitor the serum levels of 17-β-estradiol and VEGF, blood was drawn from sick animals three times (on the day of the diagnosis, as well as at one and six months after treatment). The VEGF determination assay was performed in accordance with the manufacturer's guidelines for the ELISA. In the studied group, 12 animals were diagnosed with hepatoid gland adenomas and 18 with hepatoid gland epitheliomas. Elevated VEGF levels were observed in the group of dogs with hepatoid gland ephithelioma in comparison with the control group. In the studied groups, a decrease in serum VEGF level and a complete remission of neoplastic lesions was observed one month after administering tamoxifen. The VEGF levels in dogs with hepatoid gland adenoma continued to decline with time. In the case of dogs with hepatoid gland epithelioma, after the initial drop one month after treatment, a rapid increase of the growth factor level was observed, which was significantly higher in animals suffering a relapse of the neoplastic disease (50% of dogs). A significant correlation was observed between 17-β-estradiol and VEGF levels in dogs with hepatoid gland epithelioma on the day of diagnosis (Rxy=0.64, p<0.05) and six months after treatment (Rxy=0.54, p<0.05). Conclusion: VEGF overexpresion observed six months after tamoxifen treatment may constitute a prognostic factor in terms of the progression of the neoplastic process. The level of VEGF correlates with the level of 17-β-estradiol in serum. Apart from anti-estrogen effects, tamoxifen also demonstrates anti-angiogenic activity.