LEPTIN RECEPTORS EXPRESSION IN MAMMARY TUMORS AND MAMMARY FAT PAD OF TRANSGENIC MAMMARY CANCER MOUSE MODEL.

Abstract

Background: Leptin is an adipokine encoded by the Ob (obese) gene and predominantly produced by adipocytes. The roles of both leptin and leptin receptor (ObR) in numerous pathophysiological conditions including mammary tumor (MT) development have been reported.

Aim: To examine protein expression levels of leptin and its receptors (ObR) including the long form, ObRb, in MT tissue and mammary fat pad of a transgenic mammary cancer mouse model. Further, we investigated whether the effects of leptin on MT development are systemic or local.

Materials and methods: MMTV-TGF-α transgenic female mice were fed ad libitum from week 10 up to week 74. Protein expression levels of leptin, ObR, and ObRb were measured in the mammary tissue samples of 74-week old MMTV-TGF-α mice with and without MT (MT-positive/MT-negative) by Western blot analysis. Serum leptin levels were measured by using the mouse adipokine LINCOplex kit 96-well plate assay.

Results: Protein expression levels of ObRb were significantly lower in MT as compared to control tissue of mammary gland. In addition, protein expression levels of leptin were significantly higher in the MT tissue of MT-positive mice compared to control tissue of MT-negative mice. However, ObR protein expression levels in tissues of mice with and without MT were similar. Serum leptin levels at different ages were not significantly different between the two groups.

Conclusion: Leptin and ObRb in the mammary tissue may play a critical role in the mammary cancer development, while contribution of short ObR isoform may be less important.