Leptin promotes proliferation and inhibits apoptosis of human breast cancer BT-474 and MDA-MB-231 cells by down-regulating the expression of FBP1 gene

Objective: To investigate the effects of leptin on the proliferation and apoptosis of human breast cancer BT-474 and MDA-MB-231 cells, and to explore its underlying molecular mechanism.  Methods: After treatment with 200 ng/mL leptin, the proliferation and apoptosis of BT-474 and MDA-MB-231 cells were measured by CCK-8 assay and FCM, respectively; the expression levels of proliferation- and apoptosis-associated proteins c-myc, cyclin D1, Bcl-2 and Bax were determined by Western blotting; while the levels of fructose-1, 6-bisphosphatase 1 (FBP1) mRNA and protein were detected by real-time fluorescent quantitative PCR and Western blotting, respectively. After the recombinant plasmids carrying FBP1 gene were transfected by liposome into BT-474 and MDA-MB-231 cells which were treated with 200 ng/mL leptin, the expression levels of FBP1 mRNA and protein were detected by real-time fluorescent quantitative PCR and Western blotting to verify the over-expression of FBP1 gene. Then, the proliferation abilities of BT-474 and MDA-MB-231 cells were measured by CCK-8 assay, the expression levels of proliferation-associated proteins c-myc and cyclin D1 were determined by Western blotting, the apoptosis rates of the two cell lines were detected by FCM, and the expression levels of apoptosis-associated proteins Bcl-2 and Bax were determined by Western blotting. Results: After treatment with 200 ng/mL leptin, the proliferation abilities of human breast cancer BT-474 and MDA-MB-231 cells were significantly increased (both P < 0.01); the expressions of proliferation-associated proteins c-myc and cyclin D1 were significantly up-regulated (both P < 0.01); while the apoptosis rates were apparently reduced (both P < 0.01); the expression of apoptosis-associated protein Bcl-2 was apparently up-regulated (P < 0.01), but the expression of Bax was apparently down-regulated (P < 0.01); the mRNA and protein levels of FBP1 in BT-474 and MDA-MB-231 cells were obviously down-regulated (both P < 0.05). However, after transfection with FBP1 over-expression plasmids, the expressions of FBP1 mRNA and protein were significantly up-regulated in BT-474 and MDA-MB-231 cells (both P < 0.01), while the effects of leptin on proliferation and apoptosis of BT-474 and MDA-MB-231 cells were dramatically reversed (all P < 0.01). Conclusion: Leptin promotes the proliferation and inhibits the apoptosis of human breast cancer BT-474 and MDA-MB-231 cells, and the potential mechanism may be related to the down-regulation of FBP1 gene expression. DOI:10.3781/j.issn.1000-7431.2017.11.080