Leptin-induced growth of human ZR-75-1 breast cancer cells is associated with up-regulation of cyclin D1 and c-Myc and down-regulation of tumor suppressor p53 and p21WAF1/CIP1

Abstract

Obesity has been recognized as a risk factor for breast cancer. Adipocyte-derived leptin may play as a paracrine regulator on the growth of breast cancer cells. Expression of both leptin and its OB-Rb receptor was detected in human breast cancer ZR-75-1 cells and further induced by leptin, suggesting that both expression and message mediation of leptin were autoregulated by itself. With cell counting and MTT assay, we had observed leptin stimulated ZR-75-1 growth in dose- and time-dependent manners. To study what steps of cell cycle progression leptin may involve in, we analyzed cell-cycle profile with flow cytometric analysis, mRNA and protein expressions of four cell-cycle regulators with RT-PCR and Western blotting analysis. Under the treatment of leptin, the G1 arrest of cells was reduced accompanied with up-regulation of G1 phase-specific cyclin D1 and proto-oncogene c-Myc, but down-regulation of cyclin-dependent kinase inhibitor p21(WAF1/CIP1) and tumor suppressor p53. Furthermore, JAK2 inhibitor AG490, PI3K/Akt inhibitor Wortmannin, and MEK/ERK1/2 inhibitor PD98059 were efficiently prevented leptin-promoted cell growth. Effect of cooperation between leptin and estrogen on ZR-75-1 growth had been observed. Collectively, the results showed that the proliferative effect of leptin on ZR-75-1 was associated with the up-regulation of cyclin D1 and c-Myc and down-regulation of tumor suppressor p53 and p21(WAF1/CIP1) plausibly through a hypothesized JAK2-PI3K/Akt-MEK/ERK pathway. The leptin- and OB-Rb-expressing capability of ZR-75-1 created a possible autocrine control of leptin, in which signal could be effectively amplified by itself, on cell growth.

Circulating levels of leptin, adiposity and breast cancer risk

“…Although leptin has been viewed as the hormonal signal for the regulation of energy homoeostasis (Auwerx and Staels, 1998), several lines of evidence suggest that leptin plays a much broader physiological role (Rosenbaum and Leibel, 1999;Zhang et al, 2005). On a cellular level, leptin has been found to act as a metabolic regulator and motogenic and pro-angiogenic factors (Sierra-Honignann et al, 1998;Hardwick et al, 2001;Hu et al, 2002;Chio et al, 2004;Yin et al, 2004;Chen et al, 2006a). In addition, new evidence suggests that leptin could be involved in tumorigenesis, especially in the development of breast, colorectal and prostate cancers .…”

IL‐1 family in breast cancer: Potential interplay with leptin and other adipocytokines

“…Numerous studies have demonstrated that leptin stimulates the proliferation of breast cancer cell lines [48][49][50][51]. The presence of leptin and its receptor (ObR) has been described in vitro in the normal human breast epithelial cell line MCF10A [17] and HBL100 [49] respectively, as well as in breast cancer cell lines [17,49,52].…”

Methylseleninic acid inhibits microvascular endothelial G1 cell cycle progression and decreases tumor microvessel density

“…PCR was performed using HotStarTaq Master Mix Kit and a pair of oligonucleotide primers respectively (Sigma-Genosys, The Woodlands, TX) as follows. The PCR amplification started with 95°C for 15 min, and then preceded accordingly with conditions for 18 ; P27/KIP1: Forward: 5 0 -ATG TCA AAC GTG CGA GTG TCT-3 0 , Reverse: 5 0 -TTA CGT TTG ACG TCT TCT GA-3 0 (95°C 30 sec, 57°C 1 min, 72°C 1.5 min, 30 cycles). 19 Five microliters of PCR products were fractionated in a 1.0% agarose gel containing ethidium bromide and visualized by UV illumination.…”