Alshaker Heba, Krell Jonathan, Frampton Adam E, Waxman Jonathan, Blyuss Oleg, Zaikin Alexey, Winkler Mathias, Stebbing Justin, Yagüe Ernesto, Pchejetski Dmitri
Breast Cancer Res. 2014 Oct 25;16(5):426. doi: 10.1186/s13058-014-0426-6.
Obesity is a known risk factor for breast cancer. Sphingosine kinase 1 (SK1) is an oncogenic lipid kinase that is overexpressed in breast tumours and linked with poor prognosis, however, its role in obesity-driven breast cancer was never elucidated.
Human primary and secondary breast cancer tissues were analysed for SK1 and leptin receptor expression using quantitative real-time polymerase chain reaction (qRT-PCR) assay. Leptin-induced signalling was analysed in human oestrogen receptor (ER)-positive and negative breast cancer cells using Western blotting, qRT-PCR and radiolabelling assays.
Our findings show for the first time that human primary breast tumours and associated lymph node metastases exhibit a strong correlation between SK1 and leptin receptor expression (Pearson R = 0.78 and R = 0.77, respectively, P <0.001). Both these genes are elevated in metastases of ER-negative patients and show a significant increase in patients with higher body mass index (BMI). Leptin induces SK1 expression and activation in ER-negative breast cancer cell lines MDAMB-231 and BT-549, but not in ER-positive cell lines. Pharmacological inhibition and gene knockdown showed that leptin-induced SK1 activity and expression are mediated by activation of extracellular signal-regulated kinases 1/2 (ERK1/2) and Src family kinase (SFK) pathways, but not by the major pathways downstream of leptin receptor (LEPR) - janus kinase 2 (JAK2) and signal transducer and activator of transcription 3 (STAT3). Src-homology 2 domain-containing phosphatase 2 (SHP2) appeared to be key to SK1 activation, and may function as an adaptor protein between SFKs and LEPR. Importantly, leptin-induced breast cancer cell proliferation was abrogated by SK1-specific small interfering RNA (siRNA).
Overall, our findings demonstrate a novel SFK/ERK1/2-mediated pathway that links leptin signalling and expression of oncogenic enzyme SK1 in breast tumours and suggest the potential significance of this pathway in ER-negative breast cancer.
肥胖是已知的乳腺癌风险因素。鞘氨醇激酶1(SK1)是一种致癌脂质激酶,在乳腺肿瘤中过度表达且与预后不良相关,然而,其在肥胖驱动的乳腺癌中的作用从未得到阐明。
使用定量实时聚合酶链反应(qRT-PCR)分析人原发性和继发性乳腺癌组织中SK1和瘦素受体的表达。使用蛋白质免疫印迹、qRT-PCR和放射性标记分析在人雌激素受体(ER)阳性和阴性乳腺癌细胞中瘦素诱导的信号传导。
我们的研究结果首次表明,人原发性乳腺肿瘤及相关淋巴结转移灶中SK1和瘦素受体表达之间存在强相关性(Pearson相关系数分别为R = 0.78和R = 0.77,P <0.001)。这两个基因在ER阴性患者的转移灶中升高,且在体重指数(BMI)较高的患者中显著增加。瘦素诱导ER阴性乳腺癌细胞系MDAMB - 231和BT - 549中SK1的表达和激活,但在ER阳性细胞系中则不然。药理学抑制和基因敲低表明,瘦素诱导的SK1活性和表达是由细胞外信号调节激酶1/2(ERK1/2)和Src家族激酶(SFK)途径的激活介导的,而非由瘦素受体(LEPR)下游的主要途径——janus激酶2(JAK2)和信号转导及转录激活因子3(STAT3)介导。含Src同源2结构域的磷酸酶2(SHP2)似乎是SK1激活的关键,并且可能作为SFK和LEPR之间的衔接蛋白发挥作用。重要的是,瘦素诱导的乳腺癌细胞增殖被SK1特异性小干扰RNA(siRNA)消除。
总体而言,我们的研究结果证明了一种新的SFK/ERK1/2介导的途径,该途径将瘦素信号传导与乳腺肿瘤中致癌酶SK1的表达联系起来,并提示该途径在ER阴性乳腺癌中的潜在重要性。