Kunnimalaiyaan Muthusamy, Ndiaye Mary, Chen Herbert
Department of Surgery, Section of Endocrine Surgery, Endocrine Surgery Research Laboratories, The University of Wisconsin School of Medicine and Public Health, Madison, WI 53792, USA.
Surgery. 2006 Dec;140(6):1009-14; discussion 1014-5. doi: 10.1016/j.surg.2006.06.040. Epub 2006 Nov 1.
Medullary thyroid cancer (MTC) cells exhibit frequent activation of the PI3K pathway as evidenced by the presence of hyperactivation of Akt kinases and overexpression of neuroendocrine (NE) markers. We hypothesized that the inhibition of the PI3K pathway in MTC may lead to a reduction in cell growth and NE tumor marker production.
Human MTC-TT cells were treated with the PI3K inhibitor LY294002 (0-60 micromol/L) for 8 days, and cellular growth was measured. Further, TT cells were treated with nontoxic concentrations of LY294002 for 2 days, and Western blot analyses were performed for phospho-Akt, total Akt, and the NE tumor markers CgA and human achaete-scute homolog1 (ASCL1).
Treatment of TT cells with LY294002 significantly suppressed levels of phospho-Akt. Notably, a dose-dependent reduction in cellular proliferation was also observed. Importantly, NE marker production was also reduced. Mechanistically, we show that cell growth inhibition by PI3K inactivation is mediated by apoptosis attributable to an increase in the levels of cleaved poly(ADP-ribose) polymerase and caspase-3.
MTC cell growth and NE marker production appear to depend on activation of the PI3K-signaling cascade. Inhibition of this important signal transduction pathway may lead to a possible therapeutic strategy to treat patients with MTC.
甲状腺髓样癌（MTC）细胞中PI3K通路频繁激活，Akt激酶过度激活和神经内分泌（NE）标志物过表达证明了这一点。我们假设抑制MTC中的PI3K通路可能导致细胞生长和NE肿瘤标志物产生减少。
用PI3K抑制剂LY294002（0 - 60 μmol/L）处理人MTC - TT细胞8天，并测量细胞生长。此外，用无毒浓度的LY294002处理TT细胞2天，对磷酸化Akt、总Akt以及NE肿瘤标志物嗜铬粒蛋白A（CgA）和人无翅型MMTV整合位点家族成员1（ASCL1）进行蛋白质免疫印迹分析。
用LY294002处理TT细胞可显著抑制磷酸化Akt水平。值得注意的是，还观察到细胞增殖呈剂量依赖性降低。重要的是，NE标志物的产生也减少了。从机制上讲，我们表明PI3K失活对细胞生长的抑制作用是由凋亡介导的，这归因于裂解的聚（ADP - 核糖）聚合酶和半胱天冬酶 - 3水平的增加。
MTC细胞生长和NE标志物产生似乎依赖于PI3K信号级联的激活。抑制这一重要的信号转导通路可能为治疗MTC患者带来一种可行的治疗策略。
