Ohnishi Yuichi, Yasui Hiroki, Kakudo Kenji, Nozaki Masami
Department of Cell Biology, Research Institute for Microbial Diseases, Osaka University, Suita, Osaka 565-0871, Japan.
Second Department of Oral and Maxillofacial Surgery, Osaka Dental University, Hirakata, Osaka 573-1121, Japan.
Oncol Rep. 2016 Nov;36(5):3058-3064. doi: 10.3892/or.2016.5073. Epub 2016 Sep 7.
Lapatinib, a dual inhibitor of epidermal growth factor receptor (EGFR)/ErbB2, has antiproliferative effects and is used to treat patients with ErbB2-positive metastatic breast cancer. In the present study, we examined the effects of lapatinib on growth of oral and prostate cancer cells. Oral squamous cell carcinoma (OSCC) cell lines HSC3, HSC4 and Ca9-22 were sensitive to the antiproliferative effects of lapatinib in anchorage-dependent culture, but the OSCC cell lines KB and SAS and the prostate cancer cell line DU145 were resistant to lapatinib. Phosphorylation levels of EGFR in all cell lines decreased during lapatinib treatment in anchorage‑dependent culture. Furthermore, the phosphorylation levels of ErbB2, ErbB3 and Akt and the protein levels of cyclin D1 were decreased by lapatinib treatment of HSC3, HSC4 and Ca9-22 cells. ErbB3 was not expressed and cyclin D1 protein levels were not altered by lapatinib treatment in KB, DU145 and SAS cells. The phosphorylation of ErbB2 and AKT was not affected by lapatinib in SAS cells and was not detected in KB and DU145 cells. Lapatinib-resistant cell lines exhibited sphere-forming ability, and SAS cells developed sensitivity to lapatinib during sphere formation. The phosphorylation levels of ErbB2 and AKT and protein levels of cyclin D2 increased during sphere formation of SAS cells and decreased with lapatinib treatment. In addition, sphere formation of SAS cells was inhibited by the AKT inhibitor MK2206. AKT phosphorylation and cyclin D2 levels in SAS spheres were decreased by MK2206 treatment. SAS cells expressed E-cadherin, but not vimentin and KB cells expressed vimentin, but not E-cadherin. DU145 cells expressed vimentin and E-cadherin. These results suggested that phosphorylation of EGFR and ErbB2 by cell detachment from the substratum induces the AKT pathway/cyclin D2-dependent sphere growth in SAS epithelial cancer stem-like cells, thereby rendering SAS spheres sensitive to lapatinib treatment.
拉帕替尼是一种表皮生长因子受体（EGFR）/ErbB2的双重抑制剂，具有抗增殖作用，用于治疗ErbB2阳性转移性乳腺癌患者。在本研究中，我们检测了拉帕替尼对口腔癌细胞和前列腺癌细胞生长的影响。口腔鳞状细胞癌（OSCC）细胞系HSC3、HSC4和Ca9-22在贴壁依赖性培养中对拉帕替尼的抗增殖作用敏感，但OSCC细胞系KB和SAS以及前列腺癌细胞系DU145对拉帕替尼耐药。在贴壁依赖性培养的拉帕替尼治疗期间，所有细胞系中的EGFR磷酸化水平均下降。此外，拉帕替尼处理HSC3、HSC4和Ca9-22细胞可降低ErbB2、ErbB3和Akt的磷酸化水平以及细胞周期蛋白D1的蛋白水平。在KB、DU145和SAS细胞中，拉帕替尼处理未表达ErbB3且未改变细胞周期蛋白D1蛋白水平。在SAS细胞中，拉帕替尼不影响ErbB2和AKT的磷酸化，在KB和DU145细胞中未检测到这种磷酸化。耐拉帕替尼的细胞系表现出成球能力，并且SAS细胞在成球过程中对拉帕替尼产生敏感性。在SAS细胞成球过程中，ErbB2和AKT的磷酸化水平以及细胞周期蛋白D2的蛋白水平升高，而拉帕替尼处理则使其降低。此外，AKT抑制剂MK2206可抑制SAS细胞的成球。MK2206处理可降低SAS球体中AKT磷酸化水平和细胞周期蛋白D2水平。SAS细胞表达E-钙黏蛋白，但不表达波形蛋白，而KB细胞表达波形蛋白，但不表达E-钙黏蛋白。DU145细胞表达波形蛋白和E-钙黏蛋白。这些结果表明，细胞从基质脱离导致的EGFR和ErbB2磷酸化可诱导SAS上皮癌干细胞样细胞中AKT途径/细胞周期蛋白D2依赖性球体生长，从而使SAS球体对拉帕替尼治疗敏感。
