Cell Biology and Biotherapy Unit; Istituto Nazionale per lo Studio e la Cura dei Tumori "Fondazione Giovanni Pascale"; IRCCS; Naples, Italy.
The Hormel Institute; University of Minnesota; Austin, MN USA.
Cell Cycle. 2014;13(1):148-56. doi: 10.4161/cc.26899. Epub 2013 Oct 29.
Lapatinib is a dual EGFR and ErbB-2 tyrosine kinase inhibitor that has significantly improved the clinical outcome of ErbB-2-overexpressing breast cancer patients. However, patients inexorably develop mechanisms of resistance that limit the efficacy of the drug. In order to identify potential targets for therapeutic intervention in lapatinib-resistant patients, we isolated, from ErbB-2-overexpressing SK-Br-3 breast cancer cells, the SK-Br-3 Lap-R-resistant subclone, which is able to routinely grow in 1 µM lapatinib. Resistant cells have a more aggressive phenotype compared with parental cells, as they show a higher ability to invade through a matrigel-coated membrane. Lapatinib-resistant cells have an increased Src kinase activity and persistent levels of activation of ERK1/2 and AKT compared with parental cells. Treatment with the Src inhibitor saracatinib in combination with lapatinib reduces AKT and ERK1/2 phosphorylation and restores the sensitivity of resistant cells to lapatinib. SK-Br-3 Lap-R cells also show levels of expression of CXCR4 that are higher compared with parental cells and are not affected by Src inhibition. Treatment with saracatinib or a specific CXCR4 antibody reduces the invasive ability of SK-Br-3 Lap-R cells, with the two drugs showing cooperative effects. Finally, blockade of Src signaling significantly increases TRAIL-induced cell death in SK-Br-3 Lap-R cells. Taken together, our results demonstrate that breast cancer cells with acquired resistance to lapatinib have a more aggressive phenotype compared with their parental counterpart, and that Src signaling and CXCR4 play an important role in this phenomenon, thus representing potential targets for therapeutic intervention in lapatinib-resistant breast cancer patients.
拉帕替尼是一种双重 EGFR 和 ErbB-2 酪氨酸激酶抑制剂，显著改善了 ErbB-2 过表达乳腺癌患者的临床预后。然而，患者不可避免地会产生耐药机制，限制了药物的疗效。为了确定拉帕替尼耐药患者治疗干预的潜在靶点，我们从 ErbB-2 过表达的 SK-Br-3 乳腺癌细胞中分离出 SK-Br-3 Lap-R 耐药亚克隆，该亚克隆能够在 1 μM 拉帕替尼常规生长。与亲本细胞相比，耐药细胞具有更具侵袭性的表型，因为它们显示出更高的通过基质胶包被膜侵袭的能力。与亲本细胞相比，拉帕替尼耐药细胞具有更高的Src 激酶活性和持续激活 ERK1/2 和 AKT 的水平。用 Src 抑制剂 saracatinib 联合拉帕替尼治疗可降低 AKT 和 ERK1/2 磷酸化，并恢复耐药细胞对拉帕替尼的敏感性。与亲本细胞相比，SK-Br-3 Lap-R 细胞还表现出更高水平的 CXCR4 表达，并且不受 Src 抑制的影响。用 saracatinib 或特异性 CXCR4 抗体治疗可降低 SK-Br-3 Lap-R 细胞的侵袭能力，两种药物表现出协同作用。最后，阻断 Src 信号显著增加了 SK-Br-3 Lap-R 细胞中 TRAIL 诱导的细胞死亡。总之，我们的结果表明，获得拉帕替尼耐药的乳腺癌细胞与亲本细胞相比具有更具侵袭性的表型，Src 信号和 CXCR4 在这种现象中起重要作用，因此代表了拉帕替尼耐药乳腺癌患者治疗干预的潜在靶点。
