Department of Biology, American University, Washington, DC, United States of America.
PLoS One. 2022 Mar 24;17(3):e0266017. doi: 10.1371/journal.pone.0266017. eCollection 2022.
Cutaneous squamous cell carcinoma (cSCC) is the second most common form of skin cancer in the United States, affecting one million people per year. Patients with aggressive disease have limited treatment options and high mortality, highlighting the need to identify new biomarkers linked to poor clinical outcome. HRAS mutations are found in skin papillomas and cSCCs and increase in frequency when MAP3K family members are inhibited, suggesting a link between blockade of mitogen-activated protein kinase (MAPK) signaling and initiation of RAS-primed cells. Tpl2, a MAP3K gene, can serve as a tumor suppressor gene in cSCC. We have previously shown that upon Tpl2 ablation, mice have heightened sensitivity to aberrant RAS signaling. Tpl2-/- mice display significantly higher numbers of papillomas and cSCCs in two-stage chemical carcinogenesis studies and increased tumorigenicity of keratinocytes expressing oncogenic v-rasHa in nude mouse skin grafts. In part, this is mediated through increased mesenchymal-epithelial transition factor (MET) receptor activity. Epidermal Growth Factor Receptor (EGFR) is reported to be an essential factor for MET-driven carcinogenesis and MET activation may confer resistance to EGFR therapies, suggesting that the concurrent use of both an EGFR inhibitor and a MET inhibitor may show promise in advanced cSCCs. In this study we assessed whether normal or Ras-transformed Tpl2-/- keratinocytes have aberrant EGFR signaling and whether concomitant treatment with EGFR/MET tyrosine kinase inhibitors was more effective than single agents in reducing growth and angiogenic potential of Ras-transformed keratinocytes. Tpl2-/- keratinocytes exhibited increased HER-2 and STAT-3 under basal conditions and elevated p-MET and p-EGFR when transduced with oncogenic RAS. Inhibition of MET by Capmatinib increased p-EGFR in Tpl2-/- keratinocytes and papillomas, and inhibition of EGFR by Gefitinib increased HER2 and HER3 signaling in both genotypes. Treatment of keratinocytes with EGFR and MET inhibitors, in combination, significantly enhanced endothelial tube formation, MMP-9 activity and activation of other RTKs, with more pronounced effects when Tpl2 was ablated. These data indicate that Tpl2 cross-talks with both EGFR and MET signaling pathways. Upon inhibition of EGFR/MET signaling, a myriad of escape mechanisms exists in keratinocytes to overcome targeted drug effects.
皮肤鳞状细胞癌 (cSCC) 是美国第二常见的皮肤癌，每年影响 100 万人。患有侵袭性疾病的患者治疗选择有限，死亡率高，这突出表明需要确定与不良临床结果相关的新生物标志物。HRAS 突变存在于皮肤乳头瘤和 cSCC 中，并且当 MAP3K 家族成员被抑制时频率增加，表明 MAPK 信号传导的阻断与 RAS 启动细胞的启动之间存在联系。Tpl2，一种 MAP3K 基因，在 cSCC 中可以作为肿瘤抑制基因。我们之前已经表明，在 Tpl2 缺失后，小鼠对异常 RAS 信号的敏感性增加。在两阶段化学致癌研究中，Tpl2-/- 小鼠显示出更高数量的乳头瘤和 cSCC，并且表达致癌 v-rasHa 的角质形成细胞在裸鼠皮肤移植物中的致瘤性增加。部分原因是通过增加间充质上皮转化因子 (MET) 受体活性。据报道，表皮生长因子受体 (EGFR) 是 MET 驱动的致癌作用的必需因素，并且 MET 激活可能赋予对 EGFR 治疗的抗性，这表明同时使用 EGFR 抑制剂和 MET 抑制剂可能在晚期 cSCC 中显示出希望。在这项研究中，我们评估了正常或 Ras 转化的 Tpl2-/- 角质形成细胞是否具有异常的 EGFR 信号，并且同时使用 EGFR/MET 酪氨酸激酶抑制剂是否比单一药物更有效地减少 Ras 转化的角质形成细胞的生长和血管生成潜力。在基础条件下，Tpl2-/- 角质形成细胞表现出增加的 HER-2 和 STAT-3，并且当转导致癌性 RAS 时，升高的 p-MET 和 p-EGFR。Capmatinib 抑制 MET 增加了 Tpl2-/- 角质形成细胞和乳头瘤中的 p-EGFR，Gefitinib 抑制 EGFR 增加了两种基因型的 HER2 和 HER3 信号。用 EGFR 和 MET 抑制剂联合治疗角质形成细胞显著增强了内皮管形成、MMP-9 活性和其他 RTK 的激活，当 Tpl2 缺失时效果更明显。这些数据表明 Tpl2 与 EGFR 和 MET 信号通路相互作用。在抑制 EGFR/MET 信号传导后，角质形成细胞中存在多种逃避机制来克服靶向药物的作用。
