Institute of Molecular Animal Breeding and Biotechnology, Gene Center, LMU München, Germany.
Laboratory for Functional Genome Analysis (LAFUGA), Gene Center, LMU München, Germany.
Mol Oncol. 2021 Aug;15(8):2140-2155. doi: 10.1002/1878-0261.12945. Epub 2021 Mar 31.
The incidence of melanoma and nonmelanoma skin cancer has increased tremendously in recent years. Although novel treatment options have significantly improved patient outcomes, the prognosis for most patients with an advanced disease remains dismal. It is, thus, imperative to understand the molecular mechanisms involved in skin carcinogenesis in order to develop new targeted treatment strategies. Receptor tyrosine kinases (RTK) like the ERBB receptor family, including EGFR/ERBB1, ERBB2/NEU, ERBB3, and ERBB4, are important regulators of skin homeostasis and their dysregulation often results in cancer, which makes them attractive therapeutic targets. Members of the leucine-rich repeats and immunoglobulin-like domains protein family (LRIG1-3) are ERBB regulators and thus potential therapeutic targets to manipulate ERBB receptors. Here, we analyzed the function of LRIG1 during chemically induced skin carcinogenesis in transgenic mice expressing LRIG1 in the skin under the control of the keratin 5 promoter (LRIG1-TG mice). We observed a significant induction of melanocytic tumor formation in LRIG1-TG mice and no difference in papilloma incidence between LRIG1-TG and control mice. Our findings also revealed that LRIG1 affects ERBB signaling via decreased phosphorylation of EGFR and increased activation of the oncoprotein ERBB2 during skin carcinogenesis. The epidermal proliferation rate was significantly decreased during epidermal tumorigenesis under LRIG1 overexpression, and the apoptosis marker cleaved caspase 3 was significantly activated in the epidermis of transgenic LRIG1 mice. Additionally, we detected LRIG1 expression in human cutaneous squamous cell carcinoma and melanoma samples. Therefore, we depleted LRIG1 in human melanoma cells (A375) by CRISPR/Cas9 technology and found that this caused EGFR and ERBB3 downregulation in A375 LRIG1 knockout cells 6 h following stimulation with EGF. In conclusion, our study demonstrated that LRIG1-TG mice develop melanocytic skin tumors during chemical skin carcinogenesis and a deletion of LRIG1 in human melanoma cells reduces EGFR and ERBB3 expression after EGF stimulation.
近年来，黑色素瘤和非黑色素瘤皮肤癌的发病率急剧上升。尽管新的治疗选择显著改善了患者的预后，但大多数晚期患者的预后仍然不佳。因此，了解皮肤癌发生的分子机制对于开发新的靶向治疗策略至关重要。受体酪氨酸激酶（RTK），如表皮生长因子受体（EGFR/ERBB1）家族、ERBB2/NEU、ERBB3 和 ERBB4 等，是皮肤稳态的重要调节因子，其失调常导致癌症，这使其成为有吸引力的治疗靶点。富含亮氨酸重复序列和免疫球蛋白样结构域蛋白家族（LRIG1-3）的成员是 ERBB 调节剂，因此是操纵 ERBB 受体的潜在治疗靶点。在这里，我们在皮肤中表达 LRIG1 的转基因小鼠（LRIG1-TG 小鼠）中分析了 LRIG1 在化学诱导皮肤癌发生过程中的功能，LRIG1 的表达受角蛋白 5 启动子的控制。我们观察到 LRIG1-TG 小鼠中黑色素瘤形成明显增加，而 LRIG1-TG 小鼠和对照小鼠的乳头状瘤发生率没有差异。我们的研究结果还表明，LRIG1 通过减少 EGFR 的磷酸化和增加致癌蛋白 ERBB2 的激活，影响皮肤癌发生过程中的 ERBB 信号。在 LRIG1 过表达下，表皮肿瘤形成过程中表皮增殖率显著降低，转基因 LRIG1 小鼠表皮中的凋亡标志物 cleaved caspase 3 明显激活。此外，我们还在人类皮肤鳞状细胞癌和黑色素瘤样本中检测到了 LRIG1 的表达。因此，我们通过 CRISPR/Cas9 技术在人黑色素瘤细胞（A375）中耗尽 LRIG1，并发现 A375 LRIG1 敲除细胞在 EGF 刺激后 6 小时 EGFR 和 ERBB3 下调。总之，我们的研究表明，LRIG1-TG 小鼠在化学皮肤癌发生过程中会发展黑色素瘤皮肤肿瘤，而在人黑色素瘤细胞中缺失 LRIG1 会减少 EGF 刺激后 EGFR 和 ERBB3 的表达。
