Department of Molecular Biology and Genetics, Koc University, Istanbul, Turkey.
J Cachexia Sarcopenia Muscle. 2022 Jun;13(3):1582-1594. doi: 10.1002/jcsm.12985. Epub 2022 Apr 4.
Lung cancer is the primary cause of cancer deaths worldwide. Activation of epidermal growth factor receptor (EGFR) leads to lung cancer progression and poor prognosis while involuntary weight loss remains a major problem. Tumour-derived parathyroid hormone-related protein (PTHrP) emerged as a potential mediator of cachexia. Here, we investigated the modulatory role of EGFR signalling in PTHrP (encoded by Pthlh) gene expression and the impact of this relationship on cancer cachexia.
Global gene expression profiles of Lewis lung carcinoma (LLC) cells were analysed. Pthlh mRNA levels were measured by qRT-PCR in LLC cells treated with EGFR ligands and tyrosine kinase inhibitors (TKIs). LLC tumour-bearing mice received EGFR TKI erlotinib for 7 days via intraperitoneal injection or oral gavage. Tumour Pthlh mRNA, weight of fat/muscle tissue, and grip strength were assessed. RNA-seq data from The Cancer Genome Atlas and gene expression analysis tools were used to characterize expression profiles of PTHLH and EGFR along with correlation analysis of PTHLH with EGFR and transforming growth factor alpha (TGFA) in human lung cancer and head and neck squamous carcinoma (HNSC). Survival of lung squamous cell carcinoma (LUSC) and lung adenocarcinoma (LUAD) patients with EGFR gene alterations was analysed in regard to PTHLH expression.
Expression of EGFR ligands, EGFR itself, and PTHrP co-clusters in LLC cells. Activation of EGFR signalling with its ligands significantly increases (3.8-fold, P < 0.0005) while EGFR TKIs significantly decrease (90%, P < 0.0005) Pthlh mRNA levels in LLC cells. Pthlh mRNA drops 65-75% (P < 0.0005) in tumours upon treatment of LLC tumour-bearing mice with erlotinib while their muscle mass and grip strength increase (9.2% P < 0.05, 23% P < 0.005, respectively) compared with tumour-bearing control mice. PTHLH is overexpressed in tumours of LUSC (45.8-fold, P < 0.05) and HNSC (17.5-fold, P < 0.05) compared with normal tissue. PTHLH expression correlates with EGFR and its ligand TGFA in both cancers (LUSC: n = 745, R = 0.32, P < 0.0001 and R = 0.51, P < 0.0001; HNSC: n = 545, R = 0.34, P < 0.001 and R = 0.50, P < 0.001, respectively). High PTHLH mRNA associates with poor overall survival in LUAD patients with activating EGFR mutations (n = 40, log-rank test, P = 0.0451).
Epidermal growth factor receptor signalling regulates expression of cachexia mediator PTHrP. EGFR inhibition reduces PTHrP expression in LLC tumours and ameliorates cachexia in LLC tumour-bearing mice.
肺癌是全球癌症死亡的主要原因。表皮生长因子受体 (EGFR) 的激活导致肺癌进展和预后不良，而体重非自愿减轻仍然是一个主要问题。肿瘤衍生的甲状旁腺激素相关蛋白 (PTHrP) 已成为恶病质的潜在介质。在这里，我们研究了 EGFR 信号在 PTHrP（由 Pthlh 编码）基因表达中的调节作用以及这种关系对癌症恶病质的影响。
分析了 Lewis 肺癌 (LLC) 细胞的全基因表达谱。用 qRT-PCR 测量 EGFR 配体和酪氨酸激酶抑制剂 (TKI) 处理的 LLC 细胞中的 Pthlh mRNA 水平。荷 LLC 肿瘤的小鼠通过腹腔内注射或口服给予 EGFR TKI 厄洛替尼 7 天。评估肿瘤 Pthlh mRNA、脂肪/肌肉组织重量和握力。使用癌症基因组图谱 (TCGA) 的 RNA-seq 数据和基因表达分析工具来表征人类肺癌和头颈部鳞状细胞癌 (HNSC) 中 PTHLH 和 EGFR 的表达谱，并进行 PTHLH 与 EGFR 和转化生长因子 alpha (TGFA) 的相关性分析。分析具有 EGFR 基因突变的肺鳞状细胞癌 (LUSC) 和肺腺癌 (LUAD) 患者的生存情况，以及 PTHLH 表达情况。
EGFR 配体、EGFR 本身和 PTHrP 在 LLC 细胞中共同聚类。用其配体激活 EGFR 信号可显著增加 (3.8 倍，P<0.0005)，而 EGFR TKI 可显著降低 (90%，P<0.0005) LLC 细胞中 Pthlh mRNA 水平。在 LLC 荷瘤小鼠中用厄洛替尼治疗时，肿瘤中的 Pthlh mRNA 下降 65-75%（P<0.0005），而其肌肉质量和握力增加（分别为 9.2% P<0.05，23% P<0.005）与荷瘤对照小鼠相比。与正常组织相比，LUSC（45.8 倍，P<0.05）和 HNSC（17.5 倍，P<0.05）肿瘤中 PTHLH 过度表达。PTHLH 表达与这两种癌症中的 EGFR 及其配体 TGFA 相关（LUSC：n=745，R=0.32，P<0.0001 和 R=0.51，P<0.0001；HNSC：n=545，R=0.34，P<0.001 和 R=0.50，P<0.001）。在具有激活 EGFR 突变的 LUAD 患者中，高 PTHLH mRNA 与总生存期不良相关（n=40，对数秩检验，P=0.0451）。
表皮生长因子受体信号调节恶病质介质 PTHrP 的表达。EGFR 抑制可降低 LLC 肿瘤中的 PTHrP 表达并改善 LLC 荷瘤小鼠的恶病质。
