Princess Margaret Cancer Centre, University Health Network, Toronto, Ontario, Canada.
Princess Margaret Cancer Centre, University Health Network, Toronto, Ontario, Canada; Department of Thoracic Surgery Institute of Development, Aging and Cancer, Tohoku University, Sendai, Japan.
J Thorac Oncol. 2022 Feb;17(2):277-288. doi: 10.1016/j.jtho.2021.09.008. Epub 2021 Oct 12.
Mutations in BRAF occur in 2% to 4% of patients with lung adenocarcinoma. Combination dabrafenib and trametinib, or single-agent vemurafenib is approved only for patients with cancers driven by the V600E BRAF mutation. Targeted therapy is not currently available for patients harboring non-V600 BRAF mutations.
A lung adenocarcinoma patient-derived xenograft model (PHLC12) with wild-type and nonamplified EGFR was tested for response to EGFR tyrosine kinase inhibitors (TKIs). A cell line derived from this model (X12CL) was also used to evaluate drug sensitivity and to identify potential drivers by small interfering RNA knockdown. Kinase assays were used to test direct targeting of the candidate driver by the EGFR TKIs. Structural modeling including, molecular dynamics simulations, and binding assays were conducted to explore the mechanism of off-target inhibition by EGFR TKIs on the model 12 driver.
Both patient-derived xenograft PHLC12 and the X12CL cell line were sensitive to multiple EGFR TKIs. The BRAF mutation was found to be the only known oncogenic mutation in this model. Small interfering RNA knockdown of BRAF, but not the EGFR, killed X12CL, confirming BRAF as the oncogenic driver. Kinase activity of the BRAF protein isolated from X12CL was inhibited by treatment with the EGFR TKIs gefitinib and osimertinib, and expression of BRAF in non-EGFR-expressing NR6 cells promoted growth in low serum condition, which was also sensitive to EGFR TKIs. Structural modeling, molecular dynamic simulations, and in vitro binding assays support BRAF being a direct target of the TKIs.
Clinically approved EGFR TKIs can be repurposed to treat patients with non-small cell lung cancer harboring the BRAF mutation.
BRAF 突变发生在 2%至 4%的肺腺癌患者中。达拉非尼联合曲美替尼，或单药维莫非尼仅批准用于 V600E BRAF 突变驱动的癌症患者。目前尚无针对携带非 V600 BRAF 突变的患者的靶向治疗。
对具有野生型和非扩增 EGFR 的肺腺癌患者衍生的异种移植模型（PHLC12）进行了针对 EGFR 酪氨酸激酶抑制剂（TKI）的反应测试。还使用源自该模型的细胞系（X12CL）来评估药物敏感性，并通过小干扰 RNA 敲低来鉴定潜在的驱动因素。激酶测定用于测试候选驱动因素是否被 EGFR TKI 直接靶向。进行结构建模，包括分子动力学模拟和结合测定，以探索 EGFR TKI 对模型 12 驱动因素的非靶标抑制的机制。
患者衍生的异种移植 PHLC12 和 X12CL 细胞系均对多种 EGFR TKI 敏感。该模型中仅发现 BRAF 突变是已知的致癌突变。BRAF 的小干扰 RNA 敲低，但不是 EGFR，可杀死 X12CL，证实 BRAF 是致癌驱动因素。用 EGFR TKI 吉非替尼和奥希替尼处理 X12CL 分离的 BRAF 蛋白的激酶活性被抑制，并且在不表达 EGFR 的 NR6 细胞中表达的 BRAF 促进低血清条件下的生长，这也对 EGFR TKI 敏感。结构建模、分子动力学模拟和体外结合测定支持 BRAF 是 TKI 的直接靶标。
临床批准的 EGFR TKI 可重新用于治疗携带 BRAF 突变的非小细胞肺癌患者。
