Ålgars Annika, Avoranta Tuulia, Österlund Pia, Lintunen Minnamaija, Sundström Jari, Jokilehto Terhi, Ristimäki Ari, Ristamäki Raija, Carpén Olli
Department of Oncology and Radiotherapy, Turku University Hospital, Turku, Finland.
Department of Oncology, Helsinki University Central Hospital, Helsinki, Finland; Department of Oncology, University of Helsinki, Helsinki, Finland.
PLoS One. 2014 Jun 18;9(6):e99590. doi: 10.1371/journal.pone.0099590. eCollection 2014.
Anti-EGFR therapy is commonly used to treat colorectal cancer (CRC), although only a subset of patients benefit from the treatment. While KRAS mutation predicts non-responsiveness, positive predictive markers are not in clinical practice. We previously showed that immunohistochemistry (IHC)-guided EGFR gene copy number (GCN) analysis may identify CRC patients benefiting from anti-EGFR treatment. Here we tested the predictive value of such analysis in chemorefractory metastatic CRC, elucidated EGFR GCN heterogeneity within the tumors, and evaluated the association between EGFR GCN, KRAS status, and anti-EGFR antibody response in CRC cell lines. The chemorefractory patient cohort consisted of 54 KRAS wild-type (WT) metastatic CRC patients. EGFR GCN status was analyzed by silver in situ hybridization using a cut-off value of 4.0 EGFR gene copies/cell. KRAS-WT and KRAS mutant CRC cell lines with different EGFR GCN were used in in vitro studies. The chemorefractory CRC tumors with EGFR GCN increase (≥4.0) responded better to anti-EGFR therapy than EGFR GCN (<4.0) tumors (clinical benefit, P = 0.0004; PFS, HR = 0.23, 95% CI 0.12-0.46). EGFR GCN counted using EGFR IHC guidance was significantly higher than the value from randomly selected areas verifying intratumoral EGFR GCN heterogeneity. In CRC cell lines, EGFR GCN correlated with EGFR expression. Best anti-EGFR response was seen with KRAS-WT, EGFR GCN = 4 cells and poorest response with KRAS-WT, EGFR GCN = 2 cells. Anti-EGFR response was associated with AKT and ERK1/2 phosphorylation, which was effectively inhibited only in cells with KRAS-WT and increased EGFR GCN. In conclusion, IHC-guided EGFR GCN is a promising predictor of anti-EGFR treatment efficacy in chemorefractory CRC.
抗表皮生长因子受体（EGFR）疗法常用于治疗结直肠癌（CRC），尽管只有一部分患者能从该治疗中获益。虽然KRAS突变预示着无反应，但在临床实践中尚无阳性预测标志物。我们之前表明，免疫组织化学（IHC）引导的EGFR基因拷贝数（GCN）分析可能会识别出能从抗EGFR治疗中获益的CRC患者。在此，我们测试了这种分析在化疗难治性转移性CRC中的预测价值，阐明了肿瘤内EGFR GCN的异质性，并评估了CRC细胞系中EGFR GCN、KRAS状态与抗EGFR抗体反应之间的关联。化疗难治性患者队列由54例KRAS野生型（WT）转移性CRC患者组成。使用银原位杂交分析EGFR GCN状态，截断值为4.0个EGFR基因拷贝/细胞。在体外研究中使用了具有不同EGFR GCN的KRAS-WT和KRAS突变CRC细胞系。EGFR GCN增加（≥4.0）的化疗难治性CRC肿瘤对抗EGFR治疗的反应优于EGFR GCN（<4.0）的肿瘤（临床获益，P = 0.0004；无进展生存期，风险比=0.23，95%置信区间0.12 - 0.46）。使用EGFR IHC引导计数的EGFR GCN显著高于从随机选择区域获得的值，证实了肿瘤内EGFR GCN的异质性。在CRC细胞系中，EGFR GCN与EGFR表达相关。KRAS-WT、EGFR GCN = 4的细胞对抗EGFR反应最佳，而KRAS-WT、EGFR GCN = 2的细胞反应最差。抗EGFR反应与AKT和ERK1/2磷酸化相关，只有在KRAS-WT且EGFR GCN增加的细胞中其磷酸化才被有效抑制。总之，IHC引导的EGFR GCN是化疗难治性CRC中抗EGFR治疗疗效的一个有前景的预测指标。
