Upregulation of ERCC1 and DPD expressions after oxaliplatin-based first-line chemotherapy for metastatic colorectal cancer

Abstract

Background: The updated randomised phase 2/3 FIRIS study demonstrated the noninferiority of IRIS (irinotecan and S-1) to FOLFIRI (irinotecan, folinic acid, and 5-FU) for metastatic colorectal cancer. Meanwhile, in the subset analysis including patients who previously have undergone oxaliplatin-containing chemotherapy, the IRIS group showed longer survival than the FOLFIRI group. However, the molecular mechanism underlying this result is still unknown.

Methods: The National Cancer Institute 60 (NCI60) cell line panel data were utilised to build the hypothesis. A total of 45 irinotecan-naive metastatic colorectal cancer patients who had undergone hepatic resection were included for the validation study. The mRNA expressions of excision repair cross-complementing group 1 (ERCC1), dihydropyrimidine dehydrogenase (DPD), and topoisomerase-1 (TOP1) were evaluated by quantitative RT-PCR. The expressions of ERCC1 and DPD were also evaluated by immunohistochemistry.

Results: Sensitivity to oxaliplatin in 60 cell lines was significantly correlated with that of 5-FU. Resistant cells to oxaliplatin showed significantly higher ERCC1 and DPD expression than sensitive cells. In validation study, ERCC1 and DPD but not TOP1 expressions in cancer cells were significantly higher in FOLFOX (oxaliplatin, folinic acid, and 5-FU)-treated patients (N=24) than nontreated patients (N=21). The ERCC1 and DPD protein expressions were also significantly higher in FOLFOX-treated patients.

Conclusion: The ERCC1 and DPD expression levels at both mRNA and protein levels were significantly higher in patients with oxaliplatin as a first-line chemotherapy than those without oxaliplatin. The IRIS regimens with the DPD inhibitory fluoropyrimidine may show superior activity against DPD-high tumours (e.g., tumours treated with oxaliplatin) compared with FOLFIRI.

Figure 1

Oxaliplatin-resistant cells showed high ERCC1 and DPD expression in in silico analysis. (A) Relationship between cytotoxic effects of oxaliplatin (NSC266046) and 5-FU (NSC19893) in 60 NCI60 panel cell lines. (B) Comparison of gene expression level, ERCC1 and DPD, or copy number between low sensitive cells and high sensitive cells to oxaliplatin. Data expressed as log₂ (per chip normalised value × 500). *P<0.05.

Figure 2

The ERCC1 and DPD mRNAs upregulated in CRC patients with preoperative FOLFOX. (A) Typical slide for pathological diagnosis of FFPE tumour specimens (magnification × 2.4). Sections, 5-μm-thick, stained with haematoxylin and eosin before microdissection (magnification × 50). After staining with nuclear fast red, standard manual microdissection was performed (magnification × 50). (B) Comparison of gene expression levels of ERCC1, DPD, and TOP1 in tumour cells with or without FOLFOX regimen before hepatectomy. *P<0.001 for ERCC1 and P=0.005 for DPD, respectively.

Figure 3

ERCC1 and DPD upregulated in CRC patients with preoperative FOLFOX. Representative pictures of ERCC1 and DPD in CRC patients. Cases of CRC showing weak (A), moderate (B), and strong (C) ERCC1 staining. Cases of CRC showing weak (D), moderate (E), and strong (F) DPD staining; bar=50 μm. (G) The expression scores of ERCC1 and DPD were compared between patients with FOLFOX and patients without FOLFOX using Wilcoxon test. *P=0.015 for ERCC1 and P=0.0025 for DPD, respectively.

Figure 4

Hypothesis of molecular mechanism of superiority in IRIS group for prior oxaliplatin-treated patients. This study demonstrated that oxaliplatin-resistant tumour cells showed high ERCC1 and DPD, and thereby seemed to be sensitive to IRIS therapy.