Overexpression of eIF4E in colorectal cancer patients is associated with liver metastasis

Abstract

Purpose: Liver metastasis is one of the leading causes of death in colorectal cancer (CRC) patients. The present study aimed to evaluate the value of eIF4E as a prognostic marker of colorectal liver metastasis (CLM) and identify the functional role of eIF4E in CRC metastasis.

Patients and methods: The expression level of eIF4E in CRC tissues was analyzed by immunohistochemical staining and Western blot. Expression of eIF4E in CRC cell lines was evaluated by reverse transcription quantitative polymerase chain reaction (RT-qPCR) and Western blot. Cell Counting Kit-8 (CCK-8) and Transwell assays were performed to assess the effects of eIF4E on cell proliferation, migration, and invasion. Western blot was further used to investigate the mechanism of eIF4E in tumor metastasis.

Results: The upregulation frequency of eIF4E in the CLM group (82.5%) was higher than that in the non-CLM group (65.0%). Of the 80 patients recruited for the follow-up study, 23 were in the low eIF4E group (ratio of tumor to nontumor tissue <twofold), and 57 were in the high eIF4E group (ratio of tumor to nontumor tissue ≥twofold). In addition, the group exhibiting high eIF4E expression had a higher rate of liver metastasis (47.4%) than the group exhibiting low eIF4E expression (13.0%). In CRC cell lines, the expression of eIF4E was higher than in the normal cells. In vitro functional studies indicated that eIF4E knockdown inhibited the proliferation, migration, and invasion of Lovo and SW480 cells, and suppressed the expression of cyclin D1, VEGF, MMP-2, and MMP-9.

Conclusion: The results of the present study indicated that high eIF4E levels in CRC patients predicted a high risk of liver metastasis. Knockdown of eIF4E inhibited CRC cell metastasis in part through regulating the expression of cyclin D1, VEGF, MMP-2, and MMP-9.

Keywords: colorectal cancer; eIF4E; functional study; liver metastasis.

Figure 1

The expression level of eIF4E was elevated in the CLM group compared to the non-CLM group. Notes: (A) Immunohistochemical staining displayed the eIF4E expression level in CLM tissues and paired nontumor tissues (400×). (B) Immunohistochemical staining presented eIF4E expression in non-CLM tumor tissues and paired nontumor tissues (400×). (C) Western blot analysis showed the eIF4E level in 40 pairs of CLM tissue and 40 pairs of non-CLM tissue. (D) Scatter plots of eIF4E fold-change in the CLM and non-CLM group. *P<0.05. Abbreviations: CLM, colorectal liver metastasis; N, nontumor; T, tumor.

Figure 2

The eIF4E level in CRC patients predicted the risk of CLM. Notes: (A) The 80 patients were divided into two groups according to the Western blot analysis. (B) The incidence rate of CLM in the two groups. Abbreviations: CRC, colorectal cancer; CLM, colorectal liver metastasis.

Figure 3

eIF4E was upregulated in CRC cell lines. Notes: The expression level of eIF4E in the CRC cell lines was measured by qRT-PCR (A) and Western blot analysis (B); **P<0.01. Abbreviations: CRC, colorectal cancer; qRT-PCR, reverse transcription quantitative polymerase chain reaction; N, normal tissue.

Figure 4

eIF4E was involved in the proliferation, migration, and invasion of CRC cells. Notes: (A) The expression level of eIF4E after transfection of eIF4E siRNA was measured by qRT-PCR and Western blot. (B) The proliferation of Lovo and SW480 cell was assessed by the CCK-8 assay after knockdown of eIF4E. The migration (C) and invasion (D) abilities were measured using the Transwell assay after transfection of eIF4E siRNA (200×); *P<0.05. Abbreviations: CRC, colorectal cancer; qRT-PCR, reverse transcription quantitative polymerase chain reaction; CCK-8, Cell Counting Kit-8; h, hours; OD, optical density.

Figure 5

Knockdown of eIF4E suppressed the expression level of cyclin D1, VEGF, MMP-2, and MMP-9. Notes: The cyclin D1, VEGF, MMP-2, and MMP-9 levels were assessed by Western blot assay in Lovo (A) and SW480 (B) cell lines.