Selective inhibition of proprotein convertases represses the metastatic potential of human colorectal tumor cells
Nathalie Scamuffa, … , Nabil G. Seidah, Abdel-Majid Khatib
Nathalie Scamuffa, … , Nabil G. Seidah, Abdel-Majid Khatib
Published December 6, 2007
Citation Information: J Clin Invest. 2008;118(1):352-363. https://doi.org/10.1172/JCI32040.
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Selective inhibition of proprotein convertases represses the metastatic potential of human colorectal tumor cells

Abstract

The proprotein convertases (PCs) are implicated in the activation of various precursor proteins that play an important role in tumor cell metastasis. Here, we report their involvement in the regulation of the metastatic potential of colorectal tumor cells. PC function in the human and murine colon carcinoma cell lines HT-29 and CT-26, respectively, was inhibited using siRNA targeting the PCs furin, PACE4, PC5, and PC7 or by overexpression of the general PC inhibitor α1-antitrypsin Portland (α1-PDX). We found that overexpression of α1-PDX and knockdown of furin expression inhibited processing of IGF-1 receptor and its subsequent activation by IGF-1 to induce IRS-1 and Akt phosphorylation, all important in colon carcinoma metastasis. These data suggest that the PC furin is a major IGF-1 receptor convertase. Expression of α1-PDX reduced the production of TNF-α and IL-1α by human colon carcinoma cells, and incubation of murine liver endothelial cells with conditioned media derived from these cells failed to induce tumor cell adhesion to activated murine endothelial cells, a critical step in metastatic invasion. Furthermore, colon carcinoma cells in which PC activity was inhibited by overexpression of α1-PDX when injected into the portal vein of mice showed a significantly reduced ability to form liver metastases. This suggests that inhibition of PCs is a potentially promising strategy for the prevention of colorectal liver metastasis.

Authors

Nathalie Scamuffa, Geraldine Siegfried, Yannick Bontemps, Liming Ma, Ajoy Basak, Ghislaine Cherel, Fabien Calvo, Nabil G. Seidah, Abdel-Majid Khatib

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Figure 5

Induction of hepatic TNF-α mRNA by tumor cells.

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Induction of hepatic TNF-α mRNA by tumor cells. (A and B) Mice were inje...
(A and B) Mice were injected though the intrasplenic/portal route with 106 HT-29, HT-26/PDX (A), CT-26, or CT-26/PDX cells (B), and their livers were removed at the indicated times. Total RNA was extracted and analyzed by RT-PCR using specific primers for murine TNF-α or GAPDH. Results of laser densitometry are shown in the graph and are expressed as the ratio of TNF-α/GAPDH mRNA to that of control (liver of saline-injected mice at 1 hour), which was assigned a value of 1. In Panel A and B the time zero data is from a different RT-PCR experiment done at the same time. (C) Western blotting analysis of TNF-α expression in response to tumor cells 19 hours after injection. (D) Immunohistochemistry analysis of liver sections derived from the animals 19 hours following injection of tumor cells. The sections were stained with an anti-murine TNF-α antibody (green stain, denoted by white arrows). Yellow arrows indicate the lumen of liver vessels. Note that cells expressing α1-PDX failed to induce adequately hepatic TNF-α expression compared with control cells. No significant staining was observed in uninjected or saline-injected mice. Original magnification, ×40. Results shown are representative of 2 experiments. Values are mean ± SEM (n = 4 per group). *P < 0.05, **P < 0.001 versus respective α1-PDX–expressing group.