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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Research Article Oncology

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 4

Inhibition of PC activity alter E-selectin–dependent adhesion of tumor cells to endothelial cells and cytokine production.

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Inhibition of PC activity alter E-selectin–dependent adhesion of tumor c...
(A) RT-PCR analysis was performed on RNA extracted from liver sinusoidal endothelial cells activated with TNF-α (10 ng/ml, positive control) or media derived from HT-29 or HT-29/PDX cells using E-selectin and GAPDH-specific primers. Note that media derived from HT-29/PDX cells failed to significantly induce E-selectin expression compared with media derived from HT-29 cells or TNF-α. (B) To test the effect of PC inhibition on tumor–endothelial cell adhesion, tumor cells were labeled with calcein and left to adhere to TNF-α (10 ng/ml) or tumor cell–derived, conditioned media–activated endothelial layer in the presence or absence of an anti–E-selectin neutralizing antibody. The attached tumor cells were quantified by measuring the fluorescence emission using a fluorometer. Only TNF-α and media derived from control cells significantly induced HT-29 adhesion. (C) RT-PCR analysis was performed on RNA extracted from HT-29 and HT-29/PDX cells using TNF-α, IL-1α, or GAPDH-specific primers. (D and E) Tumor cells were incubated at 37°C in serum-free media. After 24–48 hours, media were collected and analyzed for the presence of IL-1α and TNF-α using ELISA kit. Note the highly reduced expression and production of these cytokines in the presence of α1-PDX. Results shown are representative of 3 experiments. Data are mean ± SEM (n = 3 per group). **P < 0.001.