Guanylyl Cyclase C Prevents Colon Cancer Metastasis by Regulating Tumor Epithelial Cell Matrix Metalloproteinase-9

Abstract

Matrix metalloproteinase-9 (MMP-9) produced by colorectal cancer cells is a critical determinant of metastatic disease progression and an attractive target for antimetastatic strategies to reduce colon cancer mortality. Cellular signaling by cyclic GMP (cGMP) regulates MMP-9 dynamics in various cell systems, and the bacterial enterotoxin receptor guanylyl cyclase C (GCC), the principle source of cGMP in colonocytes, which is overexpressed in colorectal cancers, inhibits tumor initiation and progression in the intestine. Here, we show that ligand-dependent GCC signaling through cGMP induces functional remodeling of cancer cell MMP-9 reflected by a compartmental redistribution of this gelatinase, in which intracellular retention resulted in reciprocal extracellular depletion. Functional remodeling of MMP-9 by GCC signaling reduced the ability of colon cancer cells to degrade matrix components, organize the actin cytoskeleton to form locomotory organelles and spread, and hematogenously seed distant organs. Of significance, GCC effects on cancer cell MMP-9 prevented establishment of metastatic colonies by colorectal cancer cells in the mouse peritoneum in vivo. Because endogenous hormones for GCC are uniformly deficient in intestinal tumors, reactivation of dormant GCC signaling with exogenous administration of GCC agonists may represent a specific intervention to target MMP-9 functions in colon cancer cells. The notion that GCC-mediated regulation of cancer cell MMP-9 disrupts metastasis, in turn, underscores the unexplored utility of GCC hormone replacement therapy in the chemoprevention of colorectal cancer progression.

Emergent Concepts from the Intestinal Guanylyl Cyclase C Pathway

“…Cyclic GMP inhibits the synthesis and secretion of MMP-9 in various cell systems (Akool el et al, 2003;Gurjar et al, 1999). Accordingly, restoration of ligand-dependent GCC signalling though cGMP induces a compartmental redistribution of colon cancer cell MMP-9, in which intracellular retention results in reciprocal extracellular depletion of that collagenase (Lubbe et al, 2009). As a consequence, MMP-9 proteolytic activities at the pericellular tumor space are suppressed, with abrogation of MMP-9-dependent interstitial matrix remodelling and cell spreading (Lubbe et al, 2009).…”

“…Accordingly, restoration of ligand-dependent GCC signalling though cGMP induces a compartmental redistribution of colon cancer cell MMP-9, in which intracellular retention results in reciprocal extracellular depletion of that collagenase (Lubbe et al, 2009). As a consequence, MMP-9 proteolytic activities at the pericellular tumor space are suppressed, with abrogation of MMP-9-dependent interstitial matrix remodelling and cell spreading (Lubbe et al, 2009). Conversely, mutational dormancy of the GCC pathway early in transformation (Birkenkamp-Demtroder et al, 2002;Cohen et al 1998;Notterman et al, 2001;Steinbrecher et al, 2000) may permit the emergence of a pro-tumorigenic stromal environment characterized by increased MMP-9 secretion, break-down of epithelial basement membranes by MMP-9 catalytic activity and disruption of homeostatic epithelial-mesenchymal interactions.…”

“…Conversely, mutational dormancy of the GCC pathway early in transformation (Birkenkamp-Demtroder et al, 2002;Cohen et al 1998;Notterman et al, 2001;Steinbrecher et al, 2000) may permit the emergence of a pro-tumorigenic stromal environment characterized by increased MMP-9 secretion, break-down of epithelial basement membranes by MMP-9 catalytic activity and disruption of homeostatic epithelial-mesenchymal interactions. It has been proposed that GCC effect on spatiotemporal MMP-9 dynamics in colon cancer cells has a profound impact on the overall tumor phenotype, because by disrupting its surface localization, membrane anchoring and focal catalytic activity it suppresses oncogenic MMP-9 functions (Lubbe et al, 2009). …”

“…However away from its primary organ, GCC is a ligand-starved receptor with an intracellular dormant pathway, as normal mucosal cells in intestine are the principal producers of endogenous hormones guanylin and uroguanylin (Forte, 1999). Thus, the loss of GCC ligand expression early in transformation (Birkenkamp-Demtroder et al, 2002;Cohen et al, 1998;Notterman et al, 2001;Steinbrecher et al, 2000) may be part of the exclusive phenotypic mutations conferring a pro-metastatic evolutionary advantage to selected colon cancer clones (Lubbe et al, 2009;Pitari et al, 2007;Zuzga et al, 2011).…”

“…Normally restricted at intestinal epithelial brush borders (Lucas et al, 2000), GCC is ideally positioned to affect those molecular networks and exert spatio-temporal control of actin remodelling. Indeed, ligand-dependent GCC signalling through cGMP appears to act as a suppressor of metastatic cell morphology in intestine (Lubbe et al, 2009;Zuzga et al, 2011). Thus, colon cancer cells assume a rounded shape upon GCC signalling activation, with elimination of F-actin rich filopodia and lamellipodia (Lubbe et al, 2009).…”