Oncogenic Ras and its role in tumor cell invasion and metastasis

https://doi.org/10.1016/j.semcancer.2003.09.015Get rights and content

Abstract

The processes by which cancer cells leave the tumor and enter adjacent tissue is known as invasion, whereas metastasis refers to secondary tumor colonization of tissue at a distance from the primary lesion. These two events are the most lethal of cancer phenomena and the signaling mechanisms that govern them are complex. The Ras signaling pathways are well represented in their involvement in tumor initiation, but considerably less is known about their contribution to invasion and metastasis. In this review, we discuss the current evidence for mutant Ras proteins as significant players in these aspects of cancer progression.

Introduction

As the initiation and progression of solid tumors is in part dependent on a variety of signaling pathways, so too are the processes that allows for invasion and metastasis. In metastasis, cells migrate from the primary tumor, cross the tumor marginal border gaining access to the vascular and/or lymphatic system, and enter distal tissue. At this point, these “rogue” cells may lie dormant for an indefinite period of time, but upon stimulation by signals that at the present are not entirely known, these micrometastases can subsequently proliferate into solid tumors themselves. Because the process of metastasis can lead to potentially many secondary tumor sites, and because evidence indicates a more aggressive and lethal phenotype for the metastatic tumor versus the primary lesion, it is imperative to gain further knowledge of the biology of metastasis and invasion. Understanding the signaling mechanisms that lead to such migration will enable discovery of additional targets for therapeutic design.

Ras proteins (of which H-, N-, and K-Ras4A/4B are prototypical) are associated with the inner face of the plasma membrane where they facilitate signaling initiated by diverse extracellular stimuli [1]. Ras activity is regulated by cycling between inactive GDP-bound and active GTP-bound forms [2] (Fig. 1). Increase in GDP/GTP nucleotide exchange involves interaction between Ras and guanine exchange factors (GEFs), for example Sos1/2, RasGRP and RasGRF1/2 proteins [3]. When GTP-bound, Ras binds to and activates a plethora of effector molecules [1], [4], [5]. Hydrolysis of GTP by Ras is facilitated by GTPase-activating proteins (GAPs) such as p120GAP and NF1. Mutated variants of Ras (mutations at residues 12, 13 or 61) are found in 30% of all human cancers, are insensitive to GAP stimulation, and are consequently rendered constitutively activated [6], [7].

In addition to mutational activation, Ras GTPase signaling can be upregulated due to increased coupling to cell surface receptors. In particular, members of the epidermal growth factor (EGF) family of receptor tyrosine kinases (RTKs; including EGFR/ErbB/HER1 and ErbB2/Her2/Neu) [8], [9], [10] or other tyrosine kinases (e.g. Bcr-Abl) are commonly overexpressed in many cancers, causing persistent activation of Ras in the absence of mutations in Ras genes. Thus, Ras activation has been shown to be an important mediator of tumor cell invasion and metastasis caused by these and other tyrosine kinases. However, for the purpose of this review, we will limit our focus to the effects of mutationally activated Ras proteins on invasive and metastatic phenotypes.

The aberrant activation of Ras proteins been implicated in facilitating virtually all aspects of the malignant phenotype of the cancer cell, including cellular proliferation, transformation, invasion and metastasis (reviewed in [11]). Additionally, the functions of other Ras-related proteins are also regulated by Ras signaling and also contribute to oncogenesis. While much is known regarding the mechanisms by which aberrant Ras promotes uncontrolled proliferation by deregulation of cell cycle progression and promotion of cell survival, less is known regarding how Ras promotes tumor cell invasion and metastasis. In this review, we summarize the current understanding of the mechanisms by which oncogenic Ras promotes the malignant phenotype of cancer cells.

Section snippets

Mouse and in vitro experimental models

A variety of experimental approaches have been undertaken to ascertain the degree to which Ras GTPases are involved in and/or causative for metastasis and invasion. In both in vitro and in vivo experimental models, transfection of mutated, constitutively active forms of Ras into previously noncancerous cells can lead to invasive and metastatic phenotypes [12], [13]. One of the most commonly studied models of Ras activation is the murine NIH 3T3 fibroblast cell line. Ectopic expression of

Contribution of specific effectors downstream of oncogenic Ras

Ras interacts with and regulates multiple downstream effectors that stimulate diverse cytoplasmic signaling activities [1], [4], [5]. As new effectors continue to be identified, one of the critical issues concerns the specific role of each effector in Ras-mediated oncogenesis. While some are clearly important positive mediators of the oncogenic properties of Ras (e.g. Raf, PI3K, RalGEF, Tiam1), others may serve negative regulatory roles in oncogenesis (e.g. Nore1, RASSF).

One important area of

Met

The protooncogene Met is a RTK that is activated by its ligand hepatocyte growth factor/scatter factor (HGF/SF) [70]. Met and HGF/SF are overexpressed in metastases, and aberrant Met–HGF/SF signaling increased motility and invasion of cells in vitro and in vivo in part by augmenting the activity of urokinase plasminogen activator (uPa) [71]. uPa is known to be involved in the destruction of ECM/basement membrane, a necessary event in the migration of cells from the solid tumor.

Vande Woude and

Actin cytoskeleton

Gelsolin is a protein able to disrupt the actin cytoskeleton by cleaving F-actin subunits. It has been proposed that the upregulation of gelsolin may account for the transition from benign to invasive cell growth in some but not all tumors [87], [88]. Kwiatkowski and coworkers demonstrated a connection between gelsolin activity and Rac in fibroblast motility [89], and Gettemans and coworkers demonstrate that gelsolin activity is affected by the oncogenic Ras pathway [90], and that invasion of

Conclusions

Much work has been accomplished in discovering the many facets of oncogenic Ras signaling evident in the growth transformation of cells. These data have revealed that the mechanisms downstream of Ras are much more complex than originally thought. Similar conclusions are being formed about mutant Ras and its contribution to increased motility, invasiveness, and metastatic potential. Clearly, crosstalk and feedback with a multiplicity of signaling networks are in evidence, and the pathways

References (129)

  • N.G. Ahn et al.

    Pharmacologic inhibitors of MKK1 and MKK2

    Methods Enzymol.

    (2001)
  • J. Downward

    Ras signalling and apoptosis

    Curr. Opin. Genet. Dev.

    (1998)
  • J. Downward

    Cell cycle: routine role for Ras

    Curr. Biol.

    (1997)
  • K. Pruitt et al.

    Ras and Rho regulation of the cell cycle and oncogenesis

    Cancer Lett.

    (2001)
  • H. Chong et al.

    Mechanisms of regulating the Raf kinase family

    Cell. Signal

    (2003)
  • A. Seth et al.

    Signal transduction within the nucleus by mitogen-activated protein kinase

    J. Biol. Chem.

    (1992)
  • L.M. Shaw et al.

    Activation of phosphoinositide 3-OH kinase by the alpha6beta4 integrin promotes carcinoma invasion

    Cell

    (1997)
  • S.M. Frisch et al.

    Integrins and anoikis

    Curr. Opin. Cell. Biol.

    (1997)
  • A.A. Schmitz et al.

    Rho GTPases: signaling, migration, and invasion

    Exp. Cell. Res.

    (2000)
  • L.A. Feig

    Ral-GTPases: approaching their 15 minutes of fame

    Trends Cell Biol.

    (2003)
  • G.G. Habets et al.

    Identification of an invasion-inducing gene, Tiam-1, that encodes a protein with homology to GDP-GTP exchangers for Rho-like proteins

    Cell.

    (1994)
  • J.S. Rubin et al.

    Hepatocyte growth factor/scatter factor and its receptor, the c-met proto-oncogene product

    Biochim. Biophys. Acta

    (1993)
  • A.E. Mertens et al.

    Regulation of Tiam1-Rac signalling

    FEBS Lett.

    (2003)
  • E. Vial et al.

    ERK-MAPK signaling coordinately regulates activity of Rac1 and RhoA for tumor cell motility

    Cancer Cell

    (2003)
  • G. Oxford et al.

    Ras superfamily monomeric G proteins in carcinoma cell motility

    Cancer Lett.

    (2003)
  • P.T. Hawkins et al.

    PDGF stimulates an increase in GTP-Rac via activation of phosphoinositide 3-kinase

    Curr. Biol.

    (1995)
  • V. Benard et al.

    Characterization of Rac and Cdc42 Activation in Chemoattractant-stimulated Human Neutrophils Using a Novel Assay for Active GTPases

    J. Biol. Chem.

    (1999)
  • M. Oft et al.

    TGFbeta signaling is necessary for carcinoma cell invasiveness and metastasis

    Curr. Biol.

    (1998)
  • M. Ballin et al.

    Ras oncogene mediated induction of a 92 kDa metalloproteinase; strong correlation with the malignant phenotype

    Biochem. Biophys. Res. Commun.

    (1988)
  • H.R. Bourne et al.

    The GTPase superfamily: conserved structure and molecular mechanism

    Nature

    (1991)
  • J.L. Bos

    Ras oncogenes in human cancer: a review

    Cancer Res.

    (1989)
  • M. Barbacid

    Ras genes

    Annu. Rev. Biochem.

    (1987)
  • P.W. Janes et al.

    Activation of the Ras signalling pathway in human breast cancer cells overexpressing erbB-2

    Oncogene

    (1994)
  • G.J. Clark et al.

    Aberrant function of the Ras signal transduction pathway in human breast cancer

    Breast Cancer Res. Treat.

    (1995)
  • M. Malumbres et al.

    To cycle or not to cycle: a critical decision in cancer

    Nat. Rev. Cancer

    (2001)
  • R.J. Muschel et al.

    Harvey ras induction of metastatic potential depends upon oncogene activation and the type of recipient cell

    Am. J. Pathol.

    (1985)
  • G.P. Bondy et al.

    Experimental metastatic ability of H-ras-transformed NIH3T3 cells

    Cancer Res.

    (1985)
  • M.O. Bradley et al.

    Experimental metastasis in nude mice of NIH 3T3 cells containing various ras genes

    Proc. Natl. Acad. Sci. USA

    (1986)
  • E.E. Sander et al.

    Matrix-dependent Tiam1/Rac signaling in epithelial cells promotes either cell-cell adhesion or cell migration and is regulated by phosphatidylinositol 3-kinase

    J. Cell. Biol.

    (1998)
  • M.C. Gingras et al.

    Transient alterations in the expression of protease and extracellular matrix genes during metastatic lung colonization by H-ras-transformed 10T1/2 fibroblasts

    Cancer Res.

    (1990)
  • R. Pozzatti et al.

    Primary rat embryo cells transformed by one or two oncogenes show different metastatic potentials

    Science

    (1986)
  • F. Al-Mulla et al.

    Differences in in vitro invasive capacity induced by differences in Ki-Ras protein mutations

    J. Pathol.

    (2001)
  • J.D. Fetherston et al.

    Transfection of normal and transformed hamster cerebral cortex glial cells with activated c-H-ras-1 results in the acquisition of a diffusely invasive phenotype

    Oncogene Res.

    (1989)
  • G. Brunner et al.

    Induction of urokinase activity and malignant phenotype in bladder carcinoma cells after transfection of the activated Ha-ras oncogene

    J. Cancer Res. Clin. Oncol.

    (1989)
  • P.J. Keely et al.

    R-Ras signals through specific integrin alpha cytoplasmic domains to promote migration and invasion of breast epithelial cells

    J. Cell. Biol.

    (1999)
  • J. Ochieng et al.

    Increased invasive, chemotactic and locomotive abilities of c-Ha-ras-transformed human breast epithelial cells

    Invasion Metastasis

    (1991)
  • E.P. Gelmann et al.

    Invasive and metastatic properties of MCF-7 cells and rasH-transfected MCF-7 cell lines

    Int. J. Cancer

    (1992)
  • E.R. Boghaert et al.

    Inhibition of collagenotytic activity relates to quantitative reduction of invasion in vitro in a c-Ha-ras transfected glial cell line

    J Neurooncol.

    (1994)
  • R.D. Bonfil et al.

    Invasive and metastatic potential of a v-Ha-ras-transformed human bronchial epithelial cell line

    J. Natl. Cancer Inst.

    (1989)
  • T. Joneson et al.

    Stimulation of membrane ruffling and MAP kinase activation by distinct effectors of RAS

    Science

    (1996)
  • Cited by (224)

    • Identification of Radil as a Ras binding partner and putative activator

      2021, Journal of Biological Chemistry
      Citation Excerpt :

      Biochemically, Ras GTPases catalyze the hydrolysis of GTP to GDP. GTP-bound Ras is active, whereas GDP-bound one is inactive (1–3). To test whether GTP/GDP-loading status affected the interaction between Radil and Ras, we transfected HEK293T cells for 24 h with a plasmid encoding Flag-HRas (WT HRas), constitutively active mutant (HRasV12 bound with GTP), or dominant negative mutant (HRasN17 incapable of GTP-binding).

    View all citing articles on Scopus
    View full text