Colicins and their potential in cancer treatment

doi:10.1016/j.bcmd.2006.10.006

Blood Cells, Molecules, and Diseases

Volume 38, Issue 1, January–February 2007, Pages 15-18

https://doi.org/10.1016/j.bcmd.2006.10.006 Get rights and content

Abstract

Colicins are a family of antibacterial cytotoxins produced by Escherichia coli and released into the environment to reduce competition from other bacterial strains. Colicins kill the target cell by a variety of effects that include depolarisation of the cytoplasmic membrane, a non-specific DNase activity, a highly specific RNase activity or by inhibition of murein synthesis. This review summarises some important findings that implicate colicins as potential anti-tumor agents. Colicins appear to inhibit proliferation of tumor cell lines in a colicin-type- and cell line-dependent fashion and are more toxic to tumor cells than to normal cells within the body. This opens a potential for using bacterial colicins in combating cancer and raises a number of questions concerning the mechanism of action of colicins in targeting tumor cells, their specificity and applicability as anti-tumor therapeutics.

Introduction

Cancer remains a major public health problem in the modern world. It is responsible for 250 of 100 000 deaths and 10 million new cases worldwide are diagnosed every year (World Cancer Research Fund international; http://www.wcrf.org). Despite the improvements in surgery, radiotherapy and chemotherapy, these treatments can result in severe side effects or reduced resistance to infection and can have a long-term negative impact on human health (British Cancer agency; http://bccancer.bc.ca/default.htm). Thus, novel, more specific treatments need to be developed in order to add to the therapeutic methods available at present.

One promising strategy to specifically target tumor cells utilizes antibodies that are specific to outer membrane proteins of the cancerous cells and are coupled with cytotoxic compounds such as small-molecule drugs, radionucleotides or protein toxins [1]. Immunotoxins were developed using plant or bacterial toxins that attack eukaryotic cells such as ricin, saponin, diphtheria toxin or Pseudomonas exotoxin. To achieve specific targeting to tumor cells, the natural cell binding domains of the bacterial toxins were deleted or mutated to prevent binding to normal cells, then the toxic domain fused to cell targeting agents such as antibodies, cell-binding hormones, growth factor ligands or transferrin to allow internalisation and, subsequently, cell killing to occur [2]. However, these constructs were found to be highly toxic and the foreign origin of the toxins activated the immune system [3], [4]. Development of milder toxins that are tolerated within humans is required to solve these problems [5].

Bacteriocins produced by bacteria to kill competing bacterial strains could potentially be used as milder toxins against cancerous cells. These proteins are designed to bind the bacterial cell, penetrate the cell wall and kill the cell by a number of methods including pore formation, cleavage of DNA or specific inhibition of protein synthesis. These toxins are not specific for human cell membranes so a targeting system specific for tumor cells would need to be developed. Recent research has shown that the bacteriocins known as colicins can specifically inhibit proliferation of cancer cells, and thus could potentially be explored for combating cancer.

Section snippets

Colicins: an overview

Colicins are a family of antibacterial cytotoxins produced by Escherichia coli and released into the environment during the SOS response. They are present in ∼ 30% of E. coli isolates [6] and are believed to reduce competition from closely related strains of bacteria during times of stress caused by lack of nutrients, UV light or DNA damaging reagents such as mitomycin C. These proteins have been studied extensively in their involvement in competition, diversification and adoption of bacteria.

Cancer targeting by colicins

Research into colicins and their cytotoxic effects with human tumor cells began about 30 years ago, when colicin E3 was first reported to have significant cytocidal effects on human HeLa cells [26]. Some promising results were also observed from a colicin extracted from the E. coli strain HSC10 added to murine ascitic lymphatic leukaemia cells EL-4 [27]. Unfortunately, these results were obtained from a crude extract of colicin and it was soon realised that the anti-neoplastic activity was due

Concluding remarks

When investigating possible therapeutic drugs against cancer, it is important to consider the selectivity, mode of internalisation, intracellular targeting and the role of any form of inhibition within the patient (RNase inhibitors, immune system). Although colicins appear to be a promising group of bacteriocins against cancerous cells, most of these points are still unresolved.

The specificity of colicins for tumor cells is dependent on the colicin and on the cell line used [32]. Generally,

Acknowledgments

This paper is based on a presentation at a Focused Workshop on RNA Chemistry meets Biology sponsored by The Leukemia and Lymphoma Society (Lund, Sweden, September 29–30, 2006). Work in our laboratories was supported by the Deutsche Forschungsgemeinschaft, the Alfried Krupp von Bohlen und Halbach-Stiftung, and the Fonds der Chemischen Industrie.

References (40)

S. Rybak et al.
Natural and engineered cytotoxic ribonucleases: therapeutic potential
Exp. Cell Res.
(1999)
A.A. Makarov et al.
Cytotoxic ribonucleases: molecular weapons and their targets
FEBS Lett.
(2003)
S. Imajoh et al.
The receptor for colicin E3. Isolation and some properties
J. Biol. Chem.
(1982)
J.-C. Lazzaroni et al.
The Tol proteins of Escherichia coli and their involvement in the uptake of biomolecules and outer membrane stability
FEMS Microbiol. Lett.
(1999)
P.C. Tai
Impaired initiation complex formation on ribosomes treated with colicin E3
Biochem. Biophys. Res. Commun.
(1975)
A.J. Pommer et al.
Mechanism and cleavage specificity of the H–N–H endonuclease colicin E9
J. Mol. Biol.
(2001)
F. Turnowsky et al.
In vitro inactivation of ascites ribosomes by colicin E3
Biochem. Biophys. Res. Commun.
(1973)
H. Suzuki
Colicin E3 inhibits rabbit globin synthesis
FEBS Lett.
(1978)
C. Kleanthous et al.
Immunity proteins: enzyme inhibitors that avoid the active site
Trends Biochem. Sci.
(2001)
S.V. Govindan et al.
Cancer therapy with radiolabeled and drug/toxin-conjugated antibodies
Technol. Cancer Res. Treat.
(2005)

L. Johannes et al.

Protein toxins: intracellular trafficking for targeted therapy

Gene Ther.

(2005)

G. Thrush et al.

Immunotoxins: an update

Annu. Rev. Immunol.

(1996)

M.A. Riley

Molecular mechanisms of colicin evolution

Mol. Biol. Evol.

(1993)

R. James et al.

The biology of E colicins: paradigms and paradoxes

Microbiology

(1996)

S. Ohno et al.

Purification and characterization of active component and active fragment of colicin E3

J. Biochem. (Tokyo)

(1977)

K. Postle

TonB protein and energy transduction between membranes

J. Bioenerg. Biomembr.

(1993)

W.A. Cramer et al.

Structure and dynamics of the colicin E1 channel

Mol. Microbiol.

(1990)

C.K. Lau et al.

Bacteriocins, Microcins and Lantibiotics

(1992)

C.M. Bowman et al.

Specific inactivation of ribosomes by colicin E3 in vitro and mechanism of immunity in colicinogenic cells

Nat. New Biol.

(1971)

K. Tomita et al.

A cytotoxic ribonuclease which specifically cleaves four isoaccepting arginine tRNAs at their anti-codon loops

Proc. Natl. Acad. Sci. U. S. A.

(2000)

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Colicin plasmids share a common genetic organization consisting of the colicin gene that is expressed under control of the SOS regulon, an immunity protein as well as a lysis protein that facilitates the release of the colicin from the periplasm (Riley and Wertz, 2002). Although colicins are generally narrow spectrum antibiotics, the ColE3 RNA cleavage recognition sequence is also present in eukaryotic 18S subunit, and ColE3 has been shown to be cytotoxic to some cancer cells (Fuska et al., 1979; Lancaster et al., 2007; Cornut et al., 2008). Several bacterial strains with tumor-targeting capability including Salmonella sp. are currently being investigated for their potential use in cancer therapeutics (Forbes, 2010; Hoffman and Zhao, 2014; Low et al., 1999; Pawelek et al., 1997).
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