Difference Between Cytotoxicity and Genotoxicity

The key difference between cytotoxicity and genotoxicity is that cytotoxicity is the quality of being toxic to cells while genotoxicity is the ability to damage DNA and/or the cellular apparatus that regulates the fidelity of the genome.

Cytotoxicity and genotoxicity are two qualities of chemical agents or drugs. Cytotoxicity is the quality of being toxic to cells while genotoxicity is the quality of damaging the genetic information within a cell, causing mutations. Some toxic chemical may induce both cytotoxicity and genotoxicity. Also, genotoxicity may lead to cytotoxicity. One the other hand, cytotoxicity may or may not be genotoxic as not every cytotoxic agent is genotoxic.

CONTENTS

1. Overview and Key Difference
2. What is Cytotoxicity
3. What is Genotoxicity
4. Similarities Between Cytotoxicity and Genotoxicity
5. Side by Side Comparison – Cytotoxicity vs Genotoxicity in Tabular Form
6. Summary

What is Cytotoxicity?

Cytotoxicity is the property of a chemical agent to be toxic to cells. So, if you treat cells with a cytotoxic agent, it can destroy cells. These agents may or may not damage the genome or genetic material of the cell. Therefore, not every cytotoxic agent is genotoxic. When treated with a cytotoxic agent, cells may undergo necrosis, and they may die quickly due to cell lysis. Moreover, cells may stop growing and dividing. Cytotoxic chemicals also accelerate apoptosis or programmed cell death. In cancer patients, chemotherapy often uses cytotoxic drugs to kill or damage rapidly, dividing cancer cells. Therefore, cytotoxicity is a key feature considered when developing therapeutic anti-cancer drugs.

Cytotoxicity can be measured using different assays such as dye exclusion assays, colourimetric assays, fluorometric assays and luminometric assays. It is necessary to choose the appropriate method. The cell membrane integrity indicates cell viability and cytotoxic effects of chemicals. Therefore, assessing cell membrane integrity is the best way of measuring cytotoxicity. Cytotoxic chemicals often compromise cell membrane integrity. Healthy cells do not allow trypan blue or propidium iodide to enter the cell. When the cell loses cell membrane integrity, trypan blue or propidium iodide go inside the cells and stain the interior. Moreover, cytotoxicity can be measured using 3-(4, 5-Dimethyl-2-thiazolyl)-2, 5-diphenyl-2H-tetrazolium bromide (MTT) or by sulforhodamine B (SRB) assays. In blood or bone marrow, a significant change in the proportion of immature erythrocytes among total erythrocytes indicates the cytotoxicity of chemicals.

What is Genotoxicity?

Genotoxicity is the ability to damage the DNA of a cell.  In other words, genotoxicity is the ability of a chemical to destroy genetic material of a cell and cause mutations (change in the genetic information). When the DNA is damaged, it can lead to cancer, genetic disease or birth defects. Moreover, it can lead to cytotoxicity and destroy cells. Generally, all mutagens are genotoxic, but not all genotoxic chemicals are mutagenic. Generally, genotoxic testing is done for pharmaceuticals, industrial chemicals, and consumer products.

Genotoxicity can be measured by in vivo and in vitro tests for chromosomal damage, especially by analyzing chromosomal aberrations in metaphase cells. Moreover, it can also detect gene mutations. Micronucleus test and comet assay are two common genotoxicity tests. Ames test is usually done to find gene mutations in bacteria.

What are the Similarities Between Cytotoxicity and Genotoxicity?

• Both cytotoxicity and genotoxicity are two abilities of chemical agents to damage cell or genetic material.
• A cytotoxic agent may be genotoxic (causing DNA damage).

What is the Difference Between Cytotoxicity and Genotoxicity?

Cytotoxicity is the ability to cause damages to living cells, while genotoxicity is the ability to induce changes in the structure or number of genes via chemical interaction with DNA and/or non-DNA targets. So, this is the key difference between cytotoxicity and genotoxicity. Cytotoxic agents can make cells undergo necrosis or apoptosis while genotoxic chemicals can change the structure, nucleotide sequence or the number of genes within a cell.

Summary – Cytotoxicity vs Genotoxicity

Cytotoxicity refers to the ability of chemical agents to damage cells or destroy living cells. Genotoxicity refers to the ability of chemical agents to damage the genetic information (genome) within a cell. Not all cytotoxic chemicals are genotoxic. However, genotoxicity may lead to cytotoxicity. Thus, this summarizes the difference between cytotoxicity and genotoxicity.

Reference:

1. “Cytotoxic Agent – An Overview | Sciencedirect Topics”. Sciencedirect.Com, 2020, Available here.
2. “Genotoxicity”. Cyprotex.Com, 2020, Available here.

Image Courtesy:

1. “Structural changes of cells undergoing necrosis or apoptosis” By National institute on alcohol abuse and alcoholism (NIAAA) – File:Structural changes of cells undergoing necrosis or apoptosis.gif; (pubs.niaaa.nih.gov) (Public Domain) via Commons Wikimedia

2. “Genotoxic Damage” By Genotox – Own work (CC BY-SA 3.0) via Commons Wikimedia