Difference Between Oncogene and Tumor Suppressor Gene

Key Difference – Oncogene vs Tumor Suppressor Gene
 

Oncogene and mutated tumor suppressor gene are the two types of genes that a cancerous cell possesses. An oncogene in its normal stage is referred to as proto-oncogene. Cancerous oncogenes result due to the activation (up regulation) of proto-oncogenes while tumor suppressor genes cause cancer when they are in the inactivated state. This is the key difference between oncogene and tumor suppressor gene that is related to the occurrence of cancer.

Cancer cells are defined as the cells possessing a relentless dividing mechanisms that converts them into solid tumors. They possess two major types of genes that involved in the transformation of a normal cell into a cancerous or malignant form. They are oncogene and mutated tumor suppressor gene. Oncogene and tumor suppressor gene differ from each other in a number of ways such as the pattern of inheritance, the mechanism of function, etc. The function of the proto-oncogene is to allow the cell to grow. But when the proto-oncogene gets mutated, it is converted into cancer-causing oncogene. The same principle lies behind tumor suppressor genes where they function to regulate the cell division in their normal format, but due to mutations within the gene, it gets converted into another type of gene that stimulates uncontrolled cell division.

CONTENTS

1. Overview and Key Difference
2. What is an Oncogene
3. What is a Tumor Suppressor Gene
4. Similarities Between Oncogene and Tumor Suppressor Gene
5. Side by Side Comparison – Oncogene vs Tumor Suppressor Gene in Tabular Form
6. Summary

What is an Oncogene?

A proto-oncogene is a normal gene that codes for a particular protein. This protein mainly involves cellular division process. Since the cellular division process consists of many steps, the presence of the protein is very important in the context of process regulation. Considering the properties and the respective functions of this protein coded by a proto-oncogene, it is an essential protein for the initiation cell division. Other than the initiation of cell division, proto-oncogenes involve in the regulation of apoptosis; programmed cell death. Therefore, proto-oncogenes are normal genes that involve major cellular activities. But once proto-oncogenes are mutated, they transform into oncogenes that possess defective functions. Hence, oncogene can be defined as a gene that has the potential to cause cancer. Once the proto-oncogene becomes abnormal (oncogene) it does not respond to the stop signals that are given by the tumour suppressor genes.

The oncogene codes for a different protein and results in the production of a protein that will stimulate cell division continuously. This unregulated cell division leads to the development of cancer. The significant fact about the oncogene is that it can stimulate the unregulated cell division through only one altered copy of its gene.

A single oncogene has the potential to develop into a tumor regardless of the stop signals. A faster-growing tumor happens due to the presence of two oncogenes or one oncogene plus one mutated tumor suppressor gene.

What is a Tumor Suppressor Gene?

A tumor suppressor gene is defined as a normal gene that is found in the cells of the body. It is also termed as antioncogene. Tumor suppressor gene could be transformed into a tumour causing gene if it undergoes a mutation. In its normal stage, tumor-suppressing gene works in the regulation of the cell cycle in various ways such as slowing down of the cell cycle, marking of cells for apoptosis, the coupling of the cell cycle to DNA damage, repairing of DNA, etc. In the context of slowing down the cell cycle process, the tumor suppressor gene encodes for a special protein that results in providing a ‘stop’ signal that suppresses cell division when it is necessary.

It is important that the produced protein should be normal to stop cell division. But if a mutation occurs within the tumor suppressor gene, then the genes are converted to an abnormal stage where it is referred to as cancer-causing tumor suppressor gene. This abnormal gene codes for a different protein and that particular protein does not provide the essential stop signal to the cell division process. This results in uncontrollable cell division that is similar to oncogene function.

The significant feature of tumor-suppressing gene is that it causes cancer in its inactivated form. Also, unlike the oncogene, tumor suppressor gene needs two mutated alleles  for the development of cancer. A single mutant gene is not sufficient for this since the other normal allele will code for the correct protein that is necessary to produce the stop signal of the division process.

What are the Similarities Between Oncogene and Tumor Suppressor Gene?

• Both Oncogene and Tumor Suppressor Gene in their normal forms are essential types of genes for many cellular functions.
• Both Oncogene and Tumor Suppressor Gene in their mutated form result in cancer.

What is the Difference Between Oncogene and Tumor Suppressor Gene?

Summary – Oncogene vs Tumor Suppressor Gene

Cancer cells show uncontrollable cell division that leads to the development of solid tumors. Oncogene and mutated tumor suppressor gene are the two types of genes that cause cancers. An oncogene is defined as a mutated proto-oncogene that has the potential to develop into cancer. Proto-oncogenes are normal genes. Mutation in one of the alleles of the proto-oncogene leads to the conversion of proto-oncogene into oncogene and the development of cancer. A tumor suppressor gene is defined as a normal gene that is found in the cells of the body. It produces a stop signal that needs to control the cell division. Hence, tumor suppressor genes are also known as antioncogenes. But when a mutation occurs in both alleles of the gene, it could be transformed into a tumor causing gene. This is the difference between oncogene and tumor suppressor gene.

Reference:

1.Cooper, Geoffrey M. “Tumor Suppressor Genes.” The Cell: A Molecular Approach. 2nd Edition., U.S. National Library of Medicine, 1 Jan. 1970. Available here 
2.Britannica, The Editors of Encyclopaedia. “Oncogene.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., 3 Mar. 2017. Available here 
3.Cooper, Geoffrey M. “Oncogenes.” The Cell: A Molecular Approach. 2nd Edition., U.S. National Library of Medicine, 1 Jan. 1970. Available here 

Image Courtesy:

1.’Oncogenes illustration’ (Public Domain) via Commons Wikimedia