GENE

“Get to know genes, basic knowledge of genes
and types of genes involved in cancer”

Knowledge
About Genes

Genes are pieces of DNA inside our cells which act like a blueprint controlling how cells function. Each gene normally carries information of heredity. We inherit two sets of genes from our parents. This is how traits are passed on from one generation to another. Researchers have estimated that we each have over 25,000 protein-coding genes which explain our differences and diversity.

“Genes” instruct each cell to produce a particular protein for a particular function. They are our personal codes to ensure correct protein production.

Changes in genes, called genetic mutations, play an important role in the development of cancer. Genetic mutations can cause a cell to make (or not to make) particular proteins that affect how the cell grows and divides into new cells. This causes miscommunication which leads to irregular cell division and rapid growth without control which can eventually turn to be cancerous cells.

Genes that
cause cancer

Generally, there are three main types of genes which can cause cancer :

  • Oncogene

  • Tumor suppressor gene

  • DNA mismatch repair gene

Oncogene

Among our genes, there is one called proto-oncogene which controls normal cell growth. When a gene in this group mutates, it can become “an oncogene” causing the particular cell to divide itself and grow rapidly out of control, resulting in cancer.

Related types of cancer

Lung cancer

Related types of cancer

Leukemia

types of cancer

Lung cancer

Colorectal cancer

Related types of cancer

Lung cancer

Breast cancer

Gastric cancer

Liver cancer

Related types of cancer

Liver cancer

Kidney cancer

Lung cancer

Tumor suppressor gene

When functions normally, tumor suppressor gene is responsible for:
- Regulating cell division
- Controlling self-elimination process of expired cells defined as cells with abnormal DNA or chromosomes which can no longer be repaired.

When this type of gene mutates, there is no control over cell division and destruction of the expired cells. Subsequently, cells become malfunctioned which can then lead to cancer. Most of the hereditary cancers are caused by the abnormality of this type of gene.

Adrenal cancer

Breast cancer

Brain tumor

Colorectal cancer

Liver cancer

Breast cancer

Ovarian cancer

Pancreatic cancer

Colorectal cancer

Breast cancer

Kidney cancer

DNA mismatch repair gene

During a cell replication process, DNA synthesis is a highly complex process in which an error can easily occur and result in a mutation in the cell cycle.

Normally, protein produced by a DNA mismatch repair gene works by fixing or repairing the errored DNA and some forms of DNA damage.

If the gene functions regularly, the cell with damaged DNA can be repaired by our body. However, if the gene itself mutates and becomes malfunctioned, it loses the ability to repair itself. More importantly, if the flawed gene is an oncogene or a tumor suppressor gene, it may eventually become cancer.

Breast cancer

Gastric cancer

Colorectal cancer

Acute myeloid leukemia

Genes mutation and Cancer

Genetic mutations are changes in the genetic sequence occurring in the genetic material. Genetic mutations are a main cause of diversity among organisms which is crucial for the evolutionary process of living organisms. However, these changes may develop at many different levels, leading to widely different consequences. For instance, certain genetic mutations can lead to changes in the appearance (phenotype), which may be the shape, appearance or behavior. Certain traits that cause mutations may aid in adapting to live in a changing environment. Nevertheless, some genetic mutations result in protein malformation or malfunction, causing certain hereditary diseases or conditions.

There are two main types of gene mutations
which can result in cancer.

Germline
mutations

Germline mutations are inherited mutations that are passed directly from one generation to another, from parents to children. Germline mutations are present from birth and these mutations will not change for as long as one lives. Heredity mutations account for 5-10% of all cancers.

Somatic
mutations

Since somatic mutations are acquired mutations which do not come from parents, these mutations are not passed to the next generation. Somatic mutations are mainly caused by external or environmental factors, including cigarette smoking, being exposed to pollution over a period of time, UV or radiation exposure, certain viral infections (e.g. HPV or human papillomavirus) and ageing.

Genes can mutate at all times. Our body normally has an ability to repair and eliminate abnormal or malfunctioned cells. Whether a mutation results in cancer or not, it depends on a location on particular gene where the mutation takes place and how it affects the function of that gene.

A single mutation on one gene does not normally lead to cancer. Cancer cells are, in fact, a result of several mutations on different locations of different genes that can happen anytime.

Breast Cancer and Mutation of
BRCA1 and BRCA2

BRCA1 and BRCA2 are tumor suppressor genes. They are responsible for ensuring that cells grow consistently at a normal rate. If these genes mutate, it can potentially result in hereditary breast cancer and ovarian cancer.

Women with mutated
BRCA1

Risk to develop
breast cancer increases
by 60-80%

Risk to develop
ovarian cancer increases
by 30-45%

Women with mutated
BRCA2

Risk to develop
breast cancer increases
by 50-70%

Risk to develop
ovarian cancer increases
by 10-20%

Men with mutated
BRCA1 and BRCA2

Risk to develop
breast cancer increases
by 1-10%

Risk to develop
pancreatic cancer increases
by 2-5%

Next-Generation Sequencing (NGS)

The latest and well-acknowledged genetic
mutation detection technique

Currently, cutting-edge technology and medical advancements have constantly emerged. Genetic studies are able to identify exact changes in DNA sequence and their consequences associated with hereditary risks, enabling precise interventions and disease prevention to be performed in a timely manner.

Next-Generation Sequencing (NGS) is the latest and well-acknowledged genetic mutation detection technique used in genetic field for a wide range of purposes. NGS is a parallel sequencing technology that offers ultra-high throughput, scalability and speed. The technology is used to determine the sequence of nucleotides in entire genomes or targeted regions of DNA or RNA. Moreover, NGS can also sequence unknown nucleotides, enabling more comprehensive detection of mutations than other sequencing techniques.

Next- Generation Sequencing (NGS) technologies include:

Whole Genome
Sequencing (WGS)

Whole-Genome Sequencing (WGS) or full genome sequencing is used to study the sequencing of whole genome nucleotides in our body, including both the coding region (exon) and the non-coding region. However, WGS is considered costly technique. In addition, due to a large amount of genetic information, WGS takes a long time to analyze the whole data. More importantly, certain changes in the nucleotide sequence in the non-coding region are often difficult to explain or to draw a conclusion since it is the portion of DNA that is not encoded into a protein.

Whole Exome
Sequencing (WES)

Whole-Exome Sequencing (WES) is a widely used NGS method that involves sequencing the protein-coding regions of the genome which are often associated with the diseases. WES technology has been currently applied to a wide range of applications, such as identifying single gene disorders (Mendelian inheritance disorders), identifying susceptibility genes and mutations of cancer related genes. In comparison to WGS, WES technology becomes more popular in diagnostic tests and researches as WES is considerably cheaper and obtained data from WES takes less time to analyze.

Targeted Gene
Sequencing

Targeted Gene Sequencing is a sequencing technique that studies nucleotide sequences in specific genes which are related to the diseases. Nowadays, Targeted Gene Sequencing is used for diagnosis and research in oncology (cancer gene panel), for example, lung cancer panel, leukemia panel and breast cancer panel. In breast cancer, Targeted Gene Sequencing helps to detect the mutation of BRCA1 and BRCA2 genes that are proven to significantly increase risk of developing hereditary breast cancer and ovarian cancer.

"WGS, WES and Targeted gene sequencing are the most popular techniques used in genetic analysis. Furthermore, there are several types of NGS technologies, such as Transcriptome Sequencing (RNA-seq), Epigenomic Sequencing and Metagenome Sequencing.

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