Is Cancer Hereditary? – Here’s What You Need To Know About Hereditary Cancers
It is a common notion that cancer is hereditary because it is genetic. This is only partially true.
As per Cancer.gov, 5 to 10 percent of cancers are hereditary. Cancer is an error or change in the genes encoding protective proteins. But only a small percentage of them are hereditary.
Besides, only certain types of cancers can be inherited. There are various genetic and environmental factors involved that decide whether cancer is hereditary or not.
What types of cancer are hereditary? Is cancer hereditary from parents? Which genes are involved in the development of cancer?
In this article, we will discuss the relationship between cancer and genetics, the types of cancer that are hereditary, and their genetic bases.
Is Cancer Hereditary?
Not all cancers are hereditary. Almost 5 to 10 percent of cancers are believed to be hereditary. In these cancers, tumour suppressor genes or growth control genes with errors or mutations are inherited from a parent. In the rest of the cancers, the mutation in genes is acquired.
The hereditary nature of cancer also depends on its type. Skin and lung cancers are not hereditary, while almost 20 percent of ovarian cancers are hereditary. Almost 15 to 20 percent of cancers are familial.
Familial cancers occur in the same family due to shared environmental conditions, which expose them to the same carcinogens.
Acquired cancer mutations may be the result of excessive hormonal stimulation, chemical exposure such as carcinogens in cigarette smoke, or infrared radiation exposure.
It can also result from an interplay of various risk factors, including diet, environment, aging, and obesity.
Genetics and Cancer
Genes are the sequences of nucleotides that encode proteins. These proteins perform various structural and functional roles inside the cells. Errors or mutations in these sequences, called genes, can give rise to serious pathologies, including cancer.
When a cell cannot properly divide, genes and gene products such as RB and p53 come into action. They stop the cell division or induce voluntary cell death by a process called apoptosis. In this way, these genes prevent tumour formation.
Tumour suppressor genes and their product proteins are also involved in correcting errors in DNA that can develop during one’s lifetime.
For instance, ultraviolet and infrared radiations from the sun can damage DNA. But the tumour suppressor genes will get rid of the error before the DNA replicates.
If the tumour suppressor genes are absent, the error will survive, and the faulty DNA will replicate, leading to the development of cancer.
Cancer is specifically caused when the tumour suppressor or growth controlling genes are mutated enough to produce faulty proteins or decrease the production of protective proteins.
In the absence of the protective checkpoints during the cell division cycle, a fault in the gene or the cell survives until the cell produces thousands of cells like itself.
The mutations can be of various kinds. A single nucleotide can be absent or misplaced. Errors may occur with longer stretches of DNA, such as deletions and duplications.
Regardless, these different kinds of mutations can occur in two types of cells: somatic or germline.
Germline mutations occur in the reproductive cells; the egg, sperm, or their progenitor cells. Somatic mutations are the gene errors that occur in all other cell types.
Germline mutations can be inherited, while somatic mutations cannot. But various types of somatic cancers in the same family increase the chance or risk of developing cancer.
What is Hereditary Cancer?
Cancerous mutations in the genes that are passed from the parent to the offspring are said to be hereditary.
When the sperm fertilises the egg, and one of them has a gene mutation, the zygote that forms also carries it. The zygote divides millions of times to form offspring. And all cells of the offspring now carry the gene mutation. This is called hereditary cancer.
Every gene in our genome, or DNA, has two copies. When only one parent has the mutation, there is a 25% chance the offspring starts with one mutation already there. And there is a greater probability that the second copy will also mutate sometime during life, and cancer finally develops.
In other words, this individual has only to develop one more mutation to develop cancer. So, the risk of developing cancer is several times higher than in normal individuals.
When both parents carry the mutated gene, and somehow both copies of the gene received by the offspring are mutated, the offspring can definitely develop cancer early in life.
Cancers in the same family can also result from exposure to the same conditions, such as tobacco smoking or obesity. But they can also be linked to inherited gene mutations, a case called family cancer syndrome.
Genetic Testing for Cancer
Genetic testing employs various medical tests and techniques to spot mutation in a person’s genes. It has been one great medical breakthrough in history, and the research is still going on.
Genetic testing is of four main types:
1. Chromosome Studies evaluate the number and structure of the 46 chromosomes of a human cell. There can be an extra or missing copy of a chromosome (trisomy or monosomy), or segments of chromosomes may be misplaced (translocation).
2. DNA studies detect errors in DNA, such as gene duplication and deletion. A small nucleotide sequence can be repeated or absent.
3. Biochemical Genetic Studies involve enzymes, enzyme functions, and defects. Elevated levels of certain enzymes and hormones suggest gene disorders.
4. Gene Expression Tests evaluate the genes that are over or under-expressed. These tests study the abnormal amounts of messenger RNA to determine the overexpressed or under-expressed regions of genes, which suggest genetic disorders.
Genetic testing is regular in people with cancer. Cancerous cells are tested for gene changes to predict the prognosis of the disease or if further gene mutations are developing with rapidly dividing cancer cells.
But the more important clinical application of gene testing is the genetic tests that can point out and predict the risk of developing cancer.
Predictive Genetic Testing
If one of the parents has a mutated gene or even paired gene mutation and cancer, the offspring can be carriers. Gene testing at an early age can help prevent the individual from developing cancer.
Gene mutation detection, however, does not confirm that someone will definitely develop cancer. It only tells if you have a higher risk than others of developing a certain type of cancer.
Predictive gene testing is most commonly conducted for BRCA gene mutations involved in breast cancer development and inheritance. It can be detected any time after birth because it comes from the parents.
BRCA 1 and BRCA 2 Genetic Mutations
BRCA 1 and BRCA 2 (Breast Cancer Genes 1 and 2) gene mutations are important examples of inherited gene mutations. These mutations increase the risk of developing breast and ovarian cancer in women, a condition called hereditary breast and ovarian cancer syndrome.
- Every 50 in 100 women with a BRCA gene mutation will develop breast cancer in their 80-year life span.
- Every 30 in 100 women with a BRCA gene mutation will develop ovarian cancer sometime in their life.
BRCA 1 and BRCA 2 gene mutation carrier women only have to develop one more mutation to develop cancer. This is how breast and ovarian cancer risk increases several times for mutated gene carriers.
Men can also be carriers of the BRCA gene mutations, but only 1 percent of breast cancers occur in men. Carriers, however, are at increased risk of developing several other types of cancers such as prostate, pancreatic, and melanoma.
Gene errors such as DNA breaks and replacements occur during cell division. Tumour suppressor genes and gene products such as BRCA 1 and BRCA 2 are involved in the repair of this damaged DNA.
When both copies of these tumour suppressor genes are altered, gene errors replicate, and thus tumour develops.
TP53 and RB Gene Mutations
TP53 and RB tumour suppressor genes are two tumour suppressor genes that keep the cell division in check. TP53 encodes the p53 protein that instructs the cell to die or stop dividing when it detects a bug in the DNA. RB gene encodes RB protein that acts as a checkpoint at various stages of the cell cycle.
Acquired forms of TP53 gene mutation are involved in various types of cancers. However, the inherited type of this gene mutation is rare and is called La-Fraumeni syndrome.
RB gene mutation is hereditary, and it causes a type of eye cancer called Retinoblastoma. RB gene mutation inheritance has the same pattern as germline mutations.
What Types Of Cancer Can Run In Families Because Of Genetics?
Certain types of cancers are hereditary. For those, too, a certain percentage is hereditary, and the rest can be acquired any time after birth.
Below is a list of cancers that run in the families because of genetics:
Breast Cancer And Ovarian Cancer: Brca 1 And Brca 2 Gene Mutations
Colon Cancer: Growth Of Polyps In The Colon
Prostate Cancer: Characterized By Overactivity And Enlargement Of Prostate
Melanoma (A Type Of Skin Cancer)
Pancreatic Cancer: Pancreatic Cells Grow And Invade Surrounding Tissues
Bone Cancer Can Also Be Caused By Radiation Exposure
Brain And Spinal Cord Cancers Develop By The Spread Of Cancers From Other Parts Of The Body
Colorectal Cancer: Cancerous Mass Forms In The Colon And Rectum
Eye Cancer Such As The Inherited Retinoblastoma
Fallopian Tube Cancer Is The Primary Form Of Ovarian Cancer That Develops Where The Eggs Enter From The Ovary
Leukemia And Lymphoma: Types Of Cancers Associated With The Blood Cells
Hepatoblastoma (Abnormal Tissue Growth Of The Liver That Affects Children)
Neuroblastoma: A Congenital Defect With Strong Hereditary Factor
Neuroendocrine Tumors Originate In The Parts Of The Body That Secret Important Hormones. They Are Most Common In The Intestines.
Pituitary Gland Cancer Develops When A Person Has Some Other Type Of Inherited Cancer.
Rhabdomyosarcoma Is A Rare Type Of Cancer That Develops In Hollow Organs Such As The Bladder.
Soft Tissue Sarcoma, Which Is The Cancer Of Muscle, Fat, Lymph, And Blood Vessels. It Is Mostly Found In The Limbs And Abdomen.
Testicular Cancer Is The Cancer Of The Male Gonads That Develops At An Early Age And Has A Strong Link With Family History.
How Do You Know If Cancer In A Family Is Hereditary?
The presence of multiple forms of cancer in a family or the same pattern of cancer development indicates hereditary cancer. More aggressive forms of cancer also point at inherited gene mutations.
Following are some common signs of hereditary cancers:
1. Family members from the same side are diagnosed with cancer
2. Cancer is of the same type or origin
3. Diagnosis is at early ages
4. Cancer is of different types but is genetically related, such as breast and ovarian cancer
5. A single family member is diagnosed with different types of cancer
6. Cancer runs across many generations.
If you think that particular cancer runs in your family, consult your physician. They will record the signs and patterns and suggest gene tests for that purpose.
If you happen to be carrying the mutated gene copy, the doctor can prescribe you medications, lifestyle changes, or sometimes surgery to manage the risk.
Testing for Inherited Cancers
Genetic testing can reveal if you have a specific mutation or altered gene if more than two members of your family have developed the same type of cancer. Your doctor will suggest gene testing if the signs of hereditary cancers mentioned above are observed.
As discussed above, mutations in the germline cells have significance in inheritance. So genetic testing for inherited cancers involves germline testing.
Germline testing analyses blood because blood cells contain genes that come from the mother’s egg and the father’s sperm. Germline mutations can be detected any time after birth.
In contrast, somatic testing detects gene changes for certain types of cancers acquired after birth.
If You Have Cancer, Will Your Children Get Cancer?
The children inherit gene mutations that occur in the germline or reproductive cells. But somatic mutations also have an increased risk and rate of occurrence when cancer runs in the family due to exposure to the same conditions.
If you have cancer, it means that your body cells carry two copies of the mutated gene. There is a 50% chance you will transfer one copy of your mutated gene to your child only if the cancer is related to the germline cells, such as ovarian cancer.
In that case, the offspring will be a carrier. This does not confirm that he will develop cancer. But surely, he is at a higher risk than others.
But if your spouse also has cancer, they will transfer a copy of the mutated gene to 50 percent of the offspring.
In the case of a single mutated gene copy, the offspring has an increased risk of developing cancer, but no test can confirm that they will. With a double mutated gene, cancer will develop during the early years of the child’s life.
This pattern of inheritance is followed by both male and female parents and offspring of both sexes. But some cancers only occur in one of the sexes. Common examples include ovarian cancer that occurs in females only and prostate cancer in males.
But an offspring of any sex can be a carrier. They may not develop the disease but can pass the gene on to the next generation.
The Bottom Line: Is Cancer Hereditary?
Cancer is a genetic disease, but only some cancers are hereditary. Some of them run in families because of hereditarily high levels of certain hormones that give rise to cancers or exposure to the same conditions such as high-cholesterol foods. Others are hereditary because they are caused by a gene mutation in the germline cells.
Hereditary cancers can be tracked with the help of some signs and confirmed by gene testing. If you have cancer, your child may be a carrier, but it is not definite that he will develop cancer. In cases where both parents carry the same cancer, there is a high probability of developing cancer.
