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The Future of Health: Why Genetic Testing Matters

Empowering Health Decisions: How Genetic Testing Can Guide You

The Power of Genes: Exploring Genetic Testing Options

Genetic testing may be useful in determining whether an individual has a genetic condition or may develop one in the future.

Our body is made from millions of tiny cells. Each cell is controlled by thousands of genes. We have over 20,000 genes which are in every cell of our body and serve different functions.

As we get older, we develop mutations within our genes – some are caused by outside factors like smoking or sun damage, while others happen at random. Genetic testing identifies changes in our genes or chromosomes, that are called mutations or variants.

Genetic testing has potential benefits, whether the results are positive or negative. Getting tested may:

  • help you better understand your risk of cancer
  • relieve your anxiety or uncertainty about disease risks like cancer, diabetes
  • help you make decisions about your health and learn ways to help lower your risk of diseases
  • help other family members decide if they should get tested or learn about how to lower their risk of certain diseases
  • lead to finding cancer earlier when treatment is most likely to work better

When it comes to health and disease — and, of course, many other aspects of life — one thing is certain: genes matter.

Types of Genetic Tests and Why Are They Important?

There are many kinds of genetic tests. Limitations to that, there is no single genetic test that can detect all genetic conditions.

The approach to genetic testing is individualized based on your medical and family history and what condition you’re being tested for.

Single gene testing. Single-gene tests look for changes in only one gene. Single-gene testing is done when your doctor believes you or your child have symptoms of a specific condition or syndrome that is well-established for single-gene disorder. Some examples of this are Duchene muscular dystrophy and sickle cell disease. Single-gene testing is also used when there is a known genetic mutation running in a family.

Panel testing. A panel genetic test looks for changes in many genes in one test. Genetic testing panels are usually grouped into categories based on different kinds of medical concerns. Some examples of genetic panel tests are low muscle tone, short stature, or epilepsy. Panel genetic tests can also be grouped into genes that are all associated with a higher risk of developing certain kinds of cancer, like breast or colorectal cancer, etc.

Large-scale genetic or genomic testing. There are two different kinds of large-scale genetic tests.

  • Exome sequencing looks at all the genes in the DNA (whole exome) or just the genes that are related to medical conditions (clinical exome).
  • Genome sequencing is the largest genetic test and looks at all of a person’s DNA, not just the genes.

Exome and genome sequencing are ordered by doctors for people with complex medical histories. Large-scale genomic testing is also used in research to learn more about the genetic causes of conditions.

Comparison and benefits of Gene testing:

Genetic testing is the key to understanding our genes, providing a window into our past, guiding our present health decisions, and illuminating a path toward a healthier future.

BRCA Genes: Understanding Your Risk for Cancer

Deep DIVE into BRCA Genes: Function, Variants, and Impact on Cancer

The BRCA Mutation Landscape: Understanding Variants and Their Effects

BRCA is one of the well-studied tumour suppressor gene. There are two BRCA gene one is BRCA1 and another is BRCA2. BRCA1 and BRCA2 are involved in maintenance of genome stability, specifically the homologous recombination pathway for double-strand DNA repair.

BRCA1 gene encodes a 190 kD nuclear phosphoprotein, this gene contains 22 exons spanning about 110 kb of DNA. Mutations in this gene are responsible for approximately 40% of inherited breast cancers and more than 80% of inherited breast and ovarian cancers. BRCA1 mutations in the germline have become a hallmark for hereditary breast and ovarian cancers. The BRCA2 gene was found on chromosome 13q12.3 in human.

Newer dimension of studies could relate that pathogenic germline variants and clinically significant somatic mutations of HRR genes turn cancer cells susceptible to PARP inhibitors (PARPi) and other evolving targeted therapies. Testing HRR genes for genetic variants has thus acquired greater importance in risk stratification and treatment decision-making.

BRCA1- and BRCA2-associated hereditary breast and ovarian cancer (HBOC) is characterized by an increased risk for female and male breast cancer, ovarian cancer (including fallopian tube and primary peritoneal cancers), and to a lesser extent other cancers such as prostate cancer, pancreatic cancer, and melanoma primarily in individuals with a BRCA2 pathogenic variant.

The screening/diagnosis of BRCA1- and BRCA2-associated HBOC is considered in a person by identification of a heterozygous germline pathogenic variant in BRCA1 or BRCA2 on molecular genetic testing.

Breast cancer is one of the most common type of cancer in women it accounts for 12.5% of all new annual cancer cases worldwide. About 13% (1in 8) of U.S., women develop invasive breast cancer in the course of their life (1).

However, many other factors may play an important role in increase the risk of cancer, such as smoking, chemical exposure, alcohol consumptions etc.

In the US in 2023, invasive breast cancer will be diagnosed in an estimated 297,790 women and 2,800 men, with an additional 55,720 cases of ductal carcinoma in situ (DCIS) diagnosed in women. As per the American cancer society: “Cancer Facts & Figures 2023” An estimated 43,700 breast cancer deaths (43,170 in women, 530 in men) will occur in 2023. The breast cancer death rate among females high in 1989 and has since declined by 43% as of 2020, credit goes to earlier detection through screening mammography, as well as increased breast cancer awareness and improved treatment. This decrease translates to approximately 460,000 fewer breast cancer deaths during this time period than would have been expected in the absence of this progress. However, mortality rates in Black women remain about 40% higher than in White women, despite lower incidence (1).

Everyone has BRCA1 and BRCA2 genes. This codes for proteins that plays an important role in repairing damaged DNA. Mutated BRCA1 at ~55-65% high risk of cancer where normal patient getting cancer risk is only 12%. In case of mutated BRCA2 cancer risk is ~45%. Individuals with BRCA gene mutations tend to be diagnosed with more aggressive cancer at a younger age, often within 30s-40s.

How this test will help me?

Studies showed evidence that people with BRCA gene mutations have such significantly increased risks of breast and ovarian cancer, thus, testing for BRCA gene mutations strong step in personalizing cancer screening and risk management based on genetic risk factors. Individuals with a strong family history of breast and/or ovarian cancer are generally referred by their doctor to a genetic counsellor. This helps them to understand a detailed family medical history and use mathematical models to estimate that individual’s personal cancer risk.

What if I am found to be positive for BRCA mutation?

A person having a positive pathogenic mutation in BRCA gene typically undergo more frequent screening for breast cancer, usually mammogram and MSI every year. There are even evidences, Some women with BRCA gene mutations and a strong family history of cancer decide to undergo preventive mastectomies and oophorectomies (removal of ovaries) to reduce their future risk of developing cancer. This was very well noticed during Angelina Jolie’s decision on her mastectomy. With her public noticed awareness for BRCA positive condition (3).

What technique is best for testing?

Testing of BRCA is done by specialized genetic testing. Traditionally it was done by amplifying the copy of gene, followed by Sanger’s sequencing. Still this technique is considered as gold standard. However, this technique might be time consuming and for somatic condition in tissue, we might not be able to detect low mutation content level due to technique limitations. Recent addition of the newer techniques such as massively parallel sequencing/Next generation sequencing have allowed scientist to utilized its benefit to move towards the precision medicine dependent therapeutic approach (4).

What is HRR & why HRR testing is required?

Understanding Homologous Recombination Repair (HRR) and Its Testing Importance

Delving into HRR: A Cellular Mechanism for DNA Repair

Homologous recombination and DNA repair (HRR) are crucial for genome maintenance. Homologous recombination DNA repair is a process by which double-stranded DNA breaks and inter strand crosslinks use sister chromatids as a template for repair, thus it helps in removing DNA damage in an error-free fashion. The deficiency in the HRR pathway leads to Homologous recombination deficiency (HRD) that is associated with several tumor types like breast, ovarian, prostate, and pancreatic cancers.

Why HRR testing is required?

Poly (ADP-ribose) polymerases (PARPs) are members of related enzymes that catalyze the transfer of ADP-ribose to target proteins. PARP1 and PARP2 play an important role in maintaining genomic stability by mediating DNA repair processes. Among the PARP families, PARP1 shows abundant expression compared to the others and is responsible for most of the cellular PAR formation.

Newer dimension of studies could relate that pathogenic germline variants and clinically significant somatic mutations of HRR genes turn cancer cells susceptible to PARP inhibitors (PARPi) and other evolving targeted therapies. Testing HRR genes for genetic variants has thus acquired greater importance in risk stratification and treatment decision-making.

PARPi are targeted therapy drugs that interact with PARP enzyme in the cells, where they interact with the NAD+ binding site. This helps in the inactivation of PARP thereby inhibiting cell growth and cell death. This targeted therapy reduces the side-effect too.

US FDA-Approved PARP inhibitors available for treatment:

Olaparib (Lynparza)

Talazoparib (Talzenna)

Rucaparib (Rubraca)

Niraparib (Zejula)

Why HRR testing is required?

PARP enzymes are integral to the base excision repair pathway, where it repairs the single-strand breaks in DNA. The unrepaired single-strand breaks result in the formation of double-strand breaks, which are repaired through the HRR pathway as mentioned above.

Deficiency in synthetic lethality is a mechanism through which the PARP inhibitors target the tumor cells selectively. The preferential targeting of tumour cells thereby spares the healthy cell, thus providing the patients with benefits that are not achievable through conventional chemotherapy. This help the clinician to decide on the targeted therapy option for patient whether the patient is eligible for PARP inhibitor therapy and increases the chance to fight the cancer with FDA approved PARP inhibitors.

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