What is the Difference Between HER2 and BRCA

The key difference between HER2 and BRCA is that HER2 is a gene present in chromosome 17 in humans that undergoes somatic mutations to cause nonhereditary breast cancer, while BRCA represents the two genes BRAC1 and BRCA2 present in chromosome 17 and 13, respectively, that undergo germline mutations to cause hereditary breast cancers.

Breast cancer is a type of cancer that arises from breast tissues. It is predominantly identified in women throughout the world. The signs include a change in breast shape, lumps in the breast, and red scaly patches in the skin. Substantial support for breast cancer awareness and research funding have created a better prognosis of breast cancer. There are different types of breast cancers due to somatic and genetic mutations of important genes. HER2 and BRCA are genes that mutate to create breast cancer.

CONTENTS

1. Overview and Key Difference
2. What is HER2  
3. What is BRCA
4. Similarities – HER2 and BRCA
5. HER2 vs BRCA in Tabular Form
6. Summary – HER2 vs BRCA

What is HER2?

HER2 is a gene present in the long arm of chromosome 17 (17q12) in humans. This gene mutates somatically to cause nonhereditary breast cancer. HER2 stands for the human epidermal growth factor gene. It is a gene that produces a protein on the surface of the breast cells. This protein triggers normal cell growth. Genes are the basic units of hereditary, and they pass from parents to offspring. In certain cancers, such as breast cancer, the HER2 gene mutates and makes extra copies of the gene. This is known as over-amplification.

When this happens, the HER2 gene makes too many HER proteins, which triggers breast cells to divide and grow too fast. Breast cancers with high levels of HER2 protein are named HER2 positive. Moreover, breast cancers with low levels of expression of HER2 protein are known as HER negative. About 20% of breast cancers are HER2 positive. The diagnosis of this condition can be made through biopsy, immunohistochemistry, in-situ fluorescence hybridization, and the HER2 gene mutation test. Most women who have HER2 positive breast cancer will receive chemotherapy drugs and trastuzumab (anti-HER2 antibody) as treatment.

What is BRCA?

BRCA1 and BRCA2 are two different genes present in chromosomes 17 and 13, respectively. BRCA stands for breast cancer genes. Hereditary breast cancers occur due to germline mutations of these two genes. DNA linkage studies first identified the BRAC1 gene in 1990. Later, in 1994, the BRCA2 gene was identified. Both these genes are typical tumor suppressor genes that control normal cell growth and cell death. The altered copy of either the BRCA1 or BRCA2 gene increases the risk for various types of cancers. BRCA1 gene mutation increases the risk of breast, ovarian, and prostate cancers. On the other hand, BRCA2 gene mutation increases the risk of breast, ovarian, pancreatic, prostate, stomach cancers, and melanoma.

Only a small percentage of people (about 0.25% of the population) carry the mutated copy of BRCA1 or BRCA2 genes. The BRCA gene test is a blood test to detect changes in BRCA normal genes. The FDA approved Olaparib is a drug that treats metastatic breast cancer with a germline BRCA mutation.

What are the Similarities Between HER2 and BRCA?

• HER2 and BRCA are two genes that mutate, causing breast cancers.
• The normal copies of these genes control cell growth.
• Both HER2 and BRCA1 genes are located in chromosome 17 of humans.
• Mutated HER2 and BRCA genes can cause different types of cancers other than breast cancer in humans.

What is the Difference Between HER2 and BRCA?

HER2 is a gene present in chromosome 17 in humans and mutates somatically to cause nonhereditary breast cancer, while BRAC1 and BRCA2 (BRCA) are two genes present in chromosomes 17 and 13, respectively and undergo germline mutations, causing hereditary breast cancer. So, this is the key difference between HER2 and BRCA. Furthermore, about 20% of breast cancers are due to HER2 mutation, while about 5 to 10% of breast cancers are due to BRCA mutation.

The following infographic lists the differences between HER2 and BRCA in tabular form for side by side comparison.

Summary – HER2 vs BRCA

Breast cancer is a type of cancer in which certain cells of the breast multiply abnormally to form a tumor. Breast cancer has both inherited and non-inherited causes. HER2 and BRCA are different genes that mutate to cause breast cancer. HER2 undergoes somatic mutations to cause nonhereditary breast cancer, while BRCA undergoes germline mutations to cause hereditary breast cancers. Thus, this summarizes the difference between HER2 and BRCA.

Reference:

1. “Her2 Status: Tests, Treatments, and More.” Breastcancer.org, 21 Sept. 2020.
2. “BRCA: The Breast Cancer Gene.” National Breast Cancer Foundation, 23 Oct. 2020.

Image Courtesy:

1. “FISH Her2” By IrinaPav – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “BRCA Genes” By Tessssa13 – Own work (CC BY-SA 4.0) via Commons Wikimedia