CJG Blog

Center for Jewish Genetics blog

What Causes Cancer?

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WhatCausesCancerBy Elianna Miller 

Approximately 1,762,450 new cancer cases will be diagnosed in the US in 2019. This number has grown rapidly since 2005, but what caused this increase? Is it people’s DNA, their environment, or is it just bad luck?

A lot of the Sarnoff Center’s work focuses on hereditary cancers, particularly BRCA mutations, which are 10x more common in Jewish communities than the general population. BRCA mutations are linked to breast cancer in women in men, ovarian cancer, prostate cancer, pancreatic cancer, and melanoma. The average woman’s lifetime chance of a breast cancer diagnosis is about 12%, but that increases to 45%- 87% with a BRCA mutation. Lynch syndrome is another inherited genetic disorder that can be linked to Ashkenazi Jewish ancestry, which increases the likelihood of some gastrointestinal cancers. 

If someone with a mutation such as these ends up developing cancer, it typically happens earlier in life than with the average person. Cancer predisposition genes are typically present from birth, though the actual cancer doesn’t form until later. That means there must be more to it than just genetic predisposition.

Let’s take a deeper dive into BRCA mutations. We all have BRCA genes: one copy from mom, and one from dad. If both parents give their daughter unmutated copies of the BRCA gene, she has that 12% risk of a breast cancer diagnosis in her life. The cancer risk increase happens with a mutation in one of the two copies: since only one copy of the mutation increases risk, inheritance happens in an autosomal dominant fashion.

So, why do some women with BRCA mutations develop breast (or another related) cancer, while others do not? The development of cancer in the body based on a predisposition usually manifests in a mechanism called the “two-hit theory.” The first hit is the mutation at birth, and the second hit is later in life when the cancer begins to form. The interaction of other factors, such as the environment or other genes in the body, with a preexisting cancer risk mutation may lead to or prevent cancer development.

Many environmental factors can cause a second hit. Sun or chemical radiation exposure, alcohol use, poor diet choices, the process of aging, or tobacco use are some of the most common. Sometimes, these risk factors don’t even cause mutations, they just change gene expression. Someone could live the healthiest of lifestyles, but the interaction of certain genes affects the way that tumors get suppressed. Researchers at Johns Hopkins also found that some tissues in the body are just more susceptible to “bad luck” and random DNA mutations that cause cancer.

The takeaway here is that while genetics can increase our risk of cancer, only about 5% of all cancers are due to underlying genetic causes. Of the 1,762,450 estimated cancer diagnoses this year, about 88,000 will have a direct underlying gene mutation, and almost one million cases will not. Our environment and random chance play a lot more into cancer diagnosis than one may expect; being positive for a genetic mutation that leads to cancer predisposition is NOT a diagnosis, just as being negative for one of these genes does NOT clear one of a lifetime cancer diagnosis. The team, and specifically the genetic counselor, at the Sarnoff Center is open and available to answer any questions or connect you to more resources related to cancer genetics.

Photo citation:  https://www.flickr.com/photos/genomegov/26453305264/ 

Some Food For Thought on Gene-Editing

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By Elianna Miller

In late 2018, “CRISPR babies” made news worldwide, and they are now coming back to the spotlight. When He Jiankui made genetically modified embryos that grew into twin girls with HIV immunity, people were outraged. He didn’t discuss his plans with his scientific community, and the procedure was deemed unnecessary and risky. These so called “CRISPR babies” were viewed with great controversy and caused a halt in the global scientific community on gene-edited embryos.

Now, Russian scientist Denis Rebrikov has announced his desire to produce CRISPR babies that can hear from parents with recessive genetic deafness. Because both parents have an altered copy of a gene related to hearing, any child they naturally conceive would be deaf, too. The participants want to provide their children with the ability to hear. Rebrikov plans to consult scientific communities and explain the benefits of the process, unlike He.

So, what is CRISPR? It’s a groundbreaking technology that is often seen in the news but less often well understood. Short for Clustered Regularly Interspaced Short Palindromic Regions, multiple repeats of the same 30 or so base pairs are separated by different genes of interest (spacers). Spacers serve as a guide for an enzyme, usually Cas9, to cut specific pieces of the genetic code. When this “faulty” DNA is cut, that gene is essentially turned off.

The cutting also acts as marking, and other molecular components can guide new DNA to that marked spot. This unfortunately doesn’t always work perfectly. Since there are so many repeats, the cutting enzyme can go to the wrong spot, editing unintentionally. Rebrikov still wants to use this process to insert “hearing genes” into embryos regardless of the imperfect mechanism.

Many ethical dilemmas arise here. There is no consensus on who gets to decide when CRISPR should or should not be used. Right now, the ability to hear is a product of environment and parental genes, and scientists like Rebrikov are attempting to change those factors with this new technology.

The Center for Genetics and Society talks about CRISPR in the context of disability rights, and the range of perspectives needed when making decisions about cutting genes from embryos. They note that removing genes linked to certain characteristics is marking them as tragic, implying impossibility of a good life. How can we respect people living with certain conditions that we are choosing to eliminate from others? Also, where do boundaries lie, and how do we draw the line on what genes can be edited? If we can edit out certain genetic disorders, what will stop us from selecting for certain eye colors, heights, or intelligence capacities? These are difficult questions that will be debated again and again as CRISPR gene editing technology advances and begins to touch more lives.

To learn more about CRISPR along with the research and ethics of it, sign up for the Norton and Elaine Sarnoff Center for Jewish Genetics’ event: CRISPR: Is Gene Editing Kosher? We will be discussing potential answers and the lack thereof for questions like these.




Tay-Sachs and Carrier Screening: How They Shaped the Jewish Community

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By Elianna Miller

Many people have heard of Tay-Sachs disease, but what have they heard? Some are aware of the connection to Jewish ancestry and the devastation related to diagnosis. However, most don’t know about the history and cause of the disease, or the steps the Jewish community has taken to nearly eliminate it from our population. Community health organizations, like the Sarnoff Center, have provided resources to make this happen.

What is Tay-Sachs Disease?

Babies born with Tay-Sachs Disease experience slow nervous system deterioration, which diminishes cognitive functioning. This is usually seen as the loss of motor skills, vision, hearing, and strength someone had previously developed. Near the end of the 19th century, the researchers Warren Tay and Bernard Sachs worked separately but both contributed to the discovery of the disease. Sachs also noted the prevalence in Jewish populations. Because of the fatality, the search for a cause and a cure was on.

Fast forward to August of 1969, Drs. Okada and O'Brien found the enzyme that babies with Tay-Sachs lack: Hexosaminidase A. It is responsible for breaking down lipids (fat) in the brain and spinal cord. They become toxic if not broken down, which explains the destruction of the nervous system. Tay-Sachs is autosomal and recessive because as long as there is at least one functioning copy of the gene, Hexosaminidase A is produced to remove toxins. The problem arises when there are no enzyme producing copies. This discovery, along with the fact that about 1/30 Ashkenazi Jewish people are carriers (compared to 1/300 of the rest of the population), catalyzed people to do something. The realization of the link to Jewish ancestry led to an understanding in the scientific community that other genetic disorders are more prevalent in other specific populations, too.

So, Tay-Sachs is more common in Jewish populations. What does this mean?

The first community carrier screening event was held in 1971 at a synagogue in Maryland. Trained volunteers and physicians drew blood from over 1,500 people, which revealed if they had a possibility of having a child with Tay-Sachs. For the first time, people had knowledge about personal risk of having affected kids. Other Jewish communities wanted to do something similar.

The number of babies born with Tay-Sachs has reduced over 90% in the last 50 years. The reduction of cases of Tay-Sachs is not due to a cure, as there is not one yet. Carrier frequency in Jewish populations also has not changed. It is due to people being more educated about personal risk and taking the time to learn what they can do for prevention.

How does the Norton & Elaine Sarnoff Center for Jewish Genetics play into all of this?

The Center was founded in 1999 as an educational resource for genetic health risks in the Chicago Jewish population. Screening began shortly after that for only the 4 most common Jewish genetic disorders including Tay-Sachs. That number jumped to 19, then later to about 50. Today, there are around 80 “Jewish” disorders that we know of, and the Sarnoff Center screens for those and about 120 pan-ethnic disorders. One out of four Ashkenazi Jewish people are a carrier for at least one of these.

Since the beginning, we put on community health screening events much like the one in Maryland. A presenter would explain the importance of screening and make sure everyone went through the informed consent process during a dinner, and before leaving they would participate in a blood draw. However, these blood draws are no longer needed because screening can be done with a spit kit from home. Fun and interesting educational resources are much more easily accessible than they once were, so even people without a background in genetics can teach others the importance of awareness!






Affordable, Accessible Genetic Screening in Illinois

Our affordable, accessible carrier screening program uses advanced technology to provide comprehensive screening for Jewish and interfaith couples. Visit our Get Screened page to learn more and register.