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Colorectal Cancer and Population Genetics Q&A

EDITORS’ NOTE: For Colorectal Cancer Awareness Month, Einstein’s director of multimedia communications, Sunita Reed, spoke with Srilakshmi Raj, Ph.D., assistant professor of genetics at Albert Einstein College of Medicine and a member of the NCI-designated Albert Einstein Cancer Center to discuss the study of population genetics and how it may improve colorectal cancer prevention and treatment in the Bronx and beyond.

What is the overall goal of your work here at Einstein?

The primary goal of my research is to study variation within and among human populations and understand how that genetic variation could contribute to differences in disease risk and outcome.

What led to your interest in population genetics?

I went to a large inner city public school for elementary school. My favorite day of school was International Day when all the children would come to school wearing all of their traditional clothes. It just struck me that there was so much diversity and so much pride in our diversity. And it made me proud to be different as well. That idea of being able to appreciate people for their similarities and differences, cultural and physical really stuck with me, and it got me interested in trying to understand the biology underlying variation among populations.

How does what you do apply to colorectal cancer?

With colorectal cancer, we understand that there are enormous population disparities in risk and outcome. My role will be to try and understand what is the genetic basis of some of the differences that we see in colorectal cancer risk among different populations that live here in the Bronx. For example, African Americans get diagnosed at younger ages and have more severe onset typically. There are also larger numbers of cases among them than in European Americans, for example. We also see higher rates of colorectal cancer in certain Latino communities. Over 90% of individuals who live in the Bronx are non-European white and so we really need to understand the genetic basis of the traits and the genetic bases of the public health conditions that we have here in the Bronx. Part of the reason that I joined Einstein and that I was recruited to Einstein is it has become very clear that we really need more representation so that other populations are reflected in global genomics studies.

Why is it important to study population genetics rather than characterize people by race?

One of the greatest challenges that we have in medicine today is that a lot of what we have experienced as medical professionals, or as researchers, is that when we ask people what their ethnicity is, it mostly involves checking off a box on a form: We are Black, we are Hispanic, we are Asian, we are white. But that really doesn’t carry any weight when it comes to genetics. If you check off Black, it could mean that you’re African American, many of whom have white European ancestry, or Black Brazilian, which may be a mix of local indigenous populations and African, and/or any number of different ethnicities or combination of genetic backgrounds where your skin is darker than white Europeans. Genetic sequence variation can help us understand genetic similarities and differences among different communities. This is immensely valuable in medicine, because then we can understand differences within and among different communities. By using genomics, we can better define what a population is, and their ancestral composition much more accurately than racial categorization.

What do we know in terms of colorectal cancer risk and genetics?

We have a good understanding of how colorectal cancer risk mutation profiles might look in a white European individual, for example, but we don’t understand how these risks mutation profiles look like in individuals of different ethnicities. And this is especially relevant to colorectal cancer, because individuals of African American ancestry have much higher risk of colorectal cancer. Not only do they have higher risk, but it’s also at a younger age also with a more severe outcome. Many times when we deal with genetic diversity, a treatment that will work for one individual will not work for somebody else. In order to be able to serve the needs of the whole community, we need to understand the biological mechanisms of disease in the entire community. It is my responsibility to try and close that gap and make sure that everybody’s represented when we do genetic studies on risk to colorectal cancer.

Besides genetics, what other factors play a role in colorectal cancer risk?

Genetics is just one of the factors involved in colorectal cancer risk. There are numerous other factors that in many cases are even more important. Risk factors such as diet, physical activity, age, smoking status, family history of colorectal cancer or inflammatory bowel disease. There are very important social considerations as well. Recent studies have linked colorectal cancer survival outcomes to low income areas, low education, insurance status and the type of treatment centers available to patients. Screening via colonoscopy is a major preventative measure. Many people don’t go for screening or feel discouraged from screening for colorectal cancer or other forms of cancer, particularly in low socioeconomic status households. There has to be a real societal shift to encourage to try and encourage cancer screening across the full socioeconomic spectrum and among all populations so that we can enable better health outcomes for everybody.

How will your research help people?

Right now, the vast majority of genetic studies have been carried out on individuals of white, northern European descent. So we have a very good understanding of the genetic risk factors, for example, to certain common diseases and we know there’s a high amount of environmental input, namely behaviors that increase risk for cancer, such as smoking and drinking alcohol. But we don’t understand how this works across the board across all populations. Is a particular disease occurring at the genetic level? Is it occurring at the level where environment feeds into disease risk when it interacts with the genetics? In order to understand all of these different strands of evidence and how it feeds into disease risk in different communities, we really need to understand first, the genetic variation among different communities and how this leads to similarities and differences in disease risk among populations.

What excites you about what you do?

What excites me is that we’re at a time now where we have the genetic resources to really understand similarities and differences among populations and the technologies to be able to do this at scale. As a population geneticist, I think there’s no better time to do this kind of research bringing together genetics, big data, electronic health record information and community engagement, so we can try and ramp up medical interest in and representation for all communities.

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The Doctor's Tablet Editors

The Doctor's Tablet Editors

The Doctor’s Tablet is co-edited by Gordon Earle and David Flores of Albert Einstein College of Medicine’s department of communications and public affairs.

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