Conversations with Dr. Parry Guilford: Discovering the CDH1 gene mutation

Conversations with Dr. Parry Guilford: Discovering the CDH1 gene mutation

We asked Dr. Parry Guilford what it was like finding the gene mutation that has affected so many families worldwide. What was that “Eureka moment” like?

Dr. Parry Guilford:

We were watching the sequence of CDH1 coming up on the DNA sequencing machine’s screen as it was being read real time, letter by letter. In this case, it was a fragment of the CDH1 gene belonging to members of a large New Zealand Māori family with generations of stomach cancer. Worst case scenario was that it would take us 20,000 years at our current rate to look at the whole genome and find the bloody thing. But the week before, we had run a different type of DNA test that told us something wasn’t right in this fragment of CDH1, a piece of DNA somewhere near the middle of the gene, a fragment that measured about one tenth of one millionth of the human genome.

CDH1 was a top candidate. There are 20,000 genes in the human genome, but this one, along with a handful of others, made really good sense (although it’s easy to tell yourself something makes good sense when the alternative is super tedious). So, we broke the CDH1 gene from people with stomach cancer into bite sized fragments and started to check each fragment one by one, looking for an error, a mistake, a mutation.

This fragment was 176 letters long (the whole genome has 3 billion letters). We were watching each letter appearing on the DNA sequencer’s screen, clicking down one by one, like something from the old Space Invaders video game. What we were looking at resembled a long, long bar code (176 bars long), with each bar being revealed at the top of the screen about every three seconds.

On the sequencer, beside the fragments from the stomach cancer families, was a fragment from someone else, someone who had no history of cancer. What we were hoping to see was those two barcodes diverge, one bar of the code from the cancer families to look wrong.

At 175 letters I gave up. I pushed back in my chair and said ‘nooo (words to that effect), it’s not there’. Then I heard my colleagues yell ‘No, look!’ And there it was, the barcode at position 176, exon 7, in the CDH1 gene, in the wrong place, all askew. We had it.

Moral of the story is: watch everything to the end, the real end.

Portrait of Karen Chelcun SchreiberI’m an optimistic realist. I love to laugh, often at myself. I am learning how to focus on Right Now! I have the most amazing family, friends and colleagues. The silver lining of HDGC has been the people I have come to know, to help, to work with, and to love, all throughout the world.

It always begins with a family.

It always begins with a family.

This is my little family, circa 1962. Dad was behind the camera. Looks like we may have been on our way to Aunt Margie’s house on Easter Sunday.

Who knew that four of us pictured here inherited a mutation in the CDH1 gene from Mom, putting all of us at high risk of developing diffuse gastric cancer?

No one knew. Literally, no one knew.

Mom was the first to die of gastric cancer in 1982 at age 52, which was 20 years after this photo was taken, and 15 years before the connection was made between this deadly cancer and the CDH1 gene.

Hereditary Diffuse Gastric Cancer syndrome (HDGC), often caused by a mutation in the CDH1 gene, was first identified by Professor Parry Guilford and his team of researchers in 1997.

Fast forward 25 years following my mother’s death. The bombshell diagnosis of my big brother Greg came in 2007. We lost him in 2009 at age 59.

Our knowledge of Parry’s discovery came to us by way of frantic research, and much too late to save Greg. But this life saving discovery in NZ changed the course for me and my little brother, our children and grandchildren, and generations to come.

The two of us went through the recommended treatment to eliminate our risk – prophylactic total gastrectomy (PTG) meaning preventive surgical removal of the entire stomach.

As for the next generations, three adult children underwent PTG. Three of the younger ones (teen to twenties) have yet to work through this. Next come the grandchildren – two so far . . .

The SOS Campaign is extremely important for HDGC families worldwide: to ensure funding for the promising HDGC research taking place in New Zealand, so those who carry a CDH1 mutation do not have to continue to sacrifice their stomachs to save their lives. This work has potential to prevent Lobular Breast Cancer as well, but considerably more effort will be needed in this area in the future.

But there are more very important messages to you stemming from my story.

It always begins with a family.

Hereditary cancer syndromes and other hereditary diseases always begin with a family, and often are discovered by several deaths. The variable is how many deaths in a family it takes to figure it all out.

A cancer or disease doesn’t have to be seen back many generations in your family medical history to be concerning. Mine was a history of one generation, one person. Until my brother Greg.

Your family medical ‘history’ is being written today. We didn’t have a history of lobular breast cancer in our family, until we did in 2015. We didn’t have a history of pancreatic cancer in our family, until we did in 2022.

Document your family medical history. It can be with an online tool, or a simple Excel spreadsheet. I use Excel and update it every time something new happens in my family and share it with all my family members.

Be proactive. Ask to review your family medical history with your primary care doctor at every annual exam. Share important diagnoses with your family members, so they can update their medical record too.

Pay attention because it always begins with a family.

Karen Chelcun Schreiber
One of Parry’s Angels

Portrait of Karen Chelcun SchreiberI’m an optimistic realist. I love to laugh, often at myself. I am learning how to focus on Right Now! I have the most amazing family, friends and colleagues. The silver lining of HDGC has been the people I have come to know, to help, to work with, and to love, all throughout the world.