Scientists Say Glyphosate DNA Damage May Cause Cancer

Scientists investigating the impact of pesticides on the DNA in lymphocytes (a type of white blood cell) found that glyphosate may cause a type of DNA damage that can lead to cancer. The finding is particularly important in that glyphosate has been linked in several studies to non-Hodgkin lymphoma, a type of cancer that affects lymphocytes.

Glyphosate DNA Damage and Double Strand Breaks

The researchers tested eight pesticides and found that glyphosate was among four chemical compounds that “showed a significant effect” on the number of lymphocyte cells with a type of DNA damage known as a double strand break (DSB). Double strand breaks can lead to alterations in chromosomes that are characteristic of non-Hodgkin lymphoma.

What is a double strand break? Let’s start with the word “strand.” You’ve probably seen diagrams of the structure of DNA, the complex molecule found in all cells that many have compared to an instruction book for building and operating each person’s body. Genes and chromosomes – the “paragraphs” and “chapters” in the genetic “how to” book – are made of DNA. Models of DNA usually show two chains twisted around each other with stair steps joining them like a spiral staircase. Those chains are the “strands” that are severed in a double strand break.

As you might imagine, when those strands break, it may result in the “stairs” falling apart too. That is a problem because those stairs are made up of four molecules that serve as the “letters” – adenine (A), cytosine (C), guanine (G) and thymine (T) – that spell out the genetic instructions telling the body what to do and how to do it. Those chemical letters, known as bases, are the basic building blocks of DNA.

In a double strand break, a significant number of those letters, along with the part of the strand holding them in place, can get separated from the “staircase.” The DNA breaks down. Making matters worse, the main mechanism that the cell uses to repair DSBs, a series of chemical reactions called non-homologous end joining (NHEJ), can’t fully repair the damage.

The NHEJ mechanism, as the authors of this study mention, is “known to be prone to error.”

“Uncontrolled cell proliferation* is a hallmark of cancer…. multiple mutations that accumulate in somatic cells over many years eventually remove an elaborate set of controls that would otherwise prevent cancer cells from dividing unchecked.” [* Proliferation is the process of cell growth and division.] — Katherine Hyland, Professor of Biochemistry & Biophysics, University of California San Francisco Institute for Human Genetics

Finding Double Strand Breaks in DNA After Herbicide Exposure

Evidence of glyphosate DNA damage comes in the form of proteins that are involved in the NHEJ repair process. The proteins are the “tools” left at the DNA repair worksite that provide evidence that a double strand break has occurred.

In this study, the researchers were looking for two key proteins. One is named gamma-H2AX. The location of gamma-H2AX at the NHEJ repair site is called a gamma-H2AX focus (plural foci). Another protein involved in the DNA repair process is called p-Ku80. Both proteins are considered “biomarkers” (biological evidence) for double strand breaks.