Before we try to answer that, let’s talk about what cancer is.
Cancer is an umbrella term used to describe a few hundred diseases with the same pathological origin: the uncontrolled growth of cells.
We have a few trillion cells in the adult human body, each containing a complete copy of our DNA, the genetic blueprint for life. The DNA is housed within the nucleus, and controls and regulates the workings of the cell.
Sometimes, due to intrinsic (errors in DNA replication, spontaneous mutation) or extrinsic factors (cigarette smoke, alcohol, asbestos), the DNA gets corrupted through mutation. These corrupted pre-cancerous cells seek one goal: immortality.
The cells proliferate rapidly, ignoring all signals to slow down or stop dividing, forming an aggregate or mass of cells, sometimes closely resembling their tissue of origin. This localised mass of cells is called a benign (fancy word for harmless) tumour. Bear in mind, this localised group of cells is not considered cancer, yet.
At some point, greed overtakes this population of cells, and everything spirals out of control. These cells break free from their original tumour, seeking refuge elsewhere. Chaos ensues. The process of migration from the tissue of origin to another tissue is called metastasis, and the cancer is now called metastatic cancer. Meanwhile, the tumour is now called a malignant tumour. This is the truest form of cancer.
So, do plants get cancer?
The simpler answer would be to say no.
Plants do have tumours, however.
Agrobacterium tumefaciens is a rod-shaped, Gram-negative, soil dwelling bacteria that can infect about 140 species of eudicot plants including grape vines, rhubarb, horse radish, etc.
This bacteria has a plasmid (an extra chunk of circular DNA) called the “Tumour inducing plasmid” or Ti plasmid. This plasmid overrides the plant’s DNA by integrating itself into the plant’s genome, leading to the formation of a tumour. The disease is called “crown gall disease”, which has also been described as a plant cancer. It might cause stunting of growth in seedlings or young plants.
While A. tumefaciens and its effects are widely studied, there are other fungal and bacterial pathogens that cause plant tumours as well.
From a wider perspective, a crown gall tumour might be classified as cancer. Similar to liver, stomach and cervical cancer in humans, caused by pathogens that stimulate uncontrolled growth and division of host cells.
However, human cancers are different. One of the hallmark characteristics of human or animal cancers, lacking in plants is metastatic invasion by the tumour. The process of metastasis in animals is facilitated by the movement of cells using the bloodstream or the lymphatic system to get around. Since plant cells have a thick cell wall, they are usually held in place. Lack of movement implies that a plant tumour cannot metastasize.
So, plants don’t really get cancer the way humans or other animals do. However, there’s a striking resemblance between plant tumours and premalignant animal tumours. A study published in 2010 suggests plant and animal tumours may have overlapping mechanisms and pathways that contribute to tumour formation. Interesting!
Do you have a question about cancer? Leave it in the comments below!