We know that lots of genes are involved in cancer progression. For example, you’ve probably read something like “scientists have found the gene for such-and-such cancer” or something similar. What does that really mean? Are there really genes which cause cancer? And why do we have those genes anyways, if that’s all they do?

Generally speaking, there are two broad classes of what we may call cancer genes. One is Tumor Suppressor Genes and the other are called Oncogenes (onco = tumor). It’s important to know that these are just labels scientist use to describe those genes, it doesn’t mean that those genes exist for the sole purpose of causing or preventing cancer.

They way these genes get those labels is by observing what happens when they are mutated (that is, a nucleotide change, most likely causing a decrease in activity). If more tumors result when a gene is mutated, it’s called a tumor suppressor gene, because we can say that when it’s active it “suppresses” tumors. A gene is called an oncogene if it promotes uncontrolled growth (i.e. like a tumor). So scientists have good reason to focused on these genes, because they know they have some role in tumor progression. The question is to understand what those genes are normally doing, and how, and what happens when they stop working.

Anticancer Genes in normal and tumor cells

But there is another class of genes that is also quite exciting: Anticancer genes. These are genes that function normally in their natural environment (i.e. in the cell types where they are usually expressed). However, when these genes are expressed in tumor cells, they cause cell death (see figure). This is called ectopic (i.e. not in your normal place) expression.

This is very exciting because only tumor cells die (anticancer), the normal surrounding tissue is unaffected. That means there is a potentially very specific way of targeting tumor cells for death, without harming normal tissue. If scientists could control the activity of those genes, it would be a very powerful tool against cancer.

Several of those genes are now in preclinical and/or clinical studies. But before the true therapeutic potential of each gene can be understood, they will need further study. For example:

• Does each anticancer gene only target a single type of tumor, or tumors only of a certain age?
• How specific are anticancer genes to killing only tumor cells? Will they kill normal cells at high doses?
• What are the target pathways that anticancer genes affect?

One of the most confusing observations is that in tumor cells, cell death is inhibited. That’s partly why they can continue to grow and grow, and why they’re so hard to kill. So how are molecular pathways leading to cell death different when anticancer genes are involved? What’s happening at the molecular level?

Clearly, there are lots of open questions and the coming years will provide some exciting results into anticancer gene activity and their therapeutic potential. Keep an eye out for this exciting line of research!

Image and Citation:

Grimm, S., & Noteborn, M. (2010). Anticancer genes: inducers of tumour-specific cell death signalling Trends in Molecular Medicine, 16 (2), 88-96 DOI: 10.1016/j.molmed.2009.12.002