A picture of malignant melanocytes

Melanoma cells can invade surrounding tissue

As we said in a press release last night, our scientists at the Beatson Institute in Scotland have made an interesting discovery about how skin develops – a discovery that also helps us understand melanoma a bit better too.

The researchers were looking at how immature skin pigment cells, called melanoblasts, move around and find their correct location in the developing skin in mice, before maturing into melanocytes – pigment cells that can develop into melanoma when damaged (for example by UV light).

Melanoblasts, scientists had previosuly discovered, move around by extending long ‘legs’ into the surrounding tissue and literally hauling themselves into the correct position.

The Glasgow team, led by Professor Laura Machesky, found that a gene known as Rac1 was a key player in this process. They also discovered that interfering with Rac1 stopped the melanoblasts from moving around, and prevented mice’s skin from becoming properly pigmented. They’ve published their findings in the journal Developmental Cell.

But how is this relevant to cancer? We’ve tried to sum things up in a handy graphic, which you can see below:

Diagram showing how Rac1 is involved in the spread of melanoblasts

Click to enlarge

Although every cell in our body contains the full complement of 30,000 genes, only a subset are switched on in a given cell at a given point in its life-cycle. Consequently, Rac1 is only switched on at certain times – in this case during melanoblasts’ development.

But cancer cells, with their highly disordered and damaged DNA, seem to switch many of these developmental genes back on. In fact, cancer cells seem to regress back to their ‘childhood’ and start misbehaving.

And there’s a fair amount of evidence that Rac1 is indeed switched on in melanoma cells.

Given that researchers now know that Rac1 is a key player in how early pigment cells move around in the developing skin in mice, this suggests that the gene could be doing a similar job in melanoma cells in humans. More work is needed to find out if this holds true, but if it does then interfering with Rac1 – or other proteins it works with – in cancer cells could be a way to stop melanoma spreading (provided, of course, that this doesn’t interfere with the body’s day-to-day functioning).

It’s a small step, but science is a series of small steps that often take us in surprising new directions. We’ll be following the Beatson team’s future work with interest.


Image via Wikimedia Commons


  • Li et al: Rac1 drives melanoblast organization during mouse development by orchestrating pseudopod-driven motility and cell cycle progression. Developmental Cell (2011)