Is It a Mole or a Tumor?
Written by Vicky Diep
Edited by Audrey Bantug
Jan 18, 2021
Edited by Audrey Bantug
Jan 18, 2021
ABCDE - these comprise not just the first five letters of the alphabet, but also a rule of thumb for identifying whether a mole might be cancerous or not. A stands for asymmetry; B stands for border; C stands for color; D stands for diameter; and E stands for evolving. That is to say, moles that appear uneven (asymmetrical as opposed to a symmetric circle or oval shape), have raised edges or multiple colors, are larger than a pencil eraser, and seem to be “evolving” (changing in shape, color, or suddenly bleeding or feeling itchy) are red flags for skin cancer. How is it that some moles are just normal, benign markings on our skin while others can actually be dangerous tumors? What is the biology that underlies these differences?
To answer this question, we must first understand a few key details about cancer cells, such as what they are and what creates them. Cancer cells start off as normal cells in the body, which follow the regulations of the cell cycle to divide. They become cancerous when something (such as exposure to UV radiation or carcinogenic chemicals) induces a mutation in their genes that allow them to escape from the regulations of the cell cycle and divide nonstop. Such a mutation changes a normal gene into an oncogene. Genes that have the potential to transform into oncogenes are called “protooncogenes”.
The BRAF gene is associated with the formation of moles and is known to be a protooncogene that contributes to skin cancer. In order to elucidate the mechanism by which cell division stops in a growing mole before it becomes a tumor, researchers at the University of California, Irvine have been comparing cancer and normal mole growth in mice with BRAF mutations. They believed that rapid cell division in moles and tumors creates stress in the body, which activates a process called oncogene-induced-senescence (OIS). OIS induces those rapidly dividing cells to express genes associated with aging (senescence) so that they can no longer divide, putting an end to cell division in moles before they spiral out of control and become tumors.
By sequencing the RNA in mole cells and normal skin cells, the researchers found that, contrary to the OIS hypothesis, mole cells did not exhibit any significant differences in gene expression that would indicate that they were senescent. This led the researchers to hypothesize that instead of becoming senescent and becoming shut off by stress, moles know when to stop dividing when they reach a certain size by communicating with each other, like normal cells in growing tissues do. With this new insight into skin cell growth, the researchers believe that “further research … with the aim of better understanding what goes wrong to cause skin cancer” (ScienceDaily) will pave the way for the development of melanoma treatments in the future.
Works Cited
eLife. "New insight on mole growth could aid development of skin cancer treatments: A study detailing the processes that control mole size may help scientists find new ways to prevent skin cancer from growing." ScienceDaily. ScienceDaily, 13 October 2020. <www.sciencedaily.com/releases/2020/10/201013124200.htm>.
Image Source: "Superficial spreading melanoma in situ on dermoscopy, reflectance confocal microscopy and histopathology" by Juliana Casagrande Tavoloni Braga, Mariana Petaccia Macedo, Clovis Pinto, João Duprat, Maria Dirlei Begnami, Giovanni Pellacani, and Gisele Gargantini Rezze licensed under CC BY 3.0