Adverse condition transforms normal skins cells into melanoma
Karina Toledo/Agência FAPESP/DICYT Experiments conducted at the Federal University of São Paulo (Unifesp) have indicated that when normal skin cells are subjected to chronic stress, they undergo changes in the pattern of gene expression and ultimately transform into melanoma cells.
The mechanisms through which this modification occurs are being investigated in a research study supported by FAPESP and led by Miriam Galvonas Jasiulionis, professor in the Department of Pharmacology.
Some of the findings were presented October 16 in Germany during the panel on biotechnology at FAPESP Week Munich.
“It is a progressive transformation. First the melanocytes [cells that produce melanin] acquire altered characteristics, such as those found in pre-malignant lesions. Then they become non-metastatic melanoma cells, the type found in a less aggressive form of cancer. And finally, they become metastatic melanoma cells,” Jasiulionis explained.
According to the researcher, the initial alterations related to the transformation appear not to be genetic, but rather, epigenetic – a set of biochemical processes triggered by environmental stimuli that shape the genome function by activating or deactivating genes. Metaphorically speaking, the genome is the computer hardware while the epigenome is the software that makes the computer run.
“The most frequently studied epigenetic marks are DNA methylation [addition of methyl radicals to the molecule] and modifications of histones, which are important proteins in the compaction of this DNA. These two mechanisms are very important in regulating gene expression,” Jasiulionis explained.
The effects of stress
Data from the scientific literature shows that factors such as chronic inflammation, smoking, hormones and diet can modify the epigenetic pattern and, as a result, genome function over time. In the case of the Unifesp research study, the alterations were related to an increased production of oxygen free radicals caused by cellular stress.
“We subjected the cells to a sustained stressful condition and this increased the production of reactive oxygen species (ROS). In particular, our data indicate that there is a relationship between the increase of superoxide anion (O2.-) and changes in the pattern of DNA methylation,” Jasiulionis noted.
To induce cellular stress, the researchers coated the culture plates with a layer of algarose, a polysaccharide extracted from marine algae that prevents melanocytes from adhering to the plates.
“Normally, when we cultivate melanocytes in the laboratory, the cells secrete certain proteins to adhere to the plastic plates. When we prevent this process by using algarose, there is an increased production of reactive oxygen species,” the researcher said.
To demonstrate that there was in fact a causal relationship between oxidative stress, the epigenetic changes, and cancer, the researchers treated a portion of the cultures with a superoxide anion scavenger known as Mn(III)TBAP and observed that the process of transformation into melanoma was drastically reduced.
“After cellular stress was induced, we used cloning and then isolated some of the clones to determine whether or not they were tumors,” the researcher said.
In the cultures that were not treated with the scavenger superoxide anion, all the selected clones were malignant. But in the cells that received the Mn(III)TBAP, a very small number of clones formed and most of them died. Among the few that demonstrated viability for cultivation, an even smaller number proved to be tumorigenic.
“Most of the clones of the cells treated with the scavenger died. We believe this happened because the increase of reactive oxygen species is important in keeping the cells alive in a stressful condition,” Jasiulionis explained.
The results of the experiment were published in an article in the journal PLOS One.
The group is currently conducting similar experiments using human astrocytes – the cells found the central nervous system that when becoming malignant, give rise to a tumor known as glioblastoma. They also plan to study the transformation of keratinocytes, also found in the skin, into carcinoma.
“Our goal is to understand up to what point cellular stress is capable of contributing to the malignant transformation of several types of cells, besides the melanocytes. This understanding could help identify new therapeutic targets for fighting cancer in the future,” the researcher said.
According to Jasiulionis, the study could also provide relevant information about the relationship between conditions that result in an increased production of reactive oxygen species and the development of diseases such as cancer.
The role of reactive oxygen species in inducing cell death and the development of diseases was also the topic of the lecture by Marcus Conrad, researcher at the Helmholtz Zentrum München, in Germany.
The scientist presented a project entitled, ROScue Therapeutics, whose goal is to identify drugs capable of preventing cell death and, consequently, the failure of related organs.
The next speaker was Prof. Raghuvir Krishnaswamy Arni from São Paulo State University (Unesp) in Ribeirão Preto, who talked about the activities of the Multiuser Center for Biomolecular Innovation (CMIB), established with FAPESP funding.
With the help of structural and molecular biology techniques, the group headed up by Arni has dedicated itself to the study of proteins secreted by bacteria and viruses in order to discover ways to inhibit pathogenic action and steer the drug development process. The center is also studying proteins found in the toxins of animals such snakes, spiders, and worms.
Arni also referred to the collaboration he already enjoys with German centers such as the University of Hamburg, the German Electron Synchrotron (DESY) and Heinrich Heine University Düsseldorf (HHU).
The final speaker on the bioetechnology panel was Christiane Geiger, researcher at Trianta Immunotherapies GmbH, a spin-off of Helmholtz Zentrum München. She has been working to develop vaccines capable of strengthening immunity to cancer.