Project Title: iPSC derived melanocytes as in vitro melanoma models
PhD Award Expected: Summer/Autumn 2020
Hi everyone! I am Marina Juraleviciute and I was born and raised in a wonderful city of Vilnius. My interest in natural sciences arose in the high school and after finishing it I entered bachelor studies of Modern Technologies Physics at Vilnius University. As my enthusiasm only grew I finished my master’s in Biophysics at the same alma mater. During the study years I participated in Erasmus student exchange program and went for one semester to study to Ljubljana (Slovenia). I took the chance and participated at Erasmus+ graduate programme. It was a six months placement at The Norwegian Radium Hospital, Institute for Cancer Research. Those were an extremely beneficial and inspiring experiences. Quite recently I became a part of MELGEN network which I am very excited about.
Science is fun and interesting, but there are other things that I enjoy as well. Whenever it is possible I travel and explore new destinations. I am passionate about the photography so these two activities often complement each other. I like reading, there is no particular literature genre I prefer, but I’m hung up on Haruki Murakami’s novels now.
Melanoma is the most aggressive form of skin cancer that arises from dark pigmented cells called melanocytes. Mutation of the BRAF gene is the most common mutation detected in as many as 50% melanomas. Up to 10% of melanoma cases are of familial origin (arise in melanoma-prone families) where alterations in CDKN2A and CDK4 genes account for about 25% of melanomas occurring in such families. However, current knowledge only allows us to explain less than 30% of the genetic susceptibility in melanoma-prone families, which suggests that other genetic and environmental factors might be contributing to the remaining risk. Recent studies have identified new melanoma susceptibility genes by comparing genetic mutations between healthy individuals and melanoma patients. Molecular mechanisms by which these genes alone or together with others influence melanoma susceptibility are still poorly understood. Therefore, my project aimed to investigate how these newly identified susceptibility genes and environmental factors (e.g., UV) are involved in melanoma initiation.
To implement the project, we applied a novel model based on innovative and powerful cell reprogramming technology. Melanoma patients carrying genetic mutations predisposing them to melanoma donated skin biopsies, from which we extracted fibroblasts. We reprogrammed these into stem cells (induced pluripotent stem cells – iPSC) and subsequently differentiated these into melanocytes. Since iPSC can be cultivated for an infinite time, this approach allows us to obtain an unlimited supply of melanocytes predisposed to melanoma for further extensive studies (Figure 1).
First, we investigated and confirmed that iPSC-derived melanocytes in laboratory settings retain patients’ traits. A cohort of melanocytes was exposed to ultraviolet radiation, a known environmental risk factor for melanoma, and sensitivity was evaluated. We observed a good correlation between melanocyte sensitivity to UV and patients’ pigment factors. Pigmentation factors were calculated by evaluating and scoring a number of self-reported parameters: skin reaction to intense sun exposure, usual skin reaction to sunlight, hair and eye color, the total number of nevi on the body, skin type. Into account was also taken the status of the MC1R gene, which regulates pigmentation pathway. Mutations in this gene are associated with red hair and fair skin and increase UV sensitivity. Furthermore, by investigating UV sensitive and resistant melanocytes, we observed apparent differences in accumulation and repair of UV caused DNA damage. We demonstrated that this model is a novel tool to investigate melanoma initiation as it is more accurate than existing models since it takes into account individual variability in genes.
Next, we focused on one specific risk gene, namely MX2. Previous studies have reported that it is associated with reduced risk to develop melanoma; however, its function in tumorigenesis was utterly unclear. We discovered that the presence of MX2 protein in primary melanoma tumors is associated with better patient survival and that it is often absent in metastatic tumors. To determine the function of the MX2 gene (Figure 2), we engineered melanoma cell lines that contained a high level of MX2 protein and compared their behavior to the corresponding cell lines that had low levels of MX2 protein. Interestingly, cells with a high amount of MX2 protein proliferated much slower than control cells. We injected these melanoma cells into mice to investigate if the MX2 gene is associated with tumor formation. Fifty days after injection, mice that received cells with a low amount of MX2 protein had much bigger tumors compared to the ones that were injected with cells containing high levels of MX2 protein. In this study, we were the first to provide evidence of the MX2 gene function in melanoma by demonstrating that the MX2 gene slows down the growth of cancer cells and has tumor-suppressive properties. These studies improve our understanding of how particular genes and mutations contribute to or prevent melanoma development and might aid in discovering novel therapeutic approaches.
Juraleviciute M, Pozniak J, Nsengimana J, Harland M, Randerson-Moor J, Wernhoff P, Bassarova A, Øy G.F, Trøen G, Flørenes VA, Bishop DT, Herlyn M, Newton-Bishop J, Slipicevic A. MX 2 is a novel regulator of cell cycle in melanoma cells. Pigment Cell Melanoma Res. 2019; 00: 1– 12. Available at: https://onlinelibrary.wiley.com/doi/full/10.1111/pcmr.12837