Periodic Reporting for period 1 - INHuMAN (Intra-tumoral heterogeneity in NRAS-driven metastatic melanoma)
Berichtszeitraum: 2019-04-01 bis 2021-03-31
In this call we have characterized this cellular plasticity and based on this data we have initiated projects to better characterize when and how cells transit, in order to block this phenotypic switch. The outcome of this fundamental action can be subjected to translational research that potentially can lead to the development of treatment strategies (personalized or not) to eradicate this devastating disease and improve patient’s survival.
In the objective 1 we were able to demonstrated that the transcriptomic landscape of both mouse and human melanoma is richer than previously reported and it can be fully recapitulated in lesions arising in NRAS-mutant mice. Cross-species analyses identified novel and evolutionarily conserved melanoma states, including a highly de-differentiated melanoma stem cell-like state (MSCs) raising the possibility that this population may be sitting at the top of a cellular hierarchy established in these melanoma lesions. Interestingly, another state of interest conserved in human and mouse tumors exhibited mesenchymal-like (EMT) features. Unsupervised in silico analyses predicted the Prrx1 Transcription Factor (TF) as a putative driver of this state.
In turn, the objective 2 was focused on the clinical characterization of the two particular cell states that we identified in our single cell RNA sequencing experiments. The clinical relevance was validated at single cell resolution using scRNA in human biopsies and by multiple imaging approaches in Patient Derived Xenografts and human melanoma biopsies. The spatial location was also assessed where it was found that melanoma stem cells are localized in close proximity to blood vessels while the Metastatic Initiating Cells in the invasive front of primary tumors.
In the third objective first we characterized the MSC population demonstrating that growth of melanoma is hierarchically organized suggesting that these cells are sitting at the apex of this hierarchy. These cells are located in perivascular niches and are able to acquire stemness features fueling growth. In the second WP we characterized the functional relevance and contribution of Metastatic Initiating Cells driven by the transcription factor PRRX1. By performing in vitro and in vivo assays provide direct evidence that Prrx1 marks a population of cells at the origin of metastases.
The outcome of this action is currently under consideration for future publication (Karras et al., under revision, Nature). During this call, I have been able to co author in projects related to melanoma heterogeneity and metastasis that are still ongoing or have been published. Internal biweekly meetings and meetings with collaborators were taking place frequently to discuss the existing progress of the project or future steps. I have been able to attend conferences/meetings and disseminate my work by giving oral talks or poster presentations. Any potential intellectual property that will arise from this action will be determined by Technology Transfer Office of VIB.
The study is ongoing where our main focus is on the better characterization of the niches that the cells reside. A series of experimental strategies has been designed by introducing new models and approaches. Part of this strategies is to better characterize the interplay of different melanoma cell states with the microenvironment.
The outcome of this action revealed that the cellular plasticity of melanoma tumors can have major socio-economic impact. Efforts to block phenotypic transitions by developing transcriptional and epigenetic approaches (e.g. chromatin remodeling inhibitors) is likely to be a particularly beneficial therapeutic approach to limiting plasticity and eventually the growth and metastasis of cells. Our data provide the first exhaustive overview of melanoma heterogeneity providing a platform for identification of druggable targets for more effective therapeutic approaches that intercept the disease before its lethal spreading to vital organs. Importantly, converging lines of evidence from our experimental mouse studies and clinical samples can unravel vulnerabilities of the Melanoma Stem Cells and the Metastatic Initiating Cells that can lead to effective target and eradication.