Poster Presentation 35th Lorne Cancer Conference 2023

The Biology of Melanoma Metastases and Response to Therapy (#103)

Veronica Aedo-Lopez 1 2 , Reem Saleh 1 2 , Xin Du 1 2 , Dane Vassiliadis 1 2 , Mark A Dawson 1 2 , Riccardo Dolcetti 1 2 , Roberta Mazzieri 1 2 , Davide Moi 1 2 , Karen E Sheppard 1 2 , Grant A McArthur 1 2
  1. Peter MacCallum Cancer Centre, Melbourne, VICTORIA, Australia
  2. Medicine and Dentistry Health Sciences , University of Melbourne, Melbourne, VIC, Australia

Background: Melanoma is an aggressive disease with a high tendency of metastasis. Prognosis and response to therapy vary according to the site of metastases. Patients with liver and brain metastases have shorter survival while those with lung metastases have better outcomes1. Melanoma cells are highly plastic which allows them to quickly and dynamically switch between different phenotypes without gaining mutations. Single cell analysis has not only identified fluctuations in the molecular state of drug-naive melanoma cells that primes them to lead to resistance to targeted therapy2 but also that targeted therapy induces distinct gene expression phenotypes that survive therapy and ultimately lead to resistance3. This study aims to understand the impact of the metastatic site on melanoma cell transcriptional phenotypes, if particular transcriptional phenotypes survive therapy and if these surviving cells change in response to therapy.

Methods: Barcoded mouse BRAF mutant melanoma cell lines will be used to set up melanoma mouse models of solid tumour and experimental metastasis. For solid tumours, melanoma cells will be injected subcutaneously, and distant metastases will be induced by intravenous, intracardiac or intracranial injection. Growth of solid tumours will be monitored by digital calliper, and development of tumour metastases will be evaluated via the Lumina bioluminescence imaging system. Mice will be euthanised at pre-determined experimental endpoint and solid/metastatic tumours will be harvested for subsequent analyses.

Lineage tracing and clonal heterogeneity of transcriptional phenotypes will be evaluated using state of art SPLINTR (Single-cell Profiling and Lineage Tracing) technology4. This technology will be employed to analyse melanoma cells prior to implant and after harvest of different metastatic sites both before and after treatment (targeted therapy and/or immunotherapy).

Outcomes: This study will identify if the metastatic site selects for pre-existing transcriptional phenotypes; identify if pre-existing transcriptional phenotypes lead to resistance to therapy (BRAF/MEK targeted and/or Immune checkpoint therapy) and if they differ at the different metastatic sites; and identify transcriptional phenotypes that survive therapy and if they differ at the different organ sites. Overall, this information will provide new understanding of melanoma transcriptional phenotype behaviours and biological characteristics at different metastatic sites and in response to therapy.

  1. Conway J.W. et al. Unveiling the tumor immune microenvironment of organ-specific melanoma metastatic sites. Journal for Immunotherapy of Cancer 10e004884 (2020).
  2. Emert, B.L. et al. Variability within rare cell states enables multiple paths toward drug resistance. Nature biotechnology 39, 865 (2021).
  3. Rambow, F. et al. Toward Minimal Residual Disease-Directed Therapy in Melanoma. Cell 174, 843 (2018).
  4. Fennell, K.A. Non-genetic determinants of malignant clonal fitness at single-cell resolution. Nature 601, 125 (2022).