Mechanisms by which whole genome doubling drives breast tumor evolution [scRNA-seq]

Here we developed an experimental model of WGD using murine mammary tumor cell lines in immunocompetent mice and found that WGD triggers immune evasion characterized by reduced infiltration of CD8+ T cells. Via comprehensive cellular and molecular characterization of WGD+ and WGD- tumors at the single cell level, we determined that WGD+ cancer cells have diminished antigen presentation due to muted response to IFN stimulation in part due to epigenetic silencing of transcriptional regulators of MHCI genes via the PRC2 complex.

WGD+ tumors also have lower alpha-ketoglutarate/succinate ratio that might lead to the observed increase in histone H3 lysine 27 trimethyl levels associated with repressive chromatin. Lastly, WGD+ tumors are more responsive to anti-PD-L1 blockade and to EED inhibitors and this is associated with increased antigen presentation and CD8+ T cell infiltration. Our results have important implications for the treatment of patients with WGD+ breast cancer.