DNA methylation estimates of immune cell abundance have prognostic potential in triple negative breast cancer.

Immune infiltration is now recognised as an important prognostic factor in triple negative breast cancer (TNBC). DNA methylation, due to its cell-type specificity, offers a promising approach for quantifying immune cell abundance as a biomarker for risk stratification. Here, we used EpiDISH, a DNA methylation-based cellular deconvolution method, to estimate immune cell proportions from genome-wide methylation data across four independent breast cancer datasets. We show that increased methylation-estimated immune cell percentage in TNBC patients is associated with improved outcomes. This highlights the potential of DNA methylation-based estimates of cell composition for prognosis in TNBC.