MKI67 and breast cancer: Being a spliceosomal core Sm protein, SNRPD1 could nicely stratify breast cancer subtypes into TNBCs and non-TNBCs (Fig. 1a), showed comparable sensitivity and accuracy with the canonical proliferation marker KI67 in breast cancer subtyping (Fig. 2g), and exhibited similar correlations with KI67 (cor = 0.38, p = 9.2E−33) and the primary breast cancer subtyping marker ER (cor = − 0.39, p = 4.1E−36), suggesting the prognostic value of SNRPD1 on breast cancer subtyping and its relevance with cell proliferation.