Fig. 3

Immunohistochemical analysis of breast cancer specific and immune cell markers in BC-PDMs. DAB staining was analyzed semi-quantitatively as %-area fraction of a BC-PDMs. RGB images were unmixed by subtractive mixing (color deconvolution) using ImageJ software. (A) Hormone receptor (HR) DAB staining of clinically classified HR+ BC-PDMs vs. TNBC BC-PDMs. Clinically assessed immunoreactive scores (IRS) from primary tumor are indicated. HR+ BC-PDMs were arranged in ascending order of ERα expression (B) HR+ BC-PDMs have increased HR expression (ERα, PgR, HER2) compared to TNBC BC-PDMs. (C) DAB staining of luminal cytokeratin (CK18) and basal cytokeratins (CK5 and CK6). BC-PDMs were grouped into four groups according to CK staining: CK5⁻CK18⁺, CK5⁺, CK5/6⁺ and CK5/6/18⁺. (D) Significantly elevated expression of luminal CK18 vs. basal CK5/CK6 in HR+ compared to TNBC BC-PDMs. Mann–Whitney U test, **p = 0.006. Differences in CK18, CK5 and CK6 expression in HR+ and TNBC BC-PDMs according to their classification into the previously determined groups. Within group: One-way ANOVA, Holm-Šídák’s multiple comparisons test. Different group comparison: Two-way ANOVA, Holm-Šídák’s multiple comparisons test. (E) Differences in CK and FAPα expression in ILC BC-PDMs vs. NST BC-PDMs. NST BC-PDMs show higher levels of CK18, while ILC BC-PDMs show significant higher levels of FAPα. Mann–Whitney U-test, *p = 0.028. Both ILC/NST BC-PDMs express basal CK5 and 6. (F) DAB staining of FAPα and immune markers in BC-PDMs grouped into HR+ and TNBC. For HR+ BC-PDMs, BC-PDMs were arranged in ascending order of FAPα expression. Data are mean with SEM. *p < 0.05, **p < 0.01, ***p < 0.001. ERα: estrogen receptor alpha; PgR: progesterone receptor; HER2: HER2/neu-ErbB2 receptor