Figure 3. Active TGF-β Signaling in Basal Tumor Cells Increases Their Protection against Cisplatin-Induced Apoptosis.

(A) Experimental scheme to derive isogenic HRas^G12V-expressing YFP^negTβRII⁺ and YFP⁺TβRII^neg MKs from 1⁰ cultures. (Right) Epifluorescence of cultures ± TGF-β1. Note that only YFP^negTβRII⁺ cells are TGF-β reporter⁺ (mCherry⁺).

(B) Growth curves of TβRII⁺ and TβRII^neg cells ± 100pM TGF-β1. Data are mean ± SEM.

(C) Immunofluorescence of BSA- or TGF-β1-pretreated (36 hr) YFP^negTβRII⁺ and YFP⁺TβRII^neg MKs treated 10 hr with cisplatin. Note that YFP⁺TβRII^neg MKs frequently displayed signs of apoptotic rounding.

(D) γ-H2AX detection of DNA double-strand breaks induced by cisplatin treatment. Note that both YFP^negTβRII⁺ and YFP⁺TβRII^neg MKs show γ-H2AX signal in control, but TGF-β1 selectively spares TβRII⁺ cells, which remain spread.

(E) Quantifications of AcCasp3⁺ cells in the same experiment as in (C) and (D) (n=15 microscopic image fields). Data are box-and-whisker plots.

(F) Immunodetection of adduct formed between cisplatin and DNA. Note that YFP⁺TβRII^neg cells have more cisplatin-modified DNA (red). Anti-tubulin (white). Scale bars, 50 µm.