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. 2020 Oct 6;11(10):831. doi: 10.1038/s41419-020-03037-0

Fig. 1. PI3Kα-inhibitory chemotherapy induced an acquired CD44high state and adaptive resistance.

Fig. 1

a Scheme of the in vivo experiment. Schematics of the generation of PI3Kα inhibitor-resistant cells using MMTV-PyMT mouse tumors are shown. Mice were treated daily with BYL719 (25 mg/kg) by oral gavage for 21 days. EpCAM+/CD45− cancer cells were sorted from primary MMTV-PyMT tumors or BYL719-resistant tumors and separately orthotopically injected into SCID mice. Tumors were resected and harvested to generate single cells. b Tumorigenicity of FACS-sorted BYL719-sensitive or BYL719-resistant cancer cells from MMTV-PyMT tumors following orthotopic injection into SCID mice (n ≥ 5/group). Tumor growth was monitored and recorded. Data are represented as the mean (±SD). (statistical analysis: T-test, *P < 0.05 vs. control). c Proliferation (3 days) of two cell lines sensitive to BYL719 in comparison with their resistant counterparts upon treatment with BYL719 at increasing doses. Each value is the mean (±SD), n = 5. (statistical analysis: T-test, *P < 0.05 vs. control). d Western blot analysis of PI3K/AKT pathway signaling using cell lysates from BYL719-sensitive and BYL719-resistant MCF7 cells and the molecular phenotype as indicated. Levels of the transcription factor Sox-2 and control laminin in cell nuclear extract were determined. e Densitometry analysis was performed comparing BYL719-sensitive and BYL719-resistant MCF7 cells based on three biological repeats (statistical analysis: T-test, *P < 0.05, **P < 0.01 vs. BYL719-sensitive cells, #P > 0.05, not significant). Each value is the mean (±SD) from triplicate samples. f The CD44 expression patterns of PI3Kα-resistant luminal breast cancer cells (MCF7 and T47D) were determined by RT-PCR. Results are expressed as mean ± S.D., n = 3. *P < 0.05, **P < 0.01, #P > 0.05, not significant. g Adaptive CD44 alternative splicing upon BYL719 (a p110α inhibitor) treatment or combined treatment with BYL719 and Azd6482 (a p110β inhibitor) in BYL719-resistant cells (MCF7R and T47DR) was assessed by Western blot analysis. Results are expressed as mean ± S.D., n = 3. *P < 0.05 when compared with naive MCF7 cells. #P < 0.05 when compared with BYL719-resistant cells without Azd6482 treatment.