Figure 1.

Establishment of patient-derived xenograft (PDX) models from different molecular subtypes of breast cancer. (A) Scheme of breast cancer PDX establishment and drug treatment. Surgical or biopsy tumor samples from breast cancer patients were implanted into the mammary fat pads of immunodeficient mice. Following growth of the tumor in passage 1 (F1), tumor fragments were serially transferred from mouse to mouse. In drug-response tests, PDXs were treated orally or intraperitoneally with drug A, B, or their combination. Drug efficacy was assessed by monitoring tumor growth, validating histological features, and determining expression of target proteins. (B) PDX engraftment patterns according to breast cancer subtype. The number of PDX implantation trials and successes according to breast cancer subtype in samples obtained at the National Cancer Center, Korea, between July 2014 and September 2017. Success rates of PDX engraftment according to molecular subtype are shown in parentheses. The PDX engraftment rate for HR⁻/HER2⁺, HR⁺/HER2⁺ and TNBC subtypes was relatively high (~21%) compared with that of the HR⁺/HER2⁻ subtype. (C) Comparison of histological features between representative patients’ original tumors and the corresponding PDX tumors. Four representative patients’ xenograft tumors showing retention of the same morphological features (H&E staining) and ER, PR, HER2 and Ki-67 biomarker status as the original tumors. Patient samples are shown in the left column; corresponding xenograft results are depicted in the right column. Scale bar, 200 μm. (D) Overall survival (OS) and disease-free survival (DFS) of breast cancer patients according to PDX engraftment status. OS and DFS were analyzed using Kaplan–Meier plots and the log-rank test. Tumors from patients with poor OS (p = 0.087) and DFS (p = 0.056) showed a good engraftment tendency.