Immunohistochemistry was performed on PDX tissues by subjecting 4-µm paraffin sections to a three-step process and a DAB staining kit (ZSGB-BIO). In brief, formalin-fixed, paraffin-embedded tissue sections were dried at 80 °C for 15 min and dewaxed in xylene, rinsed in graded ethanol, and rehydrated in double-distilled water. For antigen retrieval, slides were pretreated by steaming them in sodium citrate buffer (10 mM sodium citrate, pH 6.0) for 15 min at 100 °C. After the sections were washed with phosphate-buffered saline for 3 min, they were immunostained with primary antibodies against Ki-67, TGF-β and CD34 from ZSGB-BIO and incubated at 4 °C overnight. After 3 washes in PBS buffer, the tissues were covered by HRP-conjugated anti-mouse/rabbit antibodies for 30 min at room temperature (RT). Staining reactions were performed by covering the tissue samples with the prepared DAB chromogen solution and incubating them for approximately 10 min to allow proper brown color development 24 (link).