Human tumor xenografts in mice together with the species-specific analysis of expressed genes allow to study the molecular processes driving tumor growth and progression in vivo and help to develop and evaluate anticancer therapies. In the present work, we designed and validated species-specific real-time RT-PCR assays for discrimination and quantitation of expression of human and mouse transcripts in cancer and stromal cells including dipeptidyl peptidase (DPP) 4, DPP8, DPP9, fibroblast activation protein (FAP) and CXC chemokine receptor 4 in mixed human-mouse biological samples. Using single species RNA samples and mixed human-mouse RNA samples, we formulated and characterized two-step realtime RT-PCR assays to quantitate expression of the indicated transcripts and described analytical performance of the assays. We also demonstrated the applicability of these assays for species-specific quantitation of transcriptional expression of mouse stromal cell genes including Dpp4, DppS, Dpp9, Fap and Cxcr4 in mixed human-mouse RNA samples from human glioma cell-derived tumor xenografts growing in mouse brain. (C) 2017 Elsevier Inc. All rights reserved.