Species-specific real-time RT-PCR analysis of expression of stromal cell genes in a tumor xenotransplantation model in mice.

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 real-time RT-PCR assays to quantitate expression of the indicated transcripts and described analytical performance of the assays.

Fibroblast activation protein alpha is expressed by transformed and stromal cells and is associated with mesenchymal features in glioblastoma.

Glioblastomas are deadly neoplasms resistant to current treatment modalities. Fibroblast activation protein (FAP) is a protease which is not expressed in most of the normal adult tissues but is characteristically present in the stroma of extracranial malignancies. FAP is considered a potential therapeutic target and is associated with a worse patient outcome in some cancers.

Dipeptidyl peptidase-IV inhibits glioma cell growth independent of its enzymatic activity.

Malignant gliomas exhibit abnormal expression of proteolytic enzymes that may participate in the uncontrolled cell proliferation and aberrant interactions with the brain extracellular matrix. The multifunctional membrane bound serine aminopeptidase dipeptidyl peptidase (DPP)-IV has been linked to the development and progression of several malignancies, possibly both through the enzymatic and nonenzymatic mechanisms. In this report we demonstrate the expression of DPP-IV and homologous proteases fibroblast activation protein, DPP8 and DPP9 in primary cell cultures derived from high-grade gliomas, and show that the DPP-IV-like enzymatic activity is negatively associated with their in vitro growth.

Expression of dipeptidyl peptidase-IV activity and/or structure homologs in human meningiomas.

Meningiomas are tumors derived from arachnoid cap cells that represent approximately 30% of all intracranial tumors. In this study, we investigated 22 human meningiomas for the expression of dipeptidyl peptidase (DPP)-IV activity and/or structure homologs (DASH), including canonical DPP-IV/CD26, fibroblast activation protein-alpha (FAPalpha), DPP8 and DPP9. DPP-IV-like enzymatic activity, including all enzymatically-active DASH molecules, was found in all 18 benign meningiomas WHO grade I and IV atypical meningiomas WHO grade II by continuous rate fluorimetric assay in tissue homogenates and catalytic enzyme histochemistry in situ.