Dihydropyrimidine Dehydrogenase Is a Prognostic Marker for Mesenchymal Stem Cell-Mediated Cytosine Deaminase Gene and 5-Fluorocytosine Prodrug Therapy for the Treatment of Recurrent Gliomas

Abstract

We investigated a therapeutic strategy for recurrent malignant gliomas using mesenchymal stem cells (MSC), expressing cytosine deaminase (CD), and prodrug 5-Fluorocytosine (5-FC) as a more specific and less toxic option. MSCs are emerging as a novel cell therapeutic agent with a cancer-targeting property, and CD is considered a promising enzyme in cancer gene therapy which can convert non-toxic 5-FC to toxic 5-Fluorouracil (5-FU). Therefore, use of prodrug 5-FC can minimize normal cell toxicity. Analyses of microarrays revealed that targeting DNA damage and its repair is a selectable option for gliomas after the standard chemo/radio-therapy. 5-FU is the most frequently used anti-cancer drug, which induces DNA breaks. Because dihydropyrimidine dehydrogenase (DPD) was reported to be involved in 5-FU metabolism to block DNA damage, we compared the survival rate with 5-FU treatment and the level of DPD expression in 15 different glioma cell lines. DPD-deficient cells showed higher sensitivity to 5-FU, and the regulation of DPD level by either siRNA or overexpression was directly related to the 5-FU sensitivity. For MSC/CD with 5-FC therapy, DPD-deficient cells such as U87MG, GBM28, and GBM37 showed higher sensitivity compared to DPD-high U373 cells. Effective inhibition of tumor growth was also observed in an orthotopic mouse model using DPD- deficient U87MG, indicating that DPD gene expression is indeed closely related to the efficacy of MSC/CD-mediated 5-FC therapy. Our results suggested that DPD can be used as a biomarker for selecting glioma patients who may possibly benefit from this therapy.

Cytotoxic response of 5-fluorouracil-resistant cells to gene- and cell-directed enzyme/prodrug treatment

“…The orotate phosphoribosyl transferase (OPRT) expression level of HT-29/EGFP/FUR cells was decreased, which would correspond with decreased activation of 5-FU, thus initial conversion of 5-FU to 5-FUMP. It was shown on a model of glioblastoma cell lines [26] that dihydropyrimidine dehydrogenase (DPD) can be used as a biomarker for selecting glioma patients who may benefit from the CD-MSC/5-FC therapy. Considering the ability of DPD to deplete 5-FU, it is reasonable to expect that DPD-deficient tumors would be more sensitive to this treatment.…”

Non‐viral nucleic acid delivery to the central nervous system and brain tumors

“…Moreover, the 5‐FC/CD system also possesses a powerful bystander effect that diffuses 5‐FU into neighboring non‐transfected cells. In some recent studies, non‐viral vector‐encapsulated plasmid DNA encoding CD has shown effective antitumor efficacy with the addition of 5‐FC both in vitro and in vivo , greatly encouraging further investigation via clinical trials of the treatment of brain tumors using the CD/5‐FC suicide gene therapy system.…”

Clk1‐regulated aerobic glycolysis is involved in glioma chemoresistance

“…The growth rate has been previously shown to influence sensitivity of glioma cells to anti-cancer drug (Chung et al 2016). Thus, the cells' growth rate in Clk1 knockdown and control cells was measured by cell count (Fig.…”