Arginine Deprivation Therapy: Putative Strategy to Eradicate Glioblastoma Cells by Radiosensitization

Abstract

Tumor cells-even if nonauxotrophic-are often highly sensitive to arginine deficiency. We hypothesized that arginine deprivation therapy (ADT) if combined with irradiation could be a new treatment strategy for glioblastoma (GBM) patients because systemic ADT is independent of local penetration and diffusion limitations. A proof-of-principle study was performed with ADT being mimicked by application of recombinant human arginase or arginine-free diets. ADT inhibited two-dimensional (2-D) growth and cell-cycle progression, and reduced growth recovery after completion of treatment in four different GBM cell line models. Cells were less susceptible to ADT alone in the presence of citrulline and in a three-dimensional (3-D) environment. Migration and 3-D invasion were not unfavorably affected. However, ADT caused a significant radiosensitization that was more pronounced in a GBM cell model with p53 loss of function as compared with its p53-wildtype counterpart. The synergistic effect was independent of basic and induced argininosuccinate synthase or argininosuccinate lyase protein expression and not abrogated by the presence of citrulline. The radiosensitizing potential was maintained or even more distinguishable in a 3-D environment as verified in p53-knockdown and p53-wildtype U87-MG cells via a 60-day spheroid control probability assay. Although the underlying mechanism is still ambiguous, the observation of ADT-induced radiosensitization is of great clinical interest, in particular for patients with GBM showing high radioresistance and/or p53 loss of function.

Mutant IDH1 Differently Affects Redox State and Metabolism in Glial Cells of Normal and Tumor Origin

“…There was no difference in proliferation of U87-MG-IDH1 R132H compared to IDH1 wt cells in 2-D culture growth; however, the colony forming capacity was also increased in the U87-MG-IDH1 R132H compared to the empty-vector control (10.8% ± 0.6 vs. 8.0% ± 0.1; p < 0.05 using t-Test) (Figure 2c). U87-MG cells are known to also grow in 3-D culture [23]. We therefore included a 3-D assay to verify the biological relevance of the IDH-mutation in this cell line, which appeared unaffected in the 2-D growth setting.…”

“…The cultured cells were lysed in RIPA Buffer (Sigma Aldrich, St. Louis, MO, USA) containing a protease inhibitor cocktail (Roche, Basel, Switzerland) according to the manufacturer's protocol. The extracted proteins were quantified with a Pierce™ BCA Protein Assay Kit (Pierce Biotechnology, Rockford, IL, USA) and resolved on 4-12% Bis-Tris gels (15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30) µg Protein per lane) at 100 V for 30 min. The bands were electrically transferred onto Hybond ECL Membranes (GE Healthcare, Chalfont St Giles, UK) at 30 V for one hour.…”

Combinatory Treatment of Canavanine and Arginine Deprivation Efficiently Targets Human Glioblastoma Cells via Pleiotropic Mechanisms

“…It has been described in a number reports that numerous cancers are defective in arginine biosynthesis, and some of them become hypersensitive to the deprivation of this amino acid [ 1 ]. Arginine is a semi-essential amino acid in humans, and its exogenous requirement is dependent on the stage of the organism’s development and its health status [ 2 , 3 ].…”

“…Arginine is a semi-essential amino acid in humans, and its exogenous requirement is dependent on the stage of the organism’s development and its health status [ 2 , 3 ]. Arginine plays an important role in various molecular pathways regulating cell division, wound healing, neurological and immune functions, and hormone synthesis [ 1 , 4 , 5 ]. It is also a key precursor in the synthesis of cancer-associated compounds such as nitric oxide (NO) and polyamines [ 3 , 6 , 7 ].…”

Refining Radiation for the Next Century

“…A proof-of-principle in vitro arginine deprivation therapy study was performed using recombinant human arginase or arginine-free diets. Significant IR sensitization was detected and it was more pronounced in 2D and 3D glioblastoma cell models with cells lacking functional p53 compared with their p53-wild-type counterparts (7). Further work will be needed to define the underlying mechanism responsible for this sensitization and whether or not it can be seen in preclinical mouse models.…”