Deciphering molecular mechanisms of arginine deiminase-based therapy - Comparative response analysis in paired human primary and recurrent glioblastomas.

Arginine auxotrophy constitutes the Achilles' heel for several tumors, among them glioblastoma multiforme (GBM). Hence, arginine-depleting enzymes such as arginine deiminase (ADI) from Streptococcus pyogenes are promising for treatment of primary and maybe even refractory GBM. Based on our previous study in which ADI-susceptibility was shown on a panel of patient-derived GBM cell lines, we here aimed at deciphering underlying molecular mechanisms of ADI-mediated growth inhibition. We found that ADI (35 mU/mL) initially induces a cellular stress-response that is characterized by upregulation of genes primarily belonging to the heat-shock protein family. In addition to autophagocytosis, we show for the first time that senescence constitutes another cellular response mechanism upon ADI-treatment and that this bacterial enzyme is able to act as radiosensitizer (» cases). Long-term treatment schedules revealed no resistance development, with treated cells showing morphological signs of cell stress. Next, several combination strategies were employed to optimize ADI-based treatment. Simultaneous and sequential S. pyogenes ADI-based combinations included substances acting at different molecular pathways (curcumin, resveratrol, quinacrine, and sorafenib, 2 × 72 h treatment). Adding drugs to GBM cell lines (n = 4, including a matched pair of primary and recurrent GBM in one case) accelerated and potentiated ADI-mediated cytotoxicity. Autophagy was identified as the main cause of tumor growth inhibition. Of note, residual cells again showed classical signs of senescence in most combinations. Our results suggest an alternative treatment regimen for this fatal cancer type which circumvents many of the traditional barriers. Using the metabolic defect in GBM thus warrants further (pre-) clinical evaluation.

Variability in cytogenetic adaptive response of cultured human lymphocytes to mitomycin C, bleomycin, quinacrine dihydrochloride, Co60 gamma-rays and hyperthermia.

Adaptive response (AR) is a well-documented phenomenon by which cells or organisms exposed to low dose of a genotoxicant become less sensitive to subsequent high-dose exposure to the same or another genotoxicant. AR, if induced can modify the efficacy leading to drug or radio-resistance, during anti-neoplastic drug or radiation treatment. Contradictions exist in AR induction by different genotoxicants with respect to the biomarkers, time schedules, and inter-individual variability, reflecting the complexity of AR in eukaryotic cells. In order to further ascertain these factors, AR induced by anti-neoplastic agents mitomycin C (MMC), bleomycin (BLM) and chemosterilant quinacrine dihydrochloride was examined in different donors and time schedules using cytogenetic biomarkers chromosome aberrations, sister chromatid exchanges and micronuclei (MN). BLM- and hyperthermia (HT)-induced cross-resistance to gamma rays and MMC/BLM, respectively, was also studied. Difference between MMC- and BLM-induced protective effects in biomarkers examined in the same donors was noticed. Adaptation to BLM and HT showed cross-resistance to chromosome damage induction by gamma rays and BLM/MMC, respectively. Cell cycle analysis indicated that adaptation is not caused by change in the rate of cell proliferation after challenge dose. MN as a chromosomal biomarker in large-scale population studies on AR is advocated, based on similar AR induced in all donors by MMC/BLM and rapid assessment in binucleated cells. Influence of certain genotypes on chromosomal biomarkers used in AR studies and role of AR in radiation and chemotherapy need to be further deciphered.

A one-year neonatal mouse carcinogenesis study of quinacrine dihydrochloride.

Quinacrine is an acridine derivative under investigation for its use in nonsurgical female sterilization. Safety issues regarding the carcinogenic potential of quinacrine have been raised because it is mutagenic and clastogenic in vitro. The objective of the study was to evaluate the carcinogenic potential of quinacrine dihydrochloride (quinacrine) in neonatal mice treated with single intraperitoneal doses on postpartum days 8 and 15 and observed for 52 weeks. Neonatal Crl: CD-1 mice of each sex were randomly allocated into four treatment groups (0, 10, 50, and 150 mg/kg), dosed twice with quinacrine suspended in carboxymethylcellulose, observed for 52 weeks post dose, and then euthanized, necropsied, and subjected to a full histopathological examination. In male mice, tumor incidence was not significantly increased at any site at any dose level. In female mice, the incidence of benign uterine endometrial stromal polyps was slightly greater at the mid and high dose (> or = 50 mg/kg), as was the incidence of endometrial hyperplasia. The incidence of polyps in these groups was not significantly greater than in controls by pair-wise comparison but was significantly greater (p = .042) by the linear trend test. The authors conclude that quinacrine administered twice to neonatal mice may have enhanced or accelerated the development of endometrial hyperplasia and uterine stromal polyps at higher doses. Because uterine stromal polyps are a commonly observed benign tumor in older mice, the significance of this finding is unclear and will require a weight of evidence evaluation for a conclusion on the carcinogenic potential of quinacrine.