Efficacy of cytotoxic agents used in the treatment of testicular germ cell tumours under normoxic and hypoxic conditions in vitro

Abstract

Platinum-based chemotherapy is the main treatment element to achieve cure for patients with metastatic germ cell tumours. Drug resistance in testicular germ cell tumours (TGCTs) is rare and the reasons are not fully understood. While recent investigations have indicated decreased efficacy of chemotherapy in several tumour types under hypoxic conditions, this aspect has not been investigated in TGCTs so far. Furthermore, for cisplatin -the most active drug in this disease -controversial effects of hypoxia on cytotoxic efficacy have been reported. The relative efficacy of cytotoxic agents for the treatment of TGCT patients was studied in three different cell lines derived from human embryonal carcinomas (EC) in an in vitro hypoxia model. NT2, 2102 EP, and NCCIT were tested for their sensitivity towards cisplatin, etoposide, bleomycin, 4-OOH-ifosfamide, carboplatin, paclitaxel, gemcitabine, oxaliplatin, irinotecan, and mitomycin C under normoxic and hypoxic conditions using the MTT assay. Inhibitory concentrations IC 50 of the tested agents under both conditions were compared. Selected results were confirmed by flow-cytometric assessment of the apoptotic index. In all cells, doubling times were prolonged in hypoxia (NT2oNCCITo2102 EP). All drugs were less effective under hypoxic conditions, including mitomycin C (eg, 1.6-fold increase of IC 50 in hypoxia compared to normoxia for NT2) and cisplatin (eg, NT2: two-fold increase). The relative effect of hypoxia on the IC 50 depended mainly on the cell line, and to a lesser extent on the drug. The results indicate that the reduced cell proliferation in hypoxia might be an important factor, but not the only determinant of a reduced cytotoxicity. In view of the broad spectrum of drugs with different modes of action tested, the relative resistance cannot be mediated by substance-specific resistance mechanisms like hypoxia-induced upregulation of P-glycoprotein or increased DNA-repair capacity, since many unrelated drugs were affected to a comparable extent in their efficacy by hypoxia. This study also provides the rationale to test the hypothesis whether improving tumour oxygenation by raising haemoglobin concentrations, for example, with erythropoietin in patients with TGCTs receiving chemotherapy may improve the outcome.

Altered cellular redox homeostasis and redox responses under standard oxygen cell culture conditions versus physioxia

“…There is extensive literature on the effects of O 2 concentration on the efficacy of drug and radiation treatments in cancer cell killing, both in vivo and in vitro [4][5][6][7][8][9]. However, most studies have characterized these effects in vitro in cells that have been cultured, long-term, in a hyperoxic environment (i.e.…”

“…air) with subsequent short-term exposure to different O 2 concentrations during various treatments (drugs, photodynamic irradiation, hypoxia-reperfusion, etc.) [4,5,7,[9][10][11][12]. The consequences of long-term exposure to hyperoxic or physioxic environments on the subsequent cell killing effects of cancer treatments (e.g.…”

Genome-wide DNA methylation profiling reveals novel epigenetically regulated genes and non-coding RNAs in human testicular cancer

“…Ntera2 (NT2) is one of the established pluripotent human testicular embryonal carcinoma cell lines. This cell line has been extensively used in research on TGCT (Burger et al, 1998;Koch et al, 2003;Skotheim et al, 2005). In this study, we used NT2 as a cell model to study differential methylation in embryonal carcinoma.…”

Review: Implications of In Vitro Research on the Effect of Radiotherapy and Chemotherapy Under Hypoxic Conditions

“…The induction of chronic hypoxia is mostly performed under moderate hypoxic conditions [25,26]. Chronic anoxia has been investigated also [27,28], but Weinmann et al [29] observed a retardation of cell growth and induction of apoptosis under anoxic (Ͻ0.1% O 2 ) but not under hypoxic (1% O 2 ) conditions in the cell lines they examined.…”

“…Skvortsova et al [32] and Hay et al [33] evaluated cell viability using the sulforhodamine B assay. Another colorimetric procedure used to assess cell survival after exposure to hypoxia is the microtetrazolium assay [18,25,34]. Still other investigators use the trypan blue exclusion procedure to estimate the percentage of viable cells following hypoxia [21,35].…”