Histone deacetylase inhibitor, 2-propylpentanoic acid, increases the chemosensitivity and radiosensitivity of human glioma cell lines in vitro.

Background: Treatment for malignant glioma generally consists of cytoreductive surgery followed by radiotherapy and chemotherapy. In this study, we intended to investigate the effects of 2-propylpentanoic acid (VPA), a histone deacetylase inhibitor, on chemosensitivity and radiosensitivity in human glioma cell lines.

Methods: Human glioma cell lines, T98-G, and SF295, were treated with temozolomide (TMZ) or irradiation (IR), with or without VPA (1.0 mmol/L). Then, cytotoxicity and clonogenic survival assay was performed. Cell cycle stage, apoptosis, and autophagy were also detected using flow cytometry and dansyl monocadaverin (MDC) incorporation assay. One-way analysis of variance (ANOVA) and t-test were used to analyze the differences among variant groups.

Results: Mild cytotoxicity of VPA was revealed in both cell lines, T98-G and SF295, with the 50% inhibiting concentration (IC50) value of (3.85 ± 0.58) mmol/L and (2.15 ± 0.38) mmol/L, respectively; while the IC50 value of TMZ was (0.20 ± 0.09) mmol/L for T98-G and (0.08 ± 0.02) mmol/L for SF295. Moreover, if combined with VPA (1.0 mmol/L) for 96 hours, the sensitivity of glioma cells to TMZ was significant increased (P < 0.05). The surviving fractions at 2 Gy (SF2) of T98-G and SF295 cells exposed to IR alone were 0.52 and 0.58. However, when VPA was combined with IR, the SF2 of T98-G and SF295 dropped to 0.39 (P = 0.047) and 0.49 (P = 0.049), respectively. Treatment with VPA plus TMZ or IR also resulted in a significant decrease in the proportion of cells in the G2 phase and increased apoptotic rates as well as autophagy in T98-G and SF295 cell lines (P < 0.01).

Conclusion: VPA may enhance the activities of TMZ and IR on glioma cells possibly through cell cycle block and promote autophagy, and thus could be a potential sensitizer of glioma treatment.