Gamma‐linolenic acid alters Ku80, E2F1, and bax expression and induces micronucleus formation in C6 glioma cells in vitro

Abstract

SummaryGamma-linolenic acid (GLA) is an inhibitor of tumor cell proliferation in both in vitro and in vivo conditions. The aim of this study was to investigate the effects of 150 lM GLA on the expression of E2F1, cyclin D1, bax, bcl2, Ku70, and Ku80 in C6 rat glioma cells. The Ku proteins were chosen as previous studies have shown that loss or reduction in their expression causes increased DNA damage and micronucleus formation in the presence of radiation. The fact that GLA exposure is known to enhance the efficacy of radiation treatment raised the question whether the Ku proteins could be involved in this effect as seen for other molecules such as roscovitine and flavopiridol. GLA altered the mRNA expression of E2F1, cyclin D1, and bax, but no changes were found for bcl2, Ku70, and Ku80. Alterations in protein expression were observed for bax, Ku80, and E2F1. The 45% decrease in E2F1 expression was proportional to decreased cell proliferation (44%). Morphological analysis found a 25% decrease in mitotic activity in the GLA-treated cells, which was accompanied by a 49% decrease in S-phase by FACS analysis. A 39% increase in the number of micronuclei detected by Hoechst fluorescence points to GLA's effects on cell division even at concentrations that do not produce significant increases in apoptosis. Most important was the finding that Ku80 expression, a critical protein involved in DNA repair as a heterodimer with Ku70, was decreased by 71%. It is probable that reduced Ku80 is responsible for the increase in micronucleus formation in GLA-treated cells in a similar manner to that found in Ku80 null cells exposed to radiation. The decreased expression of Ku80 and E2F1 could make cells more susceptible to radiotherapy and chemotherapy.

Caffeine Inhibits Migration in Glioma Cells through the ROCK-FAK Pathway

“…Moreover, few micronuclei (MN) were observed after caffeine treatment (Fig. 3F), which is a consequence of the conversion of TOPOII/DNA complexes to permanent DNA damage [16]. …”

The novel ruthenium—γ‐linolenic complex [Ru2(aGLA)4Cl] inhibits C6 rat glioma cell proliferation and induces changes in mitochondrial membrane potential, increased reactive oxygen species generation and apoptosis in vitro

“…[20][21] GLA has recently been shown to cause DNA damage and micronucleus formation in the C6 rat glioma cell in vitro. 22 Transition metal based drugs such as cisplatin and carboplatin have been successful in the treatment of certain cancers, although they are cytotoxic to the host and drug resistance is commonplace. [23][24] Ruthenium containing compounds have also been shown to exhibit anti-tumour activity with lower cytotoxicity.…”

Lipids, Mitochondria and Cell Death: Implications in Neuro-oncology

“…In HT29 colon tumour cells, DHA reduced the ability of E2F1 to bind to DNA suggesting reduced activation of E2F1 by DHA and resulted in reduced S-phase [103]. The effects of GLA could only be partially reverted by the natural antioxidant alpha-tocopherol suggesting that ROS production is only partially responsible for GLA-induced changes in cell proliferation in the C6 glioma cell in vitro [102].…”

“…The in vitro studies found that, as expected, GLA caused a significant decrease in cell proliferation. From the experimental findings, it was apparent that the reduced proliferative rate was accompanied by a reduction in the expression of the protein E2F1, which is required for the entry of cells into the S-phase of the cell cycle and by a reduction in the number of cells in the S-phase when analysed by FACS [102]. In HT29 colon tumour cells, DHA reduced the ability of E2F1 to bind to DNA suggesting reduced activation of E2F1 by DHA and resulted in reduced S-phase [103].…”