Haemanthamine alters sodium butyrate-induced histone acetylation, p21WAF1/Cip1 expression, Chk1 and Chk2 activation and leads to increased growth inhibition and death in A2780 ovarian cancer cells

BACKGROUND

Haemanthamine (HA) and sodium butyrate (NaB) are promising candidates for chemotherapy as a treatment for cancer.

PURPOSE

We aimed to determine the anticancer potential of HA and NaB, alone and in combination, in A2780 ovarian cancer cells and concurrently investigated anticancer potential in contrast to non-cancer human MRC-5 fibroblasts.

METHODS

Antiproliferative effects were determined by WST-1 assay and by Trypan blue exclusion staining. Cell cycle distributions were studied by flow cytometry and protein levels were determined by Western blotting.

RESULTS

The combination of HA and NaB caused a significant decrease in the proliferation of A2780 cells compared to the stand-alone treatment of cells by HA or NaB. This effect was less pronounced in non-cancer MRC-5 fibroblasts. In the later intervals, the number of A2780 living cells was strongly decreased by treatment using a combination of NaB and HA. This simultaneous application had no considerable effect in MRC-5 fibroblasts. The combination of NaB and HA led to the suppression of cells in the G1 phase and caused an accumulation of cells in the S and G2 phase in comparison to those treated with NaB and HA alone. Treatment of cells with NaB alone led to the activation of proteins regulating the cell cycle. Notably, p21^WAF1/Cip1 was upregulated in both A2780 and MRC-5 cells, while checkpoint kinases 1 and 2 were activated via phosphorylation only in A2780 cells. Unexpectedly, NaB in combination with HA suppressed the phosphorylation of Chk2 on threonine 68 and Chk1 on serine 345 in A2780 cells and downregulated p21^WAF1/Cip1 in both tested cell lines. The sensitization of cells to HA and NaB treatment seems to be accompanied by increased histone acetylation. NaB-induced acetylation of histone H3 and H4 and histone acetylation increased markedly when a combination of NaB and HA was applied. Whereas the most prominent hyperacetylation after HA and NaB treatment was observed in A2780 cells, the acetylation of histones occurred in both cell lines.

CONCLUSION

In summary, we have demonstrated the enhanced activity of HA and NaB against A2780 cancer cells, while eliciting no such effect in non-cancer MRC-5 cells.

Effect of somatostatin on repair of ionizing radiation-induced DNA damage in pituitary adenoma cells GH3

Ionizing radiation and somatostatin analogues are used for acromegaly treatment to achieve normalization or reduction of growth hormone hypersecretion and tumor shrinkage. In this study, we investigated a combination of somatostatin (SS14) with ionizing radiation of (60)Co and its effect on reparation of radiation-induced damage and cell death of somatomammotroph pituitary cells GH3. Doses of gamma-radiation 20-50 Gy were shown to inhibit proliferation and induce apoptosis in GH3 cells regardless of somatostatin presence. It has been found that the D(0) value for GH3 cells was 2.5 Gy. Somatostatin treatment increased radiosensitivity of GH3 cells, so that D(0) value decreased to 2.2 Gy. We detected quick phosphorylation of histone H2A.X upon irradiation by the dose 20 Gy and its colocalization with phosphorylated protein Nbs-1 in the site of double strand break of DNA (DSB). Number of DSB decreased significantly 24 h after irradiation, however, clearly distinguished foci persisted, indicating non repaired DSB, after irradiation alone or after combined treatment by irradiation and SS14. We found that SS14 alone triggers phosphorylation of Nbs1 (p-Nbs1), which correlates with antiproliferative effect of SS14. Irradiation also increased the presence of p-Nbs1. Most intensive phosphorylation of Nbs1 was detected after combined treatment of irradiation and SS14. The decrease of the number of the DSB foci 24 h after treatment shows a significant capacity of repair systems of GH3 cells. In spite of this, large number of unrepaired DSB persists for 24 h after the treatment. We conclude that SS14 does not have a radioprotective effect on somatomammotroph GH3 cells.