Chemotherapy treatment of cancer often employs compounds, such as Etoposide, which work by causing double-stranded DNA breaks, leading to cell apoptosis. Cells respond to this damage by instituting pathways of DNA repair, involving activation of the PI3K family of enzymes, including DNA-PK. Much research has been done to find a specific DNA-PK inhibitor to increase the effectiveness of chemotherapies. The 2-morpholine substituted-1,3-benzoaxine family of compounds are promising chemo sensitising agents.
Several compounds have been produced with varying degrees of sensitisation; one compound, with the amino acid alanine attached to the basic benzoxaxine structure (LTUSi54), had minimal inhibition of DNA-PK, but appears to play a role in cell cycle arrest in HeLa cells (cervical cancer).
HeLa cells were treated for 4 hours with various combinations of Etoposide and / or LTUSi54, followed by 2 days recovery time in the presence of LTUSi54 alone. Treatment with either Etoposide or LTUSi54 alone caused a significant reduction in cell number, while the combination further reduced cell number.
Analysis of the cell cycle after 4 hours treatment and 2 days recovery, showed an increased in sub G1 (apoptosis) in the presence of Etoposide alone and the combination Etoposide / LTUSi54. A significant reduction in G1 cells was seen with Etoposide and combination treated cells. There was also a corresponding increase in cells in both the S phase and the G2/M phase.
Using a human phosphokinase array, cells treated with LTUSi54 for 4 hours showed increased expression of three cell cycle check point proteins; p38α, Extracellular signal-regulated protein kinases 1 and 2 (ERK1/2) and p53.
These results suggest that LTUSi54 is increasing the expression of three cell cycle proteins and inhibiting cell cycle progression through a block in the transition of cells from the S to G2/M phase.