Impact of Wee1 inhibition on the hypoxia-induced DNA damage response

Tumor hypoxia is a common feature associated with resistance to current anticancer therapies, such as radiotherapy and chemotherapy. Wee1 is a tyrosine kinase regarded as a gatekeeper of the G 2 /M cell cycle transition. Wee1 has recently been highlighted as a therapeutic target in cells with a deficient G 1 checkpoint, since they are more reliant on the G 2 phase for repair of damage and survival. Here, we have assessed the impact of Wee1 inhibition on hypoxic cells and its therapeutic potential as a single agent under these conditions or in combination with radiation. The p53 null non-small cell lung carcinoma cell line H1299 was used to assess Wee1 phosphorylation and signaling in a range of hypoxic conditions. Inhibition of Wee1 decreased the G 2 population in cells exposed to normoxia (21% O 2 ) or moderate hypoxia (1% O 2 ) but did not effect the cell cycle of cells exposed to levels of hypoxia associated with greatest radio-resistance (<0.1% O 2 ). In addition, DNA damage was induced in response to Wee1 inhibition although this was less significant in cells exposed to <0.1% O 2 . Wee1 inhibitors were then tested as single agents in a 2D and 3D model or in combination with radiation treatment, by clonogenic assay. Following continuous treatment, MK-1775 was shown to sensitize the H1299 cell line to different O 2 tensions. However, in combination with radiation, although MK-1775 had significant efficacy in normoxia, disappointing results were seen when these studies were carried out in hypoxia.