PDCD1 and neoplasm: We also observed a corresponding increase in phosphorylation of CHK1 at Ser 345 in the 4T1ch9 tumours, in contrast to the results observed in AT3 tumours treated with reduced doses, suggesting that the lack of anti-tumour response observed in these two models treated with combined olaparib, AZD1775 and anti-PD-1 was not associated with the level of DNA damage signalling in the tumours indicated by the phosphorylation of CHK1.