WEE1 Inhibitor Adavosertib Exerts Antitumor Effects on Colorectal Cancer, Especially in Cases with Mutations.

Inhibition of WEE1, a key regulator of the G2/M checkpoint of the cell cycle, induces apoptosis by initiating mitosis without repairing DNA damage. However, the effects of WEE1 inhibitors on the tumor immune microenvironment in colorectal cancer (CRC) remain unclear. Here, we investigated the association between WEE1 expression and CRC clinicopathological features using surgically resected CRC specimens and assessed the antitumor effects of a WEE1 inhibitor using CRC cell lines and orthotopic transplantation mouse models. WEE1 expression was not correlated with the clinicopathological features of CRC. The WEE1 inhibitor suppressed cell proliferation in a concentration-dependent manner in all CRC cell lines. It also increased the percentage of cells in the G2/M phase and apoptotic cells, especially in cell lines with mutations, but did not alter these cell percentages in most wild-type cell lines. In the orthotopic mouse model of CRC, tumor volume was significantly reduced in the WEE1 inhibitor-treated group compared to that in the control group. RNA sequencing and immunohistochemistry analyses of mouse tumors revealed that treatment with the WEE1 inhibitor activated tumor immunity and suppressed stromal reactions. These results demonstrate the potential antitumor effects of WEE1 inhibitors in CRC, particularly in patients with mutations.