p21 limits S phase DNA damage caused by the Wee1 inhibitor MK1775

Area of Science:

• Molecular Biology
• Cancer Research
• Cell Cycle Regulation

Background:

• Wee1 inhibitors, such as MK1775 (AZD1775), are under investigation for cancer treatment.
• The role of p21, a p53 target and CDK inhibitor, in response to Wee1 inhibition is not fully understood.

Purpose of the Study:

• To investigate the protective role of p21 against DNA damage induced by the Wee1 inhibitor MK1775.
• To elucidate the S-phase specific functions of p21 in response to Wee1 inhibition.

Main Methods:

• Utilized p21-deficient cancer and normal cell lines (HCT116 p21-/-, RPE p21-/-, and U2OS p21 siRNA).
• Assessed DNA damage markers (γH2AX, phospho-DNA PKcs, phospho-RPA) and cell cycle progression following MK1775 treatment.
• Evaluated cell death and sensitization to combination therapies (MK1775 with CHK1 inhibitor AZD6772 or ionizing radiation).

Main Results:

• p21-deficient cells exhibited increased γH2AX induction and DNA breakage markers upon MK1775 treatment during S-phase.
• p21 deficiency led to increased MK1775-induced cell death in cancer cells.
• p21 deficiency sensitized cells to combined treatments with MK1775 and AZD6772 or ionizing radiation.

Conclusions:

• p21 plays a protective role against Wee1 inhibitor-induced DNA damage, primarily through its S-phase functions.
• p21 deficiency enhances sensitivity to Wee1 inhibition, suggesting its potential as a predictive biomarker for Wee1 inhibitor therapy.
• Consideration of p21 expression levels may be crucial for optimizing the clinical application of Wee1 inhibitors.