MGMT and neoplasm: Of patients with evaluable tumor biopsies, 50% demonstrated a significant increase in Rad51 foci (with or without γH2AX and pNbs1, indicators of DNA double strand breaks), documenting that the combination produces replication stress as intended; however, these nuclear DDR biomarkers cannot distinguish between genomic injury resulting from a lack of MGMT-mediated repair or inhibition of BER.