In line with this, organoids derived from one of the PARPi-resistant RAD51-negative KB1P(M) tumors (KB1PM7) failed to recapitulate PARPi resistance in vitro but upheld PARPi resistance in vivo, suggesting that PARPi resistance in this tumor may be driven via cell-extrinsic processes that can only be recapitulated in vivo.61 This evidence concerns the gene RAD51 and neoplasm.