The observations made here that PARP inhibition increased PI3K/mTOR signaling, in combination with our previous report that SCLC cell lines with higher PI3K/mTOR activity are less sensitive to PARP inhibitor talazoparib, suggest that this pathway is a both a marker of inherent resistance and a potential mechanism of acquired resistance to PARP inhibition. This evidence concerns the gene MTOR and small cell lung carcinoma.