Subgroup analyses showed that PARP overexpression was significantly related to poor OS in patients with breast cancers (HR = 1.38, 95% CI = 1.28–1.49, p < 0.001), ovary cancers (HR = 1.21, 95% CI = 1.10–1.33, p = 0.001), lung cancers (HR = 2.11, 95% CI = 1.29–3.45, p = 0.003), and liver cancers (HR = 3.29, 95% CI = 1.94–5.58, p < 0.001). Here, PARP1 is linked to liver cancer.