PARP1 and colorectal carcinoma: PARP-1 is overexpressed in several human cancers, including CRC [8,9,10,11], in which the expression of PARP-1 seems not to be homogenous in tumour cells, but it is highly expressed in CSCs compared with non-CSCs [12], indicating that PARP-1 could regulate CSC programming, as previously reported [7].