PARP9 and breast cancer: In the TRAIL-sensitive MDA-MB-231 breast cancer cell line, and the TRAIL-resistant MDA-MB-468 human breast cancer cell line, berberine acts synergistically with TRAIL but it also sensitizes resistant cells, which was confirmed with the markers of the process: caspase-3, PARP 9 Poly (ADP-ribose) polymerase 1 cleavage, and p53.