Pyridostatin (RR82) hydrochloride is a G-quadruplex DNA stabilizing agent ( K d =490 nM) and can target DNA and RNA G4s in cells. Pyridostatin hydrochloride promotes growth arrest in human cancer cells by inducing replication- and transcription-dependent DNA damage. Pyridostatin hydrochloride targets the proto-oncogene Src . Pyridostatin hydrochloride reduced SRC protein levels and SRC-dependent cellular motility in human breast cancer cells .