SP1 and fibrosarcoma: Thus, SP1, SP3 and SP4 have been found overexpressed in rhabdomyosarcoma cells and fibrosarcoma-forming transformed human fibroblasts, and its downregulation using tolfenamic acid, reactive oxygen species (ROS)-inducing anticancer agents or specific siRNAs/U1snRNAs resulted in inhibited tumor growth [6, 8, 37, 38].