PTBP1 and Ewing sarcoma: Previous studies identified AS regulatory pathways (TRA2A → RSRC2, and PTBP1 → PKM) involved in resistance of triple-negative breast cancer to paclitaxel (a microtubule poison) and of pancreatic cancer to gemcitabine (a DNA synthesis inhibitor), respectively, as well as a splicing factor (hnRNPM) controlling an AS program and cell death response triggered by BEZ235 (a dual PI3K/mTOR inhibitor of potential clinical use) in Ewing sarcoma cells (15,16,55).