SF3B1 and neoplasm: Pharmacological SF3B1 blockade, which disrupts the spliceosome activity (Fig. 5a), significantly decreased proliferation rate in a time-dependent manner in both cell lines (Fig. 5b) and primary-GBM cell cultures (Fig. 5c), but not in primary non-tumor brain cell cultures (Fig. 5d), suggesting that pladienolide B effects are selectively exerted on GBM cells.