Fig 2: Depletion of CLK2 decreases the expression of Ki-67 and phosphorylation of AKT/FOXO3aA-B. immunohistochemical stains of GSC11 and GSC272 tumor samples obtained from orthotopic murine xenografts. A, immunofluorescent stains for CLK2 and the stem cell marker nestin in GSC11 and GSC272 mouse xenografts with or without infection with CLK2 shRNA are shown. CLK2 was labeled as red and nestin as green. Expression of CLK2 and nestin overlap. B, Ki-67–positive cells stained brown with hematoxylin counterstain of nuclei. The bar graph shows the numbers of Ki-67–positive cells in vector-infected and CLK2-knockdown xenografts. C, immunofluorescent stains for phosphorylated AKT and FOXO3a in murine GSC11 and GSC272 cells. Phosphorylated AKT and FOXO3a stained red, and the nuclei were counterstained with 4',6-diamidino-2-phenylindole (blue).

Fig 3: Role of CLK2 expression in GSCsA, GSC lysates were collected, and CLK2 expression in the lysates was detected using Western blot analysis. B, GSC11, GSC272, GSC7-2 and GSC17 cells were infected with a lentivirus containing a control vector, CLK2 shRNA1, or CLK2 shRNA2. C, Hierarchical clustering was applied to protein expression data from RPPA results in vector shRNA and CLK2 shRNA in GSC272 cells. The protein expression levels in CLK2 shRNA-infected cells differed at least 1.6-fold from those in control GSC272 were selected for hierarchical clustering analysis. The red and green colors in the cells reflect relatively high and low expression, respectively. D, the cells were infected with a lentivirus containing a control vector or CLK2 shRNA, a volume of CellTiter-Glo Reagent was added to cells, and the luminescence was recorded. E, the GSCs per well were added to a 96-well plate with 20 µl of a combined MTS/PMS solution, and the plate was incubated for 3h 30min at 37°C in a humidified atmosphere. *P < 0.05; **P < 0.01; ***P < 0.001 versus control.

Fig 4: CLK2 inhibition with a novel CLK inhibitor (GW807982X and CLK2i) specifically targets TMZ-resistant GBM cells.(A) Quantified IF of pSR (1H4) intensity in TMZ-treated cells with (?H2AX+) or without (?H2AX-) DNA damage; two-tailed t test. (B) Association between CLK2 mRNA expression and OS from GlioVis CGGA GBM recurrent patient samples; log-rank (Mantel-Cox) test. (C) Association between CLK2 expression and increasing tumor grade from the CGGA dataset; one-way ANOVA. (D) Change in RNA sequencing RPKM of CLK-1 to CLK1-4 in three matched patient samples from primary (1°) GBM and post-TMZ treatment (2°) (71). *P < 0.05, **P < 0.001, ***P < 0.0005, and ****P < 0.0001. (E) Western blot of CLK2 expression in GBM TMZ-sensitive, TMZ-treated, and TMZ-resistant cell lines. (F) FACS analysis for cell cycle profile in response to 5 µM CLK2i versus DMSO vehicle control treatment for 24 hours; three biological replicates with one-way ANOVA. (G) Relative cell numbers following 24-hour treatment with 5 µM CLK2i versus DMSO vehicle control; three biological replicates with t test. (H) Sub-G1 or apoptotic DNA content in cells analyzed in (G); three biological replicates with t test. RSEM, RNA-Seq by Expectation-Maximization; RPKM, Reads Per Kilobase of transcript, per Million mapped reads.

Fig 5: Cytoplasmic EWSR1 aggregates are detected in GBM clinical specimens.(A) EWSR1 IHC of six representative GBM patients with cytoplasmic aggregation of EWSR1 (red box inset). (B) Quantification of EWSR1 aggregative positive cells between primary (Prim) and recurrent (Recur) matched patient samples. (C) Representative images of CLK2 IHC from matched patient samples. (D) Quantification of CLK2-positive cells between primary and recurrent matched patient samples from images in (C). OS in months. Scale bars, 20 µm (A) and 100 µm (D). *P < 0.05.