Figure 7. Combined inhibition of ABL and ATR kinases in SCLC impairs replication fork progression, decreases metastatic colonization, and enhances survival of tumor-bearing mice.

(A) Schematic representation of the DNA fiber assay.

(B) DMS53 cells were treated with ABL inhibitor GMB475 (GMB, 5 μM, 24 h), ATR inhibitor M6620 (1 μM for the last 30 min), each inhibitor alone or in combination (double), followed by sequential labeling with thymidine analogs CldU (50 μM) and IdU (100 μM), respectively for the indicated times. Representative images and quantification (represented as mean +/− SEM) of DNA Fiber length (n = 50) are shown. Scale bars, 5 μm. Statistics were performed with a one-way ANOVA: ****p < 0.0001.

(C) NCI-H69 cells were intracardiac injected into nude mice. Following BLI, mice were then divided into 4 groups (n = 8 each group). Starting on day 20 post-injection, mice were treated by oral gavage with vehicle control, ABL001 (100 mg/kg) once daily, M6620 (60 mg/kg) 4 times a week, or ABL001 plus M6620 double treatment. Mice were imaged at day 52.

(D) Percentage of mice surviving over the indicated times (days). Log rank (Mantel-Cox) test: *p = 0.013.

(E) Mouse brain with tumor was dissected; cerebral cortex (left and right sides), cerebellum, and skull were imaged in separate wells.

(F) NCI-H82 cells were engrafted in both flanks of nude mice. Mice were randomly enrolled into drug treatment groups once growing tumor volumes reached approximately 100 mm³. Mice were treated once daily by oral gavage with vehicle control (n = 6 tumors), ABL001 (100 mg/kg; n = 6 tumors), M6620 (60 mg/kg; n = 5 tumors), or ABL001 plus M6620 double treatment (n = 6 tumors). Statistics were performed with a two-way ANOVA with treatment groups compared against the control: **p < 0.01, ns = not significant. Data represented as mean + SEM.