Fig. 4. Combination treatment with lapatinib and dinaciclib leads to anti-tumor activity in vivo.

A Approximately, 15 × 10⁶ (15 million) BT-474 cells were injected orthotopically into each NSG mouse (both sides) and monitored for subsequent growth. When tumors were ∼200 mm³, mice were randomized into treatment cohorts: control (no drug), 100 mg/kg lapatinib, 40 mg/kg dinaciclib, and their combination for 30 days. Dinaciclib was administered twice a week via IP injection. Lapatinib was given orally once a day for 5 consecutive days. Tumor measurements were performed daily, and the percentage (%) of changes in volume for each tumor is shown by a waterfall plot (control = 4 tumors, lapatinib = 5 tumors, dinaciclib = 4 tumors, combination = 4 tumors). For statistical analysis one-way Anova test was performed for comparisons between lapatinib, dinaciclib, and combination cohorts. Dunnett’s test was used as post hoc. Differences were considered statistically different if p < 0.05. A p value < 0.05 is indicated by *, p < 0.01 by **, p < 0.001 by ***, and p < 0.0001 by ****. B Weights of the single agents and the combination cohorts of the human xenograft-bearing mice. The number of mice was: control = 5 mice, lapatinib = 5 mice, dinaciclib = 4 mice, and combination = 4 mice. p values were calculated using the two-tailed Student’s t test. C Tumors were harvested from BT-474 tumor-bearing mice approximately 2 h after the last drug administration and tumor lysates were subjected to western blot analyses and probed for the indicated proteins.