Figure 5.

In vivo assessment of optimal treatment regimen in an endogenous murine PDAC model

(A) Schematic representation of the treatment schedule applied in the endogenous (KPC) murine model of spontaneous tumor formation as well as the magnetic resonance imaging (MRI) time points applied. Cohort C: continuous treatment with the combination of SHP2i and ERKi daily; cohort D: intermittent treatment with the combination of SHP2i and ERKi 5 days on/2 days off; and cohort E: semi-continuous treatment schedule with daily dosing of SHP2i and intermittent dosing with ERKi 5 days on/2 days off. Control mice were treated with vehicle for 14 consecutive days. All treated mice were sacrificed on day 15, and tumors were resected for histological analysis.

(B) Representative MRI scan slices depicting PDAC tumor sections of KCP mice treated with vehicle (n = 5), cohort C (n = 7), cohort D (n = 7), or cohort E (n = 6) at the indicated time points (days) following the start of therapy (pre), with similar results among the groups. Volumetric measurements indicate a decrease in pancreatic volume in mice treated with the combination of SHP2i and ERKi for 2 weeks compared with vehicle-treated mice. The y axis shows pancreatic volume change in percentage quantified by measurements of MRI scans. Each bar represents the difference in pancreatic volume in an individual animal from days 0 to 15. According to the RECIST criteria, black indicates progressive disease, dark gray indicates stable disease, and light gray indicates partial response. Significance was determined by one-way ANOVA with Bonferroni’s multiple comparison test. Volume-tracking curves for individual mice over the whole course of therapy are available in Figures S3B–S3E.

(C) Macroscopic images of pancreas and spleen (top row). Representative H&E-stained sections of pancreata from mice, treated as indicated. Scale bars represent 1,000 (middle) and 200 μm (bottom). Mice numbers are indicated below.

(D) Relative pancreatic weight was significantly lower in all groups treated with the combination of SHP2i and ERKi: cohort C (n = 7), cohort D (n = 6), and cohort E (n = 7) compared with vehicle-treated control mice (n = 9). Results represent mean ± SD. ∗p < 0.05, ∗∗∗p < 0.001, significance was determined by one-way ANOVA with Bonferroni’s multiple comparison test.

(E) Quantification of relative intact acinar area as ratio of whole pancreatic area. Analysis performed on n = 4 individual mice in vehicle group and on n = 6 individual mice in cohort C. Results represent mean ± SD.

(F) Ki67-positive cells in percentage quantified in pancreata of mice treated with vehicle (n = 6) or with the combination of SHP2i and ERKi daily (n = 7). Results represent mean ± SD. ∗∗p = 0.0044, significance was determined by unpaired t test.

See also Figures S3, S4, and S6.