Figure 6.

Effects of long-term trametinib administration to mice on drug sensitivity of xenograft-derived organoids. Experimental schema of generation of xenograft-derived organoids from trametinib administered and vehicle-administered mice and the analysis (a). Bright field (b) and H&E staining (c) images of the vehicle (XDO-C) and trametinib (XDO-T) administered mice-derived tumor organoids. Scale bar: 500 μm. Sensitivity to trametinib (d, n = 3–6) and carboplatin (e, n = 3–6) was analyzed by Prestoblue kit. Results were expressed as mean ± S.E.M. 100% represents the cell viability of each control. Expression of a carboplatin sensitivity-related gene, MSH2 mRNA in each organoid was determined by quantitative real-time PCR. Expression level of gene was quantified based on the ration of expression level to GAPDH (f, n = 4). Results were expressed as mean ± S.E.M. ﹡P < .05 vs. vehicle. Expression level of MSH2 in xenografted tumor-derived organoids and original tissues (g, n = 3) from trametinib- or vehicle-administered mice. Scale bar: 50 μm. Schematic summary of the present study (h). Trametinib promoted cell cycle arrest, inhibited stemness, changed the phenotype of BC organoids, which may lead to the inhibitory effects of tumorigenesis in vivo. Besides, long-term trametinib administration enhanced the sensitivity to carboplatin through upregulation of MSH2 gene in the tumor tissues