Figure 7. MS67-mediated WDR5 degradation and mTOR inhibition cooperatively reduces translation and triple-negative breast cancer (TNBC) cell growth.

(A) Western blot analysis of the indicated proteins in LM2 cells treated for 3 days with 2.5 μM MS67N or MS67 in combination control, 2 μM OSI-027, or 5 nM everolimus. (B) Western blot analysis of the indicated proteins in MDA-MB-453 cells treated for 3 days with 2.5 μM MS67N or MS67 in combination with control, 0.5 μM OSI-027, or 1 nM everolimus. (C) Normalized translational rates in MDA-MB-453 cells from (B) (n=3, one sample t test). *p=0.0209 (MS67N versus MS67), ****p<0.0001 (MS67N versus MS67N +OSI-027), ****p<0.0001 (MS67N versus MS67 +OSI-027), ****p<0.0001 (MS67N versus MS67N +everolimus), ****p<0.0001 (MS67N versus MS67 +everolimus), ****p<0.0001(MS67N +OSI-027 versus MS67 +OSI-027), and ****p<0.0001(MS67N +everolimus versus MS67 +everolimus). (D–E) Colony formation assay of LM2 cells treated for 9 days with 5 μM MS67N or MS67 in combination with control or 2 μM OSI-027. Representative images (D) and quantification (E) are shown. ****p<0.0001 (MS67N versus MS67), ****p<0.0001 (MS67N versus MS67N+OSI-027), ****p<0.0001 (MS67N versus MS67 +OSI-027), ***p=0.0004 (MS67 versus MS67 +OSI-027), and ****p<0.0001 (MS67N+OSI-027 versus MS67 +OSI027). (F–G) Colony formation assay of LM2 cells with 5 μM MS67N or MS67 in combination with control or 5 nM everolimus for 9 days. Representative images (F) and quantification (G) are shown. ***p=0.0005 (MS67N versus MS67), ***p=0.0004 (MS67N versus MS67N +everolimus), ***p=0.0002 (MS67N versus MS67 +everolimus), ***p=0.0003 (MS67 versus MS67 +everolimus), and ***p=0.0008 (MS67N +everolimus versus MS67 +everolimus). (n=3, unpaired two-side Student’s t test). *p<0.05; **p<0.01; ***p<0.001; ****p<0.0001. Calculation of coefficients of drug interaction (CDIs) is described in Materials and methods section. Significant synergy is labeled with (#). For gel source data, see Figure 7—source data 1 and Figure 7—source data 2.