Figure 7. CTSB inhibition reduces ErbB2+ breast cancer cell tumorigenesis.

(A) 21MT1 cells cultured on FITC-gelatin were treated with DMSO vehicle or CTSB inhibitor (CA074; 25 μg/ml) for 48h and degradation analyzed as in Figure 5G. (B) Quantification of FITC-gelatin degradation shown in 7A. Mean ± S.D., n=4. (C) 21MT1 cells seeded on Matrigel-coated Transwell invasion membranes were treated with DMSO (control) or CA074 (25 μg/ml) for 24h, and cells that had invaded through Matrigel to the bottom surface were stained with CyQuant GR fluorescent dye and quantified using a fluorescence reader. Mean ± S.D., n=3. (D) FITC-gelatin matrix degradation by MDA-MB-231 cells was analyzed after 48h culture in DMSO (control) or CTSB inhibitor (CA074; 25μg/ml) as in Figure 5G. (E) Quantification of FITC-gelatin degradation shown in 7D. Mean ± S.D., n=4. (F) Invasion of MDA-MB-231 cells incubated with DMSO (control) or CA074 (25 m/ml) as in Fig. 6C. Mean ± S.D., n=8. (G) Groups of 9 nude mice carrying BT474 xenografts (average 0.5 cm³ size) received Trastuzumab (via tail vein; 4 mg/kg every 4 days), CA074 (i.p., 25 mg/kg in saline daily) or saline (control), and tumor volumes were monitored every other day. Mean +/- SEM., n=9; * = p<0.05, ** = p<0.01, *** = p<0.001.