Inhibition of neuroblastoma tumor progression by SPARC peptides FSEN and FSEC in the preclinical model of neuroblastoma. (A) Mice with xenografted SMS-KCNR neuroblastoma cells received intraperitoneal injection of PBS, 10 mg/kg of the SPARC peptides FSEN or FSEC, or scrambled peptide scFSEN five times a week for 2 weeks. Treatment with the SPARC peptide FSEC resulted in a statistically significant (p < 0.05) decrease in the average size of tumors starting from day 4 until the end of the treatment period. The average tumor weight was reduced to 26% (p = 0.01) of average control tumor weight. The average weight of tumors treated with peptide FSEN was reduced to 88%, but the decrease was not statistically significant (p = 0.83). Scrambled peptide did not affect tumorigenicity of neuroblastoma xenografts (102%, p = 0.97). (B) Representative photographs of neuroblastoma tumors treated with the SPARC peptides. (C) Normalization of the blood vessels in the SPARC peptide-treated xenografts. H&E staining of areas with large blood vessels at ×200 and ×400 magnification shows areas of extensive hemorrhage and MVP in control tumors and tumors treated with the scrambled peptides. In contrast, no evidence of hemorrhage or MVP was seen the SPARC peptide-treated tumors.