MMP1 and neoplasm: The incidence of tumor formation by the MMP-1 knockdown cells was moderately reduced compared with the control cell lines (231-BR-shNTC, 100% tumor take compared with 231-BR-sh1b, 67% tumor take; 231-BR3-shCtr, 80% tumor take, compared with sh1, 60%), although the differences were not statistically significant, using Fisher’s Exact test (Additional file 2).