Eight-week old NOD/SCID females were injected with 1??103, 1??104 or 1??105 non-targeting or S4kd MDA-MB-231 cells, and monitored for palpable tumor formation every 2?days. Spry4 shRNAs significantly suppressed the expression of endogenous Spry4 in MDA-MB-231 cells. Suppressing Spry4 expression increased MDA-MB-231 cell proliferation and migration. Suppressing Spry4 increased 3-integrin expression, and CD133+CD44+ subpopulation. Suppressing Spry4 increased mammosphere formation, while decreasing the sensitivity of MDA-MB-231 cells to Paclitaxel treatment. Finally, suppressing Spry4 increased the potency of MDA-MB-231 cell tumor initiation, a feature attributed to cancer stem cells. Conclusions Our findings provide novel evidence that endogenous Spry4 may have tumor suppressive activity in breast cancer by suppressing cancer stem cell properties in addition to negative effects on tumor cell proliferation and migration. Electronic supplementary material The online version of this article (doi:10.1186/s12935-016-0292-7) contains supplementary material, which is available to authorized users. test. P?13-Methylberberine chloride as statistically significant. Results Suppression of Spry4 in MDA-MB-231 cells promotes cell proliferation and migration in vitro MDA-MB-231 is usually a 13-Methylberberine chloride human breast cancer cell line that endogenously produces Spry4 protein (Fig.?1a). To examine the role of Spry4 in regulation of the malignant phenotype of these cells, we performed shRNA-mediated knockdown of human Spry4 compared to a non-targeting control. Stable knockdown of Spry4 (S4kd) and non-targeting control (NT) cell lines Kit were obtained by puromycin selection. Three different shRNAs targeting Spry4 were utilized, and two of them efficiently reduced Spry4 protein to undetectable levels (S4kd#1 and S4kd#2) (Fig.?1a). Growth curve analyses showed that suppression of Spry4 led to an increase in cell number over a ten-day cell growth period (Fig.?1b). Cell cycle analyses confirmed that this increased growth by suppressing Spry4 associated with the increased cells in S and G2/M phases (Additional file 1). We also tested cell migration, since highly motile cells are associated with cancer metastasis. A scratch assay was used in the presence of mitomycin C to suppress cell proliferation. Cell migration into the denuded area was quantified at 24 and 48?h. Physique?1c, d show that knockdown of Spry4 increased cell migration, with closure of the denuded area more quickly than the control cells. These data show that loss of Spry4 increases both proliferation and migration in MDA-MB-231 cells, suggesting that endogenous Spry4 protein acts to suppress these activities. Open in a separate window Fig.?1 Suppressing Spry4 expression enhances MDA-MB-231 cell growth and migration. a Immunoblotting assay shows that two out of three Spry4 shRNAs effectively decreased Spry4 protein levels compared to NT control. b Growth curve analysis shows that suppressing Spry4 expression increased MDA-MB-231 cell growth. c Representative images of scratch assays from three impartial experiments show that suppressing Spry4 expression increased cell migration into the denuded area. d Quantification of cell migration capacity from one of three experiments. *p?