MRJ(L) retards tumor growth rate and metastasis. (a,b) Mammalian relative of DnaJ (MRJ) long isoform (MRJ [L]) expressors and corresponding vector control cells (106/site) from MDA-MB-435 (panel a) and MDA-MB-231 (penal b) were injected into exposed axillary mammary fat pads of 6-week-old, female athymic mice. Tumor size was measured weekly. Eight mice were used per group and the experiment was repeated once. The results are expressed as the mean tumor diameters ± standard error. (c) The experimental metastasis assay (lung colonization asay) was performed by injecting 2.5 × 105 MDA-MB-231 cells (in 0.2 ml) into the lateral tail vein of 3- to 4-week-old, female athymic mice. After a period of 6 weeks lungs were removed and fixed with 20% Bouin's fixative in neutral buffered formalin before quantification of surface metastasis. Eight mice were used per group and the experiment was repeated once.