Stable silence of CypA results in decreased tumor growth and cell proliferation in a nude mouse model of subcutaneous (s.c.) xenograft. (A) Tumor weight (in grams). Insets: a representative mouse picture and s.c. tumor mass from each group. (B) Tumor tissues from M139-shCypA inoculated mice had significant lower levels of CypA-mRNA than those from M139-shV mice. The stability of CypA silencing in tumor tissues derived from M139-shCypA cells was confirmed by real-time PCR. (C) Immunohistochemical staining for CypA and Ki-67. (D) Quantification of Ki-67 immunohistochemical staining. Three tumors per group were analyzed and Ki-67 positive nuclei from four random high power (40×) fields were counted for each tumor tissue. Lower frequency of Ki-67 positive cells is shown in the tissue from M139-shCypA mice compared with that of Ki-67 positive cells from M139-shV mice (** P < 0.05).