Loss of p27Kip1
on the SmoA1 background facilitates tumor progression. (A) SmoA1, p27wt/- and SmoA1, p27−/− mice demonstrated a significantly higher incidence of invasive and effaced tumors than SmoA1, p27wt/wt littermates. A Fisher’s exact test was used to generate p values. (B) SmoA1, p27wt/- and SmoA1, p27−/− tumors demonstrated an increased proliferative index as determined by Bromodeoxyuridine (BrdU) uptake. Cerebellar sections were stained with an antibody recognizing BrdU and five high power fields (HPF) were scored for each sample. Bars represent the average number of BrdU positive cells per HPF, and error bars represent the standard error. A t test was used to determine p values. (C-D) Immunohistochemistry with monoclonal antibodies recognizing p27Kip1 and cyclinD1 demonstrated that tumor progression is associated with decreased p27Kip1 and increased cyclinD1 protein levels within tumors. Representative cerebellar sections from SmoA1, p27wt/- cerebella showing p27Kip1 and cyclinD1 immunostaining in a non-invasive tumor with no effacement (NI/NE; C) and in a tumor with invasion and effacement (I/E; D).