NPcis, <i>fos</i>(−/−) mice do not generate tumors.

Tumor burden in all NPcis littermates was determined (or confirmed in the case detection was prior to sacrifice) at the time of death of the NPcis, fos(−/−) mice. No differences were observed in tumor burden between NPcis, fos(+/+) and NPcis, fos(+/−) mice which were pooled as a single group and compared to their NPcis, fos(−/−) littermate. Mean tumor incidence in the NPcis, fos(+/+) plus NPcis, fos(+/−) animals was 71.4% (n = 13) contrasting with the 0% (n = 6) found in the NPcis, fos(−/−) group. *v.a.s.: verified at sacrifice.