ERBB2 and rhabdomyosarcoma: p21Cip1 was overexpressed in primary rhabdomyosarcomas and in preneoplastic male urethral tissue, as compared to HER-2/neu transgenic male mice, however it was also expressed at high level in female mice, which are not prone to rhabdomyosarcoma development, furthermore it was not up-regulated in the absence of p53 (Figure 1).