Decreasing expression of NM23 gene in metastatic murine mammary tumors of viral etiology (MMTV).

Murine mammary tumors induced by the Murine Mammary Tumor Virus (MMTV) were chosen to study the expression of the NM23 gene during the metastatic process because of their viral etiology, different from that of the previously reported experimental tumor systems. NM23 mRNA levels are higher in non metastatic tumors than in metastatic ones. Moreover, the NM23 expression is higher in tumors induced by the C3H variant of the MMTV than in tumors induced by the RIII variant. These data are a further support to the hypothesis of a basic role of the NM23 gene in the down-regulation of tumor progression.