Increased lung metastasis in transgenic NM23-Null/SV40 mice with hepatocellular carcinoma.
BACKGROUND
The metastasis-suppressing role of the NM23 gene in the metastatic spread of solid tumors is still debated. We examined the role of NM23 in tumor development and metastatic dissemination by using transgenic mice that lack mouse NM23 (NM23-M1) in two mouse models of hepatocellular carcinoma (HCC) that recapitulate all steps of tumor progression.


METHODS
We induced HCC in mice that contained (NM23-M1(+/+)) or lacked (NM23-M1(-/-)) NM23-M1 by diethylnitrosamine injection or by a crossing scheme that transferred a transgene that leads to liver expression of simian virus 40 large T antigen (ASV mice). We used microscopic examination and immunohistochemistry to analyze tumor progression. Expression of Nm23 protein isoforms (Nm23-M1 and Nm23-M2) and several tumor markers was analyzed in the primary tumor and in metastases by Western blotting. The statistical significance of differences in the incidence of Nm23-M2 overexpression in null mice relative to that in wild-type mice was tested by a one-sided Fisher's exact test. The statistical significance of differences in the incidence of metastases was examined using one-sided chi-square tests. All other statistical tests were two-sided.


RESULTS
In both models, Nm23-M1 and/or Nm23-M2 were overexpressed in the primary liver tumors compared with nontumor liver tissue; however, the lack of the NM23-M1 gene had no effect on primary tumor formation in either model. ASV mice developed pulmonary metastases that were positive for the Hep-Par 1 antibody, which recognizes a specific hepatocyte antigen, whereas the few pulmonary nodules that developed in diethylnitrosamine-injected mice were negative for this antigen. Statistically significantly more ASV/NM23-M1(-/-) mice than ASV/NM23-M1(+/+) mice developed lung metastases (69.2% versus 37.5%; difference = 31.7%, 95% confidence interval = 13.1% to 50.3%; P<.001). In ASV/NM23-M1(+/+) mice, immunohistochemical staining for Nm23-M1 was highly heterogeneous among the primary liver tumors, but weak or negative among lung metastases.


CONCLUSIONS
The lack of NM23-M1 expression promotes metastasis in the SV40 animal model of liver carcinogenesis.
Boissan
Mathieu
M
Unité Institut National de la Santé et de la Recherche Médicale 680, Faculté de Médecine Saint-Antoine, Université Pierre et Marie Curie, Paris, France.
Wendum
Dominique
D
Arnaud-Dabernat
Sandrine
S
Munier
Annie
A
Debray
Marcel
M
Lascu
Ioan
I
Daniel
Jean-Yves
JY
Lacombe
Marie-Lise
ML
D000818:Animals; D000951:Antigens, Neoplasm / Q000378:metabolism; D000957:Antigens, Viral, Tumor / Q000378:metabolism; D014408:Biomarkers, Tumor / Q000378:metabolism*; D015153:Blotting, Western; D016009:Chi-Square Distribution; D019925:Cyclin A / Q000032:analysis; D004052:Diethylnitrosamine; D018450:Disease Progression; D015971:Gene Expression Regulation, Enzymologic; D015972:Gene Expression Regulation, Neoplastic; D007150:Immunohistochemistry; D015994:Incidence; D008099:Liver / Q000201:enzymology; D008114:Liver Neoplasms, Experimental / Q000139:chemically induced / Q000201:enzymology / Q000473:pathology*; D008175:Lung Neoplasms / Q000201:enzymology / Q000556:secondary*; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D054778:NM23 Nucleoside Diphosphate Kinases; D009701:Nucleoside-Diphosphate Kinase / Q000235:genetics; D013539:Simian virus 40 / Q000276:immunology; D015854:Up-Regulation
D000951:Antigens, Neoplasm; D000957:Antigens, Viral, Tumor; D014408:Biomarkers, Tumor; D019925:Cyclin A; D054778:NM23 Nucleoside Diphosphate Kinases; D004052:Diethylnitrosamine; C517939:Nme1 protein, mouse; D009701:Nucleoside-Diphosphate Kinase