Table 2

Activity of mutationally activated Trk-Met in NIH 3T3 cells

TRK-MET construct*Focus formation (no. foci/μg DNA) TumorigenicityMetastasis§
NGF (−)NGF (+)No. mice with tumors/ no. mice injectedMean tumor size in mm2No. mice with lung metastasis/ no. mice injected
Control850/500/5
Wild type13>3000/500/5
M1268T>300>3005/52454/4
L1213V74>3005/51334/4
Y1248H105>3005/52575/5
D1246H68>3005/5994/4
  • * The control construct is the empty pMex expression vector; the wild-type construct encodes murine Met; M1268T, L1213V, Y1248H, and D1246H encode mutationally activated Met. Each Met molecule is in the pMex vector, which utilizes the Moloney murine sarcoma virus long terminal repeat promoter. 

  • NIH 3T3 cells transfected with the indicated constructs were scored for focus formation after approximately 2 weeks. Samples receiving NGF were treated with this ligand at 100 ng/ml throughout the duration of the assay. Similar results were obtained in two independent experiments. 

  • NIH 3T3 cells were cotransfected with the indicated construct plus pSV2 Neo, selected as pools of G418-resistant cells, and injected s.c. into nude mice at 8 × 105 cells per animal. Tumors were measured after 17 days. Mice injected with cells expressing wild-type Trk-Met were tumor-free even after 2 months. 

  • § NIH 3T3 cells were cotransfected with the indicated construct plus pSV2 Neo, selected as pools of G418-resistant cells, and injected i.v. into the tail vein of nude mice at 8 × 105 cells per animal. Animals were sacrificed after 4 weeks (or earlier for animals in distress) and examined for lung metastasis. All animals positive for metastasis presented with severe metastatic burden. Mice injected with cells expressing wild-type Trk-Met were metastasis-free even after 2 months.