Effect of Ha-rasval12 on nm23 expression, tumor formation and metastasis of the transformants, and immunomodulation in tumor-bearing mice.

Overexpression of the Ha-ras val12 oncogene has frequently been detected in primary and metastatic carcinomas. NM23 is a metastasis inhibition factor and plays a suppressive role in metastasis in many types of cancer. In this study, a stable NIH/3T3 cell line harboring an inducible Ha-ras val12 oncogene (designated as 7-4) and small interfering RNAs (siRNAs) were used to clarify the inverse correlation between nm23 and Ha-ras expression both in vitro and in vivo. A derivative 7-4/Z-3 cell line harboring a β-galactosidase reporter gene was used to trace cell metastasis in a murine tumor model. The data presented here reveal that Ha-ras val12 is able to cause cell morphological changes, induce tumor formation, and promote metastasis of tumor cells to the lungs. In mice with metastases, the immune surveillance against tumor formation was suppressed by Ha- ras val12 overexpression through an increase in T-reg cells and a decrease of cytotoxic T lymphocytes and natural killer cell populations. Our results suggest that the Ha-ras oncogene regulates morphogenesis, tumorigenesis, and metastasis through suppressing nm23 expression and modulation of immune cell function. Overexpression of the Ha-ras oncogene has been observed in primary and metastatic human carcinomas. Alterations in Ha-ras per se or its expression have also been reported in metastatic tumors (1). Gallick et al. examined the expression of the c-ras gene in fresh biopsies from primary and secondary colon carcinomas and found that overexpression of p21 ras was common in the primary tumors of Dukes' B and C stages when compared to the surrounding normal