The normal human H-ras1 gene can act as an onco-suppressor.

The altered morphology and tumorigenic phenotypes of rat 208F fibroblasts transformed with the human T24 H-ras1 oncogene is suppressed by transfection with the human normal H-ras1 gene. In the suppressed cells, both the normal and mutant T24 ras gene products are expressed although the normal p21 is expressed at a higher level. Rare transformants or tumours derived from suppressed cells possess reduced expression of normal ras p21. Our findings suggest that transforming ras alleles do not behave in a dominant manner and that elevated expression of the normal allele could cause suppression of the morphologically transformed and tumorigenic phenotypes.