Flat revertants isolated from Kirsten sarcoma virus-transformed cells are resistant to the action of specific oncogenes.

Abstract

Two flat revertants have been isolated from mutagen-treated populations of Kirsten murine sarcoma virus (KiMuSV)-transformed NIH/3T3 cells. These revertants, which appear to be cellular variants resistant to transformation by the KiMuSV oncogene v-Ki-ras, contain Ki-MuSV-specific DNA, elevated levels of the v-Ki-ras gene product p2l, and rescuable transforming virus. Cell hybridization studies indicated that the revertant phenotype is dominant in hybrids between revertant cells and cells transformed by Ki-MuSV or the closely related Harvey MuSV and BALB MuSV. Analysis of hybrid cells resulting from the fusion of these revertants to cell lines transformed by other retroviruses showed that the action of certain oncogenes structurally unrelated to v-Ki-ras also could be suppressed. Thus, there appear to be functional relationships and diversities among transforming genes (oncogenes) not readily apparent from their structural characteristics.Recent molecular studies have defined the structure of a number of transforming genes (oncogenes) and their products in considerable detail (reviewed in ref. 1). All of the known retroviral oncogenes are closely related to sequences present in normal vertebrate cells (cellular proto-oncogenes), from which they appear to have arisen (1, 2). The viral oncogenes associated with Kirsten and Harvey murine sarcoma viruses (Ki-and Ha-MuSVs), v-Ki-ras and v-Ha-ras, for example, are known to encode similar phosphorylated 21,000-dalton proteins (designated p2ls) with guanine nucleotide-binding activities (3-6). v-Ki-ras and v-Haras are structurally related to highly conserved cellular sequences (proto-oncogenes), some of which may be associated with the etiology of certain human tumors (refs. 7 and 8; reviewed in refs. 9 and 10).In spite of the relatively large body of information concerning the molecular structure of retrovirus oncogenes and the proteins that they specify, comparatively little is known about the cellular components with which these proteins interact and the mechanism(s) by which they transform cells. The nature of the cellular components involved in the expression of transformation can be defined theoretically by the isolation and molecular characterization of flat nontransformed variants (revertants) from populations of retrovirus-transformed cells. Although a number of such flat revertants have been isolated from cells transformed by retroviruses (refs. 11-21; reviewed in ref. 22), the great majority of these has been shown to lack expression of functioning viral oncogenes. A few revertant cell lines containing apparent alterations in host cell genomes have been isolated (13, 21); however, little is known about the specific cellular factors involved in the reversion process.This report describes two cellular revertants that are resistant to transformation by Ki-MuSV and certain other retroviruses. These revertants may be used to study the mechanism of transformation by the v-Ki-ras oncogene and to reveal functional relationships among different viral oncogene...

Involvement of the SKP2–p27KIP1 pathway in suppression of cancer cell proliferation by RECK

“…When this virus was infected into a v-K-ras-transformed NIH3T3 subline, DT (Noda et al, 1983), the cells, as expected, showed increased RECK expression ( Figure 1a) and increased spreading ( Figure 1b). We determined the gene expression profiles of DT cells infected with the control virus (Ad-Z) or Ad-RECK using Affymetrix Mouse Genome 430 2.0 Arrays (Affymetrix, Santa Clara, CA, USA).…”

Up-regulation of ras-GAP genes is reversed by a MEK inhibitor and doxorubicin in v-Ki-ras-transformed NIH/3T3 fibroblasts

“…v-Ki-ras-transformed NIH/3T3 fibroblasts (DT) [25] and parental mouse NIH/3T3 cells were grown in Dulbecco`s modified Eagle`s medium (DMEM), supplemented with 10% (v/v) fetal calf serum (FCS). v-Ha-ras-transformed rat fibroblasts (tet-H-ras/CREF: tet-off) and parental cells (tet-H-ras/CREF: tet-on) [29] were grown as the above condition.…”

“…To know whether Ras-Gap gene expressions are up-regulated and linked to the tumor biological activity in ras-tranformed cells, we compared mRNA expressions of four ras-Gap genes (p120-Gap, Gap1 m , GapIII, Nf1) between DT [25] and parental NIH/3T3 cells, and studied their sensitivity to anti-cancer drugs. We also measured the viral oncogene v-Ki-ras, PIK3CA which encodes the p110α catalytic subunit of PI3K [1], p53 that encodes a transcription factor which induces cellular senescence in response to oncogenic Ras signals [26], and PTEN tumor suppressor gene that encodes a phosphatase [27] which inhibits ras transformation in NIH/3T3 cells [28].…”

Transformation by ras modifies AP1 composition and activity

“…Four clones R2, R3, R4 and R5 were selected and expanded for further analysis. In addition, a well characterized NIH3T3-derived cell line (DT) transformed by incorporation of two copies of a Ki-ras gene (Noda et al, 1983) was also used in this study and renamed for convenience R1. Ras expression, the transformed phenotype, and the Jun and Fos protein levels were monitored for each clone.…”