Detection of genes with a potential for suppressing the transformed phenotype associated with activated ras genes

Area of Science:

• Molecular biology
• Cancer research
• Cell biology

Background:

• Kirsten sarcoma virus (v-Ki-ras) induces NIH 3T3 cell transformation.
• Transformed cells exhibit uncontrolled growth and tumorigenicity.
• Identifying genetic factors that reverse transformation is crucial for cancer research.

Purpose of the Study:

• To isolate and characterize revertant cell lines with suppressed transformed phenotypes.
• To investigate the role of normal human fibroblast cDNA in reversing v-Ki-ras-induced transformation.
• To identify potential tumor suppressor genes involved in regulating cell morphology and tumorigenicity.

Main Methods:

• Transfection of NIH 3T3 cells with a normal human fibroblast cDNA expression library.
• Isolation of morphologically nontransformed (flat) revertant cell lines.
• Analysis of v-Ki-ras expression and p21v-Ki-ras protein levels.
• Cell fusion experiments to create hybrids between revertants and transformed cells.
• Recovery and re-transfection of plasmids from revertant lines.

Main Results:

• Seven flat revertant cell lines were isolated, exhibiting reduced in vivo tumorigenicity.
• Revertants maintained rescuable transforming virus and high expression of v-Ki-ras RNA and p21v-Ki-ras.
• Transformed phenotypes were suppressed in cell hybrids formed by fusing revertants with v-Ki-ras-transformed NIH 3T3 cells.
• Plasmids capable of inducing flat secondary transfectants were recovered from two revertant lines.

Conclusions:

• Transfected cDNAs in revertant cells appear to suppress specific transformed phenotypes.
• This study identifies potential tumor suppressor genes that counteract v-Ki-ras-mediated transformation.
• The findings suggest a genetic basis for the reversal of oncogenic transformation.