A cluster of cooperating tumor-suppressor gene candidates in chromosomal deletions

Area of Science:

• Oncology
• Genetics
• Cancer Biology

Background:

• Large chromosomal deletions are common in cancer genomes, typically explained by a two-hit mechanism for tumor suppressor gene (TSG) inactivation.
• An alternative hypothesis suggests these deletions may result from selective pressure to reduce the activity of multiple genes simultaneously.

Purpose of the Study:

• To investigate the hypothesis that large chromosomal deletions in cancer arise from the need to attenuate multiple genes.
• To explore the role of chromosome 8p deletions in hepatocellular carcinoma (HCC) tumorigenesis.

Main Methods:

• Utilized a murine model of hepatocellular carcinoma (HCC).
• Employed in vivo RNA interference (RNAi) to target mouse orthologs of genes on human 8p22.
• Analyzed human HCC patient data for correlations between gene down-regulation and survival.

Main Results:

• Provided evidence that multiple genes on chromosome 8p cooperatively inhibit tumorigenesis in mice.
• Demonstrated that simultaneous suppression of these genes synergistically promotes tumor growth.
• Found that combined down-regulation of validated 8p TSGs in human HCC patients is associated with poor survival, unlike individual gene down-regulation.

Conclusions:

• Large cancer-associated deletions can create distinct phenotypes compared to single TSG loss.
• These deletions should be considered and studied as unique mutational events.
• The findings suggest a novel mechanism for tumor development driven by the cumulative effect of multiple gene attenuations.