Oncogenic H-ras stimulates tumor angiogenesis by two distinct pathways

Area of Science:

• Oncology
• Molecular Biology
• Cell Biology

Background:

• Tumor progression from a quiescent to an invasive state involves acquiring angiogenic properties.
• The precise mechanisms underlying this phenotypic shift, known as the angiogenic switch, remain largely unknown.
• This switch is thought to involve alterations in the balance between pro-angiogenic and anti-angiogenic factors.

Purpose of the Study:

• To investigate the role of activated H-ras in initiating the angiogenic switch in endothelial cells.
• To elucidate the molecular pathways through which activated H-ras promotes tumor angiogenesis.
• To explore the relationship between activated H-ras, angiogenesis, and tumor dormancy.

Main Methods:

• Introduction of activated H-ras into immortalized endothelial cells.
• Analysis of vascular endothelial growth factor (VEGF) and matrix metalloproteinase (MMP) expression and activity.
• Assessment of tissue inhibitor of metalloproteinase (TIMP) levels.
• Inhibition of phosphatidylinositol-3-kinase (PI3K) to study its role in H-ras-mediated angiogenesis.
• Investigation of tumor dormancy models.

Main Results:

• Activated H-ras expression induced the angiogenic switch in endothelial cells.
• Angiogenic switching was associated with increased VEGF and MMP bioactivity.
• Downregulation of tissue inhibitor of metalloproteinase was observed.
• Inhibition of PI3K partially blocked tumor angiogenesis, indicating dual pathways for H-ras activation.
• Evidence for two distinct forms of tumor dormancy was found.

Conclusions:

• Activated H-ras is a key driver of the angiogenic switch, promoting tumor invasion.
• Tumor angiogenesis activated by H-ras operates through at least two distinct molecular pathways, including PI3K.
• The study provides insights into the molecular basis of tumor angiogenesis and dormancy, with implications for cancer therapy.