Oncogenic HPV infection interrupts the expression of tumor-suppressive miR-34a through viral oncoprotein E6

Area of Science:

• Oncology
• Virology
• Molecular Biology

Background:

• MicroRNAs (miRNAs) are crucial regulators of cell proliferation and differentiation.
• Aberrant miRNA expression is increasingly recognized as a mechanism in human carcinogenesis.
• The causes of altered miRNA expression, particularly in virus-associated cancers, are not fully understood.

Purpose of the Study:

• To investigate the role of oncogenic human papillomaviruses (HPVs) in regulating cellular miRNA expression in cervical cancer.
• To elucidate the mechanism by which HPV affects the expression of tumor-suppressive miRNAs.
• To determine the impact of miR-34a modulation on cancer cell behavior.

Main Methods:

• Analysis of miR-34a expression in cervical cancer tissues and HPV-containing cell lines.
• Investigating the effect of HPV E6 protein on p53 and miR-34a levels.
• Utilizing siRNA to knockdown viral E6 expression and observing changes in p53 and miR-34a.
• Assessing the impact of ectopic miR-34a expression on cell growth and apoptosis.

Main Results:

• Cervical cancer tissues and cell lines with oncogenic HPVs showed reduced expression of tumor-suppressive miR-34a.
• HPV E6 protein destabilizes p53, a miR-34a transactivator, leading to decreased miR-34a levels.
• Knockdown of HPV E6 increased p53 and miR-34a expression, with miR-34a accumulating in G(0)/G(1) phase cells.
• Ectopic miR-34a expression induced cell growth retardation and apoptosis.

Conclusions:

• This study demonstrates for the first time that a viral oncoprotein can regulate cellular miRNA expression.
• High-risk HPVs contribute to cervical cancer development by downregulating miR-34a expression via the E6/p53 pathway.
• These findings offer new insights into the molecular mechanisms of HPV-induced carcinogenesis.