Insertional hypermutation in mineral oil-induced plasmacytomas

Area of Science:

• Oncology
• Virology
• Genetics

Background:

• Plasma cell tumors are rare in young BALB/c mice without chronic inflammatory stimulation.
• Chronic inflammation's role in promoting mutagenesis and tumor development is not fully understood.

Purpose of the Study:

• To investigate the mechanisms by which inflammatory tissues promote mutagenesis.
• To elucidate the nature of mutagenesis in the context of inflammation-induced tumors.

Main Methods:

• Induction of plasmacytomas in BALB/c mice using mineral oil.
• Analysis of endogenous retroelement production in tumors.
• Identification and quantification of de novo retroelement insertions in tumor genomes.

Main Results:

• Mineral oil-induced plasmacytomas produce significant amounts of endogenous retroelements, including murine leukemia virus and intracisternal A particles.
• Up to ten de novo retroelement insertions were identified per plasmacytoma, frequently in genes associated with common retroviral integration sites.
• Tumor evolution in cell culture showed additional retroelement integrations, particularly into cancer genes.

Conclusions:

• Endogenous retroelements, activated by inflammation, play a significant role in the de novo insertion mutagenesis driving plasmacytoma formation.
• These retroelement insertions are coresponsible for both the initiation and progression of plasma cell tumors in BALB/c mice.