Retroviruses in radiation-induced lymphomas

Area of Science:

• Retroviral genetics
• Molecular virology
• Cancer research

Background:

• Radiation leukemia virus complex (RadLV/VL3) is a thymotropic and leukemogenic entity.
• RadLV/VL3(T+L+) is a recombinant retrovirus with genetic similarities to Akv MuLV and xenotropic MuLV.

Purpose of the Study:

• To analyze the nucleotide sequence of RadLV/VL3(T+L+).
• To investigate the role of enhancer elements in lymphomagenesis.
• To determine if proviral integration and clonal cell selection are indicative of viral induction of leukemogenesis.

Main Methods:

• Nucleotide sequencing of RadLV/VL3(T+L+).
• Analysis of proviral sequences adjacent to the c-myc gene in rat thymic lymphomas.
• In-vitro cell culture to assess growth advantage and clonal selection.

Main Results:

• RadLV/VL3(T+L+) exhibits a recombinant retroviral structure with features from Akv MuLV and xenotropic MuLV.
• Sequence rearrangements in the LTR suggest potential enhancer elements.
• Proviral integration at specific DNA sites can confer an in-vitro growth advantage and lead to clonal cell selection, independent of lymphomagenesis.

Conclusions:

• Clonal appearance of integrated provirus in cultured lymphoma cells does not necessarily imply viral induction of radiation-induced leukemogenesis.
• The observed growth advantage may be a non-specific phenomenon related to proviral integration site.