Ultrastructural nucleolar alterations induced by an ametantrone--poly r(A-U) complex

Area of Science:

• Cell Biology
• Molecular Biology
• Cancer Research

Background:

• Nucleoli are crucial for ribosome biogenesis and cellular function.
• Dysregulation of nucleolar structure is observed in various cancers.
• Understanding how chemical agents affect nucleoli is vital for cancer therapy.

Purpose of the Study:

• To investigate the ultrastructural and intranucleolar changes in RT4 bladder cancer cells.
• To determine the effects of ametantrone (AMT) and poly (adenylate-uridylate) (poly r(A-U)) on nucleolar components.
• To elucidate the mechanisms underlying AMT and poly r(A-U) induced nucleolar alterations.

Main Methods:

• RT4 transitional cell bladder carcinoma cells were exposed to AMT, poly r(A-U), or a combination.
• Nucleolar ultrastructure and intranucleolar distribution of rDNA and rRNA were analyzed.
• Changes in nucleolar components (fibrillar center, dense fibrillar component, granular component, interstices) were quantified.

Main Results:

• Both AMT and poly r(A-U) induced nucleolar compaction and segregation.
• AMT/poly r(A-U) combination showed the most significant changes, followed by poly r(A-U) and then AMT.
• Observed changes included decreased fibrillar centers, increased size of remaining centers, chromatin margination, and retention of pre-rRNA/rRNA.

Conclusions:

• Poly r(A-U) and AMT interfere with DNA transcription and rRNA processing.
• These agents inhibit the release of nascent preribosomes from the nucleolus.
• The findings provide insights into the cytotoxic mechanisms of AMT and poly r(A-U) in cancer cells.