Ribosome Royale: A Specialized Secret Agent in the Fight to Detect Cancer

A model of a ribosome in a eukaryotic cell (image by Fvoigtsh, CC BY-SA 3.0)

Inside every living cell are millions of tiny machines called ribosomes that manufacture the proteins critical to normal cell function.  For decades, scientists believed that ribosomes shared a similar protein composition because their role in the cell was too important to tolerate variations or changes.  In recent years, however, evidence that there may be some important differences lurking in the proteins that make up the ribosomal machinery has been accumulating. The differences in these ribosomes are being investigated to aid scientists in diagnosing and treating cancer more effectively.

Prof. Jim Uniacke is a molecular biologist in the Department of Molecular and Cellular Biology with a special interest in the protein make-up of ribosomes and how this is affected by cellular stresses like hypoxia. Hypoxia is a condition where oxygen levels are below normal, and it is a common feature of tumours that have outgrown their blood supply. 

"Some ribosomal proteins act differently and/or are produced in different quantities under certain conditions such as hypoxia. These protein changes have the potential to tell physicians and scientists if tumours have become hypoxic and will subsequently become malignant and resistant to treatment," says Uniacke.

Uniacke and PhD student Andrea Brumwell designed an experiment to investigate differences in ribosomal proteins in non-cancerous cells grown under normal and hypoxic conditions.  They also compared ribosomal proteins in cancer cells from the brain, colon and prostate.  The cells were then analyzed using tandem mass spectrometry to determine the amount and type of ribosomal proteins present. 

Ultimately, the team found that hypoxia led to different variants or “specialized”
 versions of two ribosomal proteins in particular: RPS24 and RPS12.

RPS24 is a protein variant found at increased levels in hypoxic prostate cancer cells. However, there is still a mystery around how exactly this ribosomal protein affects cell function. 

“Without knowing exactly what RSP24 does for the cell, we don’t know if the protein has a function independent of the ribosome and/or to produce specialized ribosomes that aid in hypoxic adaptation," says Uniacke.  However, the increased levels suggest there is potential to use RPS24 as a biomarker to determine if a tumour is present. 

In contrast, researchers have a much stronger inkling of the role of RPS12 in the hypoxic tumour environment,  and it is a role that makes this protein of particular interest to Uniacke and his colleagues.

“We think that RPS12 helps cells synthesize more proteins to avoid cell death.  This lack of ‘programmed’ or normal cell death is a hallmark of cancerous tumours where cells live much longer than usual and grow uncontrollably,” explains Uniacke.  One application of this research is the potential development of therapeutic treatments that reduce the synthesis of RPS12 and hence its role in preventing cell death.

"With this type of research, we can figure out how specialized ribosomes help hypoxic cancer cells become dangerous," he adds.  

Uniacke and his team hope that by publishing their results, scientists around the globe can use their research to aid in the development of improved diagnostics and therapeutics for what remains one of modern medicine’s greatest challenges: defeating cancer.

Undergraduate researchers Leslie Fell and Lindsay Obess also contributed to this study.  Funding was provided by the Natural Sciences and Engineering Research Council.

Read the full study in the journal RNA Journal.

Read about other CBS Research Highlights.