Growth-factor dependent expression of the translationally controlled tumour protein TCTP is regulated through the...

Area of Science:

• Molecular Biology
• Cancer Research
• Cell Signaling

Background:

• Translationally controlled tumor protein (TCTP) is a cyto-protective protein linked to poor cancer outcomes.
• High TCTP levels are frequently observed in cancer cells, but the underlying regulatory mechanisms are not fully understood.
• TCTP mRNA possesses a 5'-terminal oligopyrimidine tract (5'-TOP), suggesting translational control.

Purpose of the Study:

• To elucidate the signaling pathways governing TCTP mRNA translation.
• To understand how TCTP levels are mechanistically elevated in cancer cells.

Main Methods:

• Utilized HT29 colon cancer and HeLa cells to study TCTP expression.
• Employed polysome profiling and mRNA quantification to assess translational control.
• Investigated the role of the PI3-K/Akt/mTORC1 pathway using inhibitors (rapamycin, Akt inhibitors) and genetic manipulation (TSC2 knockout, eIF4E, 4E-BP1 mutants).

Main Results:

• Serum stimulation increased TCTP expression in HT29 and HeLa cells, an effect inhibited by rapamycin and Akt inhibitors, indicating mTORC1 pathway involvement.
• Polysome profiling confirmed that serum-induced TCTP expression changes occur at the translational level.
• The PI3-K/Akt/mTORC1 pathway directly regulates TCTP mRNA translation, with mTORC1 hyperactivity in ~80% of tumors potentially explaining elevated TCTP levels.

Conclusions:

• TCTP mRNA translation is under the control of the PI3-K/Akt/mTORC1 signaling cascade.
• Hyperactive mTORC1 signaling in cancer contributes to increased TCTP levels, correlating with poor patient prognosis.
• Understanding this regulatory axis provides insights into cancer progression and potential therapeutic targets.