Uncoupling TORC2 from AGC kinases inhibits tumour growth

Area of Science:

• Biochemistry
• Cell Biology
• Oncology

Background:

• Mammalian target of rapamycin (mTOR) controls cell growth and metabolism through two complexes: mTORC1 and mTORC2.
• mTORC1 is targetable by rapamycin, but mTORC2's specific inhibition is challenging, limiting research into its roles.
• The mTORC2 subunit Sin1 interacts with AGC kinases like Akt and PKC, crucial for cell signaling.

Purpose of the Study:

• To develop a method for pharmacologically inhibiting mTORC2 independently of mTORC1.
• To investigate the role of mTORC2 in colon cancer growth by disrupting its interaction with AGC kinases.
• To assess the therapeutic potential of targeting mTORC2 in cancer.

Main Methods:

• Developed an inducible dominant-negative system to uncouple mTORC2 from its AGC kinase substrates.
• Utilized Sin1 mutants that bind mTORC2 but fail to recruit Akt and PKC.
• Administered the system to DLD1 colon cancer cells and xenograft tumors in vivo.
• Employed time-resolved two-site amplified FRET (A-FRET) to quantify mTORC2 uncoupling from Akt.

Main Results:

• Disrupting the Sin1-AGC kinase interaction inhibited Akt activation in DLD1 colon cancer cells.
• The developed system effectively blocked tumor growth in vivo.
• A-FRET analysis confirmed that the extent of tumor growth inhibition correlated with the degree of mTORC2 uncoupling from Akt.
• These findings demonstrate the specific inhibition of mTORC2's role in tumor progression.

Conclusions:

• mTORC2 is a critical regulator of colon cancer cell growth and tumor progression.
• The novel inducible system allows for specific pharmacological inhibition of mTORC2.
• Targeting mTORC2, independent of mTORC1, represents a promising therapeutic strategy for cancer treatment.