mLST8 Promotes mTOR-Mediated Tumor Progression

Area of Science:

• Oncology
• Molecular Biology
• Biochemistry

Background:

• Mechanistic target of rapamycin (mTOR) pathway hyperactivity is observed in many human cancers, contributing to tumor progression.
• The precise molecular mechanisms driving mTOR upregulation in cancer remain incompletely understood.

Purpose of the Study:

• To investigate the role of mLST8, a key subunit of mTOR complexes, in cancer development.
• To elucidate the functional impact of mLST8 expression levels on mTOR pathway activity and tumor cell behavior.

Main Methods:

• Examined mLST8 expression in human cancer cell lines and tissues.
• Utilized knockdown and overexpression techniques to assess mLST8 function.
• Analyzed mTORC1 and mTORC2 complex formation and downstream signaling (AKT, 4E-BP1 phosphorylation).

Main Results:

• mLST8 expression was elevated in colon and prostate cancer cells and tissues.
• mLST8 knockdown impaired mTORC1/mTORC2 complex assembly and suppressed tumor cell growth and invasion.
• mLST8 overexpression promoted anchorage-independent growth in normal cells, while knockdown did not affect normal cell growth.
• mLST8 knockdown differentially affected mTOR signaling: reduced AKT phosphorylation in all cells, but inhibited 4E-BP1 phosphorylation specifically in cancer cells.

Conclusions:

• mLST8 exhibits distinct roles in normal versus cancer cells, influenced by its expression level.
• Upregulated mLST8 contributes to tumorigenesis by constitutively activating both mTORC1 and mTORC2 pathways.
• mLST8 represents a potential therapeutic target for cancers with elevated mTOR activity.