PEPCK-M recoups tumor cell anabolic potential in a PKC-ζ-dependent manner

Area of Science:

• Cancer Biology
• Metabolic Regulation
• Cellular Stress Response

Background:

• Mitochondrial phosphoenolpyruvate carboxykinase (PEPCK-M; PCK2) is present in all cancer types and neuroprogenitor cells.
• PEPCK-M is upregulated by amino acid limitation and ER-stress via ATF4, influencing PEP/Ca2+ signaling and metabolic adaptation for survival.
• Its precise role in cancer metabolism and pro-survival mechanisms requires further elucidation.

Purpose of the Study:

• To investigate the role of PEPCK-M in cancer cell metabolism and survival under nutrient stress.
• To elucidate the mechanisms by which PEPCK-M contributes to cancer cell adaptation and evasion.
• To assess the impact of PEPCK-M modulation on tumor growth in vitro and in vivo.

Main Methods:

• Quantitative analysis of [U-13C]glutamine and [U-13C]glucose labeling in glycolytic and TCA cycle intermediates using LC/MS and GC/MS.
• Assessment of cell viability under varying glucose concentrations and in vivo xenografts.
• Loss-of-function (shRNA) and gain-of-function (overexpression) studies in HeLa cervix carcinoma cells.

Main Results:

• PEPCK-M levels correlated with [U-13C]glutamine labeling in metabolic intermediates under nutritional stress, impacting serine, glycine, and proline metabolism.
• Cell viability defects due to PEPCK-M silencing were rescued by supplementing with specific amino acids.
• PEPCK-M inhibition in abundant glucose led to TCA cycle blockade, increased ROS, and limited growth; its absence abolished the survival advantage conferred by PKC-ζ downregulation.
• PEPCK-M loss impaired anchorage-independent colony formation and xenograft growth.

Conclusions:

• PEPCK-M plays a role in regulating proteostasis during tumor growth under anabolic and stalling conditions.
• PEPCK-M contributes to cancer cell evasion mechanisms in nutrient-stressed environments.
• These findings offer molecular insights into the clinical relevance of PEPCK-M in cancer therapy.