Adaptive changes in tumor cells in response to reductive stress

Area of Science:

• Cellular Biology
• Cancer Research
• Biochemistry

Background:

• Reductive stress, an imbalance of cellular electron donors, is implicated in human pathologies like cancer.
• Melanoma cell lines were engineered for resistance to reductive stress agents: rotenone (ROT^R), n-acetyl-L-cysteine (NAC^R), and dithiothreitol (DTT^R).

Purpose of the Study:

• To investigate the cellular adaptations and metabolic shifts in melanoma cells developing resistance to reductive stress.
• To understand the impact of reductive stress resistance on cell morphology, mitochondrial function, and key signaling pathways.

Main Methods:

• Development of resistant melanoma cell lines (ROT^R, NAC^R, DTT^R).
• Analysis of cell morphology, mitochondrial morphology, membrane potential, and respiration.
• Assessment of cellular metabolic flux, including utilization of tricarboxylic acid (TCA) cycle intermediates and ketone bodies.
• Measurement of reactive oxygen species (ROS) levels, nuclear factor erythroid 2-related factor 2 (Nrf2) activation, and unfolded protein response (UPR) expression.

Main Results:

• Resistant cells exhibited faster division and a more reduced intracellular redox state.
• ROT^R cells showed significant mitochondrial alterations (fragmentation, swelling, depolarization) and reduced respiration.
• NAC^R and DTT^R cells utilized TCA cycle intermediates, while ROT^R cells used ketone bodies.
• Resistance correlated with decreased ROS, activated Nrf2/GSTP pathway, and increased UPR signaling.

Conclusions:

• Melanoma cells adapt to lethal reductive stress by altering metabolism and enhancing survival pathways.
• Reductive stress resistance induces distinct mitochondrial and metabolic profiles, with a common trend towards increased UPR.
• These findings highlight tumor cell adaptability to hostile reductive environments, crucial for understanding cancer progression and treatment resistance.