Pathogenic mitochondrial DNA mutations inhibit melanoma metastasis.

Area of Science:

• Cancer Biology
• Mitochondrial Genetics
• Melanoma Research

Background:

• Mitochondrial DNA (mtDNA) mutations are common in cancers, but their exact role in tumor progression is unclear.
• Understanding mtDNA's influence on cancer growth and metastasis is crucial for developing targeted therapies.

Purpose of the Study:

• To investigate the functional impact of pathogenic mtDNA mutations on melanoma tumor growth, metastasis, and cell circulation.
• To establish isogenic human melanoma cell lines with varying mtDNA functional states.

Main Methods:

• Developed an enhanced cytoplasmic hybrid (cybrid) generation protocol.
• Created isogenic melanoma cybrid lines with wild-type or pathogenic mtDNA, exhibiting varying oxidative phosphorylation function.
• Analyzed tumor growth, spontaneous metastasis, circulating tumor cell abundance, migration, invasion, and organ colonization.

Main Results:

• Melanoma cybrids with pathogenic mtDNA formed tumors despite impaired oxidative phosphorylation.
• Pathogenic mtDNA variants reduced spontaneous metastasis and circulating tumor cells, indicating impaired entry into circulation.
• Organ colonization was not inhibited by pathogenic mtDNA after intravenous injection.
• Single-cell analyses showed selection against pathogenic mtDNA during tumor growth in heteroplasmic lines.

Conclusions:

• Functional mtDNA is favored during melanoma growth.
• Mitochondrial dysfunction due to mtDNA mutations impairs metastatic entry into the bloodstream.
• Pathogenic mtDNA is selected against during melanoma progression, highlighting the importance of functional mitochondria for cancer dissemination.