Structural Maintenance of Chromosomes 5/6 complex dysfunction enables tumor mutagenesis.

Area of Science:

• Genomics
• Cancer Biology
• Molecular Oncology

Background:

• The Structural Maintenance of Chromosomes (SMC) 5/6 complex is vital for genome stability, but its role in cancer remains unclear.
• SMC5/6 dysfunction causes genome instability, yet its somatic inactivation in cancer is understudied.

Purpose of the Study:

• To investigate the prevalence and consequences of SMC5/6 gene dysfunction in human cancers.
• To analyze the association between SMC5/6 alterations and tumor mutational burden (TMB), patient survival, and immunotherapy response.

Main Methods:

• Pan-cancer analysis of SMC5/6 alterations (copy number and small variants) across three large tumor databases.
• Correlation analysis between SMC5/6 variants, TMB, and patient survival outcomes.
• Assessment of immunotherapy response in a colorectal cancer cohort with SMC5/6 variants.

Main Results:

• Thousands of tumors across all tissue types showed copy number alterations or small variants in SMC5/6 genes.
• Deleterious SMC5/6 variants, not copy number changes, correlated with elevated TMB, driven by POLE dysfunction and MMRd.
• Patients with SMC5/6 variants had improved survival, partly due to enhanced response to immunotherapy in colorectal cancer.

Conclusions:

• SMC5/6 gene dysfunction is a predictive biomarker for elevated TMB and immunotherapy susceptibility.
• SMC5/6 status should be considered in cancer diagnostics for prognostic insights and personalized treatment strategies.