Exploring the impact of GSTM1 as a novel molecular determinant of survival in head and neck cancer patients of African descent.

Background: Blacks/African American (BAA) patients diagnosed with head and neck squamous cell carcinoma (HNSCC) have worse survival outcomes than White patients. However, the mechanisms underlying racial disparities in HNSCC have not been thoroughly characterized.

Methods: Data on gene expression, copy number variants (CNVs), gene mutations, and methylation were obtained from 6 head and neck cancer datasets. Comparative bioinformatics analysis of the above genomic features was performed between BAAs and Whites. The expression pattern of GSTM1 was validated by immunohistochemistry using tumor tissue microarray (TMA). Effect of GSTM1 knockdown were assessed by cell proliferation, colony formation, and tumor development in an orthotopic mouse model. The changes in protein kinases were determined using the Proteome Profiler Human Phospho-Kinase Array Kit in HNSCC cells with or without GSTM1 knockdown.

Results: We identified ancestry-related differential genomic profiles in HNSCC. Specifically, in BAA HNSCC, FAT1 mutations were associated with its gene expression, SALL3 gene expression correlated with its gene CNVs, and RTP4 gene expression showed an inverse correlation with its methylation. Notably, GSTM1 emerged as a prognostic risk factor for BAA HNSCC, with high gene CNVs and expression levels correlating with poor overall survival in BAA patients. Immunohistochemistry results from newly developed in-house TMA validated the expression pattern of GSTM1 between BAA HNSCC and White HNSCC. In an orthotopic mouse model, GSTM1 knockdown significantly inhibited malignant progression in tumors derived from BAAs. In contrast, loss of GSTM1 did not affect the development of HNSCC originating in Whites. Mechanistically, GSTM1 knockdown suppressed HSP27 phosphorylation and β-catenin in BAA HNSCC cells, but not in White HNSCC cells. This differential effect at least partially contributes to tumor development in BAA patients.

Conclusion: This study identifies GSTM1 as a novel molecular determinant of survival in HNSCC patients of African descent. It also provides a molecular basis for future research focused on identifying molecular determinants and developing therapeutic interventions to improve outcomes for BAA patients with HNSCC.