[Genomic profiles and immune microenvironment of olfactory neuroblastoma]

Objective: To investigate the genomic profiles and immune microenvironment of olfactory neuroblastoma (ONB). Methods: Nineteen ONB cases diagnosed in the Beijing Tongren Hospital from May 2018 to October 2022 were divided into low-grade and high-grade groups according to the Hyams grading system, including 7 low-grade and 12 high-grade ONB. Whole exome sequencing and multiplex immunofluorescence analyses were performed on tissue samples of these ONB. Results: A total of 929 nonsynonymous alterations were identified in 18 of the 19 ONB (18/19) cases. The most commonly altered cancer-related genes were CTNNB1 (3/19) and ZNRF3 (3/19). The most mutated oncogenic pathways were the WNT and RAS pathways. The median tumor mutation burden (TMB) was 0.45/Mb, ranging from 0 to 3.25. The median tumor neoantigen load (TNB) was 9.39 neoantigens/Mb, ranging from 0 to 38.30. The median allelic mutation tumor heterogeneity (MATH) score was 16.95, ranging from 3.05 to 117.47. Only one of the 19 cases expressed PD-L1 (composite positive score, CPS>1) in the tumor cells. The median percentage of CD8⁺ tumor-infiltrating lymphocyte (TIL) in the tumor region was 1.08%. No significant differences were observed between the low-and high-grade groups for mutant genes, mutant pathways, TMB, TNB, MATH, PD-L1 expression levels, or CD8⁺ TILs percentage(P>0.05). However, the low-grade group showed significantly more CD68⁺ macrophages in both the tumor and total region than the high-grade group. Notably, CD68⁺CD163^- macrophages accounted for an average of 80.52% of CD68⁺ macrophages. Conclusions: CTNNB1 and ZNRF3 are the most commonly altered cancer-related genes. The low expression of PD-L1 and the low percentage of CD8⁺ TIL indicate that ONB might not be sensitive to immunotherapy. The percentage of M1-type macrophages in low-grade ONB is significantly higher than that in high-grade ONB, suggesting that M1-type macrophages may be involved in the progression of ONB from low-grade to high-grade.