Single-cell sequencing to elucidate the disparities in the immune microenvironment between PIK3CA mutants and wild types.

Abstract

e17524 Background: In patients with cervical cancer, PIK3CA exhibits the highest mutation rate, with the predominant oncogenic alteration reported to occur in 40% of cases. Recent studies in cervical cancer have indicated that the mutation status of PIK3CA is prominently associated with a diminished overall survival. Nevertheless, in our preceding study entitled 'Efficacy and Safety of Sintilimab Plus Anlotinib for PD-L1–Positive Recurrent or Metastatic Cervical Cancer: A Multicenter, Single-Arm, Prospective Phase II Trial', the prognosis for the mutant group surpassed that of the non-mutant group. Therefore, distinguishing the differences in the immune microenvironment between PIK3CA mutant and wild-type cervical cancer patients is of great significance. Methods: We used Single-cell RNA sequencing (scRNA-seq) to analyze the tissue samples of 7 cervical cancer patients with PIK3CA mutations and 9 with wild-type. Results: We partitioned cells from both the mutated and wild-type forms of cervical cancer into nine distinct clusters. To better understand the transcriptional heterogeneity of tumor-infiltrating T lymphocytes, we re-clustered 45,574 NK/T cells into 9 clusters. A specific cell cluster, designated as CD8+ ISG15, exhibited a significant enrichment in interferon-induced genes, including ISG15, IFIT3, IFIT1, RSAD2, and IFI6. To explore intergroup differences, we performed differential analysis on the proportions of mutations and non-mutations in different subgroups. We found significant differences in CD8+ ISG15 between the mutant group and the widegroup. ISG15 plays a pivotal role in antiviral responses, and as research advances, it has been identified as a potential prognostic biomarker and therapeutic target for cancer, beyond its antiviral function. A growing body of studies indicates that ISG15 is overexpressed in the majority of tumors, however, the influence of high ISG15 expression on the overall survival of cancer patients is dependent on the cancer type. In our single-cell analysis of cervical cancer, we observed that the CD8+ ISG15 subgroup specifically expresses ISG15, and the prevalence of this subgroup is significantly greater in the PIK3CA wild-type group compared to the mutant group. Consequently, the CD8+ ISG15 subgroup is perceived as a significant subset within the cervical cancer immune microenvironment for regulating anti-tumor responses. Conclusions: We defined the CD8+ ISG15 cell cluster present in the cervical cancer immune microenvironment using scRNA-seq, and found that its proportion is significantly lower in the PIK3CA mutant group than in the wild-type group. Combined with existing research, this suggests that this subgroup plays an important role in immune regulation within the cervical cancer immune microenvironment.