Annually, China reports over four million new cancer cases, with lung cancer comprising 24.6% and being the deadliest in terms of mortality1. Lung adenocarcinoma (LAC), which constitutes approximately 30-35% of all lung cancer cases, is characterized by a markedly high incidence of KRAS mutations, with nearly 100% of cases exhibiting such genetic alterations2. Despite KRAS’s reputation as “undruggable,” the Food and Drug Administration (FDA) has approved two KRASG12C inhibitors, sotorasib and adagrasib, for advanced NSCLC with the KRASG12C mutation3,4. However, the CodeBreaK 200 phase III trial's progression-free survival (PFS) for sotolacib, the first FDA-approved KRASG12C inhibitor, was less than anticipated5. Current investigations have elucidated multiple resistance mechanisms to KRASG12C inhibitors, including secondary mutations, reactivation of the bypass signalling pathway, acquired KRAS alterations, and the epithelial–mesenchymal transition6-9. Other potential mechanisms, such as other epigenetic mechanisms, gut microbiota, and immune destruction factors, remain to be investigated10-12.
Single-cell technologies have completely changed how we investigate the progression of tumours and medication resistance13, enabling the establishment of detailed immune profiles in cancers14,15. Longitudinal tumour sampling facilitates investigation of temporal response dynamics, offering insights into tumour heterogeneity, evolution, and development of acquired resistance16. Recently, our longitudinal study on Chinese NSCLC patients receiving anti-PD1 therapy, with over 30 months of follow-up, revealed that specific CD8+ subpopulations correlate significantly with anti-PD-1 therapy17. This finding inspired us to develop a robust strategy for utilizing noninvasive biopsies, and it is necessary to apply novel high-dimensional and single-cell technologies to explore the reason for sotorasib resistance. Sotorasib is currently first being launched into the Chinese market in the Macau special administrative region, and this is the first clinical case report of sotorasib resistance in China. In this work, we used single-cell RNA-sequencing (scRNA-seq) technology to characterize the cellular and molecular dynamics of immune cells in one patient with NSCLC treated with sotorasib by following longitudinal sampling over a period of 5 months to gain insights into the changes in the immune cell population and their gene expression profiles over time. We sought to uncover the mechanisms behind resistance and sensitivity to targeted inhibitor therapies in NSCLC, identify immune cell subtypes that react to sotorasib, and address its treatment limitations.
To elucidate development of resistance to sotorasib, we assembled a distinctive dataset derived from 4 peripheral blood samples collected longitudinally over 5 months; to date, this is the longest follow-up time of patients who receive sotorasib treatment in China. This dataset chronicles a patient's transition from a favourable initial response to sotorasib to disease progression and death (Fig. 1A). We conducted single-cell RNA sequencing analysis of the cells from these samples. After quality filtering, we obtained single-cell transcriptome data for 30,000 high-quality immune cells, which we classified into 41 distinct clusters (Clusters 0-40) to maximize differentiation of cell populations (Fig. 1B, Supplementary Fig. S1A, B). Following this stratification, we employed SingleR18 for cluster annotation, ultimately identifying 7 major cell types, including T cells (marked by CD3D, CD3E, CD4 and CD8A), natural killer (NK) cells (marked by NKG7), B cells (marked by MS4A1), monocytes (marked by CD14), dendritic cells (DCs) (marked by FCER1A), macrophages (marked by FCGR3A) and megakaryocytes (marked by PPBP) (Fig. 1C). Through marker gene analysis for cell type identification, we detected the presence of megakaryocytes within our samples. Interestingly, the proportions of T cells, NK cells, B cells, and dendritic cells (DCs) increased during the drug response phase and decreased when there was no response (Figure 1D), with declines in T cells and NK cells being the most pronounced (Supplementary Fig. S1C). Monocytes increased in both response and nonresponse cycles. Subsequently, we employed the CellChat19 tool to dissect the intricacies of cell-to-cell communication, and discovered that complex contact among these 7 cell types, especially T cells, showed stronger cell signalling activities with NK and B cells (Fig. 1E, Supplementary Fig. S1D, E). In summary, by employing single-cell RNA sequencing, we delineated the dynamic alterations in immune cell populations across various treatment cycles and demonstrated that when sotorasib resistance emerged, the proportions of T cells and NK cells decreased.
Considering the substantial differences in T cells at different stages, we refined T cells based on expression of canonical genes, resulting in identification of 3 distinct clusters, including stem-like T cells (marked by CD38), CD4+ T cells (marked by CD4), and CD8+ T cells (marked by CD8A) (Supplementary Fig. S2A). Previous research has demonstrated that blood is a crucial pathway for CD8+ T-cell movement between secondary lymphoid organs, primary tumours, and metastases, thus offering an ideal medium for investigating peripheral antitumour responses20,21. Thus, we clustered CD8+ T cells and obtained 10 transcriptionally distinct subclusters: CD8-FGFBP2 (Cluster 0), CD8-TRBC1 (Cluster 1), CD8-RPL2 (Cluster 2), CD8-CMC1 (Cluster 3), CD8-PPBP (Cluster 4), CD8-TRBV3 (Cluster 5), CD8-GNLY (Cluster 6), CD8-GZMB (Cluster 7), CD8-KLRB1 (Cluster 8), and CD8-ACTB (Cluster 9) (Fig. 2A, B). Based on bioinformatic analysis, Clusters 2 and 4 have naive T-cell features, while others are linked to effector and cytotoxic T cells. The CD8+ T-cell developmental trajectory from Slingshot22 indicated that Clusters 2 and 4 are likely starting points, with the cells then diverging. Cluster 8 appears to have evolved from Cluster 2 directly but did not further differentiate (Fig. 2C). Analysis revealed that expression of the KLRB1 gene, specific to Cluster 8, gradually increased during its differentiation from Cluster 2 (Supplementary Fig. S2B). Moreover, after treatment response, we observed a decrease in the percentage of the CD8-KLRB1 cluster in the patient with KRASG12C and an increase in the percentage following treatment nonresponse (Supplementary Fig. S2C). Further investigation indicated that CD8-KLRB1 expression-stimulating cytokine genes, such as IFNG (IFN-γ) and PRF1 (Perforin), are associated with cytotoxicity (Fig. 2D). In addition, the activation marker CD69, which is associated with mucosal-associated invariant T (MAIT) cells12, was found in this cluster (Fig. 2D). However, no T-cell exhaustion marker genes, such as PDCD1 (PD-1) or HAVCR2 (TIM-3), were detected in this cluster (Supplementary Fig. S2D). Moreover, our investigation revealed a notable expression pattern of lung-homing markers, specifically CXCR6 and CCR5, within the CD8-KLRB1 subset (Fig. 2E).
Subsequently, within the CD8-KLRB1 subpopulation, we identified certain genes associated with drug response. Specifically, GNAS and JUND exhibited downregulation during cycles 1 and 2, followed by upregulation in cycle 3. In contrast, S100A8 and S100A9 demonstrated divergent expression patterns (Fig. 2F). To investigate drug-related gene mechanisms, GSEA was used to enrich significantly changed signalling pathways among different cell clusters. The cell adhesion pathway and RAP1 pathway in the CD8-KLRB1 cluster were suppressed (Fig. 2G). Additionally, we employed the single-cell network inference (SCENIC) approach to dissect the regulatory landscape of transcription factors within the CD8+ T-cell compartment23. Active transcription factors in CD8-KLRB1 T cells included JUN, FOS, and JUNB (Supplementary Fig. S2E, F). GO and KEGG enrichment analyses demonstrated that the transcription factors of significance were linked to the biological processes of the MAPK signalling pathway (Supplementary Fig. S2G, H).
Previous studies have shown that lectin-like transcript 1 (LLT1/CLEC2D), the ligand of CD161 (encoded by KLRB1), is expressed on monocyte-derived dendritic cells and on activated B cells24,25. We detected intercellular signalling interactions between CD8-KLRB1 T cells and natural killer (NK) and B cells mediated by the receptor‒ligand pairs involving CLEC2D and KLRB1 (Fig. 2H). Thus, CD8+ CD161hi T cells and B and NK cells promote antitumour effects through the LLT1 signalling pathway.
This study presents the first comprehensive, high-resolution analysis of the peripheral blood immune landscape in patients with the KRASG12C mutation undergoing treatment with sotorasib. By leveraging single-cell technologies, we meticulously characterized the dynamic shifts within circulating PBMCs. Notably, we elucidated the intricate interplay among CD8+CD161hi T cells and diverse immune populations, corroborating progression from naive T cells to a phenotypically distinct effector state after treatment. Moreover, our investigation revealed dynamic alterations in expression of genes associated with the pharmacological action of sotorasib. These findings provide compelling evidence of active engagement of immune effectors in the antitumour response, potentially offering novel biomarkers for monitoring treatment efficacy in real time. Tumour-infiltrating CD8+CD161hi T cells are found in various tumour microenvironments, and their increase correlates with better prognosis26,27. CD161 is recognized as a coinhibitory receptor on natural killer (NK) cells; however, its role in T cells remains less defined26,28. Remarkably, patients with lung cancer show a higher frequency of circulating MAIT cells relative to healthy individuals29. Our investigation provides the first in-depth characterization of the developmental trajectories and transcriptional regulator alterations of CD8+CD161hi T cells within the context of therapeutic intervention.
To robustly ascertain the generalizability of the observed immune response—specifically, the evolutionary dynamics of the CD8+CD161hi T-cell subset—future investigations must include larger patient cohorts with diverse KRAS genotypes. Despite the lower prevalence of KRAS mutations in the Chinese NSCLC patient population relative to their Caucasian counterparts—with an incidence below 30%—the significant annual incidence of new cancer cases in China underscores the critical need to address this genetic aberration30. Thorough molecular profiling in these diverse demographic settings is essential to tailor precision oncology approaches and to enhance the clinical impact of KRASG12C-targeted therapies.