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Published on: August 16, 2024
Single-Cell RNA Sequencing Reveals Cellular Heterogeneity in an Acral Amelanotic Melanoma After Immunotherapy
Le Zhuang1,2,3,4,5,6, Jie Tian1,2,3,4,7, Binbin Lai1,2,3,4,7
1Department of Dermatology, Peking University First Hospital, Beijing, People's Republic of China.
Background:
Anti-programmed cell death ligand-1 (anti-PD-L1) immunotherapy is often used for advanced urothelial carcinoma and melanoma, including amelanotic melanoma, a relatively rare subtype with little to no pigment in the tumor cells. However, cellular heterogeneity of amelanotic melanoma during or after anti-PD-L1 immunotherapy treatments has not been described.
Purpose:
To investigate cellular heterogeneity in acral amelanotic melanoma after immunotherapy exposure.
Methods:
We evaluated subtle visual changes of the melanoma by dermoscopy and performed a pathological examination to analyze the heterogeneity of microscopic morphological and immunohistochemistry changes. The cellular transcriptional heterogeneity and corresponding biological function profiles of the melanoma were determined by single-cell RNA sequencing (scRNA-seq).
Results:
The dermoscopic examination revealed black globules and scar-like depigmentation areas against a homogeneous red background. Pigmented and amelanotic melanoma cells were observed microscopically. The pigmented cells were large and contained melanin granules expressing Melan-A and HMB45; the amelanotic cells were small and did not express HMB45. Ki-67 immunohistochemical staining revealed that the pigmented melanoma cells had a higher proliferative ability than the amelanotic cells. scRNA-seq identified three cell clusters: amelanotic cell cluster 1, amelanotic cell cluster 2, and pigmented cell cluster. Furthermore, a pseudo-time trajectory analysis showed that amelanotic cell cluster 2 originated from amelanotic cell cluster 1 and transformed into the pigmented melanoma cell cluster. The expression pattern of melanin synthesis-related and lysosome-endosome-related genes in different cell clusters supported the cell cluster transformation results. Also, upregulated expression of cell cycle genes indicated that the pigmented melanoma cells had a high proliferative ability.
Conclusion:
Coexisting amelanotic and pigmented melanoma cells indicated cellular heterogeneity in an acral amelanotic melanoma from a patient who underwent immunotherapy treatment. Additionally, the pigmented melanoma cells acquired a higher proliferative ability than the amelanotic melanoma cells.
Insights
This study reveals cellular heterogeneity in amelanotic melanoma after anti-programmed cell death ligand-1 (anti-PD-L1) immunotherapy. Pigmented melanoma cells showed increased proliferation compared to amelanotic cells, indicating treatment-induced changes.
Area of Science:
- Oncology
- Dermatology
- Immunotherapy
Background:
- Anti-programmed cell death ligand-1 (anti-PD-L1) immunotherapy is a standard treatment for advanced urothelial carcinoma and melanoma.
- Amelanotic melanoma, a rare subtype lacking pigment, presents unique challenges in treatment response assessment.
- Cellular heterogeneity in amelanotic melanoma following anti-PD-L1 therapy remains underexplored.
Purpose of the Study:
- To investigate the cellular heterogeneity of acral amelanotic melanoma after exposure to anti-PD-L1 immunotherapy.
- To characterize microscopic and molecular changes indicative of cellular diversity post-treatment.
Main Methods:
- Dermoscopic and pathological examinations were used to assess morphological changes and immunohistochemistry.
- Single-cell RNA sequencing (scRNA-seq) was employed to determine cellular transcriptional heterogeneity and functional profiles.
- Pseudo-time trajectory analysis was conducted to infer cell differentiation pathways.
Main Results:
- Microscopic analysis revealed coexisting pigmented and amelanotic melanoma cells.
- scRNA-seq identified distinct cell clusters and a developmental trajectory from amelanotic to pigmented cells.
- Pigmented melanoma cells exhibited higher proliferative capacity (Ki-67) and upregulated cell cycle genes compared to amelanotic cells.
Conclusions:
- Immunotherapy can induce cellular heterogeneity in amelanotic melanoma, characterized by the emergence of pigmented cells.
- Pigmented melanoma cells arising post-treatment demonstrate enhanced proliferative potential.
- These findings highlight the dynamic cellular responses to anti-PD-L1 therapy in amelanotic melanoma.
