Merkel cell carcinoma showing regression after biopsy: Evaluation of programmed cell death 1-positive cells
Noriki Fujimoto1, Gen Nakanishi, Miho Kabuto
1Department of Dermatology, Shiga University of Medical Science, Shiga, Japan.
Abstract:
We present a cases of Merkel cell carcinoma (MCC) with Merkel cell polyomavirus that showed complete regression after biopsy. The exact mechanism of regression in MCC has remained unclear. It has been reported that apoptosis caused by T-cell immunity was implicated in the regression, and programmed cell death 1 (PD-1), an inhibitory receptor, was expressed in approximately half of tumor-infiltrating T cells in MCC. However, the contribution of PD-1-positive cells for the regression of MCC has not been evaluated. We examined the rate of PD-1-positive cells among the peritumoral mononuclear cells, which showed that the percentage of PD-1-positive cells in the case was significantly lower compared with in MCC without regression. We propose that PD-1-positive cells suppress tumor immunity for MCC, and that reduction of PD-1-positive cells may be associated with tumor regression.
Insights
Merkel cell carcinoma (MCC) regression after biopsy may involve reduced programmed cell death 1 (PD-1) positive cells. Lower PD-1 cell percentages in surrounding tissue suggest a role in suppressing tumor immunity for MCC.
Area of Science:
- Immunology
- Oncology
- Dermatology
Background:
- Merkel cell carcinoma (MCC) is an aggressive skin cancer.
- Complete tumor regression after biopsy is observed but poorly understood.
- T-cell mediated apoptosis is a proposed mechanism for MCC regression.
Observation:
- Programmed cell death 1 (PD-1) is expressed on tumor-infiltrating T cells in MCC.
- The role of PD-1-positive cells in MCC regression remains unevaluated.
- A case of MCC with Merkel cell polyomavirus showed complete regression post-biopsy.
Findings:
- The percentage of PD-1-positive cells among peritumoral mononuclear cells was significantly lower in the regressed MCC case compared to MCC without regression.
- This suggests a potential inverse correlation between PD-1-positive cell infiltration and MCC regression.
Implications:
- PD-1-positive cells may suppress anti-tumor immunity in MCC.
- A reduction in PD-1-positive cells could be associated with spontaneous or biopsy-induced tumor regression in MCC.
- Further research is warranted to explore the therapeutic potential of modulating PD-1 pathways in MCC.
