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Updated: Feb 10, 2026
Generation and Expansion of Primary, Malignant Pleural Mesothelioma Tumor Lines
Published on: April 21, 2022
Four immunohistochemical assays to measure the PD-L1 expression in malignant pleural mesothelioma
Takuya Watanabe1, Katsuhiro Okuda1, Takayuki Murase2
1Department of Oncology, Immunology and Surgery, Nagoya City University Graduate School of Medical Sciences, Mizuho-cho, Mizuho-ku, Nagoya 467-8601, Japan.
Abstract:
Immune checkpoint inhibitors (ICIs) targeting the PD-1/PD-L1 pathway are expected to be a novel therapy for combating future increases in numbers of malignant pleural mesothelioma (MPM) patients. However, the PD-L1 expression, which is a predictor of the response to ICIs, is unclear in MPM. We studied the PD-L1 expression using four immunohistochemical assays (SP142, SP263, 28-8 and 22C3) in 32 MPM patients. The PD-L1 expression in tumor cells and immune cells was evaluated to clarify the rate of PD-L1 expression and the concordance among the four assays in MPM. The positivity rate of PD-L1 expression was 53.1% for SP142, 28.1% for SP263, 53.1% for 28-8, and 56.3% for 22C3. Nine cases were positive and 10 were negative for all assays. Discordance among the four assays was found in 13 cases. The concordance rates between SP142 and 22C3 and between 28-8 and 22C3 were the highest (84.4%). The concordance rates between SP263 and the other three assays were low (71.9% to 75.0%). The PD-L1 expression in MPM was almost equivalent for three of the assays. Given the cut-off values set in our study, these findings suggested that these assays, except for SP263, can be used for accurate PD-L1 immunostaining in MPM.
Insights
Immune checkpoint inhibitors show promise for malignant pleural mesothelioma (MPM). PD-L1 expression assays varied, with SP142, 28-8, and 22C3 showing higher concordance for predicting treatment response.
Area of Science:
- Oncology
- Immunology
- Pathology
Background:
- Malignant pleural mesothelioma (MPM) is an aggressive cancer with limited treatment options.
- Immune checkpoint inhibitors (ICIs) targeting the PD-1/PD-L1 pathway represent a potential novel therapy for MPM.
- Accurate assessment of PD-L1 expression is crucial for predicting ICI response in MPM patients.
Purpose of the Study:
- To evaluate PD-L1 expression in MPM using four different immunohistochemical assays.
- To determine the positivity rates and concordance among SP142, SP263, 28-8, and 22C3 assays.
- To identify reliable assays for PD-L1 immunostaining in MPM for guiding ICI therapy.
Main Methods:
- Analysis of PD-L1 expression in tumor and immune cells from 32 MPM patients.
- Utilized four distinct immunohistochemical assays: SP142, SP263, 28-8, and 22C3.
- Evaluated PD-L1 positivity rates and inter-assay concordance.
Main Results:
- PD-L1 positivity rates were 53.1% (SP142), 28.1% (SP263), 53.1% (28-8), and 56.3% (22C3).
- High concordance was observed between SP142/22C3 and 28-8/22C3 assays (84.4%).
- The SP263 assay showed lower concordance with the other three assays.
Conclusions:
- Three of the four PD-L1 assays (SP142, 28-8, 22C3) demonstrated comparable results in MPM.
- These assays, excluding SP263, are suitable for accurate PD-L1 immunostaining in MPM.
- Standardized PD-L1 assessment is essential for optimizing ICI therapy in MPM patients.
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