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Updated: Nov 23, 2025
Multiplexed Immunofluorescence Analysis and Quantification of Intratumoral PD-1+ Tim-3+ CD8+ T Cells
Published on: February 8, 2018
Discovery of acquired molecular signature on immune checkpoint inhibitors in paired tumor tissues
Shin Hye Yoo1,2, Jihui Yun3,4, Bhumsuk Keam5,6
1Department of Internal Medicine, Seoul National University Hospital, 101 Daehak-ro, Jongno-gu, Seoul, 110-744, Republic of Korea.
Background:
Immune checkpoint inhibitor (ICI) has an emerging role in several types of cancer. However, the mechanisms of acquired resistance (AR) to ICI have not been elucidated yet. To identify these mechanisms, we analyzed the pre- and post-ICI paired tumor samples in patients with AR.
Methods:
Six patients with renal cell carcinoma, urothelial cell carcinoma, or head and neck cancer, who showed an initial response to ICI followed by progression and had available paired tissue samples, were retrospectively analyzed. Whole exome sequencing, RNA sequencing, and multiplex immunohistochemistry were performed on pre-treatment and resistant tumor samples.
Results:
The median time to AR was 370 days (range, 210 to 739). Increased expression of alternative immune checkpoints including TIM3, LAG3, and PD-1 as well as increased CD8+ tumor-infiltrating lymphocytes were observed in post-treatment tumor than in pre-treatment tumor of a renal cell carcinoma patient. In contrast, CD8+ T cells and immunosuppressive markers were all decreased at AR in another patient with human papillomavirus-positive head and neck squamous cell carcinoma. This patient had an evident APOBEC-associated signature, and the tumor mutation burden increased at AR. Resistant tumor tissue of this patient harbored a missense mutation (E542K) in PIK3CA. No significant aberrations of antigen-presenting machinery or IFN-γ pathway were detected in any patient.
Conclusions:
Our study findings suggest that the observed increase in immunosuppressive markers after ICI might contribute to AR. Moreover, APOBEC-mediated PIK3CA mutagenesis might be an AR mechanism. To validate these mechanisms of AR, further studies with enough sample size are required.
Insights
Acquired resistance (AR) to immune checkpoint inhibitors (ICI) may involve increased immunosuppressive markers or APOBEC-mediated PIK3CA mutations. Further research is needed to confirm these AR mechanisms in cancer treatment.
Area of Science:
- Oncology
- Immunology
- Genetics
Background:
- Immune checkpoint inhibitors (ICIs) are increasingly used in cancer therapy.
- Mechanisms underlying acquired resistance (AR) to ICIs remain largely unknown.
- Understanding AR is crucial for improving cancer treatment outcomes.
Purpose of the Study:
- To investigate the molecular mechanisms of acquired resistance to immune checkpoint inhibitors (ICIs).
- To analyze paired tumor samples from patients who developed AR after initial response to ICI therapy.
Main Methods:
- Retrospective analysis of paired pre-treatment and resistant tumor samples from six patients with renal cell carcinoma, urothelial cell carcinoma, or head and neck cancer.
- Utilized whole exome sequencing, RNA sequencing, and multiplex immunohistochemistry.
Main Results:
- Observed increased expression of alternative immune checkpoints (TIM3, LAG3, PD-1) and CD8+ T cells in one patient's post-treatment sample.
- Noted decreased CD8+ T cells and immunosuppressive markers in another patient with an APOBEC signature and increased tumor mutation burden.
- Identified a PIK3CA (E542K) mutation in the resistant tumor of the latter patient.
Conclusions:
- Increased immunosuppressive markers may contribute to acquired resistance to ICIs.
- APOBEC-mediated PIK3CA mutagenesis is a potential mechanism of AR.
- Further studies with larger sample sizes are required to validate these findings.
