PD-1 and PD-L1 expression in bone and soft tissue sarcomas

Area of Science:

• Oncology
• Immunology
• Cancer Research

Background:

• Programmed cell death protein 1 (PD-1) and its ligands are crucial in tumor immune evasion.
• Anti-PD-1 inhibitors are approved for several cancers, but their role in bone and soft tissue sarcomas is understudied.
• Expression of PD-1 and PD-L1 in various sarcoma subtypes needs further investigation.

Purpose of the Study:

• To evaluate the expression of PD-1 and its ligand PD-L1 in malignant bone and soft tissue sarcomas.
• To compare PD-1 and PD-L1 expression in sarcomas with normal tissues and benign counterparts.
• To assess PD-1 and PD-L1 protein levels in sarcoma cell lines.

Main Methods:

• Tissue microarrays of liposarcomas, rhabdomyosarcomas, osteosarcomas, and chondrosarcomas were stained for PD-1 and PD-L1.
• Normal adipose tissue, skeletal muscle, bone, osteochondroma, and lipoma served as controls.
• Western blot analysis was performed on four sarcoma cell lines.

Main Results:

• Osteosarcomas, chondrosarcomas, liposarcomas, and rhabdomyosarcomas overexpressed PD-1 compared to normal tissues.
• PD-1 expression in rhabdomyosarcomas correlated with higher tumor stage.
• PD-L1 expression was rare, found only in a few specific sarcoma subtypes; normal tissues were negative.

Conclusions:

• Bone and soft tissue sarcomas exhibit significant cytoplasmic PD-1 expression.
• PD-L1 expression is minimal to absent in these sarcomas.
• The limited PD-L1 expression raises questions about the efficacy of current PD-1/PD-L1 targeted immunotherapies for these malignancies.