HLA-G expression by tumors

Area of Science:

• Immunology
• Molecular Biology
• Oncology

Background:

• The non-classical MHC class I antigen, HLA-G, is expressed by trophoblast cells.
• HLA-G is proposed to mediate immune evasion by the placenta from maternal uterine NK cells.
• A similar mechanism is hypothesized for tumor cells escaping immunosurveillance.

Purpose of the Study:

• To investigate the expression of HLA-G in various tumor types and cell lines.
• To determine if HLA-G expression by tumor cells contributes to immune evasion.
• To resolve conflicting data on HLA-G expression in tumors.

Main Methods:

• Immunohistology on tumor tissue sections.
• Flow cytometry and RT-PCR on tumor cell lines.
• Analysis of NK cell infiltration in tumor deposits.

Main Results:

• No detectable HLA-G protein expression was found in any tumors or cell lines examined.
• Very faint HLA-G mRNA bands were detected in three cell lines (hepG2, Mead, CaSki) by RT-PCR.
• Tumor deposits were generally not infiltrated by NK cells.

Conclusions:

• The study's findings do not support the hypothesis that tumor cells express HLA-G to evade NK cell-mediated lysis.
• The proposed immune evasion mechanism involving HLA-G in tumors appears unlikely based on these results.