Primary human tumor cells expressing CD155 impair tumor targeting by down-regulating DNAM-1 on NK cells

Area of Science:

• Immunology
• Cancer Biology
• Cellular Immunology

Background:

• Activating NK cell receptors, such as DNAX accessory molecule-1 (DNAM-1), are vital for tumor immune surveillance.
• DNAM-1 plays a critical role in NK cell recognition of various human tumors, including ovarian carcinoma.

Purpose of the Study:

• To investigate the receptor repertoire and functional status of NK cells in ovarian carcinoma peritoneal effusions.
• To determine how tumor-associated NK cells respond to stimulation and interact with tumor cells.

Main Methods:

• Analysis of NK cell receptor expression (DNAM-1, 2B4, CD16) in tumor-associated vs. peripheral blood NK cells.
• Assessment of NK cell hyporesponsiveness to target cells (K562) and co-stimulation.
• Evaluation of antibody-dependent cellular cytotoxicity (ADCC) against autologous tumor cells.
• Investigation of DNAM-1 expression changes upon coincubation with ovarian carcinoma cells expressing the DNAM-1 ligand (CD155).

Main Results:

• Tumor-associated NK cells exhibited reduced expression of DNAM-1, 2B4, and CD16 compared to autologous peripheral blood NK cells.
• These tumor-associated NK cells were hyporesponsive to HLA class I-deficient K562 cells and coactivation via DNAM-1 and 2B4.
• NK cells showed refractoriness to CD16 stimulation, leading to diminished ADCC against autologous tumor cells.
• Exposure to ovarian carcinoma cells expressing CD155 reduced DNAM-1 expression on NK cells.

Conclusions:

• Perturbed DNAM-1 expression on tumor-associated NK cells, induced by chronic ligand exposure, may limit NK cell-mediated rejection of ovarian carcinoma.
• Tumor-induced alterations in activating NK cell receptor expression can impair immune surveillance and contribute to tumor progression.