Clinical significance of tumor expression of major histocompatibility complex class I-related chains A and B (MICA/B) in gastric cancer patients.

Gastric cancer (GC) is the third most common cause of cancer death worldwide. Natural killer cells play an important role in the immune defense against transformed cells. They express the activating receptor NKG2D, whose ligands belong to the MIC and ULBP/RAET family. Although it is well established that these ligands are generally expressed in tumors, the association between their expression in the tumor and gastric mucosa and clinical parameters and prognosis of GC remains to be addressed. In the present study, MICA and MICB expression was analyzed, by flow cytometry, in 23 and 20 pairs of gastric tumor and adjacent non-neoplasic gastric mucosa, respectively. Additionally, ligands expression in 13 tumors and 7 gastric mucosa samples from GC patients were evaluated by immunohistochemistry. The mRNA levels of MICA in 9 pairs of tumor and mucosa were determined by quantitative PCR. Data were associated with the clinicopathological characteristics and the patient outcome. MICA expression was observed in 57% of tumors (13/23) and 44% of mucosal samples (10/23), while MICB was detected in 50% of tumors (10/20) and 45% of mucosal tissues (9/20). At the protein level, ligand expression was significantly higher in the tumor than in the gastric mucosa. MICA mRNA levels were also increased in the tumor as compared to the mucosa. However, clinicopathological analysis indicated that, in patients with tumors >5 cm, the expression of MICA and MICB in the tumor did not differ from that of the mucosa, and tumors >5 cm showed significantly higher MICA and MICB expression than tumors ≤5 cm. Patients presenting tumors >5 cm that expressed MICA and MICB had substantially shorter survival than those with large tumors that did not express these ligands. Our results suggest that locally sustained expression of MICA and MICB in the tumor may contribute to the malignant progression of GC and that expression of these ligands predicts an unfavorable prognosis in GC patients presenting large tumors.

Erlotinib enhances the CIK cell-killing sensitivity of lung adenocarcinoma A549 cells.

We examined the effects and molecular mechanism of the epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor erlotinib on NKG2D ligand expression in human lung adenocarcinoma A549 cells and the cytotoxicity of cytokine-induced killer cells. Flow cytometry was used to detect NKG2D ligand expression in A549 cells under effects of erlotinib and EGFR downstream molecules, including LY294002 (phosphoinositide 3-kinase inhibitor), SB203580 (mitogen-activated protein kinase inhibitor), and STAT21 (signal transduction and transcription 3 inhibitor) after 24 h. A lactate dehydrogenase release assay was used to detect, at different effector-to-target ratios, the A549 cell killing activity of cytokine-induced killer cells before and after treatment with 10 mM erlotinib. Erlotinib suppressed MICA expression in A549 cells and upregulated MICB and UL16 binding protein 1 expression. EGFR downstream molecules mitogen-activated protein kinase and signal transduction and transcription 3 inhibitor did not affect the expression of NKG2D ligands in A549 cells. The phosphoinositide 3-kinase inhibitor reduced MICA expression in A549 cells, while erlotinib enhanced the killing sensitivity of cytokine-induced killer cells in A549 cells. The anti-lung carcinoma effects of EGFR tyrosine kinase inhibitor were associated with the sensitivity of lung cancer cells to enhanced immune cell killing.

Histone deacetylase inhibitors impair NK cell viability and effector functions through inhibition of activation and receptor expression.

HDACi are being used as a novel, therapeutic approach for leukemias and other hematological malignancies. However, their effect on immune cells remains ill-defined, as HDACi may impair immune surveillance. In this work, we demonstrate that TSA, VPA, and NaB inhibited IFN-γ production by CD56(dim) and CD56(bright) NK cells and NK cell-mediated cytotoxicity against K562 target cells. HDACi promoted minor NK cell apoptosis but inhibited nuclear mobilization of NF-κB p50, which was accompanied by a robust down-regulation of NKG2D and NKp46 on resting NK cells and of NKG2D, NKp44, NKp46, and CD25 on cytokine-activated NK cells. Decreased CD25 expression promoted a weakened IFN-γ secretion upon restimulation of NK cells with IL-2, whereas reduced expression of NKG2D and NKp46 was accompanied by an impaired NKG2D- and NKp46-dependent cytotoxicity. Moreover, NK cells from normal mice treated in vivo with TSA displayed a diminished expression of NK1.1, NKG2D, and NKp46 and secreted reduced amounts of IFN-γ upon ex vivo stimulation with cytokines. Thus, our preclinical results indicate that HDACi exert deleterious effects on NK cell function, which may weaken immune surveillance and facilitate relapse of the malignant disease in HDACi-treated patients.

Low NKp30, NKp46 and NKG2D expression and reduced cytotoxic activity on NK cells in cervical cancer and precursor lesions.

BACKGROUND: Persistent high risk HPV infection can lead to cervical cancer, the second most common malignant tumor in women worldwide. NK cells play a crucial role against tumors and virus-infected cells through a fine balance between activating and inhibitory receptors. Expression of triggering receptors NKp30, NKp44, NKp46 and NKG2D on NK cells correlates with cytolytic activity against tumor cells, but these receptors have not been studied in cervical cancer and precursor lesions. The aim of the present work was to study NKp30, NKp46, NKG2D, NKp80 and 2B4 expression in NK cells from patients with cervical cancer and precursor lesions, in the context of HPV infection. METHODS: NKp30, NKp46, NKG2D, NKp80 and 2B4 expression was analyzed by flow cytometry on NK cells from 59 patients with cervical cancer and squamous intraepithelial lesions. NK cell cytotoxicity was evaluated in a 4 hour CFSE/7-AAD flow cytometry assay. HPV types were identified by PCR assays. RESULTS: We report here for the first time that NK cell-activating receptors NKp30 and NKp46 are significantly down-regulated in cervical cancer and high grade squamous intraepithelial lesion (HGSIL) patients. NCRs down-regulation correlated with low cytolytic activity, HPV-16 infection and clinical stage. NKG2D was also down-regulated in cervical cancer patients. CONCLUSION: Our results suggest that NKp30, NKp46 and NKG2D down-regulation represent an evasion mechanism associated to low NK cell activity, HPV-16 infection and cervical cancer progression.