3135

HLA-G

major histocompatibility complex, class I, G;HLA-G;major histocompatibility complex, class I, G

HLA G antigen|HLA class I histocompatibility antigen, alpha chain G|HLA class I molecule|HLA-G histocompatibility antigen, class I, G|MHC class I antigen G|b2 microglobulin

6p21.3

protein-coding

The human leukocyte antigen G (HLA-G) is a non-classical HLA class I molecule predominantly expressed in trophoblastic placental cells to protect the fetus during pregnancy. However, evidence has shown that this molecule may be implicated in the immune escape mechanism of tumor cells. Thus, the aim of this study was to evaluate the frequency of 14-bp insertion/deletion HLA-G polymorphism, as well as the expression of this molecule in patients with invasive breast ductal carcinoma (IDC). A significant association between the expression of HLA-G and the presence of metastasis in lymph nodes (p=0.01) was observed and the expression of HLA-G was significantly higher in patients with shorter survival time (p=0.03). The analysis suggests that the polymorphism observed in patients with IDC may be inducing a higher expression of the HLA-G molecule, which may possibly contribute to shorter survival time and a worse clinical prognosis for such patients.

Previous study showed that aberrant HLA-G expression in cancer cells plays important roles in disease progression and it was associated with tumor metastasis and with poor survival in an animal model with ovarian cancer; however, the mechanisms remain to be explored. In this study, we found that HLA-G expression could dramatically decreased the NK cytotoxicity against the ovarian carcinoma cell line (HO-8910) engineered to express HLA-G (HO-8910-G), and matrix metalloproteinase-15 (MMP-15) expression was up-regulated in HO-8910-G cells. Consistent with this, a strong correlation between HLA-G and MMP-15 expression were observed in a cohort of ovarian cancer samples. Knockdown the HLA-G induced MMP-15 expression by small interfere RNA (siRNA) significantly decreased the HO-8910-G cell migration potential and tumor metastasis. Collectively, our study indicated that HLA-G involved in tumor invasiveness or metastasis may rely on the NK cytotoxicity inhibition and induction of MMP-15 expression in ovarian cancer.

Papillary thyroid carcinoma (PTC) is the most common type of thyroid cancer and can present as lymph node metastasis in 30 to 65% of cases when initially diagnosed. High frequency recurrence, distant metastasis and treatment resistance can be found in cases of PTC so early diagnosis and treatment are critical for improved prognosis and better survival rates. The characterization of new biomarkers has proved useful for the diagnosis and follow-up of these patients. HLA-G is a non-classical HLA class I molecule whose expression in cancer cells has been associated with tumor evasion of immune response. Therefore, the aim of this study was to investigate the HLA-G expression and its clinical significance in PTC. Paraffin-embedded thyroid biopsies of 70 PTC patients (40 of whom had presented with metastasis) were evaluated. HLA-G-staining was observed in tumor cells in PTC, and the HLA-G expression was significantly associated with an increased occurrence of lymph node metastasis (p=0.0006) and capsular invasion (p=0.02). This preliminary data shows the HLA-G expression in thyroid carcinoma specimens for the first time and suggests that this expression could impair efficient anti-tumor immunity in PTC. This would indicate that HLA-G could have an independent prognostic value in PTC, principally for tumor recurrence.