Association of MHC class I expression and lymph node metastasis of gastric carcinoma

HLA gene encodes MHC, which could represent a common mechanism for enhanced antitumor immune response through T-cell cytotoxicity. Loss of HLA class I expression has been considered to be an important prognostic factor in many malignancies. We investigated the impact of HLA class I expression on lymph node metastasis in gastric carcinoma.

We examined HLA class I expression in clinical samples from 349 patients by immunohistochemistry and compared primary lesions and metastatic lymph nodes. We analyzed the expression of HLA class I antigen in gastric cancer cell lines using flow-cytometry and HLA-A typed these cell lines using PCR.

HLA class I expression was down-regulated in metastatic lymph nodes compared with its expression in primary lesion. Patients with negative expression showed a significantly poorer prognosis. We observed down-regulation of HLA class I antigen in OCUM-2MLN cell line, which has a high potential for metastasizing to lymph node. PCR-SBT analysis indicated LOH of HLA-A gene in OCUM-2MLN.

We showed that HLA class I expression was abrogated in tumor cells that had metastasized to lymph nodes. We further suggest that loss of HLA class I due to LOH was associated with lymph node metastasis.