Human leukocyte antigens in cancer metastasis: Prognostic approach and therapeutic susceptibility.

Human leukocyte antigens (HLA), which are a group of antigen-presenting proteins, are classified into two main groups: classic (including HLA-I, HLA-II, HLA-III) and non-classic. These molecules are expressed on the surface of several immune cells, which contribute to the defense of body against foreign antigens. Changing expressions of these molecules on tumor cells can be related to reduced ability of the immune system in killing tumor cells, as well as metastasis induction of many solid tumors. The purpose of this review article is to assess the possible relationship between changing expressions of HLA molecules with cancer metastasis and relapse. It can be stated that the changes in the expressions of HLA molecules on tumor cells are an important mechanism for tumor cell escape from immune cells. Therefore, these changes can be associated with tumor development, metastasis, or relapse. Given the essential role of HLA molecule expression in cancer metastasis and relapse, identification of prognostic value of these alterations as well as targeting HLA molecules with new therapeutic approaches may lead to the prevention of these complications.