Cytokine regulation of HIV-1 LTR transactivation in human hepatocellular carcinoma cell lines.

Abstract

Human hepatocellular carcinoma (HCC) cell lines, HEP-G2, J5, and SK-HEP-1, which differ in their differentiation status, were compared for their trans-activating activities after treatment with cytokines or 12-O-tetradecanoylphorbol-13-acetate (TPA). These cells were transfected with a long terminal repeat (LTR) which was derived from human immunodeficiency virus type 1 (HIV-1) and ligated to chloramphenicol acetyl transferase (CAT) gene. After treatment with interleukin-1 alpha (IL-1 alpha), interleukin-6 (IL-6), interferon-gamma (IFN-gamma), or TPA, they exhibited various degrees of enhancement of transactivation. The well differentiated HEP-G2 cells exhibited the highest degree of enhancement with these agents, while the poorly differentiated SK-HEP-1 cells showed no enhancement with cytokines and slight enhancement with TPA. The J5 cells, which were intermediate in their status of differentiation, showed a moderate degree of enhancement with cytokines and TPA. These results suggest that HCC cells at different stages of differentiation may produce different levels of cellular transacting factors activated by each of these agents. To map the cytokine response elements (CREs) in the HIV-1-LTR, HEP-G2 cells were transfected with nested series of 5' deletion mutants of HIV-1-LTR and treated with each of these cytokines. It was found that not only the degrees but also the patterns of enhancement varied depending upon the presence of positive or negative regulatory sequences in HIV-1-LTR, and that the NF-kappa B sequence played an important role, either by itself or in conjunction with the 5'-proximal response elements (REs) to interact with cellular trans-activating factors elicited by the cascade of transduction responses to cytokines. Despite the presence of promoters including kappa B and IFN-gamma RE as well as IL-6RE sequence in HIV-1-LTR-transfected cells, the poorly differentiated SK-HEP-1 cells showed no enhancement of transactivation by these cytokines, suggesting the lack of receptors or activity of some signal transduction factors which are present in well differentiated HEP-G2 and moderately differentiated J5 cells.