Effects of retinoids on regulatory cellular interactions in primary mixed lymphocyte reaction (MLR)

Retinoic acid up-regulates the expression of major histocompatibility complex molecules and adhesion/costimulation molecules (specifically, intercellular adhesion molecule ICAM-1) in human cervical cancer

OBJECTIVE

Retinoids are a class of compounds that are structurally related to vitamin A and have been found to be effective in the prevention and treatment of cervical cancer. To investigate whether enhanced immunogenicity might be responsible for such efficacy, we evaluated the effects of retinoic acid on the expression of major histocompatibility complex class I and class II and intercellular adhesion molecule ICAM-1 in human cervical carcinoma cell lines.

STUDY DESIGN

The expression of surface antigens (major histocompatibility complex class I and class II and ICAM-1) was evaluated by fluorescence-activated cell sorter analysis in 3 human cervical carcinoma cell lines after exposure to therapeutic doses of retinoic acid. In addition, the effects on human leukocyte antigen class I messenger ribonucleic acid expression were also evaluated by Northern blot analysis after such treatment.

RESULTS

CaSki, SiHa, and HT-3 cervical cancer cells expressed variable levels of major histocompatibility complex class I and ICAM-1 antigens, whereas class II surface antigens were not detectable. Exposure to therapeutic doses of retinoic acid were able to significantly increase the expression of major histocompatibility complex class I and ICAM-1 antigens in all the cell lines when compared with untreated tumor cells but were not able to induce the expression of class II surface human leukocyte antigens. Northern blot analysis showed that for major histocompatibility complex class I molecules such up-regulation was the result of an increased expression at the transcriptional level of major histocompatibility complex class I messenger ribonucleic acid.

CONCLUSIONS

These data indicate that retinoic acid increases the expression of immunologically important surface antigens, suggesting that the efficacy of retinoic acid in the treatment of cervical cancer may be, at least in part, the result of immunologic modulation. Such findings support additional clinical research investigating the use of retinoids for the treatment of cervical cancer.

Effects of retinoic acid combined with irradiation on the expression of major histocompatibility complex molecules and adhesion/costimulation molecules ICAM-1 in human cervical cancer

OBJECTIVES

Radiation treatment is one of the most standardized and effective modalities for contemporary cervical cancer therapy. In addition, the radiation-potentiating effects of retinoic acid have been recently described. In order to investigate whether enhanced immunogenicity might be responsible for such potentiation, we have evaluated the effects of retinoic acid combined with high doses of gamma-irradiation on the expression of major histocompatibility complex (MHC) Class I and II and intercellular adhesion molecule-1 (ICAM-1) in human cervical carcinoma cell lines.

METHODS

The expression of surface antigens (MHC Class I and II and ICAM-1) was evaluated by FACS analysis in untreated control cells and in cells following their exposure to retinoic acid, high doses of gamma-irradiation (i.e., 5000 and 10,000 cGy), or the combination of the two procedures.

RESULTS

HT-3 and SiHa cervical cancer cells expressed variable levels of MHC Class I and ICAM-1 antigens while Class II surface antigens were not detectable. Exposure to either 5000 or 10,000 cGy completely inhibited cell replication in both cell lines and significantly and consistently increased the expression of all surface antigens present on the cells prior to irradiation. Irradiation was unable to induce neoexpression of antigens previously not expressed by these cells (i.e., MHC Class II). In a similar fashion, retinoic acid was also able to significantly increase the expression of MHC Class I and ICAM-1 antigens when compared to untreated tumor cells but was not able to induce the expression of HLA Class II surface antigens. Exposure to the combination of radiation plus retinoic acid significantly upregulated HLA Class I and ICAM-1 molecules in an additive manner when compared to the levels obtainable with the exposure to radiation or retinoic acid alone.

CONCLUSIONS

These data indicate that the combination of these two treatments could induce an additive effect on the expression of immunologically important surface antigens in human cervical cancer cells. These findings, together with the powerful antiproliferative effect of retinoids and irradiation on tumor cells, suggest that the combined regimen may be a promising and more effective combination for the treatment of cervical cancer.

Effects of retinoic acid combined with interferon-gamma on the expression of major-histocompatibility-complex molecules and intercellular adhesion molecule-1 in human cervical cancer

Retinoids and interferons are important regulators of human epithelial cell differentiation and have been successfully used in the clinical treatment of HPV-involved cervical cancer. In this study, 2 HPV-positive human cervical-carcinoma cell lines were analyzed for their surface expression of MHC-Class-I, MHC-Class-II and ICAM-1 surface antigens before and after exposure to all-trans retinoic acid, interferon-gamma and the combination of the 2 compounds. In addition, the effects on HLA-Class-I-mRNA expression were evaluated after such treatments. Both cell lines expressed MHC-Class-I molecules, and their levels were markedly up-regulated after exposure to IFN-gamma. Similarly, MHC-Class-II and ICAM-1 antigens were either induced or significantly up-regulated by IFN-gamma. Exposure to all-trans retinoic acid was also able to significantly increase the expression of MHC-Class-I and ICAM-I antigens as compared with untreated tumor cells. However, unlike IFN-gamma, retinoids were not able to induce the expression of HLA-Class-II surface antigens. Exposure to the combination of IFN-gamma plus retinoic acid significantly up-regulated (in an additive manner) HLA-Class-I and ICAM-1 molecules as compared with the levels obtainable after exposure to IFN-gamma alone. Finally, Northern-blot analysis of HLA-Class-I-mRNA expression confirmed that the activity of both of these biologic response modifiers was at transcriptional level. These data indicate that the combination of these modalities could induce an additive effect on the expression of immunologically important surface antigens on human cervical-cancer cells. These findings, together with the known anti-proliferative effects mediated by retinoids and IFN-gamma on tumor cells, further support the combination of these agents in the treatment of pre-invasive and invasive human cervical cancer.