Mechanisms involved in the regulation of human leukocyte antigen class II expression in estrogen receptor alpha positive and estrogen receptor alpha negative breast cancer cells

Mostafa, Ahmed A. (2014) Mechanisms involved in the regulation of human leukocyte antigen class II expression in estrogen receptor alpha positive and estrogen receptor alpha negative breast cancer cells. Doctoral (PhD) thesis, Memorial University of Newfoundland.

[English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (33MB)

Abstract

Human leukocyte antigen (HLA) class II molecules [HLA-DR, HLA-DM, invariant chain (Ii)] are crucial for anti-tumor immune responses. Regulation of HLA class II occurs mainly at the transcription level through the class II transactivator (CIITA) that is induced by interferon gamma (IFN-γ). In addition, mitogen activation protein kinase (MAPK) regulates HLA class II expression at the protein and the transcriptional level in antigen presenting cells (APC) and some tumors. Previously, our laboratory reported that tumor cell expression of HLA-DR in breast cancer correlated with decreased estrogen receptor (ER) levels and younger age at diagnosis. In this study we used established ERα⁺ and ERα- breast cancer cell lines (BCCL) from ATTC and showed that, estradiol (E₂) resulted in down regulation of HLADR expression in MCF-7 (ERα⁺) and BT-474 (ERα⁺), but not in T47-D (ERα⁺), nor in SK-BR-3 (ERα⁻) and MDA-MB-231 (ERα⁻). Altogether, these data suggest that the E2- ER pathway plays a significant role in HLA class II expression in breast carcinoma. We further postulated that the higher expression of HLA-DR in ERα-, as compared to ERα⁺ breast cancer cells is due to MAPK activation. To study the mechanism(s) involved in the regulation of HLA class II expression in breast cancer cells, we used a cell line model of an ERα⁺ cell line, MC2 (MDA-MB- 231 transfected with the wild type ERα gene) and ERα- cell line, VC5 (MDA-MB-231 transfected with the empty vector). These cells were subjected to different hormonal treatments [E₂, Tamoxifen (TAM) and Fulvestrant (ICI 182,780)], cytokine treatments (IFN-γ) and MAPK inhibitors (U0126, SP 600125 and SB 202190), to determine their effects on HLA class II regulation. Inducible CIITA and HLA class II expression were markedly reduced at the protein and transcription levels in MC2, compared to VC5. Moreover, CIITA and IFN-γ activated sequence (GAS) luciferase activities were reduced in MC2 and were further inhibited by E₂-treatment. In parallel, E₂ decreased GAS luciferase activity in the same pattern in MCF-7 (ERα⁺) and BT-474 (ERα⁺). The MAPK pathway played a role in HLA-DR surface expression in the breast cancer cell lines (BCCL) regardless of ERα status. In aggregate, these results indicate that the E₂-ER and MAPK signaling pathways modulate HLA class II expression in BCCL.

Actions (login required)

View Item