Analysis and clinical relevance of human leukocyte antigen class I, heavy chain, and β2-microglobulin downregulation in breast cancer

Cancer Immune Evasion Through Loss of MHC Class I Antigen Presentation

Major histocompatibility class I (MHC I) molecules bind peptides derived from a cell's expressed genes and then transport and display this antigenic information on the cell surface. This allows CD8 T cells to identify pathological cells that are synthesizing abnormal proteins, such as cancers that are expressing mutated proteins. In order for many cancers to arise and progress, they need to evolve mechanisms to avoid elimination by CD8 T cells. MHC I molecules are not essential for cell survival and therefore one mechanism by which cancers can evade immune control is by losing MHC I antigen presentation machinery (APM). Not only will this impair the ability of natural immune responses to control cancers, but also frustrate immunotherapies that work by re-invigorating anti-tumor CD8 T cells, such as checkpoint blockade. Here we review the evidence that loss of MHC I antigen presentation is a frequent occurrence in many cancers. We discuss new insights into some common underlying mechanisms through which some cancers inactivate the MHC I pathway and consider some possible strategies to overcome this limitation in ways that could restore immune control of tumors and improve immunotherapy.

β2-microglobulin has a different regulatory molecular mechanism between ER+ and ER- breast cancer with HER2. BMC Cancer 2019;19:223. [PMID: 30866857 PMCID: PMC6417228 DOI: 10.1186/s12885-019-5410-1]

Background

Previous studies have demonstrated that β2-microglobulin (β2M) promotes the growth and survival of a variety of cancer cells and has different regulatory effects on the expression of Bcl-2 and HER2 in HER2⁻ breast cancer cells. However, β2M-mediated signaling in ER⁺ and ER⁻ breast cancer with HER2⁻ remains unclear.

Methods

β2M expression vector and siRNA were transfected into two types of HER2⁻ breast cancer cells, and the possible relevant signaling molecules were subsequently analyzed by real-time PCR and western blotting. These signaling molecules were also analyzed by real-time PCR and immunohistochemistry (IHC) in two types of HER2⁻ breast cancer tissues, and the associations between β2M and these signaling molecules were assessed using Spearman’s correlation analysis.

Results

β2M silencing downregulated p-SGK1/SGK1 levels and Bcl-2 expression, and β2M overexpression downregulated p-CREB/CREB and significantly upregulated p-SGK1/SGK1 levels and Bcl-2 expression, and both resulting processes did not affect HER2, HIF-1α, VEGF, and ERK signaling in ER⁺ breast cancer cells with HER2⁻. β2M silencing upregulated p-CREB/CREB and VEGF protein and significantly downregulated p-ERK/ERK levels, and β2M overexpression downregulated p-CREB/CREB and VEGF, significantly upregulated p-ERK/ERK levels, and both resulting processes did not affect HIF-1α and SGK1 signaling in ER⁻ breast cancer cells with HER2⁻. β2M expression was positively correlated with p-CREB, p-SGK1, and Bcl-2 expression and had no correlation with HIF-1α, VEGF, and p-ERK1/2, whereas p-SGK1 exhibited a significantly positive correlation with Bcl-2 expression in cancer tissues of patients with luminal A breast cancer, which coincide with the results obtained from the same molecular types of breast cancer cells except CREB signaling. However, β2M expression did not show a significant correlation with HIF-1α, p-CREB, VEGF, p-SGK1, p-ERK1/2, and Bcl-2 expression in cancer tissues of patients with basal-like breast cancer, which was discordant with the results obtained from the same molecular types of breast cancer cells.

Conclusions

β2M has a different molecular regulatory mechanism between ER⁺ and ER⁻ breast cancer with HER2⁻, and it may promote tumor survival through the SGK1/Bcl-2 signaling pathway in ER⁺ breast cancer with HER2⁻ and has no regulatory effects on ER⁻ breast cancer with HER2⁻.

Targeted and immuno-biology driven treatment strategies for triple-negative breast cancer: current knowledge and future perspectives

Introduction: Accounting for about 15% of breast cancer patients, triple-negative breast cancer (TNBC) is responsible for 25% of disease related deaths, more frequent distant spread and visceral metastasis. However, improving survival in TNBC failed and primary resistance, immunological ignorance and tumor heterogeneity limit clinical activity of novel therapies. In view of recent molecular, genetic and immunologic insights, this review aims to describe the current status of immunological and targeted treatments from a hypothesis driven perspective. Areas covered: Recent preclinical studies and ongoing clinical trials for immune directed and targeted treatments of TNBC are summarized, including immune-checkpoint blockade, resistance mechanisms, inhibition of poly (ADP-ribose) polymerase (PARP), combinatorial strategies as well as preclinical, hypothesis generating studies. Expert commentary: Sustained responses have been observed with immune-checkpoint blockade and PARP inhibitors demonstrated remarkable efficacy in germline BRCA mutated TNBC. In order to generate clinical success of many other, to date ineffective, targeted and immune therapies, the integration of multidimensional, large amounts of data, will be essential and likely accelerate treatment progress of TNBC.

Ly49 family receptors are required for cancer immunosurveillance mediated by natural killer cells

According to the missing-self hypothesis, natural killer (NK) cells survey for target cells that lack MHC-I molecules. The Ly49 receptor family recognizes loss of MHC-I and is critical for educating NK cells, conferring the ability to eliminate transformed or infected cells. In this study, we evaluated their requirement in innate immune surveillance of cancer cells using genetically manipulated mice with attenuated expression of Ly49 receptors (NKC(KD)) in several models of carcinoma and metastasis. We found that NKC(KD) mice exhibited uncontrolled tumor growth and metastases. Expression of two MHC-I alleles, H-2K(b) and H-2D(b), was decreased in tumors from NKC(KD) mice in support of the likelihood of NK-mediated tumor immunoediting. These tumor cells exhibited directed alterations to their cell surface expression in response to the genetically altered immune environment to evade host recognition. Immunoediting in NKC(KD) mice was restricted to MHC-I molecules, which are ligands for Ly49 receptors, while expression of Rae-1 and Mult1, ligands for another NK cell receptor, NKG2D, were unaffected. Restoring NK cell education in NKC(KD) mice with a transgene for the inhibitory self-MHC-I receptor Ly49I restored suppression of cancer onset and growth. Interestingly, immune surveillance mediated by activating Ly49 receptors remained intact in NKC(KD) mice, as demonstrated by the ability to stimulate the NKG2D receptor with tumor cells or splenocytes expressing Rae-1. Together, our results genetically establish the integral role of Ly49 in NK cell-mediated control of carcinogenesis through MHC-I-dependent missing-self recognition.

Establishment of a monoclonal anti-pan HLA class I antibody suitable for immunostaining of formalin-fixed tissue: unusually high frequency of down-regulation in breast cancer tissues

A novel monoclonal anti-pan human leukocyte antigen (HLA) class I heavy chain antibody, EMR8-5, was established. It could detect HLA-A, -B, and -C antigens in formalin-fixed paraffin embedded tissues. By immunohistochemical staining using the EMR8-5 antibody, various cancer tissues from 246 cases were examined for HLA class I expression. It was found that HLA class I expression was decreased in 20% to 42% of the cases of lung cancer, hepatocellular carcinoma, colon cancer, renal cell carcinoma, and urothelial carcinoma. In contrast, 85% of breast cancer cases had loss of or decreased HLA class I expression. Of the 35 breast cancer cases that had decreased HLA class I heavy chain expression, 33 (94%) also had decreased beta2-microglobulin expression detected by immunohistochemical staining. It was suggested that HLA class I down-regulation might be a common characteristic of breast cancer mostly caused by the down-regulation of beta2-microglobulin expression.

Transcriptomic landscape of breast cancers through mRNA sequencing

Breast cancer is a heterogeneous disease with a poorly defined genetic landscape, which poses a major challenge in diagnosis and treatment. By massively parallel mRNA sequencing, we obtained 1.2 billion reads from 17 individual human tissues belonging to TNBC, Non-TNBC, and HER2-positive breast cancers and defined their comprehensive digital transcriptome for the first time. Surprisingly, we identified a high number of novel and unannotated transcripts, revealing the global breast cancer transcriptomic adaptations. Comparative transcriptomic analyses elucidated differentially expressed transcripts between the three breast cancer groups, identifying several new modulators of breast cancer. Our study also identified common transcriptional regulatory elements, such as highly abundant primary transcripts, including osteonectin, RACK1, calnexin, calreticulin, FTL, and B2M, and "genomic hotspots" enriched in primary transcripts between the three groups. Thus, our study opens previously unexplored niches that could enable a better understanding of the disease and the development of potential intervention strategies.