Effect of gamma interferon on HLA class-I and -II transcription and protein expression in human breast adenocarcinoma cell lines

Immunotherapy for Early-Stage Triple Negative Breast Cancer: Is Earlier Better?

PURPOSE OF REVIEW

In this narrative review, we discuss the optimal timing of immune checkpoint inhibitors (ICI) in early triple negative breast cancer (TNBC), the landscape of predictive biomarkers for the use of immunotherapy, and the mounting literature suggesting a benefit for an early use of ICI.

RECENT FINDINGS

TNBC is associated with a poor prognosis relative to other breast cancer subtypes, and until recently, the treatment of TNBC was limited to cytotoxic chemotherapy. In 2021, the immune-checkpoint inhibitor, pembrolizumab, was approved in combination with neoadjuvant chemotherapy for patients with high-risk early stage TNBC. This approval changed the treatment paradigm of early TNBC concomitantly raised several challenges in clinical practice, pertaining to patient selection, toxicity management, and post-neoadjuvant treatment, among others. The introduction of neoadjuvant chemoimmunotherapy has transformed the treatment landscape for early TNBC. However, several challenges, including patient selection, toxicity management, and the identification of predictive biomarkers, need to be addressed. Future research should focus on refining the timing and duration of immunotherapy, optimizing the chemotherapy partner, and exploring novel predictive biomarkers of response or toxicity.

Insight into Cancer Immunity: MHCs, Immune Cells and Commensal Microbiota

Cancer cells circumvent immune surveillance via diverse strategies. In accordance, a large number of complex studies of the immune system focusing on tumor cell recognition have revealed new insights and strategies developed, largely through major histocompatibility complexes (MHCs). As one of them, tumor-specific MHC-II expression (tsMHC-II) can facilitate immune surveillance to detect tumor antigens, and thereby has been used in immunotherapy, including superior cancer prognosis, clinical sensitivity to immune checkpoint inhibition (ICI) therapy and tumor-bearing rejection in mice. NK cells play a unique role in enhancing innate immune responses, accounting for part of the response including immunosurveillance and immunoregulation. NK cells are also capable of initiating the response of the adaptive immune system to cancer immunotherapy independent of cytotoxic T cells, clearly demonstrating a link between NK cell function and the efficacy of cancer immunotherapies. Eosinophils were shown to feature pleiotropic activities against a variety of solid tumor types, including direct interactions with tumor cells, and accessorily affect immunotherapeutic response through intricating cross-talk with lymphocytes. Additionally, microbial sequencing and reconstitution revealed that commensal microbiota might be involved in the modulation of cancer progression, including positive and negative regulatory bacteria. They may play functional roles in not only mucosal modulation, but also systemic immune responses. Here, we present a panorama of the cancer immune network mediated by MHCI/II molecules, immune cells and commensal microbiota and a discussion of prospective relevant intervening mechanisms involved in cancer immunotherapies.

T cells in health and disease

T cells are crucial for immune functions to maintain health and prevent disease. T cell development occurs in a stepwise process in the thymus and mainly generates CD4⁺ and CD8⁺ T cell subsets. Upon antigen stimulation, naïve T cells differentiate into CD4⁺ helper and CD8⁺ cytotoxic effector and memory cells, mediating direct killing, diverse immune regulatory function, and long-term protection. In response to acute and chronic infections and tumors, T cells adopt distinct differentiation trajectories and develop into a range of heterogeneous populations with various phenotype, differentiation potential, and functionality under precise and elaborate regulations of transcriptional and epigenetic programs. Abnormal T-cell immunity can initiate and promote the pathogenesis of autoimmune diseases. In this review, we summarize the current understanding of T cell development, CD4⁺ and CD8⁺ T cell classification, and differentiation in physiological settings. We further elaborate the heterogeneity, differentiation, functionality, and regulation network of CD4⁺ and CD8⁺ T cells in infectious disease, chronic infection and tumor, and autoimmune disease, highlighting the exhausted CD8⁺ T cell differentiation trajectory, CD4⁺ T cell helper function, T cell contributions to immunotherapy and autoimmune pathogenesis. We also discuss the development and function of γδ T cells in tissue surveillance, infection, and tumor immunity. Finally, we summarized current T-cell-based immunotherapies in both cancer and autoimmune diseases, with an emphasis on their clinical applications. A better understanding of T cell immunity provides insight into developing novel prophylactic and therapeutic strategies in human diseases.

Harnessing Antitumor CD4+ T Cells for Cancer Immunotherapy

Simple Summary

Diverse evidence revealed that CD4⁺ T cells play an important role in antitumor immunity by promoting or suppressing cytotoxic T cell responses. This review outlines the role of CD4⁺ T subsets within the tumor microenvironment and summarizes the latest progress regarding their potentials in cancer immunotherapy and methods for improving outcomes in cancer strategies by modulating CD4⁺ T responses.

Abstract

Over the past decades, CD4⁺ T cells have been considered as a supporting actor in the fields of cancer immunotherapy. Until recently, accumulating evidence has demonstrated the critical role of CD4⁺ T cells during antitumor immunity. CD4⁺ T cells can either suppress or promote the antitumor cytotoxic CD8⁺ T cell responses, either in secondary lymphoid organs or in the tumor. In this review, we provide an overview of the multifaceted role of different CD4⁺ T cell subsets in cancer immune response and their contribution during cancer therapies. Specifically, we focus on the latest progress regarding the impact of CD4⁺ T cell modulation on immunotherapies and other cancer therapies and discuss the prospect for harnessing CD4⁺ T cells to control tumor progression and prevent recurrence in patients.

Epigenetic Reprogramming of CD4+ Helper T Cells as a Strategy to Improve Anticancer Immunotherapy

Evidences highlight the role of various CD4⁺ helper T cells (CD4⁺ Th) subpopulations in orchestrating the immune responses against cancers. Epigenetics takes an important part in the regulation of CD4⁺ Th polarization and plasticity. In this review, we described the epigenetic factors that govern CD4⁺ T cells differentiation and recruitment in the tumor microenvironment and their subsequent involvement in the antitumor immunity. Finally, we discussed how to manipulate tumor reactive CD4⁺ Th responses by epigenetic drugs to improve anticancer immunotherapy.

Inhibition of BRAF Sensitizes Thyroid Carcinoma to Immunotherapy by Enhancing tsMHCII-mediated Immune Recognition

CONTEXT

Multiple mechanisms play roles in restricting the ability of T-cells to recognize and eliminate tumor cells.

OBJECTIVE

To identify immune escape mechanisms involved in papillary thyroid carcinoma (PTC) to optimize immunotherapy.

SETTING AND DESIGN

iTRAQ analysis was conducted to identify proteins differentially expressed in PTC samples with or without BRAFV600E mutation. Molecular mechanisms regulating tumor cell evasion were investigated by in vitro modulations of BRAF/MAPK and related pathways. The pathological significance of identified tumor-specific major histocompatibility complex class II (tsMHCII) molecules in mediating tumor cell immune escape and targeted immune therapy was further evaluated in a transgenic mouse model of spontaneous thyroid cancer.

RESULTS

Proteomic analysis showed that tsMHCII level was significantly lower in BRAFV600E-associated PTCs and negatively correlated with BRAF mutation status. Constitutive activation of BRAF decreased tsMHCII surface expression on tumor cells, which inhibited activation of CD4+ T-cells and led to immune escape. Pathway analysis indicated that the transforming growth factor (TGF)-β1/SMAD3-mediated repression of tsMHCII, which could be reversed by BRAF inhibition (BRAFi). Targeting this pathway with a combined therapy of BRAF inhibitor PLX4032 and anti-PD-1 antibody efficiently blocked tumor growth by increasing CD4+ T-cell infiltration in a transgenic PTC mouse model.

CONCLUSIONS

Our results suggest that BRAFV600E mutation in PTC impairs the expression of tsMHCII through the TGF-β1/SMAD3 pathway to enhance immune escape. Combined treatment with PLX4032 and anti-PD-1 antibody promotes recognition and elimination of PTC by the immune system in a pre-clinical mouse model, and therefore offers an effective therapeutic strategy for patients with advanced PTC.

Identification of microRNAs Targeting the Transporter Associated with Antigen Processing TAP1 in Melanoma

The underlying molecular mechanisms of the aberrant expression of components of the HLA class I antigen processing and presentation machinery (APM) in tumors leading to evasion from T cell-mediated immune surveillance could be due to posttranscriptional regulation mediated by microRNAs (miRs). So far, some miRs controlling the expression of different APM components have been identified. Using in silico analysis and an miR enrichment protocol in combination with small RNA sequencing, miR-26b-5p and miR-21-3p were postulated to target the 3′ untranslated region (UTR) of the peptide transporter TAP1, which was confirmed by high free binding energy and dual luciferase reporter assays. Overexpression of miR-26b-5p and miR-21-3p in melanoma cells downregulated the TAP1 protein and reduced expression of HLA class I cell surface antigens, which could be reverted by miR inhibitors. Moreover, miR-26b-5p overexpression induced a decreased T cell recognition. Furthermore, an inverse expression of miR-26b-5p and miR-21-3p with TAP1 was found in primary melanoma lesions, which was linked with the frequency of CD8⁺ T cell infiltration. Thus, miR-26-5p and miR-21-3p are involved in the HLA class I-mediated immune escape and might be used as biomarkers or therapeutic targets for HLA class I^low melanoma cells.

Characterization of HLA-G Regulation and HLA Expression in Breast Cancer and Malignant Melanoma Cell Lines upon IFN-γ Stimulation and Inhibition of DNA Methylation

The potential role of human leukocyte antigen (HLA)-G as a target for new cancer immunotherapy drugs has increased the interest in the analysis of mechanisms by which HLA-G expression is regulated, and how the expression can be manipulated. We characterized HLA expression in breast cancer and malignant melanoma cell lines and investigated the induction of HLA-G expression by two distinct mechanisms: stimulation with interferon (IFN)-γ or inhibition of methylation by treatment with 5-aza-2'-deoxycytidine (5-aza-dC). The effect of IFN-γ and 5-aza-dC on HLA expression was dependent on the cancer cell lines studied. However, in general, surface expression of HLA class Ia was induced on all cell lines. Surface expression of HLA-G was inconclusive but induction of HLA-G mRNA was prevalent upon treatment with 5-aza-dC and a combination of IFN-γ and 5-aza-dC. IFN-γ alone failed to induce HLA-G expression in the HLA-G-negative cell lines. The results support that HLA-G expression is regulated partly by DNA methylation. Furthermore, IFN-γ may play a role in the maintenance of HLA-G expression rather than inducing expression. The study demonstrates the feasibility of manipulating HLA expression and contributes to the exploration of mechanisms that can be potential targets for immunotherapy in breast cancer and malignant melanoma.

Biological Consequences of MHC-II Expression by Tumor Cells in Cancer

Immunotherapy has emerged as a key pillar of cancer treatment. To build upon the recent successes of immunotherapy, intense research efforts are aimed at a molecular understanding of antitumor immune responses, identification of biomarkers of immunotherapy response and resistance, and novel strategies to circumvent resistance. These studies are revealing new insight into the intricacies of tumor cell recognition by the immune system, in large part through MHCs. Although tumor cells widely express MHC-I, a subset of tumors originating from a variety of tissues also express MHC-II, an antigen-presenting complex traditionally associated with professional antigen-presenting cells. MHC-II is critical for antigen presentation to CD4+ T lymphocytes, whose role in antitumor immunity is becoming increasingly appreciated. Accumulating evidence demonstrates that tumor-specific MHC-II associates with favorable outcomes in patients with cancer, including those treated with immunotherapies, and with tumor rejection in murine models. Herein, we will review current research regarding tumor-enriched MHC-II expression and regulation in a range of human tumors and murine models, and the possible therapeutic applications of tumor-specific MHC-II.

Expression of the MHC class II in triple-negative breast cancer is associated with tumor-infiltrating lymphocytes and interferon signaling

Tumor-infiltrating lymphocytes (TILs) have been known for their strong prognostic and predictive significance in triple-negative breast cancer (TNBC). Several mechanisms for TIL influx in TNBC have been elucidated. Major histocompatibility complex class II (MHC-II) is an essential component of the adaptive immune system and is generally restricted to the surface of antigen-presenting cells. However, it has been reported that interferon-gamma signaling may induce MHC-II in almost all cell types, including those derived from cancer. We aimed to examine the relationship between MHC-II expression in tumor cells and the amount of TILs in 681 patients with TNBC. Further, the prognostic significance of MHC-II and the association of MHC-II with a couple of molecules involved in the interferon signaling pathway were investigated using immunohistochemical staining. Higher MHC-II expression in tumor cells was associated with the absence of lymphovascular invasion (p = 0.042); larger amounts of TILs (p < 0.001); frequent formations of tertiary lymphoid structures (p < 0.001); higher expression of myxovirus resistance gene A, one of the main mediators of the interferon signaling pathway (p < 0.001); and higher expression of double-stranded RNA-activated protein kinase, which can be induced by interferons (p = 0.008). Moreover, tumors that showed high MHC class I expression and any positivity for MHC-II had larger amounts of CD4- and CD8-positive T lymphocytes (p < 0.001). Positive MHC-II expression in tumor cells was associated with better disease-free survival in patients who had lymph node metastasis (p = 0.009). In conclusion, MHC-II expression in tumor cells was closely associated with an increase in TIL number and interferon signaling in TNBC. Further studies are warranted to improve our understanding regarding TIL influx, as well as patients’ responses to immunotherapy.

Activation of ERα signaling differentially modulates IFN-γ induced HLA-class II expression in breast cancer cells

The coordinate regulation of HLA class II (HLA-II) is controlled by the class II transactivator, CIITA, and is crucial for the development of anti-tumor immunity. HLA-II in breast carcinoma is associated with increased IFN-γ levels, reduced expression of the estrogen receptor (ER) and reduced age at diagnosis. Here, we tested the hypothesis that estradiol (E₂) and ERα signaling contribute to the regulation of IFN-γ inducible HLA-II in breast cancer cells. Using a panel of established ER⁻ and ER⁺ breast cancer cell lines, we showed that E₂ attenuated HLA-DR in two ER⁺ lines (MCF-7 and BT-474), but not in T47D, while it augmented expression in ER⁻ lines, SK-BR-3 and MDA-MB-231. To further study the mechanism(s), we used paired transfectants: ERα⁺ MC2 (MDA-MB-231 c10A transfected with the wild type ERα gene) and ERα⁻ VC5 (MDA-MB-231 c10A transfected with the empty vector), treated or not with E₂ and IFN-γ. HLA-II and CIITA were severely reduced in MC2 compared to VC5 and were further exacerbated by E₂ treatment. Reduced expression occurred at the level of the IFN-γ inducible CIITA promoter IV. The anti-estrogen ICI 182,780 and gene silencing with ESR1 siRNA reversed the E₂ inhibitory effects, signifying an antagonistic role for activated ERα on CIITA pIV activity. Moreover, STAT1 signaling, necessary for CIITA pIV activation, and selected STAT1 regulated genes were variably downregulated by E₂ in transfected and endogenous ERα positive breast cancer cells, whereas STAT1 signaling was noticeably augmented in ERα⁻ breast cancer cells. Collectively, these results imply immune escape mechanisms in ERα⁺ breast cancer may be facilitated through an ERα suppressive mechanism on IFN-γ signaling.

Microenvironment of the murine mammary carcinoma 4T1: endogenous IFN-gamma affects tumor phenotype, growth, and metastasis

IFN-gamma has a profound influence on growth and metastasis of solid tumors. This is true for the murine mammary carcinoma 4T1 which grows faster and metastasizes much more readily when transplanted into the mammary fatpads of IFN-gamma(-/-) mice. We were interested in determining which infiltrating hematopoietic cells produce IFN-gamma within the 4T1 tumor microenvironment. 4T1 tumors were infiltrated with progressively increasing numbers of F4/80(+)/CD11c(+) myeloid cells, many of which were also Gr-1(+), and Gr-1(+)/CD11b(+) granulocytes. Only small numbers of CD4 T cells, CD8 T cells, NK cells, and gammadelta T cells, the most likely IFN-gamma-producing cells, were seen at any time point. Sensitive intracellular cytokine staining and flow cytometry revealed no tumor-infiltrating hematopoietic cells with detectable levels of intracellular IFN-gamma, although IFN-gamma mRNA transcripts were detected in tumor tissue. However, a progressive increase in the expression of three IFN-gamma-inducible surface membrane proteins (B7-H1, I-A(d), and ICAM-1) on growing 4T1 tumor cells indicated the presence of biologically active IFN-gamma in the tumor microenvironment. Moreover, 4T1 tumor cells from in vitro culture expressed these surface molecules 48 h after intratumoral injection into mature tumors. These data suggest that very low amounts of endogenous IFN-gamma elaborated by infiltrating hematopoietic cells within the microenvironment of a solid tumor can achieve biologically active concentrations and affect tumor phenotype, growth, and metastasis.

Effect of invariant chain on major histocompatibility complex class I molecule expression and stability on human breast tumor cell lines

Invariant chain (Ii) binds to the human leukocyte antigen (HLA) class II molecule and assists it in the process of peptide acquisition. In addition, Ii binds to the HLA class I molecule, although there has been little study of its effects on the HLA class I molecule. In addition to its normal expression on antigen-presenting cells, Ii expression is up regulated in a variety of tumors. By flow cytometric analysis, we found that expression of Ii resulted in an increase in the number of cell surface HLA class I molecules and in the proportion of unstable HLA class I molecules at the surface of breast tumor cell lines. These data suggest that the expression of Ii by tumor cells may quantitatively and qualitatively alter the presentation of antigens on those cells.

Retinoic acid-inducible gene-I is induced by interferon-gamma and regulates the expression of interferon-gamma stimulated gene 15 in MCF-7 cells

Retinoic acid-inducible gene-I (RIG-I) is a member of the DExH box family proteins, which have diverse roles in regulation of gene expression and cellular functions. We found RIG-I mRNA and protein were expressed in MCF-7 human breast cancer cells stimulated with interferon-gamma (IFN-gamma). This effect of IFN-gamma was observed in concentration- and time-dependent manners, and IFN-gamma also induced promoter activity of RIG-I. Transfection of GFP-RIG-I cDNA into MCF-7 cells resulted in the expression of RIG-I protein in cytoplasm. Overexpression of RIG-I induced the upregulation of IFN-gamma stimulated gene 15, which has the potential to amplify the immunomodulatory effects. We conclude that IFN-gamma induces the expression of RIG-I, which may play a role in the immunological effects of IFN-gamma.

HLA-DRB alleles are differentially expressed by tumor cells in breast carcinoma

The biologic and prognostic significance of HLA-DR expression and T-cell infiltration in breast carcinoma are presently controversial. To test the hypothesis that these factors are influenced by particular HLA-DRB alleles, 52 breast tumor samples, composed of 26 DRB1*04 and 26 non-DRB1*04 tumors, were assessed using immunohistochemistry for expression of DR and its associated invariant chain (Ii) and for infiltrating CD3+ T cells. While DR expression by tumor cells was significantly associated with T-cell infiltration, DRB1*04 tumors were more frequently DR+ Ii+ and contained smaller CD3+ infiltrates than non-DRB1*04 tumors. This difference was largely attributable to DRB1*07 tumors, which were typically DR- Ii-, although they contained similar numbers of T cells to DR+ Ii+ tumors. Further analysis of DR+ tumors using allotype discriminating antibodies revealed that DRB1*04 alleles were always expressed, while non-DRB1*04 alleles were inconsistently expressed. The results of this study provide the first reported evidence that DRB alleles influence DR expression and T-cell infiltration in breast carcinoma and suggest that multiple factors contribute to DR expression. Ongoing studies aimed at elucidating the molecular and immunologic mechanisms controlling differential DR expression and implications for prognosis and outcome should further our understanding of the antitumor immune response and evasion strategies employed by tumor cells.

Genetic modulation of tumor antigen presentation

An effective cancer-cell vaccine is created by expressing major-histocompatibility-complex (MHC) class II molecules without the invariant chain protein (Ii) that normally blocks the antigenic-peptide-binding site of MHC class II molecules at their synthesis in the endoplasmic reticulum. Such tumor-cell constructs are created either by the transfer of genes for MHC class IIalpha and beta chains, or by the induction of MHC class II molecules and Ii protein with a transacting factor, followed by Ii suppression using antisense methods. Preclinical validation of this approach is reviewed with the goal of using this immunotherapy for metastatic human cancers.

HLA-DR and beta 2 microglobulin expression in medullary and atypical medullary carcinoma of the breast: histopathologically similar but biologically distinct entities

AIMS

To examine the expression of HLA-DR and beta 2 microglobulin in medullary carcinoma and atypical medullary carcinoma of the breast to determine if the effective presentation of tumour antigens to the immune system can differentiate between these two histopathologically similar entities.

METHODS

Expression of HLA-DR and beta 2 microglobulin was examined by immunohistochemical methods in five samples of medullary carcinoma of the breast, which has a relatively favourable prognosis, six samples of atypical medullary carcinoma of the breast, which has a prognosis closer to that of regular invasive duct carcinoma, and 20 samples of invasive duct carcinomas, 10 with an accompanying lymphocytic infiltrate.

RESULTS

A positive and significant correlation was found between tumour type and both HLA-DR and beta 2 microglobulin expression. Expression was most prominent in medullary carcinoma, followed by atypical medullary carcinoma and invasive duct carcinoma with and without lymphocytic infiltrates. The mean intensity and percentage of HLA-DR tumour immunostaining were significantly higher in medullary carcinoma than in the other three tumour groups, as was the mean intensity of beta 2 microglobulin immunostaining. Mean percentage of beta 2 microglobulin immunostaining was significantly higher in medullary carcinoma than in invasive duct carcinoma without lymphocytic infiltrates, and showed a trend to increase from invasive duct carcinoma with lymphocytic infiltrates to atypical medullary carcinoma and medullary carcinoma.

CONCLUSIONS

Medullary carcinoma and atypical medullary carcinoma of the breast differ in their expression of HLA-DR and beta 2 microglobulin. The relatively favourable prognosis of medullary carcinoma of the breast may be related to effective tumour antigen presentation to the immune system through MHC-I and MHC-II expression. Immunotherapy aimed at MHC-I and MHC-II induction might have a beneficial effect in breast cancer.

c-erbB-2 and episialin challenge host immune response by HLA class I expression in human non-small-cell lung cancer

The role of major histocompatibility complex expression in cancer prognosis and pathogenesis is contradictory. The aim of the current study was to compare the expression of HLA class I molecules and of oncoproteins that may be sources of peptides presented by HLA class I antigens in non-small-cell lung cancer. For this purpose, the expression of HLA class I antigen and TAP-1 molecule (a transporter in the antigen-processing 1 transport protein) were studied with epidermal growth factor, receptor; c-erbB-2; episialin; wild-type and mutant p53; bcl-2 oncoprotein expression; and angiogenic factor expression (vascular endothelial growth factor and thymidine phosphorylase). The degree of lymphocytic stromal infiltration and of platelet-endothelial cell adhesion molecule-expressing lymphocytes was also studied. A strong association of c-erbB-2 and MUC1 (episialin) expression with HLA class I expression was observed (p = 0.005 and 0.009, respectively). Intense CD31-positive lymphocytic infiltration was also more frequent in HLA class I-positive cases (p = 0.05). Although there was no association of HLA class I expression with survival, loss of the HLA class I expression in MUC1 or c-erbB-2 overexpressing cases conferred a poorer clinical outcome (p = 0.04). Both c-erbB-2 and MUC1 are well-known targets of T-cell-mediated cytotoxicity and cell-cell or cell-matrix adhesion-regulating proteins. The authors provide evidence that the sequence of cell adhesion-disrupting oncoprotein expression, HLA class I induction, and enhanced epitope presentation followed by lymphocytic response is an important pathogenetic three-step sequence of events that define, in part, the clinical outcome in non-small-cell lung cancer.

Discoordinate Surface Expression of IFN-γ-Induced HLA Class II Proteins in Nonprofessional Antigen-Presenting Cells with Absence of DM and Class II Colocalization

We compared HLA class II expression in a human melanoma line (a nonprofessional APC), induced by IFN-γ or by stable transfection with CIITA, with constitutive class II expression in an EBV-transformed B lymphoblastoid cell line (a professional APC) from the same donor. IFN-γ-induced and CIITA-transfected melanoma cells expressed DR, DP, and DQ at levels similar to those expressed by the professional APC; however, DP and DQ proteins and DM-dependent DR epitopes were delayed in appearing on the cell surface when induced by IFN-γ. The delay in cell surface expression of some IFN-γ-induced class II epitopes was observed even though Northern blots demonstrated class II and DM genes to be coordinately transcribed and their mRNA levels to be equivalent to that in B lymphoblastoid cells. Confocal microscopy suggests that discoordinate cell surface expression of class II results from different intracellular trafficking for IFN-γ-induced class II proteins in the melanoma line compared with that in professional APCs. Specifically, although DR and DM proteins were present 2 days after IFN-γ induction, colocalization of DR and DM proteins intracellularly was not apparent in cells at any time after induction. Failure of DR and DM proteins to colocalize suggests that IFN-γ-induced cells lack an intracellular MIIC-like compartment. The absence of a compartment containing DR and DM to facilitate interaction between the two proteins may account for the delayed surface expression of class II epitopes whose formation requires both class II and DM.

Upregulation of DF3, in association with ICAM-1 and MHC class II by IFN-gamma in short-term human mammary carcinoma cell cultures

This study was designed to determine whether in vitro exposure of isolated short-term human primary and metastatic breast tumor cell cultures to interferon-gamma (IFN-gamma) could enhance expression of the breast tumor associated DF3 antigen in association with the intercellular adhesion molecule 1 (ICAM-1) and MHC class II molecules. Cell cultures were established from primary solid tumors and metastatic cells as previously described (Sgagias et al., 1995). Data show that recombinant human IFN-gamma treatment, in vitro, dramatically increased the breast tumor associated DF3 antigen, in association with ICAM-1, and MHC class II antigens in primary breast cancer cell cultures. All primary breast tumor cell cultures constitutively expressed high levels of HLA-class I antigen. Metastatic breast cancer cell cultures expressed high levels of DF3 and recombinant human IFN-gamma treatment, in vitro, upregulated ICAM-1 and MHC class II antigens before and after passage of the metastatic cells through the nude mouse. Metastatic breast cancer cells similar to primary breast cancer cells constitutively expressed high levels of MHC class I antigens. In addition, three LAK cell lines significantly lysed the primary and the metastatic breast tumor cell cultures to the same degree before and after passage of the metastatic cancer cells through the nude mouse. These data indicate the upregulation of the breast tumor associated DF3 antigen in vitro after IFN-gamma treatment and its persistence in vivo, after passage of the metastatic breast cancer cells through the nude mouse. The ability of IFN-gamma to upregulate the breast tumor associated DF3 antigen in association with the ICAM-1 and HLA class II antigens may play an important role in eliciting an immune response which may contribute to the immunodiagnosis, and immunotherapy of breast cancer.

Increased expression of MHC class I molecules on human cells after short time IFN-gamma treatment

Human cell lines and blood lymphocytes were treated for short time periods with IFN-gamma. This treatment increased the amount of the assembled MHC class I molecules on the plasma membrane after 30 min. This early increase of the membrane expression subsided in the next few hours. A second wave of elevation occurred after 8-24 hr. Analysis of cytoplasmic and membrane molecules in pulse chase experiments showed that the cytokine enhanced both the assembly of available heavy and light chains and the transport of the complex to the plasma membrane. The membrane level of the HLA-A2 molecules showed similar kinetics. Addition of an A2 specific binding peptide stabilized the IFN-gamma induced molecules on the cell surface. It seems that IFN-gamma alone or together with a binding peptide can influence MHC class I expression solely through post-transcriptional events utilizing an available pool of free heavy and light chains already after a short time, before the enhancement of the synthesis starts.

Immunization by gamma-IFN-treated B16-F10.9 melanoma cells protects against metastatic spread of the parental tumor

B16-F10.9 is a highly metastatic clone of the B16-F10 melanoma line, that expresses low levels of MHC class-I antigens. F10.9 cells transfected with H-2Kb are highly immunogenic and consequently exhibit a low metastatic phenotype. Treatment with gamma-IFN elevated H-2Kb and H-2Db cell surface expression of F10.9 cells to levels much higher than did transfection of these genes. Yet, following intravenous injection, the gamma-IFN treated cells generated high loads of lung metastases. However, when tested for their immunogenic effect, they elicited CTL and were sensitive to CTL. Immunization with both the positive transfectant KI and the gamma-IFN-treated F10.9 cells protected in vivo against metastatic spread of a subsequent transplant of parental F10.9 cells. The protection elicited by KI transfectants was more effective than the protection by gamma-IFN-treated cells.