Determining Factors in the Therapeutic Success of Checkpoint Immunotherapies against PD-L1 in Breast Cancer: A Focus on Epithelial-Mesenchymal Transition Activation

Immunoglobulin-binding protein and Toll-like receptors in immune landscape of breast cancer

Breast cancer (BC) is a complex disease exhibiting significant heterogeneity and encompassing various molecular subtypes. Among these, triple-negative breast cancer (TNBC) stands out as one of the most challenging types, characterized by its aggressive nature and poor prognosis. This review embarks on a comprehensive exploration of the immune landscape of BC, with a primary focus on the functional and structural characterization of immunoglobulin-binding protein (BiP) and its pivotal role in regulating the unfolded response (UPR) pathway of proteins. Moreover, we unravel the multifaceted functions of BiP in BC, with a special emphasis on the involvement of cell surface BiP in TNBC metastasis, drug resistance, and its contribution to the formation of the tumor microenvironment (TME). We also provide mechanistic insights into how ER-resident BiP mediates the sensitization of drug-resistant BC to different treatment strategies, thereby offering promising avenues for therapeutic intervention. We also delve into the role of Toll-like receptors (TLRs), shedding light on their diverse expression patterns across BC and their influence on modulating the tumor immune response. Understanding the interplay between BiP, TLRs, and the immune response, especially in TNBC, opens avenues for novel immunotherapies. Future research should focus on developing targeted therapies that activate ER-resident BiP or inhibit cell surface BiP, and modulate TLR signaling. Moreover, exploring BiP as a biomarker for TNBC diagnosis, prognosis, and treatment response will be crucial for personalized medicine.

PD-1/PD-L1 immune checkpoint blockade in breast cancer: research insights and sensitization strategies

Immunotherapy targeting programmed cell death-1 (PD-1) and PD-L1 immune checkpoints has reshaped treatment paradigms across several cancers, including breast cancer. Combining PD-1/PD-L1 immune checkpoint blockade (ICB) with chemotherapy has shown promising efficacy in both early and metastatic triple-negative breast cancer, although only a subset of patients experiences durable responses. Identifying responders and optimizing immune drug selection are therefore critical. The effectiveness of PD-1/PD-L1 immunotherapy depends on both tumor-intrinsic factors and the extrinsic cell-cell interactions within the tumor microenvironment (TME). This review systematically summarizes the key findings from clinical trials of ICBs in breast cancer and examines the mechanisms underlying PD-L1 expression regulation. We also highlight recent advances in identifying potential biomarkers for PD-1/PD-L1 therapy and emerging evidence of TME alterations following treatment. Among these, the quantity, immunophenotype, and spatial distribution of tumor-infiltrating lymphocytes stand out as promising biomarkers. Additionally, we explore strategies to enhance the effectiveness of ICBs in breast cancer, aiming to support the development of personalized treatment approaches tailored to the unique characteristics of each patient's tumor.

Enhancing the Efficacy of Breast Cancer Immunotherapy Using a Smac-Armed Oncolytic Virus

It has been shown that the response rate of TNBC is dependent on the level of PD-L1 and the tumor microenvironment (TME). Approaches that alter the TME can improve the efficacy of ICIs. Background: We have engineered a Smac-armed oncolytic virus by inserting a Smac transgene into the genome of a vesicular stomatitis virus to generate VSV-S. Our previous study shows that the anticancer efficacy of VSV-S is more potent than that of wild-typed VSV in a subcutaneous TNBC mouse model. VSV-S treatment reverts the immunosuppressive TME by reducing MDSCs and TAMs, while increasing infiltration of neutrophils and CD8+ T cells. Methods: VSV-S was used to treat TNBC in an orthotopic mouse model, and in a combination therapy with an anti-PD-1 antibody to treat metastatic TNBC in a mouse model. Changes in the TME were evaluated. Results: In this current study, we show that neoadjuvant VSV-S treatment of primary orthotopic TNBC tumors in mice drastically lowered lung metastasis after surgical removal of the primary tumor, and significantly increased the survival rate. The mechanism of action and changes to the TME were delineated, among which one significant marker is the elevation of PD-L1 expression in tumors. In the TNBC lung metastasis mouse model, pulmonary treatment with VSV-S greatly enhanced the efficacy of ICI treatment. Conclusions: Our results suggest that the combination of oncolytic virus and ICI therapies has the potential to substantially improve the outcome of TNBC treatment.

Current progress and prospects for G protein-coupled estrogen receptor in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is a biologically and clinically heterogeneous disease. The G protein-coupled estrogen receptor (GPER) plays a crucial role in mediating the effect of estrogen and estrogen-like compounds in TNBC cells. Compared with other subtypes, GPER has a higher expression in TNBC. The GPER mechanisms have been thoroughly characterized and analyzed in estrogen receptor α (ERα) positive breast cancer, but not in TNBC. Our previous work revealed that a higher expression of GPER mRNA indicates a better prognosis for ERα-positive breast cancer; however, its effects in TNBC differ. Whether GPER could serve as a predictive prognostic marker or therapeutic target for TNBC remains unclear. In this review, we provide a detailed introduction to the subcellular localization of GPER, the different effects of various ligands, and the interactions between GPER and closely associated factors in TNBC. We focused on the internal molecular mechanisms specific to TNBC and thoroughly explored the role of GPER in promoting tumor development. We also discussed the interaction of GPER with specific cytokines and chemokines, and the relationship between GPER and immune evasion. Additionally, we discussed the feasibility of using GPER as a therapeutic target in the context of existing studies. This comprehensive review highlights the effects of GPER on TNBC, providing a framework and directions for future research.

An alternatively spliced PD-L1 isoform PD-L1∆3, and PD-L2 expression in breast cancers: implications for eligibility scoring and immunotherapy response

Targeting PD-1/PD-L1 has shown substantial therapeutic response and unprecedented long-term durable responses in the clinic. However, several challenges persist, encompassing the prediction of treatment effectiveness and patient responses, the emergence of treatment resistance, and the necessity for additional biomarkers. Consequently, we comprehensively explored the often-overlooked isoforms of crucial immunotherapy players, leveraging transcriptomic analysis, structural modeling, and immunohistochemistry (IHC) data. Our investigation has led to the identification of an alternatively spliced isoform of PD-L1 that lacks exon 3 (PD-L1∆3) and the IgV domain required to interact with PD-1. PD-L1∆3 is expressed more than the canonical isoform in a subset of breast cancers and other TCGA tumors. Using the deep learning-based protein modeling tool AlphaFold2, we show the lack of a possible interaction between PD-L1∆3 and PD-1. In addition, we present data on the expression of an additional ligand for PD-1, PD-L2. PD-L2 expression is widespread and positively correlates with PD-L1 levels in breast and other tumors. We report enriched epithelial-mesenchymal transition (EMT) signature in high PD-L2 transcript expressing (PD-L2 > PD-L1) tumors in all breast cancer subtypes, highlighting potential crosstalk between EMT and immune evasion. Notably, the estrogen gene signature is downregulated in ER + breast tumors with high PD-L2. The data on PD-L2 IHC positivity but PD-L1 negativity in breast tumors, together with our results on PD-L1∆3, highlight the need to utilize PD-L2 and PD-L1 isoform-specific antibodies for staining patient tissue sections to offer a more precise prediction of the outcomes of PD-1/PD-L1 immunotherapy.

Immune Checkpoint Blockade Therapy for Breast Cancer: Lessons from Epithelial-Mesenchymal Transition

Immune checkpoint blockade therapies have generated efficacious responses in certain tumor types; however, the responses of breast carcinomas have been largely limited. Moreover, the identity of various parameters that can predict responses to immunotherapies, and at the same time, serve as putative biomarkers that can be therapeutically targeted to enhance the effectiveness of immunotherapies for breast cancers, remains to be comprehensively delineated. Activation of epithelial-mesenchymal plasticity in cancer cells, including those of the breast, increases their tumor-initiating potential and promotes their aggressiveness and resistance to multiple treatment regimens. Moreover, the residence of cancer cells in alternating epithelial or mesenchymal plastic phenotypic states can also influence their immuno-modulatory properties and susceptibilities to immune checkpoint blockade therapies. In this current opinion, we discuss the lessons that can be learnt from epithelial-mesenchymal transition to potentiate the efficacy of immunotherapy for breast cancers. We also discuss strategies to sensitize more-mesenchymal cancer cells to anti-tumor immunity and immune checkpoint blockade therapies, with the hope that these can serve as new translational avenues for the treatment of human breast tumors.

Necroptosis-Related LncRNAs Signature and Subtypes for Predicting Prognosis and Revealing the Immune Microenvironment in Breast Cancer

Purpose

Necroptosis is a mode of programmed cell death that overcomes apoptotic resistance. We aimed to construct a steady necroptosis-related signature and identify subtypes for prognostic and immunotherapy sensitivity prediction.

Methods

Necroptosis-related prognostic lncRNAs were selected by co-expression analysis, and were used to construct a linear stepwise regression model via univariate and multivariate Cox regression, along with least absolute shrinkage and selection operator (LASSO). Quantitative reverse transcription polymerase chain reaction (RT-PCR) was used to measure the gene expression levels of lncRNAs included in the model. Based on the riskScore calculated, we separated patients into high- and low-risk groups. Afterwards, we performed CIBERSORT and the single-sample gene set enrichment analysis (ssGSEA) method to explore immune infiltration status. Furthermore, we investigated the relationships between the signature and immune landscape, genomic integrity, clinical characteristics, drug sensitivity, and immunotherapy efficacy.

Results

We constructed a robust necroptosis-related 22-lncRNA model, serving as an independent prognostic factor for breast cancer (BRCA). The low-risk group seemed to be the immune-activated type. Meanwhile, it showed that the higher the tumor mutation burden (TMB), the higher the riskScore. PD-L1-CTLA4 combined immunotherapy seemed to be a promising treatment strategy. Lastly, patients were assigned to 4 clusters to better discern the heterogeneity among patients.

Conclusions

The necroptosis-related lncRNA signature and molecular clusters indicated superior predictive performance in prognosis and the immune microenvironment, which may also provide guidance to drug regimens for immunotherapy and provide novel insights into precision medicine.

Current Photoactive Molecules for Targeted Therapy of Triple-Negative Breast Cancer

Cancer is the second leading cause of death worldwide; therefore, there is an urgent need to find safe and effective therapies. Triple-negative breast cancer (TNBC) is diagnosed in ca. 15-20% of BC and is extremely aggressive resulting in reduced survival rate, which is mainly due to the low therapeutic efficacy of available treatments. Photodynamic therapy (PDT) is an interesting therapeutic approach in the treatment of cancer; the photosensitizers with good absorption in the therapeutic window, combined with their specific targeting of cancer cells, have received particular interest. This review aims to revisit the latest developments on chlorin-based photoactive molecules for targeted therapy in TNBC. Photodynamic therapy, alone or combined with other therapies (such as chemotherapy or photothermal therapy), has potential to be a safe and a promising approach against TNBC.

EFFECT OF MICRORNA-138 ON EPITHELIAL-MESENCHYMAL TRANSITION AND INVASION OF BREAST CANCER CELLS BY TARGETING SEMAPHORIN 4C

In view of the role of miR-138 in cancer cells, we predicted the target of miR-138 and its targeting to SEMA4C by bioinformatics software and luciferase experiment. The expression levels of miR-138 in human normal breast epithelial cells and two kinds of BC cells were compared, and the transfection cells were selected. MiR-138 mimetic negative control (miR-NC), miR-138 mimic and miR-138 inhibitor were designed for cell transfection. The results showed that the expression level of miR-138 in MCF-7 cells was the lowest. The up regulation of miR-138 would lead to the high expression of E-cad and the low expression of N-cad, vim and SEMA4C, and the vitality and invasion of BC cells would decrease. The down regulation of miR-138 would lead to the low expression of E-cad and the high expression of N-cad, vim and SEMA4C, and the vitality and invasion of BC cells would increase. miR-138 targeted regulation of SEMA4C can promote the expression of N-cad, inhibit the expression of E-cad, vim and SEMA4C, reverse the EMT of BC cells, and inhibit the activity and invasion of BC cells. MiR-138 has clinical potential as a tumor marker of BC.