PD-L1 is overexpressed on breast cancer stem cells through notch3/mTOR axis

CD44/PD-L1-mediated networks in drug resistance and immune evasion of breast cancer stem cells: Promising targets of natural compounds

Cancer stem cells (CSCs) significantly interfere with immunotherapy, leading to challenges such as low response rates and acquired resistance. PD-L1 expression is associated with the CSC population's overexpression of CD44. Mounting evidence suggests that the breast cancer stem cell (BCSC) marker CD44 and the immune checkpoint PD-L1 contribute to treatment failure through their networks. Natural compounds can overcome therapy resistance in breast cancer by targeting mechanisms underlying resistance in BCSCs. This review provides an updated insight into the CD44 and PD-L1 networks of BCSCs in mediating metastasis and immune evasion. The review critically examines existing literature, providing a comprehensive understanding of the topic and emphasizing the impact of natural flavones on the signaling pathways of BCSCs. Additionally, the review discusses the potential of natural compounds in targeting CD44 and PD-L1 in breast cancer (BC). Natural compounds consistently show potential in targeting regulatory mechanisms of BCSCs, inducing loss of stemness, and promoting differentiation. They offer a promising approach for developing alternative therapeutic strategies to manage breast cancer.

Neem Leaf Glycoprotein Disrupts Exhausted CD8+ T-Cell-Mediated Cancer Stem Cell Aggression

Targeting exhausted CD8+ T-cell (TEX)-induced aggravated cancer stem cells (CSC) holds immense therapeutic potential. In this regard, immunomodulation via Neem Leaf Glycoprotein (NLGP), a plant-derived glycoprotein immunomodulator is explored. Since former reports have proven immune dependent-tumor restriction of NLGP across multiple tumor models, we hypothesized that NLGP might reprogram and rectify TEX to target CSCs successfully. In this study, we report that NLGP's therapeutic administration significantly reduced TEX-associated CSC virulence in in vivo B16-F10 melanoma tumor model. A similar trend was observed in in vitro generated TEX and B16-F10/MCF7 coculture setups. NLGP rewired CSCs by downregulating clonogenicity, multidrug resistance phenotypes and PDL1, OCT4, and SOX2 expression. Cell cycle analysis revealed that NLGP educated-TEX efficiently pushed CSCs out of quiescent phase (G0G1) into synthesis phase (S), supported by hyper-phosphorylation of G0G1-S transitory cyclins and Rb proteins. This rendered quiescent CSCs susceptible to S-phase-targeting chemotherapeutic drugs like 5-fluorouracil (5FU). Consequently, combinatorial treatment of NLGP and 5FU brought optimal CSC-targeting efficiency with an increase in apoptotic bodies and proapoptotic BID expression. Notably a strong nephron-protective effect of NLGP was also observed, which prevented 5FU-associated toxicity. Furthermore, Dectin-1-mediated NLGP uptake and subsequent alteration of Notch1 and mTOR axis were deciphered as the involved signaling network. This observation unveiled Dectin-1 as a potent immunotherapeutic drug target to counter T-cell exhaustion. Cumulatively, NLGP immunotherapy alleviated exhausted CD8+ T-cell-induced CSC aggravation. Implications: Our study recommends that NLGP immunotherapy can be utilized to counter ramifications of T-cell exhaustion and to target therapy elusive aggressive CSCs without evoking toxicity.

Bioactive compounds derived from marine source: a potential immunotherapy treatment

Immunotherapy using checkpoint inhibitors blocks the checkpoint proteins (programmed cell death receptor-1; PD-1) from binding with their corresponding ligands (programmed cell death receptor ligand-1; PD-L1) to regulate cell signaling pathways. The marine environment holds a huge source of small molecules that are understudied which can be developed as an inhibitor. Hence, this study investigated the inhibitory effect of 19 algae-derived small molecules against PD-L1 by using molecular docking, absorption, distribution, metabolism, and elimination (ADME) properties and molecular dynamics simulations (MDS). The molecular docking revealed that the binding energy of the six best compounds ranges from -11.1 to -9.1 kcal/mol. Fucoxanthinol, in particular, has the strongest binding energy at -11.1 kcal/mol with three hydrogen bonds (ASN:63A, GLN:66A, and ASP:122A). Meanwhile, the MDS demonstrated that the ligands were strongly bound to the protein, indicating the stability of the complexes. In summary, the identified compounds are potential PD-L1 inhibitors in immunotherapy.Communicated by Ramaswamy H. Sarma.

Exploring the interplay between triple-negative breast cancer stem cells and tumor microenvironment for effective therapeutic strategies

Triple-negative breast cancer (TNBC) is a highly aggressive and metastatic malignancy with poor treatment outcomes. The interaction between the tumor microenvironment (TME) and breast cancer stem cells (BCSCs) plays an important role in the development of TNBC. Owing to their ability of self-renewal and multidirectional differentiation, BCSCs maintain tumor growth, drive metastatic colonization, and facilitate the development of drug resistance. TME is the main factor regulating the phenotype and metastasis of BCSCs. Immune cells, cancer-related fibroblasts (CAFs), cytokines, mesenchymal cells, endothelial cells, and extracellular matrix within the TME form a complex communication network, exert highly selective pressure on the tumor, and provide a conducive environment for the formation of BCSC niches. Tumor growth and metastasis can be controlled by targeting the TME to eliminate BCSC niches or targeting BCSCs to modify the TME. These approaches may improve the treatment outcomes and possess great application potential in clinical settings. In this review, we summarized the relationship between BCSCs and the progression and drug resistance of TNBC, especially focusing on the interaction between BCSCs and TME. In addition, we discussed therapeutic strategies that target the TME to inhibit or eliminate BCSCs, providing valuable insights into the clinical treatment of TNBC.

PD-L1 intrinsically promotes the proliferation of breast cancer cells through the SKP2-p27/p21 axis

BACKGROUND

PD-L1 intrinsically promotes tumor progression through multiple mechanisms, which potentially leads to resistance to anti-PD-1/PD-L1 therapies. The intrinsic effect of PD-L1 on breast cancer (BC) cell proliferation has not been fully elucidated.

METHODS

we used proteomics, gene expression knockdown (KD), quantitative immunofluorescence (qIF), western blots, functional assays including colony-forming assay (CFA) and real-time cell analyzer (RTCA), and in vivo data using immunohistochemistry in breast cancer patients.

RESULTS

PD-L1 promoted BC cell proliferation by accelerating cell cycle entry at the G1-to-S phase transition. Global proteomic analysis of the differentially expressed nuclear proteins indicated the involvement of several proliferation-related molecules, including p21CIP1/WAF1. Western blotting and qIF demonstrated the higher expression of SKP2 and the lower expression of p21CIP1/WAF1 and p27Kip1 in PD-L1 expressing (PD-L1pos) cells as compared to PD-L1 KD (PD-L1KD) cells. Xenograft-derived cells and the TCGA BC dataset confirmed this relationship in vivo. Functionally, CFA and RTCA demonstrated the central role of SKP2 in promoting PD-L1-mediated proliferation. Finally, immunohistochemistry in 74 breast cancer patients confirmed PD-L1 and SKP-p21/p27 axis relationship, as it showed a highly statistically significant correlation between SKP2 and PD-L1 expression (p < 0.001), and both correlated significantly with the proliferation marker Ki-67 (p < 0.001). On the other hand, there was a statistically significant inverse relationship between PD-L1 and p21CIP1/WAF1 expression (p = 0.005). Importantly, double negativity for p21CIP1/WAF1 and p27Kip1 correlated significantly with PD-L1 (p < 0.001), SKP2 (p = 0.002), and Ki-67 (p = 0.002).

CONCLUSIONS

we have demonstrated the role of the SKP2-p27/p21 axis in intrinsic PD-L1-enhanced cell cycle progression. Inhibitors of SKP2 expression can alleviate resistance to ICPIs.

Targeted immunotherapy to cancer stem cells: A novel strategy of anticancer immunotherapy

Cancer is a major disease that endangers human health. Cancer drug resistance and relapse are the two main causes contributing to cancer treatment failure. Cancer stem cells (CSCs) are a small fraction of tumor cells that are responsible for tumorigenesis, metastasis, relapse, and resistance to conventional anticancer therapies. Therefore, CSCs are considered to be the root of cancer recurrence, metastasis, and drug resistance. Novel anticancer strategies need to face this new challenge and explore their efficacy against CSCs. Recently, immunotherapy has made rapid advances in cancer treatment, and its potential against CSCs is also an interesting area of research. Meanwhile, immunotherapy strategies are novel therapeutic modalities with promising results in targeting CSCs. In this review, we summarize the targeting of CSCs by various immunotherapy strategies such as monoclonal antibodies(mAb), tumor vaccines, immune checkpoint inhibitors, and chimeric antigen receptor-T cells(CAR-T) in pre-clinical and clinical studies. This review provides new insights into the application of these immunotherapeutic approaches to potential anti-tumor therapies in the future.

Novel insights into Notch signaling in tumor immunity: potential targets for cancer immunotherapy

Notch signaling pathway is a highly conserved system of cell-to-cell communication that participates in various biological processes, such as stem cell maintenance, cell fate decision, cell proliferation and death during homeostasis and development. Dysregulation of Notch signaling has been associated with many aspects of cancer biology, such as maintenance of cancer stem-like cells (CSCs), cancer cell metabolism, angiogenesis and tumor immunity. Particularly, Notch signaling can regulate antitumor or pro-tumor immune cells within the tumor microenvironment (TME). Currently, Notch signaling has drawn significant attention in the therapeutic development of cancer treatment. In this review, we focus on the role of Notch signaling pathway in remodeling tumor immune microenvironment. We describe the impact of Notch signaling on the efficacy of cancer immunotherapies. Furthermore, we summarize the results of relevant preclinical and clinical trials of Notch-targeted therapeutics and discuss the challenges in their clinical application in cancer therapy. An improved understanding of the involvement of Notch signaling in tumor immunity will open the door to new options in cancer immunotherapy treatment.

Scoparone attenuates PD-L1 expression in human breast cancer cells by MKP-3 upregulation

Breast cancer is a frequently occurring malignant tumor that is one of the leading causes of cancer-related deaths in women worldwide. Monoclonal antibodies that block programed cell death 1 (PD-1)/programed cell death ligand 1 (PD-L1) - a typical immune checkpoint - are currently the recommended standard therapies for many advanced and metastatic tumors such as triple-negative breast cancer. However, some patients develop drug resistance, leading to unfavorable treatment outcomes. Therefore, other approaches are required for anticancer treatments, such as downregulation of PD-L1 expression and promotion of degradation of PD-L1. Scoparone (SCO) is a bioactive compound isolated from Artemisia capillaris that exhibits antitumor activity. However, the effect of SCO on PD-L1 expression in cancer has not been confirmed yet. This study aimed to evaluate the role of SCO in PD-L1 expression in breast cancer cells in vitro. Our results show that SCO downregulated PD-L1 expression in a dose-dependent manner, via AKT inhibition. Interestingly, SCO treatment did not alter PTEN expression, but increased the expression of mitogen-activated protein kinase phosphatase-3 (MKP-3). In addition, the SCO-induced decrease in PD-L1 expression was reversed by siRNA-mediated MKP-3 knockdown. Collectively, these findings suggest that SCO inhibited the expression of PD-L1 in breast cancer cells by upregulating MKP-3 expression. Therefore, SCO may serve as an innovative combinatorial agent for cancer immunotherapy.

METTL3 facilitates stemness properties and tumorigenicity of cancer stem cells in hepatocellular carcinoma through the SOCS3/JAK2/STAT3 signaling pathway

Liver cancer stem cells (LCSCs) contribute to tumor recurrence and cancer cell proliferation in patients with hepatocellular carcinoma (HCC). METTL3-catalyzed m6A modification is relevant to the cancer stem cell (CSC) phenotype, including LCSCs. LCSCs were isolated from MHCC-97H and HepG2 cells through flow cytometry. UALCAN data were used to analyze the expression of METTL3 in liver hepatocellular carcinoma (LIHC) tissues. Loss- and gain-of-function experiments were utilized to assess the biological effects of METTL3 and SOCS3 on the proliferation and stemness phenotypes in vitro and in vivo. The mechanisms underlying the impact of METTL3 were explored using qPCR, MeRIP-qPCR, dual-luciferase reporter, and western blot assays. METTL3 was significantly upregulated in LIHC tissues according to the UALCAN database. METTL3 was highly expressed in LIHC and was significantly correlated with individual cancer stage, tumor grade and lymph node metastasis. Patients with low METTL3 expression had a longer overall survival time based on the data from UALCAN. In addition, the level of METTL3 was enhanced in LCSCs and decreased in non-LCSCs compared to HCC cells. Moreover, overexpression of METTL3 stimulated the proliferation and stemness of LCSCs in vitro and in vivo, while loss of METTL3 impeded it. Bioinformatics analysis combined with validation experiments determined that m6A was modified by METTL3-targeting SOCS3 mRNA. METTL3 had side effects regarding the stability of SOCS3 mRNA. SOCS3 overexpression impaired and SOCS3 depletion facilitated the development of LCSCs via the JAK2/STAT3 pathway. Furthermore, METTL3 depletion suppressed proliferation and stemness in LCSCs, which was restored by SOCS3 knockdown or colivelin treatment. We discovered that METTL3 facilitated the stemness and tumorigenicity of LCSCs by modifying SOCS3 mRNA with m6A.

Cancer Differentiation Inducer Chlorogenic Acid Suppresses PD-L1 Expression and Boosts Antitumor Immunity of PD-1 Antibody

As immune checkpoint inhibitors have shown good clinical efficacy, immune checkpoint blockade has become a vital strategy in cancer therapy. However, approximately only 12.5% patients experience benefits from immunotherapy. Herein, we identified the cancer differentiation inducer chlorogenic acid (CGA, now in the phase II clinical trial in China for glioma treatment) to be a small-molecular immune checkpoint inhibitor that boosted the antitumor effects of the anti-PD-1 antibody. CGA suppressed the expression of PD-L1 induced by interferon-γ in tumor cell culture through inhibition of the p-STAT1-IRF1 pathway and enhanced activity of activated T-cells. In two murine tumor xenografts, combination therapy of CGA with anti-PD-1 antibody decreased the expression of PD-L1 and IRF1 and increased the inhibitory effect of the anti-PD-1 antibody on tumor growth. Particularly, the activity of tumor infiltrated T cells was enhanced by CGA. CGA improved the gene expression of granzymes in tumor-infiltrated immune cells. In conclusion, through induction of differentiation, CGA appeared to suppress the expression of PD-L1 on cancer cells, effectively promoting infiltrated T cells in the tumor and boosting the antitumor effect of the anti-PD-1 antibody. Thus, CGA might serve as a promising agent to enhance anticancer immunotherapy if combined with anti-PD-1 antibodies.

Dynamic immuno-nanomedicines in oncology

Anti-cancer therapeutics have achieved significant advances due to the emergence of immunotherapies that rely on the identification of tumors by the patients' immune system and subsequent tumor eradication. However, tumor cells often escape immunity, leading to poor responsiveness and easy tolerance to immunotherapy. Thus, the potentiated anti-tumor immunity in patients resistant to immunotherapies remains a challenge. Reactive oxygen species-based dynamic nanotherapeutics are not new in the anti-tumor field, but their potential as immunomodulators has only been demonstrated in recent years. Dynamic nanotherapeutics can distinctly enhance anti-tumor immune response, which derives the concept of the dynamic immuno-nanomedicines (DINMs). This review describes the pivotal role of DINMs in cancer immunotherapy and provides an overview of the clinical realities of DINMs. The preclinical development of emerging DINMs is also outlined. Moreover, strategies to synergize the antitumor immunity by DINMs in combination with other immunologic agents are summarized. Last but not least, the challenges and opportunities related to DINMs-mediated immune responses are also discussed.

Cancer stem cells: a target for overcoming therapeutic resistance and relapse

Cancer stem cells (CSCs) are a small subset of cells in cancers that are thought to initiate tumorous transformation and promote metastasis, recurrence, and resistance to treatment. Growing evidence has revealed the existence of CSCs in various types of cancers and suggested that CSCs differentiate into diverse lineage cells that contribute to tumor progression. We may be able to overcome the limitations of cancer treatment with a comprehensive understanding of the biological features and mechanisms underlying therapeutic resistance in CSCs. This review provides an overview of the properties, biomarkers, and mechanisms of resistance shown by CSCs. Recent findings on metabolic features, especially fatty acid metabolism and ferroptosis in CSCs, are highlighted, along with promising targeting strategies. Targeting CSCs is a potential treatment plan to conquer cancer and prevent resistance and relapse in cancer treatment.

BRD4/nuclear PD-L1/RelB circuit is involved in the stemness of breast cancer cells

BACKGROUND

Breast cancer (BC) is the most common cancer diagnosed in women worldwide. BC stem cells (BCSCs) have been known to be involved in the carcinogenesis of the breast and contribute to therapeutic resistance. The programmed death-ligand 1 (PD-L1) expression of BC correlated with a poor prognosis. Immunotherapies that target PD-L1 have great potential and have been successful when applied to cancer treatment. However, whether PD-L1 regulates BCSC formation is unknown.

METHODS

BCSCs were enriched by serum-free suspension culture. The properties of BCSCs were examined by mammosphere formation assay, CD44+/Cd24-, aldehyde dehydrogenase (ALDH) assay, CSC marker analysis, and mammosphere growth assay. To elucidate the functions of bromodomain-containing protein 4 (BRD4), nuclear PD-L1, and RelB proteins in the stemness of BCSCs, mammosphere formation was examined using BRD4 inhibitor and degrader, PD-L1 degrader, and RelB inhibitor. The antitumor function of 3',4',7,8-tetrahydroxyflavone (THF), a specific BRD4 inhibitor, was studied through in vivo tumor model and mouse studies, and the protein levels of c-Myc, PD-L1, and RelB were examined in tumor model under THF treatment.

RESULTS

BRD4 was upregulated in breast CSCs and regulates the stemness of BCs. The downregulation of BRD4 using BRD4 PROTAC, ARV-825, and BRD4 inhibitor, (+)-JQ1, inhibits mammosphere formation and reduces the levels of breast CSC markers (CD44+/CD24- and ALDH1), stem cell marker genes, and mammosphere growth. BRD4 inhibitor (JQ1) and degrader (ARV825) downregulate membrane and nuclear fractions of PD-L1 through the inhibition of PD-L1 transcript levels. The knockdown of PD-L1 inhibits mammosphere formation. Verteporfin, a PD-L1 degrader, inhibits the transcripts and protein levels of PD-L1 and downregulates the transcript and protein levels of RelB. Calcitriol, a RelB inhibitor, and the knockdown of RelB using si-RelB regulate mammosphere formation through interleukin-6 (IL-6) expression. THF is a natural product and a potent selective BRD4 inhibitor, inhibits mammosphere formation, and reduces the levels of CD44+/CD24- and mammosphere growth by downregulating c-Myc, PD-L1, and RelB. 3',4',7,8-THF shows tumoricidal activity and increased levels of CD3+CD4+ and CD3+CD8+ T-cells in the tumor and tumor-draining lymph nodes (TDLNs) in the murine tumor model using 4T1 and MC38 cells.

CONCLUSIONS

The results show the first evidence of the essential role of the BRD4/nuclear PD-L1/RelB axis in breast CSC formation. The nuclear PD-L1 regulates RelB, and the RelB/p65 complex induces IL6 and breast CSC formation. Targeting nuclear PD-L1 represents a potential and novel tool for immunotherapies of intractable BC. Video Abstract.

γ-Secretase Inhibitor Potentiates the Activity of Suberoylanilide Hydroxamic Acid by Inhibiting Its Ability to Induce Epithelial to Mesenchymal Transition and Stemness via Notch Pathway Activation in Triple-Negative Breast Cancer Cells

Histone deacetylase inhibitors, such as suberoylanilide hydroxamic acid (SAHA), possess great therapeutic value for triple-negative breast cancer patients. However, their inherent ability to induce epithelial to mesenchymal transition in various malignancies has been of greater concern. Herein, we hypothesize that SAHA facilitates epithelial to mesenchymal transition (EMT) via activation of the Notch pathway. From the literature survey, it is evident that histone deacetylase mediates the formation of the co-repressor complex upon interacting with the DNA binding domain, thereby inhibiting the transcription of the Notch downstream genes. Hence, we hypothesize that the use of SAHA facilitates the transcriptional activation of the Notch target genes, by disrupting the co-repressor complex and recruiting the coactivator complex, thereby facilitating EMT. In this study, we have observed that SAHA upregulates the expression profile of the Notch downstream proteins (such as Notch intracellular domain, Hes-1, c-Myc, etc.) and the Notch ligands (such as Jagged-1 and Jagged-2), thereby aberrantly activating the signaling pathway. Therefore, we have focused on combination therapy using a γ-secretase inhibitor LY411575 that would enhance the efficacy of SAHA by blocking the canonical Notch pathway mediated via its intracellular domain. It was observed that co-treatment significantly mediates apoptosis, generates cellular reactive oxygen species, depolarizes mitochondria, and diminishes the stemness properties. Besides, it also mediates autophagy-independent cell death and diminishes the expression of inflammatory cytokines, along with the downregulation in the expression of the Notch downstream genes and mesenchymal markers. Altogether, our study provides a mechanistic basis for combating EMT potentiated by SAHA, which could be utilized as a rational strategy for the treatment of solid tumors, especially triple-negative breast cancer.

Autophagy as a Target for Non-Immune Intrinsic Functions of Programmed Cell Death-Ligand 1 in Cancer

Autophagy is a catabolic process that is essential to the maintenance of homeostasis through the cellular recycling of damaged organelles or misfolded proteins, which sustains energy balance. Additionally, autophagy plays a dual role in modulating the development and progression of cancer and inducing a survival strategy in tumoral cells. Programmed cell death-ligand 1 (PD-L1) modulates the immune response and is responsible for maintaining self-tolerance. Because tumor cells exploit the PD-L1-PD-1 interaction to subvert the immune response, immunotherapy has been developed based on the use of PD-L1-blocking antibodies. Recent evidence has suggested a bidirectional regulation between autophagy and PD-L1 molecule expression in tumor cells. Moreover, the research into the intrinsic properties of PD-L1 has highlighted new functions that are advantageous to tumor cells. The relationship between autophagy and PD-L1 is complex and still not fully understood; its effects can be context-dependent and might differ between tumoral cells. This review refines our understanding of the non-immune intrinsic functions of PD-L1 and its potential influence on autophagy, how these could allow the survival of tumor cells, and what this means for the efficacy of anti-PD-L1 therapeutic strategies.

Predictive significance of HIF-1α, Snail, and PD-L1 expression in breast cancer

Currently, the prediction of breast cancer (BC) effectiveness to drug treatment is based on determining the expression level of steroid hormone receptors and human epidermal growth factor receptor type 2 (HER2). However, significant differences in individual response to drug treatment require the search for new predictive markers. Here, by comprehensively examining HIF-1α, Snail, and PD-L1 expression in BC tumor tissue, we demonstrate that high levels of these markers correlate with unfavorable factors of BC prognosis: the presence of regional and distant metastases and lymphovascular and perineural invasion. Analyzing the predictive significance of markers, we show that the most significant predictors of chemoresistant HER2-negative BC are a high PD-L1 level and a low Snail level, while in HER2-positive BC, only a high PD-L1 level is an independent predictor of chemoresistant BC. Our results suggest that using immune checkpoint inhibitors in these groups of patients may improve drug therapy effectiveness.

PD-L1 Downregulation and DNA Methylation Inhibition for Molecular Therapy against Cancer Stem Cells in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is a heterogeneous cancer characterized by various cellular subtypes. This study investigates the potential of a combination strategy using immunotherapy and epigenetic reprogramming against HCC. We used a transgenic HCC mouse C57BL/6J-TG(ALB1HBV)44BRI/J to assess the dynamics of the programmed death receptor and its ligand (PD-1/PD-L1) and DNA methylation markers. In parallel, PD-L1 RNA silencing was performed in various human HCC cell lines, while combination therapy was performed in a co-culture system using long-term exposure of 5-Azacytidine (5-AZA) and an anti-PD-L1. Data from the mouse model showed that the expressions of Pdcd1, Pdcd1l1, and DNA methyltransferase 1 (Dnmt1) were significantly higher in HCC as compared to the wild-type mice (p < 0.01), supported by the high presence of PD-L1 methylated DNA. In HCC cell lines, PD-L1 silencing was accompanied by DNMT1 reduction, mostly noted in aggressive HCC cell lines, followed by the dysregulation of the cancer stem cell marker EpCAM. In combination therapy, the growth of HCC cells and lymphocytes was limited by the PD-L1 antibody, further reduced in the presence of 5-AZA by up to 20% (p < 0.001). The data demonstrated that combination therapy might be an option as a potential treatment for heterogeneous HCC.

Let-7a/cMyc/CCAT1/miR-17-5p Circuit Re-sensitizes Atezolizumab Resistance in Triple Negative Breast Cancer through Modulating PD-L1

BACKGROUND

Triple negative breast cancer (TNBC) is an immunogenically hot tumor. The immune checkpoint blockades (ICBs) have been recently emerged as promising therapeutic candidates for several malignancies including TNBC. Yet, the development of innate and/or adaptive resistance by TNBC patients towards ICBs such as programmed death-ligand 1 (PD-L1) inhibitors (e.g. Atezolizumab) shed the light on importance of identifying the underlying mechanisms regulating PD-L1 in TNBC. Recently, it was reported that non-coding RNAs (ncRNAs) perform a fundamental role in regulating PD-L1 expression in TNBC. Hence, this study aims to explore a novel ncRNA axis tuning PD-L1 in TNBC patients and investigate its possible involvement in fighting Atezolizumab resistance.

METHODS

In-silico screening was executed to identify ncRNAs that could potentially target PD-L1. Screening of PD-L1 and the nominated ncRNAs (miR-17-5p, let-7a and CCAT1 lncRNA) was performed in BC patients and cell lines. Ectopic expression and/or knockdown of respective ncRNAs were performed in MDA-MB-231. Cellular viability, migration and clonogenic capacities were evaluated using MTT, scratch assay and colony-forming assay, respectively.

RESULTS

PD-L1 was upregulated in BC patients, especially in TNBC patients. PD-L1 is positively associated with lymph node metastasis and high Ki-67 in recruited BC patients. Let-7a and miR-17-5p were nominated as potential regulators of PD-L1. Ectopic expression of let-7a and miR-17-5p caused a noticeable reduction in PD-L1 levels in TNBC cells. In order to investigate the whole ceRNA circuit regulating PD-L1 in TNBC, intensive bioinformatic studies were performed. The lncRNA, Colon Cancer-associated transcript 1 (CCAT1), was reported to target PD-L1 regulating miRNAs. Results showed that CCAT1 is an upregulated oncogenic lncRNA in TNBC patients and cell lines. CCAT1 siRNAs induced a noticeable reduction in PD-L1 levels and a marked increase in miR-17-5p level, building up a novel regulatory axis CCAT1/miR-17-5p/PD-L1 in TNBC cells that was tuned by the let-7a/c-Myc engine. On the functional level, co-treatment of CCAT-1 siRNAs and let-7a mimics efficiently relieved Atezolizumab resistance in MDA-MB-231 cells.

CONCLUSION

The present study revealed a novel PD-L1 regulatory axis via targeting let-7a/c-Myc/CCAT/miR-17-5p. Additionally, it sheds the light on the potential combinational role of CCAT-1 siRNAs and Let-7a mimics in relieving Atezolizumab resistance in TNBC patients.

Engineered vitamin E-tethered non-immunogenic facial lipopeptide for developing improved siRNA based combination therapy against metastatic breast cancer

RNA interference based therapeutic gene silencing is an emerging platform for managing highly metastatic breast cancer. Cytosolic delivery of functional siRNA remains the key obstacle for efficient RNAi therapy. To overcome the challenges of siRNA delivery, we have engineered a vitamin E-tethered, short, optimum protease stabilized facial lipopeptide based non-immunogenic, biocompatible siRNA transporter to facilitate the clinical translation in future. Our designed lipopeptide has an Arginine-Sarcosine-Arginine segment for providing optimum protease-stability, minimizing adjacent arginine-arginine repulsion and reducing intermolecular aggregation and α-tocopherol as the lipidic moiety for facilitating cellular permeabilization. Interestingly, our designed non-immunogenic siRNA transporter has exhibited significantly better long term transfection efficiency than HiPerFect and can transfect hard to transfect primary cell line, HUVEC. Our engineered siRNA therapeutics demonstrated high efficacy in managing metastasis against triple negative breast cancer by disrupting the crosstalk of endothelial cells and MDA-MB-231 and reduced stemness and metastatic markers, as evidenced by downregulating critical oncogenic pathways. Our study aimed at silencing Notch1 signalling to achieve "multi-targeted" therapy with a single putative molecular medicine. We have further developed mechanistically rational combination therapy combining Notch1 silencing with a repurposed drug m-TOR inhibitor, metformin, which demonstrated synergistic interaction and enhanced antitumor efficacy against cancer metastasis.

Deciphering Common Traits of Breast and Ovarian Cancer Stem Cells and Possible Therapeutic Approaches

Breast cancer (BC) and ovarian cancer (OC) are among the most common and deadly cancers affecting women worldwide. Both are complex diseases with marked heterogeneity. Despite the induction of screening programs that increase the frequency of earlier diagnosis of BC, at a stage when the cancer is more likely to respond to therapy, which does not exist for OC, more than 50% of both cancers are diagnosed at an advanced stage. Initial therapy can put the cancer into remission. However, recurrences occur frequently in both BC and OC, which are highly cancer-subtype dependent. Therapy resistance is mainly attributed to a rare subpopulation of cells, named cancer stem cells (CSC) or tumor-initiating cells, as they are capable of self-renewal, tumor initiation, and regrowth of tumor bulk. In this review, we will discuss the distinctive markers and signaling pathways that characterize CSC, their interactions with the tumor microenvironment, and the strategies they employ to evade immune surveillance. Our focus will be on identifying the common features of breast cancer stem cells (BCSC) and ovarian cancer stem cells (OCSC) and suggesting potential therapeutic approaches.

The Role of PRMT5 in Immuno-Oncology

Immune checkpoint inhibitor (ICI) therapy has caused a paradigm shift in cancer therapeutic strategy. However, this therapy only benefits a subset of patients. The difference in responses to ICIs is believed to be dependent on cancer type and its tumor microenvironment (TME). The TME is favorable for cancer progression and metastasis and can also help cancer cells to evade immune attacks. To improve the response to ICIs, it is crucial to understand the mechanism of how the TME is maintained. Protein arginine methyltransferase 5 (PRMT5) di-methylates arginine residues in its substrates and has essential roles in the epigenetic regulation of gene expression, signal transduction, and the fidelity of mRNA splicing. Through these functions, PRMT5 can support cancer cell immune evasion. PRMT5 is necessary for regulatory T cell (Treg) functions and promotes cancer stemness and the epithelial–mesenchymal transition. Specific factors in the TME can help recruit Tregs, tumor-associated macrophages, and myeloid-derived suppressor cells into tumors. In addition, PRMT5 suppresses antigen presentation and the production of interferon and chemokines, which are necessary to recruit T cells into tumors. Overall, PRMT5 supports an immunosuppressive TME. Therefore, PRMT5 inhibition would help recover the immune cycle and enable the immune system-mediated elimination of cancer cells.

The Role of Different Immunocompetent Cell Populations in the Pathogenesis of Head and Neck Cancer-Regulatory Mechanisms of Pro- and Anti-Cancer Activity and Their Impact on Immunotherapy

Head and neck squamous cell carcinoma (HNSCC) is one of the most aggressive and heterogeneous groups of human neoplasms. HNSCC is characterized by high morbidity, accounting for 3% of all cancers, and high mortality with ~1.5% of all cancer deaths. It was the most common cancer worldwide in 2020, according to the latest GLOBOCAN data, representing the seventh most prevalent human malignancy. Despite great advances in surgical techniques and the application of modern combinations and cytotoxic therapies, HNSCC remains a leading cause of death worldwide with a low overall survival rate not exceeding 40-60% of the patient population. The most common causes of death in patients are its frequent nodal metastases and local neoplastic recurrences, as well as the relatively low response to treatment and severe drug resistance. Much evidence suggests that the tumour microenvironment (TME), tumour infiltrating lymphocytes (TILs) and circulating various subpopulations of immunocompetent cells, such regulatory T cells (CD4+CD25+Foxp3+Tregs), cytotoxic CD3+CD8+ T cells (CTLs) and CD3+CD4+ T helper type 1/2/9/17 (Th1/Th2/Th9/Th17) lymphocytes, T follicular helper cells (Tfh) and CD56dim/CD16bright activated natural killer cells (NK), carcinoma-associated fibroblasts (CAFs), myeloid-derived suppressor cells (MDSCs), tumour-associated neutrophils (N1/N2 TANs), as well as tumour-associated macrophages (M1/M2 phenotype TAMs) can affect initiation, progression and spread of HNSCC and determine the response to immunotherapy. Rapid advances in the field of immuno-oncology and the constantly growing knowledge of the immunosuppressive mechanisms and effects of tumour cancer have allowed for the use of effective and personalized immunotherapy as a first-line therapeutic procedure or an essential component of a combination therapy for primary, relapsed and metastatic HNSCC. This review presents the latest reports and molecular studies regarding the anti-tumour role of selected subpopulations of immunocompetent cells in the pathogenesis of HNSCC, including HPV+ve (HPV+) and HPV-ve (HPV-) tumours. The article focuses on the crucial regulatory mechanisms of pro- and anti-tumour activity, key genetic or epigenetic changes that favour tumour immune escape, and the strategies that the tumour employs to avoid recognition by immunocompetent cells, as well as resistance mechanisms to T and NK cell-based immunotherapy in HNSCC. The present review also provides an overview of the pre- and clinical early trials (I/II phase) and phase-III clinical trials published in this arena, which highlight the unprecedented effectiveness and limitations of immunotherapy in HNSCC, and the emerging issues facing the field of HNSCC immuno-oncology.

Variable Intrinsic Expression of Immunoregulatory Biomarkers in Breast Cancer Cell Lines, Mammospheres, and Co-Cultures

Advances in immunotherapy have increased interest in knowing the role of the immune system in breast cancer (BC) pathogenesis. Therefore, immune checkpoints (IC) and other pathways related to immune regulation, such as JAK2 and FoXO1, have emerged as potential targets for BC treatment. However, their intrinsic gene expression in vitro has not been extensively studied in this neoplasia. Thus, we evaluated the mRNA expression of tumor-cell-intrinsic CTLA-4, PDCD1 (PD1), CD274 (PD-L1), PDCD1LG2 (PD-L2), CD276 (B7-H3), JAK2, and FoXO1 in different BC cell lines, derived mammospheres, and co-cultures with peripheral blood mononuclear cells (PBMCs) by real-time quantitative polymerase chain reaction (qRT-PCR). Our results showed that intrinsic CTLA-4, CD274 (PD-L1), and PDCD1LG2 (PD-L2) were highly expressed in triple-negative cell lines, while CD276 was predominantly overexpressed in luminal cell lines. In contrast, JAK2 and FoXO1 were under-expressed. Moreover, high levels of CTLA-4, PDCD1 (PD1), CD274 (PD-L1), PDCD1LG2 (PD-L2), and JAK2 were found after mammosphere formation. Finally, the interaction between BC cell lines and peripheral blood mononuclear cells (PBMCs) stimulates the intrinsic expression of CTLA-4, PCDC1 (PD1), CD274 (PD-L1), and PDCD1LG2 (PD-L2). In conclusion, the intrinsic expression of immunoregulatory genes seems very dynamic, depending on BC phenotype, culture conditions, and tumor-immune cell interactions.

The Great Immune Escape: Understanding the Divergent Immune Response in Breast Cancer Subtypes

Breast cancer, the most common type of cancer affecting women, encompasses a collection of histologic (mainly ductal and lobular) and molecular subtypes exhibiting diverse clinical presentation, disease trajectories, treatment options, and outcomes. Immunotherapy has revolutionized treatment for some solid tumors but has shown limited promise for breast cancers. In this review, we summarize recent advances in our understanding of the complex interactions between tumor and immune cells in subtypes of breast cancer at the cellular and microenvironmental levels. We aim to provide a perspective on opportunities for future immunotherapy agents tailored to specific features of each subtype of breast cancer.

SIGNIFICANCE

Although there are currently over 200 ongoing clinical trials testing immunotherapeutics, such as immune-checkpoint blockade agents, these are largely restricted to the triple-negative and HER2+ subtypes and primarily focus on T cells. With the rapid expansion of new in vitro, in vivo, and clinical data, it is critical to identify and highlight the challenges and opportunities unique for each breast cancer subtype to drive the next generation of treatments that harness the immune system.

Response to primary chemoradiotherapy of locally advanced oropharyngeal carcinoma is determined by the degree of cytotoxic T cell infiltration within tumor cell aggregates

Background

Effective anti-tumor immune responses are mediated by T cells and require organized, spatially coordinated interactions within the tumor microenvironment (TME). Understanding coordinated T-cell-behavior and deciphering mechanisms of radiotherapy resistance mediated by tumor stem cells will advance risk stratification of oropharyngeal cancer (OPSCC) patients treated with primary chemoradiotherapy (RCTx).

Methods

To determine the role of CD8 T cells (CTL) and tumor stem cells for response to RCTx, we employed multiplex immunofluorescence stains on pre-treatment biopsy specimens from 86 advanced OPSCC patients and correlated these quantitative data with clinical parameters. Multiplex stains were analyzed at the single-cell level using QuPath and spatial coordination of immune cells within the TME was explored using the R-package Spatstat.

Results

Our observations demonstrate that a strong CTL-infiltration into the epithelial tumor compartment (HR for overall survival, OS: 0.35; p<0.001) and the expression of PD-L1 on CTL (HR: 0.36; p<0.001) were both associated with a significantly better response and survival upon RCTx. As expected, p16 expression was a strong predictor of improved OS (HR: 0.38; p=0.002) and correlated with overall CTL infiltration (r: 0.358, p<0.001). By contrast, tumor cell proliferative activity, expression of the tumor stem cell marker CD271 and overall CTL infiltration, regardless of the affected compartment, were not associated with response or survival.

Conclusion

In this study, we could demonstrate the clinical relevance of the spatial organization and the phenotype of CD8 T cells within the TME. In particular, we found that the infiltration of CD8 T cells specifically into the tumor cell compartment was an independent predictive marker for response to chemoradiotherapy, which was strongly associated with p16 expression. Meanwhile, tumor cell proliferation and the expression of stem cell markers showed no independent prognostic effect for patients with primary RCTx and thus requires further study.

The role of stem cells in small-cell lung cancer: evidence from chemoresistance to immunotherapy

Small cell lung cancer (SCLC) is the most aggressive subtype of lung cancer, accounting for approximately 15% among all lung cancers. Despite the ability of chemotherapy, the first-line treatment for SCLC, to rapidly shrink tumors, nearly all patients experience recurrence and metastasis within a few months. Cancer stem cells (CSCs) are a small population of tumor cells responsible for tumorigenesis, metastasis, and recurrence after treatment, which play a crucial role in chemoresistance by promoting DNA repair and expression of drug resistance-associated proteins. Thus, targeting CSCs has been successful in certain malignancies. Tumor therapy has entered the era of immunotherapy and numerous preclinical trials have demonstrated the effectiveness of immunotherapeutic approaches targeting CSCs, such as tumor vaccines and chimeric antigen receptor (CAR) T cell, and the feasibility of combining them with chemotherapy. Therefore, a deeper understanding of the interaction between CSCs and immune system is essential to facilitate the advances of new immunotherapies approaches targeting CSCs as well as combination with standard drugs such as chemotherapy. This narrative review summarizes the mechanisms of chemoresistance of CSCs in SCLC and the latest advances in targeted therapies. Thereafter, we discuss the effects of CSCs on tumor immune microenvironment in SCLC and corresponding immunotherapeutic approaches. Eventually, we propose that the combination of immunotherapy targeting CSCs with standard drugs is a promising direction for SCLC therapies.

Pivotal role of PD-1/PD-L1 immune checkpoints in immune escape and cancer progression: Their interplay with platelets and FOXP3+Tregs related molecules, clinical implications and combinational potential with phytochemicals

Immune checkpoint proteins including programmed cell death protein 1 (PD-1), its ligand PD-L1 and cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) are involved in proliferation, angiogenesis, metastasis, chemoresistance via immune escape and immune tolerance by disturbing cytotoxic T cell activation. Though many clinical trials have been completed in several cancers by using immune checkpoint inhibitors alone or in combination with other agents to date, recently multi-target therapy is considered more attractive than monotherapy, since immune checkpoint proteins work with other components such as surrounding blood vessels, dendritic cells, fibroblasts, macrophages, platelets and extracellular matrix within tumor microenvironment. Thus, in the current review, we look back on research history of immune checkpoint proteins and discuss their associations with platelets or tumor cell induced platelet aggregation (TCIPA) and FOXP3+ regulatory T cells (Tregs) related molecules involved in immune evasion and tumor progression, clinical implications of completed trial results and signaling networks by phytochemicals for combination therapy with immune checkpoint inhibitors and suggest future research perspectives.

Systemic Delivery of mPEG-Masked Trispecific T-Cell Nanoengagers in Synergy with STING Agonists Overcomes Immunotherapy Resistance in TNBC and Generates a Vaccination Effect

T-cell engagers (TCEs) represent a breakthrough in hematological malignancy treatment but are vulnerable to antigen escape and lack a vaccination effect. The "immunologically cold" solid tumor presents substantial challenges due to intratumor heterogeneity and an immunosuppressive tumor microenvironment (TME). Here, a methoxy poly(ethylene glycol) (mPEG)-masked CD44×PD-L1/CD3 trispecific T-cell nanoengager loaded with the STING agonist c-di-AMP (CDA) (PmTriTNE@CDA) for the treatment of triple-negative breast cancer (TNBC) is rationally designed. PmTriTNE@CDA shows tumor-specific accumulation and is preferentially unmasked in response to a weakly acidic TME to prevent on-target off-tumor toxicity. The unmasked CD44×PD-L1/CD3 trispecific T-cell nanoengager (TriTNE) targets dual tumor-associated antigens (TAAs) to redirect CD8+ T cells for heterogeneous TNBC lysis while achieving PD-L1 blockade. PmTriTNE synergized with CDA to transform the cold tumor into a hot tumor, eradicate the large established TNBC tumor, and induce protective immune memory in a 4T1 orthotopic tumor model without causing obvious toxicity. PmTriTNE@CDA shows potent efficacy in cell line-derived xenograft (CDX) and patient-derived xenograft (PDX) mouse models. This study serves as a proof-of-concept demonstration of a nanobased TCEs strategy to expand therapeutic combinations that previously could not be achieved due to systemic toxicity with the aim of overcoming TNBC heterogeneity and immunotherapy resistance.

The Notch Signaling Pathway Contributes to Angiogenesis and Tumor Immunity in Breast Cancer

Breast cancer in women is the first leading tumor in terms of incidence worldwide. Some subtypes of BC lack distinct molecular targets and exhibit therapeutic resistance; these patients have a poor prognosis. Thus, the search for new molecular targets is an ongoing challenge for BC therapy. The Notch signaling pathway is found in both vertebrates and invertebrates, and it is a highly conserved in the evolution of the species, controlling cellular fates such as death, proliferation, and differentiation. Numerous studies have shown that improper activation of Notch signaling may lead to excessive cell proliferation and cancer, with tumor-promoting and tumor-suppressive effects in various carcinomas. Thus, inhibitors of Notch signaling are actively being investigated for the treatment of various tumors. The role of Notch signaling in BC has been widely studied in recent years. There is a growing body of evidence suggesting that Notch signaling has a pro-oncogenic role in BC, and the tumor-promoting effect is largely a result of the diverse nature of tumor immunity. Immunological abnormality is also a factor involved in the pathogenesis of BC, suggesting that Notch signaling could be a target for BC immunotherapies. Furthermore, angiogenesis is essential for BC growth and metastasis, and the Notch signaling pathway has been implicated in angiogenesis, so studying the role of Notch signaling in BC angiogenesis will provide new prospects for the treatment of BC. We summarize the potential roles of the current Notch signaling pathway and its inhibitors in BC angiogenesis and the immune response in this review and describe the pharmacological targets of Notch signaling in BC, which may serve as a theoretical foundation for future research into exploring this pathway for novel BC therapies.

Fate decisions of breast cancer stem cells in cancer progression

Breast cancer has a marked recurrence and metastatic trait and is one of the most prevalent malignancies affecting women’s health worldwide. Tumor initiation and progression begin after the cell goes from a quiescent to an activated state and requires different mechanisms to act in concert to regulate t a specific set of spectral genes for expression. Cancer stem cells (CSCs) have been proven to initiate and drive tumorigenesis due to their capability of self-renew and differentiate. In addition, CSCs are believed to be capable of causing resistance to anti-tumor drugs, recurrence and metastasis. Therefore, exploring the origin, regulatory mechanisms and ultimate fate decision of CSCs in breast cancer outcomes has far-reaching clinical implications for the development of breast cancer stem cell (BCSC)-targeted therapeutic strategies. In this review, we will highlight the contribution of BCSCs to breast cancer and explore the internal and external factors that regulate the fate of BCSCs.

Targeted Molecular Construct for Bioorthogonal Theranostics of PD-L1-Expressing Cancer Cells

Molecular targeting of tumor-overexpressed oncoproteins can improve the selectivity and tolerability of anticancer therapies. The immunoinhibitory membrane protein programmed death ligand 1 (PD-L1) is highly expressed on certain tumor types, which masks malignant cells from T cell recognition and creates an optimal environment for the cancer to thrive and spread. We report here a ligand-tetrazine conjugate (LTzC) armed with a PD-L1 small molecule inhibitor to selectively target PD-L1-expressing cancer cells and inhibit PD-L1 function and conjugated to a tetrazine module and a lipoyl group to incorporate bioorthogonal reactivities and an oxidative stress enhancer into the construct. By pairing LTzC with an imaging probe, we have established a "track-&-tag" system for selective labeling of PD-L1 both on and in living cells using click chemistry. We have further shown the specificity and versatility of LTzC by click-to-release activation of prodrugs and selective killing of PD-L1-expressing breast cancer cells, offering a new multimodal approach to "track-&-treat" malignant cells that are capable of evading the immune system.

Self-Sustained Regulation or Self-Perpetuating Dysregulation: ROS-dependent HIF-YAP-Notch Signaling as a Double-Edged Sword on Stem Cell Physiology and Tumorigenesis

Organ development, homeostasis, and repair often rely on bidirectional, self-organized cell-niche interactions, through which cells select cell fate, such as stem cell self-renewal and differentiation. The niche contains multiplexed chemical and mechanical factors. How cells interpret niche structural information such as the 3D topology of organs and integrate with multiplexed mechano-chemical signals is an open and active research field. Among all the niche factors, reactive oxygen species (ROS) have recently gained growing interest. Once considered harmful, ROS are now recognized as an important niche factor in the regulation of tissue mechanics and topology through, for example, the HIF-YAP-Notch signaling pathways. These pathways are not only involved in the regulation of stem cell physiology but also associated with inflammation, neurological disorder, aging, tumorigenesis, and the regulation of the immune checkpoint molecule PD-L1. Positive feedback circuits have been identified in the interplay of ROS and HIF-YAP-Notch signaling, leading to the possibility that under aberrant conditions, self-organized, ROS-dependent physiological regulations can be switched to self-perpetuating dysregulation, making ROS a double-edged sword at the interface of stem cell physiology and tumorigenesis. In this review, we discuss the recent findings on how ROS and tissue mechanics affect YAP-HIF-Notch-PD-L1 signaling, hoping that the knowledge can be used to design strategies for stem cell-based and ROS-targeting therapy and tissue engineering.

Expression Modulation of Immune Checkpoint Molecules by Ibrutinib and Everolimus Through STAT3 in MCF-7 Breast Cancer Cells

Tumor-targeted therapy with small-molecule inhibitors (SMIs) has been demonstrated to be a highly effective therapeutic strategy for various cancers. However, their possible associations with immune evasion mechanisms remain unknown. This study examined the association of inhibitors of the protein kinase B (AKT), mammalian target of rapamycin (mTOR), and Bruton’s tyrosine kinase (BTK) signaling pathways with the expression of immune checkpoint ligands programmed death-ligand 1 (PD-L1), CD155, and galectin-9 (Gal-9) in a breast cancer cell line. MCF-7 cells were treated with everolimus, MK-2206, and ibrutinib. An MTT assay was used to determine the optimal dose for all drugs. A real-time polymerase chain reaction was utilized to measure the mRNA expression of PD-L1, CD155, and Gal-9. The western blot technique was also employed to evaluate the protein expression of the phosphorylated signal transducer and activator of transcription 3 (STAT3). The optimal doses of everolimus, MK-2206, and ibrutinib were observed to be 200, 320, and 2000 nM, respectively. The PD-L1 and CD155 mRNA expression was significantly decreased following the treatment with everolimus and ibrutinib, but not with MK-2206. There were no differences in Gal-9 expression between the single-treated and control groups; however, combined treatment with everolimus and ibrutinib increased its mRNA expression. Everolimus and ibrutinib both inhibited constitutive STAT3 phosphorylation in MCF-7, which was more pronounced in combination treatment. The findings regarding the modulation of PD-L1, CD155, and Gal-9 molecules by SMIs emphasize the crosstalk between the expression of these immune checkpoint molecules and AKT/mTOR/BTK signaling pathways through STAT3 as a critical transcription factor.

Endometrial Cancer Stem Cells: Where Do We Stand and Where Should We Go?

Endometrial cancer is one of the most common malignant diseases in women worldwide, with an incidence of 5.9%. Thus, it is the most frequent cancer of the female genital tract, with more than 34,000 women dying, in Europe and North America alone. Endometrial Cancer Stem Cells (CSC) might be drivers of carcinogenesis as well as metastatic and recurrent disease. Therefore, targeting CSCs is of high interest to improve prognosis of patients suffering of advanced or recurrent endometrial cancer. This review describes the current evidence of molecular mechanisms in endometrial CSCs with special emphasis on MYC and NF-κB signaling as well as mitochondrial metabolism. Furthermore, the current status of immunotherapy targeting PD-1 and PD-L1 in endometrial cancer cells and CSCs is elucidated. The outlined findings encourage novel therapies that target signaling pathways in endometrial CSCs as well as immunotherapy as a promising therapeutic approach in the treatment of endometrial cancer to impede cancer progression and prevent recurrence.

Breast Cancer Stem-Like Cells in Drug Resistance: A Review of Mechanisms and Novel Therapeutic Strategies to Overcome Drug Resistance

Breast cancer is the most frequent type of malignancy in women worldwide, and drug resistance to the available systemic therapies remains a major challenge. At the molecular level, breast cancer is heterogeneous, where the cancer-initiating stem-like cells (bCSCs) comprise a small yet distinct population of cells within the tumor microenvironment (TME) that can differentiate into cells of multiple lineages, displaying varying degrees of cellular differentiation, enhanced metastatic potential, invasiveness, and resistance to radio- and chemotherapy. Based on the expression of estrogen and progesterone hormone receptors, expression of human epidermal growth factor receptor 2 (HER2), and/or BRCA mutations, the breast cancer molecular subtypes are identified as TNBC, HER2 enriched, luminal A, and luminal B. Management of breast cancer primarily involves resection of the tumor, followed by radiotherapy, and systemic therapies including endocrine therapies for hormone-responsive breast cancers; HER2-targeted therapy for HER2-enriched breast cancers; chemotherapy and poly (ADP-ribose) polymerase inhibitors for TNBC, and the recent development of immunotherapy. However, the complex crosstalk between the malignant cells and stromal cells in the breast TME, rewiring of the many different signaling networks, and bCSC-mediated processes, all contribute to overall drug resistance in breast cancer. However, strategically targeting bCSCs to reverse chemoresistance and increase drug sensitivity is an underexplored stream in breast cancer research. The recent identification of dysregulated miRNAs/ncRNAs/mRNAs signatures in bCSCs and their crosstalk with many cellular signaling pathways has uncovered promising molecular leads to be used as potential therapeutic targets in drug-resistant situations. Moreover, therapies that can induce alternate forms of regulated cell death including ferroptosis, pyroptosis, and immunotherapy; drugs targeting bCSC metabolism; and nanoparticle therapy are the upcoming approaches to target the bCSCs overcome drug resistance. Thus, individualizing treatment strategies will eliminate the minimal residual disease, resulting in better pathological and complete response in drug-resistant scenarios. This review summarizes basic understanding of breast cancer subtypes, concept of bCSCs, molecular basis of drug resistance, dysregulated miRNAs/ncRNAs patterns in bCSCs, and future perspective of developing anticancer therapeutics to address breast cancer drug resistance.

PD-L1 interacts with Frizzled 6 to activate β-catenin and form a positive feedback loop to promote cancer stem cell expansion

Cancer stem cells (CSCs) drive tumor initiation, progression, metastasis, and drug resistance. We report here that programmed cell death ligand 1 (PD-L1) is constitutively expressed in cancer cells to maintain and expand CSC through a novel mechanism in addition to promoting cancer cell immune evasion. We discovered that PD-L1 interacts with receptor Frizzled 6 to activate β-catenin signaling and increase β-catenin-targeted gene expression, such as a putative stem cell marker leucine-rich-repeat-containing G-protein-coupled receptor 5. Blockage of PD-L1 function, using a specific small hairpin RNA or a specific antibody, inhibits disease progression by reducing the CSC population in both colorectal and breast tumors. Moreover, β-catenin conversely regulates PD-L1 expression through a β-catenin complex binding site in the PD-L1 promoter. Our discoveries reveal that besides assistant tumor cell immune escaping, PD-L1 and β-catenin signaling form a positive feedback loop to promote cancer progression through CSC maintenance and expansion.

Role, molecular mechanism and the potential target of breast cancer stem cells in breast cancer development

Breast cancer (BC) is one of the most common malignant tumors in women globally, and its occurrence has surpassed lung cancer and become the biggest threat for women. At present, breast cancer treatment includes surgical resection or postoperative chemotherapy and radiotherapy. However, tumor relapse and metastasis usually lead to current therapy failure thanks to breast cancer stem cells (BCSCs)-mediated tumorigenicity and drug resistance. Drug resistance is mainly due to the long-term quiescent G0 phase, strong DNA repairability, and high expression of ABC transporter, and the tumorigenicity is reflected in the activation of various proliferation pathways related to BCSCs. Therefore, understanding the characteristics of BCSCs and their intracellular and extracellular molecular mechanisms is crucial for the development of targeted drugs for BCSCs. To this end, we discussed the latest developments in BCSCs research, focusing on the analysis of specific markers, critical signaling pathways that maintain the stemness of BCSCs，such as NOTCH, Wnt/β-catenin, STAT3, Hedgehog, and Hippo-YAP signaling, immunomicroenviroment and summarizes targeting therapy strategies for stemness maintenance and differentiation, which provides a theoretical basis for further exploration of treating breast cancer and preventing relapse derived from BCSCs.

Immunosuppressive Traits of the Hybrid Epithelial/Mesenchymal Phenotype

Recent preclinical and clinical data suggests enhanced metastatic fitness of hybrid epithelial/mesenchymal (E/M) phenotypes, but mechanistic details regarding their survival strategies during metastasis remain unclear. Here, we investigate immune-evasive strategies of hybrid E/M states. We construct and simulate the dynamics of a minimalistic regulatory network encompassing the known associations among regulators of EMT (epithelial-mesenchymal transition) and PD-L1, an established immune-suppressor. Our simulations for the network consisting of SLUG, ZEB1, miR-200, CDH1 and PD-L1, integrated with single-cell and bulk RNA-seq data analysis, elucidate that hybrid E/M cells can have high levels of PD-L1, similar to those seen in cells with a full EMT phenotype, thus obviating the need for cancer cells to undergo a full EMT to be immune-evasive. Specifically, in breast cancer, we show the co-existence of hybrid E/M phenotypes, enhanced resistance to anti-estrogen therapy and increased PD-L1 levels. Our results underscore how the emergent dynamics of interconnected regulatory networks can coordinate different axes of cellular fitness during metastasis.

Suppression of stemness and enhancement of chemosensibility in the resistant melanoma were induced by Astragalus polysaccharide through PD-L1 downregulation

Chemotherapy is commonly used in the clinical treatment of melanoma, but it is prone to resistance leading to the poor effectiveness. The mechanisms of resistance are complicated including the cancer stemness. Astragalus polysaccharide (APS) is one of the active components of traditional Chinese herbal medicine Astragalus Membranaceus. Our previous work was reported that APS had an inhibitory effect on the stemness of melanoma. In this study we established chemo-resistant melanoma cells and found that expression of stemness genes were upregulated in the resistant melanoma cells. And APS could downregulate expression of stemness genes. Furthermore, APS combined with cisplatin (DDP) could significantly slow down the tumor growth in the mouse model induced by DDP-resistant cells. In addition, we found that programmed death-ligand 1 (PD-L1) expression could be downregulated and the PI3K/AKT signaling could be affected by APS. These results suggested that APS could be a potential candidate in combination with chemotherapeutic agents, which might play a role in reducing the occurrence of resistance and improving the prognosis of melanoma patients.

Dependence receptors: new targets for cancer therapy

Dependence receptors are known to promote survival and positive signaling such as proliferation, migration, and differentiation when activated, but to actively trigger apoptosis when unbound to their ligand. Their abnormal regulation was shown to be an important feature of tumorigenesis, allowing cancer cells to escape apoptosis triggered by these receptors while promoting in parallel major aspects of tumorigenesis such as proliferation, angiogenesis, invasiveness, and chemoresistance. This involvement in multiple cancer hallmarks has raised interest in dependence receptors as targets for cancer therapy. Although additional studies remain necessary to fully understand the complexity of signaling pathways activated by these receptors and to target them efficiently, it is now clear that dependence receptors represent very exciting targets for future cancer treatment. This manuscript reviews current knowledge on the contribution of dependence receptors to cancer and highlights the potential for therapies that activate pro-apoptotic functions of these proteins.

PD-L1 and Notch as novel biomarkers in pancreatic sarcomatoid carcinoma: a pilot study

BACKGROUND

The improved immunological understanding revealed the tumor microenvironment as an appealing driver to restore the immune response against cancer cells resulting in a paradigm shift in the oncology field. However, the complexity of the tumor milieu suggests the role of several pathways linking in immunomodulation mechanisms. Pancreatic cancer represents a model of the intricate relationship between malignant cells and their surrounding neighborhood.

RESEARCH DESIGN AND METHODS

In this study, we analyzed, retrospectively, six cases of rare pancreatic sarcomatoid carcinoma (PSC) and evaluated the expression of PD-L1 and Notch, aiming to explore new attributes in immunophenotype.

RESULTS

PD-L1 CPS ≥ 1was common in PSCs (83%) with half samples expressing PD-L1 CPS ≥ 50. Notch1 and Notch3 demonstrated a high range of expression. A direct significant correlation between PD-L1 and Notch3 overexpression (r = 0.7; p = 0.036) has been observed. Immunofluorescence studies revealed a co-localization of Notch3 and PD-L1 when both proteins were over-expressed within cytoplasmic or membranous compartments of the same cells.

CONCLUSIONS

Our data identify a unique biological characterization of this rare pancreatic histotype. These findings provide a rationale for future studies evaluating the potential crosstalk between PD-L1/PD-1 axis and Notch pathways and prompting the development of novel therapeutics strategy.

Cancer Stem Cell for Tumor Therapy

Simple Summary

Although many methods have been applied in clinical treatment for tumors, they still always show a poor prognosis. Molecule targeted therapy has revolutionized tumor therapy, and a proper target must be found urgently. With a crucial role in tumor development, metastasis and recurrence, cancer stem cells have been found to be a feasible and potential target for tumor therapy. We list the unique biological characteristics of cancer stem cells and summarize the recent strategies to target cancer stem cells for tumor therapy, through which we hope to provide a comprehensive understanding of cancer stem cells and find a better combinational strategy to target cancer stem cells for tumor therapy.

Abstract

Tumors pose a significant threat to human health. Although many methods, such as operations, chemotherapy and radiotherapy, have been proposed to eliminate tumor cells, the results are unsatisfactory. Targeting therapy has shown potential due to its specificity and efficiency. Meanwhile, it has been revealed that cancer stem cells (CSCs) play a crucial role in the genesis, development, metastasis and recurrence of tumors. Thus, it is feasible to inhibit tumors and improve prognosis via targeting CSCs. In this review, we provide a comprehensive understanding of the biological characteristics of CSCs, including mitotic pattern, metabolic phenotype, therapeutic resistance and related mechanisms. Finally, we summarize CSCs targeted strategies, including targeting CSCs surface markers, targeting CSCs related signal pathways, targeting CSC niches, targeting CSC metabolic pathways, inducing differentiation therapy and immunotherapy (tumor vaccine, CAR-T, oncolytic virus, targeting CSCs–immune cell crosstalk and immunity checkpoint inhibitor). We highlight the potential of immunity therapy and its combinational anti-CSC therapies, which are composed of different drugs working in different mechanisms.

Hepatic Cancer Stem Cells: Molecular Mechanisms, Therapeutic Implications, and Circulating Biomarkers

Hepatocellular carcinoma (HCC) is one of the deadliest cancers. HCC is associated with multiple risk factors and is characterized by a marked tumor heterogeneity that makes its molecular classification difficult to apply in the clinics. The lack of circulating biomarkers for the diagnosis, prognosis, and prediction of response to treatments further undermines the possibility of developing personalized therapies. Accumulating evidence affirms the involvement of cancer stem cells (CSCs) in tumor heterogeneity, recurrence, and drug resistance. Owing to the contribution of CSCs to treatment failure, there is an urgent need to develop novel therapeutic strategies targeting, not only the tumor bulk, but also the CSC subpopulation. Clarification of the molecular mechanisms influencing CSC properties, and the identification of their functional roles in tumor progression, may facilitate the discovery of novel CSC-based therapeutic targets to be used alone, or in combination with current anticancer agents, for the treatment of HCC. Here, we review the driving forces behind the regulation of liver CSCs and their therapeutic implications. Additionally, we provide data on their possible exploitation as prognostic and predictive biomarkers in patients with HCC.

Immunotherapy against programmed death-1/programmed death ligand 1 in hepatocellular carcinoma: Importance of molecular variations, cellular heterogeneity, and cancer stem cells

Hepatocellular carcinoma (HCC) is a heterogeneous malignancy related to diverse etiological factors. Different oncogenic mechanisms and genetic variations lead to multiple HCC molecular classifications. Recently, an immune-based strategy using immune checkpoint inhibitors (ICIs) was presented in HCC therapy, especially with ICIs against the programmed death-1 (PD-1) and its ligand PD-L1. However, despite the success of anti-PD-1/PD-L1 in other cancers, a substantial proportion of HCC patients fail to respond. In this review, we gather current information on biomarkers of anti-PD-1/PD-L1 treatment and the contribution of HCC heterogeneity and hepatic cancer stem cells (CSCs). Genetic variations of PD-1 and PD-L1 are associated with chronic liver disease and progression to cancer. PD-L1 expression in tumoral tissues is differentially expressed in CSCs, particularly in those with a close association with the tumor microenvironment. This information will be beneficial for the selection of patients and the management of the ICIs against PD-1/PD-L1.

Cancer Stem Cells: Emerging Key Players in Immune Evasion of Cancers

Cancer stem cells (CSCs) are subpopulations of undifferentiated cancer cells within the tumor bulk that are responsible for tumor initiation, recurrence and therapeutic resistance. The enhanced ability of CSCs to give rise to new tumors suggests potential roles of these cells in the evasion of immune surveillance. A growing body of evidence has described the interplay between CSCs and immune cells within the tumor microenvironment (TME). Recent data have shown the pivotal role of some major immune cells in driving the expansion of CSCs, which concurrently elicit evasion of the detection and destruction of various immune cells through a number of distinct mechanisms. Here, we will discuss the role of immune cells in driving the stemness of cancer cells and provide evidence of how CSCs evade immune surveillance by exerting their effects on tumor-associated macrophages (TAMs), dendritic cells (DCs), myeloid-derived suppressor cells (MDSCs), T-regulatory (Treg) cells, natural killer (NK) cells, and tumor-infiltrating lymphocytes (TILs). The knowledge gained from the interaction between CSCs and various immune cells will provide insight into the mechanisms by which tumors evade immune surveillance. In conclusion, CSC-targeted immunotherapy emerges as a novel immunotherapy strategy against cancer by disrupting the interaction between immune cells and CSCs in the TME.

The Role of Notch3 Signaling in Cancer Stemness and Chemoresistance: Molecular Mechanisms and Targeting Strategies

Aberrant Notch signaling profoundly affects cancer progression. Especially the Notch3 receptor was found to be dysregulated in cancer, where its expression is correlated with worse clinicopathological features and poor prognosis. The activation of Notch3 signaling is closely related to the activation of cancer stem cells (CSCs), a small subpopulation in cancer that is responsible for cancer progression. In addition, Notch3 signaling also contributes to tumor chemoresistance against several drugs, including doxorubicin, platinum, taxane, epidermal growth factor receptor (EGFR)–tyrosine kinase inhibitors (TKIs) and gemcitabine, through complex mechanisms. In this review, we mainly focus on discussing the molecular mechanisms by which Notch3 modulates cancer stemness and chemoresistance, as well as other cancer behaviors including metastasis and angiogenesis. What’s more, we propose potential treatment strategies to block Notch3 signaling, such as non-coding RNAs, antibodies and antibody-drug conjugates, providing a comprehensive reference for research on precise targeted cancer therapy.

Tumor-associated macrophages-mediated CXCL8 infiltration enhances breast cancer metastasis: Suppression by Danirixin

Breast cancer is the most frequent cancer among females and the second most common cause of cancer deaths worldwide. Tumor-associated macrophages (TAMs) are the most abundant immune cell population in the tumor microenvironment, including breast cancer. Breast cancer stem cells (BCSCs) play an important role in regulating breast cancer growth and metastasis, which still remains an obstacle for successful treatment of breast cancer and requires further investigation, as well as the potential therapeutic strategies. Cytokine array validated that C-X-C motif chemokine ligand 8 (CXCL8) is a pivotal chemokine secreted by TAMs, and CXCL8 could enhance breast cancer migration, invasion ability, and epithelial-mesenchymal transition (EMT) in both animal and human breast cancer. In this study, the clinical data firstly indicated that high CXCL8 expression was significantly associated with metastasis and tumor growth in breast cancer patients. Then, we showed that TAMs-released CXCL8 could markedly elevate the migration, invasion and EMT events in breast cancer cells, as well as the self-renewal of BCSCs in vitro. These processes were markedly abrogated by the treatment of Danirixin, a reversible and selective antagonist of CXC chemokine receptor 2 (CXCR2). Consistently, the in vivo analysis confirmed that CXCL8 suppression using Danirixin effectively reduced the tumor growth, lung metastasis and repressed the self-renewal of BCSCs. Collectively, TAMs/CXCL8 could enhance BCSCs self-renewal and breast cancer metastasis, and these effects could be markedly abolished by Danirixin treatment, suppressing breast cancer progression consequently. Therefore, Danirixin could be considered as a novel and effective therapeutic strategy for breast cancer treatment without obvious toxicity to major organs.

PD-1/PD-L1 immune checkpoints: Tumor vs atherosclerotic progression

Immunotherapy has become one of the most attraction cancer therapy strategies. The PD-1/PD-L1 pathway plays key roles in immune responses and autoimmunity by regulating T cell activity. Overactivation of this pathway dampens T cell and immune function, which allows tumor cells immune escape. Antibody or inhibitors of PD-1/PD-L1 immune targets have been implicated in clinic anti-cancer therapy and gain great clinic outcoming for their high efficiency. However, recent studies showed that the PD-1/PD-L1 immunotherapy in some tumor patients was found to accelerate T cell-driven inflammatory and the progression of atherosclerotic lesions. This article reviews the research progression of PD-1/PD-L1 in tumors and atherosclerosis, and the possible mechanisms of anti-PD-1/PD-L1 immunotherapy increasing the risk of atherosclerotic lesions.