Increased expression of MyD88 and association with paclitaxel resistance in breast cancer

MyD88 and Its Inhibitors in Cancer: Prospects and Challenges

The interplay between the immune system and cancer underscores the central role of immunotherapy in cancer treatment. In this context, the innate immune system plays a critical role in preventing tumor invasion. Myeloid differentiation factor 88 (MyD88) is crucial for innate immunity, and activation of MyD88 promotes the production of inflammatory cytokines and induces infiltration, polarization, and immune escape of immune cells in the tumor microenvironment. Additionally, abnormal MyD88 signaling induces tumor cell proliferation and metastasis, which are closely associated with poor prognosis. Therefore, MyD88 could serve as a novel tumor biomarker and is a promising target for cancer therapy. Current strategies targeting MyD88 including inhibition of signaling pathways and protein multimerization, have made substantial progress, especially in inflammatory diseases and chronic inflammation-induced cancers. However, the specific role of MyD88 in regulating tumor immunity and tumorigenic mechanisms remains unclear. Therefore, this review describes the involvement of MyD88 in tumor immune escape and disease therapy. In addition, classical and non-classical MyD88 inhibitors were collated to provide insights into potential cancer treatment strategies. Despite several challenges and complexities, targeting MyD88 is a promising avenue for improving cancer treatment and has the potential to revolutionize patient outcomes.

MyD88 signaling pathways: role in breast cancer

MyD88 plays a central role in breast cancer, exerting a multitude of effects that carry substantial implications. Elevated MyD88 expression is closely associated with aggressive tumor characteristics, suggesting its potential as a valuable prognostic marker and therapeutic target. MyD88 exerts influence over several critical aspects of breast cancer, including metastasis, recurrence, drug resistance, and the regulation of cancer stem cell properties. Furthermore, MyD88 modulates the release of inflammatory and chemotactic factors, thereby shaping the tumor's immune microenvironment. Its role in immune response modulation underscores its potential in influencing the dynamic interplay between tumors and the immune system. MyD88 primarily exerts intricate effects on tumor progression through pathways such as Phosphoinositide 3-kinases/Protein kinase B (PI3K/Akt), Toll-like Receptor/Nuclear Factor Kappa B (TLR/NF-κB), and others. Nevertheless, in-depth research is essential to unveil the precise mechanisms underlying the diverse roles of MyD88 in breast cancer. The translation of these findings into clinical applications holds great promise for advancing precision medicine approaches for breast cancer patients, ultimately enhancing prognosis and enabling the development of more effective therapeutic strategies.

MyD88 dimerization inhibitor ST2825 targets the aggressiveness of synovial fibroblasts in rheumatoid arthritis patients

BACKGROUND

Dimerization of the myeloid differentiation primary response 88 protein (MyD88) plays a pivotal role in the exacerbated response to innate immunity-dependent signaling in rheumatoid arthritis (RA). ST2825 is a highly specific inhibitor of MyD88 dimerization, previously shown to inhibit the pro-inflammatory gene expression in peripheral blood mononuclear cells from RA patients (RA PBMC). In this study, we elucidated the effect of disrupting MyD88 dimerization by ST2825 on the pathological properties of synovial fibroblasts from RA patients (RA SFs).

METHODS

RA SFs were treated with varying concentrations of ST2825 in the presence or absence of bacterial lipopolysaccharides (LPS) to activate innate immunity-dependent TLR signaling. The DNA content of the RA SFs was quantified by imaging cytometry to investigate the effect of ST2825 on different phases of the cell cycle and apoptosis. RNA-seq was used to assess the global response of the RA SF toward ST2825. The invasiveness of RA SFs in Matrigel matrices was measured in organoid cultures. SFs from osteoarthritis (OA SFs) patients and healthy dermal fibroblasts were used as controls.

RESULTS

ST2825 reduced the proliferation of SFs by arresting the cells in the G0/G1 phase of the cell cycle. In support of this finding, transcriptomic analysis by RNA-seq showed that ST2825 may have induced cell cycle arrest by primarily inhibiting the expression of critical cell cycle regulators Cyclin E2 and members of the E2F family transcription factors. Concurrently, ST2825 also downregulated the genes encoding for pain, inflammation, and joint catabolism mediators while upregulating the genes required for the translocation of nuclear proteins into the mitochondria and members of the mitochondrial respiratory complex 1. Finally, we demonstrated that ST2825 inhibited the invasiveness of RA SFs, by showing decreased migration of LPS-treated RA SFs in spheroid cultures.

CONCLUSIONS

The pathological properties of the RA SFs, in terms of their aberrant proliferation, increased invasiveness, upregulation of pain and inflammation mediators, and disruption of mitochondrial homeostasis, were attenuated by ST2825 treatment. Taken together with the previously reported anti-inflammatory effects of ST2825 in RA PBMC, this study strongly suggests that targeting MyD88 dimerization could mitigate both systemic and synovial pathologies in a variety of inflammatory arthritic diseases.

Synthesis of small molecules targeting paclitaxel-induced MyD88 expression in triple-negative breast cancer cell lines

Acquired paclitaxel (PTX) chemoresistance in triple-negative breast cancer (TNBC) can be inferred from the overexpression of toll-like receptor 4 (TLR4) and myeloid differentiation primary response 88 (MyD88) proteins and the activation of the TLR4/MyD88 cascading signalling pathway. Finding a new inhibitor that can attenuate the activation of this pathway is a novel strategy for reducing PTX chemoresistance. In this study, a series of small molecule compounds were synthesised and tested in combination with PTX against TNBC cells. The trimethoxy-substituted compound significantly decreased MyD88 overexpression and improved PTX activity in MDA-MB-231^TLR4+ cells but not in HCC^TLR4- cells. On the contrary, the trifluoromethyl-substituted compound with PTX synergistically improved the growth inhibition in both TNBC subtypes. The fluorescence titrations indicated that both compounds could bind with MD2 with good and comparable binding affinities. This was further supported by docking analysis, in which both compounds fit perfectly well and form some critical binding interactions with MD2, an essential lipid-binding accessory to TLR4 involved in activating the TLR-4/MyD88-dependent pathway.

Resistance to Intervention: Paclitaxel in Breast Cancer

Breast cancer stands as the most prevalent cancer in women globally, and contributes to the highest percentage of mortality due to cancer-related deaths in women. Paclitaxel (PTX) is heavily relied on as a frontline chemotherapy drug in breast cancer treatment, especially in advanced metastatic cancer. Generation of resistance to PTX often derails clinical management and adversely affects patient outcomes. Understanding the molecular mechanism of PTX resistance is necessary to device methods to aid in overcoming the resistance. Recent studies exploring the mechanism of development of PTX resistance have led to unveiling of a range novel therapeutic targets. PTX resistance pathways that involve major regulatory proteins/RNAs like RNF8/Twist/ROR1, TLR, ErbB3/ErbB2, BRCA1- IRIS, MENA, LIN9, MiRNA, FoxM1 and IRAK1 have expanded the complexity of resistance mechanisms, and brought newer insights into the development of drug targets. These resistance-related targets can be dealt with synthetic/natural therapeutics in combination with PTX. The present review encompasses the recent understanding of PTX resistance mechanisms in breast cancer and possible therapeutic combinations to overcome resistance.

Kinase shRNA screening reveals that TAOK3 enhances microtubule-targeted drug resistance of breast cancer cells via the NF-κB signaling pathway

BACKGROUND

Chemotherapy is currently one of the most effective treatments for advanced breast cancer. Anti-microtubule agents, including taxanes, eribulin and vinca-alkaloids are one of the primary major anti-breast cancer chemotherapies; however, chemoresistance remains a problem that is difficult to solve. We aimed to discover novel candidate protein targets to combat chemoresistance in breast cancer.

METHODS

A lentiviral shRNA-based high-throughput screening platform was designed and developed to screen the global kinome to find new therapeutic targets in paclitaxel-resistant breast cancer cells. The phenotypes were confirmed with alternative expression in vitro and in vivo. Molecular mechanisms were investigated using global phosphoprotein arrays and expression microarrays. Global microarray analysis was performed to determine TAOK3 and genes that induced paclitaxel resistance.

RESULTS

A serine/threonine kinase gene, TAOK3, was identified from 724 screened kinase genes. TAOK3 shRNA exhibited the most significant reduction in IC50 values in response to paclitaxel treatment. Ectopic downregulation of TAOK3 resulted in paclitaxel-resistant breast cancer cells sensitize to paclitaxel treatment in vitro and in vivo. The expression of TAOK3 also was correlated to sensitivity to two other anti-microtubule drugs, eribulin and vinorelbine. Our TAOK3-modulated microarray analysis indicated that NF-κB signaling played a major upstream regulation role. TAOK3 inhibitor, CP43, and shRNA of NF-κB both reduced the paclitaxel resistance in TAOK3 overexpressed cells. In clinical microarray databases, high TAOK3 expressed breast cancer patients had poorer prognoses after adjuvant chemotherapy.

CONCLUSIONS

Here we identified TAOK3 overexpression increased anti-microtubule drug resistance through upregulation of NF-κB signaling, which reduced cell death in breast cancer. Therefore, inhibition of the interaction between TAOK3 and NF-κB signaling may have therapeutic implications for breast cancer patients treated with anti-microtubule drugs. Video abstract.

The MyD88 inhibitor TJ-M2010-2 suppresses proliferation, migration and invasion of breast cancer cells by regulating MyD88/GSK-3β and MyD88/NF-κB signalling pathways

MyD88 has been implicated in the tumourigenesis, metastasis and recurrence of breast cancer (BC). Here we utilized TJ-M2010-2 (TJ), an inhibitor of MyD88 homodimerimerization, and siMyD88 to suppress the function of MyD88 in MCF-7 and MDA-MB-231 cells. BC cells were treated in vitro and xenografted into nude mice to generate a model in vivo. TJ inhibited BC cell growth by impeding proliferation rather than by promoting apoptosis in vitro. Additionally, TJ and siMyD88 significantly attenuated cell migration and invasion, inhibited EMT-like progression and reduced cytokine (IL-6, IL-8, TGF-β1 and TNF-α) secretion induced by LPS. In vivo, TJ significantly hindered tumour growth in mice. Notably, TJ also decreased the secretion of IL-6, IL-8, TGF-β1, and TNF-α and M2 macrophage infiltration in the tumour microenvironment. The expression of MyD88, TRAF6, NF-κB p65, Snail, MMP-2, MMP-9, p-GSK-3β and p-Akt was significantly downregulated by TJ in BC cells and tumour tissues. Collectively, these results suggest that a MyD88 inhibitor (TJ) may be a promising therapeutic modality for treating BC patients.

MicroRNA-4317 predicts the prognosis of breast cancer and inhibits tumor cell proliferation, migration, and invasion

Previous researches have indicated that miR-4317 was aberrantly expressed in several tumors. However, the potential role of miR-4317 in breast cancer is still unclear. The aim of this study was to investigate the potential role of miR-4317 in breast cancer. The relative expression levels of miR-4317 were detected in breast cancer tissues and cell lines using qRT-PCR analysis. The Kaplan-Meier survival curve and multivariate Cox regression analyses were used to investigate the prognostic significance of miR-4317 in breast cancer. CCK-8 and Transwell assays were performed to evaluate the effects of miR-4317 on cell proliferation, migration, and invasion. The results showed that miR-4317 expression was decreased in breast cancer tissues and cell lines. Downregulation of miR-4317 was significantly associated with lymph node metastasis, TNM stage, and poor prognosis. Overexpression of miR-4317 inhibited proliferation, migration, and invasion of breast cancer cells, while downregulation of miR-4317 exhibited the opposite effects. MYD88 may be a direct target of miR-4317. The results suggest miR-4317 may play a tumor suppressor role in breast cancer and inhibit proliferation, migration, and invasion of breast cancer cells by targeting MYD88. The findings provide novel evidence of miR-4317 as a potential prognostic biomarker and therapeutic target for breast cancer.

Promoter methylation status of ASC/TMS1/PYCARD is associated with decreased overall survival and TNM status in patients with early stage non-small cell lung cancer (NSCLC)

BACKGROUND

Lung cancer is the leading cause of cancer-related death worldwide, with 5-year overall survival less than 15%. Therefore, it is essential to find biomarkers for early detection and prognosis. Aberrant DNA methylation is a common feature of human cancers and its utility is already recognized in cancer management. The aim of this study was to explore the diagnostic and prognostic value of the promoter methylation status of the ASC/TMS1/PYCARD and MyD88 genes, key adaptor molecules in the activation of the innate immune response and apoptosis pathways.

METHODS

A total of 50 non-small cell lung cancer (NSCLC) patients were enrolled in the study. Methylation of bisulphite converted DNA was quantified by pyrosequencing in fresh frozen malignant tissues and adjacent non-malignant tissues. Associations between methylation and lung function, tumor grade and overall survival were evaluated using receiver-operating characteristics (ROC) analysis and statistical tests of hypothesis.

RESULTS

Methylation level of tested genes is generally low but significantly decreased in tumor tissues (ASC/TMS1/PYCARD, P<0.0001; MyD88, P<0.0002), which correlates with increased protein expression. Three CpG sites were identified as promising diagnostic marker candidates; CpG11 (-63 position) in ASC/TMS1/PYCARD and CpG1 (-253 position) and 2 (-265 position) in MyD88. The association study showed that the methylation status of the ASC/TMS1 CpG4 site (-34 position) in malignant and non-malignant tissues is associated with the overall survival (P=0.019) and the methylation status of CpG8 site (-92 position) is associated with TNM-stage (P=0.011).

CONCLUSIONS

The methylation status of the ASC/TMS1/PYCARD and MyD88 promoters are promising prognostic biomarker candidates. However, presented results should be considered as a preliminary and should be confirmed on the larger number of the samples.

Ursolic Acid Reverses the Chemoresistance of Breast Cancer Cells to Paclitaxel by Targeting MiRNA-149-5p/MyD88

Paclitaxel (PTX) is widely used as a front-line chemotherapy for breast cancer treatment. However, its clinical applications are limited by the development of chemoresistance. The objective of this study was to investigate the reversal effects of ursolic acid (UA) on PTX resistance and the possible mechanisms in breast cancer. The role of miRNA-149-5p/MyD88 in the regulation of PTX resistance was investigated by the transfection of breast cancer cells with MDA-MB-231 (231) and MDA-MB-231/PTX-resistance (231/PTX) with lentiviruses carrying the MyD88 gene, shRNA specific for MyD88, the miR-149-5p gene, and shRNA specific for miR-149-5p. The PTX sensitivity was assessed by a CCK-8 assay. qRT-PCR and Western blot analyses were used to detect changes in the mRNA and protein levels. Flow cytometry was used to measure the rate of cell apoptosis. A luciferase activity assay was used to detect the binding site of miR-149-5p on the 3'UTR of MyD88. 231/PTX cells were injected into the flanks of female athymic nude mice, and the mice were randomly divided into the five following groups: PBS, PTX (low), PTX (high), UA, and PTX+UA. Our data show that UA reversed the resistance of breast cancer 231/PTX cells to PTX in vitro and in vivo. UA treatment significantly increased the expression of miR-149-5p, which was lower in 231/PTX cells than in 231 cells. Furthermore, the overexpression of miR-149-5p increased the sensitivity of 231/PTX cells to PTX treatment, whereas the knockdown of the miR-149-5p gene attenuated the effects of UA on the regulation of PTX sensitivity. A luciferase assay demonstrated that miR-149-5p could directly regulate the transcriptional activity of MyD88, a known PTX-resistance gene, by targeting the 3'UTR of MyD88. Meanwhile, the downregulation of MyD88 through the overexpression of miR-149-5p or UA treatment inhibited the activation of the Akt signaling pathway in 231/PTX cells. Thus, our data indicate that UA can reverse PTX resistance by targeting the miRNA-149-5p/MyD88 axis in breast cancer cells.

An analysis of the expression and function of myeloid differentiation factor 88 in human osteosarcoma

The aim of the present study was to investigate the expression and function of myeloid differentiation factor 88 (MyD88) in osteosarcoma. Immunohistochemical staining was used to detect MyD88 protein in osteosarcoma tissues and matched normal bone tissues. The association between MyD88 expression and the clinical characteristics of patients with osteosarcoma was analyzed. Furthermore, survival analysis of patients with osteosarcoma was performed to study the association between MyD88 expression and patient prognosis. Finally, the effect of the MyD88 inhibitor, ST2825, on the proliferation and apoptosis of the human osteosarcoma cell line U2OS was examined. Additionally, cell proliferation, invasion and apoptosis were examined using an MTT assay, Transwell assay and Annexin V-fluorescein isothiocyanate staining kit, respectively. The expression of proteins associated with the NF-κB signaling pathway was analyzed by western blotting. The positive expression rate of MyD88 in osteosarcoma and normal bone tissues was 71.4 and 6.1%, respectively. Statistical analysis demonstrated that MyD88 was not associated with gender, age, histological type or tumor location, but that it was associated with Enneking stage and tumor metastasis (P<0.05). According to the survival analysis, patients with osteosarcoma in the high MyD88 expression group displayed a reduced overall survival rate (P<0.05). Furthermore, inhibition of MyD88 by ST2825 in U2OS cells resulted in a marked decrease in cellular proliferation and migration, and an increase in the rate of apoptosis (P<0.05). Notably, ST2825 significantly decreased cyclin D1, matrix metallopeptidase-9 and nucleus p65 expression, but increased cleaved-caspase 3 expression in ST2825-treated U2OS cells (P<0.05). The results of the present study indicated that MyD88 expression is associated with the progression of osteosarcoma and may be a potential therapeutic target for the treatment of osteosarcoma.

NT21MP negatively regulates paclitaxel-resistant cells by targeting miR‑155‑3p and miR‑155-5p via the CXCR4 pathway in breast cancer

Evidence has shown that microRNAs (miRNAs) are vital in cell growth, migration, and invasion by inhibiting their target genes. A previous study demonstrated that miRNA (miR)-155-3p and miR-155-5p exerted opposite effects on cell proliferation, apoptosis, migration and invasion in breast cancer cell lines. An miRNA microarray was used to show that miR-155-3p was downregulated whereas miR-155-5p was upregulated in paclitaxel-resistant (PR) cells compared with parental breast cancer cells. However, the role of miR-155 in breast cancer cell invasion and metastasis remains to be elucidated. A 21-residue peptide derived from the viral macrophage inflammatory protein II (NT21MP), competes with the ligand of CXC chemokine receptor 4 (CXCR4) and its ligand stromal cell-derived factor-1α, inducing cell apoptosis in breast cancer. The present study aimed to identify the underlying mechanism of action of miR-155-3p/5p and NT21MP in PR breast cancer cells. Quantitative polymerase chain reaction, western blotting, wound-healing, cell cycle and apoptosis assays, and Cell Counting kit-8 assay were used to achieve this goal. The combined overexpression of miR-155-3p with NT21MP decreased the migration and invasion ability and increased the number of apoptotic and arrested cells in the G0/G1 phase transition in vitro. The knockdown of miR-155-5p combined with NT21MP had a similar effect on PR breast cancer cells. Furthermore, the ectopic expression of their target gene myeloid differentiation primary response gene 88 (MYD88) or tumor protein 53-induced nuclear protein 1 (TP53INP1) combined with NT21MP enhanced the sensitivity of the breast cancer cells to paclitaxel. Taken together, these findings suggested that miR-155-3p/5p and their target genes MYD88 and TP53INP1 may serve as novel biomarkers for NT21MP therapy through the CXCR4 pathway for improving sensitivity to paclitaxel in breast cancer.

HDACI regulates the PI3K/Akt signaling pathway to reverse MCF-7/PTX resistance by inhibiting SET

The occurrence of chemoresistance greatly restricts the efficacy of antitumor drugs, and so novel agents are urgently needed to abrogate resistant phenotypes.