Overcoming resistance to chemotherapies remains a major unmet need for cancers, such as triple-negative breast cancer (TNBC). Therefore, mechanistic studies to provide insight for drug development ...are urgently needed to overcome TNBC therapy resistance. Recently, an important role of fatty acid β-oxidation (FAO) in chemoresistance has been shown. But how FAO might mitigate tumor cell apoptosis by chemotherapy is unclear. Here, we show that elevated FAO activates STAT3 by acetylation via elevated acetyl-coenzyme A (CoA). Acetylated STAT3 upregulates expression of long-chain acyl-CoA synthetase 4 (ACSL4), resulting in increased phospholipid synthesis. Elevating phospholipids in mitochondrial membranes leads to heightened mitochondrial integrity, which in turn overcomes chemotherapy-induced tumor cell apoptosis. Conversely, in both cultured tumor cells and xenograft tumors, enhanced cancer cell apoptosis by inhibiting ASCL4 or specifically targeting acetylated-STAT3 is associated with a reduction in phospholipids within mitochondrial membranes. This study demonstrates a critical mechanism underlying tumor cell chemoresistance.
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•Fatty acid oxidation increases acetylated-STAT3 in chemoresistant TNBC cells•Acetylated STAT3 upregulates ACSL4 to increase phospholipid biogenesis•Increased phospholipids elevate mitochondrial membrane potential•Increased mitochondrial membrane potential resists paclitaxel-induced apoptosis
Li et al. demonstrate that FAO mediates chemoresistance in part by acetylating STAT3 through increased acetyl-CoA. Acetylated STAT3 upregulates long-chain acyl-CoA synthetase 4 (ACSL4). Upregulated ACSL4 enhances phospholipid synthesis, which is accompanied by elevated mitochondrial membrane phospholipid levels and strengthened mitochondrial membrane potential. This leads to compromised mitochondrial apoptotic signaling.
Phenotypic plasticity, the ability of cells to reversibly alter their phenotypes in response to signals, presents a significant clinical challenge to treating solid tumors. Tumor cells utilize ...phenotypic plasticity to evade therapies, metastasize, and colonize distant organs. As a result, phenotypic plasticity can accelerate tumor progression. A well‐studied example of phenotypic plasticity is the bidirectional conversions among epithelial, mesenchymal, and hybrid epithelial/mesenchymal (E/M) phenotype(s). These conversions can alter a repertoire of cellular traits associated with multiple hallmarks of cancer, such as metabolism, immune evasion, invasion, and metastasis. To tackle the complexity and heterogeneity of these transitions, mathematical models have been developed that seek to capture the experimentally verified molecular mechanisms and act as ‘hypothesis‐generating machines’. Here, we discuss how these quantitative mathematical models have helped us explain existing experimental data, guided further experiments, and provided an improved conceptual framework for understanding how multiple intracellular and extracellular signals can drive E/M plasticity at both the single‐cell and population levels. We also discuss the implications of this plasticity in driving multiple aggressive facets of tumor progression.
In this review, we highlight how an integrated theoretical‐experimental approach has driven a better understanding of epithelial/mesenchymal (E/M) plasticity. Through multiple examples presented in a pedagogical manner, we discuss how quantitative mathematical models focused on signaling networks and/or cellular mechanics have acted as hypothesis‐generating tools to guide further experiments to decode multiple aspects associated with E/M plasticity, such as stemness, motility, immune evasion, and drug resistance. We also suggest what other open questions in the regulation of epithelial‐mesenchymal transition and mesenchymal‐epithelial transition can benefit from bidirectional communication among quantitative mathematical in silico models and diverse in vitro and in vivo experiments.
Metastasis remains the cause of over 90% of cancer-related deaths. Cells undergoing metastasis use phenotypic plasticity to adapt to their changing environmental conditions and avoid therapy and ...immune response. Reversible transitions between epithelial and mesenchymal phenotypes – epithelial–mesenchymal transition (EMT) and its reverse mesenchymal–epithelial transition (MET) – form a key axis of phenotypic plasticity during metastasis and therapy resistance. Recent studies have shown that the cells undergoing EMT/MET can attain one or more hybrid epithelial/mesenchymal (E/M) phenotypes, the process of which is termed as partial EMT/MET. Cells in hybrid E/M phenotype(s) can be more aggressive than those in either epithelial or mesenchymal state. Thus, it is crucial to identify the factors and regulatory networks enabling such hybrid E/M phenotypes. Here, employing an integrated computational-experimental approach, we show that the transcription factor nuclear factor of activated T-cell (NFATc) can inhibit the process of complete EMT, thus stabilizing the hybrid E/M phenotype. It increases the range of parameters enabling the existence of a hybrid E/M phenotype, thus behaving as a phenotypic stability factor (PSF). However, unlike previously identified PSFs, it does not increase the mean residence time of the cells in hybrid E/M phenotypes, as shown by stochastic simulations; rather it enables the co-existence of epithelial, mesenchymal and hybrid E/M phenotypes and transitions among them. Clinical data suggests the effect of NFATc on patient survival in a tissue-specific or context-dependent manner. Together, our results indicate that NFATc behaves as a non-canonical PSF for a hybrid E/M phenotype.
Aberrant activation of epithelial-mesenchymal transition (EMT) in carcinoma cells
contributes to increased migration and invasion, metastasis, drug resistance,
and tumor-initiating capacity. EMT is ...not always a binary process; rather, cells
may exhibit a hybrid epithelial/mesenchymal (E/M) phenotype. ZEB1—a key
transcription factor driving EMT—can both induce and maintain a
mesenchymal phenotype. Recent studies have identified two novel autocrine
feedback loops utilizing epithelial splicing regulatory protein 1 (ESRP1),
hyaluronic acid synthase 2 (HAS2), and CD44 which maintain high levels of ZEB1.
However, how the crosstalk between these feedback loops alters the dynamics of
epithelial-hybrid-mesenchymal transition remains elusive. Here, using an
integrated theoretical-experimental framework, we identify that these feedback
loops can enable cells to stably maintain a hybrid E/M phenotype. Moreover,
computational analysis identifies the regulation of ESRP1 as a crucial node, a
prediction that is validated by experiments showing that knockdown of ESRP1 in
stable hybrid E/M H1975 cells drives EMT. Finally, in multiple breast cancer
datasets, high levels of ESRP1, ESRP1/HAS2, and ESRP1/ZEB1 correlate with poor
prognosis, supporting the relevance of ZEB1/ESRP1 and ZEB1/HAS2 axes in tumor
progression. Together, our results unravel how these interconnected feedback
loops act in concert to regulate ZEB1 levels and to drive the dynamics of
epithelial-hybrid-mesenchymal transition.
Activation of the NRF2 pathway through gain-of-function mutations or loss-of-function of its suppressor KEAP1 is a frequent finding in lung cancer. NRF2 activation has been reported to alter the ...tumor microenvironment. Here, we demonstrated that NRF2 alters tryptophan metabolism through the kynurenine pathway that is associated with a tumor-promoting, immune suppressed microenvironment. Specifically, proteomic profiles of 47 lung adenocarcinoma (LUAD) cell lines (11
mutant and 36
wild-type) revealed the tryptophan-kynurenine enzyme kynureninase (KYNU) as a top overexpressed protein associated with activated NRF2. The siRNA-mediated knockdown of
, the gene encoding for NRF2, or activation of the NRF2 pathway through siRNA-mediated knockdown of
or via chemical induction with the NRF2-activator CDDO-Me confirmed that NRF2 is a regulator of KYNU expression in LUAD. Metabolomic analyses confirmed KYNU to be enzymatically functional. Analysis of multiple independent gene expression datasets of LUAD, as well as a LUAD tumor microarray demonstrated that elevated KYNU was associated with immunosuppression, including potent induction of T-regulatory cells, increased levels of PD1 and PD-L1, and resulted in poorer survival. Our findings indicate a novel mechanism of NRF2 tumoral immunosuppression through upregulation of KYNU.
New strategies that improve median survivals of only ~15–20 months for glioblastoma (GBM) with the current standard of care (SOC) which is concurrent temozolomide (TMZ) and radiation (XRT) treatment ...are urgently needed. Inhibition of polo-like kinase 1 (PLK1), a multifunctional cell cycle regulator, overexpressed in GBM has shown therapeutic promise but has never been tested in the context of SOC. Therefore, we examined the mechanistic and therapeutic impact of PLK1 specific inhibitor (volasertib) alone and in combination with TMZ and/or XRT on GBM cells. We quantified the effects of volasertib alone and in combination with TMZ and/or XRT on GBM cell cytotoxicity/apoptosis, mitochondrial membrane potential (MtMP), reactive oxygen species (ROS), cell cycle, stemness, DNA damage, DNA repair genes, cellular signaling and in-vivo tumor growth. Volasertib alone and in combination with TMZ and/or XRT promoted apoptotic cell death, altered MtMP, increased ROS and G2/M cell cycle arrest. Combined volasertib and TMZ treatment reduced side population (SP) indicating activity against GBM stem-like cells. Volasertib combinatorial treatment also significantly increased DNA damage and reduced cell survival by inhibition of DNA repair gene expression and modulation of ERK/MAPK, AMPK and glucocorticoid receptor signaling. Finally, as observed in-vitro, combined volasertib and TMZ treatment resulted in synergistic inhibition of tumor growth in-vivo. Together these results identify new mechanisms of action for volasertib that provide a strong rationale for further investigation of PLK1 inhibition as an adjunct to current GBM SOC therapy.
The current COVID-19 pandemic has affected most severely people with old age, or with comorbidities like hypertension, diabetes mellitus, and cancer. Cancer patients are twice more likely to contract ...the disease because of the malignancy or treatment-related immunosuppression; hence identification of the vulnerable population among these patients is essential.
We took a bioinformatics approach to analyze the gene and protein expression data of these coronavirus receptors (DPP4, ANPEP, ENPEP, TMPRSS2) in human normal and cancer tissues of multiple organs including the brain, liver, kidney, heart, lung, skin, GI tract, pancreas, endocrine tissues, and the reproductive organs. RNA-Seq data from The Cancer Genome Atlas (TCGA) and GTeX databases were used for extensive profiling analysis of these receptors across 9,736 tumors and 8,587 normal tissues comparing coronavirus receptors. Protein expression from immunohistochemistry data was assessed from The Human Protein Atlas database including 144 samples, corresponding to 48 different normal human tissue types, and 432 tumor samples from 216 different cancer patients. The correlations between immune cell infiltration, chemokine, and cytokines were investigated via Tumor Immune Estimation Resource (TIMER) and TCGA.
We found that among all, renal tumor and normal tissues exhibited increased levels of ACE2, DPP4, ANPEP, and ENPEP. Our results revealed that TMPRSS2 may not be the co-receptor for coronavirus infection in renal carcinoma patients. The other receptors DPP4, ANPEP, and ENPEP may act as the compensatory receptor proteins to help ACE2. The receptors' expression levels were variable in different tumor stage, molecular, and immune subtypes of renal carcinoma. Intriguingly, in clear cell renal cell carcinomas, coronavirus receptors were associated with high immune infiltration, markers of immunosuppression, and T cell exhaustion.
Our study indicates that CoV receptors may play an important role in modulating the immune infiltrate and hence cellular immunity in renal carcinoma. As our current knowledge of pathogenic mechanisms will improve, it may help us in designing focused therapeutic approaches.
Neutrophil elastase (NE) can be rapidly taken up by tumor cells that lack endogenous NE expression, including breast cancer, which results in cross-presentation of PR1, an NE-derived ...HLA-A2-restricted peptide that is an immunotherapy target in hematological and solid tumor malignancies. The mechanism of NE uptake, however, remains unknown. Using the mass spectrometry-based approach, we identify neuropilin-1 (NRP1) as a NE receptor that mediates uptake and PR1 cross-presentation in breast cancer cells. We demonstrated that soluble NE is a specific, high-affinity ligand for NRP1 with a calculated Kd of 38.7 nm. Furthermore, we showed that NRP1 binds to the RRXR motif in NE. Notably, NRP1 knockdown with interfering RNA or CRISPR-cas9 system and blocking using anti-NRP1 antibody decreased NE uptake and, subsequently, susceptibility to lysis by PR1-specific cytotoxic T cells. Expression of NRP1 in NRP1-deficient cells was sufficient to induce NE uptake. Altogether, because NRP1 is broadly expressed in tumors, our findings suggest a role for this receptor in immunotherapy strategies that target cross-presented antigens.
We previously demonstrated that nuclear and cytoplasmic accumulation of the intracellular domain (Ep-ICD) of epithelial cell adhesion molecule (EpCAM) accompanied by a reciprocal reduction of its ...extracellular domain (EpEx), occurs in aggressive thyroid cancers. This study was designed to determine whether similar accumulation of Ep-ICD is a common event in other epithelial cancers.
Ten epithelial cancers were immunohistochemically analyzed using Ep-ICD and EpEx domain-specific antibodies. The subcellular localization of EpEx and Ep-ICD in the human colon adenocarcinoma cell line CX-1 was observed using immunofluorescence. Nuclear and cytoplasmic Ep-ICD expression was increased in cancers of the breast (31 of 38 tissues, 82%), prostate (40 of 49 tissues, 82%), head and neck (37 of 57 tissues, 65%) and esophagus (17 of 46 tissues, 37%) compared to their corresponding normal tissues that showed membrane localization of the protein. Importantly, Ep-ICD was not detected in the nuclei of epithelial cells in most normal tissues. High nuclear and cytoplasmic Ep-ICD accumulation also occurred in the other six epithelial cancer types analyzed - lung, colon, liver, bladder, pancreatic, and ovarian. A concomitant reduction in membrane EpEx expression was observed in a subset of all cancer types. Receiver operating characteristic curve analysis revealed nuclear Ep-ICD distinguished breast cancers with 82% sensitivity and 100% specificity and prostate cancers with 82% sensitivity and 78% specificity. Similar findings were observed for cytoplasmic accumulation of Ep-ICD in these cancers. We provide clinical evidence of increased nuclear and cytoplasmic Ep-ICD accumulation and a reduction in membranous EpEx in these cancers.
Increased nuclear and cytoplasmic Ep-ICD was observed in all epithelial cancers analyzed and distinguished them from normal tissues with high-sensitivity, specificity, and AUC. Development of a robust high throughput assay for Ep-ICD will facilitate the determination of its diagnostic, prognostic and therapeutic relevance in epithelial cancers.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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