Recently, in a research report published in the international journal Developmental Cell, scientists from the Sanford Burnham Prebys Institute for Medical Discovery and other institutions discovered the reason why a type of colon cancer does not respond to immunotherapy. By targeting these factors that interfere with tumor treatment, it may be expected to help develop new methods that make cancer therapies more effective.
In the article, the researchers analyzed CMS4 colorectal cancer and proposed that cancer-related fibroblasts interfere with tumor treatment. CMS4 is one of the most malignant and difficult-to-treat colorectal cancers, and affects the health of nearly one-third of colorectal cancer patients. The researcher aims to determine how these cancer-related cells acquire the properties that promote their support for the carcinogenesis of nearby cells. This research consists of two important components. First, the researchers demonstrated in a obvious way how these cancer-related fibroblasts acquired the characteristics they possess. Second, the scientists confirmed that the findings of the study also apply to patients, and began to reveal how these findings are applied in the clinic.

In previous studies, researchers developed a mouse model that mimics CMS4 colorectal cancer. Like this type of colorectal cancer patients, researchers also found high concentrations of cancer related fibroblasts in the tumors of these mice The researchers used mouse models, cultured cells and organoids to study the relationship between cancer cells and cancer-related fibroblasts. They found that cancer cells can send signals to change the characteristics of fibroblasts. Appearing makes the tumor more aggressive and more invisible to the immune system. At the molecular level, it appears to reduce the level of PKCz protein, thereby increasing the level of SOX2 protein in fibroblasts. And then, SOX2 directly binds to the Sfrp1 / 2 promoter, causing the expression of Sfrp1 / 2. Interestingly, the inactivation of Sox2 or Sfrp1/2 in Cancer associated fibroblasts weakens the migration and invasion induction of colon cancer cells, as well as their tumorigenicity in vivo. Therefore, these changes seem to make fibroblasts friendly to promote tumor growth.

The researchers then used animal models to detect the behavior of the changed cells in the laboratory. They used single-cell RNA sequencing technology to confirm that the results observed in the laboratory were consistent with those observed in patient samples; the researchers said that they currently Understanding the communication mechanism between cancer cells and fibroblasts, they believe that the communication between the two allows fibroblasts to protect tumor cells from the human immune system in a unique way.

Subsequent research focuses on finding drugs or methods that can target fibroblasts that deprive the tumor of the protective environment. These drugs can be used in combination with immunotherapy to reduce the defense of fibroblasts and promote the function of immune cells activated by checkpoint blocking drugs. The results of this study may be applied to other cancer types, especially pancreatic cancer. Pancreatic cancer contains a large number of fibroblasts, which seems to make tumors resistant to immune therapy.

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Clinical studies have found that SARS-CoV-2 can affect multiple organs such as the lungs and kidneys, and can also cause neurological symptoms, including temporary loss of smell and taste. Therefore, the symptom spectrum of COVID-19 is quite complex. In 2003, a related coronavirus-SARS-CoV caused a much smaller outbreak. This may be because the virus infection was limited to the lower respiratory system, making the virus less spread. On the contrary, SARS-CoV-2 will also infect the upper respiratory system, including the nasal mucosa, so it will spread rapidly through active virus shedding (such as when sneezing).

The Leader into Cell

In order to infect humans, SARS-CoV-2 must first attach to the surface of human respiratory or intestinal epithelial cells. Once attached, the virus invades the cell and then replicates multiple copies of itself. These replicated viruses are released, leading to the spread of SARS-CoV-2. The process of SARS-CoV-2 attaching and invading human cells is accomplished by a viral protein called “spike” protein, and it has tissue chemotaxis. This tissue chemotaxis depends on whether there are docking points on the cell surface, the so-called receptors. These receptors allow the virus to dock and invade the cell. Interestingly, the researchers found that SARS-CoV, which uses ACE2 as the receptor like SARS-CoV-2, produces disease symptoms that are quite different from SARS-CoV-2.

Figure 1. SARS-CoV-2 supposed life cycle.

In order to understand the differences in the tropism of these tissues, these researchers observed the “spike protein” of SARS-CoV-2. The SARS-CoV-2 spike protein differs from its older relatives in that it inserts a furin cleavage site. Similar sequences have been found in the spike proteins of many other highly pathogenic human viruses. When a protein is cleaved by furin, a specific amino acid sequence is exposed at its cleaved end. Such a protein substrate that can be cleaved by furin has a characteristic pattern sequence known to bind to neuropilin on the cell surface.

Experiments using laboratory-cultured cells, artificial viruses that mimic SARS-CoV-2, and naturally-occurring viruses have shown that NRP1 can promote viral infections in the presence of ACE2. By specifically blocking NRP1 with antibodies, this viral infection can be suppressed. The relationship between the two is like the entrance and the guide. Among them, ACE2 is a door into the cell, and NRP1 may be an important factor that guides this virus to find and enter this door. Because the expression level of ACE2 in most cells is very low, it is not easy for the virus to find the door into the cell. Other factors such as NRP1 may be necessary to help this virus enter the cell.

Potential Access to the Nervous System
Given that loss of smell is one of the symptoms of COVID-19, and NRP1 is mainly found in the cell layer of the nasal cavity, these researchers examined tissue samples from dead patients. Other experiments in mice have shown that NRP1 can transport virus-sized nanoparticles from the nasal mucosa to the central nervous system. These nanoparticles are chemically engineered to bind to NRP1. In contrast to control particles that have no affinity for NRP1, when these NRP1-binding nanoparticles are applied to the noses of these mice, they reach the neurons and capillaries in the brain within a few hours.

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Existing clinical data indicate that fungal-derived polysaccharide β-glucan or Bacillus Calmette-Guerin-Bacillus vaccine (BCG) can promote the continuous enhanced response of bone marrow cells to secondary infection or inflammation. The process mediated by  transcription, epigenetic and metabolic reprogramming is called “trained innate immunity” or “innate immune memory”. Recently, scientists have discovered that by regulating the progenitor cells of myeloid cells in the bone marrow (BM), they have discovered that the trained immune system can exhibit long-term anti-cancer effects. In addition, agonist agents that help train the immune system exert anti-tumor activity. For example, BCG can be used to treat bladder cancer, and β-glucan is related to the efficacy of tumor immunotherapy. However, its specific role in tumors is still not clear. It is not well understood whether the potential tumor-modulating effects of agents such as β-glucan involve the induction of innate immune memory. In order to clarify the mechanism, scientists have recently explored the induction experiment by pretreatment of mice with β-glucan.

Studies have shown that neutrophils infiltrating solid tumors (called tumor-associated neutrophils (TANs)) can exhibit phenotypes with cytotoxic and anti-tumor properties (widely referred to as TAN1) or with Phenotype related to tumor progression (TAN2). Type I interferon (IFN) promotes TAN1, while transforming growth factor-β (TGF-β) is related to the differentiation of TAN2. In the context of anti-tumor immunity, neutrophils and granulocyte progenitor cells are the main cellular effectors of training immunity induced by β-glucan. Further studies have found that the anti-tumor effect of training immunity induced by β-glucan is related to the transcriptome and epigenetic rearrangement of granulocyte production, as well as neutrophil reprogramming and anti-tumor phenotype. This process is related to granulocyte production mediated by type I IFN signaling. Studies have shown that type I interferon plays a central role in granulocyte production and promotes the anti-tumor phenotype of neutrophils. Mice lacking IFN-β showed hindered bone marrow hematopoietic progenitor cell maturation, reduced blood neutrophil counts, and more aggressive tumor growth. After immune training, neutrophils can achieve subsequent anti-tumor properties through the generated ROS. The results showed that the adoptive transfer of neutrophils from β-glucan-trained mice to naive receptors inhibited the tumor growth of the latter in a ROS-dependent manner. Therefore, the anti-tumor effect of the trained granulocytes induced by β-glucan can be transmitted to unimmunized mice through bone marrow transplantation.

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In a new study, researchers from the University of California, San Diego School of Medicine found that cholesterol-25-hydroxylase (CH25H) can prevent the entry of  the coronavirus SARS-CoV-2 by removing cholesterol from the cell membrane.

According to existing research, it is known that the coronavirus will induce interferon (IFN) after infection. Interferon is an active protein (mainly glycoprotein) produced by monocytes and lymphocytes with multiple functions. They have broad-spectrum antiviral activities on the same cells, affecting cell growth, differentiation, and regulating immune function. After detecting the molecular pattern associated with viral infection, the IFN pathway is activated, prompting the further activation of hundreds of interferon-stimulating genes (ISG), thereby interfering with the virus life cycle process. Human type I interferons including IFN-α and IFN-β work through the ubiquitously expressed type I interferon receptor (IFNAR), while type III interferon IFN-λ and epithelial restricted type III interferon receptor Combine and function. In vitro and clinical studies have shown that SARS-CoV-2 is sensitive to type I IFN, and type I IFN treatment may be a promising treatment strategy for COVID-19.

Cholesterol 25-hydroxylase (CH25H) is a gene that encodes the enzyme that synthesizes hydroxysterol 25-hydroxycholesterol (25HC) from cholesterol. CH25H is an interferon-inducible gene that is strongly upregulated in SARS-CoV-2 infected lung epithelial cell lines and COVID-19 infected patients. Clinical studies have found that 25HC, the product of interferon-induced enzyme CH25H, has broad-spectrum antiviral activity against human coronaviruses. Previous studies have shown that 25HC can inhibit a variety of viruses from entering cells, including VSV, HIV, NiV, EBOV and ZIKV. However, the mechanism by which 25HC regulates virus entry is unclear. Existing studies have shown that the endoplasmic reticulum localization enzyme ACAT uses fatty acyl-coenzyme a and cholesterol as substrates to produce cholesterol esters, which are stored in cytoplasmic lipid droplets and induce the consumption of accessible cholesterol of plasma membrane through an unknown mechanism. When exploring the mechanism of 25HC function, the researchers found that 25HC triggers the consumption of accessible cholesterol in the plasma membrane by activating acyl coa:cholesterol acyltransferase (ACAT), thereby inhibiting the entry of viruses. Cholesterol has multiple effects on the lipid bilayer. The increase or decrease of cholesterol may be accompanied by changes in membrane fluidity, polarity, thickness, and inherent curvature. In addition, the change of cholesterol can affect the function of the entire membrane protein (including viral receptors or co-receptors) by changing its conformation or distribution on the plasma membrane. These changes will directly or indirectly affect the fusion of the virus and the cell membrane, and cell membrane fusion is critical to the release of the viral genome. Due to the importance of membrane cholesterol in virus-cell fusion, the mechanism of 25HC may extend to the cell membrane fusion process of other viruses.

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In this study, the researchers focused on cancer metastasis. The metastasis of cancer is the process by which cancer cells break away from the original tumor site and form new tumors at other sites in the body. Through observation and analysis of metastatic cancer cells, the researchers discovered some interesting phenomena, namely, the metabolites of methylmalonic acid (MMA), a byproduct of malonate metabolism, seem to accumulate as the body ages. And as a mediator of tumor progression. In order to analyze whether MMA plays a key role in the process of cancer metastasis, the researchers conducted related studies on people under 30 and over 60. When lung cancer cells and breast cancer cells are exposed to the blood of these people,  the behavior of lung and breast cancer cells whether change. The results of the study showed that in 30 blood samples from young donors, cancer cells in 25 samples did not show any changes, but in 30 blood samples from elderly donors, cancer cells in 25 samples exhibits different characteristics, its migration and invasion capabilities are enhanced, and it also has a certain tolerance to two drugs that are often used to treat cancer.

More interestingly, when the treated cancer cells are injected into mice, they will produce metastatic tumors in the lung tissues of the mice. So does MMA induce these changes in cancer cells? Through experimental research, it is found that the key to the changes in cancer cells induced by MMA seems to be the existence of a special reprogramming mechanism, which turns on the expression of the SOX4 gene. Previous studies have shown that SOX4 can make cancer cells more aggressive and easier to metastasize.

To determine the correlation between MMA and SOX4, the researchers blocked the expression of this gene. It was found that after blocking the Sox4 gene, the induction effect of MMA could not be produced. In addition, blocking the function of SOX4 also inhibits the ability of cancer cells to develop resistance to the two cancer therapies. This provides new ideas for new therapies to reduce mortality in cancer populations by descreasing MMA levels.

At present, researchers still have a series of questions to be solved, including why MMA will continue to accumulate in the body as the body ages, and whether the mechanisms found in blood samples and mouse studies are the same in humans. In addition, the blood samples used in the existing research are all from men, and it is necessary to verify whether the same mechanism will also appear in the female body in the later period.

Existing studies have shown that the accumulation of MMA is related to the intake of a high-protein diet, so a low-protein diet may be helpful in the treatment of cancer patients. Theoretically, drugs that lower MMA levels may also work, that is, potentially reducing the malignant spread of cancer in the patient’s body.

The post The New Mechanism of Aging To Promote Cancer first appeared on Creative Diagnostics.

Studies have shown that SMS is an enzyme that produces spermine from spermidine. It is very important for cell growth. Because the excessive accumulation of spermidine can have a harmful effect on cell viability, the body has a precise mechanism to regulate the level of spermidine in the cell. However, the mechanism of  tumor cells maintain a relatively high level of spermidine and below the toxicity threshold to promote tumor growth remains unclear.

Recently, researchers at the University of Kentucky found that SMS is overexpressed in colorectal cancer (CRC) and plays an important role in balancing the level of spermidine in cells. In this study, the researchers discovered that SMS and MYC together inhibit the important function of the apoptotic protein Bim by a unique regulatory pathway, and found that the down-regulation of Bim is a key survival signal for promoting CRC tumor growth.

Studies have shown that SMS overexpression plays an important role in balancing cell spermidine levels, and low spermidine levels are a necessary condition for the occurrence of CRC. In normal body cells, polyamine homeostasis is necessary for cell growth and tissue regeneration. With age, in model organisms and in humans, due to the decline in polyamine biosynthesis, the concentration of spermidine in tissues also decreases. In contrast, oncogenic signals induce the up-regulation of the biosynthetic activity of polyamine generating enzymes (such as ODC, SRM, SAMDC, and SMS), which in turn leads to an increase in the level of polyamines, which are thought to play an important role in tumor development. However, excessive polyamine accumulation itself can have a serious and harmful effect on cell activity. Similar to these findings, SMS is overexpressed in CRC during the entire tumorigenesis process, which can destroy the excessive accumulation of spermidine, and then make the spermidine in CRC cells at a tolerable level. Under normal physiological conditions, normal cells with properly regulated polyamine homeostasis can tolerate a certain level of spermidine, which is beneficial to their proliferation. In CRC cells, since the up-regulation of polyamine biosynthesis enzymes is much higher than in normal cells, spermidine is converted into spermine to prevent the level of spermidine from exceeding the toxicity threshold. Therefore, SMS gene knockout completely inhibits the function of SMS and induces excessive accumulation of spermidine, which leads to the inhibition of the growth of CRC.

Further studies have found that the targeted destruction of SMS in CRC cells leads to the accumulation of spermidine, which transfers to the nucleus and transcriptionally induces the expression of the pro-apoptotic protein Bim. However, myc-driven expression of miR-19a and miR-19b inhibited the production of Bim, thereby attenuating this induction. In CRC cells lacking SMS, drugs or genes inhibiting MYC activity can significantly induce Bim expression and apoptosis, leading to tumor regression, but these effects will be significantly reduced after Bim is silenced. These findings reveal the key survival signals in CRC that inhibit the expression of Bim through the aggregation of different signals and myc-mediated signaling pathways.

Therefore, inhibiting SMS and MYC signaling is a promising treatment strategy for CRC. The Cancer Genome Atlas data shows that MYC-dependent transcription is activated in almost all CRCs. Therefore, MYC is an attractive therapeutic target for CRC. Although there is no clear ligand-binding domain small molecule drug for MYC, emerging evidence suggests that small molecule compounds (such as JQ1) that target the epigenetic readers of the bromodomain and terminal extradomain (BET) family act as inhibitors of MYC activity. However, the efficacy of BET inhibitors in CRC is generally moderate, indicating that CRC tumors are inherently resistant to BET inhibition. However, the combined use of SMS inhibitors and BET inhibitors may have broad prospects in the treatment of CRC that is abnormally affected by SMS and MYC-mediated signaling pathways.

The post SMS and MYC Synergistically Promote The Survival of Colorectal Cancer Cells first appeared on Creative Diagnostics.

Most existing treatments for individual proteins rely on interactions with specific activity regulation of the target protein, such as enzyme inhibition or ligand blockade. However, there are some treatment-related proteins whose activities are unknown or unavailable, so the strategies above cannot be used to treat some proteins. In addition, strategies involving protein degradation platforms such as proteolytic targeting chimeras and other platforms (such as dTAGs, Trim-Away, chaperone-mediated autophagy targeting, and SNIPERs) have been developed for proteins that are generally difficult to target. However, these methods require the use of intracellular protein degradation mechanisms, so they are limited to proteins containing intracellular domains, and ligands can bind to these domains and recruit necessary cellular components.

Studies have found that extracellular proteins and membrane-associated proteins account for 40% of all protein-coding genes and are key factors in cancer, aging-related diseases and autoimmune diseases. Therefore, the general strategy of selective degradation of these proteins may improve human health . In this study, the researchers used a conjugate that binds to the lysosomal shuttle receptor on the cell surface and the extracellular domain of the target protein to determine a targeted degradation strategy for extracellular and membrane-associated proteins. These researchers have developed a new class of molecules that can shuttle unwanted proteins from the cell surface or the surrounding environment to the lysosome, which is the cell compartment dedicated to protein degradation. These molecules are called lysosomal targeted chimeras (LYTACs).

Mechanism of action of lysosome targeted chimera (LYTAC)
Existing studies have shown that cation-independent mannose-6-phosphate receptor (CI-M6PR) is involved in the biochemical pathway that mediates the internalization of cell line cargo. LYTAC uses this mechanism to transport labeled targeting molecules to the lysosome for degradation. The LYTAC molecule consists of an oligosaccharide peptide group (which binds to the cell surface receptor CI-M6PR) and an antibody that binds to a specific transmembrane protein or extracellular protein. The antibody can also be replaced by a small protein binding molecule. When combined with CI-M6PR and target protein at the same time, the resulting complex is swallowed by the cell membrane to form a transport vesicle. This brings this complex to the lysosome, after which the target protein is degraded and the receptor CI-M6PR is recycled. By degrading treatment-related proteins, including apolipoprotein E4, epidermal growth factor receptor, CD71, and programmed death ligand, it proves that the platform has a wide range of effects.

The key to this tool’s function lies in its dual-function design. One side of the LYTAC molecule can be customized to bind to any protein of interest. On the other side of it is a short amino acid sequence, or peptide, inlaid with a sugar called mannose-6-phosphate. This sugar acts as a label for the cell. When a cell contains proteins that are sent to the lysosome for degradation, it adds this sugar to ensure they reach their destination. There are receptors on the cell surface that interact with this sugar. When they grab the LYTAC molecule and pull it into the cell, the labeled protein will also be dragged in with it. In the process of attaching this tag to the protein, LYTAC hijacks a natural cell shuttle mechanism designed to escort newly synthesized lysosomal proteins to their new home. However, lysosomal proteins are tough enough to survive in the presence of degrading enzymes encountered in lysosomes, and most proteins cannot do this, so those that are labeled proteins by the LYTAC method are usually destroyed. This selective degradation can help scientists study and treat diseases such as cancer and Alzheimer’s disease related to surface proteins by targeting and degrading proteins that play an important role. More interestingly, the tethered end of LYTAC can be anything that binds to proteins, such as antibodies or existing drugs, so in the future, many other proteins and diseases can be target attacked.

The post Novel Chimera Targeting Lysosomes Can Degrade Extracellular Proteins first appeared on Creative Diagnostics.

Studies have found that the regulatory center of these epigenetic changes is located in the mitochondria. Mitochondria not only produce a large amount of 5′-adenosine triphosphate (ATP) through tricarboxylic acid (TCA) cycle and oxidative phosphorylation (OXPHOS) to maintain cell homeostasis, they also participate in the biosynthesis of some biological molecules, such as lipids and heme , Iron-sulfur clusters and intermediate metabolites, these intermediate metabolites can be used as signals to participate in the regulation of the rest of the cell, so that mitochondria become the center of a variety of biological processes. Through the continuous signal communication between the energy control center mitochondria and the nucleus, cells and organisms can monitor and integrate the body’s nutrient utilization and energy demand information, thereby ensuring the body’s metabolic stability.

Although the complete loss or nearly complete loss of mitochondrial function is unfavorable for cells, studies have found that partial inhibition of mitochondrial activity can promote the longevity of worms, flies, and mice. Studies on Caenorhabditis elegans indicate that in the early stages of life, the reduction of electron transport chain (ETC) activity in the mitochondria leads to extensive chromatin reorganization, which is essential for activating the mitochondrial unfolded protein response (UPRmt). This pathway can promote the restoration of mitochondrial protein homeostasis and stress. Specifically, the overall chromatin compaction induced by mitochondrial stress is manifested by the use of histone H3K9 methyltransferase SETDB1/MET-2 and its cofactors ATF7IP/LIN-65 to methylate non-essential genes to avoid the transcription of non-essential genes under stress conditions. The activation of stress-related UPRmt genes is demethylated and activated by histone H3K27 demethylases JMJD-1.2 and JMJD-3.1, thereby causing a sustained response and prolonging lifespan.

UPR mt is a transcriptional response that can induce the expression of mitochondrial chaperones and proteases, and then repair or degrade the misfolded proteins in mitochondria, and ultimately restore protein homeostasis in mitochondria. In addition, studies also found that UPR mt can also promote the reconnection of cell metabolism to reduce mitochondrial stress and promote cell survival. In Caenorhabditis elegans, when mitochondrial protein homeostasis is disrupted, UPR mt is induced, resulting in a decrease in the efficiency of mitochondrial entry, so that the transcription factor (TF) ATFS-1 that would otherwise enter the mitochondria for degradation enters the nucleus. Another TF and chromatin remodeling factor DVE-1 is also involved in UPR mt signal transduction, but unlike ATFS-1, its nuclear translocation does not depend on the efficiency of mitochondrial entry.

With the deepening of research, people have increasingly realized that many metabolic intermediates such as folic acid, acetyl-CoA (acetyl-CoA) and α-ketoglutarate (α-KG) not only affect the energy and material metabolism of cells , It also has a profound and dynamic impact on the overall chromatin modification. These intermediate metabolites can serve as substrates for enzymes that modify signal proteins, metabolic enzymes, and chromatin proteins. As the main source of epigenetic regulation of metabolites, such as, acetyl-CoA which is the source of histone and protein acetylation, and s-adenosylmethionine is the epigenetic methyl donor. In addition, α-KG produced in the TCA cycle of mitochondria is an essential cofactor for histone demethylase and DNA methylase. In contrast, succinic acid and fumaric acid inhibit these α-KG-dependent enzymes. In short, mitochondrial disturbances can change the nuclear epigenome by affecting various mitochondrial-derived metabolites, and ultimately affect cell proliferation and aging.

Recently, scientists have studied TF DVE-1, which is essential for UPR mt and contains homology domains, and identified nucleosome remodeling and histone deacetylases ( NuRD) complex that mediate the subcellular localization of DVE-1 in response to mitochondrial stress. The results show that after the mitochondrial function is disturbed, the level of mitochondrial-derived acetyl-CoA decreases, and the level of histone acetylation decreases, so that the NuRD complex can achieve overall chromatin reorganization. Restoring acetyl-CoA levels by providing the substrates and nutrients needed to produce acetyl-CoA can prevent the reduction of histone acetylation and inhibit chromatin reorganization under mitochondrial stress. In general, acetyl-CoA is a signal of mitochondrial dysfunction, which regulates body aging through NuRD-mediated chromatin remodeling.

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To test the function of endogenous CD95 in tumor cells, CD95-specific short hairpin (sh) RNA lentivirus was used to reduce the expression of CD95 in various human cancer cell lines. Infection with CD95-mediated lentiviral shRNA to the CD95-mediated apoptosis in vitro CD95 overexpressing ovarian cancer cell line HeyA8 greatly reduced the CD95 protein and surface expression, resulting in decreased CD95 apoptosis sensitivity. Interestingly, the abolition of CD95 expression also resulted in a substantial reduction in cancer cell growth. This has been confirmed by another shRNA targeting CD95 (R4) and another ovarian cancer cell line SKOV3.ip1, which expresses a very small amount of CD95 and is completely resistant to CD95L-induced apoptosis. Rebuilding SKOV3.ip1 CD95 knockdown cells and short-term anti-interference (si) RNA CD95 cells to endogenous levels can restore the growth of SKOV3.ip1 cells. In addition, growth inhibition of CD95 expression was also found in cell lines derived from colon cancer (HCT116), renal cancer (CAKI-1), breast cancer (MCF7), and liver cancer (HepG2). It is worth noting that 6 days after lentivirus infection, knockdown of CD95 in MCF7 cells with R6 virus resulted in growth arrest. However, 26 days after infection, the growth of cells expressing moderate CD95 levels was partially restored. However, neither MCF7 nor CAKI-1 cells benefited from the overexpression of CD95, indicating that regardless of absolute levels, cancer cells maintain CD95 expression at a level sufficient to promote optimal growth based on CD95 expression.

Further research shows that stimulation of CD95 in 22 tumor cell lines does not lead to increased proliferation. However, incubating cells with neutralized CD95L monoclonal antibody (mAb) NOK-1 reduced cell growth, indicating that the small amount of CD95L produced by tumor cells can help their growth. To further test this hypothesis, the researchers used three independent shRNAs specific to CD95L based on lentivirus to knock down CD95L. As a result, it was found that when the knockout efficiency was comparable, these viruses caused different degrees of growth inhibition, from reduced growth to complete loss of growth. In addition, knocking out CD95L will also reduce the growth of all other cancer cell lines, suggesting that CD95L is essential for the growth of many tumor cells.

In short, the CD95/CD95L system can promote the growth of cancer. CD95 activates neuronal stem cells and acts as a tumor promoter for glioblastoma by activating Src kinase. In addition, it was recently discovered that mice expressing only soluble CD95L can induce large histiocytic sarcoma in the liver, which may be due to the lack of apoptosis induction and the carcinogenic activity of CD95L. The data also shows that CD95 plays a role in promoting growth mainly through the pathways involving JNK, Jun, Erg1 and Fos.

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Existing studies have found that elevated bile acid (BA) can cause liver cell inflammation, apoptosis and liver cell necrosis, so long-term elevated BA levels in patients are considered to be risk factors for the development of liver cancer. In fact, changes in serum BA may be more useful in the diagnosis of cholangiocarcinoma. Therefore, as a key factor that mediates bile acid homeostasis, JNK has been focused on research. Previous studies have determined that liver c-Jun NH2 terminal kinase (JNK) deficiency can inhibit cholangiocarcinoma cell proliferation and oncogenic transformation in a p53/Kras-induced cholangiosarcoma model; and it is deficient in hepatocellular carcinoma with diethylnitrosamine and NEMO promotes cholangiocarcinoma in the syndrome model. Interestingly, recent studies have found that liver JNK alone is not enough to develop cholangiocarcinoma.

Through the search, scientists discovered an important regulator involved in lipid and BA liver metabolic homeostasis, the receptor α (PPARα) activated by peroxisome proliferators. The study found that JNK can inhibit the activation of PPARα in liver cells, thereby affecting lipid metabolism and steatosis through the liver factor FGF21 (encoded by the PPARα target gene). Further research found that JNK-mediated inhibition of PPARα leads to changes in BA homeostasis, thereby inhibiting cholangiocyte proliferation. Therefore, JNK deficiency will stimulate the proliferation of cholangiocarcinoma cells and promote the development of cholangiocarcinoma. Increased proliferation is caused by changes in BA metabolism and increased liver expression of FXR / FGF15 / FGFR4, which triggers ERK activation in cholangiocellular cells, which in turn activates downstream proliferation-related genes. The activation of FXR by BA triggers human fibroblast growth Factor 15/19 (FGF15 / FGF19) secretion. Clinical studies have found that FGF15/19 is expressed in the liver during the development of hepatocellular carcinoma and intrahepatic cholangiocarcinoma. It is worth noting that FGF15/19 improves blood glucose response and reduces hepatic steatosis, while also promoting liver cancer. Therefore, the steady state change of BA causes FGF15/FGF19 to promote the development of cholangiocarcinoma.Through the search, scientists discovered an important regulator involved in lipid and BA liver metabolic homeostasis, the receptor α (PPARα) activated by peroxisome proliferators. The study found that JNK can inhibit the activation of PPARα in liver cells, thereby affecting lipid metabolism and steatosis through the liver factor FGF21 (encoded by the PPARα target gene). Further research found that JNK-mediated inhibition of PPARα leads to changes in BA homeostasis, thereby inhibiting cholangiocyte proliferation. Therefore, JNK deficiency will stimulate the proliferation of cholangiocarcinoma cells and promote the development of cholangiocarcinoma. Increased proliferation is caused by changes in BA metabolism and increased liver expression of FXR / FGF15 / FGFR4, which triggers ERK activation in cholangiocellular cells, which in turn activates downstream proliferation-related genes. The activation of FXR by BA triggers human fibroblast growth Factor 15/19 (FGF15 / FGF19) secretion. Clinical studies have found that FGF15/19 is expressed in the liver during the development of hepatocellular carcinoma and intrahepatic cholangiocarcinoma. It is worth noting that FGF15/19 improves blood glucose response and reduces hepatic steatosis, while also promoting liver cancer. Therefore, the steady state change of BA causes FGF15/FGF19 to promote the development of cholangiocarcinoma.

In this process, liver PPARα is an important mediator of this regulatory cascade. PPARα deficiency significantly inhibits the phenotype caused by JNK deficiency. However, the role of PPARα in liver cancer remains unclear. Although some studies indicate that PPARα activation may promote liver cancer, other studies indicate that PPARα activation may be neutral or inhibit the development of liver cancer. This may be due to the different experimental conditions used in these studies. Recent studies have shown that the oncogenic effect of PPARα activation is partly due to changes in BA metabolism that drives ERK activation, which indicates that PPARα activation is a key factor in the development and progression of cholangiocarcinoma. The role of JNK /PPARα/ FGF signaling in lipid metabolism suggests that this pathway may represent a therapeutic target for steatosis and obesity. However, the potential risk of this pathway for carcinogenic progression indicates a serious problem with long-term treatment. Therefore, in the clinical treatment of steatosis and obesity using JNK inhibitory treatment strategies should consider the potential risk of cholangiocarcinoma.

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