SPHK1 (sphingosine kinase 1) induces epithelial-mesenchymal transition by promoting the autophagy-linked lysosomal degradation of CDH1/E-cadherin in hepatoma cells

Harnessing lysosomal genetics: development of a risk stratification panel and unveiling of DPP7 as a biomarker for colon adenocarcinoma

Lysosomal dysfunction has been implicated in the progression of colon adenocarcinoma (COAD), yet the prognostic significance and therapeutic potential of lysosome-related genes (LRGs) remain underexplored. In this study, we construct a 6-LRG-based prognostic risk stratification model (DPP7, ADAM8, CD1B, LRP2, ATP6V1C2, and PLAAT3) by integrating LASSO and Cox regression analyses. Stratifying patients based on median risk scores, we demonstrate that high-risk patients exhibit significantly worse clinical outcomes across the TCGA cohort and five independent GEO datasets. Furthermore, this panel outperforms 136 previously published models in terms of predictive accuracy for 1-, 3-, and 5-year survival rates. Validation multiplex immunofluorescence using an in-house tissue microarray cohort confirms the 6-LRG signature serves as an independent prognostic factor. Additionally, high-risk patients exhibit distinct immunosuppressive tumor microenvironment and aggressive malignancy characteristics. Functional depletion of DPP7 significantly inhibits tumor cell proliferation, migration, and metastasis in both in vitro and in vivo settings. Moreover, DPP7 silencing attenuates epithelial-mesenchymal transition, as evidenced by the upregulation of E-cadherin and downregulation of N-cadherin, Vimentin, and Snail. In conclusion, this study establishes an LRG-based model for COAD prognostic prediction and nominates DPP7 as a promising therapeutic target for COAD treatment.

Epithelial-to-mesenchymal transition and live cell extrusion contribute to measles virus release from human airway epithelia

Measles virus (MeV) is a highly contagious respiratory virus transmitted via aerosols. To understand how MeV exits the airways of an infected host, we use unpassaged primary cultures of human airway epithelial cells (HAE). MeV typically remains cell-associated in HAE and forms foci of infection, termed infectious centers, by directly spreading cell-to-cell. We previously described the phenomenon in which infectious centers detach en masse from HAE and remain viable. Here, we investigate the mechanism of this cellular detachment. Via immunostaining, we observed loss of tight junction and cell adhesion proteins within infectious centers. These morphological changes indicate activation of epithelial-to-mesenchymal transition (EMT). EMT can contribute to wound healing in respiratory epithelia by mobilizing nearby cells. Inhibiting TGF-β, and thus EMT, reduced infectious center detachment. Compared with uninfected cells, MeV-infected cells also expressed increased levels of sphingosine kinase 1 (SK1), a regulator of live cell extrusion. Live cell extrusion encourages cells to detach from respiratory epithelia by contracting the actomyosin of neighboring cells. Inhibition or induction of live cell extrusion impacted infectious center detachment rates. Thus, these two related pathways contributed to infectious center detachment in HAE. Detached infectious centers contained high titers of virus that may be protected from the environment, allowing the virus to live on surfaces longer and infect more hosts.IMPORTANCEMeasles virus (MeV) is an extremely contagious respiratory pathogen that continues to cause large, disruptive outbreaks each year. Here, we examine mechanisms of detachment of MeV-infected cells. MeV spreads cell-to-cell in human airway epithelial cells (HAE) to form groups of infected cells, termed "infectious centers". We reported that infectious centers ultimately detach from HAE as a unit, carrying high titers of virus. Viral particles within cells may be more protected from environmental conditions, such as ultraviolet radiation and desiccation. We identified two host pathways, epithelial-to-mesenchymal transition and live cell extrusion, that contribute to infectious center detachment. Perturbing these pathways altered the kinetics of infectious center detachment. These pathways influence one another and contribute to epithelial wound healing, suggesting that infectious center detachment may be a usurped consequence of the host's response to infection that benefits MeV by increasing its transmissibility between hosts.

Potential Modulatory Role of Phoenixin-14 in Epithelial-Mesenchymal Transition of Endometriotic 12Z Cells

Background/Objectives: Endometriosis is a painful chronic condition in which the endometrium grows outside the uterus. The epithelial-mesenchymal transition (EMT) is critical to endometriosis progression, where cells lose epithelial traits and gain invasiveness. Methods: This study investigates the effects of phoenixin-14 (PNX-14), a neuropeptide found at reduced levels in endometriosis patients, on the expression of two molecular EMT markers, CDH1 (E-cadherin) and THBS2 (thrombospondin 2), as well as cell viability in the endometriosis-derived 12Z cell line. Cells were treated with physiological (0.2 nM) and endometriosis-relevant (0.05 nM) concentrations of PNX-14. Gene expression was analyzed using RT-qPCR, while protein localization was assessed by immunocytochemistry. Cell viability was measured using an XTT assay. Results: THBS2 gene expression was significantly decreased, and CDH1 remained unchanged in cells stimulated by 0.05 nM PNX-14. Immunolocalization indicates a weaker THBS2 and CDH1 protein immunosignal reaction for 0.05 nM PNX-14. PNX-14 treatment also exhibited a biphasic effect on cell viability. Lower concentration initially decreased viability at 48 h but then significantly increased it at 72 h. This increase coincided with the decrease in THBS2 expression, suggesting a potential link between PNX-14, THBS2, and cell viability. Conclusions: A negative correlation between cell viability and the expression of both EMT markers further highlights their possible involvement in the survival and adaptability of ectopic epithelial cells. Our findings suggest a complex interplay between PNX-14, EMT markers, and cell viability in ectopic epithelial cells. PNX-14's ability to modulate these factors warrants further investigation to elucidate its role in endometriosis.

Sphingosine-1-phosphate alleviates Sjögren's syndrome-like symptoms via inducing autophagy and regulating status of Treg cells in NOD mice

BACKGROUND

Sjögren' s syndrome (SS) is a chronic autoimmune disease that causes multiple lesions. Regulatory T (Treg) cells play an important role in the maintenance of immune homeostasis. Weakened Treg-cell-mediated immunosuppression may aggravate SS symptoms by inducing lymphocyte infiltration into the salivary glands. Although Treg cell egress from such glands requires sphingosine-1-phosphate (S1P), the specific effects of S1P on SS-like symptoms remain unclear.

AIMS

To examine the effect of S1P on SS-like symptoms and the crosstalk between such symptoms and autophagy in non-obese diabetic (NOD) mice.

METHODS

NOD mice were taken as SS model mice. Balb/c mice served as controls. Serum anti-SSA and anti-SSB antibodies were quantitated via ELISA. Submandibular gland tissues were subjected to haematoxylin-and-eosin staining, and extracts thereof to reverse transcription-polymerase chain reaction. The numbers of Treg cells; and the levels of cytokines, LC3, and SPHK1 were measured via flow cytometry (FCM). The Treg immunosuppression capacity was assessed in co-culture experiments.

RESULT

Compared to untreated NOD mice, mice treated with S1P exhibited milder disease, and higher numbers of functional Treg cells. FCM revealed that S1P restored LC3 expression in Treg cells, but had little effect on the LC3 levels of Teff cells. RT-PCR showed that S1P increased the expression levels of mRNAs encoding Foxp-3, SPHK1, S1PR1, and LC3 in submandibular glands (SMGs). After administration of PF-543, the disease became aggravated; lymphocyte infiltration into SMGs increased and LC3 expression fell.

CONCLUSION

S1P therapy alleviated SS-like symptoms in NOD mice by increasing the number of Treg cells, by restoring Treg cell function, and by positively regulating autophagy via crosstalk. Such therapy may be a new and valuable SS treatment option.

Analysis of nitrogen metabolism-related gene expression in hepatocellular carcinoma to establish relevant indicators for prediction of prognosis and guidance of immunotherapy

BACKGROUND

The prognosis of cancers is strongly connected with nitrogen metabolism (NM), which plays a critical role in the microenvironment and growth of tumors. It is unsubstantiated, however, how important NM-related genes are for the prognosis of hepatocellular carcinoma (HCC).

METHODS

Using publicly available data, we examined potential mechanisms of NM-related genes in HCC, created a predictive model, and assessed immune infiltration and medication sensitivity.

RESULTS

A prognostic model, which included 12 NM genes (COLQ, GNE, ISCU, MSRA, SARS2, SPHK1, CBS, GOT2, CHST1, EXTL2, GCLM, YARS1), was constructed based on regression analysis. The robustness of the model was validated using multiple methods. The high-risk (HR) and low-risk (LR) groups had varying degrees of immune infiltration, according to an immunology-related study. Of these, B cells and Type_II_IFN_Response were greatly infiltrated in the LR group, whereas aCDs, Macrophages, and Treg were heavily infiltrated in the HR group (p < 0.05). Because of higher immunophenoscore, the low-risk group could benefit from immunotherapy more. Drug sensitivity predictions indicated that people with high CBS expression and low GOT2 and ISCU expression may benefit more from treatment with SCH-772984, Pimasertib, Cobimetinib (isomer1), TAK-733, LY-3214996, ARRY-162, Cladribine, Fludarabine, and Hydroxyurea.

CONCLUSION

This work created a 12-gene signature based on NM, preliminary investigated immune infiltration in two risk categories, and discovered some possible anti-tumor medications. To sum up, our study findings offer fresh perspectives on the roles played by NM-associated genes in HCC development, prognosis, immunological response, and medication screening.

SPHK1 promotes bladder cancer metastasis via PD-L2/c-Src/FAK signaling cascade

SPHK1 (sphingosine kinase type 1) is characterized as a rate-limiting enzyme in sphingolipid metabolism to phosphorylate sphingosine into sphingosine-1-phosphate (S1P) that can bind to S1P receptors (S1PRs) to initiate several signal transductions leading to cell proliferation and survival of normal cell. Many studies have indicated that SPHK1 is involved in several types of cancer development, however, a little is known in bladder cancer. The TCGA database analysis was utilized for analyzing the clinical relevance of SPHK1 in bladder cancer. Through CRISPR/Cas9 knockout (KO) and constitutive activation (CA) strategies on SPHK1 in the bladder cancer cells, we demonstrated the potential downstream target could be programmed cell death 1 ligand 2 (PD-L2). On the other hand, we demonstrated that FDA-approved SPHK1 inhibitor Gilenya® (FTY720) can successfully suppress bladder cancer metastasis by in vitro and in vivo approaches. This finding indicated that SPHK1 as a potent therapeutic target for metastatic bladder cancer by dissecting the mechanism of action, SPHK1/S1P-elicited Akt/β-catenin activation promoted the induction of PD-L2 that is a downstream effector in facilitating bladder cancer invasion and migration. Notably, PD-L2 interacted with c-Src that further activates FAK. Here, we unveil the clinical relevance of SPHK1 in bladder cancer progression and the driver role in bladder cancer metastasis. Moreover, we demonstrated the inhibitory effect of FDA-approved SPHK1 inhibitor FTY720 on bladder cancer metastasis from both in vitro and in vivo models.

Bioactive sphingolipids as emerging targets for signal transduction in cancer development

Sphingolipids, crucial components of cellular membranes, play a vital role in maintaining cellular structure and signaling integrity. Disruptions in sphingolipid metabolism are increasingly implicated in cancer development. Key bioactive sphingolipids, such as ceramides, sphingosine-1-phosphate (S1P), ceramide-1-phosphate (C1P), and glycosphingolipids, profoundly impact tumor biology. They influence the behavior of tumor cells, stromal cells, and immune cells, affecting tumor aggressiveness, angiogenesis, immune modulation, and extracellular matrix remodeling. Furthermore, abnormal expression of sphingolipids and their metabolizing enzymes modulates the secretion of tumor-derived extracellular vesicles (TDEs), which are key players in creating an immunosuppressive tumor microenvironment, remodeling the extracellular matrix, and facilitating oncogenic signaling within in situ tumors and distant pre-metastatic niches (PMNs). Understanding the role of sphingolipids in the biogenesis of tumor-derived extracellular vesicles (TDEs) and their bioactive contents can pave the way for new biomarkers in cancer diagnosis and prognosis, ultimately enhancing comprehensive tumor treatment strategies.

Wnt5a-mediated autophagy contributes to the epithelial-mesenchymal transition of human bronchial epithelial cells during asthma

BACKGROUND

The epithelial-mesenchymal transition (EMT) of human bronchial epithelial cells (HBECs) is essential for airway remodeling during asthma. Wnt5a has been implicated in various lung diseases, while its role in the EMT of HBECs during asthma is yet to be determined. This study sought to define whether Wnt5a initiated EMT, leading to airway remodeling through the induction of autophagy in HBECs.

METHODS

Microarray analysis was used to investigate the expression change of WNT5A in asthma patients. In parallel, EMT models were induced using 16HBE cells by exposing them to house dust mites (HDM) or interleukin-4 (IL-4), and then the expression of Wnt5a was observed. Using in vitro gain- and loss-of-function approaches via Wnt5a mimic peptide FOXY5 and Wnt5a inhibitor BOX5, the alterations in the expression of the epithelial marker E-cadherin and the mesenchymal marker protein were observed. Mechanistically, the Ca2+/CaMKII signaling pathway and autophagy were evaluated. An autophagy inhibitor 3-MA was used to examine Wnt5a in the regulation of autophagy during EMT. Furthermore, we used a CaMKII inhibitor KN-93 to determine whether Wnt5a induced autophagy overactivation and EMT via the Ca2+/CaMKII signaling pathway.

RESULTS

Asthma patients exhibited a significant increase in the gene expression of WNT5A compared to the healthy control. Upon HDM and IL-4 treatments, we observed that Wnt5a gene and protein expression levels were significantly increased in 16HBE cells. Interestingly, Wnt5a mimic peptide FOXY5 significantly inhibited E-cadherin and upregulated α-SMA, Collagen I, and autophagy marker proteins (Beclin1 and LC3-II). Rhodamine-phalloidin staining showed that FOXY5 resulted in a rearrangement of the cytoskeleton and an increase in the quantity of stress fibers in 16HBE cells. Importantly, blocking Wnt5a with BOX5 significantly inhibited autophagy and EMT induced by IL-4 in 16HBE cells. Mechanistically, autophagy inhibitor 3-MA and CaMKII inhibitor KN-93 reduced the EMT of 16HBE cells caused by FOXY5, as well as the increase in stress fibers, cell adhesion, and autophagy.

CONCLUSION

This study illustrates a new link in the Wnt5a-Ca2+/CaMKII-autophagy axis to triggering airway remodeling. Our findings may provide novel strategies for the treatment of EMT-related diseases.

Global research status and frontiers on autophagy in hepatocellular carcinoma: a comprehensive bibliometric and visualized analysis

BACKGROUND

An extensive body of research has explored the role of autophagy in hepatocellular carcinoma (HCC), revealing its critical involvement in the disease's pathogenesis, progression, and therapeutic targeting. However, there is a discernible deficit in quantitative, analytical studies concerning autophagy in the context of HCC. Accordingly, this investigation endeavored to meticulously assess the evolution of autophagy research, employing bibliometric citation analysis to offer a comprehensive evaluation of the findings in this field.

METHODS

The authors conducted a literature search on 2 August 2023, to extract relevant publications spanning from 2013 to 2022, indexed in the Science Citation Index-Expanded (SCIE) of the Web of Science Core Collection (WOSCC). Subsequently, the authors performed a bibliometric assessment of the compiled documents using visualization tools such as CiteSpace and VOSviewer.

RESULTS

The search yielded 734 publications penned by 4699 authors, encompassing contributions from 41 countries and 909 institutions, disseminated across 272 journals, and comprising 26 295 co-cited references from 2667 journals. Notably, China led in publication volume with 264 articles (amounting to 35.9%) and exhibited the most robust collaboration with the United States. The mechanisms underlying autophagy's influence on the emergence and advancement of HCC, as well as the implicated proteins and genes, have garnered significant attention. In recent years, investigations of targeting autophagy and the resistance to sorafenib have surfaced as pivotal themes and emerging frontiers in this domain.

CONCLUSIONS

This study rigorously collated and distilled the prevailing research narratives and novel insights on autophagy in HCC. The resultant synthesis provides a substantive foundation for medical professionals and researchers, as well as pivotal implications for future investigative endeavors in this arena.

Immune checkpoints between epithelial-mesenchymal transition and autophagy: A conflicting triangle

Inhibitory immune checkpoint (ICP) molecules are pivotal in inhibiting innate and acquired antitumor immune responses, a mechanism frequently exploited by cancer cells to evade host immunity. These evasion strategies contribute to the complexity of cancer progression and therapeutic resistance. For this reason, ICP molecules have become targets for antitumor drugs, particularly monoclonal antibodies, collectively referred to as immune checkpoint inhibitors (ICI), that counteract such cancer-associated immune suppression and restore antitumor immune responses. Over the last decade, however, it has become clear that tumor cell-associated ICPs can also induce tumor cell-intrinsic effects, in particular epithelial-mesenchymal transition (EMT) and macroautophagy (hereafter autophagy). Both of these processes have profound implications for cancer metastasis and drug responsiveness. This article reviews the positive or negative cross-talk that tumor cell-associated ICPs undergo with autophagy and EMT. We discuss that tumor cell-associated ICPs are upregulated in response to the same stimuli that induce EMT. Moreover, ICPs themselves, when overexpressed, become an EMT-inducing stimulus. As regards the cross-talk with autophagy, ICPs have been shown to either stimulate or inhibit autophagy, while autophagy itself can either up- or downregulate the expression of ICPs. This dynamic equilibrium also extends to the autophagy-apoptosis axis, further emphasizing the complexities of cellular responses. Eventually, we delve into the intricate balance between autophagy and apoptosis, elucidating its role in the broader interplay of cellular dynamics influenced by ICPs. In the final part of this article, we speculate about the driving forces underlying the contradictory outcomes of the reciprocal, inhibitory, or stimulatory effects between ICPs, EMT, and autophagy. A conclusive identification of these driving forces may allow to achieve improved antitumor effects when using combinations of ICIs and compounds acting on EMT and/or autophagy. Prospectively, this may translate into increased and/or broadened therapeutic efficacy compared to what is currently achieved with ICI-based clinical protocols.

Lysosomes in Cancer-At the Crossroad of Good and Evil

Although it has been known for decades that lysosomes are central for degradation and recycling in the cell, their pivotal role as nutrient sensing signaling hubs has recently become of central interest. Since lysosomes are highly dynamic and in constant change regarding content and intracellular position, fusion/fission events allow communication between organelles in the cell, as well as cell-to-cell communication via exocytosis of lysosomal content and release of extracellular vesicles. Lysosomes also mediate different forms of regulated cell death by permeabilization of the lysosomal membrane and release of their content to the cytosol. In cancer cells, lysosomal biogenesis and autophagy are increased to support the increased metabolism and allow growth even under nutrient- and oxygen-poor conditions. Tumor cells also induce exocytosis of lysosomal content to the extracellular space to promote invasion and metastasis. However, due to the enhanced lysosomal function, cancer cells are often more susceptible to lysosomal membrane permeabilization, providing an alternative strategy to induce cell death. This review summarizes the current knowledge of cancer-associated alterations in lysosomal structure and function and illustrates how lysosomal exocytosis and release of extracellular vesicles affect disease progression. We focus on functional differences depending on lysosomal localization and the regulation of intracellular transport, and lastly provide insight how new therapeutic strategies can exploit the power of the lysosome and improve cancer treatment.

SPHK1 potentiates colorectal cancer progression and metastasis via regulating autophagy mediated by TRAF6-induced ULK1 ubiquitination

A sphingolipid metabolite regulator, sphingosine kinase 1 (SPHK1), plays a critical role in the development of colorectal cancer (CRC). Studies have demonstrated that invasion and metastasis of CRC are promoted by SPHK1-driven autophagy. However, the exact mechanism of SPHK1 drives autophagy to promote tumor progression remains unclear. Here, immunohistochemical detection showed the expression of SPHK1 and tumor necrosis factor receptor-associated factor-6 (TRAF6) in human CRC tissues was stronger than in adjacent normal tissues, they were both associated with distance metastasis. It was discovered that knockdown of SPHK1 reduced the expression of TRAF6, inhibited autophagy, and inhibited the growth and metastasis of CRC cells in vitro. Moreover, the effects of SPHK1-downregulating were reversed by overexpression of TRAF6 in CRC cells transfected by double-gene. Overexpression of SPHK1 and TRAF6 promoted the expression of autophagy protein LC3 and Vimentin, while downregulated the expression of autophagy protein P62 and E-cadherin. The expression of autophagy-related ubiquitination protein ULK1 and Ubiquitin protein were significantly upregulated in TRAF6-overexpressed CRC cells. In addition, autophagy inhibitor 3-methyladenine (3MA) significantly inhibited the metastasis-promoting effect of SPHK1 and TRAF6, suppressed the expression of LC3 and Vimentin, and promoted the expression of P62 and E-cadherin, in CRC cells. Immunofluorescence staining showed SPHK1 and TRAF6 were co-localized in HT29 CRC cell membrane and cytoplasm. Immunoprecipitation detection showed SPHK1 was efficiently combined with the endogenous TRAF6, and the interaction was also detected reciprocally. Additionally, proteasome inhibitor MG132 treatment upregulated the expression of TRAF6 and the level of Ubiquitin protein, in SPHK1-downregulating CRC cells. These results reveal that SPHK1 potentiates CRC progression and metastasis via regulating autophagy mediated by TRAF6-induced ULK1 ubiquitination. SPHK1-TRAF6-ULK1 signaling axis is critical to the progression of CRC and provides a new strategy for the therapeutic control of CRC.

PAK inhibitor FRAX486 decreases the metastatic potential of triple-negative breast cancer cells by blocking autophagy

BACKGROUND

Triple-negative breast cancer (TNBC) is a unique breast cancer subtype with a high risk of metastasis and recurrence and a poor prognosis. Epithelial-mesenchymal transition (EMT) endows epithelial cells with the ability to move to distant sites, which is essential for the metastasis of TNBC to organs, including the lung. Autophagy, an intracellular degradation process that involves formation of double-layered lipid autophagosomes that transport cytosolic cargoes into lysosomes via autophagosome-lysosome fusion, is involved in various diseases, including cancer and neurodegenerative, metabolic, cardiovascular, and infectious diseases. The relationship between autophagy and cancer has become relatively clear. However, research on pharmacological drugs that block cancer EMT by targeting autophagy is still in the initial stages. Therefore, the re-evaluation of old drugs for their potential in blocking both autophagy and EMT was conducted.

METHODS

More than 2000 small molecule chemicals were screened for dual autophagy/EMT inhibitors, and FRAX486 was identified as the best candidate inhibitor of autophagy/EMT. The functions of FRAX486 in TNBC metastasis were detected by CCK-8, migration and wound healing assays. The effects of FRAX486 on autophagy and its target PAK2 were determined by immunoblotting, immunofluorescence, immunoprecipitation analysis and transmission electron microscopy. The findings were validated in mouse models.

RESULTS

Here, we report that FRAX486, a potent P21-activated kinase 2 (PAK2) inhibitor, facilitates TNBC suppression both in vitro and in vivo by blocking autophagy. Mechanistically, FRAX486 inhibits autophagy in TNBC cells by targeting PAK2, leading to the ubiquitination and proteasomal degradation of STX17, which mediates autophagosome-lysosome fusion. The inhibition of autophagy by FRAX486 causes upregulation of the epithelial marker protein E-cadherin and thus suppresses the migration and metastasis of TNBC cells.

CONCLUSIONS

The effects of FRAX486 on TNBC metastasis suppression were verified to be dependent on PAK2 and autophagy inhibition. Together, our results provide a molecular basis for the application of FRAX486 as a potential treatment for inhibiting the metastasis of TNBC.

Targeting Lysosomes: A Strategy Against Chemoresistance in Cancer

Chemotherapy is still the major method of treatment for many types of cancer. Curative cancer therapy is hampered significantly by medication resistance. Acidic organelles like lysosomes serve as protagonists in cellular digestion. Lysosomes, however, are gaining popularity due to their speeding involvement in cancer progression and resistance. For instance, weak chemotherapeutic drugs of basic nature permeate through the lysosomal membrane and are retained in lysosomes in their cationic state, while extracellular release of lysosomal enzymes induces cancer, cytosolic escape of lysosomal hydrolases causes apoptosis, and so on. Drug availability at the sites of action is decreased due to lysosomal drug sequestration, which also enhances cancer resistance. This review looks at lysosomal drug sequestration mechanisms and how they affect cancer treatment resistance. Using lysosomes as subcellular targets to combat drug resistance and reverse drug sequestration is another method for overcoming drug resistance that is covered in this article. The present review has identified lysosomal drug sequestration as one of the reasons behind chemoresistance. The article delves deeper into specific aspects of lysosomal sequestration, providing nuanced insights, critical evaluations, or novel interpretations of different approaches that target lysosomes to defect cancer.

Sphingolipid paracrine signaling impairs keratinocyte adhesion to promote melanoma invasion

Melanoma is the deadliest form of skin cancer due to its propensity to metastasize. It arises from melanocytes, which are attached to keratinocytes within the basal epidermis. Here, we hypothesize that, in addition to melanocyte-intrinsic modifications, dysregulation of keratinocyte functions could initiate early-stage melanoma cell invasion. We identified the lysolipid sphingosine 1-phosphate (S1P) as a tumor paracrine signal from melanoma cells that modifies the keratinocyte transcriptome and reduces their adhesive properties, leading to tumor invasion. Mechanistically, tumor cell-derived S1P reduced E-cadherin expression in keratinocytes via S1P receptor dependent Snail and Slug activation. All of these effects were blocked by S1P2/3 antagonists. Importantly, we showed that epidermal E-cadherin expression was inversely correlated with the expression of the S1P-producing enzyme in neighboring tumors and the Breslow thickness in patients with early-stage melanoma. These findings support the notion that E-cadherin loss in the epidermis initiates the metastatic cascade in melanoma.

Pancreatic Acinar Cells-Derived Sphingosine-1-Phosphate Contributes to Fibrosis of Chronic Pancreatitis via Inducing Autophagy and Activation of Pancreatic Stellate Cells

BACKGROUND & AIMS

Studies have demonstrated that activated pancreatic stellate cells (PSCs) play a crucial role in pancreatic fibrogenesis in chronic pancreatitis (CP); however, the precise mechanism for PSCs activation has not been fully elucidated. We analyzed the role of injured pancreatic acinar cells (iPACs) in the activation of PSCs of CP.

METHODS

Sphingosine kinase 1 (SPHK1)/sphingosine-1-phosphate (S1P) signaling was evaluated in experimental CP induced by cerulein injection or pancreatic duct ligation, as well as in PACs injured by cholecystokinin. The activation of PSCs and pancreatic fibrosis in CP samples was evaluated by immunohistochemical and immunofluorescence analyses. In vitro coculture assay of iPACs and PSCs was created to evaluate the effect of the SPHK1/S1P pathway and S1P receptor 2 (SIPR2) on autophagy and activation of PSCs. The pathogenesis of CP was assessed in SPHK1-/- mice or PACs-specific SPHK1-knockdown mice with recombinant adeno-associated virus serotypes 9-SPHK1-knockdown, as well as in mice treated with inhibitor of SPHK1 and S1P receptor 2 (S1PR2).

RESULTS

SPHK1/S1P was remarkably increased in iPACs and acinar cells in pancreatic tissues of CP mice. Meanwhile, the pathogenesis, fibrosis, and PSCs activation of CP was significantly prevented in SPHK1-/- mice and recombinant adeno-associated virus serotypes 9-SPHK1-knockdown mice. Meanwhile, iPACs obviously activated PSCs, which was prevented by SPHK1 knockdown in iPACs. Moreover, iPACs-derived S1P specifically combined to S1PR2 of PSCs, by which modulated 5' adenosine monophosphate-activated protein kinase/mechanistic target of rapamycin pathway and consequently induced autophagy and activation of PSCs. Furthermore, hypoxia-inducible factor 1-α and -2α promoted SPHK1 transcription of PACs under hypoxia conditions, which is a distinct characteristic of the CP microenvironment. Coincidently, inhibition of SPHK1 and S1PR2 activity with inhibitor PF-543 and JTE-013 obviously impeded pancreatic fibrogenesis of CP mice.

CONCLUSIONS

The activated SPHK1/S1P pathway in iPACs induces autophagy and activation of PSCs by regulating the S1PR2/5' adenosine monophosphate-activated protein kinase/mammalian target of rapamycin pathway, which promotes fibrogenesis of CP. The hypoxia microenvironment might contribute to the cross talk between PACs and PSCs in pathogenesis of CP.

Ag/TiO2 nanohybrids induce fibrosis-related epithelial-mesenchymal transition in lung epithelial cells and the influences of silver content and silver particle size

The controlled synthesis of silver nanoparticles (AgNPs) decorated TiO2 nanohybrids (Ag/TiO2) for photocatalysis has received considerable attention. These photocatalysts are widely used in environment and energy, resulting in human exposure through inhalation. Pure TiO2 is generally considered a low-toxic nanomaterial. However, little is known about the toxicity after AgNPs loading. In this study, silver-decorated TiO2 nanohybrids were controllably synthesized by the photodeposition method, and their toxic effects on murine lung and human lung epithelial cells were explored. As a result, silver loading significantly enhanced the effect of TiO2 photocatalyst on EMT in lung epithelial cells, potentially acting as a pro-fibrogenic effect in murine lung. Meanwhile, the increase in autophagy vacuoles, LC3-II marker, stub-RFP-sens-GFP-LC3 fluorescence assay, and LC3 turnover assay showed that silver loading also significantly increased autophagy flux. Furthermore, analysis of autophagy inhibition by 3-Methyladenine indicated that the promotion of EMT by silver loading was related to the increased autophagy flux. Intriguingly, the autophagy and EMT biological effects could be alleviated when the silver loading amount was reduced or silver particle size was increased, and the enhanced pro-fibrogenic effect was mitigated at the same time. This study supplemented safety information of Ag-decorated TiO2 nanohybrids and provided methods of controlled synthesis for reducing toxicity.

Unraveling the Janus-Faced Role of Autophagy in Hepatocellular Carcinoma: Implications for Therapeutic Interventions

This review aims to provide a comprehensive understanding of the molecular mechanisms underlying autophagy and mitophagy in hepatocellular carcinoma (HCC). Autophagy is an essential cellular process in maintaining cell homeostasis. Still, its dysregulation is associated with the development of liver diseases, including HCC, which is one of leading causes of cancer-related death worldwide. We focus on elucidating the dual role of autophagy in HCC, both in tumor initiation and progression, and highlighting the complex nature involved in the disease. In addition, we present a detailed analysis of a small subset of autophagy- and mitophagy-related molecules, revealing their specific functions during tumorigenesis and the progression of HCC cells. By understanding these mechanisms, we aim to provide valuable insights into potential therapeutic strategies to manipulate autophagy effectively. The goal is to improve the therapeutic response of liver cancer cells and overcome drug resistance, providing new avenues for improved treatment options for HCC patients. Overall, this review serves as a valuable resource for researchers and clinicians interested in the complex role of autophagy in HCC and its potential as a target for innovative therapies aimed to combat this devastating disease.

Machine learning-enhanced insights into sphingolipid-based prognostication: revealing the immunological landscape and predictive proficiency for immunomotherapy and chemotherapy responses in pancreatic carcinoma

Background: With a poor prognosis for affected individuals, pancreatic adenocarcinoma (PAAD) is known as a complicated and diverse illness. Immunocytes have become essential elements in the development of PAAD. Notably, sphingolipid metabolism has a dual function in the development of tumors and the invasion of the immune system. Despite these implications, research on the predictive ability of sphingolipid variables for PAAD prognosis is strikingly lacking, and it is yet unclear how they can affect PAAD immunotherapy and targeted pharmacotherapy. Methods: The investigation process included SPG detection while also being pertinent to the prognosis for PAAD. Both the analytical capability of CIBERSORT and the prognostic capability of the pRRophetic R package were used to evaluate the immunological environments of the various HCC subtypes. In addition, CCK-8 experiments on PAAD cell lines were carried out to confirm the accuracy of drug sensitivity estimates. The results of these trials, which also evaluated cell survival and migratory patterns, confirmed the usefulness of sphingolipid-associated genes (SPGs). Results: As a result of this thorough investigation, 32 SPGs were identified, each of which had a measurable influence on the dynamics of overall survival. This collection of genes served as the conceptual framework for the development of a prognostic model, which was carefully assembled from 10 chosen genes. It should be noted that this grouping of patients into cohorts with high and low risk was a sign of different immune profiles and therapy responses. The increased abundance of SPGs was identified as a possible sign of inadequate responses to immune-based treatment approaches. The careful CCK-8 testing carried out on PAAD cell lines was of the highest importance for providing clear confirmation of drug sensitivity estimates. Conclusion: The significance of Sphingolipid metabolism in the complex web of PAAD development is brought home by this study. The novel risk model, built on the complexity of sphingolipid-associated genes, advances our understanding of PAAD and offers doctors a powerful tool for developing personalised treatment plans that are specifically suited to the unique characteristics of each patient.

The role of sphingosine-1-phosphate in autophagy and related disorders

S1P, also referred to as sphingosine-1-phosphate, is a lipid molecule with bioactive properties involved in numerous cellular processes such as cell growth, movement, programmed cell death, self-degradation, cell specialization, aging, and immune system reactions. Autophagy is a meticulously controlled mechanism in which cells repurpose their elements to maintain cellular balance. There are five stages in autophagy: initiation, nucleation, elongation and maturation, fusion, and degradation. New research has provided insight into the complex connection between S1P and autophagy, uncovering their interaction in both normal and abnormal circumstances. Gaining knowledge about the regulatory mechanism of S1P signaling on autophagy can offer a valuable understanding of its function in well-being and illness, potentially leading to innovative therapeutic concepts for diverse ailments. Hence, this review analyzes the essential stages in mammalian autophagy, with a specific emphasis on recent research exploring the control of each stage by S1P. Additionally, it sheds light on the roles of S1P-induced autophagy in various disorders.

Integrative roles of sphingosine kinase in liver pathophysiology

Bioactive sphingolipids and enzymes that metabolize sphingolipid-related substances have been considered as critical messengers in various signaling pathways. One such enzyme is the crucial lipid kinase, sphingosine kinase (SphK), which mediates the conversion of sphingosine to the potent signaling substance, sphingosine-1-phosphate. Several studies have demonstrated that SphK metabolism is strictly regulated to maintain the homeostatic balance of cells. Here, we summarize the role of SphK in the course of liver disease and illustrate its effects on both physiological and pathological conditions of the liver. SphK has been implicated in a variety of liver diseases, such as steatosis, liver fibrosis, hepatocellular carcinoma, and hepatic failure. This study may advance the understanding of the cellular and molecular foundations of liver disease and establish therapeutic approaches via SphK modulation.

Multifaceted roles of mitochondria in wound healing and chronic wound pathogenesis

Mitochondria are intracellular organelles that play a critical role in numerous cellular processes including the regulation of metabolism, cellular stress response, and cell fate. Mitochondria themselves are subject to well-orchestrated regulation in order to maintain organelle and cellular homeostasis. Wound healing is a multifactorial process that involves the stringent regulation of several cell types and cellular processes. In the event of dysregulated wound healing, hard-to-heal chronic wounds form and can place a significant burden on healthcare systems. Importantly, treatment options remain limited owing to the multifactorial nature of chronic wound pathogenesis. One area that has received more attention in recent years is the role of mitochondria in wound healing. With regards to this, current literature has demonstrated an important role for mitochondria in several areas of wound healing and chronic wound pathogenesis including metabolism, apoptosis, and redox signalling. Additionally, the influence of mitochondrial dynamics and mitophagy has also been investigated. However, few studies have utilised patient tissue when studying mitochondria in wound healing, instead using various animal models. In this review we dissect the current knowledge of the role of mitochondria in wound healing and discuss how future research can potentially aid in the progression of wound healing research.

The epithelial-mesenchymal plasticity landscape: principles of design and mechanisms of regulation

Epithelial-mesenchymal plasticity (EMP) enables cells to interconvert between several states across the epithelial-mesenchymal landscape, thereby acquiring hybrid epithelial/mesenchymal phenotypic features. This plasticity is crucial for embryonic development and wound healing, but also underlies the acquisition of several malignant traits during cancer progression. Recent research using systems biology and single-cell profiling methods has provided novel insights into the main forces that shape EMP, which include the microenvironment, lineage specification and cell identity, and the genome. Additionally, key roles have emerged for hysteresis (cell memory) and cellular noise, which can drive stochastic transitions between cell states. Here, we review these forces and the distinct but interwoven layers of regulatory control that stabilize EMP states or facilitate epithelial-mesenchymal transitions (EMTs) and discuss the therapeutic potential of manipulating the EMP landscape.

miR‑137 is a diagnostic tumor‑suppressive miRNA that targets SPHK2 to promote M1‑type tumor‑associated macrophage polarization

The present study investigated the expression level of microRNA (miR)-137 in glioma tissues and cell lines and explored its potential diagnostic significance as well as its function effects on glioma cells. miR-137 expression level was detected in glioma tissues using in situ hybridization, and in glioma cell lines using reverse transcription-quantitative PCR (RT-qPCR). The diagnostic significance of miR-137 in glioma was assessed using receiver operating characteristic curve analyses. Quantibody® Human Inflammation Array 1 was used to evaluate the impact of ectopic miR-137 expression on release of cytokines in glioma cell lines. IL-13, TNF-α and IFN-γ levels were detected using ELISA. To confirm that sphingosine kinase 2 (SPHK2) is a target of miR-137, RT-qPCR, western blot analysis and dual-luciferase assay were adopted. The results demonstrated that miR-137 expression was downregulated in both glioma tissues and cell lines. Downregulation of miR-137 was significantly associated with high grade gliomas. Additionally, it was found that overexpression of miR-137 reduced IL-13, but promoted TNFα and IFN-γ production. SPHK2 knockdown inhibited IL-13 release, promoted TNF-α and IFN-γ production. SPHK2 was a direct target of miR-137. Collectively, the results of the present study indicated that miR-137 expression plays a tumor-suppressive role in glioma. It is downregulated in glioma and may promote M1-type TAMs polarization, and may be a diagnostic biomarker and potential therapeutic strategy for glioma treatment in the future.

Regulation of Autophagy via Carbohydrate and Lipid Metabolism in Cancer

Metabolic changes are an important component of tumor cell progression. Tumor cells adapt to environmental stresses via changes to carbohydrate and lipid metabolism. Autophagy, a physiological process in mammalian cells that digests damaged organelles and misfolded proteins via lysosomal degradation, is closely associated with metabolism in mammalian cells, acting as a meter of cellular ATP levels. In this review, we discuss the changes in glycolytic and lipid biosynthetic pathways in mammalian cells and their impact on carcinogenesis via the autophagy pathway. In addition, we discuss the impact of these metabolic pathways on autophagy in lung cancer.

Prognostic signatures of sphingolipids: Understanding the immune landscape and predictive role in immunotherapy response and outcomes of hepatocellular carcinoma

Background

Hepatocellular carcinoma (HCC) is a complex disease with a poor outlook for patients in advanced stages. Immune cells play an important role in the progression of HCC. The metabolism of sphingolipids functions in both tumor growth and immune infiltration. However, little research has focused on using sphingolipid factors to predict HCC prognosis. This study aimed to identify the key sphingolipids genes (SPGs) in HCC and develop a reliable prognostic model based on these genes.

Methods

The TCGA, GEO, and ICGC datasets were grouped using SPGs obtained from the InnateDB portal. A prognostic gene signature was created by applying LASSO-Cox analysis and evaluating it with Cox regression. The validity of the signature was verified using ICGC and GEO datasets. The tumor microenvironment (TME) was examined using ESTIMATE and CIBERSORT, and potential therapeutic targets were identified through machine learning. Single-cell sequencing was used to examine the distribution of signature genes in cells within the TME. Cell viability and migration were tested to confirm the role of the key SPGs.

Results

We identified 28 SPGs that have an impact on survival. Using clinicopathological features and 6 genes, we developed a nomogram for HCC. The high- and low-risk groups were found to have distinct immune characteristics and response to drugs. Unlike CD8 T cells, M0 and M2 macrophages were found to be highly infiltrated in the TME of the high-risk subgroup. High levels of SPGs were found to be a good indicator of response to immunotherapy. In cell function experiments, SMPD2 and CSTA were found to enhance survival and migration of Huh7 cells, while silencing these genes increased the sensitivity of Huh7 cells to lapatinib.

Conclusion

The study presents a six-gene signature and a nomogram that can aid clinicians in choosing personalized treatments for HCC patients. Furthermore, it uncovers the connection between sphingolipid-related genes and the immune microenvironment, offering a novel approach for immunotherapy. By focusing on crucial sphingolipid genes like SMPD2 and CSTA, the efficacy of anti-tumor therapy can be increased in HCC cells.

Epithelial-to-mesenchymal transition as a learning paradigm of cell biology

Epithelial-to-mesenchymal transition (EMT) is a complex biological process that occurs during normal embryogenesis and in certain pathological conditions, particularly in cancer. EMT can be viewed as a cell biology-based process, since it involves all the cellular components, including the plasma membrane, cytoskeleton and extracellular matrix, endoplasmic reticulum, Golgi apparatus, lysosomes, and mitochondria, as well as cellular processes, such as regulation of gene expression and cell cycle, adhesion, migration, signaling, differentiation, and death. Therefore, we propose that EMT could be used to motivate undergraduate medical students to learn and understand cell biology. Here, we describe and discuss the involvement of each cellular component and process during EMT. To investigate the density with which different cell biology concepts are used in EMT research, we apply a bibliometric approach. The most frequent cell biology topics in EMT studies were regulation of gene expression, cell signaling, cell cycle, cell adhesion, cell death, cell differentiation, and cell migration. Finally, we suggest that the study of EMT could be incorporated into undergraduate disciplines to improve cell biology understanding among premedical, medical and biomedical students.

Lysosomes as a Target of Anticancer Therapy

Lysosomes are organelles containing acidic hydrolases that are responsible for lysosomal degradation and the maintenance of cellular homeostasis. They play an important role in autophagy, as well as in various cell death pathways, such as lysosomal and apoptotic death. Various agents, including drugs, can induce lysosomal membrane permeability, resulting in the translocation of acidic hydrolases into the cytoplasm, which promotes lysosomal-mediated death. This type of death may be of great importance in anti-cancer therapy, as both cancer cells with disturbed pathways leading to apoptosis and drug-resistant cells can undergo it. Important compounds that damage the lysosomal membrane include lysosomotropic compounds, antihistamines, immunosuppressants, DNA-damaging drugs, chemotherapeutics, photosensitizers and various plant compounds. An interesting approach in the treatment of cancer and the search for ways to overcome the chemoresistance of cancer cells may also be combining lysosomotropic compounds with targeted modulators of autophagy to induce cell death. These compounds may be an alternative in oncological treatment, and lysosomes may become a promising therapeutic target for many diseases, including cancer. Understanding the functional relationships between autophagy and apoptosis and the possibilities of their regulation, both in relation to normal and cancer cells, can be used to develop new and more effective anticancer therapies.

Inhibition of bromodomain-containing protein 4 enhances the migration of esophageal squamous cell carcinoma cells by inducing cell autophagy

BACKGROUND

Esophageal squamous cell carcinoma (ESCC), the predominant type of esophageal cancer, has a 5-year survival rate less than 20%. Although the cause of poor prognosis is the high incidence and mortality of ESCC, the high rate of metastasis after esophageal cancer surgery is the main cause of death after the surgery. Bromodomain-containing protein 4 (BRD4), an epigenetic reader of chromatin-acetylated histones in tumorigenesis and development, plays an essential role in regulating oncogene expression. BRD4 inhibition and BRD4 inhibition-based treatment can potentially suppress ESCC growth. However, the effects and mechanisms of action of BRD4 on ESCC cell migration remain unclear.

AIM

To explore the effect of BRD4 on cell migration of ESCC in vitro and its possible molecular mechanism.

METHODS

Human ESCC cell lines KYSE-450 and KYSE-150 were used. The 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide assay was performed to examine cell proliferation, and the transwell migration assay was conducted to test ESCC cell migration. JQ1, a BRD4 inhibitor, was applied to cells, and BRD4 siRNA was transfected into ESCC cells to knockdown endogenous BRD4. GFP-RFP-LC3 adenovirus was infected into ESCC cells to evaluate the effect of JQ1 on autophagy. Western blotting was performed to determine the protein levels of BRD4, E-cadherin, vimentin, AMP-activated protein kinase (AMPK), and p-AMPK.

RESULTS

BRD4 was either downregulated by small interfering RNA or pretreated with JQ1 in ESCC cells, leading to increased tumor migration in ESCC cells in a dose- and time-dependent manner. Inhibition of BRD4 not only significantly suppressed cell proliferation but also strongly increased cell migration by inducing epithelial-mesenchymal transition (EMT). The protein expression of vimentin was increased and E-cadherin decreased in a dose-dependent manner, subsequently promoting autophagy in KYSE-450 and KYSE-150 cells. Pretreatment with JQ1, a BRD4 inhibitor, inhibited BRD4-induced LC3-II activation and upregulated AMPK phosphorylation in a dose-dependent manner. Additionally, an increased number of autophagosomes and autolysosomes were observed in JQ1-treated ESCC cells. The autophagy inhibitor 3-methyladenine (3-MA) reversed the effects of BRD4 knockdown on ESCC cell migration and blocked JQ1-induced cell migration. 3-MA also downregulated the expression of vimentin and upregulation E-cadherin.

CONCLUSION

BRD4 inhibition enhances cell migration by inducing EMT and autophagy in ESCC cells via the AMPK-modified pathway. Thus, the facilitating role on ESCC cell migration should be considered for BRD4 inhibitor clinical application to ESCC patients.

BNIP3 enhances pancreatic cancer cell migration and proliferation via modulating autophagy under hypoxia

Chemotherapy and immunotherapy for pancreatic ductal adenocarcinoma (PDAC) have limited success for the intricated surrounding cancer microenvironment. Hypoxic microenvironment in PDAC causes the activation of multiple different molecules and signaling pathways compared with normoxia. We studied the roles of BNIP3 for the migration and proliferation of PDAC and Panc1 cells in vitro. In the present study, we found that BNIP3 expression was elevated and enhanced the migration and proliferation of CFPAC-1 and Panc1 cells under hypoxia. The upregulation of BNIP3 was important for the autophagic activation, while inhibition of autophagy with siRNA targeting Atg5 and Atg7 impaired the hypoxia-induced cell migration and proliferation. Additionally, blocking ERK1/2 mitogen-activated protein kinase (MAPK) signaling with PD98058 significantly down-regulated BNIP3 expression, autophagic activation, as well as the migration and proliferation of CFPAC-1 and Panc1 cells under hypoxia. Collectively, our results here uncover a hitherto unknown hypoxia-BNIP3-autophagy axis in modulating the migration and proliferation and provide a potential intriguing drug target for the therapy of PDAC.

TNF Receptor Associated Factor 2 (TRAF2) Signaling in Cancer

Simple Summary

Tumor necrosis factor (TNF) receptor associated factor-2 (TRAF2) is an intracellular adapter protein with E3 ligase activity, which interacts with a plethora of other signaling proteins, including plasma membrane receptors, kinases, phosphatases, other E3 ligases, and deubiquitinases. TRAF2 is involved in various cancer-relevant cellular processes, such as the activation of transcription factors of the NFκB family, stimulation of mitogen-activated protein (MAP) kinase cascades, endoplasmic reticulum (ER) stress signaling, autophagy, and the control of cell death programs. In a context-dependent manner, TRAF2 promotes tumor development but it can also act as a tumor suppressor. Based on a general description, how TRAF2 in concert with TRAF2-interacting proteins and other TRAF proteins act at the molecular level is discussed for its importance for tumor development and its potential usefulness as a therapeutic target in cancer therapy.

Abstract

Tumor necrosis factor (TNF) receptor associated factor-2 (TRAF2) has been originally identified as a protein interacting with TNF receptor 2 (TNFR2) but also binds to several other receptors of the TNF receptor superfamily (TNFRSF). TRAF2, often in concert with other members of the TRAF protein family, is involved in the activation of the classical NFκB pathway and the stimulation of various mitogen-activated protein (MAP) kinase cascades by TNFRSF receptors (TNFRs), but is also required to inhibit the alternative NFκB pathway. TRAF2 has also been implicated in endoplasmic reticulum (ER) stress signaling, the regulation of autophagy, and the control of cell death programs. TRAF2 fulfills its functions by acting as a scaffold, bringing together the E3 ligase cellular inhibitor of apoptosis-1 (cIAP1) and cIAP2 with their substrates and various regulatory proteins, e.g., deubiquitinases. Furthermore, TRAF2 can act as an E3 ligase by help of its N-terminal really interesting new gene (RING) domain. The finding that TRAF2 (but also several other members of the TRAF family) interacts with the latent membrane protein 1 (LMP1) oncogene of the Epstein–Barr virus (EBV) indicated early on that TRAF2 could play a role in the oncogenesis of B-cell malignancies and EBV-associated non-keratinizing nasopharyngeal carcinoma (NPC). TRAF2 can also act as an oncogene in solid tumors, e.g., in colon cancer by promoting Wnt/β-catenin signaling. Moreover, tumor cell-expressed TRAF2 has been identified as a major factor-limiting cancer cell killing by cytotoxic T-cells after immune checkpoint blockade. However, TRAF2 can also be context-dependent as a tumor suppressor, presumably by virtue of its inhibitory effect on the alternative NFκB pathway. For example, inactivating mutations of TRAF2 have been associated with tumor development, e.g., in multiple myeloma and mantle cell lymphoma. In this review, we summarize the various TRAF2-related signaling pathways and their relevance for the oncogenic and tumor suppressive activities of TRAF2. Particularly, we discuss currently emerging concepts to target TRAF2 for therapeutic purposes.

Sphk1-induced autophagy in microglia promotes neuronal injury following cerebral ischaemia-reperfusion

Microglial hyperactivation mediated by sphingosine kinase 1/sphingosine-1-phosphate (SphK1/S1P) signalling and the consequent inflammatory mediator production serve as the key drivers of cerebral ischaemia-reperfusion injury (CIRI). Although SphK1 reportedly controls autophagy and microglial activation, it remains uncertain as to whether SphK1 is similarly capable of regulating damage mediated by CIRI-activated microglia. In the current study, we adopted both in vitro oxygen-glucose deprivation reperfusion (OGDR) models and in vivo rat models of focal CIRI to ascertain this possibility. It was found that CIRI upregulated SphK1 and induced autophagy in microglia, while inhibiting these changes significantly impaired to prevented neuronal apoptosis. Results of mechanistic investigation revealed that SphK1 promoted autophagy via the tumour necrosis factor receptor associated factor 2 (TRAF2) pathway. Altogether, our findings unfolded to reveal a novel mechanism, whereby SphK1-induced autophagy in microglia contributed to the pathogenesis of CIRI, potentially highlighting novel avenues for future therapeutic intervention in ischaemic stroke patients.

The key role of sphingolipid metabolism in cancer: New therapeutic targets, diagnostic and prognostic values, and anti-tumor immunotherapy resistance

Biologically active sphingolipids are closely related to the growth, differentiation, aging, and apoptosis of cancer cells. Some sphingolipids, such as ceramides, are favorable metabolites in the sphingolipid metabolic pathway, usually mediating antiproliferative responses, through inhibiting cancer cell growth and migration, as well as inducing autophagy and apoptosis. However, other sphingolipids, such as S1P, play the opposite role, which induces cancer cell transformation, migration and growth and promotes drug resistance. There are also other sphingolipids, as well as enzymes, played potentially critical roles in cancer physiology and therapeutics. This review aimed to explore the important roles of sphingolipid metabolism in cancer. In this article, we summarized the role and value of sphingolipid metabolism in cancer, including the distribution of sphingolipids, the functions, and their relevance to cancer diagnosis and prognosis. We also summarized the known and potential antitumor targets present in sphingolipid metabolism, analyzed the correlation between sphingolipid metabolism and tumor immunity, and summarize the antitumor effects of natural compounds based on sphingolipids. Through the analysis and summary of sphingolipid antitumor therapeutic targets and immune correlation, we aim to provide ideas for the development of new antitumor drugs, exploration of new therapeutic means for tumors, and study of immunotherapy resistance mechanisms.

Sphingosine-1-phosphate in mitochondrial function and metabolic diseases

Sphingosine-1-phosphate (S1P) is a bioactive sphingolipid metabolite. The past decade has witnessed exponential growth in the field of S1P research, partly attributed to drugs targeting its receptors or kinases. Accumulating evidence indicates that changes in the S1P axis (i.e., S1P production, transport, and receptors) may modify metabolism and eventually mediate metabolic diseases. Dysfunction of the mitochondria on a master monitor of cellular metabolism is considered the leading cause of metabolic diseases, with aberrations typically induced by abnormal biogenesis, respiratory chain complex disorders, reactive oxygen species overproduction, calcium deposition, and mitophagy impairment. Accordingly, we discuss decades of investigation into changes in the S1P axis and how it controls mitochondrial function. Furthermore, we summarize recent scientific advances in disorders associated with the S1P axis and their involvement in the pathogenesis of metabolic diseases in humans, including type 2 diabetes mellitus and cardiovascular disease, from the perspective of mitochondrial function. Finally, we review potential challenges and prospects for S1P axis application to the regulation of mitochondrial function and metabolic diseases; these data may provide theoretical guidance for the treatment of metabolic diseases.

Epithelial–mesenchymal transition: The history, regulatory mechanism, and cancer therapeutic opportunities

Epithelial–mesenchymal transition (EMT) is a program wherein epithelial cells lose their junctions and polarity while acquiring mesenchymal properties and invasive ability. Originally defined as an embryogenesis event, EMT has been recognized as a crucial process in tumor progression. During EMT, cell–cell junctions and cell–matrix attachments are disrupted, and the cytoskeleton is remodeled to enhance mobility of cells. This transition of phenotype is largely driven by a group of key transcription factors, typically Snail, Twist, and ZEB, through epigenetic repression of epithelial markers, transcriptional activation of matrix metalloproteinases, and reorganization of cytoskeleton. Mechanistically, EMT is orchestrated by multiple pathways, especially those involved in embryogenesis such as TGFβ, Wnt, Hedgehog, and Hippo, suggesting EMT as an intrinsic link between embryonic development and cancer progression. In addition, redox signaling has also emerged as critical EMT modulator. EMT confers cancer cells with increased metastatic potential and drug resistant capacity, which accounts for tumor recurrence in most clinic cases. Thus, targeting EMT can be a therapeutic option providing a chance of cure for cancer patients. Here, we introduce a brief history of EMT and summarize recent advances in understanding EMT mechanisms, as well as highlighting the therapeutic opportunities by targeting EMT in cancer treatment.

TMCO1 expression promotes cell proliferation and induces epithelial-mesenchymal transformation in human gliomas

Transmembrane and coiled-coil domains 1 (TMCO1) is a recently discovered transmembrane protein of endoplasmic reticulum (ER), which plays a critical role in maintaining calcium homeostasis. TMCO1 dysfunction has been proved to be closely related to a variety of human diseases, including glaucoma, deformities, mental retardation and tumorigenesis. However, the role of TMCO1 in gliomas remains unclear. The purpose of this study was to detect the role of TMCO1 in the pathogenesis and progression of gliomas. This study demonstrated that TMCO1 was upregulated in gliomas and its overexpression predicted poor prognosis. We also revealed that the expression of TMCO1 was associated with the World Health Organization (WHO) grade of gliomas. Knockdown of TMCO1 inhibited the proliferation and induced apoptosis of U87 and U251 cells. In addition, TMCO1 induced GBM cell migration and invasion by promoting epithelial-mesenchymal transition (EMT). These date collectively proved the crucial role of TMCO1 as a novel prognostic factor and underlying therapeutic target for glioma patients.

TMEM139 prevents NSCLC metastasis by inhibiting lysosomal degradation of E-cadherin

Non‐small‐cell lung cancer (NSCLC) accounts for approximately 85% of all lung cancer cases and has the highest mortality rate among all solid tumors. It is characterized by early metastasis, and investigations of the molecular mechanisms underlying the progression and metastasis of NSCLC are urgently needed for the development of therapeutic targets. Here, we report that the transmembrane protein TMEM139 is significantly downregulated in NSCLC and that reduced expression of TMEM139 is correlated with a poor prognosis in NSCLC patients. Mechanistically, we found that TMEM139 directly interacts with E‐cadherin at the plasma membrane and at focal adhesion sites. Moreover, TMEM139 can prevent the lysosomal degradation of E‐cadherin, which inhibits epithelial‐mesenchymal transition, migration and invasion of NSCLC cells both in vitro and in vivo. Our study not only expands our understanding of NSCLC metastasis but also provides a foundation to develop novel therapeutic strategies.

SPHK Inhibitors and Zoledronic Acid Suppress Osteoclastogenesis and Wear Particle-Induced Osteolysis

Background: Inflammatory osteolysis induced by wear particles is the major cause of prosthetic loosening after artificial joint replacement, and its prevention and treatment are difficult worldwide. Our previous study confirmed that sphingosine kinases (SPHKs) are important mediators regulating the wear particle-induced macrophage inflammatory response. However, it is unclear whether SPHKs can modulate chronic inflammation and alleviate osteolysis. Zoledronic acid (ZA), an imidazole-containing bisphosphonate, directly affects osteoclasts and prevents bone mineral-related diseases. However, the effects of SPHK inhibitors and ZA used to treat periprosthetic osteolysis are unknown. Methods: We applied tartrate-resistant acid phosphatase (TRAP) staining to evaluate bone destruction in the interface membranes of patients with aseptic loosening and a control group. A murine calvarial osteolysis model was used to examine the preventative effect of SPHK inhibitors and ZA on osteolysis. Micro-CT scanning, immunohistochemistry (IHC), and histomorphometric analysis were conducted to determine the variations in inflammatory osteolysis. The effects of different drug concentrations on cell viability were evaluated using the Cell Counting Kit-8 (CCK-8) assay. Real-time quantitative polymerase chain reaction (RT-qPCR) analysis was performed to confirm the reduced expression of osteoclast-specific genes after drug and titanium treatment. The osteoclast formation and functions of the drugs were analyzed using TRAP staining in vivo and in vitro. The effect of SPHKs/S1P-TRAF2-BECN1 signaling pathways was verified via RT-qPCR and tissue IHC. Results: In this study, we found that SPHK inhibitors (ABC294640 and FTY720) combined with ZA decreased the degree of inflammatory osteolysis in vivo. However, ABC294640 and ZA suppressed osteoclast differentiation and osteoclast-specific genes in vitro. SPHKs regulate the inflammatory osteolysis induced by wear particles by increasing the expression of SPHKs/S1P-TRAF2-BECN1. Conclusion: Our study revealed that wear particles could induce inflammatory osteolysis by upregulating SPHKs/S1P-TRAF2-BECN1 and SPHK inhibitors/ZA inhibit osteoclastogenesis in vitro and prevent inflammatory osteolysis in vivo, suggesting that SPHK inhibitors and ZA can be a new perspective and scientific basis for the prevention and treatment of prosthesis loosening.

Emerging roles of epithelial-mesenchymal plasticity in invasion-metastasis cascade and therapy resistance

Strong association of cancer incidence and its progression with mortality highlights the need to decipher the cellular and molecular mechanisms that drive tumor cells to rapidly progress to metastatic disease and therapy resistance. Epithelial-mesenchymal plasticity (EMP) emerged as a key regulator of metastatic outgrowth. It allows neoplastic epithelial cells to delaminate from their neighbors either individually or collectively, traverse the extracellular matrix (ECM) barrier, enter into the circulation, and establish distal metastases. Plasticity between epithelial and mesenchymal states and the existence of hybrid epithelial/mesenchymal (E/M) phenotypes are increasingly being reported in different tumor contexts. Small subset of cancer cells with stemness called cancer stem cells (CSCs) exhibit plasticity, possess high tumorigenic potential, and contribute to high degree of tumoral heterogeneity. EMP characterized by the presence of dynamic intermediate states is reported to be influenced by (epi)genomic reprograming, growth factor signaling, inflammation, and low oxygen generated by tumor stromal microenvironment. EMP alters the genotypic and phenotypic characteristics of tumor cells/CSCs, disrupts tissue homeostasis, induces the reprogramming of angiogenic and immune recognition functions, and renders tumor cells to survive hostile microenvironments and resist therapy. The present review summarizes the roles of EMP in tumor invasion and metastasis and provides an update on therapeutic strategies to target the metastatic and refractory cancers.

Methylation silencing of ULK2 via epithelial-mesenchymal transition causes transformation to poorly differentiated gastric cancers

BACKGROUND

Diffuse-type gastric cancers (DGC) typically have a poor prognosis related to their invasion and metastasis, in which the epithelial-mesenchymal transition (EMT) is the initiation step. ULK2 plays a role in the autophagy initiation, which might provide a survival advantage in cancer cells. Although knock-down of ULK2 reportedly induces autophagy and EMT in a lung cancer cell line, the mechanism of EMT via the down-regulation of ULK2, as well as its clinical significance, remains yet unclear. The present study, therefore, aims at clarifying this mechanism and its clinical significance in gastric cancers.

METHODS

We examined ULK2 mRNA expression in gastric cancer tissues and normal gastric tissues of healthy people. The effects of knock-downed ULK2 were examined in two gastric cancer cells, which were investigated in terms of their gene expression changes by the mRNA microarray.

RESULTS

ULK2 was strongly expressed in intestinal-type cancers but was scarcely expressed in DGC by immunohistochemical staining. Furthermore, we found that ULK2 was methylated in DGC and was unmethylated in corresponding adjacent normal tissues. Then, we validated whether knock-down of ULK2 could induce autophagy, cell migration, and EMT in NUGC3 and MKN45 cells. Using mRNA microarray analysis, we confirmed that knock-down of ULK2 changed expressions of oncogenic genes associated with cell migration and EMT. Autophagy inhibitor suppressed cell migration and EMT induced by knock-down of ULK2 in NUGC3 and MKN45.

CONCLUSION

Methylation silencing of ULK2 could induce cell migration and EMT by means of autophagy induction, causing transformation to poorly differentiated cancers.

Prognostic value and underlying mechanism of autophagy-related genes in bladder cancer

Bladder cancer (BLCA) is the most common malignancy whose early diagnosis can ensure a better prognosis. However, the predictive accuracy of commonly used predictors, including patients’ general condition, histological grade, and pathological stage, is insufficient to identify the patients who need invasive treatment. Autophagy is regarded as a vital factor in maintaining mitochondrial function and energy homeostasis in cancer cells. Whether autophagy-related genes (ARGs) can predict the prognosis of BLCA patients deserves to be investigated. Based on BLCA data retrieved from the Cancer Genome Atlas and ARGs list obtained from the Human Autophagy Database website, we identified prognosis-related differentially expressed ARGs (PDEARGs) through Wilcox text and constructed a PDEARGs-based prognostic model through multivariate Cox regression analysis. The predictive accuracy, independent forecasting capability, and the correlation between present model and clinical variables or tumor microenvironment were evaluated through R software. Enrichment analysis of PDEARGs was performed to explore the underlying mechanism, and a systematic prognostic signature with nomogram was constructed by integrating clinical variables and the aforementioned PDEARGs-based model. We found that the risk score generated by PDEARGs-based model could effectively reflect deteriorated clinical variables and tumor-promoting microenvironment. Additionally, several immune-related gene ontology terms were significantly enriched by PDEARGs, which might provide insights for present model and propose potential therapeutic targets for BLCA patients. Finally, a systematic prognostic signature with promoted clinical utility and predictive accuracy was constructed to assist clinician decision. PDEARGs are valuable prognostic predictors and potential therapeutic targets for BLCA patients.

Identification of Epithelial Mesenchymal Transition-Related lncRNAs Associated with Prognosis and Tumor Immune Microenvironment of Hepatocellular Carcinoma

Purpose. The long noncoding RNAs (lncRNAs) play the important role in tumor occurrence and progression, and the epithelial to mesenchymal transition (EMT) is the critical process for tumor migration. However, the role of EMT-related lncRNA in hepatocellular carcinoma (HCC) has not been elucidated. Methods. In this study, we selected the EMT-related lncRNAs in HCC by using data from The Cancer Genome Atlas database (TCGA). Two prognostic models of the overall survival (OS) and relapse-free survival (RFS) were constructed and validated through Cox regression model, Kaplan-Meier analysis, and the receiver-operating characteristic (ROC) curves. The unsupervised clustering analysis was utilized to investigate the association between EMT-lncRNAs with tumor immune microenvironment. ESTIMATE algorithm and gene set enrichment analysis (GSEA) were used to estimate tumor microenvironment and associated KEGG pathways. Results. Two EMT-related lncRNA prognostic models of OS and RFS were constructed. Kaplan-Meier curves showed the dismal prognosis of OS and RFS in the group with high-risk score. The ROC curves and AUC values in two prognostic models indicated the discriminative value in the training set and validation set. Patients with HCC were clustered into two subgroups according the unsupervised clustering analysis. Lnc-CCNY-1 was selected as the key lncRNA. GSVA analysis showed that lnc-CCNY-1 was negatively associated with peroxisome proliferator-activated receptor (PPAR) signaling pathway and positively correlated with CELL cycle pathway. Conclusion. Two EMT-related lncRNA prognostic models of OS and RFS were constructed to discriminate patients and predict prognosis of HCC. EMT-related lncRNAs may play a role on prognosis of HCC by influencing the immune microenvironment. Lnc-CCNY-1 was selected as the key EMT-related lncRNA for further exploration.

The Epithelial-Mesenchymal Transition at the Crossroads between Metabolism and Tumor Progression

The transition between epithelial and mesenchymal phenotype is emerging as a key determinant of tumor cell invasion and metastasis. It is a plastic process in which epithelial cells first acquire the ability to invade the extracellular matrix and migrate into the bloodstream via transdifferentiation into mesenchymal cells, a phenomenon known as epithelial–mesenchymal transition (EMT), and then reacquire the epithelial phenotype, the reverse process called mesenchymal–epithelial transition (MET), to colonize a new organ. During all metastatic stages, metabolic changes, which give cancer cells the ability to adapt to increased energy demand and to withstand a hostile new environment, are also important determinants of successful cancer progression. In this review, we describe the complex interaction between EMT and metabolism during tumor progression. First, we outline the main connections between the two processes, with particular emphasis on the role of cancer stem cells and LncRNAs. Then, we focus on some specific cancers, such as breast, lung, and thyroid cancer.

Biomimetic nanoparticles blocking autophagy for enhanced chemotherapy and metastasis inhibition via reversing focal adhesion disassembly

BACKGROUND

Autophagy is a conserved catabolic process, which plays an important role in regulating tumor cell motility and degrading protein aggregates. Chemotherapy-induced autophagy may lead to tumor distant metastasis and even chemo-insensitivity in the therapy of hepatocellular carcinoma (HCC). Therefore, a vast majority of HCC cases do not produce a significant response to monotherapy with autophagy inhibitors.

RESULTS

In this work, we developed a biomimetic nanoformulation (TH-NP) co-encapsulating Oxaliplatin (OXA)/hydroxychloroquine (HCQ, an autophagy inhibitor) to execute targeted autophagy inhibition, reduce tumor cell migration and invasion in vitro and attenuate metastasis in vivo. The tumor cell-specific ligand TRAIL was bioengineered to be stably expressed on HUVECs and the resultant membrane vesicles were wrapped on OXA/HCQ-loaded PLGA nanocores. Especially, TH-NPs could significantly improve OXA and HCQ effective concentration by approximately 21 and 13 times in tumor tissues compared to the free mixture of HCQ/OXA. Moreover, the tumor-targeting TH-NPs released HCQ alkalized the acidic lysosomes and inhibited the fusion of autophagosomes and lysosomes, leading to effective blockade of autophagic flux. In short, the system largely improved chemotherapeutic performance of OXA on subcutaneous and orthotopic HCC mice models. Importantly, TH-NPs also exhibited the most effective inhibition of tumor metastasis in orthotopic HCCLM3 models, and in the HepG2, Huh-7 or HCCLM3 metastatic mice models. Finally, we illustrated the enhanced metastasis inhibition was attributed to the blockade or reverse of the autophagy-mediated degradation of focal adhesions (FAs) including E-cadherin and paxillin.

CONCLUSIONS

TH-NPs can perform an enhanced chemotherapy and antimetastatic effect, and may represent a promising strategy for HCC therapy in clinics.

The Autophagic Route of E-Cadherin and Cell Adhesion Molecules in Cancer Progression

Simple Summary

A hallmark of carcinoma progression is the loss of epithelial integrity. In this context, the deregulation of adhesion molecules, such as E-cadherin, affects epithelial structures and associates with epithelial to mesenchymal transition (EMT). This, in turn, fosters cancer progression. Autophagy endows cancer cells with the ability to overcome intracellular and environmental stress stimuli, such as anoikis, nutrient deprivation, hypoxia, and drugs. Furthermore, it plays an important role in the degradation of cell adhesion proteins and in EMT. This review focuses on the interplay between the turnover of adhesion molecules, primarily E-cadherin, and autophagy in cancer progression.

Abstract

Cell-to-cell adhesion is a key element in epithelial tissue integrity and homeostasis during embryogenesis, response to damage, and differentiation. Loss of cell adhesion and gain of mesenchymal features, a phenomenon known as epithelial to mesenchymal transition (EMT), are essential steps in cancer progression. Interestingly, downregulation or degradation by endocytosis of epithelial adhesion molecules (e.g., E-cadherin) associates with EMT and promotes cell migration. Autophagy is a physiological intracellular degradation and recycling process. In cancer, it is thought to exert a tumor suppressive role in the early phases of cell transformation but, once cells have gained a fully transformed phenotype, autophagy may fuel malignant progression by promoting EMT and conferring drug resistance. In this review, we discuss the crosstalk between autophagy, EMT, and turnover of epithelial cell adhesion molecules, with particular attention to E-cadherin.

PCBP1 regulates the transcription and alternative splicing of metastasis‑related genes and pathways in hepatocellular carcinoma

PCBP1 is a multifunctional RNA-binding protein (RBP) expressed in most human cells and is involved in posttranscriptional gene regulation. PCBP1 regulates the alternative splicing, translation and RNA stability of many cancer-related genes and has been identified as a potential tumour suppressor gene. PCBP1 inhibits the invasion of hepatocellular carcinoma (HCC) cells, but there are few studies on the specific regulatory target and mechanism of RBPs in HCC, and it is unclear whether PCBP1 plays a role in tumour metastasis as a splicing factor. We analysed the regulation of gene expression by PCBP1 at the transcriptional level. We obtained and analysed PCBP1-knockdown RNA-seq data and eCLIP-seq data of PCBP1 in HepG2 cells and found that PCBP1 widely regulates the alternative splicing and expression of genes enriched in cancer-related pathways, including extracellular matrix, cell adhesion, small molecule metabolic process and apoptosis. We validated five regulated alternative splicing events affected by PCBP1 using RT-qPCR and found that there was a significant difference in the expression of APOC1 and SPHK1 between tumour and normal tissues. In this study, we provided convincing evidence that human PCBP1 profoundly regulates the splicing of genes associated with tumour metastasis. These findings provide new insight into potential markers or therapeutic targets for HCC treatment.

CHD1L augments autophagy-mediated migration of hepatocellular carcinoma through targeting ZKSCAN3

Autophagy is an important biological process in normal cells. However, how it affects tumor progression still remains poorly understood. Herein, we demonstrated that the oncogenic protein Chromodomain-helicase-DNA-binding-protein 1-like gene (CHD1L) might promote HCC cells migration and metastasis through autophagy. CHD1L could bind to the promotor region of Zinc finger with KRAB and SCAN domain 3 (ZKSCAN3), a pivotal autophagy suppressor, and inhibit its transcription. We established inducible CHD1L conditional knockout cell line (CHD1L-iKO cell) and found that the deletion of CHD1L significantly increased ZKSCAN3 expression both at mRNA and protein level. Deletion of CHD1L impaired the autophagic flux and migration of HCC cells, while specifically inhibiting ZKSCAN3 blocked these effects. Further exploration demonstrated that the enhanced tumor cell migration and metastasis induced by CHD1L was mediated through ZKSCAN3-induced autophagic degradation of Paxillin. In summary, we have characterized a previously unknown function of CHD1L in regulating tumor migration via ZKSCAN3-mediated autophagy in HCC. Further inhibition of CHD1L and its downstream autophagy signaling might shed new light on cancer therapeutics.

Sphk1 promotes salivary adenoid cystic carcinoma progression via PI3K/Akt signaling

The progression of salivary adenoid cystic carcinoma (SACC) is closely related to abnormal gene expression. Herein, the role of Sphk1 in SACC was explored. Sphk1 was overexpressed in SACC tissues. In SACC cell lines, Sphk1 induced cell proliferation, inhibited apoptosis, and promoted cell migration. Moreover, Sphk1 overexpression induced up-regulation of the PI3K protein level and AKT phosphorylation level. Rescue assays further showed that activation of the Sphk1 /PI3K/Akt pathway affected various biological functions of SACC cells. Together, these findings suggested that Sphk1 promotes salivary tumorigenesis by activating the PI3K/ Akt pathway, which may provide novel intervention targets for SACC treatment.