Facilitate Cancer Metastasis Research Articles

Exosomal miR-4745-5p/3911 from N2-polarized tumor-associated neutrophils promotes gastric cancer metastasis by regulating SLIT2

Tumor cells remodel the phenotype and function of tumor microenvironment (TME) cells to favor tumor progression. Previous studies have shown that neutrophils in TME are polarized to N2 tumor-associated neutrophils (TANs) by tumor derived factors, thus promoting tumor growth and metastasis, angiogenesis, therapy resistance, and immunosuppression. Exosomes act as critical intercellular messengers in human health and diseases including cancer. So far, the biological roles of exosomes from N2 TANs in gastric cancer have not been well characterized. Herein, we represented the first report that exosomes from N2 TANs promoted gastric cancer metastasis in vitro and in vivo. We found that exosomes from N2 TANs transferred miR-4745-5p/3911 to gastric cancer cells to downregulate SLIT2 (slit guidance ligand 2) gene expression. Adenovirus-mediated overexpression of SLIT2 reversed the promotion of gastric cancer metastasis by N2 TANs derived exosomes. We further revealed that gastric cancer cells induced glucose metabolic reprogramming in neutrophils through exosomal HMGB1 (high mobility group protein B1)/NF-κB pathway, which mediated neutrophil N2 polarization and miR-4745-5p/3911 upregulation. We further employed ddPCR (droplet digital PCR) to detect the expression of miR-4745-5p/3911 in N2 TANs exosomes from human serum samples and found their increased levels in gastric cancer patients compared to healthy controls and benign gastric disease patients. Conclusively, our results indicate that N2 TANs facilitate cancer metastasis via regulation of SLIT2 in gastric cancer cells by exosomal miR-4745-5p/3911, which provides a new insight into the roles of TME cells derived exosomes in gastric cancer metastasis and offers a potential biomarker for gastric cancer diagnosis.

Aberrant alternative splicing in cancer: Splicing events and their regulatory mechanisms (Review).

Alternative RNA splicing provides cells with transcriptomic and proteomic diversity by adding another layer of regulation to gene expression. Accumulating evidence has revealed that defects in alternative splicing contribute to a variety of features of cancer development, including the modulation of cancer heterogeneity, evasion of apoptosis of cancer cells, rewiring cancer metabolism and facilitating cancer metastasis via fine‑tuning the epithelial‑to‑mesenchymal transition process. In this review, well‑known aberrant alternative splicing events associated with multiple aspects of cancer progression were presented based on available data obtained from an extensive literature search used to construct splicing regulatory networks for each of these events. The study aims to provide a more comprehensive understanding of cancer‑associated splicing networks and more precise guidance for targeting these events for cancer treatment.

GPX4 transcriptionally promotes liver cancer metastasis via GRHL3/PTEN/PI3K/AKT axis

Hepatocellular carcinoma (HCC) is among the most fatal types of malignancy, with a high prevalence of relapse and limited treatment options. As a critical regulator of ferroptosis and redox homeostasis, glutathione peroxidase 4 (GPX4) is commonly upregulated in HCC and is hypothesized to facilitate cancer metastasis, but this has not been fully explored in HCC. Here, we report that up-regulated GPX4 expression in HCC is strongly associated with tumor metastasis. FACS-based in vivo and in vitro analysis revealed that a cell subpopulation featuring lower cellular reactive oxygen species levels and ferroptosis resistance were involved in GPX4-mediated HCC metastasis. Mechanistically, GPX4 overexpressed in HCC tumor cells was enriched in the nucleus and transcriptionally silenced GRHL3 expression, thereby activating PTEN/PI3K/AKT signaling and promoting HCC metastasis. Functional studies demonstrated that GPX4 amino acids 110–145 are a binding site that interacts with the GRHL3 promoter. As AKT is a downstream target of GPX4, we combined the AKT inhibitor, AKT-IN3, with lenvatinib to effectively inhibit HCC tumor cell metastasis. Overall, these results indicate that the GPX4/GRHL3/PTEN/PI3K/AKT axis controls HCC cell metastasis and lenvatinib combined with AKT-IN3 represents a potential therapeutic strategy for patients with metastatic HCC.

Enhancing liquid biopsies are a promising approach for the early detection of cancer

Cancer is a formidable threat to human life, a cure for which in advanced stages remains challenging. Early detection and treatment of cancer are paramount, yet a substantial number of cancer patients receive diagnoses at an advanced stage, resulting in a lower 5-year survival rate. Early-stage cancers, however, frequently elude detection. Conventional tumor screening techniques, such as tumor biopsy, serve as essential means for an early cancer diagnosis. However, these procedures are invasive and may inadvertently facilitate cancer metastasis. A current research focal point involves liquid biopsy technologies, offering a potential solution to mitigate the above-mentioned issues, but often exhibiting low sensitivity. A research team from the Massachusetts Institute of Technology has recently pioneered an innovative approach to enhance the sensitivity of liquid biopsy for cancer diagnosis. By administering a pre-treatment agent 1–2 h prior to sampling, a greater than 10-fold increase in collected ctDNA was obtained. Subsequent tumor analysis using ctDNA not only demonstrated heightened sensitivity in detecting small tumors (>75%) but also presented a promising avenue for early clinical cancer detection and diagnosis. This discovery holds significant potential for advancing the prospects of early cancer detection, diagnosis, and treatment.

Docetaxel Inhibits Epithelial-Mesenchymal Transition in Human Mammary Cells.

Epithelial-mesenchymal transition (EMT) is a reversible and dynamic biological process in which epithelial cells acquire mesenchymal characteristics including enhanced stemness and migratory ability. EMT can facilitate cancer metastasis and is a known driver of cellular resistance to common chemotherapeutic drugs, such as docetaxel. Current chemotherapeutic practices such as docetaxel treatment can promote EMT and increase the chance of tumor recurrence and resistance, calling for new approaches in cancer treatment. Here we show that prolonged docetaxel treatment at a sub-IC50 concentration inhibits EMT in immortalized human mammary epithelial (HMLE) cells. Using immunofluorescence, flow cytometry, and bulk transcriptomic sequencing to assess EMT progression, we analyzed a range of cellular markers of EMT in docetaxel-treated cells and observed an upregulation of epithelial markers and downregulation of mesenchymal markers in the presence of docetaxel. This finding suggests that docetaxel may have clinical applications not only as a cytotoxic drug but also as an inhibitor of EMT-driven metastasis and multidrug resistance depending on the concentration of its use.

FTO facilitates cancer metastasis by modifying the m6A level of FAP to induce integrin/FAK signaling in non-small cell lung cancer

BackgroundEmerging evidence suggests the critical roles of N6-methyladenosine (m6A) RNA modification in tumorigenesis and tumor progression. However, the role of m6A in non-small cell lung cancer (NSCLC) is still unclear. This study aimed to explore the role of the m6A demethylase fat mass and obesity-associated protein (FTO) in the tumor metastasis of NSCLC.MethodsA human m6A epitranscriptomic microarray analysis was used to identify downstream targets of FTO. Quantitative real-time PCR (qRT‒PCR) and western blotting were employed to evaluate the expression levels of FTO and FAP in NSCLC cell lines and tissues. Gain-of-function and loss-of-function assays were conducted in vivo and in vitro to assess the effects of FTO and FAP on NSCLC metastasis. M6A-RNA immunoprecipitation (MeRIP), RNA immunoprecipitation (RIP), luciferase reporter assays, and RNA stability assays were used to explore the mechanism of FTO action. Co-immunoprecipitation (co-IP) assays were used to determine the mechanism of FAP in NSCLC metastasis.ResultsFTO was upregulated and predicted poor prognosis in patients with NSCLC. FTO promoted cell migration and invasion in NSCLC, and the FAK inhibitor defactinib (VS6063) suppressed NSCLC metastasis induced by overexpression of FTO. Mechanistically, FTO facilitated NSCLC metastasis by modifying the m6A level of FAP in a YTHDF2-dependent manner. Moreover, FTO-mediated metastasis formation depended on the interactions between FAP and integrin family members, which further activated the FAK signaling.ConclusionOur current findings provided valuable insights into the role of FTO-mediated m6A demethylation modification in NSCLC metastasis. FTO was identified as a contributor to NSCLC metastasis through the activation of the FAP/integrin/FAK signaling, which may be a potential therapeutic target for NSCLC.EwEnNquqUtx8DT1YGQrFDqVideo

Gut microbiota: key facilitator in metastasis of colorectal cancer.

Colorectal cancer (CRC) ranks third in terms of incidence among all kinds of cancer. The main cause of death is metastasis. Recent studies have shown that the gut microbiota could facilitate cancer metastasis by promoting cancer cells proliferation, invasion, dissemination, and survival. Multiple mechanisms have been implicated, such as RNA-mediated targeting effects, activation of tumor signaling cascades, secretion of microbiota-derived functional substances, regulation of mRNA methylation, facilitated immune evasion, increased intravasation of cancer cells, and remodeling of tumor microenvironment (TME). The understanding of CRC metastasis was further deepened by the mechanisms mentioned above. In this review, the mechanisms by which the gut microbiota participates in the process of CRC metastasis were reviewed as followed based on recent studies.

The adaptor protein TRAF3 is an immune checkpoint that inhibits myeloid-derived suppressor cell expansion.

Myeloid-derived suppressor cells (MDSCs) are aberrantly expanded in cancer patients and under other pathological conditions. These cells orchestrate the immunosuppressive and inflammatory network to facilitate cancer metastasis and mediate patient resistance to therapies, and thus are recognized as a prime therapeutic target of human cancers. Here we report the identification of the adaptor protein TRAF3 as a novel immune checkpoint that critically restrains MDSC expansion. We found that myeloid cell-specific Traf3-deficient (M-Traf3 -/-) mice exhibited MDSC hyperexpansion during chronic inflammation. Interestingly, MDSC hyperexpansion in M-Traf3 -/- mice led to accelerated growth and metastasis of transplanted tumors associated with an altered phenotype of T cells and NK cells. Using mixed bone marrow chimeras, we demonstrated that TRAF3 inhibited MDSC expansion via both cell-intrinsic and cell-extrinsic mechanisms. Furthermore, we elucidated a GM-CSF-STAT3-TRAF3-PTP1B signaling axis in MDSCs and a novel TLR4-TRAF3-CCL22-CCR4-G-CSF axis acting in inflammatory macrophages and monocytes that coordinately control MDSC expansion during chronic inflammation. Taken together, our findings provide novel insights into the complex regulatory mechanisms of MDSC expansion and open up unique perspectives for the design of new therapeutic strategies that aim to target MDSCs in cancer patients.

Exosome-transmitted miR-29a induces colorectal cancer metastasis by destroying the vascular endothelial barrier.

Metastasis is the leading cause of colorectal cancer treatment failure and mortality. Communication between endothelium and tumor cells in the tumor microenvironment is required for cancer metastasis. Tumor-derived exosomes have been shown to increase vascular permeability by delivering microRNA (miRNA) to vascular endothelial cells, facilitating cancer metastasis. The mechanism by which Epithelial-mesenchymal transition (EMT) tumor cell-derived exosomes influence vascular permeability remains unknown. MicroRNA-29a (miR-29a) expression is up-regulated in colorectal cancer (CRC) tissues, which is clinically significant in metastasis. Exosomal miR-29a secreted by EMT-CRC cells has been found to decrease the expression of Zonula occlusion 1 (ZO-1), Claudin-5, and Occludin via targeting Kruppel-like factor 4 (KLF4). In vitro co-culture investigations further revealed that EMT-cancer cells release exosomal miR-29a, which alters vascular endothelial permeability. Furthermore, exosomal miR-29a promoted liver metastases in CRC mice. Our findings demonstrate that EMT-CRC cells may transport exosomal miR-29a to endothelial cells in the tumor microenvironment (TME). As a result, increased vascular permeability promotes the development and metastasis of CRC. Exosomal miR-29a has the potential to be a predictive marker for tumor metastasis as well as a viable therapeutic target for CRC.

Exploration and identification of anoikis-related genes in polycythemia vera.

Background: Polycythemia Vera (PV) is a type of typical Myeloproliferative Neoplasms (MPNs) characterized with excessive erythropoiesis and thrombosis. Anoikis is a special programmed cell death mode induced by the adhesion disorder between cells and extracellular matrix (ECM) or adjacent cells facilitating cancer metastasis. However, few studies have focused on the role of anoikis in PV, especially on the development of PV. Methods: The microarray and RNA-seq results were screened from the Gene Expression Omnibus (GEO) database and the anoikis-related genes (ARGs) were downloaded from Genecards. The functional enrichment analysis of intersecting differentially expressed genes (DEGs) and protein-protein interaction (PPI) network analysis were performed to discover hub genes. The hub genes expression was tested in the training (GSE136335) and validation cohort (GSE145802), and RT-qPCR was performed to verify the gene expression in PV mice. Results: In the training GSE136335, a total of 1,195 DEGs was obtained from Myeloproliferative Neoplasm (MPN) patients compared with controls, among which 58 were anoikis-related DEGs. The significant enrichment of the apoptosis and cell adhesion pathways (i.e., cadherin binding) were shown in functional enrichment analysis. The PPI network was conducted to identify top five hub genes (CASP3, CYCS, HIF1A, IL1B, MCL1). The expression of CASP3 and IL1B were significantly upregulated both in validation cohort and PV mice and downregulated after treatment, suggesting that CASP3 and IL1B could be important indicators for disease surveillance. Conclusion: Our research revealed a relationship between anoikis and PV for the first time by combined analysis of gene level, protein interaction and functional enrichment, allowing novel insights into mechanisms of PV. Moreover, CASP3 and IL1B may become promising indicators of PV development and treatment.

Capsaicin shapes gut microbiota and pre-metastatic niche to facilitate cancer metastasis to liver

Dietary factors are fundamental in tumorigenesis throughout our lifetime. A spicy diet has been ambiguous on the development of cancers, especially in the study of colon cancer metastasis. Here, we utilized a mouse metastasis model to test the potential role of capsaicin in influencing metastasis. Long-term continuous administration of capsaicin diet (300 mg/kg) to mice promotes the formation of liver pre-metastatic niche to facilitate the metastasis of colon cancer cells. Bacteria translocation to liver is clearly observed. Capsaicin increases intestinal barrier permeability and disrupts gut vascular barrier by altering the composition of gut microbiota. Capsaicin not only changes the abundance of mucin-related bacteria like Akkermanisa and Muribaculaceae, but also bacteria involved in bile acids metabolism. Dysregulated bile acids profile is related to the recruitment of natural killer T (NKT) cells in pre-metastatic niche, primary bile acid α-Muricholic acid can enhance the recruitment of NKT cells, while secondary bile acids Glycoursodeoxycholic acid and Taurohyodeoxycholic acid impair the recruitment of NKT cells. These findings reveal long term consumption of capsaicin increases the risk of cancer metastasis through modulating the gut microbiota. Capsaicin (300 mg/kg) disrupts gut barrier and promotes the translocation of bacteria to liver, while altered bile acids metabolism affects the recruitment of NKT cells in liver, forming a pre-metastatic niche and promoting cancer metastasis.

An ultrasensitive FRET-based fluorescent low molecular weight heparin nanoprobe for quantifying heparanase activity

Heparanase (HPA) is a multifaceted endo-β-glucuronidase, and its dysregulation facilitates cancer metastasis. Developing techniques for fast and sensitively monitoring HPA enzymatic activity is crucial for searching for molecular therapies targeting HPA. Herein, we developed a novel fluorescence resonance energy transfer (FRET)-based nanoprobe AuNCs-LMWH-AuNRs, with AuNCs@GSH-cys and AuNRs/end-NH2/side-SiO2 attached to the non-reducing terminus and reducing terminus of low molecular weight heparin (LMWH), respectively. AuNCs@GSH-cys exhibited an absolute quantum yield of 1.1%. The absorption spectra of AuNRs/end-NH2/side-SiO2 (825 nm for maximum longitudinal absorption) and the emission spectra of AuNCs@GSH-cys (824 nm for maximum emission) were precisely overlapping, further enhancing the efficiency of FRET. In the presence of HPA, the LMWH nanoprobe exhibited an ultrasensitive response with excitation/emission wavelength (lambda (ex) = 560 nm, lambda (em) = 824 nm). The probe presented a wide linear dynamic detection range (LDR) of 0.125 ng/μL - 0.01 μg/μL in vitro with a limit of detection (LODs) of 82.15 pM (0.43 pg/μL). The excellent selectivity and good fluorescence turn-on efficiency of the probe made it possible for one-step detection of cellular heparanase activity. High throughput screening of HPA inhibitors also can be accomplished using the highly efficient LMWH nanoprobe.

The Role of MARCKS in Metastasis and Treatment Resistance of Solid Tumors.

Simple SummaryCancer metastasis is a critical event in the progression of solid tumors and is invariably associated with adverse outcomes and mortality. Understanding novel mechanisms or molecules that promote cancer metastasis will facilitate the development of new strategies for cancer treatment. Recently, MARCKS has been studied extensively in several cancers and has been implicated in tumor progression and metastasis. This review summarizes recent advances in the understanding of MARCKS on cancer metastasis, stemness, and therapeutic resistance and provides prospects on targeting MARCKS therapeutically. Specifically, we review the molecular mechanisms and multiple signaling pathways by which MARCKS contributes to the progression and metastasis in solid tumors.The myristoylated alanine-rich C-kinase substrate (MARCKS) is a membrane-associated protein kinase C (PKC) substrate ubiquitously expressed in eukaryotic cells. MARCKS plays important roles in multiple cellular processes, including cell adhesion and motility, mucin secretion, exocytosis, and inflammatory response. Aberrant MARCKS signaling has been observed in the development and progression of multiple cancer types. In addition, MARCKS facilitates cancer metastasis through modulating cancer cell migration and invasion. Moreover, MARCKS contributes to treatment resistance, likely by promoting cancer stem cell renewal as well as immunosuppression. In this review, we describe MARCKS protein structure, cellular localization, and biological functions. We then discuss the role of MARCKS in cancer metastasis as well as its mechanisms of action in solid tumors. Finally, we review recent advances in targeting MARCKS as a new therapeutic strategy in cancer management.

Abstract 2646: Novel, isoform selective PAD4 inhibitors for the treatment of cancer

Abstract Background: Peptidyl Arginine Deiminase 4 (PAD4/PADI4) is an enzyme that converts protein arginine or mono-methylarginine to citrulline. The PAD4-mediated hyper citrullination reaction in neutrophils causes the release of nuclear chromatin to form a chromatin network termed Neutrophil Extracellular Traps (NETs). NETs have been shown to be associated with several pathological processes including, fibrosis, ischemic stroke, preeclampsia, thrombosis, cancers, and other autoimmune diseases. In the context of cancer, tumors secrete chemokines such as CXCL1 and GCSF to recruit and prime neutrophils to form NETs, which in turn, facilitate cancer metastasis by forming Circulating Tumor Cell (CTC) clusters and potentially increasing tumor cell extravasation. Therefore, cancer cell endogenous PAD4 seems to play a significant role in metastasis, and inhibition of PAD4 could be a novel strategy to inhibit cancer progression and metastasis. Here, we describe a series of novel small molecule PAD4 inhibitors that are selective and orally bioavailable for the treatment of cancer. Methods: Potency and selectivity were evaluated in ammonia release assay using recombinant PAD enzymes. Cellular potency was evaluated by assessing the modulation of citrullination in a human neutrophil-based assay. ADME surrogates and PK studies were conducted using appropriate preclinical models. In vivo efficacy studies were conducted in syngeneic mice tumor models. Results: Multiple leads with strong in vitro potency on PAD4 (< 0.200 µM) were identified. One of the leads (JTxPAD4i) showed an IC50 of 0.102 µM against recombinant human PAD4 in the biochemical assay and a similar potency on mouse PAD4. It was selective against PAD1, PAD2, and PAD3 enzymes (IC50 > 10 µM). In the human neutrophil-based assay, JTxPAD4i inhibited H3-Histone citrullination with an IC50 of 0.125 µM. It showed an oral bioavailability of greater than 50% across species, including mouse, rat, and dog. Oral dosing with JTxPAD4i at 50 mg/kg, BID, in 4T1 mice syngeneic breast cancer model resulted in ~50% tumor growth inhibition (TGI) as compared to ~35% TGI with anti-PD1 antibody and was well tolerated. TGI was associated with strong inhibition of histone citrullination and myeloperoxidase (MPO) that are markers for NET formation. There was also a strong and significant inhibition in inflammatory cytokines, including IL-6, IL-17, and IL-1β in the tumor. Similar TGI was observed in additional breast and lung cancer syngeneic models with more than one PAD4 inhibitor from our lead series. Further studies with our lead molecules are underway to elucidate the mechanism of action of these PAD4 inhibitors. Conclusion: These studies clearly emphasize the potential of PAD4 inhibition in the treatment of cancer and our lead PAD4 inhibitors are being profiled in advanced toxicology studies to be developed as a clinical candidate. Citation Format: Dhanalakshmi Sivanandhan, Sridharan Rajagopal, Chandru G, Mohd Zainuddin, Naveen Sadhu, Ramachandraiah Gosu, Luca Rastelli, Amir Siddiqui, Sharad Singh, Rudresh G, Sadanand Mullurwar, Saravanan Kandan, Santosh Vishwakarma, Gurulingappa Hallur, Ravi Trivedi, Jeyaraj D A. Novel, isoform selective PAD4 inhibitors for the treatment of cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2646.

Exclusion of NUMB Exon12 Controls Cancer Cell Migration through Regulation of Notch1-SMAD3 Crosstalk.

NUMB is an endocytic adaptor protein that contains four isoforms (p65, p66, p71 and p72) due to alternative splicing regulation. Here, we show that NUMB exon12 (E12)-skipping isoforms p65/p66 promote epithelial to mesenchymal transition (EMT) and cancer cell migration in vitro, and facilitate cancer metastasis in mice, whereas E12-included p71/p72 isoforms attenuate these effects. Mechanistically, p65/p66 isoforms significantly increase the sorting of Notch1 through early endosomes (EEs) for enhanced Notch1 activity. In contrast, p71/p72 isoforms act as negative regulators of Notch1 by ubiquitylating the Notch1 intracellular domain (N1ICD) and promoting its degradation. Moreover, we observed that the interaction between N1ICD and SMAD3 is important for their own stabilization, and for NUMB-mediated EMT response and cell migration. Either N1ICD or SMAD3 overexpression could significantly recuse the migration reduction seen in the p65/p66 knockdown, and Notch1 or SMAD3 knockdown rescued the migration advantage seen in the overexpression of p66. Taken all together, our study provides mechanistic insights into the opposite regulation of Notch1-SMAD3 crosstalk by NUMB isoforms and identifies them as critical regulators of EMT and cancer cell migration.

Effect of HIT Components on the Development of Breast Cancer Cells.

Cancer cells circulating in blood vessels activate platelets, forming a cancer cell encircling platelet cloak which facilitates cancer metastasis. Heparin (H) is frequently used as an anticoagulant in cancer patients but up to 5% of patients have a side effect, heparin-induced thrombocytopenia (HIT) that can be life-threatening. HIT is developed due to a complex interaction among multiple components including heparin, platelet factor 4 (PF4), HIT antibodies, and platelets. However, available information regarding the effect of HIT components on cancers is limited. Here, we investigated the effect of these materials on the mechanical property of breast cancer cells using atomic force microscopy (AFM) while cell spreading was quantified by confocal laser scanning microscopy (CLSM), and cell proliferation rate was determined. Over time, we found a clear effect of each component on cell elasticity and cell spreading. In the absence of platelets, HIT antibodies inhibited cell proliferation but they promoted cell proliferation in the presence of platelets. Our results indicate that HIT complexes influenced the development of breast cancer cells.

TGF-β1 Facilitates TAp63α Protein Lysosomal Degradation to Promote Pancreatic Cancer Cell Migration.

Simple SummaryNumerous studies demonstrate that the activation of transforming growth factor-β (TGF-β) signaling is a critical driving force for promoting cancer cell migration and tumor metastasis. Our recent study indicates that TGF-β1 promotes FBXO3-mediated ΔNp63α protein degradation to facilitate cancer metastasis. In this study, we show that TGF-β1 can inhibit TAp63α protein stability in a lysosome-dependent, but canonical Smad pathway-independent manner, which leads to upregulation of p53-R248W expression, and consequently results in increased pancreatic cancer cell migration.TGF-β signaling plays a pivotal role in promoting tumor cell migration and cancer metastasis. ΔNp63α and TAp63α are two major isoforms of p53-related p63 protein. Our recent study has shown that TGF-β1 promotes ΔNp63α protein degradation to facilitate cancer metastasis. However, whether TAp63α is involved in TGF-β1-induced cancer metastasis remains unclear. In this study, we show that, in human pancreatic cancer MIA PaCa-2 cells harboring p53-R248W allele, TGF-β1 can significantly inhibit TAp63α protein stability in a Smad pathway-independent manner. Lysosome inhibitor, chloroquine, but not proteasome inhibitor MG132, can rescue TGF-β1-induced downregulation of TAp63α protein. In addition, we show that either TGF-β1 treatment or silencing of TAp63α can dramatically increase migration of MIA PaCa-2 cells. Importantly, the restored expression of TAp63α can effectively block TGF-β1-induced migration of MIA PaCa-2 cells. Mechanistically, we show that TGF-β1 promotes TAp63α protein degradation, leading to upregulation of p53-R248W protein expression, and consequently resulting in elevated MIA PaCa-2 cell migration. Together, this study indicates that lysosomal degradation is an important way for regulating TAp63α protein fate and highlights that TGF-β1-TAp63α-mutant p53 axis is critically important in pancreatic cancer metastasis.

Exosomes in ovarian cancer ascites promote epithelial\u2013mesenchymal transition of ovarian cancer cells by delivery of miR-6780b-5p

The poor prognosis of ovarian cancer is mainly due to metastasis, and the specific mechanism underlying ovarian cancer metastasis is not clear. Ascites-derived exosomes (ADEs) play an important role in the progression of ovarian cancer, but the mechanism is unknown. Here, we found that ADEs promoted ovarian cancer metastasis not only in vitro but also in vivo. This promotive function was based on epithelial–mesenchymal transition (EMT) of ovarian cancer cells. Bioinformatics analysis of RNA sequencing microarray data indicated that miR-6780b-5p may be the key microRNA (miRNA) in ADEs that facilitates cancer metastasis. Moreover, the expression of exosomal miR-6780b-5p correlated with tumor metastasis in ovarian cancer patients. miR-6780b-5p overexpression promoted and miR-6780b-5p downregulation suppressed EMT of ovarian cancer cells. These results suggest that ADEs transfer miR-6780b-5p to ovarian cancer cells, promoting EMT and finally facilitating ovarian cancer metastasis.

P68 RNA Helicase facilitates Breast Cancer progression by promoting Proliferation and Migration via PDGFR-β/AR axis.

Aberrant expression of P68 RNA helicase (p68), a prototypical member of the DEAD box family of RNA helicases, contributes to tumor development and progression. P68 tyrosine phosphorylation induced by PDGF signaling facilitates cancer metastasis by promoting EMT. In this report, we show that p68 promotes breast cancer cell EMT and cell migration by upregulation of PDGF receptor β (PDGFR-β). Knockdown of p68 in MDA-MB-231 and BT549 cells significantly decreases PDGFR-β both in mRNA and protein levels. P68 promotes EMT and cell migration in response to PDGF-BB stimulation via upregulation of PDGFR-β, suggesting that p68 enhances PDGF signaling by a positive feedback loop in cancer cells. Furthermore, our study reveals that p68 mediates the effects of PDGFR-β in regulation of androgen receptor (AR) in breast cancer cells. We demonstrate that p68 and PDGFR-β co-regulate AR expression and promote androgen-mediated proliferation in breast cancer cells. Our studies uncover an important pathway of p68-PDGFR-β axis in promoting breast cancer progression.

AMPK maintains TCA cycle through sequential phosphorylation of PDHA to promote tumor metastasis.

Cancer represents the leading public health problem throughout the world. Globally, about one out of six deaths is related to cancer, which is largely due to the metastatic lesions. However, there are no effective strategies for targeting cancer metastasis. Identification of the key druggable targets maintaining metastasis is crucial for cancer treatment. In our recent study (Cai et al. (2020), Mol Cell, doi: 10.1016/j.molcel.2020.09.018), we found that activity of AMPK was enriched in metastatic tumors compared to primary tumors. Depletion of AMPK rendered cancer cells more sensitive to metabolic and oxidative stress, leading to the impairment of breast cancer lung metastasis. Activation of AMPK rewired cancer metabolism towards TCA cycle, which protects disseminated cancer cells from both metabolic and oxidative stress-induced cell death, and facilitates cancer metastasis. Further, AMPK critically maintained the activity of pyruvate dehydrogenase complex (PDH), the rate limiting enzyme involved in TCA cycle, thus favoring the pyruvate metabolism towards TCA cycle rather than converting it to lactate. Mechanistically, AMPK was shown to co-localize with PDHA, the catalytic subunit of PDH, in the mitochondrial matrix and directly triggered the phosphorylation of PDHA on Ser295 and Ser314. Hyper-phosphorylation of Ser295 and Ser314 of PDHA promotes lung metastasis through elevating activity of PDH. Of note, PDHA Ser314 phosphorylation abrogated the interaction between PDHA and PDHKs leading to the dephosphorylation on previously reported S293 site, whose phosphorylation serves as a negative signal for PDH activation, while S295 phosphorylation serves as an intrinsic catalytic site required for pyruvate metabolism. Our study presented the first evidence for the pro-metastatic property of the AMPK-PDH axis and advance our current understanding of how PDH is activated under physiological and pathological conditions.