Metastasis and immunosuppression promoted by mtDNA and PD-L1 in extracellular vesicles are reversed by WGP ß-glucan in oral squamous cell carcinoma.

The suppressive regulatory T cells (Treg) are frequently upregulated in cancer patients. This study aims to demonstrate the hypothesis that arecoline could induce the secretion of mitochondrial (mt) DNA D-loop and programmed cell death-ligand 1 (PD-L1) in extracellular vesicles (EVs), and attenuate T-cell immunity by upregulated Treg cell numbers. However, the immunosuppression could be reversed by whole glucan particle (WGP) ß-glucan in oral squamous cell (OSCC) patients. Arecoline-induced reactive oxygen specimen (ROS) production and cytosolic mtDNA D-loop were analyzed in OSCC cell lines. mtDNA D-loop, PD-L1, IFN-γ, and Treg cells were also identified for the surgical specimens and sera of 60 OSCC patients. We demonstrated that higher mtDNA D-loop, PD-L1, and Treg cell numbers were significantly correlated with larger tumor size, nodal metastasis, advanced clinical stage, and areca quid chewing. Furthermore, multivariate analysis confirmed that higher mtDNA D-loop levels and Treg cell numbers were unfavorable independent factors for survival. Arecoline significantly induced cytosolic mtDNA D-loop leakage and PD-L1 expression, which were packaged by EVs to promote immunosuppressive Treg cell numbers. However, WGP ß-glucan could elevate CD4+ and CD8+ T-cell numbers, mitigate Treg cell numbers, and promote oral cancer cell apoptosis. To sum up, arecoline induces EV production carrying mtDNA D-loop and PD-L1, and in turn elicits immune suppression. However, WGP ß-glucan potentially enhances dual effects on T-cell immunity and cell apoptosis and we highly recommend its integration with targeted and immune therapies against OSCC.

Mitochondrial Lon-induced mitophagy benefits hypoxic resistance via Ca2+-dependent FUNDC1 phosphorylation at the ER-mitochondria interface.

During hypoxia, FUNDC1 acts as a mitophagy receptor and accumulates at the ER (endoplasmic reticulum)-mitochondria contact sites (EMC), also called mitochondria-associated membranes (MAM). In mitophagy, the ULK1 complex phosphorylates FUNDC1(S17) at the EMC site. However, how mitochondria sense the stress and send the signal from the inside to the outside of mitochondria to trigger mitophagy is still unclear. Mitochondrial Lon was reported to be localized at the EMC under stress although the function remained unknown. In this study, we explored the mechanism of how mitochondrial sensors of hypoxia trigger and stabilize the FUNDC1-ULK1 complex by Lon in the EMC for cell survival and cancer progression. We demonstrated that Lon is accumulated in the EMC and associated with FUNDC1-ULK1 complex to induce mitophagy via chaperone activity under hypoxia. Intriguingly, we found that Lon-induced mitophagy is through binding with mitochondrial Na+/Ca2+ exchanger (NCLX) to promote FUNDC1-ULK1-mediated mitophagy at the EMC site in vitro and in vivo. Accordingly, our findings highlight a novel mechanism responsible for mitophagy initiation under hypoxia by chaperone Lon in mitochondria through the interaction with FUNDC1-ULK1 complex at the EMC site. These findings provide a direct correlation between Lon and mitophagy on cell survival and cancer progression.

A Fc-VEGF chimeric fusion enhances PD-L1 immunotherapy via inducing immune reprogramming and infiltration in the immunosuppressive tumor microenvironment.

BACKGROUND: Immunotherapy is an emerging cancer therapy with potential great success; however, immune checkpoint inhibitor (e.g., anti-PD-1) has response rates of only 10-30% in solid tumor because of the immunosuppressive tumor microenvironment (TME). This affliction can be solved by vascular normalization and TME reprogramming. METHODS: By using the single-cell RNA sequencing (scRNAseq) approach, we tried to find out the reprogramming mechanism that the Fc-VEGF chimeric antibody drug (Fc-VFD) enhances immune cell infiltration in the TME. RESULTS: In this work, we showed that Fc-VEGF121-VEGF165 (Fc-VEGF chimeric antibody drug, Fc-VFD) arrests excess angiogenesis and tumor growth through vascular normalization using in vitro and in vivo studies. The results confirmed that the treatment of Fc-VFD increases immune cell infiltration including cytotoxic T, NK, and M1-macrophages cells. Indeed, Fc-VFD inhibits Lon-induced M2 macrophages polarization that induces angiogenesis. Furthermore, Fc-VFD inhibits the secretion of VEGF-A, IL-6, TGF-ß, or IL-10 from endothelial, cancer cells, and M2 macrophage, which reprograms immunosuppressive TME. Importantly, Fc-VFD enhances the synergistic effect on the combination immunotherapy with anti-PD-L1 in vivo. CONCLUSIONS: In short, Fc-VFD fusion normalizes intratumor vasculature to reprogram the immunosuppressive TME and enhance cancer immunotherapy.

Mitochondrial oxidative stress in the tumor microenvironment and cancer immunoescape: foe or friend?

The major concept of "oxidative stress" is an excess elevated level of reactive oxygen species (ROS) which are generated from vigorous metabolism and consumption of oxygen. The precise harmonization of oxidative stresses between mitochondria and other organelles in the cell is absolutely vital to cell survival. Under oxidative stress, ROS produced from mitochondria and are the major mediator for tumorigenesis in different aspects, such as proliferation, migration/invasion, angiogenesis, inflammation, and immunoescape to allow cancer cells to adapt to the rigorous environment. Accordingly, the dynamic balance of oxidative stresses not only orchestrate complex cell signaling events in cancer cells but also affect other components in the tumor microenvironment (TME). Immune cells, such as M2 macrophages, dendritic cells, and T cells are the major components of the immunosuppressive TME from the ROS-induced inflammation. Based on this notion, numerous strategies to mitigate oxidative stresses in tumors have been tested for cancer prevention or therapies; however, these manipulations are devised from different sources and mechanisms without established effectiveness. Herein, we integrate current progress regarding the impact of mitochondrial ROS in the TME, not only in cancer cells but also in immune cells, and discuss the combination of emerging ROS-modulating strategies with immunotherapies to achieve antitumor effects.

Lon upregulation contributes to cisplatin resistance by triggering NCLX-mediated mitochondrial Ca2+ release in cancer cells.

Mitochondria are the major organelles in sensing cellular stress and inducing the response for cell survival. Mitochondrial Lon has been identified as an important stress protein involved in regulating proliferation, metastasis, and apoptosis in cancer cells. However, the mechanism of retrograde signaling by Lon on mitochondrial DNA (mtDNA) damage remains to be elucidated. Here we report the role of Lon in the response to cisplatin-induced mtDNA damage and oxidative stress, which confers cancer cells on cisplatin resistance via modulating calcium levels in mitochondria and cytosol. First, we found that cisplatin treatment on oral cancer cells caused oxidative damage of mtDNA and induced Lon expression. Lon overexpression in cancer cells decreased while Lon knockdown sensitized the cytotoxicity towards cisplatin treatment. We further identified that cisplatin-induced Lon activates the PYK2-SRC-STAT3 pathway to stimulate Bcl-2 and IL-6 expression, leading to the cytotoxicity resistance to cisplatin. Intriguingly, we found that activation of this pathway is through an increase of intracellular calcium (Ca2+) via NCLX, a mitochondrial Na+/Ca2+ exchanger. We then verified that NCLX expression is dependent on Lon levels; Lon interacts with and activates NCLX activity. NCLX inhibition increased the level of mitochondrial calcium and sensitized the cytotoxicity to cisplatin in vitro and in vivo. In summary, mitochondrial Lon-induced cisplatin resistance is mediated by calcium release into cytosol through NCLX, which activates calcium-dependent PYK2-SRC-STAT3-IL-6 pathway. Thus, our work uncovers the novel retrograde signaling by mitochondrial Lon on resistance to cisplatin-induced mtDNA stress, indicating the potential use of Lon and NCLX inhibitors for better clinical outcomes in chemoresistant cancer patients.

ß-glucan therapy converts the inhibition of myeloid-derived suppressor cells in oral cancer patients.

OBJECTIVES: The myeloid-derived suppressor cells (MDSCs) frequently have a high expansion in cancer patients. This research explored whether administration of ß-glucan could increase anti-tumor immunity in oral squamous cell carcinoma (OSCC) patients. MATERIALS AND METHODS: This study evaluated the MDSC level of circulating blood as CD33+ /CD11b+ /HLA-DR-/low by flow cytometry in 30 healthy donors (HDs, group I), in 48 oral squamous cell carcinoma (OSCC) patients before and after 14-day preoperative administration of ß-glucan (group II), and in 52 OSCC patients without taking ß-glucan (group III). RESULTS: A significantly higher mean MDSC level was observed in 100 OSCC patients than in 30 HDs (p < .001). There was a significant reduction of the mean MDSC level in group II patients after taking ß-glucan (p < .001). Moreover, we discovered a significantly higher recurrence-free survival (RFS) in group II than in group III patients (p = .026). Finally, the multivariate Cox regression further identified the MDSC level ≤1% and administration of ß-glucan as more favorable prognostic factors for OSCC patients. CONCLUSION: Preoperative administration of ß-glucan can augment anti-tumor immunity and increase RFS rate via subversion of suppressive function of MDSC in OSCC patients.

Sharpening up tumor microenvironment to enhance the efficacy of immune checkpoint blockade on head and neck cancer using a CpG-oligodeoxynucleotide.

Head and neck cancers are a type of life-threatening cancers characterized by an immunosuppressive tumor microenvironment. Only less than 20% of the patients respond to immune checkpoint blockade therapy, indicating the need for a strategy to increase the efficacy of immunotherapy for this type of cancers. Previously, we identified a type B CpG-oligodeoxynucleotide (CpG-ODN) called CpG-2722, which has the universal activity of eliciting an immune response in grouper, mouse, and human cells. In this study, we further characterized and compared its cytokine-inducing profiles with different types of CpG-ODNs. The antitumor effect of CpG-2722 was further investigated alone and in combination with an immune checkpoint inhibitor in a newly developed syngeneic orthotopic head and neck cancer animal model. Along with other inflammatory cytokines, CpG-2722 induces the gene expressions of interleukin-12 and different types of interferons, which are critical for the antitumor response. Both CpG-2722 and anti-programmed death (PD)-1 alone suppressed tumor growth. Their tumor suppression efficacies were further enhanced when CpG-2722 and anti-PD-1 were used in combination. Mechanistically, CpG-2722 shaped a tumor microenvironment that is favorable for the action of anti-PD-1, which included promoting the expression of different cytokines such as IL-12, IFN-ß, and IFN-γ, and increasing the presence of plasmacytoid dendritic cells, M1 macrophages, and CD8 positive T cells. Overall, CpG-2722 provided a priming effect for CD8 positive T cells by sharpening the tumor microenvironment, whereas anti-PD-1 released the brake for their tumor-killing effect, resulting in an enhanced efficacy of the combined CpG-2722 and anti-PD-1.

Insulin-like growth factor binding protein 3 promotes radiosensitivity of oral squamous cell carcinoma cells via positive feedback on NF-κB/IL-6/ROS signaling.

BACKGROUND: Ectopic insulin-like growth factor binding protein 3 (IGFBP3) expression has been shown to enhance cell migration and lymph node metastasis of oral squamous cell carcinoma (OSCC) cells. However, OSCC patients with high IGFBP3 expression had improved survival compared with those with low expression. Therefore, we speculated that IGFBP3 expression may play a role in response to conventional OSCC therapies, such as radiotherapy. METHODS: We used in vitro and in vivo analyses to explore IGFBP3-mediated radiosensitivity. Reactive oxygen species (ROS) detection by flow cytometry was used to confirm IGFBP3-mediated ionizing radiation (IR)-induced apoptosis. Geneset enrichment analysis (GSEA) and ingenuity pathway analysis (IPA) were used to analyze the relationship between IGFBP3 and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling. Assays involving an NF-κB inhibitor, ROS scavenger or interleukin 6 (IL-6) were used to evaluate the NF-κB/IL-6/ROS signaling in IGFBP3-mediated radiosensitivity. RESULTS: Ectopic IGFBP3 expression enhanced IR-induced cell-killing in vitro. In vivo, IGFBP3 reduced tumor growth and increased apoptotic signals of tumor tissues in immunocompromised mice treated with IR. Combined with IR, ectopic IGFBP3 expression induced mitochondria-dependent apoptosis, which was apparent through mitochondrial destruction and increased ROS production. Ectopic IGFBP3 expression enhanced NK-κB activation and downstream cytokine expression. After IR exposure, IGFBP3-induced NF-κB activation was inhibited by the ROS scavenger N-acetyl-L-cysteine (NAC). IGFBP3-mediated ROS production was reduced by the NF-κB inhibitor BMS-345541, while exogenous IL-6 rescued the NF-κB-inhibited, IGFBP3-mediated ROS production. CONCLUSIONS: Our data demonstrate that IGFBP3, a potential biomarker for radiosensitivity, promotes IR-mediated OSCC cell death by increasing ROS production through NF-κB activation and cytokine production.

Establishment of an Immunocompetent Metastasis Rat Model with Hepatocyte Cancer Stem Cells.

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer mortality. Cancer stem cells (CSCs) are responsible for the maintenance, metastasis, and relapse of various tumors. The effects of CSCs on the tumorigenesis of HCC are still not fully understood, however. We have recently established two new rat HCC cell lines HTC and TW-1, which we isolated from diethylnitrosamine-induced rat liver cancer. Results showed that TW-1 expressed the genetic markers of CSCs, including CD133, GSTP1, CD44, CD90, and EpCAM. Moreover, TW-1 showed higher tolerance to sorafenib than HTC did. In addition, tumorigenesis and metastasis were observed in nude mice and wild-type rats with TW-1 xenografts. Finally, we combined highly expressed genes in TW-1/HTC with well-known biomarkers from recent HCC studies to predict HCC-related biomarkers and able to identify HCC with AUCs > 0.9 after machine learning. These results indicated that TW-1 was a novel rat CSC line, and the mice or rat models we established with TW-1 has great potential on HCC studies in the future.

Mitochondrial Lon-induced mtDNA leakage contributes to PD-L1-mediated immunoescape via STING-IFN signaling and extracellular vesicles.

BACKGROUND: Mitochondrial Lon is a chaperone and DNA-binding protein that functions in protein quality control and stress response pathways. The level of Lon regulates mitochondrial DNA (mtDNA) metabolism and the production of mitochondrial reactive oxygen species (ROS). However, there is little information in detail on how mitochondrial Lon regulates ROS-dependent cancer immunoescape through mtDNA metabolism in the tumor microenvironment (TME). METHODS: We explored the understanding of the intricate interplay between mitochondria and the innate immune response in the inflammatory TME. RESULTS: We found that oxidized mtDNA is released into the cytosol when Lon is overexpressed and then it induces interferon (IFN) signaling via cGAS-STING-TBK1, which upregulates PD-L1 and IDO-1 expression to inhibit T-cell activation. Unexpectedly, upregulation of Lon also induces the secretion of extracellular vehicles (EVs), which carry mtDNA and PD-L1. Lon-induced EVs further induce the production of IFN and IL-6 from macrophages, which attenuates T-cell immunity in the TME. CONCLUSIONS: The levels of mtDNA and PD-L1 in EVs in patients with oral cancer function as a potential diagnostic biomarker for anti-PD-L1 immunotherapy. Our studies provide an insight into the immunosuppression on mitochondrial stress and suggest a therapeutic synergy between anti-inflammation therapy and immunotherapy in cancer.

Mitochondrial oxidative stress by Lon-PYCR1 maintains an immunosuppressive tumor microenvironment that promotes cancer progression and metastasis.

Mitochondrial Lon is a chaperone protein whose upregulation increases the production of mitochondrial reactive oxygen species (ROS). However, there is a lack of information in detail on how mitochondrial Lon regulates cancer metastasis through ROS production in the tumor microenvironment (TME). Our results show that elevated Lon promotes epithelial-mesenchymal transition (EMT) via ROS-dependent p38 and NF-κB-signaling. We further identified pyrroline-5-carboxylate reductase 1 (PYCR1) as a client of chaperone Lon, which induces mitochondrial ROS and EMT by Lon. Mitochondrial Lon induces ROS-dependent production of inflammatory cytokines, such as TGF-ß, IL-6, IL-13, and VEGF-A, which consequently activates EMT, angiogenesis, and M2 macrophage polarization. In addition, Lon expression is induced upon the activation and M2 polarization of macrophages, which further promotes M2 macrophages to enhance the immunosuppressive microenvironment and metastatic behaviors in the TME. This raises the possibility that manipulation of the mitochondrial redox balance in the TME may serve as a therapeutic strategy to improve T cell function in cancer immunotherapy.

Unlocking the Mystery of the Therapeutic Effects of Chinese Medicine on Cancer.

Over the past decade, the rise of cancer immunotherapy has coincided with a remarkable breakthrough in cancer therapy, which attracted increased interests in public. The scientific community clearly showed that the emergence of immunotherapy is an inevitable outcome of a holistic approach for cancer treatment. It is well established that traditional Chinese medicine (TCM) utilizes the principle of homeostasis and balance to adjust the healthy status of body. TCM treatment toward cancer has a long history, and the diagnosis and treatment of tumors were discussed in the ancient and classical literatures of Chinese medicine, such as the Yellow Emperor's Inner Canon. Precious heritage has laid the foundation for the innovation and development of cancer treatment with TCM. The modern study indicated that TCM facilitates the treatment of cancer and enhances the survival rate and life expectancy of patients. However, the pharmacological mechanisms underlying these effects are not yet completely understood. In addition, physicians cannot always explain why the TCM treatment is effective and the mechanism of action cannot be explained in scientific terms. Here, we attempted to provide insights into the development of TCM in the treatment and interpret how TCM practitioners treat cancer through six general principles of TCM by using modern scientific language and terms based on newly discovered evidence.

A time-saving-modified Giemsa stain is a better diagnostic method of Helicobacter pylori infection compared with the rapid urease test.

BACKGROUND: Despite having chronic gastritis, most people infected by Helicobacter pylori (H. pylori) are asymptomatic and have no specific clinical signs and symptoms. H. pylori infection can be diagnosed by several detection methods. Giemsa stain and rapid urease test (CLO test) are the most performed tests of H. pylori infection at first-line clinical examination because of their simplicity and reliability. However, the sensitivity of CLO test is significantly reduced in patients with atrophic gastritis and intestinal metaplasia, and the weaknesses of Giemsa stain are higher cost and time-consuming. METHODS: The Giemsa stain was modified in several staining solutions and procedures based on the simplified Giemsa technique described by Gray, Wyatt, & Rathbone (1986). The modified Giemsa stain is examined its efficacy and compared with the CLO test using 233 H. pylori-infected patients with gastric disease. RESULTS: The modified Giemsa stain is comparable to the traditional one. Statistical analysis indicated that the modified Giemsa stain obtains greater accuracy in H. pylori-infected patients with gastritis and ulcer than the CLO test (48.1% vs. 43.7%). Moreover, considering the prognosis of different symptoms of gastric diseases, the modified Giemsa stain has a more accurate prognosis than combination symptoms (P = 1.8E-05 vs. P = 5.49E-05). The modified Giemsa stain is confirmed to be better than CLO test using 233 H. pylori-infected patients with gastric disease. CONCLUSIONS: The modified Giemsa stain is more simplified and time-saving than traditional Giemsa stain, which is comparable to the traditional one and is confirmed to be better than CLO test using 233 H. pylori-infected patients with gastric disease. In clinical examination, this modified Giemsa stain can be applied to routine examination and provides quick and accurate diagnosis and prognosis to H. pylori-infected patients with gastric diseases.

Correction: USP17 mediates macrophage-promoted inflammation and stemness in lung cancer cells by regulating TRAF2/TRAF3 complex formation.

A correction to this paper has been published and can be accessed via a link at the top of the paper.

TDP-43 induces mitochondrial damage and activates the mitochondrial unfolded protein response.

Mutations in or dys-regulation of the TDP-43 gene have been associated with TDP-43 proteinopathy, a spectrum of neurodegenerative diseases including Frontotemporal Lobar Degeneration (FTLD) and Amyotrophic Lateral Sclerosis (ALS). The underlying molecular and cellular defects, however, remain unclear. Here, we report a systematic study combining analyses of patient brain samples with cellular and animal models for TDP-43 proteinopathy. Electron microscopy (EM) analyses of patient samples revealed prominent mitochondrial impairment, including abnormal cristae and a loss of cristae; these ultrastructural changes were consistently observed in both cellular and animal models of TDP-43 proteinopathy. In these models, increased TDP-43 expression induced mitochondrial dysfunction, including decreased mitochondrial membrane potential and elevated production of reactive oxygen species (ROS). TDP-43 expression suppressed mitochondrial complex I activity and reduced mitochondrial ATP synthesis. Importantly, TDP-43 activated the mitochondrial unfolded protein response (UPRmt) in both cellular and animal models. Down-regulating mitochondrial protease LonP1 increased mitochondrial TDP-43 levels and exacerbated TDP-43-induced mitochondrial damage as well as neurodegeneration. Together, our results demonstrate that TDP-43 induced mitochondrial impairment is a critical aspect in TDP-43 proteinopathy. Our work has not only uncovered a previously unknown role of LonP1 in regulating mitochondrial TDP-43 levels, but also advanced our understanding of the pathogenic mechanisms for TDP-43 proteinopathy. Our study suggests that blocking or reversing mitochondrial damage may provide a potential therapeutic approach to these devastating diseases.

AXL phosphorylates and up-regulates TNS2 and its implications in IRS-1-associated metabolism in cancer cells.

BACKGROUND: TNS2 is a focal adhesions protein and a binding partner for many proteins, including the receptor tyrosine kinase Axl. Although TNS2 can bind with Axl, the details of their interactions have not been elucidated. TNS2 is involved in IRS-1 signaling pathway. In this study, we confirmed the relationship between TNS2 expression and the expression of Axl, IRS-1, PDK1 and Glut4 in pancreatic cancer patients. METHODS: The expression levels of TNS2, Axl, IRS-1, PDK1 and Glut4 in human cancer cells were measured by Western blot and/or IP-Western blot assays. Paired samples of pancreatic cancer and non-cancer tissues were obtained from 33 patients and were used to construct tissue microarrays. The expression levels of these markers in the tissue microarrays were measured by enzyme-linked Immunohistochemistry assay, and the relationships were analyzed by Pearson's chi-square test and two-tailed t-test analysis. RESULTS: We demonstrated for the first time that TNS2 is a phosphorylation substrate of Axl. Moreover, we found a positive relationship between TNS2 expression and the expression of Axl, IRS-1, PDK1 and Glut4 in pancreatic cancer patients. Based on these results, we suggest that Axl modulates glucose metabolism potentially through TNS2 and IRS-1. We hypothesize that there exists a novel mechanism whereby Axl binds to and phosphorylates TNS2, releasing TNS2 from interaction with IRS-1 and resulting in increased stability of IRS-1. The two key enzymes of aerobic glycolysis (Glut4 and PDK1) were found to be up-regulated by Axl/TNS2/IRS-1 cross-talk and may play a critical role in glucose metabolism of cancer cells. CONCLUSIONS: Our results revealed for the first time that Axl binds to and phosphorylates TNS2 and that Axl/TNS2/IRS-1 cross-talk may potentially play a critical role in glucose metabolism of cancer cells.

Identification of Novel Cdc7 Kinase Inhibitors as Anti-Cancer Agents that Target the Interaction with Dbf4 by the Fragment Complementation and Drug Repositioning Approach.

BACKGROUND: Cdc7-Dbf4 is a conserved serine/threonine kinase that plays an important role in initiation of DNA replication and DNA damage tolerance in eukaryotic cells. Cdc7 has been found overexpressed in human cancer cell lines and tumor tissues, and the knockdown of Cdc7 expression causes an p53-independent apoptosis, suggesting that Cdc7 is a target for cancer therapy. Only a handful Cdc7 kinase inhibitors have been reported. All Cdc7 kinase inhibitors, including PHA-767491, were identified and characterized as ATP-competitive inhibitors. Unfortunately, these ATP-competitive Cdc7 inhibitors have no good effect on clinical trial. METHODS: Here, we have developed a novel drug-screening platform to interrupt the interaction between Cdc7 and Dbf4 based on Renilla reniformis luciferase (Rluc)-linked protein-fragment complementation assay (Rluc-PCA). Using drug repositioning approach, we found several promising Cdc7 inhibitors for cancer therapy from a FDA-approved drug library. FINDINGS: Our data showed that dequalinium chloride and clofoctol we screened inhibit S phase progression, accumulation in G2/M phase, and Cdc7 kinase activity. In addition, in vivo mice animal study suggests that dequalinium chloride has a promising anti-tumor activity in oral cancer. Interestingly, we also found that dequalinium chloride and clofoctol sensitize the effect of platinum compounds and radiation due to synergistic effect. In conclusion, we identified non-ATP-competitive Cdc7 kinase inhibitors that not only blocks DNA synthesis at the beginning but also sensitizes cancer cells to DNA damage agents. INTERPRETATION: The inhibitors will be a promising anti-cancer agent and enhance the therapeutic effect of chemotherapy and radiation for current cancer therapy. FUND: This work was supported by grants from the Ministry of Science and Technology, Ministry of Health and Welfare, and National Health Research Institutes, Taiwan.

USP17 mediates macrophage-promoted inflammation and stemness in lung cancer cells by regulating TRAF2/TRAF3 complex formation.

Macrophage accumulation and inflammation in the lung owing to stresses and diseases is a cause of lung cancer development. However, molecular mechanisms underlying the interaction between macrophages and cancer cells, which drive inflammation and stemness in cancers, are poorly understood. In this study, we investigated the expression of ubiquitin-specific peptidase 17 (USP17) in lung cancers, and role of elevated USP17 in the interaction between macrophages and lung cancer cells. USP17 expression in lung cancers was associated with poor prognosis, macrophage, and inflammatory marker expressions. Macrophages promoted USP17 expression in cancer cells. TNFR-associated factor (TRAF) 2-binding and TRAF3-binding motifs were identified in USP17, through which it interacted with and disrupted the TRAF2/TRAF3 complex. This stabilized its client proteins, enhanced inflammation and stemness in cancer cells, and promoted macrophage recruitment. In different animal studies, co-injection of macrophages with cancer cells promoted USP17 expression in tumors and tumor growth. Conversely, depletion of macrophages in host animals by clodronate liposomes reduced USP17 expression and tumor growth. In addition, overexpression of USP17 in cancer cells promoted tumor growth and inflammation-associated and stemness-associated gene expressions in tumors. These results suggested that USP17 drives a positive-feedback interaction between macrophages and cancer cells to enhance inflammation and stemness in cancer cells, and promotes lung cancer growth.

Mitochondrial Lon sequesters and stabilizes p53 in the matrix to restrain apoptosis under oxidative stress via its chaperone activity.

Mitochondrial Lon is a multi-function matrix protease with chaperone activity. However, little literature has been undertaken into detailed investigations on how Lon regulates apoptosis through its chaperone activity. Accumulating evidences indicate that various stresses induce transportation of p53 to mitochondria and activate apoptosis in a transcription-independent manner. Here we found that increased Lon interacts with p53 in mitochondrial matrix and restrains the apoptosis induced by p53 under oxidative stress by rescuing the loss of mitochondrial membrane potential (Δψm) and the release of cytochrome C and SMAC/Diablo. Increased chaperone Lon hampers the transcription-dependent apoptotic function of p53 by reducing the mRNA expression of p53 target genes. The ATPase mutant (K529R) of chaperone Lon decreases the interaction with p53 and fails to inhibit apoptosis. Furthermore, the chaperone activity of Lon is important for mitochondrial p53 accumulation in an mtHsp70-dependent manner, which is also important to prevent the cytosolic distribution of p53 from proteasome-dependent degradation. These results indicate that the chaperone activity of Lon is important to bind with mitochondrial p53 by which increased Lon suppresses the apoptotic function of p53 under oxidative stress. Furthermore, mitochondrial Lon-mtHsp70 increases the stability/level of p53 through trafficking and retaining p53 in mitochondrial matrix and preventing the pool of cytosolic p53 from proteasome-dependent degradation in vitro and in clinic.

Cdc7-Dbf4-mediated phosphorylation of HSP90-S164 stabilizes HSP90-HCLK2-MRN complex to enhance ATR/ATM signaling that overcomes replication stress in cancer.

Cdc7-Dbf4 kinase plays a key role in the initiation of DNA replication and contributes to the replication stress in cancer. The activity of human Cdc7-Dbf4 kinase remains active and acts as an effector of checkpoint under replication stress. However, the downstream targets of Cdc7-Dbf4 contributed to checkpoint regulation and replication stress-support function in cancer are not fully identified. In this work, we showed that aberrant Cdc7-Dbf4 induces DNA lesions that activate ATM/ATR-mediated checkpoint and homologous recombination (HR) DNA repair. Using a phosphoproteome approach, we identified HSP90-S164 as a target of Cdc7-Dbf4 in vitro and in vivo. The phosphorylation of HSP90-S164 by Cdc7-Dbf4 is required for the stability of HSP90-HCLK2-MRN complex and the function of ATM/ATR signaling cascade and HR DNA repair. In clinically, the phosphorylation of HSP90-S164 indeed is increased in oral cancer patients. Our results indicate that aberrant Cdc7-Dbf4 enhances replication stress tolerance by rewiring ATR/ATM mediated HR repair through HSP90-S164 phosphorylation and by promoting recovery from replication stress. We provide a new solution to a subtyping of cancer patients with dominant ATR/HSP90 expression by combining inhibitors of ATR-Chk1, HSP90, or Cdc7 in cancer combination therapy.