Hirsutanol A, a novel sesquiterpene compound from fungus Chondrostereum sp., induces apoptosis and inhibits tumor growth through mitochondrial-independent ROS production: hirsutanol A inhibits tumor growth through ROS production.

BACKGROUND: Hirsutanol A is a novel sesquiterpene compound purified from fungus Chondrostereum sp. in Sarcophyton tortuosum. Our previous studies had demonstrated that hirsutanol A exhibited potent cytotoxic effect on many kinds of cancer cell lines. In the current study, the antitumor activity of hirsutanol A and its molecular mechanisms were investigated. METHODS: Hirsutanol A induced growth inhibition and apoptotic cell death of human colon cancer SW620 cells and human breast cancer MDA-MB-231cells were determined using MTT assay and flow cytometry assay, respectively. The effect of hirsutanol A on intrinsic ROS level and change in mitochondrial membrane potential (△ψm) of different cell lines were also measured by flow cytometry assay. The function of JNK was compromised by JNK siRNA or JNK inhibitor SP600125. The expression of cytochrome c, p-JNK, p-c-Jun after treatment with hirsutanol A were detected by Western blot analysis. Finally, the in vivo anti-tumor effect of hirsutanol A was examined in human cancer cell SW620 xenograft model. RESULTS: The results showed that hirsutanol A significantly induced apoptosis, mitochondrial-independent increase of Reactive Oxygen Species (ROS) level, change of mitochondrial membrane potential, release of cytochrome c in human cancer cells. Preventing increase of ROS level using the potent antioxidant N-acetyl-L-cysteine (NAC) markedly decreased hirsutanol A-induced apoptosis. In addition, JNK signaling pathway was activated by hirsutanol A through elevating ROS level. Blockade of JNK signaling pathway by JNK specific inhibitor SP600125 enhanced apoptosis and hirsutanol A-induced ROS accumulation. Also, hirsutanol A exhibited antitumor activity in human cancer cell SW620 xenograft model. CONCLUSION: These data suggested that hirsutanol A inhibited tumor growth through triggering ROS production and apoptosis.

Isolation and structural elucidation of chondrosterins F-H from the marine fungus Chondrostereum sp.

The marine fungus Chondrostereum sp. was collected from a soft coral of the species Sarcophyton tortuosum from the South China Sea. Three new compounds, chondrosterins F-H (1, 4 and 5), together with three known compounds, incarnal (2), arthrosporone (3), and (2E)-decene-4,6,8-triyn-1-ol (6), were isolated. Their structures were elucidated primarily based on NMR and MS data. Incarnal (2) exhibited potent cytotoxic activity against various cancer cell lines.

Small nucleolar RNAs (snoRNAs) as potential non-invasive biomarkers for early cancer detection.

Small nucleolar RNAs (snoRNAs) are non-coding RNA (ncRNA) molecules, which are associated with specific proteins to form small nucleolar ribonucleoparticles. However, the function of snoRNAs in cancer still remains elusive. Recently, several independent lines of evidence have indicated that these ncRNAs might have crucial roles in controlling tumorigenesis, and snoRNAs could be potential biomarkers for cancer.

Hirsutanol A induces apoptosis and autophagy via reactive oxygen species accumulation in breast cancer MCF-7 cells.

Hirsutanol A is a novel sesquiterpene compound purified from the marine fungus Chondrostereum sp in the coral Sarcophyton tortuosum. Our previous studies had demonstrated that hirsutanol A exerted potent cytotoxic effect in many kinds of cancer cell lines. Here, the anticancer molecular mechanisms of hirsutanol A were investigated in breast cancer MCF-7 cells. The results showed that hirsutanol A could inhibit cell proliferation, elevate reactive oxygen species (ROS) level, and induce apoptosis and autophagy. Co-treatment with the potent antioxidant agent N-acetyl-L-cysteine could effectively reverse the effect of enhanced ROS production, which in turn, reduces growth inhibition, apoptosis, and autophagy mediated by hirsutanol A. In addition, blocking autophagy by bafilomycin A1 or Atg7-siRNA could synergistically enhance the antiproliferative effect and apoptosis induced by hirsutanol A. These data suggested that hirsutanol A could induce apoptosis and autophagy via accumulation of ROS and co-treatment with an autophagy inhibitor could sensitize MCF-7 cells to hirsutanol A.

Salivary Fusobacterium nucleatum serves as a potential diagnostic biomarker for gastric cancer.

BACKGROUND: As one of the most common tumors, gastric cancer (GC) has a high mortality rate, since current examination approaches cannot achieve early diagnosis. Fusobacterium nucleatum (Fn) primarily colonized in the oral cavity, has been reported to be involved in the development of gastrointestinal tumor. Until now, little is known about the relationship between salivary Fn and GC. AIM: To determine whether salivary Fn could be a biomarker to diagnose GC and explore the influence of Fn on GC cells. METHODS: The abundance of Fn in saliva was quantified by droplet digital polymerase chain reaction in 120 GC patients, 31 atrophic gastritis (AG) patients, 35 non-AG (NAG) patients, 26 gastric polyp (GP) patients, and 20 normal controls (NC) from Qilu Hospital of Shandong University from January 2019 to December 2020. Receiver operating characteristic (ROC) curve analysis was performed to evaluate the diagnostic value of Fn as well as traditional serum tumor markers, including carcinoembryonic antigen (CEA), carbohydrate antigen (CA) 19-9, and CA72-4. Transwell assay and wound-healing assay were conducted to assess the influence of Fn infection on GC cells. The expression of epithelial-mesenchymal transition (EMT) markers was detected using western blot assay. RESULTS: We found that the level of salivary Fn in GC patients was significantly increased compared with those in AG, NAG, and GP patients and NC (P < 0.001). ROC curve analysis showed a favorable capability of Fn (73.33% sensitivity; 82.14% specificity; area under the curve: 0.813) in GC diagnosis, which was superior to that of CEA, CA19-9, CA72-4, ferritin, and sialic acid. The Fn level in saliva of GC patients was increased as the TNM stage increased. GC patients with lymph node metastasis had higher Fn levels than those without metastasis. Both transwell and wound-healing assays indicated that Fn infection promoted the migration and invasion of GC cells. Western blot analysis showed that Fn infection decreased the expression of E-cadherin and increased the expressions of N-cadherin, vimentin, and snail. CONCLUSION: Fn abundance in saliva could be used as a promising biomarker to diagnose GC, and Fn infection could promote GC metastasis by accelerating the EMT process.

Fusobacterium Nucleatum Is a Risk Factor for Metastatic Colorectal Cancer.

OBJECTIVE: Increasing evidence has indicated that there is a correlation between Fusobacterium nucleatum (F. nucleatum) abundance and poor prognosis of colorectal cancer (CRC). Furthermore, tumor metastasis plays a decisive role in the prognosis of CRC patients. Therefore, it was hypothesized that the abundance of F. nucleatum in CRC tissues affects the tumor metastasis. METHODS: In the present study, F. nucleatum DNA obtained from 141 resected CRC samples was quantified by qPCR to determine whether there were differences in F. nucleatum abundance between groups with and without CRC metastasis. RESULTS: The results revealed that F. nucleatum was more abundant in CRC patients with metastasis, and CRC tissues enriched with F. nucleatum had a higher risk of lymph node metastasis and distant metastasis. The receiver operating characteristic curve indicated that F. nucleatum in CRC tissues could be used as an indicator for CRC metastasis, to some extent. Furthermore, the in vitro experiments (electron microscopy, and migration and invasion trials) revealed that F. nucleatum was a highly invasive bacterial strain, and could significantly enhance the invasion and migration capacity of SW480 and SW620 cells. In addition, a meta-analysis comprehensively indicated a slight correlation between F. nucleatum abundance and advanced CRC stage (RR=1.17, 95% CI: 1.00-1.37, P=0.04, random effect). CONCLUSION: There is a correlation between F. nucleatum abundance and CRC metastasis, and F. nucleatum may serve as a metastasis biomarker for CRC patients.

CaMKII-mediated Beclin 1 phosphorylation regulates autophagy that promotes degradation of Id and neuroblastoma cell differentiation.

Autophagy is a degradative pathway that delivers cellular components to the lysosome for degradation. The role of autophagy in cell differentiation is poorly understood. Here we show that CaMKII can directly phosphorylate Beclin 1 at Ser90 to promote K63-linked ubiquitination of Beclin 1 and activation of autophagy. Meanwhile, CaMKII can also promote K63-linked ubiquitination of inhibitor of differentiation 1/2 (Id-1/2) by catalyzing phosphorylation of Id proteins and recruiting TRAF-6. Ubiquitinated Id-1/Id-2 can then bind to p62 and be transported to autolysosomes for degradation. Id degradation promotes the differentiation of neuroblastoma cells and reduces the proportion of stem-like cells. Our study proposes a mechanism by which autophagic degradation of Id proteins can regulate cell differentiation. This suggests that targeting of CaMKII and the regulation of autophagic degradation of Id may be an effective therapeutic strategy to induce cell differentiation in neuroblastoma.

Antitumor activity of 7RH, a discoidin domain receptor 1 inhibitor, alone or in combination with dasatinib exhibits antitumor effects in nasopharyngeal carcinoma cells.

Dysregulation of the discoidin domain receptors (DDRs) has been implicated in the development of numerous types of tumors, including head and neck cancer, and nasopharyngeal, breast, ovarian and esophageal carcinomas. Furthermore, agents that inhibit DDR1 activity are hypothesized to be useful for the treatment of nasopharyngeal carcinoma (NPC). The aim of the present study was to evaluate the effect of the DDR1 inhibitory (3-(2-(pyrazolo(1,5-a)pyrimidin-6-yl)-ethynyl)benzamide compound, 7RH, in NPC cells both in vitro and in vivo, and its effect when used in combination with dasatinib, a SRC family kinase (SFK) inhibitor. The effects of 7RH alone or in combination with dasatinib on cell viability were assessed using MTT assays and apoptosis was detected by flow cytometry. In addition, western blotting was performed to analyze the relative protein expression levels of cell cycle-associated genes in human NPC cell lines (CNE1, CNE2, HONE1 and SUNE1). Cell migration was also assessed using cell adhesion assays. Furthermore, tumor xenografts of CNE2 NPC cells were established in nude mice and the growth inhibitory effects of 7RH treatment alone or in combination with dasatinib were evaluated. Finally, knockdown of DDR1 protein expression was achieved by transfection of CNE2 cells with DDR1-specific small interfering RNA. Treatment with 7RH effectively suppressed the proliferation and induced the apoptosis of NPC cells. In addition, the Janus kinase 1 (JAK1)/signal transducer and activator of transcription (STAT3) signaling pathway was downregulated by 7RH, whereas the activities of the Ras/Raf/mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) and phosphoinositide 3-kinase (PI3K)/AKT signaling pathways were upregulated in response to 7RH treatment. Furthermore, the expression levels of phosphorylated SRC were increased in NPC cells treated with 7RH; thus indicating that SRC exhibits a vital function in the resistance of NPC cells to 7RH via activation of the PI3K/AKT signaling pathway. The results of the present study indicate that DDR1 and SFK inhibition may present a potential therapeutic strategy for patients with NPC.

EGFR tyrosine kinase inhibitors promote pro-caspase-8 dimerization that sensitizes cancer cells to DNA-damaging therapy.

The combination of time and order-dependent chemotherapeutic strategies has demonstrated enhanced efficacy in killing cancer cells while minimizing adverse effects. However, the precise mechanism remains elusive. Our results showed that pre-treatment of MCF-7 and MDA-MB-468 cells with epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor erlotinib or lapatinib significantly enhanced the cytotoxic effects of DNA-damaging agents compared to coadministration of the EGFR inhibitor and DNA-damaging agent. Sequential application of erlotinib and doxorubicin increased activated caspase-8 by promoting pro-caspase-8 homodimerization and autocatalytical cleavage, whereas coadministration did not. We found that EGFR inhibitors promoted pro-caspase-8 homodimerization by inhibiting ERK pathway signaling, while doxorubicin promoted it. Our data highlight that ERK has the potential to inhibit the formation of pro-caspase-8 homodimers by phosphorylating pro-caspase-8 at S387. In conclusion, the pretreatment of EGFR tyrosine kinase inhibitors promote pro-caspase-8 dimerization that sensitizes cancer cells to DNA-damaging agents. Our findings provide rationale for novel strategies for the implementation of combined targeted and cytotoxic chemotherapy within a new framework of time and order-dependent therapy.

ATM-mediated PTEN phosphorylation promotes PTEN nuclear translocation and autophagy in response to DNA-damaging agents in cancer cells.

PTEN (phosphatase and tensin homolog), a tumor suppressor frequently mutated in human cancer, has various cytoplasmic and nuclear functions. PTEN translocates to the nucleus from the cytoplasm in response to oxidative stress. However, the mechanism and function of the translocation are not completely understood. In this study, topotecan (TPT), a topoisomerase I inhibitor, and cisplatin (CDDP) were employed to induce DNA damage. The results indicate that TPT or CDDP activates ATM (ATM serine/threonine kinase), which phosphorylates PTEN at serine 113 and further regulates PTEN nuclear translocation in A549 and HeLa cells. After nuclear translocation, PTEN induces autophagy, in association with the activation of the p-JUN-SESN2/AMPK pathway, in response to TPT. These results identify PTEN phosphorylation by ATM as essential for PTEN nuclear translocation and the subsequent induction of autophagy in response to DNA damage.

Inhibition of DNA methyltransferase as a novel therapeutic strategy to overcome acquired resistance to dual PI3K/mTOR inhibitors.

Dual PI3K/mTOR(phosphatidylinositol 3-kinase/mammalian target of rapamycin) inhibitors are being evaluated clinically for the treatment of tumors with a hyperactivated PI3K/mTOR pathway. However, unexpected outcomes were obtained in clinical studies of cancer patients with an aberrant PI3K pathway. In clinical trials, applicable combination regimens are not yet available. In this study, using an integrated analysis of acquired BEZ235-resistant nasopharyngeal carcinoma cells, we demonstrate that DNA methyltransferase is a key modulator and a common node upstream of the AKT/mTOR and PDK1/MYC pathways, which are activated in cancer cells with acquired BEZ235 resistance. DNA methyltransferases were upregulated and induced PTEN and PPP2R2B gene hypermethylation, which downregulated their expression in BEZ235-resistant cancer cells. Reduced PTEN and PPP2R2B expression correlated with activated AKT/mTOR and PDK1/MYC pathways and conferred considerable BEZ235 resistance in nasopharyngeal carcinoma. Targeting methyltransferases in combination with BEZ235 sensitized BEZ235-resistant cells to BEZ235 in vitro and in vivo, suggesting the potential clinical application of this strategy to overcome BEZ235 resistance.

DC120, a novel AKT inhibitor, preferentially suppresses nasopharyngeal carcinoma cancer stem-like cells by downregulating Sox2.

Side population (SP) contains cancer stem-like cells (CSLCs). In this study, we characterized SP cells from nasopharyngeal carcinoma (NPC) cell lines and found that SP cells had a higher self-renewal ability in vitro and greater tumorigenicity in vivo. The AKT pathway was activated in NPC SP cells. DC120, a 2-pyrimidyl-5-amidothiazole inhibitor of the ATP binding site of AKT, inhibited phosphorylation of FKHRL1 and GSK-3ß. DC120 inhibited SP fraction, the sphere-forming ability in vitro and growth of primary xenografts as well as secondary xenografts' tumor recurrence. This inhibition was accompanied by reduced expression of stem-related gene Sox2 due to induction of p27 and miR-30a. A combination of DC120 and CDDP more effectively inhibited NPC cells compared with monotherapy in vitro and in vivo. Clinical evaluation of DC120 is warranted.

Acetylation of Beclin 1 inhibits autophagosome maturation and promotes tumour growth.

Beclin 1, a protein essential for autophagy, regulates autophagy by interacting with Vps34 and other cofactors to form the Beclin 1 complex. Modifications of Beclin 1 may lead to the induction, inhibition or fine-tuning of the autophagic response under a variety of conditions. Here we show that Beclin 1 is acetylated by p300 and deacetylated by SIRT1 at lysine residues 430 and 437. In addition, the phosphorylation of Beclin 1 at S409 by CK1 is required for the subsequent p300 binding and Beclin 1 acetylation. Beclin 1 acetylation inhibits autophagosome maturation and endocytic trafficking by promoting the recruitment of Rubicon. In tumour xenografts, the expression of 2KR mutant Beclin 1 (substitution of K430 and K437 to arginines) leads to enhanced autophagosome maturation and tumour growth suppression. Therefore, our study identifies an acetylation-dependent regulatory mechanism governing Beclin 1 function in autophagosome maturation and tumour growth.

Apogossypolone, a small-molecule inhibitor of Bcl-2, induces radiosensitization of nasopharyngeal carcinoma cells by stimulating autophagy.

Nasopharyngeal carcinoma (NPC) is a major cause of cancer deaths. Concurrent administration of radiation and chemotherapy is the treatment of choice for advanced NPC. Previously, we showed that apogossypolone (ApoG2) induced apoptosis by blocking the binding of Bcl-2 to Bax, arresting the cell cycle in the S phase, in turn inhibiting proliferation of NPC cells both in vitro and in vivo. In the present study, we showed that ApoG2 inhibited the proliferation of NPC cells in a dose-dependent manner. We treated CNE1, CNE2 and SUNE1 cells with ApoG2 for 72 h, and calculated the IC50 values as 2.84, 5.64 and 2.18 µM, respectively. Normal NP69 cell proliferation was not significantly inhibited. ApoG2 treatment induced significant autophagy, demonstrated by an increase in LC3-II protein expression, reduced protein p62 expression, and accumulation of punctuate GFP-LC3 in the cytoplasm of CNE1 or CNE2 cells. Sh-Atg5 attenuated the autophagy induced by ApoG2, indicating that Atg5 was required for ApoG2-induced autophagy. In addition, ApoG2 treatment blocked the binding of Bcl-2 to Beclin 1 protein, releasing pro-autophagic Beclin 1, which in turn triggered the autophagic cascade. Colony formation assays indicated that ApoG2 enhanced radiosensitization of CNE2 cells. In the ApoG2-plus-radiation combination group, more ring-shaped structures were evident in CNE1 and CNE2 cultures. LC3-II expression was enhanced and that of p62 reduced, compared to the ApoG2-only, radiation-only and control groups. ApoG2 enhanced the radiosensitivity of CNE2 xenografts in nude mice as measured by (C-T)/C ratios (as percentages); the values for the ApoG2 and radiation groups were 46.89% and 19.34%, respectively. The ApoG2-plus-radiation group exhibited greater antitumor activity (the inhibitory rate was 61.64%). Immunohistological staining showed that LC3-II expression became gradually upregulated in the ApoG2-plus-radiation group. Together, the results suggest that ApoG2 inhibits the binding of Bcl-2 to Beclin 1, inducing autophagy and radio-sensitizing NPC cells both in vitro and in vivo.

FRET-based ratiometric fluorescent probes for selective Fe3+ sensing and their applications in mitochondria.

Efficient ratiometric fluorescent Fe(3+) probes were designed and synthesized by linking a conjugated naphthalene chromophore to a rhodamine platform and a lipophilic triphenylphosphonium (TPP) cation. The probes could sensitively and selectively detect mitochondrial Fe(3+) in living cells.

Aggregation-induced emission of a novel conjugated phosphonium salt and its application in mitochondrial imaging.

A new conjugated phosphonium salt TPP was synthesized readily from phosphine-triggered ring-opening of 2,4,5-triphenylpyrylium salt. In aqueous solution, it exhibited interesting AIEE properties and self-assembled into fluorescent nanoparticles, which can be used as a fluorescence probe to image mitochondria in cells.

A diterpenoid compound, excisanin A, inhibits the invasive behavior of breast cancer cells by modulating the integrin ß1/FAK/PI3K/AKT/ß-catenin signaling.

AIM: Excisanin A, a diterpenoid compound purified from Isodon macrocalyxin D, has anti-cancer properties with little toxicity. In this study, the anti-invasive effects of excisanin A on breast cancer cells and its molecular mechanism of action were investigated. MAIN METHODS: MTT, wound healing, transwell chamber and cell adhesion assays were utilized to investigate the effects of excisanin A on MDA-MB-231 and SKBR3 cells. Western blotting, real-time PCR, RNA interference and luciferase reporter assays were employed to determine the molecular mechanism of action of excisanin A. KEY FINDINGS: Treating MDA-MB-231 and SKBR3 cells with 10-40µM excisanin A significantly inhibited cell migration and invasion and suppressed the mRNA and protein levels of matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9) in a dose-dependent manner. Excisanin A efficiently abolished integrin ß1 expression and reduced the phosphorylation of the downstream kinases focal adhesion kinase (FAK) and Src. Excisanin A inhibited the phosphorylation of phosphoinositide 3-kinase (PI3K), AKT and glycogen synthase kinase 3 beta (GSK3ß) and down-regulated ß-catenin expression and the luciferase activity of the transcription factor LEF-1. Moreover, treating breast cancer cells with siRNA targeting integrin ß1 inhibited cell invasion and migration. SIGNIFICANCE: These results demonstrated that excisanin A inhibited invasion by suppressing MMP-2 and MMP-9 expression; the integrin ß1/FAK/PI3K/AKT/ß-catenin signaling pathway was involved in this process. Therefore, excisanin A might be a potential anti-metastatic chemotherapeutic agent for the treatment of breast cancer.

Houttuyninum, an active constituent of Chinese herbal medicine, inhibits phosphorylation of HER2/neu receptor tyrosine kinase and the tumor growth of HER2/neu-overexpressing cancer cells.

AIMS: The overexpression of HER2/neu receptor plays a key role in tumorigenesis and tumor progression. Small molecules targeting HER2/neu have therapeutic value in cancers that overexpress HER2. In this present study, the effect of houttuyninum, a component in the Chinese herbal medicine Houttuynia cordata Thunb, on HER2/neu tyrosine phosphorylation and its in vivo antitumour activity was investigated. MAIN METHODS: The phosphorylation and expression of proteins were determined by Western blot analysis. The MTT assay was employed to examine the inhibition of cell proliferation in vitro. Xenografts were established in nude mice for evaluating the antitumour activity of houttuyninum in vivo. KEY FINDINGS: Houttuyninum inhibited phosphorylation of HER2 in a dose-dependent manner with an IC50 of 5.52 µg/ml without reducing HER2/neu protein expression in MDA-MB-453 cells. Houttuyninum also inhibited the activation of ERK1/2 and AKT, downstream molecules in the HER2/neu-mediated signal transduction pathway. In contrast, tyrosine phosphorylation of EGFR was unaffected when the concentration of houttuyninum was increased to 40 µg/ml in both A431 cells and MDA-MB-468 cells. Additionally, houttuyninum preferentially inhibited the growth of MDA-MB-453 cells that overexpressed HER2/neu; the MDA-MB-468 cells that overexpress EGFR remained unaffected. Administration of houttuyninum in vivo resulted in a significant reduction of phosphorylated HER2 levels and in tumor volumes of the BT474 and N87 xenografts, which both overexpress HER2/neu. SIGNIFICANCE: Our findings showed that houttuyninum can inhibit the HER2/neu signalling pathway and the tumor growth of cancer cells that overexpress HER2/neu. This drug may provide therapeutic value in the treatment of cancers that involve overexpression of HER2/neu.