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Mitophagy is a selective form of macroautophagy in which dysfunctional and damaged mitochondria can be efficiently degraded, removed and recycled through autophagy. Selective removal of damaged or fragmented mitochondria is critical to the functional integrity of the entire mitochondrial network and cells. In past decades, numerous studies have shown that mitophagy is involved in various diseases; however, since the dual role of mitophagy in tumour development, mitophagy role in tumour is controversial, and further elucidation is needed. That is, although mitophagy has been demonstrated to contribute to carcinogenesis, cell migration, ferroptosis inhibition, cancer stemness maintenance, tumour immune escape, drug resistance, etc. during cancer progression, many research also shows that to promote cancer cell death, mitophagy can be induced physiologically or pharmacologically to maintain normal cellular metabolism and prevent cell stress responses and genome damage by diminishing mitochondrial damage, thus suppressing tumour development accompanying these changes. Signalling pathway-specific molecular mechanisms are currently of great biological significance in the identification of potential therapeutic targets. Here, we review recent progress of molecular pathways mediating mitophagy including both canonical pathways (Parkin/PINK1- and FUNDC1-mediated mitophagy) and noncanonical pathways (FKBP8-, Nrf2-, and DRP1-mediated mitophagy); and the regulation of these pathways, and abovementioned pro-cancer and pro-death roles of mitophagy. Finally, we summarise the role of mitophagy in cancer therapy. Mitophagy can potentially be acted as the target for cancer therapy by promotion or inhibition.

Nanomedicines (NMs) have played an increasing role in cancer therapy as carriers to efficiently deliver therapeutics into tumor cells. For this application, the uptake of NMs by tumor cells is usually a prerequisite to deliver the cargo to intracellular locations, which mainly relies on endocytosis. NMs can enter cells through a variety of endocytosis pathways. Different endocytosis pathways exhibit different intracellular trafficking routes and diverse subcellular localizations. Therefore, a comprehensive understanding of endocytosis mechanisms is necessary for increasing cellular entry efficiency and to trace the fate of NMs after internalization. This review focuses on endocytosis pathways of NMs in tumor cells, mainly including clathrin- and caveolae-mediated endocytosis pathways, involving effector molecules, expression difference of those molecules between normal and tumor cells, as well as the intracellular trafficking route of corresponding endocytosis vesicles. Then, the latest strategies for NMs to actively employ endocytosis are described, including improving tumor cellular uptake of NMs by receptor-mediated endocytosis, transporter-mediated endocytosis and enabling drug activity by changing intracellular routes. Finally, active targeting strategies towards intracellular organelles are also mentioned. This review will be helpful not only in explicating endocytosis and the trafficking process of NMs and elucidating anti-tumor mechanisms inside the cell but also in rendering new ideas for the design of highly efficacious and cancer-targeted NMs.

Biotransformation of the neo-clerodane diterpene, scutebarbatine F (1), by Streptomyces sp. CPCC 205437 was investigated for the first time, which led to the isolation of nine new metabolites, scutebarbatine F1–F9 (2–10). Their structures were determined by extensive high-resolution electrospray ionization mass spectrometry (HRESIMS) and NMR data analyses. The reactions that occurred included hydroxylation, acetylation, and deacetylation. Compounds 2–4 and 8–10 possess 18-OAc fragment, which were the first examples of 13-spiro neo-clerodanes with 18-OAc group. Compounds 7–10 were the first report of 13-spiro neo-clerodanes with 2-OH. Compounds 1–10 were biologically evaluated for the cytotoxic, antiviral, and antibacterial activities. Compounds 5, 7, and 9 exhibited cytotoxic activities against H460 cancer cell line with inhibitory ratios of 46.0, 42.2, and 51.1%, respectively, at 0.3 μM. Compound 5 displayed a significant anti-influenza A virus activity with inhibitory ratio of 54.8% at 20 μM, close to the positive control, ribavirin.

Background A35 is a novel synthetic cyclizing-berberine recently patented as an antitumor compound. Based on its dual targeting topoisomerase (top) activity, A35 might overcome the resistance of single-target top inhibitors and has no cardiac toxicity for not targeting top2β. In this study we further explored the biological effects and mechanisms of A35. Methods Antitumor activity of A35 was evaluated by SRB and colony formation assay. G2/M phase arrest (especially M) and first damage of M-phase cells were investigated by flow cytometry, cytogenetic analysis, immunofluorescence, co-immunoprecipitation and WB. The key role of phospho-YAP (Ser127) in decreasing YAP nuclear localization, subsequent G2/M arrest and proliferation inhibition were explored by YAP1−/− cells, mutated Ser127 YAP construct (Ser127A) and TUNEL. Results G2/M arrest induced by A35 was independent of p53. M phase cells at low dose were firstly damaged and most damaged-cells accumulated in M phase, and that was a result of preferring targeting top2α by A35, as top2α is essential to push M phase into next phase, and targeting top2α induced cells arrested at M phase. A35 decreased YAP1 nuclear localization by activating YAP phosphorylation (Ser127) which subsequently regulated the transcription of YAP target genes associated with growth and cycle regulation to induce G2/M arrest and growth inhibition. Conclusions Our studies suggested the mechanism of G2/M arrest induced by A35 and a novel role of YAP1 (Ser127) in G2/M arrest. As a dual topoisomerase inhibitor characterized by no cardiac toxicity, A35 is a promising topoisomerase anticancer agent and worthy of further development in future.

Cholestatic liver diseases are important causes of liver cirrhosis and liver transplantation, but few drugs are available for treatment. D-chiro-inositol (DCI), an isomer of inositol found in many Leguminosae plants and in animal viscera, is used clinically for the treatment of polycystic ovary syndrome (PCOS) and diabetes mellitus. In this study, we investigated whether DCI exerted an anti-cholestatic effect and its underlying mechanisms. A cholestatic rat model was established via bile duct ligation (BDL). After the surgery, the rats were given DCI (150 mg·kg-1·d-1) in drinking water for 2 weeks. Oral administration of DCI significantly decreased the serum levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST), and attenuated bile duct proliferation, parenchymal necrosis and fibrosis in BDL rats. Furthermore, DCI treatment significantly increased the serum and bile levels of total bile acid (TBA), and decreased TBA levels in the liver. Moreover, DCI treatment significantly increased expression of the genes encoding bile acid transporters BSEP (Abcb11) and MRP2 (Abcc2) in liver tissues. DCI treatment also markedly decreased hepatic CD68 and NF-kappaB (NF-κB) levels, significantly decreased the serum and hepatic MDA levels, markedly increased superoxide dismutase activity in both serum and liver tissues. Using whole-genome oligonucleotide microarray, we revealed that DCI treatment altered the expression profiles of oxidation reduction-related genes in liver tissues. Collectively, DCI effectively attenuates BDL-induced hepatic bile acid accumulation and decreases the severity of injury and fibrosis by improving bile acid secretion, repressing inflammation and decreasing oxidative stress. The results suggest that DCI might be beneficial for patients with cholestatic disorders.

c-Myc, a key activator of cell proliferation and angiogenesis, promotes the development and progression of breast cancer. Ezrin-radixin-moesin-binding phosphoprotein-50 (EBP50) is a multifunctional scaffold protein that suppresses the proliferation of breast cancer cells. In this study we investigated whether the cancer-suppressing effects of EBP50 resulted from its regulation of c-Myc signaling in human breast cancer MCF-7 cells in vitro and in vivo. We first found a significant correlation between EBP50 and c-Myc expression levels in breast cancer tissue, and demonstrated that EBP50 suppressed cell proliferation through decreasing the expression of c-Myc and its downstream proteins cyclin A, E and Cdc25A in MCF-7 cells. We further showed that EBP50 did not regulate c-Myc mRNA expression, but it promoted the degradation of c-Myc through the autophagic lysosomal pathway. Moreover, EBP50 promoted integration between c-Myc and p62, an autophagic cargo protein, triggering the autophagic lysosomal degradation of c-Myc. In EBP50-silenced MCF-7 cells, activation of autophagy by Beclin-1 promoted the degradation of c-Myc and inhibited cell proliferation. These results demonstrate that the EBP50/Beclin-1/p62/c-Myc signaling pathway plays a role in the proliferation in MCF-7 breast cancer cells: EBP50 stimulates the autophagic lysosomal degradation of c-Myc, thereby inhibits the proliferation of MCF-7 cells. Based on our results, promoting the lysosomal degradation of c-Myc might be a promising new strategy for treating breast cancer.

Human myofibrillogenesis regulator 1 (MR-1) is a functional gene also known as paroxysmal nonkinesigenic dyskinesia (PNKD). It is localised on human chromosome 2q35 and three different isomers, MR-1L, MR-1M and MR-1S, are formed by alternative splicing. MR-1S promotes cardiac hypertrophy and is closely related to cancer. MR-1S is overexpressed in haematologic and solid malignancies, such as hepatoma, breast cancer and chronic myelogenous leukaemia. MR-1S causes disordered cell differentiation, initiates malignant transformation and accelerates metastasis. MR-1S directly phosphorylates and activates the MEK-ERK-RSK pathway to accelerate cancer growth and facilitates metastasis by activating the MLC2-FAK-AKT pathway. Silencing MR-1 inhibits cancer cell proliferation and metastasis. MR-1S causes disordered cell differentiation, initiates malignant transformation and accelerates metastasis. MR-1 interacts with eukaryotic translation initiation factors and MRIP-1, which contains Ras GTPase, PH and zinc-containing ArfGap domains, as well as three ankyrin repeats. Mutations in the N-terminal region of MR-1L and MR-1S are the main causes of PNKD (a hereditary disease characterised by paroxysmal dystonic choreoathetosis) and targeting the mutated protein could provide symptomatic relief. These findings provide compelling evidence that MR-1 might be a diagnostic marker and therapeutic target for solid tumours, myelogenous leukaemia and PNKD.

SPHK1 (sphingosine kinase 1), a regulator of sphingolipid metabolites, plays a causal role in the development of hepatocellular carcinoma (HCC) through augmenting HCC invasion and metastasis. However, the mechanism by which SPHK1 signaling promotes invasion and metastasis in HCC remains to be clarified. Here, we reported that SPHK1 induced the epithelial-mesenchymal transition (EMT) by accelerating CDH1/E-cadherin lysosomal degradation and facilitating the invasion and metastasis of HepG2 cells. Initially, we found that SPHK1 promoted cell migration and invasion and induced the EMT process through decreasing the expression of CDH1, which is an epithelial marker. Furthermore, SPHK1 accelerated the lysosomal degradation of CDH1 to induce EMT, which depended on TRAF2 (TNF receptor associated factor 2)-mediated macroautophagy/autophagy activation. In addition, the inhibition of autophagy recovered CDH1 expression and reduced cell migration and invasion through delaying the degradation of CDH1 in SPHK1-overexpressing cells. Moreover, the overexpression of SPHK1 produced intracellular sphingosine-1-phosphate (S1P). In response to S1P stimulation, TRAF2 bound to BECN1/Beclin 1 and catalyzed the lysine 63-linked ubiquitination of BECN1 for triggering autophagy. The deletion of the RING domain of TRAF2 inhibited autophagy and the interaction of BECN1 and TRAF2. Our findings define a novel mechanism responsible for the regulation of the EMT via SPHK1-TRAF2-BECN1-CDH1 signal cascades in HCC cells. Our work indicates that the blockage of SPHK1 activity to attenuate autophagy may be a promising strategy for the prevention and treatment of HCC.

A series of new 1,13-cycloprotoberberine derivatives defined through variations at the 9-position were designed, synthesized and evaluated for their cytotoxicities in human HepG2 (hepatoma), HT1080 (fibrosarcoma) and HCT116 (colon cancer) cells. The preliminary structure−activity relationship (SAR) revealed that the replacement of 9-methoxyl with an ester moiety might significantly enhance the antiproliferative activity in vitro . Notably, compound 7f demonstrated equipotent cytotoxicity activity against breast cancer MCF-7 (parent) and doxorubicin (DOX)-resistant MCF-7 (MCF-7/ADrR) cells, indicating a mode of action different from that of DOX. Further mechanism study showed that 7f significantly inhibited activity of DNA topoisomerase I (Top I) and Top II. G2/M phase arrest and tumor cell growth reduction was observed thereafter. Thus, we consider cycloprotoberberine analogues to be a new family of promising antitumor agents with an advantage of inhibiting drug-resistant cancer cells.

Myofibrillogenesis regulator-1 (MR-1) is a gene overexpressed usually in many human cancers. However, the effects of MR-1 on cell proliferation, adhesion, migration and genome-wide gene regulation are still unclear. In this study, a human hepatoma cell line that highly overexpresses MR-1, BEL-7402/MR-1 cells was established. While the high expression of MR-1 did not promote cell proliferation, it significantly increased cell spreading, adhesion and migration compared with control cells. A total of 147 genes were regulated by MR-1 expression, 46 genes were down-regulated and 101 genes were up-regulated by MR-1 overexpression. Many of these genes were related to cell adhesion, cytoskeletal regulation, MAPK signaling, and cell cycle related pathways. Western blot analysis further confirmed the regulation of pathways associated with migration by MR-1. These results suggest that MR-1 is involved in the regulation of cancer cell adhesion, migration and related gene expression.

Wuli Zhao, Caixia Zhang, Chongwen Bi, Cheng Ye, Danqing Song, Xiujun Liu, Rongguang Shao Key Laboratory of Antibiotic Bioengineering, Ministry of Health, Laboratory of Oncology, Institute of Medicinal Biotechnology, Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing, People’s Republic of China Abstract: Sophoridine is a quinolizidine natural product of Sophora alopecuroides and has been applied for treatment of malignant trophoblastic tumors. Although characterized by low toxicity, the limited-spectrum antitumor activity hinders its further applications. 05D, a derivative of sophoridine, exhibits a better anticancer activity on diverse cancer cells, including solid tumors, and hematologic malignancy. It could inhibit topoisomerase 1 (top1) activity by stabilizing DNA–top1 complex and induce mitochondria-mediated apoptosis by promoting DNA single- and double-strand breakage mediated by top1. Also, 05D induced HCT116 cells arrest at G1 phase by inactivating CDK2/CDK4–Rb–E2F and cyclinD1–CDK4–p21 checkpoint signal pathways. 05D suppressed the ataxia telangiectasia mutated (ATM) and ATM and Rad3-related (ATR) activation and decreased 53BP level, which contributed to DNA damage repair, suggesting that the novel compound 05D might be helpful to improve the antitumor activity of DNA damaging agent by repressing ATM and ATR activation and 53BP level. In addition, the priorities in molecular traits and druggability, such as a simple structure and formulation for oral administration, further prove 05D to be a promising targeting topoisomerase agent. Keywords: topoisomerase inhibitor, topoisomerase 1, DNA breakage, sophoridinol, anticancer, apoptosis, cell cycle

Ras‐GTPase‐activating protein SH3 domain‐binding proteins (G3BP) are overexpressed in various human tumors and participate in several signaling pathways involved in growth, differentiation and apoptosis. G3BP interact with RasGAP (Ras‐GTPase activating protein) only in growing cells and depend on Ras activation, and participate in the Ras signal pathway. Therefore, the blockage and downregulation of G3BP may be a new strategy for cancer therapy. In this report, we demonstrate that a novel peptide GAP161 blocked the functions of G3BP and markedly suppressed HCT116 cell growth through the induction of apoptosis. The peptide bound with G3BP, which interfered with the interaction of G3BP1 with RasGAP and further suppressed Ras signaling pathways. GAP161 downregulated G3BP1 and G3BP2 proteins. Similarly, the knockdown of G3BP substantially decreased the proliferation of HCT116 cells and inhibited Ras signal pathways. Furthermore, the downregulation of G3BP could enhance cisplatin‐induced apoptosis and growth inhibition of HCT116 cells. We also found that GAP161 suppressed the growth of BALB/c mice bearing colon CT26 tumors and nude mice bearing HCT116 xenografts. These results suggest that downregulation of G3BP might be useful in cancer therapy and that GAP161 is a promising new therapeutic agent for cancers. (Cancer Sci, doi: 10.1111/j.1349‐7006.2012.02361.x, 2012)

DNA topoisomerases play a key role in tumor proliferation. Chemotherapeutics targeting topoisomerases have been widely used in clinical oncology, but resistance and side effects, particularly cardiotoxicity, usually limit their application. Clinical data show that a decrease in topoisomerase (top) levels is the primary factor responsible for resistance, but in cells there is compensatory effect between the levels of top1 and top2α. Here, we validated cyclizing-berberine A35, which is a dual top inhibitor and preferentially targets top2α. The impact on the top2α catalytic cycle indicated that A35 could intercalate into DNA but did not interfere with DNA-top binding and top2α ATPase activity. A35 could facilitate DNA-top2α cleavage complex formation by enhancing pre-strand and post-strand cleavage and inhibiting religation, suggesting this compound can be a topoisomerase poison and had a district mechanism from other topoisomerase inhibitors. TARDIS and comet assays showed that A35 could induce cell DNA breakage and DNA-top complexes but had no effect on the cardiac toxicity inducer top2β. Silencing top1 augmented DNA break and silencing top2α decreased DNA break. Further validation in H9c2 cardiac cells showed A35 did not disturb cell proliferation and mitochondrial membrane potency. Additionally, an assay with nude mice further demonstrated A35 did not damage the heart. Our work identifies A35 as a novel skeleton compound dually inhibits topoisomerases, and predominantly and specially targets top2α by interfering with all cleavage steps and its no cardiac toxicity was verified by cardiac cells and mice heart. A35 could be a novel and effective targeting topoisomerase agent.

The treatment of hepatocellular carcinoma (HCC) remains a challenge and the future of cancer therapy will incorporate rational combinations directed to molecular targets that cooperate to drive critical pro-survival signaling. Sphingosine kinase 1 (SphK1) has been shown to regulate various processes important for cancer progression. Given the up-regulated expression of SphK1 in response to the silence of N-ras and other interactions between Ras/ERK and SphK1, it was speculated that combined inhibition of Ras/ERK and SphK1 would create enhanced antitumor effects. Experimental results showed that dual blockage of N-ras/ERK and SphK1 resulted in enhanced growth inhibitions in human hepatoma cells. Similarly, MEK1/2 Inhibitor U0126 potentiated SKI II-induced apoptosis in hepatoma HepG2 cells, consistently with the further attenuation of Akt/ERK/NF-κB signaling pathway. It was also shown that the combination of SKI II and U0126 further attenuated the migration of hepatoma HepG2 cells via FAK/MLC-2 signaling pathway. Taken together, the dual inhibition of SphK1 and Ras/ERK pathway resulted in enhanced effects, which might be an effective therapeutic approach for the treatment of HCC.

Myofibrillogenesis regulator-1 (MR-1) has been characterized as a tumor promoter in many cancers. However, its mechanism of action has not been fully elucidated. Here, we report that MR-1 is overexpressed in human breast cancer cells and participates in tumor promotion in human breast cancer MCF7 cells by activating the ERK1/2 signaling pathway. MR-1 interacts with MEK1/2 and ERK1, and its N-terminal sequence plays a major role in promoting the MEK/ERK cascade. Furthermore, six phosphorylation sites of MR-1 were identified, and phosphorylation at S46 was shown to be critical for the activation of MEK/ERK. Therefore, our findings suggest that MR-1 functions as a tumor promoter in MCF7 cells by activating the MEK/ERK signaling.