Autophagy Arrest Research Articles

Amantadine against glioma via ROS-mediated apoptosis and autophagy arrest.

Glioma is a common primary nervous system malignant tumor with poor overall cure rate and low survival rate, yet successful treatment still remains a challenge. Here, we demonstrated that amantadine (AMT) exhibits the powerful anti-glioma effect by promoting apoptosis and autophagy in vivo and in vitro. Mechanistically, amantadine induces a large amount of reactive oxygen species (ROS) accumulation in glioma cells, and then triggers apoptosis by destroying mitochondria. In addition, amantadine induces the initiation of autophagy and inhibits the fusion of autophagosome and lysosome, consequently performing an anti-glioma role. Taken together, our findings suggest that amantadine could be a promising anti-glioma drug that inhibits glioma cells by inducing apoptosis and autophagy, which may provide a novel potential treatment option for patients.

Targeted degradation of NDUFS1 by agrimol B promotes mitochondrial ROS accumulation and cytotoxic autophagy arrest in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a global public health problem with increased morbidity and mortality. Agrimol B, a natural polyphenol, has been proved to be a potential anticancer drug. Our recent report showed a favorable anticancer effect of agrimol B in HCC, however, the mechanism of action remains unclear. Here, we found agrimol B inhibits the growth and proliferation of HCC cells in vitro as well as in an HCC patient-derived xenograft (PDX) model. Notably, agrimol B drives autophagy initiation and blocks autophagosome-lysosome fusion, resulting in autophagosome accumulation and autophagy arrest in HCC cells. Mechanistically, agrimol B downregulates the protein level of NADH:ubiquinone oxidoreductase core subunit S1 (NDUFS1) through caspase 3-mediated degradation, leading to mitochondrial reactive oxygen species (mROS) accumulation and autophagy arrest. NDUFS1 overexpression partially restores mROS overproduction, autophagosome accumulation, and growth inhibition induced by agrimol B, suggesting a cytotoxic role of agrimol B-induced autophagy arrest in HCC cells. Notably, agrimol B significantly enhances the sensitivity of HCC cells to sorafenib in vitro and in vivo. In conclusion, our study uncovers the anticancer mechanism of agrimol B in HCC involving the regulation of oxidative stress and autophagy, and suggests agrimol B as a potential therapeutic drug for HCC treatment.

Inhibition of STX17–SNAP29–VAMP8 complex formation by costunolide sensitizes ovarian cancer cells to cisplatin via the AMPK/mTOR signaling pathway

Ovarian cancer (OC) is the most common gynecological malignancy. Chemotherapy failure is a major challenge in OC treatment. Targeting autophagy is a promising strategy to enhance the cytotoxicity of chemotherapeutic agents. In this study, we found that costunolide (CTD) inhibits autophagic flux and exhibits high therapeutic efficacy for OC treatment in an in vitro model. Mechanistically, CTD inactivates AMPK/mTOR signaling to inhibit autophagy initiation at the early stage and blocks mTORC1-dependent autophagosome–lysosome fusion at the late stage during autophagy by disrupting SNARE complex (STX17–SNAP29–VAMP8) formation, resulting in lethal autophagy arrest in OC cells. Furthermore, CTD sensitizes OC cells to cisplatin (CDDP) by blocking CDDP-induced autophagy both in vitro and in vivo. Together, our data provide novel mechanistic insights into CTD-induced autophagy arrest and suggest a new autophagy inhibitor for effective treatment of OC.

Brain-Targeted HFn-Cu-REGO Nanoplatform for Site-Specific Delivery and Manipulation of Autophagy and Cuproptosis in Glioblastoma.

Durable glioblastoma multiforme (GBM) management requires long-term chemotherapy after surgery to eliminate remaining cancerous tissues. Among chemotherapeutics, temozolomide is considered as the first-line drug for GBM therapy, but the treatment outcome is not satisfactory. Notably, regorafenib, an oral multi-kinase inhibitor, has been reported to exert a markedly superior effect on GBM suppression compared with temozolomide. However, poor site-specific delivery and bioavailability significantly restrict the efficient permeability of regorafenib to brain lesions and compromise its treatment efficacy. Therefore, human H-ferritin (HFn), regorafenib, and Cu2+ are rationally designed as a brain-targeted nanoplatform (HFn-Cu-REGO NPs), fulfilling the task of site-specific delivery and manipulating autophagy and cuproptosis against GBM. Herein, HFn affords a preferential accumulation capacity to GBM due to transferrin receptor 1 (TfR1)-mediated active targeting and pH-responsive delivery behavior. Moreover, regorafenib can inhibit autophagosome-lysosome fusion, resulting in lethal autophagy arrest in GBM cells. Furthermore, Cu2+ not only facilitates the encapsulation of regorafenib to HFn through coordination interaction but also disturbs copper homeostasis for triggering cuproptosis, resulting in a synergistical effect with regorafenib-mediated lethal autophagy arrest against GBM. Therefore, this work may broaden the clinical application scope of Cu2+ and regorafenib in GBM treatment via modulating autophagy and cuproptosis.

Moxidectin induces autophagy arrest in colorectal cancer.

Colorectal cancer (CRC) is a cancer with a high morbidity and mortality worldwide. Hence, developing new therapeutic drugs for CRC is very important. Moxidectin (MOX) has shown good anti-glioblastoma effect both in vitro and in vivo. This study aimed to elucidate the anti-CRC effect of MOX and its potential mechanism by investigating the influence of MOX on the viability, apoptosis, necrosis and autophagy of colorectal cancer cells (HCT15 and SW620) and its underlying mechanisms. It was found that MOX can induce autophagy arrest, promote autophagy initiation, inhibit autophagic flux and cell proliferation, simultaneously PI3K-Akt-mTOR signaling pathway and microtubule acetylation. Furthermore, MOX suppressed the growth of xenograft tumors, which was consistent with the in vitro results.

P17.09.A Regorafenib and Re-irradiation: analysis of clinical outcomes and toxicities in patients with recurrent glioblastomas

Abstract Background Glioblastoma is the most common and aggressive primary brain tumor in adults.The aggressiveness and poor prognosis related to this disease join to the limited available treatment options. The current standard of care involves surgical resection followed by concomitant radiotherapy and chemotherapy. At recurrence, no standard treatment exists and there are no guidelines to facilitate decisions in the recurrent setting. Available options include re-operation, re-irradiation, systemic therapy, alone or in combination. In recent years, immunotherapy strategies have revolutionized the treatment of many cancers, increasing the hope for GBM therapy. Regorafenib (Stivarga) is an inhibitor of several kinases involved in the mechanisms that regulate neoangiogenesis processes, through the inhibition vascular endothelial growth factor (VEGF) receptors and the modifications of the tumor microenvironment; specifically, Regorafenib binds and stabilizes PSAT1 (phosphoserine aminotransferase 1). The dual regulatory mechanism underlying PSAT1-induced autophagy arrest accounts for the superior anti-GBM effect of Regorafenib compared with Temozolomide. Material and Methods 15 patients with documented disease progression after surgery followed by RT and TMZ were assigned to receive regorafenib (REG) 160 mg once daily for the first 3 weeks of each 4-week cycle. All patients received prior radiation therapy (RT) to a median dose of 60 Gy (range 40.05 -60). Median time to retreatment after prior RT was 16 months (range 14-33). Tumor volumes ranged from 81.7 cm3 to 422.4 cm3 (CTV) and from 112.7 cm3 to 422.4 cm3 (PTV).3 patients (20%) received concomitant reirradiation with a radiation dose of 37.5 Gy in 15 fractions of 2.5 Gy. Results the median follow-up was 9.5 months (range 5-22). The overall survival and the progression-free survival rates were 53,8 %, and 46,6 % respectively at 2 years. In 53% the symptoms were stable. Only one patient developed late toxicity: acute pancreatitis (Grade I) regressed on interruption of Regorafenib. No other neurological deficits occurred during follow-up. At last follow up 60% of patients were alive. Conclusion we report our experience with Regorafenib, administered in patients with rapid progression after the end of postoperative radio chemotherapy treatment. Regorafenib might be a new potential treatment option for recurrent glioblastoma: it was well tolerated also in cases of combined treatment with reirradiation and appeared effective. Other studies will be necessary to evaluate and confirm the role of Regorafenib in glioblastoma patients and the potential effectiveness of the combined therapeutic strategy: Regorafenib-reirradiation.

Autophagy guided interventions to modify the cardiac phenotype of Danon disease

Danon disease is a lethal X-linked genetic syndrome resulting from radical mutations in the LAMP2 gene. LAMP2 protein deficiency results in defective lysosomal function, autophagy arrest and a multisystem disorder primarily involving the heart, skeletal muscle and the central nervous system. Cardiomyopathy is the main cause of morbidity and mortality. To investigate the mechanisms of and develop therapies for cardiac Danon disease we engineered a mouse model carrying an exon 6 deletion human mutation in LAMP2, which recapitulates the human cardiac disease phenotype. Mice develop cardiac hypertrophy followed by left ventricular dilatation and systolic dysfunction, in association with progressive fibrosis, oxidative stress, accumulation of autophagosomes and activation of proteasome. Stimulation of autophagy in Danon mice (by exercise training, caloric restriction, and rapamycin) aggravate the disease phenotype, promoting dilated cardiomyopathy. Inhibiting autophagy (by high fat diet or hydroxychloroquine) is better tolerated by Danon mice compared to wild type but is not curative. Inhibiting proteasome by Velcade was found to be highly toxic to Danon mice, suggesting that proteasome is activated to compensate for defective autophagy. In conclusion, activation of autophagy should be avoided in Danon patients. Since Danon's is a lifelong disease, we suggest that lifestyle interventions to decrease cardiac stress may be useful to slow progression of Danon's cardiomyopathy. While Danon mice better tolerate high fat diet and sedentary lifestyle, the benefit regarding cardiomyopathy in humans needs to be balanced against other health consequences of such interventions.

Repurposing Oxiconazole against Colorectal Cancer via PRDX2-mediated Autophagy Arrest

Colorectal cancer (CRC) is one of the most common malignancies worldwide, yet successful treatment still remains a challenge. In this study, we found that oxiconazole (OXI), a broad-spectrum antifungal agent, exhibits certain anti-tumor effect against CRC. Autophagy arrest and subsequent apoptosis are characterized as pivotal events involving OXI-induced growth suppression of CRC cells. Mechanistically, OXI downregulates the protein levels of peroxiredoxin-2 (PRDX2), an antioxidant enzyme, for reactive oxygen species (ROS) detoxication, to initiate autophagy by inactivating the Akt/mTOR pathway and inhibiting RAB7A-mediated fusion of autophagosome and lysosome, which lead to extreme accumulation of autophagosomes and subsequent growth suppression of CRC cells. Consistently, interfering with autophagy or overexpressing PRDX2 significantly impedes OXI-induced growth suppression of CRC cells. Moreover, OXI plus oxaliplatin, a mainstay drug for CRC treatment, achieves an improved anti-tumor effect. Taken together, our findings bring novel mechanistic insights into OXI-induced autophagy arrest and the growth inhibitory effect on CRC cells, and suggest a promisingly therapeutic role of OXI for CRC treatment.

Imperatorin induces autophagy and G0/G1 phase arrest via PTEN-PI3K-AKT-mTOR/p21 signaling pathway in human osteosarcoma cells in vitro and in vivo

BackgroundOsteosarcoma is the third most common cancer in adolescence and the first common primary malignant tumor of bone. The long-term prognosis of osteosarcoma still remains unsatisfactory in the past decades. Therefore, development of novel therapeutic agents which are effective to osteosarcoma and are safe to normal tissue simultaneously is quite essential and urgent.MethodsFirstly, MTT assay, cell colony formation assay, cell migration and invasion assays were conducted to evaluate the inhibitory effects of imperatorin towards human osteosarcoma cells. RNA-sequence assay and bioinformatic analysis were then performed to filtrate and assume the potential imperatorin-induced cell death route and signaling pathway. Moreover, quantitative real-time PCR assay, western blot assay and rescue experiments were conducted to confirm the assumptions of bioinformatic analysis. Finally, a subcutaneous tumor-transplanted nude mouse model was established and applied to evaluate the internal effect of imperatorin on osteosarcoma by HE and immunohistochemistry staining.ResultsImperatorin triggered time-dependent and dose-dependent inhibition of tumor growth mainly by inducing autophagy promotion and G0/G1 phase arrest in vitro and in vivo. Besides, imperatorin treatment elevated the expression level of PTEN and p21, down-regulated the phosphorylation of AKT and mTOR. In contrast, the inhibition of PTEN using Bpv (HOpic), a potential and selective inhibitor of PTEN, concurrently rescued imperatorin-induced autophagy promotion, cell cycle arrest and inactivation of PTEN-PI3K-AKT-mTOR/p21 pathway.ConclusionsThis work firstly revealed that imperatorin induced autophagy and cell cycle arrest through PTEN-PI3K-AKT-mTOR/p21 signaling pathway by targeting and up-regulating PTEN in human osteosarcoma cells. Hence, imperatorin is a desirable candidate for clinical treatments of osteosarcoma.

Dihydromyricetin attenuates palmitic acid-induced oxidative stress by promoting autophagy via SIRT3-ATG4B signaling in hepatocytes

BackgroundOxidative stress in hepatocytes was important pathogenesis of nonalcoholic steatohepatitis (NASH). Autophagy was a cellular process that can remove damaged organelles under oxidative stress, and thus presented a potential therapeutic target against NASH. This work aimed to investigate whether autophagy was participated in the protective effects of dihydromyricetin (DHM) on palmitic acid (PA)-induced oxidative stress in hepatocytes and the underlying mechanism.MethodsHepG2 and HHL-5 cell lines were pretreated with DHM (20 μM) for 2 h, followed by PA (0.2 mM) treatment for 16 h. The oxidative stress was assessed by the quantification of intracellular reactive oxygen species (ROS), mitochondrial ROS (mtROS), mitochondrial membrane potential (MMP) and mitochondrial ultrastructural analyses. The protein expressions of SIRT3, LC3I/II, P62 and ATG4B, as well as the acetylation of AGT4B were determined by western blotting using HepG2 and HepG2/ATG4B± cells with heterozygous knockout of ATG4B.ResultsExposure to PA resulted in increased intracellular ROS and mtROS, decreased MMP and aggravated mitochondrial injury in HepG2 cells, which were notably attenuated by DHM treatment. DHM-induced inhibition of oxidative stress was associated with the induction of autophagy, characterized by upregulated ATG4B and LC3 II as well as downregulated P62 levels. Furthermore, the inhibitory effects of DHM on PA-induced autophagy arrest and oxidative stress were eliminated when pretreated with a SIRT3 inhibitor 3-TYP or conducted in HepG2/ATG4B± cells, suggesting that SIRT3 and ATG4B were involved in DHM-induced benefits. Moreover, DHM treatment increased the protein expression of SIRT3 and SIRT3-dependent deacetylation of ATG4B in HepG2 cells.ConclusionOur results demonstrated that DHM attenuated PA-induced oxidative stress in hepatocytes through induction of autophagy, which was mediated through the increased expression of SIRT3 and SIRT3-mediated ATG4B deacetylation following DHM treatment.

YAP activation attenuates toxicarioside G‑induced lethal autophagy arrest in SW480 colorectal cancer cells.

Toxicarioside G (TCG), a natural product isolated from Calotropis gigantea, has been found to exhibit potent anticancer effects. The present study aimed to investigate the effect of TCG on the SW480 colorectal cancer cell line and the role of autophagy and Yes1 associated transcriptional regulator (YAP) in the TCG-mediated inhibition of cell proliferation and viability. Cell proliferation was detected using MTT, BrdU, colony formation and LDH release assays, while apoptosis was analyzed using flow cytometry and western blot analyses. Immunofluorescence and western blot analysis was used to determine TCG-induced autophagy and YAP activation. Pharmacological inhibition and siRNA was used to investigate the role of autophagy and YAP in TCG-mediated cell growth inhibition. The results revealed that TCG inhibited SW480 cell proliferation and viability, independent of apoptosis, and also induced autophagy. It was further demonstrated that TCG blocks autophagic flux, resulting in autophagy arrest in the SW480 cell line. The inhibition of autophagy restored the TCG-mediated inhibition of cell proliferation and viability, suggesting that TCG may induce lethal autophagy arrest in the SW480 cell line. Furthermore, TCG induced YAP activation in the SW480 cell line. Inhibition of YAP activity enhanced the TCG-mediated inhibition of cell proliferation and viability, suggesting that YAP may play a protective role in the TCG-induced effects. In conclusion, the findings of the present study indicated that TCG may induce lethal autophagy arrest and activate YAP, which serves a protective role in the SW480 cell line. These results suggested that the combined targeting of TCG and YAP may represent a promising strategy for TCG-mediated anticancer therapy.

Repurposing antitussive benproperine phosphate against pancreatic cancer depends on autophagy arrest.

Pancreatic cancer (PC) is one of the most common human malignancies worldwide and remains a major clinical challenge. Here, we found that benproperine phosphate (BPP), a cough suppressant, showed a significant anticancer effect on PC both invitro and invivo via the induction of autophagy-mediated cell death. Mechanistic studies revealed that BPP triggered AMPK/mTOR-mediated autophagy initiation and disturbed Ras-related protein Rab-11A (RAB11A)-mediated autophagosome-lysosome fusion, resulting in excessive accumulation of autophagosomes. Inhibition of autophagy or overexpression of RAB11A partially reversed BPP-induced growth inhibition in PC cells, suggesting that BPP might induce lethal autophagy arrest in PC cells. In conclusion, our results identify BPP as a potent antitumor agent for PC via the induction of autophagy arrest, therefore providing a new potential therapeutic strategy for the treatment of PC.

Discovery of new fluorescent thiazole\u2013pyrazoline derivatives as autophagy inducers by inhibiting mTOR activity in A549 human lung cancer cells

A series of fluorescent thiazole–pyrazoline derivatives was synthesized and their structures were characterized by 1H NMR, 13C NMR, and HRMS. Biological evaluation demonstrated that these compounds could effectively inhibit the growth of human non-small cell lung cancer (NSCLC) A549 cells in a dose- and time-dependent manner in vitro and inhibit tumor growth in vivo. The structure–activity relationship (SAR) of the compounds was analyzed. Further mechanism research revealed they could induce autophagy and cell cycle arrest while had no influence on cell necrosis. Compound 5e inhibited the activity of mTOR via FKBP12, which could be reversed by 3BDO, an mTOR activator and autophagy inhibitor. Compound 5e inhibited growth, promoted autophagy of A549 cells in vivo. Moreover, compound 5e showed good selectivity with no influence on normal vascular endothelial cell growth and the normal chick embryo chorioallantoic membrane (CAM) capillary formation. Therefore, our research provides potential lead compounds for the development of new anticancer drugs against human lung cancer.

Involvement of sarco/endoplasmic reticulum calcium ATPase-mediated calcium flux in the protective effect of oleic acid against lipotoxicity in hepatocytes

Elevated free fatty acids, particularly saturated ones such as palmitic acid, may play an important role in the lipotoxic mechanism of nonalcoholic fatty liver disease (NAFLD). Saturated fatty acids induce autophagy dysfunction and endoplasmic reticulum (ER) stress leading to apoptosis in hepatocytes. However, unsaturated fatty acids, such as oleic acid, are nontoxic and can even prevent saturated fatty acid-induced toxicity in vitro. Although emerging evidence has suggested that ER calcium flux disruption in hepatocytes is involved in NAFLD pathogenesis, the roles of fatty acids in autophagy and ER calcium flux still remain unclear. We demonstrated that oleic acid ameliorated palmitic acid-induced autophagy arrest and ER stress in parallel with ER calcium depletion in hepatocytes. Moreover, we found that the effect of oleic acid against autophagy arrest was reversed by the pharmacological inhibition of sarcoplasmic reticulum Ca2+–ATPase (SERCA), which influxes calcium to ER. These data suggest that SERCA-mediated ER calcium flux is greatly involved in fatty acid-induced lipotoxicity in hepatocytes, and the prevention of ER calcium depletion may restore saturated fatty acid-induced autophagy arrest in hepatocytes.

Exocyst Subcomplex Functions in Autophagosome Biogenesis by Regulating Atg9 Trafficking

During autophagy, double-membrane vesicles called autophagosomes capture and degrade the intracellular cargo. The de novo formation of autophagosomes requires several vesicle transport and membrane fusion events which are not completely understood. We studied the involvement of exocyst, an octameric tethering complex, which has a primary function in tethering post-Golgi secretory vesicles to plasma membrane, in autophagy. Our findings indicate that not all subunits of exocyst are involved in selective and general autophagy. We show that in the absence of autophagy specific subunits, autophagy arrest is accompanied by accumulation of incomplete autophagosome-like structures. In these mutants, impaired Atg9 trafficking leads to decreased delivery of membrane to the site of autophagosome biogenesis thereby impeding the elongation and completion of the autophagosomes. The subunits of exocyst, which are dispensable for autophagic function, do not associate with the autophagy specific subcomplex of exocyst.

Regorafenib induces lethal autophagy arrest by stabilizing PSAT1 in glioblastoma

ABSTRACTGBM (glioblastoma multiforme) is the most common and aggressive brain tumor with no curative options available. Therefore, it is imperative to develop novel potent therapeutic drugs for GBM treatment. Here, we show that regorafenib, an oral multi-kinase inhibitor, exhibits superior therapeutic efficacy over temozolomide, the first-line chemotherapeutic agent for GBM treatment both in vitro and in vivo. Mechanistically, regorafenib directly stabilizes PSAT1 (phosphoserine aminotransferase 1), a critical enzyme for serine synthesis, to trigger PRKAA-dependent autophagy initiation and inhibit RAB11A-mediated autophagosome-lysosome fusion, resulting in lethal autophagy arrest in GBM cells. Maintenance of PSAT1 at a high level is essential for regorafenib-induced GBM suppression. Together, our data provide novel mechanistic insights of regorafenib-induced autophagy arrest and suggest a new paradigm for effective treatment of GBM.Abbreviations: 3-MA: 3-methyladenine; ACACA: acetyl coenzyme A carboxylase alpha; ACTB/β-actin: actin, beta; AMPK: adenosine monophosphate-activated protein kinase; ATG5: autophagy related 5; CTSD: cathepsin D; DN-: dominant-negative; GBM: glioblastoma multiforme; LAMP1: lysosomal-associated membrane protein 1; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; PIK3C3/VPS34: phosphatidylinositol 3-kinase catalytic subunit type 3; PRKAA/AMPKα: protein kinase AMP-activated catalytic subunit alpha; PSAT1: phosphoserine aminotransferase 1; SQSTM1/p62: sequestosome 1; TKIs: tyrosine kinase inhibitors.

Potentiating bacterial cancer therapy using hydroxychloroquine liposomes

Salmonella VNP20009 inhibits tumor growth in preclinical models but its efficacy in humans is limited, potentially because cells mount an autophagy response that destroys the therapeutic bacteria. To neutralize this protective response, we combined VNP20009 with long-circulating liposomes containing the autophagy arrest agent hydroxychloroquine. This combination was associated with significantly larger numbers of intracellular Salmonella, accumulated autophagic vacuoles and much greater cell death in vitro. The combination was also associated with greater tumor-targeting ability, slower tumor growth and longer survival than free hydroxychloroquine in a murine model of melanoma. Our results suggest that combining tumor-targeting Salmonella with autophagy arrest may be effective for treating highly aggressive melanoma.

Abstract 3083A: C6-ceramide nanoliposomes sensitize paclitaxel resistant ovarian cancer cells to chemotherapy treatment

Abstract Ovarian cancer is the fifth leading cause of cancer deaths among women, and the majority of women are diagnosed at advanced stages resulting in poorer outcomes and survival rates. One of the driving forces behind these outcomes is the development of chemoresistance, and subsequent proliferation and invasion of tumor cells. In a patient-derived xenograft model of ovarian cancer, we identified the sphingosine pathway as significantly enriched in tumors after treatment with conventional chemotherapy. In order to target the sphingosine pathway, we investigated the potential effects of combining paclitaxel with C6-ceramide nanoliposomes in paclitaxel-resistant ovarian cancer cell lines, HeyA8-MDR and SKOV3-TR. Ceramide has been shown to be a key player in several processes important for tumor suppression including apoptosis, autophagy, and cell cycle arrest. We administered paclitaxel and C6-ceramide to HeyA8-MDR and SKOV3-TR cell lines in vitro and measured cell viability and expression of apoptotic and autophagic proteins. Results showed that in both cell lines, C6-ceramide significantly decreases the IC50 dose of paclitaxel, compared to control ghost nanoliposome treated cells. The IC50 of paclitaxel decreased in HeyA8-MDR cells from 400nM to 150nM, and in SKOV3-TR cells from 1000nM to 450nM. Western blot analyses indicate that combination treatment increases expression of apoptotic (cleaved caspase-3) factors in HeyA8-MDR cells, and autophagic (LC3) factors in SKOV3-TR cells, over single agent treatment or control. Paclitaxel is known to increase expression of apoptotic factors while decreasing expression of autophagic factors. Ceramide may increase both apoptotic and autophagic factors. In an orthotopic mouse model with the HeyA8-MDR line, combination treatment of paclitaxel and C6-ceramide resulted in significantly decreased tumor burden (1.38g +/- 0.74), compared to control ghost (p = 0.022, 2.81g +/- 1.57), C6-ceramide alone (p = 0.078, 2.50g +/- 1.58), and paclitaxel alone (p = 0.005, 2.48g +/- 0.75) groups. The combination of C6-ceramide and paclitaxel may prove useful in elucidating and targeting underlying chemoresistance mechanisms in ovarian cancer. Citation Format: Danielle C. Llaneza, Tye G. Deering, Samantha G. Sherwood, John R. Cornelison, Mark Kester, Charles N. Landen. C6-ceramide nanoliposomes sensitize paclitaxel resistant ovarian cancer cells to chemotherapy treatment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3083A. doi:10.1158/1538-7445.AM2017-3083A

Cadmium disrupts autophagic flux by inhibiting cytosolic Ca2+-dependent autophagosome-lysosome fusion in primary rat proximal tubular cells.

Previous studies have shown that subcellular Ca2+ redistribution is involved in Cd-induced autophagy inhibition in primary rat proximal tubular (rPT) cells, but the mechanism remains unclear. In this study, the status of autophagic flux was monitored by the GFP and RFP tandemly tagged LC3 method. Pharmacological inhibition of cytosolic Ca2+ concentration ([Ca2+]c) with 2-APB or BAPTA-AM significantly alleviated Cd-elevated yellow puncta formation and restored Cd-inhibited red puncta formation, while thapsigargin (TG) had the opposite regulatory effect, demonstrating that Cd-induced [Ca2+]c elevation inhibited the autophagic flux in rPT cells. Resultantly, Cd-induced autophagosomes accumulation was obviously modulated by 2-APB, BAPTA-AM and TG, respectively. Meanwhile, blockage of autophagosome-lysosome fusion and decreased recruitment of Rab7 to autophagosomes by Cd exposure was noticeably restored by 2-APB or BAPTA-AM, but co-treatment with Cd and TG further impaired Cd-induced autophagy arrest. Moreover, Cd-induced oxidative stress intimately correlated with cytosolic Ca2+ mobilization, and N-acetylcysteine (NAC) markedly rescued Cd-blocked autophagosome-lysosome fusion and recruitment of Rab7 to autophagosomes in rPT cells, implying that Cd-induced autophagy inhibition was due to [Ca2+]c elevation-triggered oxidative stress. In summary, these results suggest that Cd-mediated autophagy inhibition in rPT cells is dependent on cytosolic Ca2+ overload. Elevation of [Ca2+]c inhibited the autophagosome-lysosome fusion to block the degradation of autophagosomes, which aggravated Cd-induced cytotoxicity in rPT cells.

Abstract 1328: Arenobufagin induces apoptosis, autophagy and cell cycle arrest in hepatocellular carcinoma cells

Abstract Backgrounds: Hepatocellular carcinoma (HCC) is a deadly form of cancer without effective chemotherapy so far. Thus, there is an urgent need for novel chemotherapeutic agents for the treatment of HCC. Toad venom is frequently used in the treatment of liver cancer in traditional Chinese medicine. However, the exact component and the precise underlying mechanisms against tumor cells remain unclear. In the present research, we sought to study the antitumor mechanism of arenobufagin, a major active ingredient isolated from toad venom, in HCC cells. Methods and Results: The in vitro and in vivo antitumor activity was measured by colonic formation and HepG2/ADM tumor xenograft, respectively. Arenobufagin-induced HepG2 and HepG2/ADM cell apoptosis was detected by Annexin V-FITC staining and transmission electron microscope. The mitochondrial membrane potential measured by JC-1 staining combined with the changes of expression of Caspase9, Caspase3, PARP, Bax and Bcl-2 in HepG2 and HepG2/ADM cells suggested arenobufagin induced apoptosis via the mitochondrial pathways. Increasing autophagosomes that identified by Cyto-ID® staining and transmission electron microscope were observed in HepG2/ADM cells after arenobufagin treatment. Autophagy-specific inhibitors (e.g. 3-methyladenine, chloroquine and bafilomycin A1), small interfering RNAs target Beclin1 and Atg5 enhance arenobufagin-induced apoptosis, indicated that arenobufagin-mediated autophagy may protects HepG2/ADM cells from undergoing apoptotic cell death. We also demonstrated that inhibition of PI3K/Akt/mTOR pathway promotes the development of both autophagy and apoptosis caused by arenobufagin treatment. In addition, arenobufagin arrested HCC cells in G2 phase was determined by flow cytometry and p-Histone H3 (Ser10) staining. Arenobufagin caused double-strand DNA breaks and triggered the DNA damage response was evaluated by comet assay andγH2AX staining, and these effects were partly via the ATM/ATR-Chk1/Chk2-Cdc25C signaling pathway. We used a synthetic biotinylated arenobufagin-conjugated chemical probe in live cells to show that arenobufagin accumulated mainly in the nucleus. The microscopic thermodynamic parameters measured using isothermal titration calorimetry (ITC) also demonstrated that arenobufagin directly bound to DNA in vitro. The spectral characteristics of DNA (e.g. UV-visible absorption spectrum, circular dichroism spectrum and fluorescence intensity of the ethidium bromide-DNA system) indicated that arenobufagin bound to DNA by intercalation. Molecular modeling suggested arenobufagin intercalated with DNA via hydrogen bonds between arenobufagin and GT base pairs. Conclusion: This study provides novel insights into arenobufagin-induced HCC cells apoptosis, autophagy and cell cycle arrest. It is valuable for the further investigation of the use of arenobufagin in clinical anticancer chemotherapy. Citation Format: Min-Feng Chen, Li-Juan Deng, Wen-Cai Ye, Dong-Mei Zhang. Arenobufagin induces apoptosis, autophagy and cell cycle arrest in hepatocellular carcinoma cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1328.