Autophagy and cancer

Autologous blood transfusion promotes autophagy and inhibits hepatocellular carcinoma progression through HIF-1α signalling pathway

To explore the molecular mechanism of autologous blood transfusion promoting autophagy of hepatocellular carcinoma (HCC) cells and inhibiting the HCC progression through HIF-1α signalling pathway. This is a research paper. Rat hepatocellular carcinoma model and HepG2 cell model were built. The rats with HCC were conducted a surgery, and their blood was collected for detection to detect the recurrence and metastasis of the rats. Western blot was used to analysed the expression of HIF-1α, TP53, MDM2, ATG5 and ATG14 protein. The apoptosis rate of HepG2 cells was detected by flow cytometry, and autophagosomes were observed by transmission electron microscopy. HIF-1α expression was measured by immunofluorescence assay. The expressions of HIF-1α, TP53, MDM2, ATG5 and ATG14 protein were highest in model + autoblood group compared with the model group. HIF-1α content of model group was higher, but content of TP53, MDM2, ATG5 and ATG14 in the model group is the second. The highest apoptosis rate was found in HepG2 + autoblood group. The number of autophagosomes in HepG2 + autoblood was obviously larger than that of HepG2 + autoblood + inhibitor. HIF-1α expression of immunofluorescence assay showed that high expression of HIF-1α was clearly observed in HepG2 and HepG2 + autoblood group from confocal observation. However, there was no HIF-1α protein expression in HepG2 + autoblood + inhibitor group. The migration rate in HepG2 group, HepG2 + autoblood group and HepG2 + autoblood + inhibitor group was 85.71 ± 7.38%, 14.36 ± 6.54% and 61.25 ± 5.39%, respectively. Autologous blood transfusion promotes autophagy of HCC cells through HIF-1α signalling pathway, which further inhibits HCC migration and erosion.

Pharmacological Activities of Ginkgolic Acids in Relation to Autophagy

Plant-derived natural compounds are widely used as alternative medicine in healthcare throughout the world. Ginkgolic acids, the phenolic compounds isolated from the leaves and seeds of Ginkgo biloba, are among the chemicals that have been explored the most. Ginkgolic acids exhibit cytotoxic activity against a vast number of human cancers in various preclinical models in vitro and in vivo. Additionally, the pharmacological activities of ginkgolic acids are also involved in antidiabetic, anti-bacteria, anti-virus, anti-fibrosis, and reno/neuroprotection. Autophagy as a highly conserved self-cleaning process that plays a crucial role in maintaining cellular and tissue homeostasis and has been proven to serve as a protective mechanism in the pathogenesis of many diseases, including neurodegenerative diseases, cancer, and infectious diseases. In this review, we surveyed the pharmacological activities of the major three forms of ginkgolic acids (C13:0, C15:1, and C17:1) that are linked to autophagic activity and the mechanisms to which these compounds may participate. A growing body of studies in last decade suggests that ginkgolic acids may represent promising chemical compounds in future drug development and an alternative remedy in humans.

Suppression of Ribose-5-Phosphate Isomerase a Induces ROS to Activate Autophagy, Apoptosis, and Cellular Senescence in Lung Cancer

Ribose-5-phosphate isomerase A (RPIA) regulates tumorigenesis in liver and colorectal cancer. However, the role of RPIA in lung cancer remains obscure. Here we report that the suppression of RPIA diminishes cellular proliferation and activates autophagy, apoptosis, and cellular senescence in lung cancer cells. First, we detected that RPIA protein was increased in the human lung cancer versus adjust normal tissue via tissue array. Next, the knockdown of RPIA in lung cancer cells displayed autophagic vacuoles, enhanced acridine orange staining, GFP-LC3 punctae, accumulated autophagosomes, and showed elevated levels of LC3-II and reduced levels of p62, together suggesting that the suppression of RPIA stimulates autophagy in lung cancer cells. In addition, decreased RPIA expression induced apoptosis by increasing levels of Bax, cleaved PARP and caspase-3 and apoptotic cells. Moreover, RPIA knockdown triggered cellular senescence and increased p53 and p21 levels in lung cancer cells. Importantly, RPIA knockdown elevated reactive oxygen species (ROS) levels. Treatment of ROS scavenger N-acetyl-L-cysteine (NAC) reverts the activation of autophagy, apoptosis and cellular senescence by RPIA knockdown in lung cancer cells. In conclusion, RPIA knockdown induces ROS levels to activate autophagy, apoptosis, and cellular senescence in lung cancer cells. Our study sheds new light on RPIA suppression in lung cancer therapy.

Inhibition of SIRT1/2 upregulates HSPA5 acetylation and induces pro-survival autophagy via ATF4-DDIT4-mTORC1 axis in human lung cancer cells

Sirtuins have emerged as a promising novel class of anti-cancer drug targets. Inhibition of SIRT1 and SIRT2 induces apoptosis in cancer cells and they play multifaceted roles in regulating autophagy. In the present study, we found that salermide, a SIRT1/2-specific inhibitor or small interfering RNAs (siRNAs) to block SIRT1/2 expression could induce autophagy in human NSCLC cells. Moreover, SIRT1/2 inhibition increased the expression levels of ATF4 and DDIT4 and downregulated p-RPS6KB1 and p-EIF4EBP1, two downstream molecules of mTORC1. Moreover, ATF4 or DDIT4 knockdown attenuated salermide-induced autophagy, suggesting that SIRT1/2 inhibition induced autophagy through the ATF4-DDIT4-mTORC1 axis. Mechanistically, SIRT1/2 inhibition led to HSPA5 acetylation and dissociation from EIF2AK3, leading to ER stress response and followed by upregulation of ATF4 and DDIT4, triggering autophagy. Silencing of the autophagic gene ATG5 in lung cancer cells resulted in increased apoptotic cell death induced by SIRT1/2 inhibition. Our data show that inhibition of SIRT1/2 induces pro-survival autophagy via acetylation of HSPA5 and subsequent activation of ATF4 and DDIT4 to inhibit the mTOR signaling pathway in NSCLC cells. These findings suggest that combinatorial treatment with SIRT1/2 inhibitors and pharmacological autophagy inhibitors is an effective therapeutic strategy for cancer therapy.

A mechanism for increased sensitivity of acute myeloid leukemia to mitotoxic drugs

Mitochondria play a central and multifunctional role in the progression of tumorigenesis. Although many recent studies have demonstrated correlations between mitochondrial function and genetic makeup or originating tissue, it remains unclear why some cancers are more susceptible to mitocans (anticancer drugs that target mitochondrial function to mediate part or all of their effect). Moreover, fundamental questions of efficacy and mechanism of action in various tumor types stubbornly remain. Here we demonstrate that cancer type is a significant predictor of tumor response to mitocan treatment, and that acute myeloid leukemias (AML) show an increased sensitivity to these drugs. We determined that AML cells display particular defects in mitochondrial metabolism that underlie their sensitivity to mitocan treatment. Furthermore, we demonstrated that combinatorial treatment with a mitocan (CCCP) and a glycolytic inhibitor (2-deoxyglucose) has substantial synergy in AML cells, including primary cells from patients with AML. Our results show that mitocans, either alone or in combination with a glycolytic inhibitor, display anti-leukemia effects in doses much lower than needed to induce toxicity against normal blood cells, indicating that mitochondria may be an effective and selective therapeutic target.

Differential effects of ginkgol C17:1 on cisplatin-induced cytotoxicity: Protecting human normal L02 hepatocytes versus sensitizing human hepatoma HepG2 cells

Liver cancer is a major healthcare problem and one of the leading causes of cancer-associated mortality in the world. To date, chemotherapy remains a common method for treating cancer and cisplatin is one of the most widely used chemotherapeutics. However, owing to drug resistance and side effects, it is imperative to identify a novel approach to improve the anticancer effect of cisplatin. Auxiliary chemotherapy drugs with minor toxicity to normal cells may represent a novel strategy for cancer therapy. Previous studies have indicated that ginkgol C17:1 exhibits anticancer effects in liver cancer cells in vitro and in vivo. The antitumor activity of ginkgol C17:1 has been reported in combination with cisplatin in human liver cancer cells. Owing to the route of systemic administration, liver cancer cells and normal hepatocytes were exposed to chemotherapeutics and auxiliary chemotherapy drugs. However, the effects of ginkgol C17:1 in normal hepatocytes remain unclear. In the present study, the biological effects of ginkgol C17:1 alone and as co-treatment with cisplatin were compared in human hepatoma cells and normal hepatocytes. Consistently, the results confirmed that in human hepatoma HepG2 cells, ginkgol C17:1 or cisplatin alone induced autophagy and apoptosis. The co-treatment increased cisplatin-induced apoptosis and inhibited cisplatin-induced autophagy. In comparison, the treatments in human normal L02 hepatocytes indicated that ginkgol C17:1 alone induced autophagy, whereas cisplatin alone induced apoptosis. The co-treatment inhibited cisplatin-induced apoptosis, but enhanced autophagy in L02 cells. Further investigation revealed that the AMP-activated protein kinase/serine/threonine protein kinase ULK1 and phosphoinositide 3-kinase/protein kinase B/mammalian target of rapamycin signaling pathways were involved in the underlying regulatory mechanisms. Taken together, the results of the present study provide the first evidence that ginkgol C17:1 protects normal hepatocytes against cisplatin-induced cytotoxicity while potentiating the anticancer effect of cisplatin chemotherapy. The differential effects on normal and cancer cells suggest that ginkgol C17:1 is a promising candidate for auxiliary chemotherapy.

Diet Modulation Restores Autophagic Flux in Damaged Skeletal Muscle Cells

OBJECTIVES

Autophagy is a physiological and highly regulated mechanism, crucial for cell homeostasis maintenance. Its impairment seems to be involved in the onset of several diseases, including muscular dystrophies, myopathies and sarcopenia. According to few papers, chemotherapeutic drug treatment is able to trigger side effects on skeletal muscle tissue and, among these, a defective autophagic activation, which leads to the persistence of abnormal organelles within cells and, finally, to myofiber degeneration. The aim of this work is to find a strategy, based on diet modulation, to prevent etoposide-induced damage, in a model of in vitro skeletal muscle cells.

METHODS

Glutamine supplementation and nutrient deprivation have been chosen as pre-treatments to counteract etoposide effect, a chemotherapeutic drug known to induce oxidative stress and cell death. Cell response has been evaluated by means of morpho-functional, cytofluorimetric and molecular analyses.

RESULTS

Etoposide treated cells, if compared to control, showed dysfunctional mitochondria presence, ER stress and lysosomal compartment damage, confirmed by molecular investigations.

CONCLUSIONS

Interestingly, both dietary approaches were able to rescue myofiber from etoposide-induced damage. Glutamine supplementation, in particular, seemed to be a good strategy to preserve cell ultrastructure and functionality, by preventing the autophagic impairment and partially restoring the normal lysosomal activity, thus maintaining skeletal muscle homeostasis.

Effects of ginkgol C17:1 on cisplatin-induced autophagy and apoptosis in HepG2 cells

Previous studies have demonstrated that ginkgol C17:1 significantly inhibits human liver cancer cells and enhances the anticancer activity of cisplatin in vivo and in vitro. However, the mechanism and biological function of ginkgol C17:1 on cells undergoing chemotherapy remain unclear. The aim of the present study was to determine the antitumor activity and mechanism of ginkgol C17:1 in combination with cisplatin in human hepatoblastoma HepG2 cells. The green fluorescent protein (GFP)-light chain 3 (LC3) adenovirus was transfected into HepG2 cells and autophagic flux was determined using fluorescence microscopy. Western blot analysis was also conducted to measure the expression of proteins associated with apoptosis, autophagy and their associated signaling pathways. Compared with the control group, autophagic flux and nucleus aberration rates were significantly increased (P<0.05), and the expression of proteins associated with autophagy and apoptosis were increased in the groups treated with cisplatin or ginkgol C17:1, respectively. However, following co-treatment with ginkgol C17:1 and cisplatin, the autophagic flux and the expression of autophagy proteins decreased; however, the nucleus aberration rate and apoptosis protein expression significantly increased (P<0.05) compared with the group treated with cisplatin alone. Additionally, the signaling pathways of autophagy and apoptosis were also activated following treatment with cisplatin, alone and in combination with ginkgol C17:1. Taken together, these results indicate that ginkgol C17:1 inhibits cisplatin-induced autophagy via AMP-activated protein kinase/ULK1signaling and increases cisplatin-induced apoptosis in HepG2 cells via the phosphoinositide 3-kinase/Akt/mechanistic target of rapamycin pathway.

Activation of a c-Jun N-terminal kinase-mediated autophagy pathway attenuates the anticancer activity of gemcitabine in human bladder cancer cells

The role of autophagy in the anticancer activity of gemcitabine (GEM) in bladder cancer is unclear. The aim of this study is to determine whether GEM activates autophagy, the role of autophagy in the anticancer activity of GEM, and the underlying mechanism by which GEM induces autophagy. Human bladder cancer cell lines T24 and BIU87 were treated with GEM in vitro. Cell viability was measured using the Cell Counting Kit-8 assay. Apoptosis was detected by annexin V assay and western blot. Autophagy was measured by western blot and transmission electron microscopy. c-Jun N-terminal kinase (JNK) activation was detected by western blot. Chemical inhibitors were used for intervention of JNK and autophagy. GEM killed bladder cancer cells, which was associated with apoptosis induction. Autophagy was effectively activated by GEM. Suppressing autophagy in GEM-treated cells significantly decreased cell viability, which was associated with increased apoptosis. GEM-induced JNK activation and suppressed B-cell lymphoma 2 expression. The JNK inhibitor SP600125 inhibited GEM-induced autophagy activation and increased GEM's cytotoxicity. GEM kills bladder cancer cells through apoptosis. Meanwhile, JNK-mediated autophagy was activated, which protects the cells against apoptosis. Therefore, inhibition of autophagy could be exploited to enhance the anticancer efficacy of GEM for treating bladder cancer.

Digestomics: an emerging strategy for comprehensive analysis of protein catabolism

When cells mobilize nutrients from protein, they generate a fingerprint of peptide fragments that reflects the net action of proteases and the identities of the affected proteins. Analyzing these mixtures falls into a grey area between proteomics and metabolomics that is poorly served by existing technology. Herein, we describe an emerging digestomics strategy that bridges this gap and allows mixtures of proteolytic fragments to be quantitatively mapped with an amino acid level of resolution. We describe recent successes using this technique, including a case where digestomics provided the link between hemoglobin digestion by the malaria parasite and the world-wide distribution of chloroquine resistance. We highlight other areas of microbiology and cancer research that are well-suited to this emerging technology.

Cross Talk of Proteostasis and Mitostasis in Cellular Homeodynamics, Ageing, and Disease

Mitochondria are highly dynamic organelles that provide essential metabolic functions and represent the major bioenergetic hub of eukaryotic cell. Therefore, maintenance of mitochondria activity is necessary for the proper cellular function and survival. To this end, several mechanisms that act at different levels and time points have been developed to ensure mitochondria quality control. An interconnected highly integrated system of mitochondrial and cytosolic chaperones and proteases along with the fission/fusion machinery represents the surveillance scaffold of mitostasis. Moreover, nonreversible mitochondrial damage targets the organelle to a specific autophagic removal, namely, mitophagy. Beyond the organelle dynamics, the constant interaction with the ubiquitin-proteasome-system (UPS) has become an emerging aspect of healthy mitochondria. Dysfunction of mitochondria and UPS increases with age and correlates with many age-related diseases including cancer and neurodegeneration. In this review, we discuss the functional cross talk of proteostasis and mitostasis in cellular homeodynamics and the impairment of mitochondrial quality control during ageing, cancer, and neurodegeneration.

Bypassing Mechanisms of Mitochondria-Mediated Cancer Stem Cells Resistance to Chemo- and Radiotherapy

Cancer stem cells (CSCs) are highly resistant to conventional chemo- and radiotherapeutic regimes. Therefore, the multiple drug resistance (MDR) of cancer is most likely due to the resistance of CSCs. Such resistance can be attributed to some bypassing pathways including detoxification mechanisms of reactive oxygen and nitrogen species (RO/NS) formation or enhanced autophagy. Unlike in normal cells, where RO/NS concentration is maintained at certain threshold required for signal transduction or immune response mechanisms, CSCs may develop alternative pathways to diminish RO/NS levels leading to cancer survival. In this minireview, we will focus on elaborated mechanisms developed by CSCs to attenuate high RO/NS levels. Gaining a better insight into the mechanisms of stem cell resistance to chemo- or radiotherapy may lead to new therapeutic targets thus serving for better anticancer strategies.

The Origin and Role of Autophagy in the Formation of Cytoplasmic Granules in Canine Lingual Granular Cell Tumors

Granular cell tumors (GCTs) are histologically characterized by polygonal neoplastic cells with abundant eosinophilic cytoplasmic granules. In humans, these cells are considered to be derived from Schwann cells, and the cytoplasmic granules are assumed to be autophagosomes or autophagolysosomes. However, the origin and nature of the cytoplasmic granules in canine GCTs have not been well characterized. The present study examined 9 canine lingual GCTs using immunohistochemistry, transmission electron microscopy (TEM), and cell culture and xenotransplantation experiments. In some cases, the tumor cells expressed S100, CD133, and desmin. The cytoplasmic granules were positive for LC3, p62, NBR1, and ubiquitin. TEM revealed autophagosome-like structures in the cytoplasm of the granule-containing cells. The cultured GCT cells were round to spindle shaped and expressed S100, nestin, Melan-A, CD133, LC3, p62, NBR1, and ubiquitin, suggesting that they were of neural crest origin, redifferentiated into melanocytes, and exhibited upregulated autophagy. The xenotransplanted tumors consisted of spindle to polygonal cells. Only a few cells contained cytoplasmic granules, and some had melanin pigments in their cytoplasm. The xenotransplanted cells expressed S100, nestin, Melan-A, and CD133. P62 and ubiquitin were detected, regardless of the presence or absence of cytoplasmic granules, while LC3 and NBR1 were detected only in the neoplastic cells containing cytoplasmic granules. These findings suggest that some xenotransplanted cells redifferentiated into melanocytes and that autophagy was upregulated in the cytoplasmic granule-containing cells. In conclusion, canine lingual GCTs originate from the neural crest and develop cytoplasmic granules via autophagy. In addition, the microenvironment of GCT cells affects their morphology.

Mitophagy mechanisms and role in human diseases

Mitophagy is a process of mitochondrial turnover through lysosomal mediated autophagy activities. This review will highlight recent studies that have identified mediators of mitophagy in response to starvation, loss of mitochondrial membrane potential or perturbation of mitochondrial integrity. Furthermore, we will review evidence of mitophagy dysfunction in various human diseases and discuss the potential for therapeutic interventions that target mitophagy processes.

Lithium improves survival of PC12 pheochromocytoma cells in high-density cultures and after exposure to toxic compounds

Autophagy is an evolutionary conserved mechanism that allows for the degradation of long-lived proteins and entire organelles which are driven to lysosomes for digestion. Different kinds of stressful conditions such as starvation are able to induce autophagy. Lithium and rapamycin are potent autophagy inducers with different molecular targets. Lithium stimulates autophagy by decreasing the intracellular myo-inositol-1,4,5-triphosphate levels, while rapamycin acts through the inhibition of the mammalian target of rapamycin (mTOR). The correlation between autophagy and cell death is still a matter of debate especially in transformed cells. In fact, the execution of autophagy can protect cells from death by promptly removing damaged organelles such as mitochondria. Nevertheless, an excessive use of the autophagic machinery can drive cells to death via a sort of self-cannibalism. Our data show that lithium (used within its therapeutic window) stimulates the overgrowth of the rat Pheochromocytoma cell line PC12. Besides, lithium and rapamycin protect PC12 cells from toxic compounds such as thapsigargin and trimethyltin. Taken together these data indicate that pharmacological activation of autophagy allows for the survival of Pheochromocytoma cells in stressful conditions such as high-density cultures and exposure to toxins.

Cathepsins mediate tumor metastasis

Cathepsins are highly expressed in various human cancers, associated with tumor metastasis. It is superfamily, concluding A, B, C, D, E, F, G, H, L, K, O, S, V, and W family members. As a group of lysosomal proteinases or endopeptidases, each member has a different function, playing different roles in distinct tumorigenic processes such as proliferation, angiogenesis, metastasis, and invasion. Cathepsins belong to a diverse number of enzyme subtypes, including cysteine proteases, serine proteases and aspartic proteases. The contribution of cathepsins to invasion in human cancers is well documented, although the precise mechanisms by which cathepsins exert their effects are still not clear. In the present review, the role of cathepsin family members in cancer is discussed.

Autophagy Modulation in Disease Therapy: Where Do We Stand?

Since it was first described more than 50 years ago autophagy has been examined in many contexts, from cell survival to pathogen sequestration and removal. In more recent years our understanding of autophagy has developed sufficiently to allow effective targeted therapeutics to be developed against various diseases. The field of autophagy research is expanding rapidly, demonstrated by increases in both numbers of investigators in the field and the breadth of topics being addressed. Some diseases, such as the many cancers, have come to the fore in autophagy therapeutics research as a better understanding of their underlying mechanisms has surfaced. Numerous treatments are being developed and explored, from creative applications of the classic autophagy modulators chloroquine and rapamycin, to repurposing drugs approved for other treatments, such as astemizole, which is currently in use as an antimalarial and chronic rhinitis treatment. The landscape of autophagy modulation in disease therapy is rapidly changing and this review hopes to provide a cross-section of the current state of the field.