Autophagic action of new targeting agents in head and neck oncology

High nitric oxide-adapted head and neck cancer cell lines demonstrate altered autophagy and apoptosis

Background/purpose

Autophagy is an intracellular degradative process occurring under stressful conditions. Nitric oxide (NO), a free radical, regulates autophagy and apoptosis in several cancers. However, the effect of head and neck squamous cell carcinoma (HNSCC) cell adaptation to high nitric oxide (HNO) on autophagy remains unknown. We investigated the autophagy and apoptotic changes in the HNO-adapted HNSCC cell lines.

Materials and methods

Isogenic primary HNSCC (HN18/HN30) and metastatic (HN17/HN31) cell lines were evaluated. The cells were induced with 1, 2, 3 and 4 mM DEA-NONOate, an NO donor, for 72 h and assessed for cell viability by MTT assay. "HNO-adapted cells" were defined when the cell viability in the treatment group was <10%. The surviving cells were re-treated with HNO to confirm their adaptation. HNO-adapted cells were quantified for apoptosis using flow cytometry. Autophagic structures (autophagosomes) and proteins (LC3A/B and LC3B-II) were investigated using transmission electron and confocal microscopy, respectively.

Results

HNO-adapted concentration for HN18, HN17, HN30 and HN31 cells was 3, 2, 4 and 4 mM, respectively. The HNO-adapted HN18 cells demonstrated a significantly increased apoptotic percentage, whereas no significant apoptotic change was detected in the HNO-adapted HN17, HN30 and HN31 cells compared with the parent cells. Autophagosomes were widely observed across the HNO-adapted cells. Moreover, LC3A/B and LC3B-II proteins were increased in all HNO-adapted cells.

Conclusion

Our results demonstrate that apoptosis and/or autophagy are increased during HNO adaptation in HNSCC cell lines.

The dual role of autophagy in HPV-positive head and neck squamous cell carcinoma: a systematic review

PURPOSE

Human papilloma virus (HPV)-positive head and neck squamous cell carcinoma (HNSCC) displays distinct epidemiological, clinical, and molecular characteristics compared to the negative counterpart. Alterations in autophagy play an important role in cancer, and emerging evidence indicates an interplay of autophagy in HNSCC carcinogenesis and tumor promotion. However, the influence of HPV infection on autophagy in HNSCC has received less attention and has not been previously reviewed. Therefore, we here aimed to systematically review the role of autophagy explicitly in HPV+ HNSCC.

METHODS

Studies accessible in PubMed, Embase, Scopus, and Web of Science investigating HNSCC, highlighting the molecular biological differences between HPV- and HPV+ HNSCC and its influences on autophagy in HNSCC were analyzed according to the PRISMA statement. A total of 10 articles were identified, included, and summarized.

RESULTS

The HPV16 E7 oncoprotein was reported to be involved in the degradation of AMBRA1 and STING, and to enhance chemotherapy-induced cell death via lethal mitophagy in HNSCC cells. Autophagy-associated gene signatures correlated with HPV-subtype and overall survival. Additionally, immunohistochemical (IHC) analyses indicate that high LC3B expression correlates with poor overall survival in oropharyngeal HNSCC patients.

CONCLUSION

HPV may dampen general bulk autophagic flux via degradation of AMBRA1 but may promote selective autophagic degradation of STING and mitochondria. Interpretations of correlations between autophagy-associated gene expressions or IHC analyses of autophagy-related (ATG) proteins in paraffin embedded tissue with clinicopathological features without biological validation need to be taken with caution.

The Hippo pathway noncanonically drives autophagy and cell survival in response to energy stress

The Hippo pathway is known for its crucial involvement in development, regeneration, organ size control, and cancer. While energy stress is known to activate the Hippo pathway and inhibit its effector YAP, the precise role of the Hippo pathway in energy stress response remains unclear. Here, we report a YAP-independent function of the Hippo pathway in facilitating autophagy and cell survival in response to energy stress, a process mediated by its upstream components MAP4K2 and STRIPAK. Mechanistically, energy stress disrupts the MAP4K2-STRIPAK association, leading to the activation of MAP4K2. Subsequently, MAP4K2 phosphorylates ATG8-family member LC3, thereby facilitating autophagic flux. MAP4K2 is highly expressed in head and neck cancer, and its mediated autophagy is required for head and neck tumor growth in mice. Altogether, our study unveils a noncanonical role of the Hippo pathway in energy stress response, shedding light on this key growth-related pathway in tissue homeostasis and cancer.

Targeted therapy for head and neck cancer: signaling pathways and clinical studies

Head and neck cancer (HNC) is malignant, genetically complex and difficult to treat and is the sixth most frequent cancer, with tobacco, alcohol and human papillomavirus being major risk factors. Based on epigenetic data, HNC is remarkably heterogeneous, and treatment remains challenging. There is a lack of significant improvement in survival and quality of life in patients with HNC. Over half of HNC patients experience locoregional recurrence or distal metastasis despite the current multiple traditional therapeutic strategies and immunotherapy. In addition, resistance to chemotherapy, radiotherapy and some targeted therapies is common. Therefore, it is urgent to explore more effective and tolerable targeted therapies to improve the clinical outcomes of HNC patients. Recent targeted therapy studies have focused on identifying promising biomarkers and developing more effective targeted therapies. A well understanding of the pathogenesis of HNC contributes to learning more about its inner association, which provides novel insight into the development of small molecule inhibitors. In this review, we summarized the vital signaling pathways and discussed the current potential therapeutic targets against critical molecules in HNC, as well as presenting preclinical animal models and ongoing or completed clinical studies about targeted therapy, which may contribute to a more favorable prognosis of HNC. Targeted therapy in combination with other therapies and its limitations were also discussed.

Autophagy awakens-the myriad roles of autophagy in head and neck cancer development and therapeutic response

Autophagy is an evolutionarily conserved cell survival mechanism that degrades damaged proteins and organelles to generate cellular energy during times of stress. Recycling of these cellular components occurs in a series of sequential steps with multiple regulatory points. Mechanistic dysfunction can lead to a variety of human diseases and cancers due to the complexity of autophagy and its ability to regulate vital cellular functions. The role that autophagy plays in both the development and treatment of cancer is highly complex, especially given the fact that most cancer therapies modulate autophagy. This review aims to discuss the balance of autophagy in the development, progression, and treatment of head and neck cancer, as well as highlighting the need for a deeper understanding of what is still unknown about autophagy.

Targeting Drug Chemo-Resistance in Cancer Using Natural Products

Cancer is one of the leading causes of death globally. The development of drug resistance is the main contributor to cancer-related mortality. Cancer cells exploit multiple mechanisms to reduce the therapeutic effects of anticancer drugs, thereby causing chemotherapy failure. Natural products are accessible, inexpensive, and less toxic sources of chemotherapeutic agents. Additionally, they have multiple mechanisms of action to inhibit various targets involved in the development of drug resistance. In this review, we have summarized the basic research and clinical applications of natural products as possible inhibitors for drug resistance in cancer. The molecular targets and the mechanisms of action of each natural product are also explained. Diverse drug resistance biomarkers were sensitive to natural products. P-glycoprotein and breast cancer resistance protein can be targeted by a large number of natural products. On the other hand, protein kinase C and topoisomerases were less sensitive to most of the studied natural products. The studies discussed in this review will provide a solid ground for scientists to explore the possible use of natural products in combination anticancer therapies to overcome drug resistance by targeting multiple drug resistance mechanisms.

NGAL is Downregulated in Oral Squamous Cell Carcinoma and Leads to Increased Survival, Proliferation, Migration and Chemoresistance

Oral cancer is a major public health burden worldwide. The lack of biomarkers for early diagnosis has increased the difficulty in managing this disease. Recent studies have reported that neutrophil gelatinase-associated lipocalin (NGAL), a secreted glycoprotein, is upregulated in various tumors. In our study, we found that NGAL was significantly downregulated in primary malignant and metastatic tissues of oral cancer in comparison to normal tissues. The downregulation of NGAL was strongly correlated with both degree of differentiation and stage (I–IV); it can also serve as a prognostic biomarker for oral cancer. Additionally, tobacco carcinogens were found to be involved in the downregulation of NGAL. Mechanistic studies revealed that knockdown of NGAL increased oral cancer cell proliferation, survival, and migration; it also induced resistance against cisplatin. Silencing of NGAL activated mammalian target of rapamycin (mTOR)signaling and reduced autophagy by the liver kinase B1 (LKB1)-activated protein kinase (AMPK)-p53-Redd1 signaling axis. Moreover, cyclin-D1, Bcl-2, and matrix metalloproteinase-9 (MMP-9) were upregulated, and caspase-9 was downregulated, suggesting that silencing of NGAL increases oral cancer cell proliferation, survival, and migration. Thus, from our study, it is evident that downregulation of NGAL activates the mTOR pathway and helps in the progression of oral cancer.

Nintedanib selectively inhibits the activation and tumour-promoting effects of fibroblasts from lung adenocarcinoma patients

BACKGROUND

Nintedanib is a clinically approved multikinase receptor inhibitor to treat non-small cell lung cancer with adenocarcinoma (ADC) histology in combination with docetaxel, based on the clinical benefits reported on ADC but not on squamous cell carcinoma (SCC), which are the two most common histologic lung cancer subtypes.

METHODS

We examined the potential role of tumour-associated fibroblasts (TAFs) in the differential effects of nintedanib in ADC and SCC. Because TAFs are largely quiescent and activated in histologic sections, we focused on the antifibrotic effects of nintedanib on TAFs stimulated with the potent fibroblast activator TGF-β1, which is upregulated in lung cancer.

RESULTS

Nintedanib dose-dependently inhibited the TGF-β1-induced expression of a panel of pro-fibrotic activation markers in both ADC-TAFs and control fibroblasts derived from uninvolved lung parenchyma, whereas such inhibition was very modest in SCC-TAFs. Remarkably, nintedanib abrogated the stimulation of growth and invasion in a panel of carcinoma cell lines induced by secreted factors from activated TAFs in ADC but not SCC, thereby supporting that TGF-β signalling and aberrant TAF-carcinoma cross-talk is regulated by different mechanisms in ADC and SCC.

CONCLUSIONS

These results reveal that nintedanib is an effective inhibitor of fibrosis and its associated tumour-promoting effects in ADC, and that the poor antifibrotic response of SCC-TAFs to nintedanib may contribute to the differential clinical benefit observed in both subtypes. Our findings also support that preclinical models based on carcinoma-TAF interactions may help defining the mechanisms of the poor antifibrotic response of SCC-TAFs to nintedanib and testing new combined therapies to further expand the therapeutic effects of this drug in solid tumours.

Monitoring Autophagy Immunohistochemically and Ultrastructurally during Human Head and Neck Carcinogenesis. Relationship with the DNA Damage Response Pathway

Autophagy is a catabolic process that preserves cellular homeostasis. Its exact role during carcinogenesis is not completely defined. Specifically in head and neck cancer, such information from clinical settings that comprise the whole spectrum of human carcinogenesis is very limited. Towards this direction, we examined the in situ status of the autophagy-related factors, Beclin-1, microtubule-associated protein 1 light chain 3, member B (LC3B) and sequestosome 1/p62 (p62) in clinical material covering all histopathological stages of human head and neck carcinogenesis. This material is unique as each panel of lesions is derived from the same patient and moreover we have previously assessed it for the DNA damage response (DDR) activation status. Since Beclin-1, LC3B and p62 reflect the nucleation, elongation and degradation stages of autophagy, respectively, their combined immunohistochemical (IHC) expression profiles could grossly mirror the autophagic flux. This experimental approach was further corroborated by ultrastructural analysis, applying transmission electron microscopy (TEM). The observed Beclin-1/LC3B/p62 IHC patterns, obtained from serial sections analysis, along with TEM findings are suggestive of a declined authophagic activity in preneoplastic lesions that was restored in full blown cancers. Correlating these findings with DDR status in the same pathological stages are indicative of: (i) an antitumor function of autophagy in support to that of DDR, possibly through energy deprivation in preneoplastic stages, thus preventing incipient cancer cells from evolving; and (ii) a tumor-supporting role in the cancerous stage.

Natural Compounds As Modulators of Non-apoptotic Cell Death in Cancer Cells

Cell death is an innate capability of cells to be removed from microenvironment, if and when they are damaged by multiple stresses. Cell death is often regulated by multiple molecular pathways and mechanism, including apoptosis, autophagy, and necroptosis. The molecular network underlying these processes is often intertwined and one pathway can dynamically shift to another one acquiring certain protein components, in particular upon treatment with various drugs. The strategy to treat human cancer ultimately relies on the ability of anticancer therapeutics to induce tumor-specific cell death, while leaving normal adjacent cells undamaged. However, tumor cells often develop the resistance to the drug-induced cell death, thus representing a great challenge for the anticancer approaches. Numerous compounds originated from the natural sources and biopharmaceutical industries are applied today in clinics showing advantageous results. However, some exhibit serious toxic side effects. Thus, novel effective therapeutic approaches in treating cancers are continued to be developed. Natural compounds with anticancer activity have gained a great interest among researchers and clinicians alike since they have shown more favorable safety and efficacy then the synthetic marketed drugs. Numerous studies in vitro and in vivo have found that several natural compounds display promising anticancer potentials. This review underlines certain information regarding the role of natural compounds from plants, microorganisms and sea life forms, which are able to induce non-apoptotic cell death in tumor cells, namely autophagy and necroptosis.

Novel Mechanisms for the Antifibrotic Action of Nintedanib

Idiopathic pulmonary fibrosis (IPF) is a disease with relentless course and limited therapeutic options. Nintedanib (BIBF-1120) is a multiple tyrosine kinase inhibitor recently approved by the U.S. Food and Drug Administration for the treatment of IPF. The precise antifibrotic mechanism(s) of action of nintedanib, however, is not known. Therefore, we studied the effects of nintedanib on fibroblasts isolated from the lungs of patients with IPF. Protein and gene expression of profibrotic markers were assessed by Western immunoblotting and real-time PCR. Autophagy markers and signaling events were monitored by biochemical assays, Western immunoblotting, microscopy, and immunofluorescence staining. Silencing of autophagy effector proteins was achieved with small interfering RNAs. Nintedanib down-regulated protein and mRNA expression of extracellular matrix (ECM) proteins, fibronectin, and collagen 1a1 while inhibiting transforming growth factor (TGF)-β1-induced myofibroblast differentiation. Nintedanib also induced beclin-1-dependent, ATG7-independent autophagy. Nintedanib's ECM-suppressive actions were not mediated by canonical autophagy. Nintedanib inhibited early events in TGF-β signaling, specifically tyrosine phosphorylation of the type II TGF-β receptor, activation of SMAD3, and p38 mitogen-activated protein kinase. Nintedanib down-regulates ECM production and induces noncanonical autophagy in IPF fibroblasts while inhibiting TGF-β signaling. These mechanisms appear to be uncoupled and function independently to mediate its putative antifibrotic effects.

Radiation oncology in vitro: trends to improve radiotherapy through molecular targets

Much has been investigated to improve the beneficial effects of radiotherapy especially in that case where radioresistant behavior is observed. Beyond simple identification of resistant phenotype the discovery and development of specific molecular targets have demonstrated therapeutic potential in cancer treatment including radiotherapy. Alterations on transduction signaling pathway related with MAPK cascade are the main axis in cancer cellular proliferation even as cell migration and invasiveness in irradiated tumor cell lines; then, for that reason, more studies are in course focusing on, among others, DNA damage enhancement, apoptosis stimulation, and growth factors receptor blockages, showing promising in vitro results highlighting molecular targets associated with ionizing radiation as a new radiotherapy strategy to improve clinical outcome. In this review we discuss some of the main molecular targets related with tumor cell proliferation and migration as well as their potential contributions to radiation oncology improvements.

C2-ceramide induces cell death and protective autophagy in head and neck squamous cell carcinoma cells

Ceramides are second messengers involved in several intracellular processes in cancer cells, amongst others. The aim of this study was to evaluate the anti-tumor efficacy of C2-ceramide (C2-Cer; N-acetyl-d-sphingosine) by investigating cell death and autophagy in head and neck squamous cell carcinoma (HNSCC) cells. C2-Cer showed concentration-dependent cytotoxicity in HN4 and HN30 cell lines. It simultaneously induced caspase-3-independent apoptosis and programmed necrosis. C2-Cer markedly increased the expression level of microtubule-associated protein 1 light chain 3B (LC3B) type II associated with protective autophagy. An autophagy inhibitor enhanced C2-Cer-mediated cytotoxicity, while a programmed-necrosis inhibitor produced the opposite effect. Furthermore, C2-Cer up-regulated the phosphorylation of extracellular signal-regulated kinase 1/2, but down-regulated its downstream substrate phospho-mammalian target of rapamycin (p-mTOR) during the autophagy process. These results suggested that C2-Cer exerts anti-tumor effects by inducing programmed apoptosis and necrosis in HNSCC, and these cytotoxic effects are enhanced by an autophagy inhibitor.

Grape seed extract and resveratrol prevent 4-nitroquinoline 1-oxide induced oral tumorigenesis in mice by modulating AMPK activation and associated biological responses

Preventive measures against oral carcinogenesis are urgently warranted to lower the high morbidity and mortality associated with this malignancy worldwide. Here, we investigated the chemopreventive efficacy of grape seed extract (GSE) and resveratrol (Res) in 4-nitroquinoline-1-oxide (4NQO)-induced tongue tumorigenesis in C57BL/6 mice. Following 8 weeks of 4NQO exposure (100 µg/ml in drinking water), mice were fed with either control AIN-76A diet or diet containing 0.2% GSE (w/w) or 0.25% Res (w/w) for 8 subsequent weeks, while continued on 4NQO. Upon termination of the study at 16 weeks, tongue tissues were histologically evaluated for hyperplasia, dysplasia, and papillary lesions, and then analyzed for molecular targets by immunohistochemistry. GSE and Res feeding for 8 weeks, moderately decreased the incidence, but significantly prevented the multiplicity and severity of 4NQO-induced preneoplastic and neoplastic lesions, without any apparent toxicity. In tongue tissues, both 4NQO + GSE and 4NQO + Res treatment correlated with a decreased proliferation (BrdU labeling index) but increased apoptotic death (TUNEL-positive cells) as compared to the 4NQO group. Furthermore, tongue tissues from both the 4NQO + GSE and 4NQO + Res groups showed an increase in activated metabolic regulator phospho-AMPK (Thr172) and decreased autophagy flux marker p62. Together, these findings suggest that GSE and Res could effectively prevent 4NQO-induced oral tumorigenesis through modulating AMPK activation, and thereby, inhibiting proliferation and inducing apoptosis and autophagy, as mechanisms of their efficacy.