Inhibition of autophagy augments chemotherapy in human salivary adenoid cystic carcinoma

Autophagy and salivary gland cancer: A putative target for salivary gland tumors

Salivary gland carcinomas are a group of heterogeneous tumors of different histological subtypes, presenting relatively low incidence but the entire variable of types. Although novel treatment options for salivary gland carcinomas patients' outcomes have improved, the treatment of this type of cancer is still not standardized. In addition, a significant number of patients, with a lack of optimal treatment strategies, have reduced survival. In the last two decades, a plethora of evidence pointed to the importance of autophagy, an essential catabolic process of cytoplasmatic component digestion, in cancer. In vitro and in vivo studies highlight the importance of autophagy in salivary gland carcinomas development as a tumor suppressor or promoter mechanism. Despite the potential of autophagy in salivary gland carcinomas development, no therapies are currently available that specifically focus on autophagy modulation in salivary gland carcinomas. In this review, we summarize current knowledge and clinical trials in regard to the interplay between autophagy and the development of salivary gland carcinomas. Autophagy manipulation may be a putative therapeutic strategy for salivary gland carcinomas patients.

Autophagy-A Hidden but Important Actor on Oral Cancer Scene

The duration of denture use, oral hygiene, smoking and male sex were identified as risk factors for oral mucosal lesions. As it is well known, all the oral mucosal lesions associated with risk factors have an important degree of malignity. Chronic mechanical irritation can be another cause of oral cancer and it is produced by the constant action of a deleterious agent from the oral cavity. Autophagy represents a complex evolutionary conserved catabolic process in which cells self-digest intracellular organelles in order to regulate their normal turnover and remove the damaged ones with compromised function to further maintain homeostasis. Autophagy is modulated by mTOR kinase and indirectly by PI3K/AKT survival pathway. Due to its dual capacity to either induce cell death or promote cell survival, important evidence pointed that autophagy has a two-faced role in response to chemotherapy in cancer. In conclusion, understanding how to overcome cytoprotective autophagy and how to take advantage of autophagic cell death is critical in order to enhance the cancer cells sensitivity to particular therapeutic agents.

Autophagy modulating agents as chemosensitizers for cisplatin therapy in cancer

Although cisplatin is one of the most common antineoplastic drug, its successful utilisation in cancer treatment is limited by the drug resistance. Multiple attempts have been made to find potential cisplatin chemosensitisers which would overcome cancer cells resistance thus improving antineoplastic efficacy. Autophagy modulation has become an important area of interest regarding the aforementioned topic. Autophagy is a highly conservative cellular self-digestive process implicated in response to multiple environmental stressors. The high basal level of autophagy is a common phenomenon in cisplatin-resistant cancer cells which is thought to grant survival benefit. However current evidence supports the role of autophagy in either promoting or limiting carcinogenesis depending on the context. This encourages the search of substances modulating the process to alleviate cisplatin resistance. Such a strategy encompasses not only simple autophagy inhibition but also harnessing the process to induce autophagy-dependent cell death. In this paper, we briefly describe the mechanism of cisplatin resistance with a special emphasis on autophagy and we give an extensive literature review of potential substances with cisplatin chemosensitising properties related to autophagy modulation.

Current State of Knowledge on Salivary Gland Cancers

Salivary gland cancers (SGCs), categorized as head and neck cancers (HNCs), constitute about 6% of head and neck cancer diagnoses based on estimate by American Head and Neck Society. Salivary gland tumors originate from different glandular cell types and are thus morphologically diverse. These tumors arise from any of the three major and various minor salivary glands. The incidence of SGCs has slowly increased during the last four decades. The etiology of SGCs is mostly unknown; however, specific gene mutations are associated with certain types of salivary tumors. Treatment options include surgical resection, radiation therapy (RT), chemotherapy, and multimodality therapy. HNC patients treated with RT often develop xerostomia and salivary hypofunction due to damaged salivary glands. In this review, we discuss etiology of SGCs, present findings on the role of autophagy in salivary tumorigenesis, review adverse effects of radiation treatment, and examine remedies for restoration of salivary function.

LncRNA CPS1-IT1 suppresses EMT and metastasis of colorectal cancer by inhibiting hypoxia-induced autophagy through inactivation of HIF-1α

OBJECTIVE

Hypoxia is a common phenomenon in solid tumor microenvironment. Thereby, the aim of this study was to investigate the molecular mechanisms of tumor metastasis and epithelial-mesenchymal transition (EMT) regulated by lncRNA CPS1 intronic transcript 1 (CPS1-IT1) under hypoxia in CRC.

METHODS

Expression of lncRNA CPS1-IT1, hypoxia-inducible factor-1 alpha (HIF-1α) and autophagy related protein (LC3) were initially assessed in human CRC tissues and in a series of CRC cell lines. The relationship of CPS1-IT1, HIF-1α and autophagy were analyzed in CRC were performed through in vitro and in vivo functional assays.

RESULTS

Expression of CPS1-IT1 were significantly reduced, while HIF-1α and LC3-II were increased in CRC tissues and cell lines. Then, in vitro assays revealed that CPS1-IT1 suppresses EMT and autophagy by inhibiting the activation of HIF-1α in CRC. An in vivo animal model also demonstrated the tumor suppressor mechanism of CPS1- IT1.

CONCLUSION

In this study, we found that hypoxia induce autophagy, and inhibition of autophagy could suppress tumor metastasis and EMT in CRC. Additionally, lncRNA CPS1-IT might suppresses metastasis and EMT by inhibiting hypoxia-induced autophagy through inactivation of HIF-1α in CRC.

Autophagy and its implication in human oral diseases

Macroautophagy/autophagy is a conserved lysosomal degradation process essential for cell physiology and human health. By regulating apoptosis, inflammation, pathogen clearance, immune response and other cellular processes, autophagy acts as a modulator of pathogenesis and is a potential therapeutic target in diverse diseases. With regard to oral disease, autophagy can be problematic either when it is activated or impaired, because this process is involved in diverse functions, depending on the specific disease and its level of progression. In particular, activated autophagy functions as a cytoprotective mechanism under environmental stress conditions, which regulates tumor growth and mediates resistance to anticancer treatment in established tumors. During infections and inflammation, activated autophagy selectively delivers microbial antigens to the immune systems, and is therefore connected to the elimination of intracellular pathogens. Impaired autophagy contributes to oxidative stress, genomic instability, chronic tissue damage, inflammation and tumorigenesis, and is involved in aberrant bacterial clearance and immune priming. Hence, substantial progress in the study of autophagy provides new insights into the pathogenesis of oral diseases. This review outlines the mechanisms of autophagy, and highlights the emerging roles of this process in oral cancer, periapical lesions, periodontal diseases, and oral candidiasis.

Expression of Autophagy and Reactive Oxygen Species-Related Proteins in Lacrimal Gland Adenoid Cystic Carcinoma

PURPOSE

To investigate the difference of expression of autophagy and reactive oxygen species (ROS) related proteins in adenoid cystic carcinoma (ACC) of lacrimal gland in comparison with ACC of salivary gland.

MATERIALS AND METHODS

Formalin-fixed, paraffin-embedded tissue samples from patients pathologically diagnosed as lacrimal gland ACC (n=11) and salivary gland ACC (n=64) were used. Immunochemistry was used to measure expression of autophagy related proteins [beclin-1, light chain (LC) 3A, LC3B, p62, and BCL2/adenovirus E1B 19 kDa protein-interacting protein 3 (BNIP3)] and ROS related proteins [catalase, thioredoxinreductase, glutathione S-transferasepi (GSTpi), thioredoxin interacting protein, and manganese superoxide dismutase (MnSOD)]. The prognostic factors related to disease-free and overall survival (OS) in lacrimal gland ACC by log-rank tests, were determined.

RESULTS

GSTpi in stromal cells was more highly expressed in lacrimal gland ACC (p=0.006), however, MnSOD in epithelial cells was expressed more in salivary gland ACC (p=0.046). LC3B positivity and BNIP3 positivity in epithelial component were associated with shorter disease-free survival (both p=0.002), and LC3A positivity in stromal component was the factor related to shorter OS (p=0.005).

CONCLUSION

This is the first study to demonstrate the expression of autophagy and ROS related proteins in lacrimal gland ACC in comparison with the salivary gland ACC, which would provide a basis for further study of autophagy and ROS mechanism as novel therapeutic targets in lacrimal gland ACC.

Autophagy facilitates lung adenocarcinoma resistance to cisplatin treatment by activation of AMPK/mTOR signaling pathway

Resistance to cisplatin-based therapy is a major challenge in the control of lung cancer progression. However, the underlying mechanisms remain largely unclear. Autophagy is closely associated with resistance to lung cancer therapy, but the function of autophagy in cisplatin treatment is still controversial. Here, we investigated whether autophagy was involved in lung adenocarcinoma resistance to cisplatin and further elucidated the underlying molecular mechanisms. Cisplatin-refractory lung adenocarcinoma cells increased autophagic vacuole formation detected by monodansylcadaverine staining. When exposed to cisplatin, lung adeno-carcinoma cells demonstrated increased levels of autophagy detected by MAP1A/1B LC3B and mammalian homologue of yeast Atg6 (Beclin-1) expression using Western blot analysis. Activation of cisplatin-induced autophagic flux was increased by using chloroquine (CQ), which can accumulate LC3B-II protein and increase punctate distribution of LC3B localization. The combination of cisplatin with CQ was more potent than cisplatin alone in inhibiting lung adenocarcinoma cell growth, which also increased cisplatin-induced apoptosis. Compared to cisplatin treatment alone, the combination of cisplatin and CQ decreased p-AMPK and increased p-mTOR protein expressions, in addition, the AMPK inhibitor Compound C plus cisplatin downregulated p-AMPK and upregulated p-mTOR as well as depressed LC3B cleavage. These findings demonstrate that activation of autophagy is a hallmark of cisplatin exposure in human lung adenocarcinoma cells, and that there is a cisplatin-induced autophagic response via activation of the AMPK/mTOR signaling pathway. We speculate that autophagy can be used as a novel therapeutic target to overcome cisplatin-resistant lung adenocarcinoma.

Hypoxia-induced autophagy contributes to the invasion of salivary adenoid cystic carcinoma through the HIF-1α/BNIP3 signaling pathway

Adenoid cystic carcinoma (ACC) is one of the most common types of salivary gland malignancy in the head and neck, and its aggressive ability to invade and metastasize is an important reason for its poor survival rates. Our previous investigations confirmed that autophagy-associated gene expression is closely associated with the occurrence and development of ACC. On this basis, the present study further investigated hypoxia-induced autophagy and its role in tumor invasion. Cobalt chloride (CoCl₂) was used to mimic hypoxia. The results of the present study indicated that autophagosome formation and upregulation of autophagy-associated microtubule-associated protein 1 light chain 3 and Beclin 1 were observed in ACC-M cells in response to CoCl₂. The hypoxia-inducible factor 1α/B cell lymphoma 2/adenovirus E1B 19K-interacting protein 3 signaling pathway was involved in hypoxia-induced autophagy in ACC. Furthermore, inhibition of autophagy by chloroquine markedly attenuated the tumor invasion induced by mimetic hypoxia in ACC. These results suggested that hypoxia-induced autophagy may serve as a potential target for the future treatment of ACC.

The Role of Autophagy in Salivary Gland Homeostasis and Stress Responses

Autophagy is a catabolic process that has been shown to have a role in many cellular processes including the removal of excessive or damaged proteins and protein aggregates. The salivary glands play a critical role in oral health, and their secretory capacity may be critically intertwined with the autophagic process. This review describes the role of autophagy activation in normal salivary gland homeostasis and during the glandular stress responses of therapeutic radiation, ductal ligation, autoimmunity, and salivary gland adenoid cystic carcinoma.