Original contributionInhibition of autophagy-potentiated chemosensitivity to cisplatin in laryngeal cancer Hep-2 cells☆
Introduction
Larynx squamous cell carcinoma constitutes almost 2% to 3% of all malignant tumors, representing the second most common malignant neoplasm of the respiratory tract [1]. Early laryngeal cancer can usually be managed successfully with either radiotherapy or surgery. Advanced-stage cancer often requires a combination of treatment modalities. Chemotherapy is an important option in curing or controlling various cancers, but laryngeal cancer is insensitive to cisplatin (CDDP)-based chemotherapy in a clinical setting. The underlying mechanism has not been illuminated. Evidence suggests that autophagy plays a role in CDDP-induced cell death or CDDP resistance. Kim et al [2] found that autophagy increases the cytotoxicity of irradiation in apoptosis-efficient cells, which suggests the ability of autophagy to overcome multidrug resistance in cancer cells. Notably, autophagy can serve either to promote cell/tumor survival at certain stages or to promote cell death at other stages [3]. Despite this complication, it has been suggested by Mishima et al [4] that the blocking of autophagy could be a new strategy in the treatment of chronic myelogenous leukemia.
Prior studies have led to conflicting views of the role of autophagy in cancer chemotherapy. It has been established that autophagy mediates cell death of acute lymphoblastic leukemia cells by dexamethasone [5], promotes growth inhibition of PC3 cells by phenethyl isothiocyanate [6], promotes cell death by histone deacetylase inhibitors in chondrosarcoma cell lines [7], and may constitute a key mechanism by which transforming growth factor β promotes the generation of antitumor responses [8]. On the other hand, autophagy represents a protective mechanism against apoptotic cell death under starvation as well as contributes to resistance against therapy-induced apoptosis in cancer cells. It has been shown that autophagy is activated as a protective mechanism against 5-fluorouracil–induced apoptosis ([9], autophagy blockade sensitizes prostate cancer cells toward sulforaphane [10], autophagy serves a protective role in imatinib-mediated cell killing [11], and autophagy inhibition augments the anticancer activity of the histone deacetylase inhibitor suberoylanilide hydroxamic acid [12].
Markers for autophagy induction include Beclin 1 and LC3 conversion. We detected a high level of Beclin 1 expression in intact laryngeal cancer Hep2 cells. Hence, we speculated that autophagy may play a role in CDDP resistance in laryngeal cancer. Then, we examined whether increased cellular autophagy contributes to CDDP resistance in laryngeal cancer Hep2 cells and whether autophagy alteration affects the molecular events associated with cell death. Autophagy inhibitor 3-methyladenine (3-MA) or small interfering RNA (siRNA) against the autophagic gene Beclin 1 was used to study the effect of autophagy on drug resistance.
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Cell culture and transfection
The human laryngeal cancer Hep-2 cell line was purchased from the Type Culture Collection of the Chinese Academy of Sciences (Shanghai, China). Hep-2 cells were cultured in Dulbecco modified Eagle medium containing 10% fetal bovine serum (Gibco [New York, NY, USA], catalog number: 16000-044), penicillin (10 U/mL; Sigma [Los Angeles, CA, USA], catalog number: P0781) and streptomycin (0.1 mg/mL; catalog number: P0781) and were kept in a humidified atmosphere of 5% CO2 at 37°C. Cells were seeded
Autophagy was induced in Hep-2 cells treated with CDDP
An increasing number of studies have shown that cancer cells undergo autophagy in response to various anticancer therapies. The autofluorescent substance MDC is a specific marker for autophagic vacuoles. Autophagic vacuoles distributed within the cytoplasm or perinuclear regions stained by MDC appear as distinct dotlike structures. As shown in Fig. 1, compared with the control cells, the CDDP-treated Hep-2 cells showed an increase in the number of MDC-labeled vesicles, suggesting an induction
Discussion
The acquisition of drug resistance by cancer cells is thought to account for the failure of many anticancer therapies. Autophagy was one of the drug mechanisms. Many frontline anticancer agents would be predicted to stimulate autophagy, including arsenic trioxide, 5-fluorouracil, histone deacetylase inhibitors, tamoxifen, imatinib, and ionizing radiation [11], [12], [14], [15], [16], [17].
Laryngeal cancer exhibits CDDP resistance in a clinical setting. In this study, we explored whether
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Combined treatment with acetazolamide and cisplatin enhances the chemosensitivity of human head and neck squamous cell carcinoma TU868 cells
2020, Archives of Oral BiologyCitation Excerpt :Studies have found that acetazolamide, as a treatment of human colon cancer in nude mice transplanted tumor, could significantly suppress tumor growth (Kong, Xiao-Hua, & Yong, 2010). It is reported that the commonly used doses of cisplatin are 0.25 μg/ml-20 μg/ml in anti-tumor experiments in vitro (Ju et al., 2015; Kang et al., 2012; Nör et al., 2014). In order to explore the influence of combination therapy and minimize the generation of side effects better, we chose a relatively low effective dose of cisplatin 1 μg/mL.
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2016, Oral OncologyCitation Excerpt :Other cancer site studies are few and far between. Work in laryngeal cancer cell lines suggests that inhibition of autophagy promotes cisplatin-induced cell death [62] and cell death in response to other novel agents such as recombinant human arginase [63]. These data thus support the potential for adjuvant autophagy inhibition in the treatment of laryngeal cancers.
Autophagic responses to hypoxia and anticancer therapy in head and neck cancer
2015, Pathology Research and PracticeCitation Excerpt :The mRNA expression of Beclin 1 in cancer tissues was approximately 8 (P < 0.0001) times lower as compared the normal tissue while no correlation was observed between a decreasing trend of serum Beclin-1 levels by SPR and ELISA and clinical parameters, suggesting that decreased expression of Beclin 1 from tissues as compared to serum may be a poor prognosis indicator. Recently, Kang et al. demonstrated that knockdown of Beclin 1 by small interfering RNA against Beclin 1 could inhibit autophagy and elevated larynx squamous carcinoma cell's chemosensitivity to chemotherapy [33]. Beside Beclin 1's vital role in the process of autophagy, PI3K/mTOR pathway is also of vital importance in the regulation of autophagy [22].
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Conflicts of interest: None of the authors have any financial or other interest with regard to the submitted manuscript that might be constructed as a conflict of interest.