Abstract Conclusion: Autophagy was involved in the radiation treatment of CNE-2 cells, and blocked autophagy enhances the radiosensitivity of nasopharyngeal carcinoma cell line CNE-2 in vitro. Objective: To determine whether autophagy induced by radiation therapy contributes to tumor cell death or represents a mechanism of resistance to therapy-mediated cell death. Methods: Autophagy in the CNE-2 nasopharyngeal carcinoma cells after radiation treatment was determined by quantitative GFP-LC3 analysis, electron microscopy, and autophagy-related molecules analysis by Western blotting. The contribution of autophagy to the cell viability was determined by MTT assay and clonogenic assay. Results: Autophagy was involved in CNE-2 cells post radiation treatment, and autophagy could ameliorate the cell viability post radiation. On the other hand, inhibition of autophagy could reduce cell viability and decrease the cell survival.
Breast cancer remains the leading cause of cancer mortality in females, and about 70% of the primary breast cancer patients are diagnosed ER?-positive, which is the most common type of breast cancer. MicroRNA-34a (miR-34a) has been shown to be a master regulator of tumor suppression in many types of cancers including breast cancer. However, the role of miR-34a in ER?-positive breast cancer has not been elucidated. Here, we find that in MCF-7, which is an ER?-positive breast cancer cell line, miR-34a is remarkably downregulated after E2 treatment. Overexpression of miR-34a by lentivirus suppresses cell proliferation, S phase ratio, and tumor formation in an E2-dependent manner in vitro. According to the mRNA sequence, lemur tyrosine kinase 3 (LMTK3), which is an important regulator of estrogen receptor alpha (ER?), is a predicted target of miR-34a. This is confirmed by dual luciferase reporter assay and the decrease of LMTK3 mRNA and protein levels after overexpression of miR-34a. Moreover, miR-34a overexpression decreases AKT signaling pathway and increases ER? phosphorylation status. Taken together, these results suggest that miR-34a inhibits breast cancer proliferation by targeting LMTK3 and might be used as an anti-ER? agent in breast cancer therapy.
Multidrug resistance (MDR) poses a serious impediment to the success of chemotherapy for laryngeal cancer. To identify microRNAs and mRNAs associated with MDR of human laryngeal cancer Hep-2 cells, we developed a multidrug-resistant human laryngeal cancer subline, designated Hep-2/v, by exposing Hep-2 cells to stepwise increasing concentrations of vincristine (0.02-0.96µM). Microarray assays were performed to compare the microRNA and mRNA expression profiles of Hep-2 and Hep-2/v cells. Compared to Hep-2 cells, Hep-2/v cells were more resistant to chemotherapy drugs (? 45-fold more resistant to vincristine, 5.1-fold more resistant to cisplatin, and 5.6-fold more resistant to 5-fluorouracil) and had a longer doubling time (42.33 ± 1.76 vs 28.75 ± 1.12h, P<0.05), higher percentage of cells in G0/G1 phase (80.98 ± 0.52 vs 69.14 ± 0.89, P<0.05), increased efflux of rhodamine 123 (95.97 ± 0.56 vs 12.40 ± 0.44%, P<0.01), and up-regulated MDR1 expression. A total of 7 microRNAs and 605 mRNAs were differentially expressed between the two cell types. Of the differentially expressed mRNAs identified, regulator of G-protein signaling 10, high-temperature requirement protein A1, and nuclear protein 1 were found to be the putative targets of the differentially expressed microRNAs identified. These findings may open a new avenue for clarifying the mechanisms responsible for MDR in laryngeal cancer.
The goals of this study were to investigate the effects of hypoxia on cochlear hair cell damage, and to explore the role of sirtuin1 in hypoxia-induced hair cell damage. Cochlear organotypic cultures from postnatal day 4 rats were used in this study. Hypoxia was induced by treating cochlear explants with CoCl2. Cochlear cultures were treated with CoCl2 alone or in combination with the sirtuin1 activator resveratrol and the sirtuin1 inhibitor sirtinol. Hair cell damage was identified by phalloidin staining and imaged using scanning electron microscopy. RT-PCR and Western blot analyses were used to detect the expression of sirtuin1 and acetylated nuclear factor-?B (NF-?B). Low concentrations of CoCl2 (100-200 ?M) did not cause an obvious change in the number and morphology of hair cells, whereas higher concentrations of CoCl2 (300-400 ?M) induced swelling of hair cells, accompanied by cell loss. Increased sirtuin1 expression was induced by CoCl2 at 100 to 200 ?M, but not at 400 ?M. NF-?B acetylation was significantly increased in explants treated with 400 ?M CoCl2. Pretreatment with resveratrol prevented CoCl2-induced hair cell loss and acetylation of NF-?B. The protective effect of resveratrol was significantly reduced by sirtinol. CoCl2 induces hair cell damage in organotypic cochleae cultures. Resveratrol attenuates CoCl2-induced cochlear hair cell damage possibly via activation of sirtuin1, which deacetylates NF-?B.
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