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Although poly (ADP-ribose) polymerase (PARP) inhibitors, as anti-tumor drugs targeting the DNA damage response (DDR), have been used for the therapy of various tumors, few researches reported their effect on laryngeal squamous cell carcinoma (LSCC). Here, we first discovered that the PARP-1/2 inhibitor Niraparib could simultaneously induce cell growth inhibition and autophagy in LSCC TU212 and TU686 cells. Niraparib decelerated cell cycle of LSCC by arresting G1 phase and preventing the cells from entering S phase. DNA lesions were also observed upon Niraparib treatment as evidenced by the accumulation of γH2AX and abatement of pRB expression. In addition, autophagy generation was confirmed by the observation of autophagosomes, LC3-positive autophagy-like vacuoles, and obvious conversion of LC3-I to LC3-II. Moreover, blocking autophagy enhanced Niraparib-induced growth inhibition and DNA lesions. Further studies suggested that autophagy suppression could obstruct the activation of checkpoint kinase 1 (Chk1) through elevating proteasomal activity and then impair the capacity of homologous recombination (HR), thereby improving the anti-LSCC efficiency of Niraparib. Collectively, these findings suggested that simultaneous targeting of Niraparib and autophagy might be a promising therapeutic schedule for LSCC in clinic. [ABSTRACT FROM AUTHOR]

Laryngeal squamous cell carcinoma (LSCC), one of the most common malignancies in the head and neck, has poor prognosis and high mortality. The need of novel and effective treatment for LSCC is urgent. Asparaginase, an enzyme-depriving asparagine, has been employed for the treatment of various cancers. In this study, we reported for the first time that asparaginase could induce remarkable cytotoxicity and caspase-dependent apoptosis in human LSCC Tu212 and Tu686 cells. Meanwhile, autophagy was triggered by asparaginase in LSCC cells, which was confirmed by accumulation of autophagosomes and the conversion of light chain 3-I (LC3-I) to LC3-II. Importantly, inhibition of autophagy by chloroquine (CQ) significantly enhanced asparaginase-induced cytotoxicity, indicating that autophagy has a cytoprotective role in asparaginase-treated LSCC cells. Meanwhile, we found that mitochondrial-originated reactive oxygen species (ROS) participated in asparaginase-induced autophagy and cytotoxicity. N-acetyl-L-cysteine (NAC), a common antioxidant, was employed to scavenge ROS, and our results demonstrated that NAC could significantly block asparaginase-induced autophagy and attenuate asparaginase-induced cytotoxicity, indicating that intracellular ROS played a crucial role in asparagine deprivation therapy. Furthermore, western blot analysis showed that asparaginase-induced autophagy was mediated by inactivation of Akt/mTOR and activation of the Erk signaling pathway in Tu212 and Tu686 cells. Therefore, these results indicated the protective role of autophagy in asparaginase-treated LSCC cells and provided a new attractive therapeutic strategy for LSCC by asparaginase alone or in combination with autophagic inhibitors. [ABSTRACT FROM AUTHOR]

Laryngeal squamous cell carcinoma (LSCC), one of the most common malignant solid tumors in the world, has a high rate of mortality, recurrence, and metastasis. Recombinant human arginase (rhArg) recently has been developed in arginine deprivation therapy for a number of malignant tumors. In the present study, we observed that rhArg triggered significant cytotoxicity in human laryngeal squamous cell carcinoma Tu212 cells. Meanwhile, we observed that rhArg simultaneously activated autophagic flux in Tu212 cells, which was demonstrated by the accumulation of autophagosome and light chain 3 II (LC3-II). And, we explored the role of autophagy in cytotoxicity induced by rhArg in Tu212 cells. Autophagy inhibitors including chloroquine (CQ) and bafilomycin A1 (Baf A1) enhanced cytotoxicity induced by rhArg, implying the protective role of autophagy in rhArg-treated Tu212 cells. Moreover, Akt/mTOR signaling pathway was most possibly to participate in the rhArg-induced autophagy. Meanwhile, rhArg could upregulate the phosphorylation of ERK1/2 in a time-dependent manner. Therefore, all the results illuminated the cytoprotective role of autophagy in the treatment of rhArg in laryngeal squamous carcinoma Tu212 cells and provided a potential approach for LSCC therapy by rhArg combined with autophagy inhibitors. [ABSTRACT FROM AUTHOR]

Nedaplatin, a cisplatin analog, was developed to reduce the toxicity of cisplatin, whereas it can be cross-resistant with cisplatin in some circumstances. This study aimed to investigate the role of autophagy in nedaplatin induced cell death in cisplatin-resistant nasopharyngeal carcinoma cells. Here, we showed that HNE1/DDP and CNE2/DDP cells were resistant to nedaplatin-induced cell death with reduced apoptotic activity. Nedaplatin treatment resulted in autophagosome accumulation and increased expression of LC3-II, indicating the induction of autophagy by nedaplatin in HNE1/DDP and CNE2/DDP cells. Inhibition of autophagy by Bafilomycin A1 (Baf A1) and 3-Methyladenine (3-MA) remarkably enhanced the antitumor efficacy of nedaplatin in HNE1/DDP and CNE2/DDP cells, suggesting that the resistance to nedaplatin-induced cell death was caused by enhanced autophagy in nedaplatin-resistant NPC cells. Additionally, Baf A1 enhanced reactive oxygen species (ROS) generation and apoptosis induced by nedaplatin in HNE1/DDP cells. Mechanistically, nedaplatin treatment caused activation of ERK1/2 and suppression of Akt/mTOR signaling pathways. While inhibition of ERK1/2 by MEK1/2 inhibitor, U0126, could reduce the expression of LC3-II in nedaplatin-resistant NPC cells. Furthermore, suppression of ROS could inhibit nedaplatin-induced ERK activation in HNE1/DDP cells, indicating that ROS and ERK were involved in nedaplatin-induced autophagy. Together, these findings suggested that autophagy played a cytoprotective role in nedaplatin-induced cytotoxicity of HNE1/DDP and CNE2/DDP cells. Furthermore, our results highlighted a potential approach to restore the sensitivity of cisplatin-resistant nasopharyngeal cancer cells to nedaplatin in combination with autophagy inhibitors. [ABSTRACT FROM AUTHOR]