Glioblastoma is the most common and aggressive primary brain tumor in adults. New drug design and development is still a major challenge for glioma treatment. Increasing evidence has shown that nitazoxanide, an antiprotozoal drug, has a novel antitumor role in various tumors and exhibits multiple molecular functions, especially autophagic regulation. However, whether nitazoxanide-associated autophagy has an antineoplastic effect in glioma remains unclear. Here, we aimed to explore the underlying molecular mechanism of nitazoxanide in glioblastoma. Our results showed that nitazoxanide suppressed cell growth and induced cell cycle arrest in glioblastoma by upregulating ING1 expression with a favorable toxicity profile. Nitazoxanide inhibited autophagy through blockage of late-stage lysosome acidification, resulting in decreased cleavage of ING1. A combination with chloroquine or Torin1 enhanced or impaired the chemotherapeutic effect of nitazoxanide in glioblastoma cells. Taken together, these findings indicate that nitazoxanide as an autophagy inhibitor induces cell cycle arrest in glioblastoma via upregulated ING1 due to increased transcription and decreased post-translational degradation by late-stage autophagic inhibition.

Thymoquinone (TQ) is a natural compound extracted from the black seeds of Nigella sativa Linn. belonging to the Ranunculaceae family. TQ exhibits anti-inflammatory and antineoplastic activities against various cancers. Many therapeutics in hepatocellular carcinoma (HCC) treatments, such as doxorubicin (DOX) and cisplatin (DDP), exhibit considerable side effects on patients. We investigated cytotoxic effects of TQ, alone or in combination with DDP and DOX to HCC cells. TQ exhibited selective killing to HCC HepG2 and SMMC-7721 cells, but relatively low toxicity to normal liver HL-7702 cells. Importantly, when used with DOX or DDP, TQ showed synergistic inhibition of HCC cells, but not HL-7702 cells. We also discovered that Hep3B cells with a p53 null status were more sensitive to TQ than HepG2 and SMMC-7721 cells harboring wild type p53. Consistently, shRNA-mediated p53 silencing in HepG2 cells dramatically enhanced TQ-induced apoptosis, measured by caspase 3 and PARP cleavage. Furthermore, TQ-stimulated increase of reactive oxygen species (ROS) in p53-depleted cells was more pronounced than that in cells with intact p53. In summary, we discovered that TQ synergistically improves the anti-cancer activity of DOX and DDP, and loss of p53 sensitizes HCC cells to TQ-induced apoptosis.