Mechanism of hydrogen on cervical cancer suppression revealed by high-throughput RNA sequencing

Cervical cancer is considered one of the diseases with the highest mortality among women and with limited treatment options. Hydrogen (H(2)) inhalation has been reported to have a variety of tumor-suppressive effects, but the exact mechanism remains unclear. In the present study, HeLa cervical cancer cells and HaCaT keratinocytes treated with H(2), and a HeLa xenograft mouse model subjected to H(2) inhalation were established. TUNEL, Cell Counting Kit-8 and Ki67 staining assays were used to detect cell apoptosis and proliferation. Oxidative stress was determined according to the levels of reactive oxygen species, malondialdehyde and superoxide dismutase. Tumor growth was recorded every 3 days, and the excised tumors were stained with hematoxylin and eosin. High-throughput RNA sequencing and subsequent Gene Ontology (GO) enrichment analysis were performed in HeLa-treated and un-treated HeLa cells. The expression of hypoxia-inducible factor (HIF)-1α and NF-κB p65 was verified by western blotting, immunohistochemistry and reverse transcription-quantitative PCR. The results revealed an increased apoptosis rate, and reduced cell proliferation and oxidative stress in H(2)-treated HeLa cells but not in HaCaT cells. Similarly, decreased tumor growth and cell proliferation, and enhanced cell apoptosis were observed in H(2)-treated HeLa tumors. RNA sequencing and GO analysis suggest that downregulated HIF1A (HIF-1α mRNA) and RelA (NF-κB p65) levels, and reduced NF-κB signaling were associated with the antitumor effect of H(2). Finally, decreased HIF-1α and NF-κB p65 expression both at the transcriptional and translational levels were observed in H(2)-treated HeLa cells and in HeLa-derived tumors. In conclusion, the present study reveals a novel mechanism of H(2) against cervical cancer, which may serve as a potential therapeutic target in clinical practice.