Molecular Hydrogen Inhibits Colorectal Cancer Growth via the AKT/SCD1 Signaling Pathway

Objective. Molecular hydrogen (H-2) has been considered a potential therapeutic target in many cancers. Therefore, we sought to assess the potential effect of H-2 on colorectal cancer (CRC) in this study. Methods. The effect of H-2 on the proliferation and apoptosis of RKO, SW480, and HCT116 CRC cell lines was assayed by CCK-8, colony formation, and flow cytometry assays. The effect of H-2 on tumor growth was observed in xenograft implantation models (inhalation of 67% hydrogen two hours per day). Western blot and immunohistochemistry analyses were performed to examine the expression of p-PI3K, PI3K, AKT, pAKT, and SCD1 in CRC cell lines and xenograft mouse models. The expression of SCD1 in 491 formalin-fixed, paraffin-embedded CRC specimens was investigated with immunochemistry. The relationship between SCD1 status and clinicopathological characteristics and outcomes was determined. Results. Hydrogen treatment suppressed the proliferation of CRC cell lines independent of apoptosis, and the cell lines showed different responses to different doses of H-2. Hydrogen also elicited a potent antitumor effect to reduce CRC tumor volume and weight in vivo. Western blot and IHC staining demonstrated that H-2 inhibits CRC cell proliferation by decreasing pAKT/SCD1 levels, and the inhibition of cell proliferation induced by H-2 was reversed by the AKT activator SC79. IHC showed that SCD1 expression was significantly higher in CRC tissues than in normal epithelial tissues (70.3% vs. 29.7%, p=0.02) and was correlated with a more advanced TNM stage (III vs. I+II; 75.9% vs. 66.3%, p=0.02), lymph node metastasis (with vs. without; 75.9% vs. 66.3%, p=0.02), and patients without a family history of CRC (78.7% vs. 62.1%, p=0.047). Conclusion. This study demonstrates that high concentrations of H-2 exert an inhibitory effect on CRC by inhibiting the pAKT/SCD1 pathway. Further studies are warranted for clinical evaluation of H-2 as SCD1 inhibitor to target CRC.