Lingyun Zhang

FLOT1 Is a Novel Serum Biomarker of Ovarian Cancer Targeted by N6‐methyladenosine Modification Inhibition

ABSTRACTOvarian cancer (OC) is a deadly disease and lacks a precise marker for diagnosis worldwide. Our previous work has shown the overexpression of flotillin‐1 (FLOT1) in OC tissue. To improve diagnostic sensitivity and accuracy, we evaluated the serum level of FLOT1 in OC patients and found that the serum concentration of FLOT1 as well as CA125 was significantly increased in patients with OC compared with healthy control (p < 0.01) and those with benign tumors (p < 0.05). The detection rate (above the upper limit of a cut‐off value) of FLOT1 and CA125 was 77.78% and 72.22%, respectively, in patients with OC, which was increased to 88.89% in combination. The elevation of FLOT1 was confirmed in the serum of nude mice after the implantation of human OC cells. A high level of FLOT1 protein in the serum was positively correlated with the overexpression of FLOT1 protein in OC tissues. Furthermore, the level of m6A modification of FLOT1 mRNA was significantly high in OC cells compared with normal ovarian epithelial cells, leading to an increase in FLOT1 mRNA expression. Application of a methylation inhibitor, 3‐deazaadenosine, decreased FLOT1 mRNA expression in OC cells and suppressed tumor formation in a xenograft mouse model. In conclusion, the current study demonstrated that FLOT1 is a novel serum biomarker of OC and can be targeted by m6A modification inhibition. These data highlight the potential application of FLOT1 as a diagnostic marker and a therapeutic target for patients with OC.

Targeting PNPO to suppress tumor growth via inhibiting autophagic flux and to reverse paclitaxel resistance in ovarian cancer

AbstractOur previous study showed that pyridoxine 5’-phosphate oxidase (PNPO) is a tissue biomarker of ovarian cancer (OC) and has a prognostic implication but detailed mechanisms remain unclear. The current study focused on PNPO-regulated lysosome/autophagy-mediated cellular processes and the potential role of PNPO in chemoresistance. We found that PNPO was overexpressed in OC cells and was a prognostic factor in OC patients. PNPO significantly promoted cell proliferation via the regulation of cyclin B1 and phosphorylated CDK1 and shortened the G2M phase in a cell cycle. Overexpressed PNPO enhanced the biogenesis and perinuclear distribution of lysosomes, promoting the degradation of autophagosomes and boosting the autophagic flux. Further, an autolysosome marker LAMP2 was upregulated in OC cells. Silencing LAMP2 suppressed cell growth and induced cell apoptosis. LAMP2-siRNA blocked PNPO action in OC cells, indicating that the function of PNPO on cellular processes was mediated by LAMP2. These data suggest the existence of the PNPO-LAMP2 axis. Moreover, silencing PNPO suppressed xenographic tumor formation. Chloroquine counteracted the promotion effect of PNPO on autophagic flux and inhibited OC cell survival, facilitating the inhibitory effect of PNPO-shRNA on tumor growth in vivo. Finally, PNPO was overexpressed in paclitaxel-resistant OC cells. PNPO-siRNA enhanced paclitaxel sensitivity in vitro and in vivo. In conclusion, PNPO has a regulatory effect on lysosomal biogenesis that in turn promotes autophagic flux, leading to OC cell proliferation, and tumor formation, and is a paclitaxel-resistant factor. These data imply a potential application by targeting PNPO to suppress tumor growth and reverse PTX resistance in OC.