Inhibition of Tyrosine 3-Monooxygenase/Tryptophan 5-Monooxygenase Activation Protein Zeta (YWHAZ) Overcomes Drug Resistance and Tumorigenicity in Ovarian Cancer

Background/Aims: Cancer stem-like cells are the main cause of tumor occurrence, progression, and therapeutic resistance. However, the precise signals required for the maintenance of the stem-like traits of these cells in ovarian cancer remain elusive. We have thus worked to elucidate the functional role of Tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein zeta (YWHAZ), a gene encoding the 14-3-3ζ protein, in the regulation of multidrug resistance and stem cell-like traits in ovarian cancer. Methods: We detected the YWHAZ levels in human ovarian cancer specimens and cell lines using quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and western blots. MTS assays, soft agar colony formation assays, migration assays, cell cycle analysis, sphere formation assays, and flow cytometry were applied to investigate the functional role of YWHAZ in ovarian cancer. Results: Our data reveals substantially increased YWHAZ expression in both cisplatin- and paclitaxel-resistant ovarian cancer cells. Silencing YWHAZ restored the sensitivity of resistant ovarian cancer cells to cisplatin and paclitaxel. Furthermore, in vitro studies showed that down-regulation of YWHAZ inhibited cell cycle progression, migration, and the expression of stem cell markers. Moreover, tumorigenicity was suppressed in tumor-bearing BALB/c nude mice following YWHAZ knockdown. Additionally, we demonstrated that the expression of YWHAZ was directly down-regulated by miR-30e in resistant ovarian cancer cells. Conclusion: Our results have led to new insights into the essential role of YWHAZ in the regulation of tumourigenesis, stem-like traits, and drug resistance in ovarian cancer, thereby helping to identify a potential target for ovarian cancer therapy.