ISG15 is downregulated by KLF12 and implicated in maintenance of cancer stem cell-like features in cisplatin-resistant ovarian cancer.

Drug resistance is often developed during clinical chemotherapy of ovarian cancers. The ubiquitin-like protein interferon-stimulated gene 15 (ISG15) is possibly dependent on tumour context to promote or suppress progression of various tumours. The ubiquitin-like protein interferon-stimulated gene 15 (ISG15) was decreased in cisplatin-resistant ovarian cancer cells. The current study identified that both ectopic wild type and nonISGylatable mutant ISG15 expression inhibited CSC-like phenotypes of cisplatin-resistant ovarian cancer cells. Moreover, ectopic ISG15 expression suppressed tumour formation in nude mice. In addition, ISG15 downregulation promoted CSC-like features of cisplatin-sensitive ovarian cancer cells. Furthermore, low ISG15 expression was associated with poor prognosis in patients with ovarian cancer. Transcriptional repressor Krüppel-like factor 12 (KLF12) downregulated ISG15 in cisplatin-resistant cells. Our data indicated that downregulating ISG15 expression, via weakening effect of KLF12, might be considered as new therapeutic strategy to inhibit CSC phenotypes in the treatment of cisplatin-resistant ovarian cancer.