The myo-inositol biosynthesis rate-limiting enzyme ISYNA1 suppresses the stemness of ovarian cancer via Notch1 pathway.

Cancer stem cells (CSCs) play a central role in ovarian cancer (OC), understanding regulatory mechanisms governing their stemness is critical. Here, we report ISYNA1, the rate-limiting enzyme in myo-inositol biosynthesis, as a suppressor of OC regulating cancer stemness. We identified ISYNA1 as a differentially expressed gene in normal ovary and ovarian cancer tissues, as well as OC cells and OCSCs. Low ISYNA1 expression correlated with poor prognosis in OC patients. In addition, ISYNA1 was negatively correlated with cancer stem cell (CSC) markers, and ISYNA1-related pathways were enriched in Wnt, Notch, and other critical cancer pathways. ISYNA1 deficiency promoted OC cell growth, migration, and invasion ability in vitro and in vivo. Knockdown of ISYNA1 increased stemness of OC cells, including self-renewal, CSC markers expression, ALDH activity, and proportion of CD44+/CD117+ CSCs. Conversely, ectopic overexpression of ISYNA1 suppresses cell proliferation, migration, invasion and stemness of OC cells. Mechanistically, ISYNA1 inhibits OC stemness by regulating myo-inositol to suppress Notch1 signaling. In summary, these data provide evidence that ISYNA1 act as a tumor suppressor in OC and a regulator of stemness, providing insight into potentially targetable pathways for ovarian cancer therapy.

Zinc finger and SCAN domain containing 1, ZSCAN1, is a novel stemness-related tumor suppressor and transcriptional repressor in breast cancer targeting TAZ.

Introduction: Cancer stem cells (CSCs) targeted therapy holds the potential for improving cancer management; identification of stemness-related genes in CSCs is necessary for its development. Methods: The Cancer Genome Atlas (TCGA) and the Molecular Taxonomy of Breast Cancer International Consortium (METABRIC) datasets were used for survival analysis. ZSCAN1 correlated genes was identified by Spearman correlation analysis. Breast cancer stem-like cells (BCSLCs) were isolated by sorting CD44+CD24- cells from suspension cultured breast cancer (BC) spheroids. The sphere-forming capacity and sphere- and tumor-initiating capacities were determined by sphere formation and limiting dilution assays. The relative gene expression was determined by qRT-PCR, western blot. Lentivirus system was used for gene manipulation. Nuclear run-on assay was employed to examine the levels of nascent mRNAs. DNA pull-down and Chromatin immunoprecipitation (ChIP) assays were used for determining the interaction between protein and target DNA fragments. Luciferase reporter assay was used for evaluating the activity of the promoter. Results and discussion: ZSCAN1 is aberrantly suppressed in BC, and this suppression indicates a bad prognosis. Ectopic expression of ZSCAN1 inhibited the proliferation, clonogenicity, and tumorigenicity of BC cells. ZSCAN1-overexpressing BCSLCs exhibited weakened stemness properties. Normal human mammary epithelial (HMLE) cells with ZSCAN1 depletion exhibited enhanced stemness properties. Mechanistic studies showed that ZSCAN1 directly binds to -951 ~ -925bp region of WWTR1 (encodes TAZ) promoter, inhibits WWTR1 transcription, thereby inhibiting the stemness of BCSCs. Our work thus revealed ZSCAN1 as a novel stemness-related tumor suppressor and transcriptional repressor in BC.

Luteolin directly binds to KDM4C and attenuates ovarian cancer stemness via epigenetic suppression of PPP2CA/YAP axis.

Long-term use of low-toxic natural products holds the promise for eradicating cancer stem cells. In this study, we report that luteolin, a natural flavonoid, attenuates the stemness of ovarian cancer stem cells (OCSCs) by directly binding to KDM4C and epigenetic suppression of PPP2CA/YAP axis. Ovarian cancer stem like cells (OCSLCs) isolated by suspension culture and CD133 + ALDH+ cell sorting was employed as OCSCs model. The maximal non-toxic dose of luteolin suppressed stemness properties, including sphere-forming capacity, the expression of OCSCs markers, sphere-initiating and tumor-initiating capacities, as well as the percentage of CD133 + ALDH+ cells of OCSLCs. Mechanistic study showed that luteolin directly binds to KDM4C, blocks KDM4C-induced histone demethylation of PPP2CA promoter, inhibits PPP2CA transcription and PPP2CA-mediated YAP dephosphorylation, thereby attenuating YAP activity and the stemness of OCSLCs. Furthermore, luteolin sensitized OCSLCs to traditional chemotherapeutic drugs in vitro and in vivo. In summary, our work revealed the direct target of luteolin and the underlying mechanism of the inhibitory effect of luteolin on the stemness of OCSCs. This finding thus suggests a novel therapeutic strategy for eradicating human OCSCs driven by KDM4C.