ZSWIM4 inhibition improves chemosensitivity in epithelial ovarian cancer cells by suppressing intracellular glycine biosynthesis

BACKGROUND

Zinc finger SWIM-type containing 4 (ZSWIM4) induces drug resistance in breast cancer cells. However, its role in epithelial ovarian cancer (EOC) remains unknown. In this study, we aimed to investigate the clinical significance of ZSWIM4 expression in EOC and develop new clinical therapeutic strategies for EOC.

METHODS

ZSWIM4 expression in control and EOC tumor tissues was examined using immunohistochemistry. Lentiviral transduction, Cell Counting Kit-8 assay, tumorsphere formation assay, flow cytometry, western blotting, and animal xenograft model were used to assess the role of ZSWIM4 in chemotherapy. Cleavage Under Targets and Tagmentation (CUT&Tag) assays, chromatin immunoprecipitation assays, and luciferase reporter assays were used to confirm FOXK1-mediated upregulation of ZSWIM4 expression. The mechanism by which ZSWIM4 inhibition improves chemosensitivity was evaluated using RNA-sequencing. A ZSWIM4-targeting inhibitor was explored by virtual screening and surface plasmon resonance analysis. Patient-derived organoid (PDO) models were constructed from EOC tumor tissues with ZSWIM4 expression.

RESULTS

ZSWIM4 was overexpressed in EOC tumor tissues and impaired patient prognoses. Its expression correlated positively with EOC recurrence. ZSWIM4 expression was upregulated following carboplatin treatment, which, in turn, contributed to chemoresistance. Silencing ZSWIM4 expression sensitized EOC cells to carboplatin treatment in vitro and in vivo. FOXK1 could bind to the GTAAACA sequence of the ZSWIM4 promoter region to upregulate ZSWIM4 transcriptional activity and FOXK1 expression increased following carboplatin treatment, leading to an increase in ZSWIM4 expression. Mechanistically, ZSWIM4 knockdown downregulated the expression of several rate-limiting enzymes involved in glycine synthesis, causing a decrease in intracellular glycine levels, thus enhancing intracellular reactive oxygen species production induced by carboplatin treatment. Compound IPN60090 directly bound to ZSWIM4 protein and exerted a significant chemosensitizing effect in both EOC cells and PDO models.

CONCLUSIONS

ZSWIM4 inhibition enhanced EOC cell chemosensitivity by ameliorating intracellular glycine metabolism reprogramming, thus providing a new potential therapeutic strategy for EOC.

SWIM domain protein ZSWIM4 is required for JAK2 inhibition resistance in breast cancer

AIMS

Janus kinase 2 (JAK2)/signal transducer and activator of transcription (STAT) signaling plays a critical role in the progression of breast cancer. However, a small part of tumor cells survived from the killing effect of JAK2 inhibitor. We aimed to find out the mechanism of drug resistance in breast cancer cells and develop new therapeutic strategies.

MATERIALS AND METHODS

The anti-tumor effect of TG101209 in breast cancer cells was confirmed by cell counting kit 8 and flow cytometry. Western blotting was used to determine the up-regulation of zinc finger SWIM-type containing 4 (ZSWIM4) induced by TG101209. In vitro and in vivo experiments were performed to evaluate the role of ZSWIM4 in the resistance of breast cancer cells to TG101209. Through the determination and analysis of 50% inhibiting concentration (IC₅₀) curves, the effect of combination therapy was confirmed.

KEY FINDINGS

Our data indicate that the elevated expression of ZSWIM4 contributes to JAK2 inhibition resistance, as knockdown of ZSWIM4 significantly enhances the sensitivity of breast cancer cells to TG101209 and over-expression of this gene mitigates the killing effect. Furthermore, the expression of vitamin D receptor (VDR) and utilization of 1α,25-(OH)2VD3 is decreased in ZSWIM4-knockdown breast cancer cells. VDR-silencing or GW0742-mediated blockade of VDR activity can partially reverse the JAK2 inhibition resistance.

SIGNIFICANCE

Our data implicated that ZSWIM4 might be an inducible resistance gene of JAK2 inhibition in breast cancer cells. The combination of JAK2 inhibitor and VDR inhibitor may achieve better coordinated therapeutic effect in breast cancer.