Experimental & Molecular Medicine

Dihydroartemisinin inhibits metastatic potential and cancer stemness by modulating the miR-200b–BMI-1/VEGF-A axis in ovarian cancer

Abstract Despite therapeutic advances, ovarian cancer remains a major clinical challenge owing to its frequent metastasis and chemoresistance, which are often driven by cancer stem cells (CSCs) and proangiogenic signaling. Here we demonstrated that dihydroartemisinin (DHA), a derivative of the antimalarial drug artemisinin, inhibits CSC characteristics, tumor neovascularization and resistance to carboplatin via a microRNA-dependent mechanism in ovarian cancer. DHA substantially inhibited CSC properties, tumorigenicity and vascular endothelial growth factor A (VEGF-A)-mediated tumor neovascularization in ovarian cancer. Moreover, the combined treatment with DHA and carboplatin produced a synergistic effect that reduced tumor burden, chemoresistance and peritoneal dissemination in vivo. Mechanistically, DHA downregulated BMI-1 and VEGF-A/vascular endothelial growth factor receptor 2 (VEGFR2), which are critical factors in CSC maintenance and metastasis, via the upregulation of miR-200b. An analysis of ovarian tumor tissues collected from patients enrolled in our clinical cohort revealed that dual positivity for BMI-1 and VEGF-A was associated with poor progression-free survival. Overall, DHA targets the miR-200b–BMI-1/VEGF-A axis to suppress cancer stemness and metastatic potential, highlighting its therapeutic promise in overcoming the limitations of standard chemotherapy for ovarian cancer. The clinical trial number for this study is not applicable.

A stearate-rich diet and oleate restriction directly inhibit tumor growth via the unfolded protein response

Abstract Fatty acids are known to have significant effects on the properties of cancer cells. Therefore, these compounds have been incorporated into therapeutic strategies. However, few studies have examined the effects of individual fatty acids and their interactions in depth. This study analyzed the effects of various fatty acids on cancer cells and revealed that stearic acid, an abundant saturated fatty acid, had a stronger inhibitory effect on cell growth than did palmitic acid, which is also an abundant saturated fatty acid, by inducing DNA damage and apoptosis through the unfolded protein response (UPR) pathway. Intriguingly, the negative effects of stearate were reduced by the presence of oleate, a different type of abundant fatty acid. We combined a stearate-rich diet with the inhibition of stearoyl-CoA desaturase-1 to explore the impact of diet on tumor growth. This intervention significantly reduced tumor growth in both ovarian cancer models and patient-derived xenografts (PDXs), including those with chemotherapy resistance, notably by increasing stearate levels while reducing oleate levels within the tumors. Conversely, the negative effects of a stearate-rich diet were mitigated by an oleate-rich diet. This study revealed that dietary stearate can directly inhibit tumor growth through mechanisms involving DNA damage and apoptosis mediated by the UPR pathway. These results suggest that dietary interventions, which increase stearic acid levels while decreasing oleic acid levels, may be promising therapeutic strategies for cancer treatment. These results could lead to the development of new cancer treatment strategies.

RNA m5C modification upregulates E2F1 expression in a manner dependent on YBX1 phase separation and promotes tumor progression in ovarian cancer

Abstract5-Methylcytosine (m5C) is a common RNA modification that modulates gene expression at the posttranscriptional level, but the crosstalk between m5C RNA modification and biomolecule condensation, as well as transcription factor-mediated transcriptional regulation, in ovarian cancer, is poorly understood. In this study, we revealed that the RNA methyltransferase NSUN2 facilitates mRNA m5C modification and forms a positive feedback regulatory loop with the transcription factor E2F1 in ovarian cancer. Specifically, NSUN2 promotes m5C modification of E2F1 mRNA and increases its stability, and E2F1 binds to the NSUN2 promoter, subsequently reciprocally activating NSUN2 transcription. The RNA binding protein YBX1 functions as the m5C reader and is involved in NSUN2-mediated E2F1 regulation. m5C modification promotes YBX1 phase separation, which upregulates E2F1 expression. In ovarian cancer, NSUN2 and YBX1 are amplified and upregulated, and higher expression of NSUN2 and YBX1 predicts a worse prognosis for ovarian cancer patients. Moreover, E2F1 transcriptionally regulates the expression of the oncogenes MYBL2 and RAD54L, driving ovarian cancer progression. Thus, our study delineates a NSUN2-E2F1-NSUN2 loop regulated by m5C modification in a manner dependent on YBX1 phase separation, and this previously unidentified pathway could be a promising target for ovarian cancer treatment.

COL1A1-induced LOXL2 promotes ovarian cancer metastasis via a feedback loop upon inhibiting EGFR lysosomal degradation

Abstract Widespread peritoneal metastasis is a key reason for high mortality in ovarian cancer and understanding its mechanisms will offer new targets for the effective treatment of metastatic ovarian cancer. Our previous research revealed that collagen type I alpha 1 (COL1A1)-induced upregulation of lysyl oxidase-like 2 (LOXL2) was markedly overexpressed in ovarian cancer tissue samples and ascites. LOXL2 serves as an independent risk factor for predicting prognosis and its high expression is associated with high-risk clinical factors. LOXL2 promoted migration and invasion of ovarian cancer cells and metastasis of transplanted tumors in the xenograft mouse model. Here we determined that, mechanistically, COL1A1 activated the EGFR–MEK–ERK signaling pathway, which subsequently facilitated the nuclear translocation of SP1. SP1 binds to the promoter region of LOXL2, augmenting its transcription. Meanwhile, LOXL2 interacts with EGFR, protecting it from lysosomal degradation and enhancing protein stability. Finally, EGFR activates the MEK–ERK signaling pathway, promoting the translocation of SP1 and forming positive feedback. Our findings confirmed the molecular mechanism by which COL1A1-induced upregulation of LOXL2 promotes ovarian cancer metastasis through a positive feedback loop involving EGFR–MEK–ERK–SP1, offering novel scientific insights and potential therapeutic targets for inhibiting ovarian cancer metastasis.

Integrative analysis reveals early epigenetic alterations in high-grade serous ovarian carcinomas

AbstractHigh-grade serous ovarian carcinoma (HGSOC) is the most lethal gynecological malignancy. To date, the profiles of gene mutations and copy number alterations in HGSOC have been well characterized. However, the patterns of epigenetic alterations and transcription factor dysregulation in HGSOC have not yet been fully elucidated. In this study, we performed integrative omics analyses of a series of stepwise HGSOC model cells originating from human fallopian tube secretory epithelial cells (HFTSECs) to investigate early epigenetic alterations in HGSOC tumorigenesis. Assay for transposase-accessible chromatin using sequencing (ATAC-seq), chromatin immunoprecipitation sequencing (ChIP-seq), and RNA sequencing (RNA-seq) methods were used to analyze HGSOC samples. Additionally, protein expression changes in target genes were confirmed using normal HFTSECs, serous tubal intraepithelial carcinomas (STICs), and HGSOC tissues. Transcription factor motif analysis revealed that the DNA-binding activity of the AP-1 complex and GATA family proteins was dysregulated during early tumorigenesis. The protein expression levels of JUN and FOSL2 were increased, and those of GATA6 and DAB2 were decreased in STIC lesions, which were associated with epithelial-mesenchymal transition (EMT) and proteasome downregulation. The genomic region around the FRA16D site, containing a cadherin cluster region, was epigenetically suppressed by oncogenic signaling. Proteasome inhibition caused the upregulation of chemokine genes, which may facilitate immune evasion during HGSOC tumorigenesis. Importantly, MEK inhibitor treatment reversed these oncogenic alterations, indicating its clinical effectiveness in a subgroup of patients with HGSOC. This result suggests that MEK inhibitor therapy may be an effective treatment option for chemotherapy-resistant HGSOC.

Targeting the splicing factor SNRPB inhibits endometrial cancer progression by retaining the POLD1 intron

Abstract Dysregulated alternative splicing has been closely linked to the initiation and progression of tumors. Nevertheless, the precise molecular mechanisms through which splicing factors regulate endometrial cancer progression are still not fully understood. This study demonstrated elevated expression of the splicing factor SNRPB in endometrial cancer samples. Furthermore, our findings indicate that high SNRPB expression is correlated with poor prognosis in patients with endometrial cancer. Functionally, SNRPB inhibition hindered the proliferative and metastatic capacities of endometrial cancer cells. Mechanistically, we revealed that SNRPB knockdown decreased POLD1 expression and that POLD1 intron 22 was retained after SNRPB silencing in endometrial cancer cells, as determined via RNA sequencing data analysis. The retained intron 22 of POLD1 created a premature termination codon, leading to the absence of amino acids 941–1,107 and the loss of the site of interaction with PCNA, which is essential for POLD1 enzyme activity. In addition, POLD1 depletion decreased the increase in the malignancy of endometrial cancer cells overexpressing SNRPB. Furthermore, miR-654-5p was found to bind directly to the 3′ untranslated region of SNRPB, resulting in SNRPB expression inhibition in endometrial cancer. Antisense oligonucleotide-mediated SNRPB inhibition led to a decrease in the growth capacity of a cell-derived xenograft model and a patient with endometrial cancer-derived xenograft model. Overall, SNRPB promotes the efficient splicing of POLD1 by regulating intron retention, ultimately contributing to high POLD1 expression in endometrial cancer. The oncogenic SNRPB–POLD1 axis is an interesting therapeutic target for endometrial cancer, and antisense oligonucleotide-mediated silencing of SNRPB may constitute a promising therapeutic approach for treating patients with endometrial cancer.

Metastatic pattern of ovarian cancer delineated by tracing the evolution of mitochondrial DNA mutations

AbstractOvarian cancer (OC) is the most lethal gynecologic tumor and is characterized by a high rate of metastasis. Challenges in accurately delineating the metastatic pattern have greatly restricted the improvement of treatment in OC patients. An increasing number of studies have leveraged mitochondrial DNA (mtDNA) mutations as efficient lineage-tracing markers of tumor clonality. We applied multiregional sampling and high-depth mtDNA sequencing to determine the metastatic patterns in advanced-stage OC patients. Somatic mtDNA mutations were profiled from a total of 195 primary and 200 metastatic tumor tissue samples from 35 OC patients. Our results revealed remarkable sample-level and patient-level heterogeneity. In addition, distinct mtDNA mutational patterns were observed between primary and metastatic OC tissues. Further analysis identified the different mutational spectra between shared and private mutations among primary and metastatic OC tissues. Analysis of the clonality index calculated based on mtDNA mutations supported a monoclonal tumor origin in 14 of 16 patients with bilateral ovarian cancers. Notably, mtDNA-based spatial phylogenetic analysis revealed distinct patterns of OC metastasis, in which a linear metastatic pattern exhibited a low degree of mtDNA mutation heterogeneity and a short evolutionary distance, whereas a parallel metastatic pattern showed the opposite trend. Moreover, a mtDNA-based tumor evolutionary score (MTEs) related to different metastatic patterns was defined. Our data showed that patients with different MTESs responded differently to combined debulking surgery and chemotherapy. Finally, we observed that tumor-derived mtDNA mutations were more likely to be detected in ascitic fluid than in plasma samples. Our study presents an explicit view of the OC metastatic pattern, which sheds light on efficient treatment for OC patients.

PBK drives PARP inhibitor resistance through the TRIM37/NFκB axis in ovarian cancer

AbstractResistance to PARP inhibitors (PARPi) remains a therapeutic challenge in ovarian cancer patients. PDZ-binding kinase (PBK) participates in the chemoresistance of many malignancies. However, the role of PBK in PARPi resistance of ovarian cancer is obscure. In the current study, we demonstrated that overexpression of PBK contributed to olaparib resistance in ovarian cancer cells. Knockdown of PBK sensitized olaparib-resistant SKOV3 cells to olaparib. Inhibition of PBK using a specific inhibitor enhanced the therapeutic efficiency of olaparib. Mechanically, PBK directly interacted with TRIM37 to promote its phosphorylation and nuclear translocation. which subsequently activates the NFκB pathway. Additionally, PBK enhanced olaparib resistance of ovarian cancer by regulating the NFκB/TRIM37 axis in vitro and in vivo. In conclusion, PBK confers ovarian cancer resistance to PARPi through activating the TRIM37-mediated NFκB pathway, and targeted inhibition of PBK provided the new therapy to improve PARPi treatment outcomes for ovarian cancer patients.

Mutational signatures and chromosome alteration profiles of squamous cell carcinomas of the vulva.

Vulvar squamous cell carcinoma (SCC) consists of two different etiologic categories: human papilloma virus (HPV)-associated (HPV (+)) and HPV-non-associated (HPV (-)). There have been no genome-wide studies on the genetic alterations of vulvar SCCs or on the differences between HPV (+) and HPV (-) vulvar SCCs. In this study, we performed whole-exome sequencing and copy number profiling of 6 HPV (+) and 9 HPV (-) vulvar SCCs and found known mutations (TP53, CDKN2A and HRAS) and copy number alterations (CNAs) (7p and 8q gains and 2q loss) in HPV (-) SCCs. In HPV (+), we found novel mutations in PIK3CA, BRCA2 and FBXW7 that had not been reported in vulvar SCCs. HPV (-) SCCs exhibited more mutational loads (numbers of nonsilent mutations and driver mutations) than HPV (+) SCCs, but the CNA loads and mutation signatures between HPV (+) and HPV (-) SCCs did not differ. Of note, 40% and 40% of the 15 vulvar SCCs harbored PIK3CA and FAT1 alterations, respectively. In addition, we found that the SCCs harbored kataegis (a localized hypermutation) in 2 HPV (+) SCCs and copy-neutral losses of heterozygosity in 4 (one HPV (+) and 3 HPV (-)) SCCs. Our data indicate that HPV (+) and HPV (-) vulvar SCCs may have different mutation and CNA profiles but that there are genomic features common to SCCs. Our data provide useful information for both HPV (+) and HPV (-) vulvar SCCs and may aid in the development of clinical treatment strategies.