Biomarkers of drug resistance in ovarian cancer – an update

Expression of human dCTP pyrophosphatase 1 (DCTPP1) and its association with cisplatin resistance characteristics in ovarian cancer

Cisplatin (DDP) resistance is a major challenge in treating ovarian cancer patients. A recently discovered enzyme called dCTP pyrophosphatase 1 (DCTPP1) has been implicated in regulating cancer characteristics, including drug responses. In this study, we aimed to understand the role of DCTPP1 in cancer progression and cisplatin response. Using publicly available databases, we analysed the expression and clinical significance of DCTPP1 in ovarian cancer. Our bioinformatics analysis confirmed that DCTPP1 is significantly overexpressed in ovarian cancer and is closely associated with tumour progression and poor prognosis after cisplatin treatment. We also found that DCTPP1 located in oxidoreductase complex and may be involved in various biological processes related to cisplatin resistance, including pyrimidine nucleotide metabolism, the P53 signalling pathway and cell cycle signalling pathways. We observed higher expression of DCTPP1 in cisplatin-resistant cells (SKOV3/DDP) and samples compared to their sensitive counterparts. Additionally, we found that DCTPP1 expression was only enhanced in SKOV3/S cells when treated with cisplatin, indicating different expression patterns of DCTPP1 in cisplatin-sensitive and cisplatin-resistant cancer cells. Our study further supports the notion that cisplatin induces intracellular reactive oxygen species (ROS) and triggers cancer cell death through excessive oxidative stress. Knocking out DCTPP1 reversed the drug resistance of ovarian cancer cells by enhancing the intracellular antioxidant stress response and accumulating ROS. Based on our research findings, we conclude that DCTPP1 has prognostic value for ovarian cancer patients, and targeting DCTPP1 may be clinically significant in overcoming cisplatin resistance in ovarian cancer.

Enhancing precision medicine: a nomogram for predicting platinum resistance in epithelial ovarian cancer

BACKGROUND

This study aimed to develop a novel nomogram that can accurately estimate platinum resistance to enhance precision medicine in epithelial ovarian cancer(EOC).

METHODS

EOC patients who received primary therapy at the General Hospital of Ningxia Medical University between January 31, 2019, and June 30, 2021 were included. The LASSO analysis was utilized to screen the variables which contained clinical features and platinum-resistance gene immunohistochemistry scores. A nomogram was created after the logistic regression analysis to develop the prediction model. The consistency index (C-index), calibration curve, receiver operating characteristic (ROC) curve, and decision curve analysis (DCA) were used to assess the nomogram's performance.

RESULTS

The logistic regression analysis created a prediction model based on 11 factors filtered down by LASSO regression. As predictors, the immunohistochemical scores of CXLC1, CXCL2, IL6, ABCC1, LRP, BCL2, vascular tumor thrombus, ascites cancer cells, maximum tumor diameter, neoadjuvant chemotherapy, and HE4 were employed. The C-index of the nomogram was found to be 0.975. The nomogram's specificity is 95.35% and its sensitivity, with a cut-off value of 165.6, is 92.59%, as seen by the ROC curve. After the nomogram was externally validated in the test cohort, the coincidence rate was determined to be 84%, and the ROC curve indicated that the nomogram's AUC was 0.949.

CONCLUSION

A nomogram containing clinical characteristics and platinum gene IHC scores was developed and validated to predict the risk of EOC platinum resistance.

A Novel ZIP4-HDAC4-VEGFA Axis in High-Grade Serous Ovarian Cancer

Simple Summary

Despite tremendous research efforts, epithelial ovarian cancer (EOC) remains one of the most difficult cancers to detect early and treat successfully for >5-year survival. We have recently shown that ZIP4, a zinc transporter, is a novel cancer stem cell (CSC) marker and a therapeutic target for EOC. The current work focuses on developing new strategies to target ZIP4 and inhibit its CSC activities in EOC. We found that cells expressing high levels of ZIP4 were supersensitive to a group of inhibitors called HDACis. One of the major targets of these inhibitors is a protein called HDAC4. We revealed the new molecular bases for the ZIP4-HDAC4 axis and tested the efficacies of targeting this axis in the lab and in mouse models. Our study provides a new mechanistic-based targeting strategy for EOC.

Abstract

We have recently identified ZIP4 as a novel cancer stem cell (CSC) marker in high-grade serous ovarian cancer (HGSOC). While it converts drug-resistance to cisplatin (CDDP), we unexpectedly found that ZIP4 induced sensitization of HGSOC cells to histone deacetylase inhibitors (HDACis). Mechanistically, ZIP4 selectively upregulated HDAC IIa HDACs, with little or no effect on HDACs in other classes. HDAC4 knockdown (KD) and LMK-235 inhibited spheroid formation in vitro and tumorigenesis in vivo, with hypoxia inducible factor-1 alpha (HIF1α) and endothelial growth factor A (VEGFA) as functional downstream mediators of HDAC4. Moreover, we found that ZIP4, HDAC4, and HIF1α were involved in regulating secreted VEGFA in HGSOC cells. Furthermore, we tested our hypothesis that co-targeting CSC via the ZIP4-HDAC4 axis and non-CSC using CDDP is necessary and highly effective by comparing the effects of ZIP4-knockout/KD, HDAC4-KD, and HDACis, in the presence or absence of CDDP on tumorigenesis in mouse models. Our results showed that the co-targeting strategy was highly effective. Finally, data from human HGSOC tissues showed that ZIP4 and HDAC4 were upregulated in a subset of recurrent tumors, justifying the clinical relevance of the study. In summary, our study provides a new mechanistic-based targeting strategy for HGSOC.

Transcriptome-based stemness indices analysis reveals platinum-based chemo-theraputic response indicators in advanced-stage serous ovarian cancer

Serous ovarian cancer (SOC) is a main histological subtype of ovarian cancer, in which cancer stem cells (CSC) are responsible for its chemoresistance. However, the underlying modulation mechanisms of chemoresistance led by cancer stemness are still undefined. We aimed to investigate potential drug-response indicators among stemness-associated biomarkers in advanced SOC samples. The mRNA expression-based stemness index (mRNAsi) of The Cancer Genome Atlas (TCGA) was evaluated and corrected by tumor purity. Weighted gene co-expression network analysis (WGCNA) was utilized to explore the gene modules and key genes involved in stemness characteristics. We found that mRNAsi and corrected mRNAsi scores were both greater in tumors of Grade 3 and 4 than that of Grade 1 and 2. Forty-two key genes were obtained from the most significant mRNAsi-related gene module. Functional annotation revealed that these key genes were mainly involved in the mitotic division. Thirteen potential platinum-response indicators were selected from the genes enriched to platinum-response associated pathways. Among them, we identified 11 genes with prognostic value of progression-free survival (PFS) in advanced SOC patients treated with platinum and 7 prognostic genes in patients treated with a combination of platinum and taxol. The expressions of the 13 key genes were also validated between platinum-resistant and -sensitive SOC samples of advanced stages in two Gene Expression Omnibus (GEO) datasets. The results revealed that CDC20 was a potential platinum-sensitivity indicator in advanced SOC. These findings may provide a new insight for chemotherapies in advanced SOC patients clinically.

Subtype specific biomarkers associated with chemoresistance in epithelial ovarian cancer

In spite of the advent of many high throughput technologies, tumor tissue biomarkers are still the gold standard for diagnosis and prognosis of different malignancies including epithelial ovarian cancer (EOC). EOC is a heterogeneous disease comprised of five major subtypes which show distinct clinicopathological features and therapy response. Acquirement of chemoresistance toward therapy is a major challenge for successful treatment outcome in EOC patients. Several markers have been tested by immunohistochemical method to evaluate their prognostic merit to predict clinical outcome. However, a vast majority of such markers have been assessed for high-grade serous and clear cell ovarian cancer, among all subtypes of EOC. The current review elaborates upon those biomarkers that can potentially predict chemoresistance with subtype specificity.

Genome-wide analysis of microRNA to evaluate prognostic markers in isolated cancer glands and surrounding stroma in high-grade serous ovarian carcinoma

The molecular mechanisms responsible for the progression of ovarian cancer remain incompletely understood. By targeting multiple cancer-related genes, microRNAs (miRNAs) have been identified as key regulators of cancer development and progression. In addition, the microenvironment, which constitutes cancer glands and the surrounding stromal tissue at the invasive front, has an important role in cancer progression. Using array-based analysis of 14 cases (cohort 1), the aim of the present study was to evaluate global miRNA expression in cancerous glands and surrounding stromal tissues (isolated using a crypt isolation method), in order to identify potential prognostic markers of high-grade serous carcinoma (HGSC). Reverse transcription-quantitative PCR was also used to verify the results in cohort 1 (14 cases) and in 16 additional HGSC cases (cohort 2; verification cohort). Firstly, miRNA expression levels were compared between HGSC and normal samples among both the isolated cancer gland and stromal tissue samples. Secondly, miRNA expression was compared between HGSC cases with recurrence and those without recurrence among the isolated cancer gland and stromal tissue samples. The results revealed six and seven miRNAs identified in both of the aforementioned comparisons in isolated cancer glands and surrounding stromal tissue, respectively. Furthermore, downregulation of miRNA-214-3p in isolated cancer glands and downregulation of miRNA-320c in the corresponding stromal tissue were associated with a decrease in disease-free survival (without recurrence) in cohort 2. These findings indicated that specific miRNAs expressed in cancer cells and surrounding stromal cells of HGSC may be potential biomarkers predicting patient prognosis.

Identification of key factors associated with early- and late-onset ovarian serous cystadenocarcinoma

Aim: To uncover the molecular mechanisms of early-onset ovarian serous cystadenocarcinoma (EOOSC; patients <50 years old) and late-onset ovarian serous cystadenocarcinoma (LOOSC; patients ≥50 years old). Materials & methods: Bioinformatics was utilized to identify the key factors. Results: 478 EOOSC and 899 LOOSC individual differentially expressed genes were identified and enriched in different pathways. The expression of key genes LAG3, LRRC63 and MT1B significantly influenced the overall survival of EOOSC patients. The expression of key genes RDH12, NTSR1, ZSCAN16, CT45A3 and EPPIN_WFDC6 significantly affected the overall survival of LOOSC patients. Conclusions: The molecular mechanisms of EOOSC and LOOSC appear to be different, so that patients might be treated individually in respect of age.

Mutation analysis and genomic imbalances of cells found in effusion fluids from patients with ovarian cancer

Ovarian carcinomas and carcinosarcomas often cause malignant effusions, an accumulation within serous cavities of fluid containing cancer cells. Few studies have focused on the molecular alterations and genetic mechanisms behind effusion formation. The present study investigated the mutation status of TP53, PIK3CA, KRAS, HRAS, NRAS and BRAF in effusion fluids from 103 patients with ovarian cancer. In addition, array Comparative Genomic Hybridization (aCGH) analysis was performed on 20 effusions from patients with high-grade serous carcinoma (10 cases positive for TP53 mutation and 10 with TP53 wild-type). TP53 mutations, two of which were novel: c.826_830delCCTGT and c.475_476GC>TT, were identified in 44% of the cases. Mutations in KRAS, HRAS, and PIK3CA were identified in two, two and four cases, respectively. None of the effusions analysed showed NRAS or BRAF mutations. The aCGH analysis revealed highly imbalanced genomes similar to those described in primary ovarian carcinomas. No specific profile was indicated to distinguish tumors with TP53 mutations from those without. The molecular profiling of cells found in effusion fluids from patients with ovarian cancer thus showed considerable molecular heterogeneity. TP53 seems to be the most frequently mutated gene in these cells and may serve a leading role in the metastatic process.

Role of the Exosome Secretion Machinery in Ovarian Carcinoma: In Vitro and In Vivo Models

Objective. We recently reported on the expression and clinical role of molecules that mediate exosome secretion in high-grade serous carcinoma. In the present study, the biological role of these molecules was analyzed. Methods. OVCAR8 and ES-2 ovarian carcinoma cells were studied using a combination of CRISPR/Cas9 technology and two 3D in vitro models—spheroids emulating effusions and alginate scaffolds representing solid lesions. Isolation of exosomes was validated by electron microscopy. TSAP6, NSMASE2, RAB27A, and RAB27B mRNA and protein levels were analyzed using qRT-PCR and Western blotting, respectively. Tumor aggressiveness was studied in vitro using scratch assay, invasion assay, and matrix metalloproteinase (MMP) activity assay and in vivo using a mouse model. Results. In OVCAR8 cells, mRNA expression of TSAP6 and RAB27A was significantly higher in spheroids compared to scaffolds, whereas the opposite was true for NSMASE2 mRNA. In ES-2 cells, TSAP6 and RAB27B mRNA expression was significantly higher in spheroids versus scaffolds. In addition, nSMase2 and TSAP6 protein expression was significantly higher in scaffolds compared to spheroids. CRISPR-edited cells with silencing of NSMASE2, TSAP6, and RAB27A/B had reduced migration, invasion, and MMP activity. Additionally, knockout (KO) of these molecules resulted in significantly diminished exosome secretion. In vivo assay showed that when injected to mice, OVCAR8 RAB27A/B KO cells, as opposed to control OVCAR8 cells, did not form ascites or visible tumor lesions and had reduced MMP expression. Conclusion. The present study provides evidence that different models for culturing ovarian carcinoma cells affect the expression of molecules mediating exosome secretion and that these molecules have a tumor-promoting role. Silencing these molecules may consequently have therapeutic relevance in this cancer.