Karina Dahl Steffensen

Molecular phenotyping of human ovarian cancer stem cells unravels the mechanisms for repair and chemoresistance

A major burden in the treatment of ovarian cancer is the high percentage of recurrence and chemoresistance. Cancer stem cells (CSCs) provide a reservoir of cells that can self-renew, can maintain the tumor by generating differentiated cells [non-stem cells (non-CSCs)] which make up the bulk of the tumor and may be the primary source of recurrence. We describe the characterization of human ovarian cancer stem cells (OCSCs). These cells have a distinctive genetic profile that confers them with the capacity to recapitulate the original tumor, proliferate with chemotherapy, and promote recurrence. CSC identified in EOC cells isolated form ascites and solid tumors are characterized by: CD44+, MyD88+, constitutive NFκB activity and cytokine and chemokine production, high capacity for repair, chemoresistance to conventional chemotherapies, resistance to TNFα-mediated apoptosis, capacity to form spheroids in suspension, and the ability to recapitulate in vivo the original tumor. Chemotherapy eliminates the bulk of the tumor but it leaves a core of cancer cells with high capacity for repair and renewal. The molecular properties identified in these cells may explain some of the unique characteristics of CSCs that control self-renewal and drive metastasis. The identification and cloning of human OCSCs can aid in the development of better therapeutic approaches for ovarian cancer patients.

Cancers take their Toll--the function and regulation of Toll-like receptors in cancer cells

Cancer could be deemed as an abnormal and uncontrolled tissue repair process. Therefore, it would not be surprising that factors that function in the tissue repair process, such as cytokines, chemokines, growth factors and Toll-like receptor (TLR) ligands, as well as growth signals for compensatory proliferation, would also be key factors in regulating and enhancing cancer progression. The TLR pathways, which play a critical role in tissue repair, are also key regulators in cancer progression as well as chemoresistance. TLRs serve as cell surface sensors that can initiate pathways leading to proliferation and chemoresistance; as well as mediators that are able to regulate the infiltrating immune cells to provide further support for cancer progression.

The relationship of VEGF polymorphisms with serum VEGF levels and progression-free survival in patients with epithelial ovarian cancer

OBJECTIVE The vascular endothelial growth factor (VEGF) is an important regulator of angiogenesis and vascular permeability of tumors. In the present study we evaluated the relation of five single nucleotide polymorphisms (SNPs) in the VEGF gene with progression-free survival. Furthermore, we evaluated the functional significance of the SNPs as determined by the influence on serum VEGF levels in ovarian cancer. METHODS Serum from 143 consecutive ovarian cancer patients referred for first line platinum/paclitaxel treatment were analyzed for serum VEGF levels using commercially available enzyme-linked immunosorbent assay (ELISA). VEGF gene polymorphisms (-2578 C/A, -1154 G/A, -460 T/C, +405 G/C and +936C/T) were determined by real time PCR using genomic DNA extracted from whole blood samples. RESULTS VEGF serum levels were significantly higher in carriers of the 2578C, 460T and 405C, alleles compared to non-carriers (p=0.003, p=0.003 and p=0.001, respectively). There was no significant correlation between VEGF SNP genotypes and progression-free survival. In haplotype analysis, the multivariate survival analysis showed that progression-free survival (PFS) for the patients with the AGCGC haplotype was significantly improved compared to patients with other haplotypes (HR 1.9, p=0.036). CONCLUSIONS VEGF polymorphisms were found to be significantly related with serum VEGF levels. The AGCGC haplotype was found to be independently associated with improved PFS.

Prevalence of Epithelial Ovarian Cancer Stem Cells Correlates with Recurrence in Early-Stage Ovarian Cancer

Epithelial ovarian cancer stem cells (EOC stem cells) have been associated with recurrence and chemoresistance. CD44 and CK18 are highly expressed in cancer stem cells and function as tools for their identification and characterization. We investigated the association between the number of CD44+ EOC stem cells in ovarian cancer tumors and progression-free survival. EOC stem cells exist as clusters located close to the stroma forming the cancer stem cell “niche”. 17.1% of the samples reveled high number of CD44+ EOC stem cells (>20% positive cells). In addition, the number of CD44+ EOC stem cells was significantly higher in patients with early-stage ovarian cancer (FIGO I/II), and it was associated with shorter progression-free survival (P = 0.026). This study suggests that quantification of the number of EOC stem cells in the tumor can be used as a predictor of disease and could be applied for treatment selection in early-stage ovarian cancer.

The relationship of platinum resistance and ERCC1 protein expression in epithelial ovarian cancer.

Objective: Although platinum-based chemotherapy remains the cornerstone for treatment of ovarian cancer, some patients are resistant to the treatment and will therefore not benefit from the standard platinum-based chemotherapy. Preclinical and clinical data have suggested a potential use of excision repair cross-complementation group 1 enzyme (ERCC1) as a molecular predictor of clinical resistance to platinum-based chemotherapy. Excision repair cross-complementation group 1 enzyme is a key enzyme in the nucleotide excision repair pathway which is involved in the DNA repair mechanisms in tumor cells damaged by treatment with platinum agents. The primary aim of the present study was to investigate if immunohistochemical expression of ERCC1 protein was associated with resistance to standard combination carboplatin and paclitaxel chemotherapy in newly diagnosed ovarian cancer patients. Methods: Formalin-fixed, paraffin-embedded tissue sections from 101 patients with newly diagnosed ovarian cancer were used for immunohistochemical staining for the ERCC1 protein. All patients received carboplatin-paclitaxel combination chemotherapy. Results: Excision repair cross-complementation group 1 enzyme protein overexpression was found in 13.9% of the tumors. Platinum resistance was found in 75% of the tumors with positive ERCC1 protein expression compared with 27% among the patients with negative tumor staining for ERCC1 (P = 0.0013). These findings translated into a significant difference in progression-free survival in both univariate (P = 0.0012) and in multivariate analysis (P = 0.006). Conclusions: The data presented suggest a positive association between positive ERCC1 protein expression and clinical resistance to platinum-based chemotherapy.

The predictive value of serum VEGF in multiresistant ovarian cancer patients treated with bevacizumab

OBJECTIVE Bevacizumab, a humanized monoclonal antibody against VEGF (vascular endothelial growth factor), has shown antitumor activity, but so far no biomarkers have been identified to predict outcome. The purpose of the present study was to investigate the efficacy of bevacizumab in patients with multiresistant ovarian cancer and, furthermore, to investigate the possible predictive value of serum VEGF, VEGFR1-2 and VEGF gene polymorphisms. METHODS Patients received single-agent bevacizumab 10 mg/kg every 3 weeks. All patients were followed with CA 125 measurements and serum VEGF/VEGFR1-2 levels prior to each cycle. Endpoints were response rate (RR), progression-free survival (PFS) and overall survival (OS). RESULTS Thirty-eight patients were included. All patients were heavily pre-treated with a median of five prior regimens. The median number of bevacizumab treatments was 4. Overall response rate was 30% according to CA 125 (GCIG criteria). Median PFS was 5.9 months (95% CI, 3.5-9.4) and median OS was 8.6 months (95% CI, 6.6-12.8). The VEGF serum level decreased during treatment in all patients. A low pre-treatment VEGF level was predictive to response. The median value was 540 pg/ml and divided the patients into two groups with a response rate of 60% and 0%, respectively (p=0.0007). The difference translated to a significant difference in PFS (p=0.047) and OS (p=0.01). VEGF gene polymorphisms -2578, -1154, -460, +405, +936 did not reveal any association with response or survival and the same applied to serum VEGFR1-2. CONCLUSIONS Single agent bevacizumab has activity in ovarian cancer patients. Pre-treatment serum VEGF seems to have predictive value.

Prognostic impact of prechemotherapy serum levels of HER2, CA125, and HE4 in ovarian cancer patients.

Objective: Human epididymis protein 4 (HE4) has attracted a lot of interest as a relatively novel biomarker for ovarian carcinoma. Research focus has been directed at HE4 as a diagnostic tool with potential for better triage of women with adnexal masses but the prognostic aspect of HE4 in ovarian cancer patients remains to be elucidated. The aim of the present study was to investigate the prognostic value of prechemotherapy serum HER2, cancer antigen 125 (CA125), and HE4 levels in ovarian cancer patients receiving standard combination chemotherapy. Methods: Serum from 139 patients with newly diagnosed ovarian cancer was analyzed for HER2, CA125, and HE4 using enzyme-linked immunosorbent assay assays. Samples were collected just before first-line chemotherapy, and all patients were treated with carboplatin-paclitaxel combination chemotherapy. Results: Increasing levels of serum HE4 (grouped into quartiles) was significantly associated with worse progression-free survival (PFS) (P < 10−5) and overall survival (P < 10−5). After adjustment in the Cox model, HE4 serum levels remained an independent prognostic parameter for PFS, with a hazard ratio of 1.77 (95% confidence interval, 1.03-3.04; P = 0.040) for patients with HE4 levels above the median compared with patients with HE4 levels below the median. The shorter PFS for patients with high levels of HE4 also translated into an independent significant difference in overall survival (hazard ratio, 3.17 [95% confidence interval, 1.41-7.10]; P = 0.005). Serum HER2 and CA125 levels did not demonstrate an independent prognostic value. Conclusions: High levels of serum HE4 is a strong and independent indicator of worse prognosis in epithelial ovarian cancer patients.

Prognostic importance of vascular endothelial growth factor-A expression and vascular endothelial growth factor polymorphisms in epithelial ovarian cancer.

Introduction: Vascular endothelial growth factors (VEGFs) play a central role in angiogenesis and consequently, in various steps of ovarian carcinogenesis. Gene polymorphisms within the VEGF system have revealed a correlation with prognosis in some malignancies. The aim of the present study was to examine the possible importance of 2 VEGF polymorphisms and VEGF-A expression in ovarian cancer. Methods: We investigated 2 single nucleotide polymorphisms VEGF +405G/C and VEGF −460C/T by polymerase chain reaction and also analyzed VEGF-A expression by immunohistochemistry in 159 women with ovarian cancer. Results: Vascular endothelial growth factor-A expression revealed a significant correlation with survival in a Cox proportional hazards regression model (P = 0.012). Germline polymorphisms were not correlated with clinicopathological parameters such as stage, type, and histology. Heterozygous genotype in VEGF +405G/C predicted a better survival compared with homozygous genotypes (P = 0.034), and the heterozygous genotype in VEGF −460C/T pointed to the same direction. A multivariate analysis also indicated that heterozygosity of either of the 2 polymorphisms held independent prognostic significance (P = 0.001). Conclusions: Vascular endothelial growth factor polymorphisms +405G/C and VEGF expression seem to have independent prognostic importance.

Improved classification of epithelial ovarian cancer: results of 3 danish cohorts

Objective An increasing body of evidence has suggested that epithelial ovarian cancer (EOC) patients can broadly be divided into 2 groups on the basis of histopathologic parameters and molecular profiles. Type 1 tumors are slow-growing tumors with inherent mutations such as KRAS or BRAF mutations, whereas type 2 tumors are more rapidly growing tumors of which many contain TP53 mutations. In the present study, we performed a comprehensive study in a large Danish material to evaluate the clinical importance. Materials and Methods A total of 512 tissue samples were included (430 EOCs, 34 borderline, 28 benign tumors, and 20 normal ovaries). KRAS mutations (codon 12/13) and BRAF codon 600 mutations were analyzed from formalin-fixed paraffin-embedded tissue by ARMS qPCR. p53 expression was examined by immunohistochemistry. Results Of the EOC patients, 25% had histopathologically classified type 1 tumors, and of these, 44% were either KRAS or BRAF mutated. Of patients with histopathologic type 2 tumors, 66% showed p53 protein overexpression, whereas 4 (1.5%) patients contained a KRAS mutation. In a univariate survival analysis, a large difference in survival was seen between patients with type 1 and type 2 tumors. Patients with type histologic 2 tumors had significantly worse survival compared with patients with type 1 tumors (P < 10−5). International Federation of Gynecology and Obstetrics (FIGO) stage, tumor grade, residual tumor, and KRAS/BRAF mutation were independent predictors of overall survival in the multivariate analysis. Patients with KRAS/BRAF mutated carcinomas showed independent decreased overall survival with a hazard ratio of 2.01 (95% confidence interval, 1.13–3.57; P = 0.018). Conclusions KRAS/BRAF mutations are with very few exceptions constrained to patients with histopathologic type 1 tumors, whereas p53 overexpression is very frequent in type 2 tumors. KRAS/BRAF mutations had independent prognostic importance. The classification presented here should have a major therapeutic implication and serve as a hallmark of future clinical trials.

Mutant epidermal growth factor receptor in benign, borderline, and malignant ovarian tumors.

Purpose: Dysfunction of the epidermal growth factor (EGF) complex is essential to the growth and development of many human tumors. Overexpression of the EGF receptor (EGFR) is a characteristic finding in a considerable number of solid tumors and often signalizes poor prognosis. There is a major disagreement among researchers about both the frequency and possible clinical importance of EGFR overexpression in ovarian cancer. The type III variant of EGFR (EGFRvIII) is a mutant with a deletion. Contrary to the wild-type, it is constitutively active. EGFRvIII has not been found in normal tissue, and consequently, it is an attractive tumor-specific candidate for molecular targeted treatment. The literature dealing with this mutation in ovarian cancer has been very sparse. Experimental Design: Tissue from 225 patients who underwent surgery for a pelvic mass was collected consecutively. The samples included 99 ovarian/peritoneal/tuba cancers, 17 ovarian borderline tumors, 66 benign ovarian tumors, 15 other cancer types, 24 normal ovarian biopsies, and 4 miscellaneous. The presence of EGFRvIII was investigated both by PCR analyses for EGFRvIII gene expression and with protein analysis by Western blots. Results: None of the tissue samples was positive for the EGFRvIII mutation neither at the mRNA level nor at the protein level. Conclusions: The EGFRvIII mutation seems to be very rare in ovarian tissue. Our data indicate that EGFRvIII is not a part of the malignant phenotype in ovarian cancer and should not be pursued as a therapeutic target for treatment of this disease.