Cytokeratin 5-Positive Cells Represent a Therapy Resistant subpopulation in Epithelial Ovarian Cancer

Estrogen- and estrogen receptor (ER)-mediated cisplatin chemoresistance in cancer

Cisplatin is a platinum-based chemotherapeutic drug used in the standard treatment of various solid cancers including testicular, bladder, head and neck, cervical and ovarian cancer. Although successful clinical responses are observed in patients following initial cisplatin treatment, resistance to cisplatin ultimately develops in most patients, leading to therapeutic failure. Multiple molecular mechanisms contributing to cisplatin resistance in cancer cells have been identified to date. In this review, we discuss the effect of estrogen, estrogen receptors (ERs) and estrogen-related receptors (ERRs) on cisplatin resistance in various cancer types. We highlight that estrogen treatment or increased expression of ERs or ERRs are generally associated with higher cisplatin resistance in cancer in vitro, mostly due to decreased caspase activity, increased anti-apoptotic protein levels such as BCL-2, higher drug efflux and higher levels of antioxidant enzymes. Targeted inhibition of ERs or estrogen production in combination with cisplatin treatment thus can be a useful strategy to overcome chemoresistance in certain cancer types. Estrogen levels and ER status can also be considered to identify cancer patients with a high potential of therapy response against cisplatin. A better mechanistic understanding of the involvement of estrogen, ERs and ERRs in the development of cisplatin resistance is needed to improve the management of cancer treatment.

Circulating tumor cells: potential markers of minimal residual disease in ovarian cancer? a study of the OVCAD consortium

Purpose

In 75% of ovarian cancer patients the tumor mass is completely eradicated by established surgical and cytotoxic treatment; however, the majority of the tumors recur within 24 months. Here we investigated the role of circulating tumor cells (CTCs) indicating occult tumor load, which remains inaccessible by established diagnostics.

Experimental design

Blood was taken at diagnosis (baseline samples, n = 102) and six months after completion of adjuvant first-line chemotherapy (follow-up samples; n = 78). CTCs were enriched by density gradient centrifugation. A multi-marker immunostaining was established and further complemented by FISH on CTCs and tumor/metastasis tissues using probes for stem-cell like fusion genes MECOM and HHLA1.

Results

CTCs were observed in 26.5% baseline and 7.7% follow-up blood samples at a mean number of 12.4 and 2.8 CTCs per ml blood, respectively. Baseline CTCs indicated a higher risk of death in R0 patients with complete gross resection (univariate: HR 2.158, 95% CI 1.111–4.191, p = 0.023; multivariate: HR 2.720, 95% CI 1.340–5.522, p = 0.006). At follow-up, the presence of CTCs was associated with response to primary treatment as assessed using RECIST criteria. Chromosomal gains at MECOM and HHLA1 loci suggest that the observed cells were cancer cells and reflect pathophysiological decisive chromosomal aberrations of the primary and metastatic tumors.

Conclusions

Our data suggest that CTCs detected by the multi-marker protein panel and/or MECOM/HHLA1 FISH represent minimal residual disease in optimally debulked ovarian cancer patients. The role of CTCs cells especially for clinical therapy stratification of the patients has to be validated in consecutive larger studies applying standardized treatment schemes.

Keratin 5 overexpression is associated with serous ovarian cancer recurrence and chemotherapy resistance

This study investigated the clinical significance of keratin 5 and 6 expression in serous ovarian cancer progression and chemotherapy resistance. KRT5 and KRT6 (KRT6A, KRT6B & KRT6C) gene expression was assessed in publically available serous ovarian cancer data sets, ovarian cancer cell lines and primary serous ovarian cancer cells. Monoclonal antibodies which detect both K5/6 or only K5 were used to assess protein expression in ovarian cancer cell lines and a cohort of high grade serous ovarian carcinomas at surgery (n = 117) and after neoadjuvant chemotherapy (n = 21). Survival analyses showed that high KRT5 mRNA in stage III/IV serous ovarian cancers was significantly associated with reduced progression-free (HR 1.38, P < 0.0001) and overall survival (HR 1.28, P = 0.013) whilst high KRT6 mRNA was only associated with reduced progression-free survival (HR 1.2, P = 0.031). Both high K5/6 (≥ 10%, HR 1.78 95% CI; 1.03−2.65, P = 0.017) and high K5 (≥ 10%, HR 1.90, 95% CI; 1.12−3.19, P = 0.017) were associated with an increased risk of disease recurrence. KRT5 but not KRT6C mRNA expression was increased in chemotherapy resistant primary serous ovarian cancer cells compared to chemotherapy sensitive cells. The proportion of serous ovarian carcinomas with high K5/6 or high K5 immunostaining was significantly increased following neoadjuvant chemotherapy. K5 can be used to predict serous ovarian cancer prognosis and identify cancer cells that are resistant to chemotherapy. Developing strategies to target K5 may therefore improve serous ovarian cancer survival.

Cytokeratin 5/6 expression, prognosis, and association with estrogen receptor α in high-grade serous ovarian carcinoma

High-grade serous ovarian carcinoma remains one of the most lethal malignancies in women. For histopathologic differentiation from mesothelioma cytokeratin, 5/6 immunohistochemistry is widely used. Another preferred marker for differential diagnosis to mesothelioma is estrogen receptor α (ER-α). In this study, we determined the rate of cytokeratin 5/6-positive cells in primary high-grade serous carcinoma. A cohort of 215 patients with high-grade serous ovarian carcinoma was evaluated immunohistochemically for the protein expression of cytokeratin 5/6. Most tumors demonstrated at least partly positive for cytokeratin 5/6 (n=148; 68.3%), showing different staining patterns from scattered stained cells to a diffuse staining, at times with a distinctive tumor-stroma border motif. Sixty-seven (31%) were entirely negative. No correlation of cytokeratin immunoreactivity score (IRS) with conventional staging parameters could be demonstrated. From the different IRS values for cytokeratin 5/6, IRS=12 (n=6; 2.9%) seemed to indicate a worse prognosis, albeit not statistically significant. An association with ER-α expression could not be detected but the combination of cytokeratin 5/6 IRS=12 and ER-α negativity resulted in a significant negative prognostic marker (overall survival: P=.003 and progression-free survival: P<.0001). We substantiate cytokeratin 5/6 protein expression as a frequent feature of high-grade serous ovarian carcinoma with various staining patterns, an important fact for the routine differential diagnosis with mesothelioma. Furthermore, cytokeratin 5/6 in combination with ER-α proved to be a negative prognostic marker, wherefore we suggest further investigation of its biological significance and possible manifestation of a basal differentiation.

Partial Oxygen Pressure Affects the Expression of Prognostic Biomarkers HIF-1 Alpha, Ki67, and CK20 in the Microenvironment of Colorectal Cancer Tissue

Hypoxia is prognostically important in colorectal cancer (CRC) therapy. Partial oxygen pressure (pO₂) is an important parameter of hypoxia. The correlation between pO₂ levels and expression levels of prognostic biomarkers was measured in CRC tissues. Human CRC tissues were collected and pO₂ levels were measured by OxyLite. Three methods for tissue fixation were compared, including formalin, Finefix, and Finefix-plus-microwave. Immunohistochemistry (IHC) staining was conducted by using the avidin-biotin complex technique for detecting the antibodies to hypoxia inducible factor-1 (HIF-1) alpha, cytokeratin 20 (CK20), and cell proliferation factor Ki67. The levels of pO₂ were negatively associated with the size of CRC tissues. Finefix-plus-microwave fixation has the potential to replace formalin. Additionally, microwave treatment improved Finefix performance in tissue fixation and protein preservation. The percentage of positive cells and gray values of HIF-1 alpha, CK20, and Ki67 were associated with CRC development (P < 0.05). The levels of pO₂ were positively related with the gray values of Ki67 and negatively related with the values of HIF-1 alpha and CK20 (P < 0.05). Thus, the levels of microenvironmental pO₂ affect the expression of predictive biomarkers HIF-1 alpha, CK20, and Ki67 in the development of CRC tissues.