Ovarian cancer cells regulate their mitochondrial content and high mitochondrial content is associated with a poor prognosis.

Most cancer patients ultimately die from the consequences of distant metastases. As metastasis formation consumes energy mitochondria play an important role during this process as they are the most important cellular organelle to synthesise the energy rich substrate ATP, which provides the necessary energy to enable distant metastasis formation. However, mitochondria are also important for the execution of apoptosis, a process which limits metastasis formation. We therefore wanted to investigate the mitochondrial content in ovarian cancer cells and link its presence to the patient's prognosis in order to analyse which of the two opposing functions of mitochondria dominates during the malignant progression of ovarian cancer. Monoclonal antibodies directed against different mitochondrial specific proteins, namely heat shock proteins 60 (HSP60), fumarase and succinic dehydrogenase, were used in immunohistochemistry in preliminary experiments to identify the antibody most suited to detect mitochondria in ovarian cancer cells in clinical tissue samples. The clearest staining pattern, which even delineated individual mitochondria, was seen with the anti-HSP60 antibody, which was used for the subsequent clinical study staining primary ovarian cancers (n = 155), borderline tumours (n = 24) and recurrent ovarian cancers (n = 26). The staining results were semi-quantitatively scored into three groups according to their mitochondrial content: low (n = 26), intermediate (n = 50) and high (n = 84). Survival analysis showed that high mitochondrial content correlated with a statistically significant overall reduced survival rate In addition to the clinical tissue samples, mitochondrial content was analysed in ovarian cancer cells grown in vitro (cell lines: OVCAR8, SKOV3, OVCAR3 and COV644) and in vivo in severe combined immunodeficiency (SCID) mice.In in vivo grown SKOV3 and OVCAR8 cells, the number of mitochondria positive cells was markedly down-regulated compared to the in vitro grown cells indicating that mitochondrial number is subject to regulatory processes. As high mitochondrial content is associated with a poor prognosis, the provision of high energy substrates by the mitochondria seems to be more important for metastasis formation than the inhibition of apoptotic cell death, which is also mediated by mitochondria. In vivo and in vitro grown human ovarian cancer cells showed that the mitochondrial content is highly adaptable to the growth condition of the cancer cells.

Tumor cell integrin ß4 and tumor stroma E-/P-selectin cooperatively regulate tumor growth in vivo.

BACKGROUND: The immunological composition of the tumor microenvironment has a decisive influence on the biological course of cancer and is therefore of profound clinical relevance. In this study, we analyzed the cooperative effects of integrin ß4 (ITGB4) on tumor cells and E-/P-selectin on endothelial cells within the tumor stroma for regulating tumor growth by shaping the local and systemic immune environment. METHODS: We used several preclinical mouse models for different solid human cancer types (xenograft and syngeneic) to explore the role of ITGB4 (shRNA-mediated knockdown in tumor cells) and E-/P-selectins (knockout in mice) for tumor growth; effects on apoptosis, proliferation and intratumoral signaling pathways were determined by histological and biochemical methods and 3D in vitro experiments; changes in the intratumoral and systemic immune cell composition were determined by flow cytometry and immunohistochemistry; chemokine levels and their attracting potential were measured by ELISA and 3D invasion assays. RESULTS: We observed a very robust synergism between ITGB4 and E-/P-selectin for the regulation of tumor growth, accompanied by an increased recruitment of CD11b+ Gr-1Hi cells with low granularity (i.e., myeloid-derived suppressor cells, MDSCs) specifically into ITGB4-depleted tumors. ITGB4-depleted tumors undergo apoptosis and actively attract MDSCs, well-known to promote tumor growth in several cancers, via increased secretion of different chemokines. MDSC trafficking into tumors crucially depends on E-/P-selectin expression. Analyses of clinical samples confirmed an inverse relationship between ITGB4 expression in tumors and number of tumor-infiltrating leukocytes. CONCLUSIONS: These findings suggest a distinct vulnerability of ITGB4Lo tumors for MDSC-directed immunotherapies.

The role of the desmosomal protein desmocollin 2 in tumour progression in triple negative breast cancer patients.

BACKGROUND: The disruption of epithelial features represents a critical step during breast cancer spread. In this context, the dysregulation of desmosomal proteins has been associated with malignant progression and metastasis formation. Curiously, both tumour suppressive and pro-metastatic roles have been attributed to desmosomal structures in different cancer entities. In the present study, we describe the pro-metastatic role of the desmosomal protein desmocollin 2 (DSC2) in breast cancer. METHODS: We analysed the prognostic role of DSC2 at mRNA and protein level using microarray data, western blot analysis and immunohistochemistry. Functional consequences of DSC2 overexpression and DSC2 knock down were investigated in the triple negative breast cancer (TNBC) cell line MDA-MB-231 and its brain-seeking subline MDA-MB-231-BR, respectively in vitro and in vivo. RESULTS: We found a significantly higher DSC2 expression in the more aggressive molecular subtypes HER2-positive and TNBC than in luminal breast cancers, as well as a significant correlation between increased DSC2 expression and a shorter disease-free-also in multivariate analysis-and overall survival. Additionally, a significant association between DSC2 expression in the primary tumour and an increased frequency of cerebral and lung metastasis could be observed. In vitro, ectopic DSC2 expression or DSC2 down-regulation in MDA-MB-231 and MDA-MB-231-BR led to a significant tumour cell aggregation increase and decrease, respectively. Furthermore, tumour cells displaying higher DSC2 levels showed increased chemoresistance in 3D structures, but not 2D monolayer structures, suggesting the importance of cell aggregation as a means for reduced drug diffusion. In an in vivo brain dissemination xenograft mouse model, reduced expression of DSC2 in the brain-seeking TNBC cells led to a decreased amount of circulating tumour cells/clusters and, in turn, to fewer and smaller brain metastatic lesions. CONCLUSION: We conclude that high DSC2 expression in primary TNBC is associated with a poorer prognosis, firstly by increasing tumour cell aggregation, secondly by reducing the diffusion and effectiveness of chemotherapeutic agents, and, lastly, by promoting the circulation and survival of tumour cell clusters, each of which facilitates distant organ colonisation.

Ovarian Cancer-Cell Pericellular Hyaluronan Deposition Negatively Impacts Prognosis of Ovarian Cancer Patients.

BACKGROUND: Hyaluronan (HA), a component of the extracellular matrix, is frequently increased under pathological conditions including cancer. Not only stroma cells but also cancer cells themselves synthesize HA, and the interaction of HA with its cognate receptors promotes malignant progression and metastasis. METHODS: In the present study, HA deposition in tissue sections was analyzed by hyaluronan-binding protein (HABP) ligand histochemistry in 17 borderline tumors and 102 primary and 20 recurrent ovarian cancer samples. The intensity and, particularly, localization of the HA deposition were recorded: for the localization, the pericellular deposition around the ovarian cancer cells was distinguished from the deposition within the stromal compartment. These histochemical data were correlated with clinical and pathological parameters. Additionally, within a reduced subgroup of ovarian cancer samples (n = 70), the RNA levels of several HA-associated genes were correlated with the HA localization and intensity. RESULTS: Both stroma-localized and pericellular tumor-cell-associated HA deposition were observed. Cancer-cell pericellular HA deposition, irrespective of its staining intensity, was significantly associated with malignancy, and in the primary ovarian cancer cohort, it represents an independent unfavorable prognostic marker for overall survival. Furthermore, a significant association between high CD44, HAS2 and HAS3 mRNA levels and a cancer-cell pericellular HA-deposition pattern was noted. In contrast, stromal hyaluronan deposition had no impact on ovarian cancer prognosis. CONCLUSIONS: In conclusion, the site of HA deposition is of prognostic value, but the amount deposited is not. The significant association of only peritumoral cancer-cell HA deposition with high CD44 mRNA expression levels suggests a pivotal role of the CD44-HA signaling axis for malignant progression in ovarian cancer.

Key Role of Hyaluronan Metabolism for the Development of Brain Metastases in Triple-Negative Breast Cancer.

Breast cancer (BC) is the second-most common cause of brain metastases (BM) and BCBM patients have a reduced quality of life and a poor prognosis. Hyaluronan (HA), and in particular the hyaluronidase Hyal-1, has been already linked to the development of BCBM, and therefore presents an interesting opportunity to develop new effective therapeutic options. HA metabolism was further discovered by the CRISPR/Cas9-mediated knockout of HYAL1 and the shRNA-mediated down-regulation of HA-receptor CD44 in the brain-seeking triple-negative breast cancer (TNBC) cell line MDA-MB-231-BR. Therefore, the impact of Hyal-1 on adhesion, disruption, and invasion through the brain endothelium, both in vitro and in vivo, was studied. Our analysis points out a key role of Hyal-1 and low-molecular-weight HA (LMW-HA) in the formation of a pericellular HA-coat in BC cells, which in turn promotes tumor cell adhesion, disruption, and migration through the brain endothelium in vitro as well as the extent of BM in vivo. CD44 knockdown in MDA-MB-231-BR significantly reduced the pericellular HA-coat on these cells, and, consequently, tumor cell adhesion and invasion through the brain endothelium. Thus, the interaction between Hyal-1-generated LMW-HA fragments and the HA-receptor CD44 might represent a potential target for future therapeutic options in BC patients with a high risk of cerebral metastases formation.

Insights into the Steps of Breast Cancer-Brain Metastases Development: Tumor Cell Interactions with the Blood-Brain Barrier.

Brain metastases (BM) represent a growing problem for breast cancer (BC) patients. Recent studies have demonstrated a strong impact of the BC molecular subtype on the incidence of BM development. This study explores the interaction between BC cells of different molecular subtypes and the blood-brain barrier (BBB). We compared the ability of BC cells of different molecular subtypes to overcome several steps (adhesion to the brain endothelium, disruption of the BBB, and invasion through the endothelial layer) during cerebral metastases formation, in vitro as well as in vivo. Further, the impact of these cells on the BBB was deciphered at the molecular level by transcriptome analysis of the triple-negative (TNBC) cells themselves as well as of hBMECs after cocultivation with BC cell secretomes. Compared to luminal BC cells, TNBC cells have a greater ability to influence the BBB in vitro and consequently develop BM in vivo. The brain-seeking subline and parental TNBC cells behaved similarly in terms of adhesion, whereas the first showed a stronger impact on the brain endothelium integrity and increased invasive ability. The comparative transcriptome revealed potential brain-metastatic-specific key regulators involved in the aforementioned processes, e.g., the angiogenesis-related factors TNXIP and CXCL1. In addition, the transcriptomes of the two TNBC cell lines strongly differed in certain angiogenesis-associated factors and in several genes related to cell migration and invasion. Based on the present study, we hypothesize that the tumor cell's ability to disrupt the BBB via angiogenesis activation, together with increased cellular motility, is required for BC cells to overcome the BBB and develop brain metastases.

Tumor cell E-selectin ligands determine partialefficacy of bortezomib on spontaneous lung metastasis formation of solid human tumors in vivo.

Extravasation of circulating tumor cells (CTCs) is critical for metastasis and is initiated by adhesive interactions between glycoligands on CTCs and E-selectin on endothelia. Here, we show that the clinically approved proteasome inhibitor bortezomib (BZM; Velcade) counteracts the cytokine-dependent induction of E-selectin in the lung mediated by the primary tumor, thereby impairing endothelial adhesion and thus spontaneous lung metastasis in vivo. However, the efficacy of BZM crucially depends on the tumor cells' E-selectin ligands, which determine distinct adhesion patterns. The canonical ligands sialyl-Lewis A (sLeA) and sLeX mediate particularly high-affinity E-selectin binding so that the incomplete E-selectin-reducing effect of BZM is not sufficient to disrupt adhesion or metastasis. In contrast, tumor cells lacking sLeA/X nevertheless bind E-selectin, but with low affinity, so that adhesion and lung metastasis are significantly diminished. Such low-affinity E-selectin ligands apparently consist of sialylated MGAT5 products on CD44. BZM no longer has anti-metastatic activity after CD44 knockdown in sLeA/X-negative tumor cells or E-selectin knockout in mice. sLeA/X can be determined by immunohistochemistry in cancer samples, which might aid patient stratification. These data suggest that BZM might act as a drug for inhibiting extravasation and thus distant metastasis formation in malignancies expressing low-affinity E-selectin ligands.

Fra-2 overexpression upregulates pro-metastatic cell-adhesion molecules, promotes pulmonary metastasis, and reduces survival in a spontaneous xenograft model of human breast cancer.

PURPOSE: The transcription factor Fra-2 affects the invasive potential of breast cancer cells by dysregulating adhesion molecules in vitro. Previous results suggested that it upregulates the expression of E- and P-selectin ligands. Such selectin ligands are important members of the leukocyte adhesion cascade, which govern the adhesion and transmigration of cancer cells into the stroma of the host organ of metastasis. As so far, no in vivo data are available, this study was designed to elucidate the role of Fra-2 expression in a spontaneous breast cancer metastasis xenograft model. METHODS: The effect of Fra-2 overexpression in two stable Fra-2 overexpressing clones of the human breast cancer cell line MDA MB231 on survival and metastatic load was studied after subcutaneous injection into scid and E- and P-selectin-deficient scid mice. RESULTS: Fra-2 overexpression leads to a significantly shorter overall survival and a higher amount of spontaneous lung metastases not only in scid mice, but also in E- and P-deficient mice, indicating that it regulates not only selectin ligands, but also selectin-independent adhesion processes. CONCLUSION: Thus, Fra-2 expression influences the metastatic potential of breast cancer cells by changing the expression of adhesion molecules, resulting in increased adherence to endothelial cells in a breast cancer xenograft model.

TGFB-induced factor homeobox 1 (TGIF) expression in breast cancer.

BACKGROUND: Breast cancer (BC) is the most frequent female cancer and preferentially metastasizes to bone. The transcription factor TGFB-induced factor homeobox 1 (TGIF) is involved in bone metabolism. However, it is not yet known whether TGIF is associated with BC bone metastasis or patient outcome and thus of potential interest. METHODS: TGIF expression was analyzed by immunohistochemistry in 1197 formalin-fixed, paraffin-embedded tissue samples from BC patients treated in the GAIN (German Adjuvant Intergroup Node-Positive) study with two adjuvant dose-dense schedules of chemotherapy with or without bisphosphonate ibandronate. TGIF expression was categorized into negative/low and moderate/strong staining. Endpoints were disease-free survival (DFS), overall survival (OS) and time to primary bone metastasis as first site of relapse (TTPBM). RESULTS: We found associations of higher TGIF protein expression with smaller tumor size (p = 0.015), well differentiated phenotype (p < 0.001) and estrogen receptor (ER)-positive BC (p < 0.001). Patients with higher TGIF expression levels showed a significantly longer disease-free (DFS: HR 0.75 [95%CI 0.59-0.95], log-rank p = 0.019) and overall survival (OS: HR 0.69 [95%CI 0.50-0.94], log-rank p = 0.019), but no association with TTPBM (HR 0.77 [95%CI 0.51-1.16]; p = 0.213). Univariate analysis in molecular subgroups emphasized that elevated TGIF expression was prognostic for both DFS and OS in ER-positive BC patients (DFS: HR 0.68 [95%CI 0.51-0.91]; log-rank p = 0.009, interaction p = 0.130; OS: HR 0.60 [95%CI 0.41-0.88], log-rank p = 0.008, interaction p = 0.107) and in the HER2-negative subgroup (DFS:HR 0.67 [95%CI 0.50-0.88], log-rank p = 0.004, interaction p = 0.034; OS: HR 0.57 [95%CI 0.40-0.81], log-rank p = 0.002, interaction p = 0.015). CONCLUSIONS: Our results suggest that moderate to high TGIF expression is a common feature of breast cancer cells and that this is not associated with bone metastases as first site of relapse. However, a reduced expression is linked to tumor progression, especially in HER2-negative breast cancer. TRIAL REGISTRATION: This clinical trial has been registered with ClinicalTrials.gov ; registration number: NCT00196872 .

Molecular characteristics and tumorigenicity of ascites-derived tumor cells: mitochondrial oxidative phosphorylation as a novel therapy target in ovarian cancer.

Ovarian cancer disseminates primarily intraperitoneally. Detached tumor cell aggregates (spheroids) from the primary tumor are regarded as 'metastatic units' that exhibit a low sensitivity to classical chemotherapy, probably due to their unique molecular characteristics. We have analyzed the cellular composition of ascites from OvCa patients, using flow cytometry, and studied their behavior in vitro and in vivo. We conclude that ascites-derived cultured cells from OvCa patients give rise to two subpopulations: adherent cells and non-adherent cells. Here, we found that the AD population includes mainly CD90+ cells with highly proliferative rates in vitro but no tumorigenic potential in vivo, whereas the NAD population contains principally tumor cell spheroids (EpCAM+ /CD24+ ) with low proliferative potential in vitro. Enriched tumor cell spheroids from the ascites of high-grade serous OvCA patients, obtained using cell strainers, were highly tumorigenic in vivo and their metastatic spread pattern precisely resembled the tumor dissemination pattern found in the corresponding patients. Comparative transcriptome analyses from ascites-derived tumor cell spheroids (n = 10) versus tumor samples from different metastatic sites (n = 30) revealed upregulation of genes involved in chemoresistance (TGM1, HSPAs, MT1s), cell adhesion and cell-barrier integrity (PKP3, CLDNs, PPL), and the oxidative phosphorylation process. Mitochondrial markers (mass and membrane potential) showed a reduced mitochondrial function in tumoroids from tumor tissue compared with ascites-derived tumor spheroids in flow cytometry analysis. Interestingly, response to OXPHOS inhibition by metformin and IACS010759 in tumor spheroids correlated with the extent of mitochondrial membrane potential measured by fluorescence-activated cell sorting. Our data contribute to a better understanding of the biology of ovarian cancer spheroids and identify the OXPHOS pathway as new potential treatment option in advanced ovarian cancer.

Spatially correlated phenotyping reveals K5-positive luminal progenitor cells and p63-K5/14-positive stem cell-like cells in human breast epithelium.

Understanding the mechanisms regulating human mammary epithelium requires knowledge of the cellular constituents of this tissue. Different and partially contradictory definitions and concepts describing the cellular hierarchy of mammary epithelium have been proposed, including our studies of keratins K5 and/or K14 as markers of progenitor cells. Furthermore, we and others have suggested that the p53 homolog p63 is a marker of human breast epithelial stem cells. In this investigation, we expand our previous studies by testing whether immunohistochemical staining with monospecific anti-keratin antibodies in combination with an antibody against the stem cell marker p63 might help refine the different morphologic phenotypes in normal breast epithelium. We used in situ multilabel staining for p63, different keratins, the myoepithelial marker smooth muscle actin (SMA), the estrogen receptor (ER), and Ki67 to dissect and quantify the cellular components of 16 normal pre- and postmenopausal human breast epithelial tissue samples at the single-cell level. Importantly, we confirm the existence of K5+ only cells and suggest that they, in contrast to the current view, are key luminal precursor cells from which K8/18+ progeny cells evolve. These cells are further modified by the expression of ER and Ki67. We have also identified a population of p63+K5+ cells that are only found in nipple ducts. Based on our findings, we propose a new concept of the cellular hierarchy of human breast epithelium, including K5 luminal lineage progenitors throughout the ductal-lobular axis and p63+K5+ progenitors confined to the nipple ducts.

Selectin-independent adhesion during ovarian cancer metastasis.

PURPOSE: Ovarian cancer (OvCa) progression mainly takes place by intraperitoneal spread. Adhesion of tumor cells to the mesothelial cells which form the inner surface of the peritoneum is a crucial step in this process. Cancer cells use in principle different molecules of the leukocyte adhesion cascade to facilitate adhesion. This cascade is initiated by selectin-ligand interactions followed by integrin - extracellular matrix protein interactions. Here we address the question whether all tumor cells predominantly employ selectin-dependent leukocyte-like adhesion cascade (SDAC) or whether they use integrin mediated adhesion for OvCa progression as well. METHODS: A comparative transcriptomic analysis of the human OvCa cell lines OVCAR8 and SKOV3 was performed. Intraperitoneal xenograft model of OVCAR8 cells was used to determine whether there is a correlation between SDAC gene expression and the metastatic potential of the control cells and the cells overexpressing c-Fos. Transcriptomic analysis of OVCAR8 and SKOV3 samples was performed using microarrays. RESULTS: One-third of the protein-coding genes involved in SDAC exhibited lower expression levels in OVCAR8 than in SKOV3 cells. In contrast to SKOV3 cells, c-Fos overexpression in OVCAR8 cells did not significantly influence the expression of SDAC genes. Intraperitoneal xenograft model of OVCAR8 cells unexpectedly demonstrated that the aggressiveness of OVCAR8 tumors was not depended on the c-Fos expression level and was comparable to that of SKOV3 control tumors. Gene expression analysis of tumors suggests that SKOV3-derived tumor progression was mainly depended on SDAC. Progression of OVCAR8 tumors relied on other cell adhesion molecules that do not interact with selectins. CONCLUSIONS: High expression of c-Fos in ovarian cancer cells is not always associated with reduced metastatic potential. Low expression level of SDAC genes may not ensure low OvCa metastatic potential hence alternative adhesion mechanisms involving laminin-integrin interactions exist as well.

Role of HYAL1 expression in primary breast cancer in the formation of brain metastases.

BACKGROUND: The incidence of brain metastases in breast cancer patients has increased in the last years. However, the knowledge about tumor cell invasion in the brain is still very limited. Based on our recent study on cDNA microarray data of breast cancer patients, we hypothesized that two enzymes involved in the hyaluronan metabolism, namely, hyaluronan synthase 2 (HAS2) and hyaluronidase 1 (HYAL1) are associated with brain metastases formation. METHODS: Protein expression levels of hyaluronan, HAS2, and HYAL1 were analyzed in primary breast cancer, and metastatic tissue samples from different localizations (brain, bone, skin, liver, and lung) were included in four different cohorts by immunohistochemistry. Correlations of expression levels with clinical and pathological parameters were performed within the individual cohorts. RESULTS: Higher HYAL1 expression was detected among primary tumors from patients with subsequent brain metastases compared with those without brain metastases (p = 0.011). Interestingly, brain metastatic tissue showed a significantly reduced HYAL1 expression compared with the corresponding primary tumor (p = 0.003). HYAL1 expression in brain metastases was also significantly lower than in skin, liver, and lung metastases. Further, hyaluronan staining in brain metastases was mainly located on the surface of the tumor cells, whereas in all other metastatic sites hyaluronan was only detected in the extracellular matrix. We could not show an association of HAS2 with the formation of brain metastases. CONCLUSIONS: In conclusion, our results suggest that the enzyme HYAL1 plays a role in tumor dissemination and brain-specific colonization, rather than in subsequent metastatic out-growth.