Hannelore Denys

Effect of the Secretory Small GTPase Rab27B on Breast Cancer Growth, Invasion, and Metastasis

BACKGROUND Secretory GTPases like Rab27B control vesicle exocytosis and deliver critical proinvasive growth regulators into the tumor microenvironment. The expression and role of Rab27B in breast cancer were unknown. METHODS Expression of green fluorescent protein (GFP) fused with wild-type Rab3D, Rab27A, or Rab27B, or Rab27B point mutants defective in GTP/GDP binding or geranylgeranylation, or transient silencing RNA to the same proteins was used to study Rab27B in estrogen receptor (ER)-positive human breast cancer cell lines (MCF-7, T47D, and ZR75.1). Cell cycle progression was evaluated by flow cytometry, western blotting, and measurement of cell proliferation rates, and invasion was assessed using Matrigel and native type I collagen substrates. Orthotopic tumor growth, local invasion, and metastasis were analyzed in mouse xenograft models. Mass spectrometry identified proinvasive growth regulators that were secreted in the presence of Rab27B. Rab27B protein levels were evaluated by immunohistochemistry in 59 clinical breast cancer specimens, and Rab3D, Rab27A, and Rab27B mRNA levels were analyzed by quantitative real-time polymerase chain reaction in 20 specimens. Statistical tests were two-sided. RESULTS Increased expression of Rab27B promoted G(1) to S phase cell cycle transition, proliferation and invasiveness of cells in culture, and invasive tumor growth and hemorrhagic ascites production in a xenograft mouse model (n = 10; at 10 weeks, survival of MCF-7 GFP- vs GFP-Rab27B-injected mice was 100% vs 62.5%, hazard ratio = 0.26, 95% confidence interval = 0.08 to 0.88, P = .03). Mass spectrometric analysis of purified Rab27B-secretory vesicles identified heat-shock protein 90alpha as key proinvasive growth regulator. Heat-shock protein 90alpha secretion was Rab27B-dependent and was required for matrix metalloproteinase-2 activation. All Rab27B-mediated functional responses were GTP- and geranylgeranyl-dependent. Presence of endogenous Rab27B mRNA and protein, but not of Rab3D or Rab27A mRNA, was associated with lymph node metastasis (P < .001) and differentiation grade (P = .001) in ER-positive human breast tumors. CONCLUSIONS Rab27B regulates invasive growth and metastasis in ER-positive breast cancer cell lines, and increased expression is associated with poor prognosis in humans.

Bone marrow-derived mesenchymal stem cells promote colorectal cancer progression through paracrine neuregulin 1/HER3 signalling

Objective Bone marrow-derived mesenchymal stem cells (BM-MSC) migrate to primary tumours and drive tumour progression. This study aimed to identify the molecular mechanisms associated with these heterotypic cellular interactions and analyse their relevance in colorectal cancer (CRC). Design Paracrine interactions of BM-MSC with CRC cells were studied using collagen invasion assays, cell counts, flow cytometric cell-cycle analysis and tumour xenograft models. The role of neuregulin 1 (NRG1) and the human epidermal growth factor receptor (HER) family pathways were investigated using tyrosine kinase assays, mass spectrometry, pharmacological inhibition, antibody-mediated neutralisation and RNA interference. Transmembrane neuregulin 1 (tNRG1), HER2 and HER3 expression was analysed in primary CRC (n=54), adjacent normal colorectal tissues (n=4), liver metastases (n=3) and adjacent normal liver tissues (n=3) by immunohistochemistry. Results BM-MSC stimulate invasion, survival and tumorigenesis of CRC through the release of soluble NRG1, activating the HER2/HER3-dependent PI3K/AKT signalling cascade in CRC cells. Similarly, tumour-associated mesenchymal cells (T-MC) in CRC demonstrate high tNRG1 expression, which is significantly associated with advanced Union for International Cancer Control stage (p=0.005) and invasion depth (p=0.04) and decreased 5-year progression-free survival (p=0.01). HER2 and HER3 show membrane localisation in cancer cells of CRC tissue. Conclusion Paracrine NRG1/HER3 signals initiated by BM-MSC and T-MC promote CRC cell progression, and high tNRG1 expression is associated with poor prognosis in CRC.

Differential impact of TGF-β and EGF on fibroblast differentiation and invasion reciprocally promotes colon cancer cell invasion

Several studies indicate that cancer-associated fibroblasts play a critical role in cancer cell invasion and metastasis, the hallmarks of malignancy. To better understand the mechanisms underlying such effects, we established a heterotypic model of human fibroblasts (primary colon fibroblasts and immortalized human dermal fibroblasts) in co-culture with human colon cancer cells (HCT-8/E11), using three-dimensional collagen type-I and Matrigel matrices. We report that TGF-beta is the unique and dominant factor to provide pro-invasive signals to HCT-8/E11 colon cancer cells from TGF-beta-treated human fibroblasts in three-dimensional collagen type I and Matrigel matrices. These effects are not mimicked or reversed by EGF or bFGF, and are associated with the TGF-beta-mediated induction of myofibroblast differentiation and functional markers, such as alpha-SMA, the haptotactic matrix molecule TNC, collagen type 1 maturation enzyme P4H, serine protease FAP, and myofibroblast contractility. Accordingly, TGF-beta induced a strong activation of RhoA and stress fiber formation in fibroblasts, with no impact on Rac1-GTP levels. In contrast, EGF down-regulated Rho-GTP levels in fibroblasts, giving permissive signals for Rac1 activation, fibroblast polarization, and invasion. Taken together, our data imply that TGF-beta and EGF exert invasive growth-promoting actions in human colon tumors through a differential and cumulative impact on the stromal and cancer cell compartments. Our data predict that inhibitors directed at this reciprocal molecular and cellular crosstalk will have therapeutic applications for targeting the invasive growth of human primary tumors and their metastatic spread.

Use of Tamoxifen Before and During Pregnancy

For premenopausal patients with receptor-positive early breast cancer, administration of tamoxifen for 5 years constitutes the main adjuvant endocrine therapy. During pregnancy, tamoxifen and its metabolites interact with rapidly growing and developing embryonic or fetal tissues. Information about tamoxifen and pregnancy was gathered by searching PubMed. In addition, we had access to the records of the pharmaceutical company AstraZeneca. Because these observations are retrospective and other therapies and diagnostic measures are possible confounders, a causal relationship was not established between tamoxifen treatment and pregnancy outcome. The records from AstraZeneca documented three live births with congenital anomalies and four live births without congenital anomalies related to tamoxifen treatment before pregnancy. Tamoxifen therapy during pregnancy resulted in 16 live births with congenital malformations and a total of 122 live births without malformations. The 122 live births without malformations included 85 patients from a prevention trial that did not record a single anomaly, whereas the AstraZeneca Safety Database alone reported 11 babies with congenital malformations of 44 live births. Additionally, there were: 12 spontaneous abortions, 17 terminations of pregnancy without known fetal defects, six terminations of pregnancy with fetal defects, one stillbirth without fetal defects, two stillbirths with fetal defects, and 57 unknown outcomes. The relatively high frequency of severe congenital abnormalities indicates that reliable birth control during tamoxifen treatment is mandatory. After tamoxifen use, a washout period of 2 months is advisable based on the known half-life of tamoxifen. In case of an inadvertent pregnancy, risks and options should be discussed.

Cancer-associated adipose tissue promotes breast cancer progression by paracrine Oncostatin M and Jak/STAT3 signaling.

Increasing evidence supports the critical roles played by adipose tissue in breast cancer progression. Yet, the mediators and mechanisms are poorly understood. Here, we show that breast cancer-associated adipose tissue from freshly isolated tumors promotes F-actin remodeling, cellular scattering, invasiveness, and spheroid reorganization of cultured breast cancer cells. A combination of techniques, including transcriptomics, proteomics, and kinomics enabled us to identify paracrine secretion of oncostatin M (OSM) by cancer-associated adipose tissue. Specifically, OSM, expressed by CD45(+) leucocytes in the stromal vascular fraction, induced phosphorylation of STAT3 (pSTAT3-) Y705 and S727 in breast cancer cells and transcription of several STAT3-dependent genes, including S100 family members S100A7, S100A8, and S100A9. Autocrine activation of STAT3 in MCF-7 cells ectopically expressing OSM-induced cellular scattering and peritumoral neovascularization of orthotopic xenografts. Conversely, selective inhibition of OSM by neutralizing antibody and Jak family kinases by tofacitinib inhibited STAT3 signaling, peritumoral angiogenesis, and cellular scattering. Importantly, nuclear staining of pSTAT3-Y705 identified at the tumor invasion front in ductal breast carcinomas correlates with increased lymphovascular invasion. Our work reveals the potential of novel therapeutic strategies targeting the OSM and STAT3 axis in patients with breast cancer harboring nuclear pSTAT3-Y705.

Vacuolar H+ ATPase expression and activity is required for Rab27B-dependent invasive growth and metastasis of breast cancer

The secretory Rab27B small GTPase promotes invasive growth and metastasis in estrogen receptor (ER) α‐positive breast cancer cells by orchestrating the peripheral targeting of vesicles secreting proinvasive growth regulators. Increased Rab27B expression is associated with poor prognosis in breast cancer patients. The molecular mechanisms of peripheral Rab27B secretory vesicle distribution are poorly understood. Mass spectrometry analysis on green fluorescent protein (GFP)‐Rab27B vesicles prepared from GFP‐Rab27B transfected MCF‐7 human breast cancer cells detected eight subunits of the vacuolar H(+)‐ATPase (V‐ATPase) and the presence of V0a1 and V0d1 subunits was confirmed by Western blot analysis. Reversible inhibition of V‐ATPase activity by bafilomycin A1 or transient silencing of V0a1 or V0d1 subunits demonstrated that V‐ATPase controls peripheral localization and size of Rab27B vesicles. V‐ATPase expression and activity further controls Rab27B‐induced collagen type I invasion, cell‐cycle progression and invasive growth in the chorioallantoic membrane assay. In agreement, Rab27B‐dependent extracellular heat shock protein90α release and matrix metalloprotease‐2 activation is markedly reduced by bafilomycin A1 and transient silencing of V0a1 and V0d1 subunits. Poor prognosis ERα‐positive primary breast tumors expressing high levels of Rab27B also expressed multiple V‐ATPase subunits and showed a strong cytoplasmic and peripheral V‐ATPase V1E expression. In conclusion, inhibiting V‐ATPase activity by interfering agents and drugs might be an effective strategy for blocking Rab27B‐dependent proinvasive secretory vesicle trafficking in ERα‐positive breast cancer patients.

PARP INHIBITORS IN ONCOLOGY: A NEW SYNTHETIC LETHAL APPROACH TO CANCER THERAPY

Abstract Damage to DNA has emerged as a major culprit in cancer. Mammalian cells are continuously exposed to DNA damage, caused by exogenous toxins as well as endogenous activities such as DNA replication and cellular free radical generation. It is therefore essential that cells have DNA repair mechanisms in place to preserve its genomic integrity. Interestingly, cancer cells frequently harbour defects in DNA repair pathways, leading to genomic instability. This can foster tumorigenesis, but also provides a weakness in the tumour that can be exploited therapeutically. In this context, it has been shown that homologous recombination (HR)- deficient tumour cells – including those with defects in BRCA1/2 – are highly sensitive to blockade of the base excision repair (BER) pathway via inhibition of the poly (ADPribose) polymerase (PARP) enzyme. This provides the basis for a novel ‘synthetic lethal’ approach to cancer therapy. Recent clinical trials have shown an enhancement of the cytotoxic effect of chemotherapy by adding a PARP inhibitor to the standard treatment. Still, clinical outcome may be even further improved if these drugs would be used as firstline therapy. In conclusion, it can be stated that an exciting new class of drugs has entered the arena of cancer therapy. However, additional clinical studies are needed before PARP inhibitors can definitely enter daily clinical practice.

Colloidal stability of nano-sized particles in the peritoneal fluid: Towards optimizing drug delivery systems for intraperitoneal therapy

Intraperitoneal (IP) administration of nano-sized delivery vehicles containing small interfering RNA (siRNA) has recently gained attention as an alternative route for the efficient treatment of peritoneal carcinomatosis. The colloidal stability of nanomatter following IP administration has, however, not been thoroughly investigated yet. Here, enabled by advanced microscopy methods such as single particle tracking and fluorescence correlation spectroscopy, we follow the aggregation and cargo release of nano-scaled systems directly in peritoneal fluids from healthy mice and ascites fluid from a patient diagnosed with peritoneal carcinomatosis. The colloidal stability in the peritoneal fluids was systematically studied as a function of the charge (positive or negative) and poly(ethylene glycol) (PEG) degree of liposomes and polystyrene nanoparticles, and compared to human serum. Our data demonstrate strong aggregation of cationic and anionic nanoparticles in the peritoneal fluids, while only slight aggregation was observed for the PEGylated ones. PEGylated liposomes, however, lead to a fast and premature release of siRNA cargo in the peritoneal fluids. Based on our observations, we reflect on how to tailor improved delivery systems for IP therapy.

Stromal architecture and periductal decorin are potential prognostic markers for ipsilateral locoregional recurrence in ductal carcinoma in situ of the breast

The incidence of ductal carcinoma in situ (DCIS) has increased since the introduction of screening mammography. Recurrence prediction is still not accurate, and could be improved by identifying additional prognostic markers. Periductal stroma actively participates in early breast cancer progression. Therefore, the aim of this study was to explore the prognostic potential of stromal characteristics in DCIS.

Development and validation of a liquid chromatographic method for the simultaneous determination of four anthracyclines and their respective 13-S-dihydro metabolites in plasma and saliva

A quantitative HPLC method with fluorescence detection has been developed for the simultaneous determination of four anthracyclines (doxorubicin, epirubicin, daunorubicin and idarubicin) and their respective 13-S-dihydro metabolites (doxorubicinol, epirubicinol, daunorubicinol and idarubicinol) in plasma and saliva, using epidaunorubicin as internal standard. A progressive optimization matrix led to a two-step extraction based on a protein precipitation with ethanol followed by a liquid-liquid extraction with dichloromethane after pH adjustment to 8.5. The chromatographic separation was performed in 14min on a C18 column, applying gradient elution with a mixture of 0.1% formic acid in water and 0.1% formic acid in acetonitrile. The analytes were detected and quantified at an excitation and emission wavelength of 480 and 555nm, respectively. Limit of detection (LOD) and lower limit of quantification (LLOQ) were 0.3 or 0.75, and 1 or 2.5ng/mL, respectively. Linearity by means of weighted (1/x) regression was obtained from the LLOQ up to 1000 or 2500ng/mL for the parent drugs and up to 400 or 1000ng/mL for the metabolites. Intra-assay and inter-assay relative standard deviation values were all less than 14% at low, medium and high levels, and below 17% at the LLOQ. Accuracy ranged between 91 and 113% at low, medium and high concentrations and between 83 and 118% at the LLOQ. Absolute recoveries were between 78 and 88% in plasma, and between 70 and 79% in saliva, respectively. Autosampler, benchtop, freeze-thaw and long-term stability samples fulfilled acceptance criteria. This selective method was applied successfully to the analysis of plasma and saliva samples from patients administered epirubicin intravenously.