Angiogenesis and lymphangiogenesis are downregulated in primary breast cancer

Background:

Angiogenesis and lymphangiogenesis are considered to play key roles in tumour growth, progression and metastasis. However, targeting tumour angiogenesis in clinical trials showed only modest efficacy. We therefore scrutinised the concept of tumour angiogenesis and lymphangiogenesis by analysing the expression of crucial markers involved in these processes in primary breast cancer.

Methods:

We analysed the expression of angiogenic, lymphangiogenic or antiangiogenic factors, their respective receptors and specific markers for endothelial and lymphendothelial cells by quantitative real-time RT-PCR in primary breast cancer and compared the expression profiles to non-cancerous, tumour-adjacent tissues and breast tissues from healthy women.

Results:

We found decreased mRNA amounts of major angiogenic and lymphangiogenic factors in tumour compared to healthy tissues, whereas antiangiogenic factors were upregulated. Concomitantly, angiogenic and lymphangiogenic receptors were downregulated in breast tumours. This antiangiogenic, antilymphangiogenic microenvironment was even more pronounced in aggressive tumours and accompanied by reduced amounts of endothelial and lymphatic endothelial cell markers.

Conclusion:

Primary breast tumours are not a site of highly active angiogenesis and lymphangiogenesis. Selection for tumour cells that survive with minimal vascular supply may account for this observation in clinical apparent tumours.     

Prognostic significance of vascular endothelial cell growth factors -A, -C and -D in breast cancer and their relationship with angio- and lymphangiogenesis

Vascular endothelial cell growth factors (VEGF)-A, -C and -D have potent angio and lymphangiogenic functions in experimental models, although their role in the progression of human breast cancer is unclear. The aims of the current study were to examine the relationship between the expression of the aforementioned growth factors with the angio and lymphangiogenic characteristics of breast cancer, and to assess their suitability as potential prognostic factors. Paraffin-embedded sections of 177 primary invasive breast cancer, with complete clinical follow-up information for 10 years, were stained for VEGF-A, -C, -D, podoplanin and CD34 using standard immunohistochemical approaches. The expression of the growth factors was correlated with clinicopathological criteria and patients' survival. Lymph vessel density (LVD) and microvessel density (MVD) were assessed and correlated with expression of the growth factors. Vascular endothelial cell growth factor-A, -C and -D were highly expressed in 40, 37 and 42% of specimens, respectively. High expression of VEGF-A and - C, but not of -D, was associated with a higher LVD (P=0.013 and P=0.014, respectively), a higher MVD (P<0.001 and P=0.002, respectively), the presence of lymph node metastasis (P<0.001 and P<0.001, respectively), distant metastasis (P=0.010 and P=0.008, respectively) and a shorter Overall Survival (P=0.029 and 0.028, respectively). In conclusion, breast cancers that express high levels of VEGF-A and -C are characterised by a poor prognosis, likely through the induction of angio and lymphangiogenesis. Examination of expression of VEGF-A and -C in breast cancer may be beneficial in the identification of a subset of tumours that have a higher probability of recurrence and metastatic spread.     

Soluble histone H2AX is induced by DNA replication stress and sensitizes cells to undergo apoptosis

Introduction

There have been few studies on lymphangiogenesis in the past due to the lack of specific lymphatic endothelial markers, and lymphatic-specific growth factors. Recently, these limitations have been relieved by the discovery of a small number of potential lymphatic-specific markers. The relationship between lymphangiogenesis and regional or distant metastasis has not previously been investigated in humans. Using these lymphatic markers, it is possible to explore the relationship between lymphangiogenesis and tumour metastasis. This study indirectly quantified lymphangiogenesis by measuring mRNA expression of all seven lymphatic markers described above in breast cancers and correlated these markers with lymphatic involvement and survival. The cDNA from 153 frozen archived breast samples were analysed with Q-PCR for all seven lymphangiogenic markers. This was correlated with various prognostic factors as well as patient survival.

Results

There was significantly greater expression of all 7 markers in malignant compared to benign breast tissue. In addition, there was greater expression in lymph node positive/grade 3 tumours when compared to lymph node negative/grade 1 tumours. In 5 of the markers, there was a greater expression in poor NPI prognostic tumours when compared to favourable prognostic tumours which was not statistically significant. There was no association between recurrence risk and lymphangiogenic marker expression.

Conclusion

In summary, the findings from this study show that lymphangiogenesis, measured by specific lymphatic marker expression, is higher in breast cancers than in normal breast tissue. Secondly, breast cancers which have metastasised to the regional lymphatics show higher expression compared to those which have not, although the individual differences for all five markers were not statistically significant.     

Roles of prostaglandins in tumor-associated lymphangiogenesis with special reference to breast cancer

Lymphangiogenesis (formation of new lymphatic vessels), unlike angiogenesis, has been a lesser-focused field in cancer biology, because of earlier controversy regarding whether lymphatic metastasis occurs via pre-existing or newly formed lymphatics. Recent evidence reveals that peri-tumoral or intra-tumoral lymphangiogenesis is a precursor for lymphatic metastasis in most carcinomas and melanomas. Two major lymphangiogenic factors, vascular endothelial growth factor (VEGF)-C and VEGF-D, are produced by cancer cells or immune cells such as macrophages in the tumor-stroma to promote sprouting of lymphatics from lymphatic endothelial cells (LEC) or LEC precursors (LECP) by binding to their primary (high affinity) receptor VEGF-R3 or secondary receptors VEGF-R2, neuropilin (NRP)2 and α9/β1 integrin. Many other growth factors/receptors such as VEGF-A/VEGF-R2, fibroblast growth factor (FGF)2/FGF-R, platelet-derived growth factor (PDGF)/PDGF-R, hepatocyte growth factor (HGF)/C-Met, angiopoietins (Ang)1, 2/Tie2, and chemokines/ chemokine receptors (CCL21/CCR7, CCL12/CCR4) can also stimulate LEC sprouting directly or indirectly. This review deals with the roles of prostaglandins (PG), in particular PGE2, in cancer-associated lymphangiogenesis, with special emphasis on breast cancer. We show that cyclooxygenase (COX)-2 expression by breast cancer cells or tumor stroma leading to high PGE2 levels in the tumor milieu promotes lymphangiogenesis and lymphatic metastases, resulting from binding of PGE2 to PGE receptors (EP, in particular EP4) on multiple cell types: tumor cells, tumor-infiltrating immune cells, and LEC. EP4 activation on cancer cells and macrophages upregulated VEGF-C/D production to stimulate LEC sprouting. Furthermore, ligation of EP4 with PGE2 on cancer or host cells can initiate a new cascade of molecular events leading to cross-talk between cancer cells and LEC, facilitating lymphangiogenesis and lympho-vascular transport of cancer cells. We make a case for EP4 as a potential therapeutic target for breast cancer.     

Ezrin is key regulator of Src-induced malignant phenotype in three-dimensional environment

The oncogenic tyrosine kinase Src has a role in cancer development, especially by promoting invasive and metastatic behavior. It is, however, unclear which of the Src-regulated signaling cascades induce malignant phenotype in three-dimensional environment. One of Src substrates is ezrin, a cytoskeletal organiser and regulator of signal transduction. Ezrin expression correlates with poor outcome of diverse cancers and is essential in experimental metastatic osteosarcoma. We reconstituted genetically ezrin-deficient cells with wild-type (WT) or phosphorylation-deficient Y477F ezrin together with constitutively active Src. In two-dimensional cultures, Src induced malignant features regardless of the presence or absence of ezrin. In contrast, only WT ezrin-expressing cells grew efficiently in soft agar or in suspension. In Matrigel, only WT ezrin significantly promoted growth and invasion, and was targeted to specific regions on the plasma membrane. WT and Y477F ezrin-expressing cells showed marked differences only when growing or scattering in three-dimensional matrix. Additional experiments showed that Y477-phosphorylated ezrin is also needed for the growth of Src-transformed epithelial cells in three-dimensional matrix. Cells lacking functional ezrin had reduced cyclin D levels and fewer cells in G2+S phase, possibly as a consequence of abnormal mTOR signaling, as ezrin Y477F cells showed lower expression of phosphorylated intermediates downstream of mTOR than WT cells. We conclude that the pathways activated by Src depend on the type of environment and that ezrin is a crucial element of Src-induced malignant features in cells growing inside three-dimensional environment.     

Tumor-derived VEGF-C, but not VEGF-D, promotes sentinel lymph node lymphangiogenesis prior to metastasis in breast cancer patients

Breast cancer usually initially metastases to the sentinel lymph nodes (SLNs). Recent studies have demonstrated that tumor cells induce SLN lymphangiogenesis before metastasis in several malignancies. In addition, tumor-derived VEGF-C or VEGF-D may induce lymphangiogenesis and promote lymph node metastasis. To explore the mechanisms of lymph node metastasis in breast cancer, we investigated whether primary tumors induce SLN lymphangiogenesis before metastasis and determined the function of tumor-derived VEGF-C and VEGF-D in SLN lymphangiogenesis. Expression of VEGF-C and VEGF-D was examined using immunohistochemistry in 63 primary breast tumors. No significant relationships between VEGF-C and VEGF-D (P = 0.420), and VEGF-C or VEGF-D expression and clinical parameters (age, tumor size, grade, hormonal receptor status, her-2 status) were observed (P > 0.05). Expression of the lymphatic-specific markers VEGFR-3, Prox-1 and LYVE-1 was measured using quantitative real-time RT-PCR in uninvolved SLNs from 63 patients and compared to control lymph nodes from patients with benign breast disease. Expression of Prox-1 and LYVE-1 mRNA was significantly higher in uninvolved SLNs from breast cancer patients than that in control lymph nodes (P < 0.01). Interestingly, expression of VEGFR-3, Prox-1 and LYVE-1 was significantly higher in SLNs from patients with high VEGF-C-expressing tumors than low VEGF-C-expressing tumors (P < 0.05), but not VEGF-D-high-expressing tumors (P > 0.05). This study demonstrates that primary breast tumors induce SLN lymphangiogenesis before metastasis occurs and that tumor-derived VEGF-C, but not VEGF-D, plays an important role in SLN lymphangiogenesis in breast cancer.     

Increase in ezrin expression from benign to malignant breast tumours

Purpose

Ezrin is known to be involved in intercellular interactions, and a shift from membrane-bound to cytoplasmatic protein expression has been associated with malignant potential. This association has primarily been demonstrated in cell lines and, as yet, little is known about the distribution of ezrin in primary benign and malignant breast tissues. We have, therefore, set out to investigate ezrin protein expression in a series of primary breast lesions.

Methods

Immunohistochemistry was used to detect ezrin expression in 465 samples of normal breast tissues, benign breast tumours, pre-invasive breast lesions, breast cancer tissues and metastatic lymph nodes, and the protein expression patterns observed were correlated with clinicopathological parameters.

Results

Ezrin was detected in the cytoplasm of both benign and malignant breast tissues, but its expression was significantly higher in the malignant tissues (13 % vs 60 %, p?<?0.0001; χ ² test). We also detected a statistically significant higher ezrin expression in pre-invasive lesions compared to benign lesions (15 % vs 44 %, p?=?0.04; χ ² test). We did not find such a difference in ezrin expression between pre-invasive and invasive cancer samples, nor between invasive cancer samples and lymph node metastases. Within the group of invasive cancer samples, we found a significant correlation between ezrin expression and CK14 (rs:0.38, p?<?0.007) and Her2 (rs:0.25, p?<?0.002) expression. No such correlation was observed between ezrin expression and nodal status, grading, patient’s age, hormone receptor status, and Ki67 or p53 expression.

Conclusion

Taken together, we found that cytoplasmatic ezrin expression increases from benign to malignant breast tumour development. We hypothesize that the tissue architectural alterations that are associated with aberrant ezrin expression may point at pathophysiological mechanisms that may be instrumental for the design of novel therapies.     

Src: a potential target for the treatment of triple-negative breast cancer

BackgroundTriple-negative breast cancers lack expression of estrogen and progesterone receptors and overexpression of human epidermal growth factor receptor 2 (HER2). Unlike other subgroups of patients with breast cancer, targeted therapy is currently unavailable for these patients. The aim of this study was to investigate v-src sarcoma viral oncogene homolog (Src) as a potential target for the treatment of triple-negative breast cancer.MethodsExpression of Src was measured in 87 triple-negative and 93 non-triple-negative breast cancers. Dasatinib (an inhibitor of Src) was tested in a panel of breast cancer cell lines.ResultsCytoplasmic expression of Src was detected in 83 (95%) triple-negative samples versus 78 (84%) non-triple-negative samples (P = 0.012), while membrane Src was detected in 78% triple-negative compared with 38% of non-triple-negative specimens (P < 0.0001). Dasatinib inhibited growth in three of five triple-negative cell lines (IC₅₀ < 1 μM). Dasatinib combined with cisplatin was synergistic in the three dasatinib-sensitive cell lines (combination index < 0.9). Dasatinib, in combination with 5′-deoxy-5′-fluoruridine, displayed synergy or additivity. Moderate synergy was observed with docetaxel (Taxotere) in two cell lines but the combination was antagonistic in HCC-1143 cells.ConclusionsWe conclude that dasatinib with cisplatin is a rational drug combination for testing in triple-negative breast cancer.     

血管内皮生长因子D及其受体3在乳腺癌淋巴转移中作用的研究进展

乳腺癌是女性最常见的恶性肿瘤。乳腺癌淋巴转移与患者的预后密切相关。最近研究表明淋巴管生成可能会主动促进淋巴转移的发生,而血管内皮生长因子家族的部分成员在这一过程中发挥了重要作用,如血管内皮生长因子C、血管内皮生长因子D及其受体3等。但是,对乳腺癌中血管内皮生长因子D的作用及其预后价值、血管内皮生长因子受体3与乳腺癌淋巴管生成的关系等问题仍有争议。本文对近年国内外有关血管内皮生长因子D及其受体3在乳腺癌淋巴转移中作用的研究进展作一综述。     

Tumor lymphangiogenesis and metastatic spread-new players begin to emerge

The metastatic spread of tumor cells is the most lethal aspect of cancer and can occur via various routes, including the lymphatic vasculature. Studies of tumor models in animals and clinicopathological data have indicated that growth of lymphatic vessels (lymphangiogenesis) in the vicinity of solid tumors may contribute to lymphatic metastasis. Research over the past 5 years has identified a range of lymphangiogenic growth factors that could conceivably play a role in promoting tumor lymphangiogenesis and lymphatic metastasis. The most extensively studied signaling system that promotes lymphangiogenesis in tumors involves the secreted lymphangiogenic proteins vascular endothelial growth factor-C (VEGF-C) and VEGF-D, and their cognate receptor on lymphatic endothelium VEGF receptor-3 (VEGFR-3). More recent studies have identified other signaling molecules that can also promote lymphangiogenesis in vivo, including hepatocyte growth factor and members of the fibroblast growth factor, angiopoietin, platelet-derived growth factor and insulin-like growth factor families of secreted proteins. This article provides an overview of the molecular mechanisms that control lymphangiogenic signaling, emphasizing the more recently identified lymphangiogenic growth factors and the roles they may play in cancer biology. Molecular approaches for inhibiting lymphangiogenic signaling in cancer, designed to restrict tumor metastasis, are also examined.     

Phosphorylated c-Src in the nucleus is associated with improved patient outcome in ER-positive breast cancer

Elevated c-Src protein expression has been shown in breast cancer and in vitro evidence suggests a role in endocrine resistance. To investigate whether c-Src is involved in endocrine resistance, we examined the expression of both total and activated c-Src in human breast cancer specimens from a cohort of oestrogen receptor (ER)-positive tamoxifen-treated breast cancer patients. Tissue microarray technology was employed to analyse 262 tumour specimens taken before tamoxifen treatment. Immunohistochemistry using total c-Src and activated c-Src antibodies was performed. Kaplan–Meier survival curves were constructed and log-rank test were performed. High level of nuclear activated Src was significantly associated with improved overall survival (P=0.047) and lower recurrence rates on tamoxifen (P=0.02). Improved patient outcome was only seen with activated Src in the nucleus. Nuclear activated Src expression was significantly associated with node-negative disease and a lower NPI (P<0.05). On subgroup analysis, only ER-positive/progesterone receptor (PgR)-positive tumours were associated with improved survival (P=0.004). This shows that c-Src activity is increased in breast cancer and that activated Src within the nucleus of ER-positive tumours predicts an improved outcome. In ER/PgR-positive disease, activated Src kinase does not appear to be involved in de novo endocrine resistance. Further study is required in ER-negative breast cancer as this may represent a cohort in which it is associated with poor outcome.     

The membrane cytoskeletal crosslinker ezrin is required for metastasis of breast carcinoma cells

Introduction  

The membrane cytoskeletal crosslinker ezrin participates in several functions including cell adhesion, motility and cell survival, and there is increasing evidence that it regulates tumour progression. However, the role played by ezrin in breast cancer metastasis has not been clearly delineated.     

Src,a potential target for overcoming trastuzumab resistance in HER2-positive breast carcinoma

Background:

Src is a non-receptor tyrosine kinase involved in signalling and crosstalk between growth-promoting pathways. We aim to investigate the relationship of active Src in response to trastuzumab of HER2-positive breast carcinomas.

Methods:

We selected 278 HER2-positive breast cancer patients with (n=154) and without (n=124) trastuzumab treatment. We performed immunohistochemistry on paraffin-embedded tissue microarrays of active Src and several proteins involved in the PI3K/Akt/mTOR pathway, PIK3CA mutational analysis and in vitro studies (SKBR3 and BT474 cancer cells). The results were correlated with clinicopathological factors and patients'' outcome.

Results:

Increased pSrc-Y416 was demonstrated in trastuzumab-resistant cells and in 37.8% of tumours that correlated positively with tumour size, necrosis, mitosis, metastasis to the central nervous system, p53 overexpression and MAPK activation but inversely with EGFR and p27. Univariate analyses showed an association of increased active Src with shorter survival in patients at early stage with HER2/hormone receptor-negative tumours treated with trastuzumab.

Conclusions:

Src activation participates in trastuzumab mechanisms of resistance and indicates poor prognosis, mainly in HER2/hormone receptor-negative breast cancer. Therefore, blocking this axis may be beneficial in those patients.     

Apelin promotes lymphangiogenesis and lymph node metastasis

Whereas the role of the G-protein-coupled APJ receptor and its ligand, apelin, in angiogenesis has been well documented, the ability of the apelin/APJ system to induce lymphangiogenesis and lymphatic metastasis has been largely unexplored. To this end, we first show that APJ is expressed in lymphatic endothelial cells (LECs) and, moreover, that it responds to apelin by activating the apelinergic signaling cascade. We find that although apelin treatment does not influence the proliferation of LECs in vitro, it enhances their migration, protects them against UV irradiation-induced apoptosis, increases their spheroid numbers in 3D culture, stimulates their in vitro capillary-like tube formation and, furthermore, promotes the invasive growth of lymphatic microvessels in vivo in the matrigel plug assay. We also demonstrate that apelin overexpression in malignant cells is associated with accelerated in vivo tumor growth and with increased intratumoral lymphangiogenesis and lymph node metastasis. These results indicate that apelin induces lymphangiogenesis and, accordingly, plays an important role in lymphatic tumor progression. Our study does not only reveal apelin as a novel lymphangiogenic factor but might also open the door for the development of novel anticancer therapies targeting lymphangiogenesis.     

microRNA-128 plays a critical role in human non-small cell lung cancer tumourigenesis,angiogenesis and lymphangiogenesis by directly targeting vascular endothelial growth factor-C

Recent studies have indicated that microRNAs (miRNAs) are important gene regulators that play critical roles in biological processes and function as either tumour suppressors or oncogenes. Therefore, the expression levels of miRNAs can be important and reliable biomarkers for cancer detection and prognostic prediction, and potentially serve as targets for cancer therapy. In this study, we showed that the expression level of miR-128 was significantly downregulated in non-small cell lung cancer (NSCLC) tissues and cancer cells, and was significantly correlated with NSCLC differentiation, pathological stage and lymph node metastasis. Ectopic miR-128 overexpression significantly suppressed in vitro proliferation, colony formation, immigration and invasion, and induced G1 arrest and apoptosis of NSCLC cells. Interestingly, ectopic miR-128 overexpression could significantly inhibit vascular endothelial growth factor (VEGF)-C expression and reduce the activity of a luciferase reporter containing the VEGF-C 3′-untranslated region. In addition, overexpression of miR-128 in NSCLC cells and human umbilical vein endothelial cells (HUVECs) cells led to decreased expression of VEGF-A, vascular endothelial growth factor receptor (VEGFR)-2 and VEGFR-3, critical factors responsible for cancer angiogenesis and lymphangiogenesis, and subsequently decreased phosphorylation of extracellular signal-regulated kinase (ERK), phosphatidylinositol 3-kinase (AKT) and p38 signalling pathways. Furthermore, in vivo restoration of miR-128 significantly suppressed tumourigenicity of A549 cells in nude mice and inhibited both angiogenesis and lymphangiogenesis of tumour xenografts. These findings suggest that miR-128 could play a role in NSCLC tumourigenesis at least in part by modulation of angiogenesis and lymphangiogenesis through targeting VEGF-C, and could simultaneously block ERK, AKT and p38 signalling pathways. Therapeutic strategies to restore miR-128 in NSCLC could be useful to inhibit tumour progression.     

The expression of stem cell protein Piwil2 and piR-932 in breast cancer

BackgroundTo investigate the expression status of PIWIL2 and piR-932 in breast cancer stem cells and the role they could play in tumor cell growth and metastasis through Latexin.MethodsCD44⁺/CD24^? tumor cells (CSC) from clinical specimens were sorted using flow cytometry. PIWIL2 expression status was detected in CSC cells by microarray analysis and 1086 breast cancer specimens by Western blot and immunohistochemistry staining. piR-932 expression was also detected in CSC cells by piRNA microarray assay. The relationship between the PIWIL2 protein and clinico-pathological parameters and prognosis was subsequently determined.ResultsCSC cells are more likely to generate new tumors in mice and cell microspheres that are deficient in NOD/SCID compared to the control group. PIWIL2 protein was expressed higher in CSC cells compared to the control cells. In total, 334 (30.76%) of the 1086 breast cases showed high PIWIL2 expression. PIWIL2 was observed to be related to age, tumor size, histological type, tumor stage, and lymph node metastasis (all P < 0.05). Furthermore, we have found that one of the Piwi-interacting RNAs (piRNAs) called piR-932 expressed significantly higher in the breast cancer cells that were induced to EMT, and it could form immune complexes through immunoprecipitation with PIWIL2; in PIWIL2+ breast cancer stem cells, Latexin expression significantly reduced because of its promoter region CpG island methylation.ConclusionsThese results suggest that the combination of piR-932 and PIWIL2 may be a positive regulator in the process of breast cancer stem cells through promoting the methylation of Latexin, and they both could be the potential targets for blocking the metastasis of breast cancer.     

Distribution and expression of CD44 isoforms and Ezrin during prostate cancer-endothelium interaction

CD44 is a multifunctional cell surface adhesion molecule that has been implicated in tumour cell invasion and metastasis. Many cancer cell types as well as their metastases express high levels of CD44. Furthermore, the expression of certain CD44 variants has been linked with metastasis and tumour progression. It is known that ezrin, a member of the ERM family of proteins, can bind to CD44 and thus raises the possibility that it is involved in cell migration and metastasis. Therefore we examined the expression and distribution of CD44, its co-localisation and translocation with ezrin in prostate cancer cell lines as they interact with endothelial cells. Experimental results indicate prostate cancer cells express multiple CD44 isoforms that co-localise with ezrin in DU-145 and PC-3 prostate cancer cells. Treatment with hepatocyte growth factor (HGF/SF) resulted in up-regulation of CD44 and its co-translocation with ezrin during tumour-endothelial cell interactions. In addition, tumour cell adhesion to endothelial cells and their invasiveness was increased after exposure to HGF/SF, and can be blocked by the presence of anti-CD44 antibodies. It is concluded that CD44 and ezrin interact in endothelial cells and that they co-localise in the areas of tumour-endothelial contact. The CD44/ezrin complex plays a pivotal role in the capture and invasion of endothelial cells by prostate cancer cells.     

The tyrosine kinase Abl is required for Src-transforming activity in mouse fibroblasts and human breast cancer cells

The cytoplasmic tyrosine kinase Src has been implicated in signal transduction induced by growth factors and integrins. Src also shows oncogenic activity when deregulated. Accumulating evidence indicates that the tyrosine kinase Abl is an important substrate for Src signalling in normal cells. Here we show that Abl is also required for Src-induced transformation of mouse fibroblasts. Abl does not mediate tyrosine phosphorylation of Stat3 and Shc, two important regulators of Src oncogenic activity. In contrast, Abl controls the activation of the small GTPase Rac for oncogenic signalling and active Rac partly rescued Src transformation in cells with inactive Abl. Moreover, Abl mediates Src-induced extracellular regulated kinase 5 (ERK5) activation to drive cell transformation. Finally, we find that Abl/Rac and Abl/ERK5 pathways also operate in human MCF7 and BT549 breast cancer cells, where neoplastic transformation depends on Src-like activities. Therefore, Abl is an important regulator of Src oncogenic activity both in mouse fibroblasts and in human cancer cells. Targeting these Abl-dependent signalling cascades may be of therapeutic value in breast cancers where Src-like function is important.     

Targeting heat shock protein 27 (HspB1) interferes with bone metastasis and tumour formation in vivo

Background:

The small stress heat shock protein 27 (Hsp27) has recently turned as a promising target for cancer treatment. Hsp27 upregulation is associated with tumour growth and resistance to chemo- and radio-therapeutic treatments, and several ongoing drugs inhibiting Hsp27 expression are under clinical trial. Hsp27 is now well described to counteract apoptosis and its elevated expression is associated with increased aggressiveness of several primary tumours. However, its role in the later stage of tumour progression and, more specifically, in the later and most deadly stage of tumour metastasis is still unclear.

Methods/results:

In the present study, we showed by qRT–PCR that Hsp27 gene is overexpressed in a large fraction of the metastatic breast cancer area in 53 patients. We further analysed the role of this protein in mice during bone metastasis invasion and establishment by using Hsp27 genetically depleted MDA-MB231/B02 human breast cancer cell line as a model. We demonstrate that Hsp27 silencing led to reduced cell migration and invasion in vitro and that in vivo it correlated with a decreased ability of breast cancer cells to metastasise and grow in the skeleton.

Conclusion:

Altogether, these data characterised Hsp27 as a potent therapeutic target in breast cancer bone metastasis and skeletal tumour growth.