Induction of ErbB-3 expression by alpha6beta4 integrin contributes to tamoxifen resistance in ERbeta1-negative breast carcinomas

Advancing Lung Cancer Treatment with Combined c-Met Promoter-Driven Oncolytic Adenovirus and Rapamycin

Lung cancer remains a formidable health challenge due to its high mortality and morbidity rates. Non-small cell lung cancer (NSCLC) constitutes approximately 85% of all lung cancer cases, with small cell lung cancer (SCLC) accounting for the remainder. Both NSCLC and SCLC cells express receptor tyrosine kinases, which may be overexpressed or mutated in lung cancer, leading to increased activation. The c-Met receptor tyrosine kinase, crucial for cell transformation and tumor growth, invasion, and metastasis, became the focus of our study. We used an E1B55KD-deleted, replication-selective oncolytic adenovirus (Ad.What), driven by the c-Met promoter, targeting lung cancer cells with c-Met overexpression, thus sparing normal cells. Previous studies have shown the enhanced antitumor efficacy of oncolytic adenoviruses when combined with chemotherapeutic agents. We explored combining rapamycin, a selective mTOR inhibitor with promising clinical trial outcomes for various cancers, with Ad.What. This combination increased infectivity by augmenting the expression of coxsackievirus and adenovirus receptors and αV integrin on cancer cells and induced autophagy. Our findings suggest that combining a c-Met promoter-driven oncolytic adenovirus with rapamycin could be an effective lung cancer treatment strategy, offering a targeted approach to exploit lung cancer cells' vulnerabilities, potentially marking a significant advancement in managing this deadly disease.

Epigenetic factors in breast cancer therapy

Epigenetic modifications are inherited differences in cellular phenotypes, such as cell gene expression alterations, that occur during somatic cell divisions (also, in rare circumstances, in germ line transmission), but no alterations to the DNA sequence are involved. Histone alterations, polycomb/trithorax associated proteins, short non-coding or short RNAs, long non—coding RNAs (lncRNAs), & DNA methylation are just a few biological processes involved in epigenetic events. These various modifications are intricately linked. The transcriptional potential of genes is closely conditioned by epigenetic control, which is crucial in normal growth and development. Epigenetic mechanisms transmit genomic adaptation to an environment, resulting in a specific phenotype. The purpose of this systematic review is to glance at the roles of Estrogen signalling, polycomb/trithorax associated proteins, DNA methylation in breast cancer progression, as well as epigenetic mechanisms in breast cancer therapy, with an emphasis on functionality, regulatory factors, therapeutic value, and future challenges.

RNA sequencing of long-term label-retaining colon cancer stem cells identifies novel regulators of quiescence

Recent data suggest that therapy-resistant quiescent cancer stem cells (qCSCs) are the source of relapse in colon cancer. Here, using colon cancer patient-derived organoids and xenografts, we identify rare long-term label-retaining qCSCs that can re-enter the cell cycle to generate new tumors. RNA sequencing analyses demonstrated that these cells display the molecular hallmarks of quiescent tissue stem cells, including expression of p53 signaling genes, and are enriched for transcripts common to damage-induced quiescent revival stem cells of the regenerating intestine. In addition, we identify negative regulators of cell cycle, downstream of p53, that we show are indicators of poor prognosis and may be targeted for qCSC abolition in both p53 wild-type and mutant tumors. These data support the temporal inhibition of downstream targets of p53 signaling, in combination with standard-of-care treatments, for the elimination of qCSCs and prevention of relapse in colon cancer.

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Colon tumors contain therapy-resistant quiescent cancer stem cells (qCSCs)

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qCSC gene expression mirrors that of quiescent stem cells of the regenerating gut

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qCSCs are enriched for p53 signaling genes

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qCSC elimination may be achieved by inhibiting downstream targets of p53 signaling

Cancer stem cells: Culprits in endocrine resistance and racial disparities in breast cancer outcomes

Breast cancer stem cells (BCSCs) promote endocrine therapy (ET) resistance, also known as endocrine resistance in hormone receptor (HR) positive breast cancer. Endocrine resistance occurs via mechanisms that are not yet fully understood. In vitro, in vivo and clinical data suggest that signaling cascades such as Notch, hypoxia inducible factor (HIF), and integrin/Akt promote BCSC-mediated endocrine resistance. Once HR positive breast cancer patients relapse on ET, targeted therapy agents such as cyclin dependent kinase inhibitors are frequently implemented, though secondary resistance remains a threat. Here, we discuss Notch, HIF, and integrin/Akt pathway regulation of BCSC activity and potential strategies to target these pathways to counteract endocrine resistance. We also discuss a plausible link between elevated BCSC-regulatory gene levels and reduced survival observed among African American women with basal-like breast cancer which lacks HR expression. Should future studies reveal a similar link for patients with luminal breast cancer, then the use of agents that impede BCSC activity could prove highly effective in improving clinical outcomes among African American breast cancer patients.

Cell signaling and cancer: a mechanistic insight into drug resistance

Drug resistance is a major setback for advanced therapeutics in multiple cancers. The increasing prevalence of this resistance is a growing concern and bitter headache for the researchers since a decade. Hence, it is essential to revalidate the existing strategies available for cancer treatment and to look after a novel therapeutic approach for target based killing of cancer cells at the genetic level. This review outlines the different mechanisms enabling resistance including drug efflux, drug target alternation, alternative splicing, the release of the extracellular vesicle, tumor heterogeneity, epithelial-mesenchymal transition, tumor microenvironment, the secondary mutation in the receptor, epigenetic alternation, heterodimerization of receptors, amplification of target and amplification of components rather than the target. Furthermore, existing evidence and the role of various signaling pathways like EGFR, Ras, PI3K/Akt, Wnt, Notch, TGF-β, Integrin-ECM signaling in drug resistance are explained. Lastly, the prevention of this resistance by a contemporary therapeutic strategy, i.e., a combination of specific signaling pathway inhibitors and the cocktail of a cancer drug is summarized showing the new treatment strategies.

HMGA1/E2F1 axis and NFkB pathways regulate LPS progression and trabectedin resistance

Although the medical treatments of sarcoma have evolved in the last years, a significant portion of patients develops recurrence after therapies suggesting the need to identify novel targets to improve the treatments. By the use of patient-derived and established cell lines from liposarcoma, as well as specimens from patient biopsies, we found that HMGA1 is involved in the progression of dedifferentiated and myxoid liposarcoma. The immunohistochemical and RT-PCR analyses of 68 liposarcoma specimens revealed a significant high expression of HMGA1, at the protein and RNA levels, both in myxoid and dedifferentiated liposarcoma subtypes compared with differentiated ones. Loss- and gain-of-function experiments by HMGA1-specific depletion and overexpression in dedifferentiated and myxoid liposarcoma cells showed the contribution of this oncogenic factor in cell proliferation, motility, invasion, and drug resistance. The in vitro and in vivo treatment of myxoid liposarcoma with trabectedin, a drug with a potent anti-tumor activity, revealed downregulation of HMGA1, E2F1, and its-downstream targets, vimentin and ZEB1, indicating a critical role of trabectedin in inhibiting the mesenchymal markers of these tumors through the HMGA1/E2F1 axis. These data were also confirmed in patients’ tumor biopsies being HMGA1, E2F1, and vimentin expression significantly reduced upon trabectedin therapy, administered as neo-adjuvant chemotherapy. Furthermore, trabectedin treatment inhibits in vitro NFkB pathway in mixoyd liposarcoma sensitive but not in resistant counterparts, and the inhibition of NFkB pathway re-sensitizes the resistant cells to trabectedin treatment. These data support the rational for combining NFkB inhibitors with trabectedin in liposarcoma patients, who have become resistant to the drug.

Transcriptional profiling of NCI/ADR-RES cells unveils a complex network of signaling pathways and molecular mechanisms of drug resistance

Background

Ovarian cancer has the highest mortality rate among all the gynecological cancers. This is mostly due to the resistance of ovarian cancer to current chemotherapy regimens. Therefore, it is of crucial importance to identify the molecular mechanisms associated with chemoresistance.

Methods

NCI/ADR-RES is a multidrug-resistant cell line that is a model for the study of drug resistance in ovarian cancer. We carried out a microarray-derived transcriptional profiling analysis of NCI/ADR-RES to identify differentially expressed genes relative to its parental OVCAR-8.

Results

Gene-expression profiling has allowed the identification of genes and pathways that may be important for the development of drug resistance in ovarian cancer. The NCI/ADR-RES cell line has differential expression of genes involved in drug extrusion, inactivation, and efficacy, as well as genes involved in the architectural and functional reorganization of the extracellular matrix. These genes are controlled through different signaling pathways, including MAPK–Akt, Wnt, and Notch.

Conclusion

Our findings highlight the importance of using orthogonal therapies that target completely independent pathways to overcome mechanisms of resistance to both classical chemotherapeutic agents and molecularly targeted drugs.

Vaccination targeting human HER3 alters the phenotype of infiltrating T cells and responses to immune checkpoint inhibition

Expression of human epidermal growth factor family member 3 (HER3), a critical heterodimerization partner with EGFR and HER2, promotes more aggressive biology in breast and other epithelial malignancies. As such, inhibiting HER3 could have broad applicability to the treatment of EGFR- and HER2-driven tumors. Although lack of a functional kinase domain limits the use of receptor tyrosine kinase inhibitors, HER3 contains antigenic targets for T cells and antibodies. Using novel human HER3 transgenic mouse models of breast cancer, we demonstrate that immunization with recombinant adenoviral vectors encoding full length human HER3 (Ad-HER3-FL) induces HER3-specific T cells and antibodies, alters the T cell infiltrate in tumors, and influences responses to immune checkpoint inhibitions. Both preventative and therapeutic Ad-HER3-FL immunization delayed tumor growth but were associated with both intratumoral PD-1 expressing CD8⁺ T cells and regulatory CD4⁺ T cell infiltrates. Immune checkpoint inhibition with either anti-PD-1 or anti-PD-L1 antibodies increased intratumoral CD8⁺ T cell infiltration and eliminated tumor following preventive vaccination with Ad-HER3-FL vaccine. The combination of dual PD-1/PD-L1 and CTLA4 blockade slowed the growth of tumor in response to Ad-HER3-FL in the therapeutic model. We conclude that HER3-targeting vaccines activate HER3-specific T cells and induce anti-HER3 specific antibodies, which alters the intratumoral T cell infiltrate and responses to immune checkpoint inhibition.

Dual targeting of HER3 and MEK may overcome HER3-dependent drug-resistance of colon cancers

Although the medical treatment of colorectal cancer has evolved greatly in the last years, a significant portion of early-stage patients develops recurrence after therapies. The current clinical trials are directed to evaluate new drug combinations and treatment schedules.

By the use of patient-derived or established colon cancer cell lines, we found that the tyrosine kinase receptor HER3 is involved in the mechanisms of resistance to therapies. In agreement, the immunohistochemical analysis of total and phospho-HER3 expression in 185 colorectal cancer specimens revealed a significant correlation with lower disease-free survival.

Targeting HER3 by the use of the monoclonal antibody patritumab we found induction of growth arrest in all cell lines. Despite the high efficiency of patritumab in abrogating the HER3-dependent activation of PI3K pathway, the HER2 and EGFR-dependent MAPK pathway is activated as a compensatory mechanism. Interestingly, we found that the MEK-inhibitor trametinib inhibits, as expected, the MAPK pathway but induces the HER3-dependent activation of PI3K pathway. The combined treatment results in the abrogation of both PI3K and MAPK pathways and in a significant reduction of cell proliferation and survival.

These data suggest a new strategy of therapy for HER3-overexpressing colon cancers.

Pancreatic cancer stem cell markers and exosomes - the incentive push

Pancreatic cancer (PaCa) has the highest death rate and incidence is increasing. Poor prognosis is due to late diagnosis and early metastatic spread, which is ascribed to a minor population of so called cancer stem cells (CSC) within the mass of the primary tumor. CSC are defined by biological features, which they share with adult stem cells like longevity, rare cell division, the capacity for self renewal, differentiation, drug resistance and the requirement for a niche. CSC can also be identified by sets of markers, which for pancreatic CSC (Pa-CSC) include CD44v6, c-Met, Tspan8, alpha6beta4, CXCR4, CD133, EpCAM and claudin7. The functional relevance of CSC markers is still disputed. We hypothesize that Pa-CSC markers play a decisive role in tumor progression. This is fostered by the location in glycolipid-enriched membrane domains, which function as signaling platform and support connectivity of the individual Pa-CSC markers. Outside-in signaling supports apoptosis resistance, stem cell gene expression and tumor suppressor gene repression as well as miRNA transcription and silencing. Pa-CSC markers also contribute to motility and invasiveness. By ligand binding host cells are triggered towards creating a milieu supporting Pa-CSC maintenance. Furthermore, CSC markers contribute to the generation, loading and delivery of exosomes, whereby CSC gain the capacity for a cell-cell contact independent crosstalk with the host and neighboring non-CSC. This allows Pa-CSC exosomes (TEX) to reprogram neighboring non-CSC towards epithelial mesenchymal transition and to stimulate host cells towards preparing a niche for metastasizing tumor cells. Finally, TEX communicate with the matrix to support tumor cell motility, invasion and homing. We will discuss the possibility that CSC markers are the initial trigger for these processes and what is the special contribution of CSC-TEX.

Sema6A and Mical1 control cell growth and survival of BRAFV600E human melanoma cells

We used whole genome microarray analysis to identify potential candidate genes with differential expression in BRAFV600E vs NRASQ61R melanoma cells. We selected, for comparison, a peculiar model based on melanoma clones, isolated from a single tumor characterized by mutually exclusive expression of BRAFV600E and NRASQ61R in different cells. This effort led us to identify two genes, SEMA6A and MICAL1, highly expressed in BRAF-mutant vs NRAS-mutant clones. Real-time PCR, Western blot and immunohistochemistry confirmed preferential expression of Sema6A and Mical1 in BRAFV600E melanoma. Sema6A is a member of the semaphorin family, and it complexes with the plexins to regulate actin cytoskeleton, motility and cell proliferation. Silencing of Sema6A in BRAF-mutant cells caused cytoskeletal remodeling, and loss of stress fibers, that in turn induced cell death. Furthermore, Sema6A depletion caused loss of anchorage-independent growth, inhibition of chemotaxis and invasion. Forced Sema6A overexpression, in NRASQ61R clones, induced anchorage-independent growth, and a significant increase of invasiveness. Mical1, that links Sema/PlexinA signaling, is also a negative regulator of apoptosis. Indeed, Mical-1 depletion in BRAF mutant cells restored MST-1-dependent NDR phosphorylation and promoted a rapid and massive NDR-dependent apoptosis. Overall, our data suggest that Sema6A and Mical1 may represent new potential therapeutic targets in BRAFV600E melanoma.

Syndecan-1 and Syndecan-4 Capture Epidermal Growth Factor Receptor Family Members and the α3β1 Integrin Via Binding Sites in Their Ectodomains: NOVEL SYNSTATINS PREVENT KINASE CAPTURE AND INHIBIT α6β4-INTEGRIN-DEPENDENT EPITHELIAL CELL MOTILITY

The α6β4 integrin is known to associate with receptor tyrosine kinases when engaged in epithelial wound healing and in carcinoma invasion and survival. Prior work has shown that HER2 associates with α6β4 integrin and syndecan-1 (Sdc1), in which Sdc1 engages the cytoplasmic domain of the β4 integrin subunit allowing HER2-dependent motility and carcinoma cell survival. In contrast, EGFR associates with Sdc4 and the α6β4 integrin, and EGFR-dependent motility depends on cytoplasmic engagement of β4 integrin with Sdc4. However, how HER2 and EGFR assimilate into a complex with the syndecans and integrin, and why kinase capture is syndecan-specific has remained unknown. In the present study, we demonstrate that HER2 is captured via a site, comprised of amino acids 210-240, in the extracellular domain of human Sdc1, and EGFR is captured via an extracellular site comprised of amino acids 87-131 in human Sdc4. Binding assays using purified recombinant proteins demonstrate that the interaction between the EGFR family members and the syndecans is direct. The α3β1 integrin, which is responsible for the motility of the cells, is captured at these sites as well. Peptides based on the interaction motifs in Sdc1 and Sdc4, called synstatins (SSTN210-240 and SSTN87-131) competitively displace the receptor tyrosine kinase and α3β1 integrin from the syndecan with an IC50 of 100-300 nm. The syndecans remain anchored to the α6β4 integrin via its cytoplasmic domain, but the activation of cell motility is disrupted. These novel SSTN peptides are potential therapeutics for carcinomas that depend on these HER2- and EGFR-coupled mechanisms for their invasion and survival.

Clinical significance of the integrin α6β4 in human malignancies

Integrin α6β4 is a cellular adhesion molecule that binds to laminins in the extracellular matrix and nucleates the formation of hemidesmosomes. During carcinoma progression, integrin α6β4 is released from hemidesmosomes, where it can then signal to facilitate multiple aspects of tumor progression including sustaining proliferative signaling, tumor invasion and metastasis, evasion of apoptosis, and stimulation of angiogenesis. The integrin achieves these ends by cooperating with growth factor receptors including EGFR, ErbB-2, and c-Met to amplify downstream pathways such as PI3K, AKT, MAPK, and the Rho family small GTPases. Furthermore, it dramatically alters the transcriptome toward a more invasive phenotype by controlling promoter DNA demethylation of invasion and metastasis-associated proteins, such as S100A4 and autotaxin, and upregulates and activates key tumor-promoting transcription factors such as the NFATs and NF-κB. Expression of integrin α6β4 has been studied in many human malignancies where its overexpression is associated with aggressive behavior and a poor prognosis. This review provides an assessment of integrin α6β4 expression patterns and their prognostic significance in human malignancies, and describes key signaling functions of integrin α6β4 that contribute to tumor progression.

β1 and β4 integrins: from breast development to clinical practice

Following a highly dynamic and complex dialogue between the epithelium and the surrounding microenvironment, the mammary gland develops into a branching structure during puberty, buds during pregnancy, forms intricate polar acini during lactation and, once the babies are weaned, remodels and involutes. At every stage of menstrual and pregnancy cycles, interactions between the cells and the extracellular matrix (ECM) and homotypic and heterotypic cell–cell interactions give rise to the architecture and function of the gland at that junction. These orchestrated programs would not be possible without the important role of the ECM receptors, integrins being the prime examples. The ECM–integrin axis regulates many crucial cellular functions including survival, migration and quiescence; the imbalance in any of these processes could contribute to oncogenesis. In this review we spotlight the involvement of two prominent integrin subunits, β1 and β4 integrins, in cross-talk with tyrosine kinase receptors, and we discuss the roles of these integrin subunits in the biology of normal breast differentiation and as potential prognostic and therapeutic targets in breast cancer.

Antihormone induced compensatory signalling in breast cancer: an adverse event in the development of endocrine resistance

Using MCF7 breast cancer cells, it has been shown that antihormones promote expression/activity of oestrogen-repressed tyrosine kinases, notably EGFR, HER2 and Src. These inductive events confer responsiveness to targeted inhibitors (e.g., gefitinib, trastuzumab, saracatinib). We observed that these antihormone-induced phenomena are common to ER+HER2- and ER+HER2+ breast cancer models in vitro, where targeting of EGFR, HER2 or Src alongside antihormone improves antitumour response and delays/prevents endocrine resistance. Such targeted inhibitors also subvert acquired endocrine resistant cells which retain increased EGFR, HER2 and Src (e.g., TAMR and FASR models derived after 6-12 months of tamoxifen or Faslodex treatment). Thus, antihormone-induced tyrosine kinases comprise "compensatory signalling" crucial in limiting maximal initial antihormone response and subsequently driving acquired resistance in vitro. However, despite such convincing preclinical findings from our group and others, clinical trials examining equivalent antigrowth factor strategies have proved relatively disappointing. Our new studies deciphering underlying causes reveal that further antihormone-promoted events could be pivotal in vivo. Firstly, Faslodex induces HER3 and HER4 which sensitise ER+ cells to heregulin, a paracrine growth factor that overcomes endocrine response and diminishes antitumour effect of agents targeting EGFR, HER2 or Src alongside antihormone. Secondly, extended antihormone exposure (experienced by ER+ cells prior to adjuvant clinical relapse) can "reprogramme" the compensatory kinase profile in vitro, hindering candidate antigrowth factor targeting of endocrine resistance. Faslodex resistant cells maintained with this antihormone for 3 years in vitro lose EGFR/HER2 dependency, gaining alternative mitogenic/invasion kinases. Deciphering these previously unrecognised antihormone-induced events could provide superior treatments to control endocrine relapse in the clinic.

Cytoplasmic domain interactions of syndecan-1 and syndecan-4 with α6β4 integrin mediate human epidermal growth factor receptor (HER1 and HER2)-dependent motility and survival

Epithelial cells are highly dependent during wound healing and tumorigenesis on the α6β4 integrin and its association with receptor tyrosine kinases. Previous work showed that phosphorylation of the β4 subunit upon matrix engagement depends on the matrix receptor syndecan (Sdc)-1 engaging the cytoplasmic domain of the β4 integrin and coupling of the integrin to human epidermal growth factor receptor-2 (HER2). In this study, HER2-dependent migration activated by matrix engagement is compared with migration stimulated by EGF. We find that whereas HER2-dependent migration depends on Sdc1, EGF-dependent migration depends on a complex consisting of human epidermal growth factor receptor-1 (HER1, commonly known as EGFR), α6β4, and Sdc4. The two syndecans recognize distinct sites at the extreme C terminus of the β4 integrin cytoplasmic domain. The binding motif in Sdc1 is QEEXYX, composed in part by its syndecan-specific variable (V) region and in part by the second conserved (C2) region that it shares with other syndecans. A cell-penetrating peptide containing this sequence competes for HER2-dependent epithelial migration and carcinoma survival, although it is without effect on the EGFR-stimulated mechanism. β4 mutants bearing mutations specific for Sdc1 and Sdc4 recognition act as dominant negative mutants to block cell spreading or cell migration that depends on HER2 or EGFR, respectively. The interaction of the α6β4 integrin with the syndecans appears critical for it to be utilized as a signaling platform; migration depends on α3β1 integrin binding to laminin 332 (LN332; also known as laminin 5), whereas antibodies that block α6β4 binding are without effect. These findings indicate that specific syndecan family members are likely to have key roles in α6β4 integrin activation by receptor tyrosine kinases.

The impact of tumor stroma on drug response in breast cancer

In the last two decades the breast cancer mortality rate has steadily declined, in part, due to the availability of better treatment options. However, drug resistance still remains a major challenge. Resistance can be an inherent feature of breast cancer cells, but can also arise from the tumor microenvironment. This review aims to focus on the modulatory effect of the tumor microenvironment on the differing response of breast cancer subtypes to targeted drugs and chemotherapy.

Do type 1 receptor tyrosine kinases inform treatment choice? A prospectively planned analysis of the TEAM trial

BACKGROUND

Epidermal growth factor receptors contribute to breast cancer relapse during endocrine therapy. Substitution of aromatase inhibitors (AIs) may improve outcomes in HER-positive cancers.

METHODS

Tissue microarrays were constructed. Quantitative analysis of HER1, HER2, and HER3 was performed. Data were analysed relative to disease-free survival and treatment using outcomes at 2.75 and 6.5 years.

RESULTS

Among 4541 eligible samples, 4225 (93%) had complete HER1-3 data. Overall, 5% were HER1-positive, 13% HER2-positive, and 21% HER3-positive; 32% (n=1351) overexpressed at least one HER receptor. In the HER1-3-negative subgroup, the hazard ratio (HR) for upfront exemestane vs tamoxifen at 2.75 years was 0.67 (95% confidence interval (CI), 0.52-0.87), in the HER1-3-positive subgroup, the HR was 1.15 (95% CI, 0.85-1.56). A prospectively planned treatment-by-marker analysis demonstrated a significant interaction between HER1-3 and treatment at 2.75 years (HR=0.58; 95% CI, 0.39-0.87; P=0.008), as confirmed by multivariate regression analysis adjusting for prognostic factors (HR=0.55; 95% CI, 0.36-0.85; P=0.005). This effect was time dependent.

CONCLUSION

In the 2.75 years prior to switching patients initially treated with tamoxifen to exemestane, a significant treatment-by-marker effect exists between AI/tamoxifen treatment and HER1-3 expression, suggesting HER expression could be used to select appropriate endocrine treatment at diagnosis to prevent or delay early relapses.

Dual roles of the transcription factor grainyhead-like 2 (GRHL2) in breast cancer

Using a retrovirus-mediated cDNA expression cloning approach, we identified the grainyhead-like 2 (GRHL2) transcription factor as novel protooncogene. Overexpression of GRHL2 in NIH3T3 cells induced striking morphological changes, an increase in cell proliferation, anchorage-independent growth, and tumor growth in vivo. By combining a microarray analysis and a phylogenetic footprinting analysis with various biochemical assays, we identified the epidermal growth factor receptor family member Erbb3 as a novel GRHL2 target gene. In breast cancer cell lines, shRNA-mediated knockdown of GRHL2 expression or functional inactivation of GRHL2 using dominant negative GRHL2 proteins induces down-regulation of ERBB3 gene expression, a striking reduction in cell proliferation, and morphological and phenotypical alterations characteristic of an epithelial-to-mesenchymal transition (EMT), thus implying contradictory roles of GRHL2 in breast carcinogenesis. Interestingly, we could further demonstrate that expression of GRHL2 is directly suppressed by the transcription factor zinc finger enhancer-binding protein 1 (ZEB1), which in turn is a direct target for repression by GRHL2, suggesting that the EMT transcription factors GRHL2 and ZEB1 form a double negative regulatory feedback loop in breast cancer cells. Finally, a comprehensive immunohistochemical analysis of GRHL2 expression in primary breast cancers showed loss of GRHL2 expression at the invasive front of primary tumors. A pathophysiological relevance of GRHL2 in breast cancer metastasis is further demonstrated by our finding of a statistically significant association between loss of GRHL2 expression in primary breast cancers and lymph node metastasis. We thus demonstrate a crucial role of GRHL2 in breast carcinogenesis.

Role of β4 integrin in HER-3-negative, K-RAS wild-type metastatic colorectal tumors receiving cetuximab

AIMS

Altered α6β4 integrin expression has been demonstrated in HER-3-negative tumors and may be responsible for anti-HER treatment resistance. The current study aimed to evaluate the interaction between polymorphisms of α6 and β4 integrins and clinical outcome in HER-3-negative, K-RAS wild-type colorectal cancer patients receiving cetuximab.

PATIENTS & METHODS

K-RAS analysis was performed via direct sequencing, HER-3 was evaluated by immunohistochemistry and genotyping of α6 and β4 integrins was performed by real-time PCR.

RESULTS

An univariate analysis, the β4 rs8669, rs871443 and rs9367 polymorphisms correlated with progression-free and overall survival. On multivariate analysis, only the β4 rs8669 maintained an independent role in influencing progression-free survival.

CONCLUSION

We believe that β4 rs8669 genotyping may help to identify a subgroup of HER-3-negative, K-RAS wild-type colorectal cancer patients who are more likely to benefit from anti-EGFR treatment. Our findings could also be relevant in planning future trials testing treatment strategies against the integrin-activated molecular pathways.

Inhibition of p85, the non-catalytic subunit of phosphatidylinositol 3-kinase, exerts potent antitumor activity in human breast cancer cells

The phosphoinositide 3-kinases (PI3Ks) are heterodimers consisting of the catalytic subunit p110 and the regulatory subunit p85. The PI3K/Akt pathway is strongly deregulated in breast cancer (BC) representing one of the mechanisms of resistance to therapies. Therefore, the identification of inhibitors of PI3K components represents one of the main goals to produce therapeutic agents. Here, we evaluated the efficacy of a phosphopeptide 1257 (P-1257) that targeting p85 strongly inhibits PI3K activity. We tested the effects of P-1257 administration in vitro and in vivo using BC cells expressing different levels of ErbB-2 and resistant or responsive to Trastuzumab. We demonstrated that inhibition of p85 activity by P-1257 induces cell death and sensitizes JIMT-1 and KPL-4 ErbB-2-overexpressing BC cells to Trastuzumab treatment. It is noteworthy that P-1257 delivery in vivo by electroporation or liposomes significantly inhibits the proliferation of tumor cells engrafted at subcutaneous and visceral sites. Overall, our data indicate that the p85 subunit is a valid target for therapeutic approaches and suggest that the structure of the peptide used in our study could be utilized for the development of novel drugs to apply in combination with therapies that fail to cure BCs with high PI3K activity.

Can predictive biomarkers in breast cancer guide adjuvant endocrine therapy?

Personalized medicine for oestrogen receptor-α (ERα)-positive breast cancer requires predictive biomarkers for broad endocrine resistance as well as biomarkers capable of predicting resistance to a specific agent. In addition, biomarkers could be used to select patients that might benefit from the addition of treatments that do not target ERα. However, biomarker identification studies seem to be far from consistent and identified biomarkers seldom face an introduction into clinical practice. Importantly, most of the studies that seek to identify biomarkers have been performed using material from consecutive series of patients treated with tamoxifen (the most commonly prescribed ERα antagonist). Consequently, the predictive value of any biomarker identified is confounded by its prognostic value. Another important issue is the lack of differentiation between premenopausal and postmenopausal patients with breast cancer. The hormonal environment of a tumour in patients who are premenopausal is intrinsically distinct from those arising in postmenopausal women. Biomarkers of different biological mechanisms might enable the prediction of either broad endocrine resistance or resistance to a specific agent in each of these patient subtypes. Ultimately, improvements to study design are needed to establish the clinical validity of the most promising biomarkers to predict benefit from endocrine therapy.

Controlled breast cancer microarrays for the deconvolution of cellular multilayering and density effects upon drug responses

Background

Increasing evidence shows that the cancer microenvironment affects both tumorigenesis and the response of cancer to drug treatment. Therefore in vitro models that selectively reflect characteristics of the in vivo environment are greatly needed. Current methods allow us to screen the effect of extrinsic parameters such as matrix composition and to model the complex and three-dimensional (3D) cancer environment. However, 3D models that reflect characteristics of the in vivo environment are typically too complex and do not allow the separation of discrete extrinsic parameters.

Methodology/Principal Findings

In this study we used a poly(ethylene glycol) (PEG) hydrogel-based microwell array to model breast cancer cell behavior in multilayer cell clusters that allows a rigorous control of the environment. The innovative array fabrication enables different matrix proteins to be integrated into the bottom surface of microwells. Thereby, extrinsic parameters including dimensionality, type of matrix coating and the extent of cell-cell adhesion could be independently studied. Our results suggest that cell to matrix interactions and increased cell-cell adhesion, at high cell density, induce independent effects on the response to Taxol in multilayer breast cancer cell clusters. In addition, comparing the levels of apoptosis and proliferation revealed that drug resistance mediated by cell-cell adhesion can be related to altered cell cycle regulation. Conversely, the matrix-dependent response to Taxol did not correlate with proliferation changes suggesting that cell death inhibition may be responsible for this effect.

Conclusions/Significance

The application of the PEG hydrogel platform provided novel insight into the independent role of extrinsic parameters controlling drug response. The presented platform may not only become a useful tool for basic research related to the role of the cancer microenvironment but could also serve as a complementary platform for in vitro drug development.

Integrin signaling in cancer cell survival and chemoresistance

Resistance to apoptosis and chemotherapy is a hallmark of cancer cells, and it is a critical factor in cancer recurrence and patient relapse. Extracellular matrix (ECM) via its receptors, the integrins, has emerged as a major pathway contributing to cancer cell survival and resistance to chemotherapy. Several studies over the last decade have demonstrated that ECM/integrin signaling provides a survival advantage to various cancer cell types against numerous chemotherapeutic drugs and against antibody therapy. In this paper, we will discuss the major findings on how ECM/integrin signaling protects tumor cells from drug-induced apoptosis. We will also discuss the potential role of ECM in malignant T-cell survival and in cancer stem cell resistance. Understanding how integrins and their signaling partners promote tumor cell survival and chemoresistance will likely lead to the development of new therapeutic strategies and agents for cancer treatment.

Critical analysis of simultaneous blockage of histone deacetylase and multiple receptor tyrosine kinase in the treatment of prostate cancer

BACKGROUND

The concept of molecular tumor targeting might be an innovative option to treat advanced prostate cancer. We analyzed the effect of combining the multiple receptor tyrosine kinase inhibitor AEE788 and the histone deacetylase (HDAC) inhibitor valproic acid (VPA) on adhesion and growth properties of prostate cancer cell lines.

METHODS

PC-3, DU-145, and LNCaP cells were treated with AEE788, VPA or with an AEE788-VPA combination, and cell cycle progression investigated. Furthermore, tumor cell adhesion to vascular endothelium or to immobilized extracellular matrix proteins was evaluated, and integrin α and β subtypes were analyzed. Finally, effects of drug treatment on cell signaling pathways were determined.

RESULTS

AEE788 moderately and VPA strongly reduced tumor cell adhesion and growth. VPA impaired cell cycle progression and altered the expression level of the cell cycle regulating proteins cdk1, cdk2, cdk4, cyclin B, D1, cyclin E, p21, and p27. VPA also acted on the membranous, cytoplasmic, and gene expression pattern of various integrin α and β subtypes. AEE788 acted likewise, but more moderately. Combining AEE788 and VPA did not result in an additive anti-tumor effect. Signaling analysis revealed that the EGFr downstream target Akt was similarly modified in the presence of VPA or the VPA-AEE788 combination, but not influenced by AEE788 alone.

CONCLUSIONS

The AEE788-VPA combination has no advantage over VPA monotreatment in vitro. The non-responsiveness of Akt

Fulvestrant-induced expression of ErbB3 and ErbB4 receptors sensitizes oestrogen receptor-positive breast cancer cells to heregulin β1

Introduction

We have previously reported that induction of epidermal growth factor receptor and ErbB2 in response to antihormonal agents may provide an early mechanism to allow breast cancer cells to evade the growth-inhibitory action of such therapies and ultimately drive resistant cell growth. More recently, the other two members of the ErbB receptor family, ErbB3 and ErbB4, have been implicated in antihormone resistance in breast cancer. In the present study, we have investigated whether induction of ErbB3 and/or ErbB4 may provide an alternative resistance mechanism to antihormonal action in a panel of four oestrogen receptor (ER)-positive breast cancer cell lines.

Methods

MCF-7, T47D, BT474 and MDAMB361 cell lines were exposed to fulvestrant (100 nM) for seven days, and effects on ErbB3/4 expression and signalling, as well as on cell growth, were assessed. Effects of heregulin β1 (HRGβ1) were also examined in the absence and presence of fulvestrant to determine the impact of ER blockade on the capacity of this ErbB3/4 ligand to promote signalling and cell proliferation.

Results

Fulvestrant potently reduced ER expression and transcriptional activity and significantly inhibited growth in MCF-7, T47D, BT474 and MDAMB361 cells. However, alongside this inhibitory activity, fulvestrant also consistently induced protein expression and activity of ErbB3 in MCF-7 and T47D cells and ErbB4 in BT474 and MDAMB361 cell lines. Consequently, fulvestrant treatment sensitised all cell lines to the actions of the ErbB3/4 ligand HRGβ1 with enhanced ErbB3/4-driven signalling activity, reexpression of cyclin D1 and significant increases in cell proliferation being observed when compared to untreated cells. Indeed, in T47D and MDAMB361 HRGβ1 was converted from a ligand having negligible or suppressive growth activity into one that potently promoted cell proliferation. Consequently, fulvestrant-mediated growth inhibition was completely overridden by HRGβ1 in all four cell lines.

Conclusions

These findings suggest that although antihormones such as fulvestrant may have potent acute growth-inhibitory activity in ER-positive breast cancer cells, their ability to induce and sensitise cells to growth factors may serve to reduce and ultimately limit their inhibitory activity.

Mechanisms of endocrine resistance in breast cancer

The estrogen receptor (ER) pathway plays a pivotal role in breast cancer development and progression. Endocrine therapy to block the ER pathway is highly effective, but its usefulness is limited by common intrinsic and acquired resistance. Multiple mechanisms responsible for endocrine resistance have been proposed and include deregulation of various components of the ER pathway itself, alterations in cell cycle and cell survival signaling molecules, and the activation of escape pathways that can provide tumors with alternative proliferative and survival stimuli. Among these, increased expression or signaling of growth factor receptor pathways, especially the EGFR/HER2 pathway, has been associated with both experimental and clinical endocrine therapy resistance. New treatment combinations targeting both ER and growth factor receptor signaling to block the crosstalk between these pathways and eliminate escape routes have been proven highly effective in preclinical models. Results of recent clinical studies, while partly supporting this approach, also highlight the need to better identify a priori the patients whose tumors are most likely to benefit from these specific cotargeting strategies.

ZNF217, a candidate breast cancer oncogene amplified at 20q13, regulates expression of the ErbB3 receptor tyrosine kinase in breast cancer cells

Understanding the mechanisms underlying ErbB3 overexpression in breast cancer will facilitate the rational design of therapies to disrupt ErbB2-ErbB3 oncogenic function. Although ErbB3 overexpression is frequently observed in breast cancer, the factors mediating its aberrant expression are poorly understood. In particular, the ErbB3 gene is not significantly amplified, raising the question as to how ErbB3 overexpression is achieved. In this study we showed that the ZNF217 transcription factor, amplified at 20q13 in ∼20% of breast tumors, regulates ErbB3 expression. Analysis of a panel of human breast cancer cell lines (n = 50) and primary human breast tumors (n = 15) showed a strong positive correlation between ZNF217 and ErbB3 expression. Ectopic expression of ZNF217 in human mammary epithelial cells induced ErbB3 expression, whereas ZNF217 silencing in breast cancer cells resulted in decreased ErbB3 expression. Although ZNF217 has previously been linked with transcriptional repression because of its close association with C-terminal-binding protein (CtBP)1/2 repressor complexes, our results show that ZNF217 also activates gene expression. We showed that ZNF217 recruitment to the ErbB3 promoter is CtBP1/2-independent and that ZNF217 and CtBP1/2 have opposite roles in regulating ErbB3 expression. In addition, we identify ErbB3 as one of the mechanisms by which ZNF217 augments PI-3K/Akt signaling.

Targeting miR-205 in breast cancer

As small non-coding regulatory RNAs, microRNAs are capable of silencing gene expression by translational repression or mRNA degradation. Accumulating evidence indicates that deregulation of microRNAs is often associated with human malignancies and suggests a causal role of microRNAs in neoplasia, presumably because microRNAs can function as oncogenes or tumor suppressors. Among them, miR-205 is significantly underexpressed in breast tumors compared with matched normal breast tissue although miR-205 has been shown to be upregulated in some other type of tumors. Furthermore, breast cancer cell lines, including MCF-7 and MDA-MB-231, express a lower level of miR-205 than the non-malignant MCF-10A cells. Ectopic expression of miR-205 significantly inhibits cell proliferation and anchorage-independent growth as well as cell invasion. These findings establish the tumor suppressive role of miR-205, which is probably through direct targeting of oncogenes such as ErbB3 and Zeb1. Therefore, miR-205 may serve as a unique therapeutic target for breast cancer.

HER3 is required for the maintenance of neuregulin-dependent and -independent attributes of malignant progression in prostate cancer cells

HER3 (ERBB3) is a catalytically inactive pseudokinase of the HER receptor tyrosine kinase family, frequently overexpressed in prostate and other cancers. Aberrant expression and mutations of 2 other members of the family, EGFR and HER2, are key carcinogenic events in several types of tumors, and both are well- validated therapeutic targets. In this study, we show that HER3 is required to maintain the motile and invasive phenotypes of prostate (DU-145) and breast (MCF-7) cancer cells in response to the HER3 ligand neuregulin-1 (NRG-1), epidermal growth factor (EGF) and fetal bovine serum. Although MCF-7 breast cancer cells appeared to require HER3 as part of an autocrine response induced by EGF and FBS, the response of DU-145 prostate cancer cells to these stimuli, while requiring HER3, did not appear to involve autocrine stimulation of the receptor. DU-145 cells required the expression of HER3 for efficient clonogenicity in vitro in standard growth medium and for tumorigenicity in immunodeficient mice. These observations suggest that prostate cancer cells derived from tumors that overexpress HER3 are dependent on its expression for the maintenance of major attributes of neoplastic aggressiveness, with or without cognate ligand stimulation.

Environment-mediated drug resistance: a major contributor to minimal residual disease

Environment-mediated drug resistance is a form of de novo drug resistance that protects tumour cells from the initial effects of diverse therapies. Surviving foci of residual disease can then develop complex and permanent acquired resistance in response to the selective pressure of therapy. Recent evidence indicates that environment-mediated drug resistance arises from an adaptive, reciprocal signalling dialogue between tumour cells and the surrounding microenvironment. We propose that new therapeutic strategies targeting this interaction should be applied during initial treatment to prevent the emergence of acquired resistance.

Micro-SPECT/CT with 111In-DTPA-pertuzumab sensitively detects trastuzumab-mediated HER2 downregulation and tumor response in athymic mice bearing MDA-MB-361 human breast cancer xenografts

Pertuzumab is a HER2 dimerization inhibitor that binds to an epitope unique from that of trastuzumab. Our objective was to determine whether SPECT with (111)In-diethylenetriaminepentaacetic acid-pertuzumab ((111)In-DTPA-pertuzumab) could sensitively detect an early molecular response to trastuzumab manifested by HER2 downregulation and a later tumor response revealed by a decreased number of HER2-positive viable tumor cells.

METHODS

Changes in HER2 density in SKBr-3 and MDA-MB-361 BC cells exposed to trastuzumab (14 microg/mL) in vitro were measured by saturation binding assays using (111)In-DTPA-pertuzumab and by confocal immunofluorescence microscopy and flow cytometry with fluorescein isothiocyanate-labeled HER2/neu antibodies. Imaging of HER2 downregulation was studied in vivo in athymic mice with subcutaneous MDA-MB-361 tumors treated for 3 d with trastuzumab (4 mg/kg) or nonspecific human IgG (hIgG) or phosphate-buffered saline (PBS). Imaging of tumor response to trastuzumab was studied in mice bearing subcutaneous MDA-MB-361 xenografts treated with trastuzumab (4 mg/kg), followed by weekly doses of nonspecific hIgG or rituximab or PBS (2 mg/kg). Mice were imaged on a micro-SPECT/CT system at 72 h after injection of (111)In-DTPA-pertuzumab. Tumor and normal-tissue biodistribution was determined.

RESULTS

(111)In-DTPA-pertuzumab saturation binding to SKBr-3 and MDA-MB-361 cells was significantly decreased at 72 h after exposure in vitro to trastuzumab (14 microg/mL), compared with untreated controls (62% +/- 2%, P < 0.0001; 32% +/- 9%, P < 0.0002, respectively). After 3 d of trastuzumab, in vivo tumor uptake of (111)In-DTPA-pertuzumab decreased 2-fold in trastuzumab- versus PBS-treated mice (13.5 +/- 2.6 percentage injected dose per gram [%ID/g] vs. 28.5 +/- 9.1 %ID/g, respectively; P < 0.05). There was also a 2-fold decreased tumor uptake in trastuzumab- versus PBS-treated mice by image volume-of-interest analysis (P = 0.05), suggesting trastuzumab-mediated HER2 downregulation. After 3 wk of trastuzumab, tumor uptake of (111)In-DTPA-pertuzumab decreased 4.5-fold, compared with PBS-treated mice (7.6 +/- 0.4 vs. 34.6 +/- 9.9 %ID/g, respectively; P < 0.001); this decrease was associated with an almost-completed eradication of HER2-positive tumor cells determined immunohistochemically.

CONCLUSION

(111)In-DTPA-pertuzumab sensitively imaged HER2 downregulation after 3 d of treatment with trastuzumab and detected a reduction in viable HER2-positive tumor cells after 3 wk of therapy in MDA-MB-361 human breast cancer xenografts.

Therapeutically targeting ErbB3: a key node in ligand-induced activation of the ErbB receptor-PI3K axis

The signaling network downstream of the ErbB family of receptors has been extensively targeted by cancer therapeutics; however, understanding the relative importance of the different components of the ErbB network is nontrivial. To explore the optimal way to therapeutically inhibit combinatorial, ligand-induced activation of the ErbB-phosphatidylinositol 3-kinase (PI3K) axis, we built a computational model of the ErbB signaling network that describes the most effective ErbB ligands, as well as known and previously unidentified ErbB inhibitors. Sensitivity analysis identified ErbB3 as the key node in response to ligands that can bind either ErbB3 or EGFR (epidermal growth factor receptor). We describe MM-121, a human monoclonal antibody that halts the growth of tumor xenografts in mice and, consistent with model-simulated inhibitor data, potently inhibits ErbB3 phosphorylation in a manner distinct from that of other ErbB-targeted therapies. MM-121, a previously unidentified anticancer therapeutic designed using a systems approach, promises to benefit patients with combinatorial, ligand-induced activation of the ErbB signaling network that are not effectively treated by current therapies targeting overexpressed or mutated oncogenes.

Loss of Phosphatase and Tensin homologue deleted on chromosome 10 engages ErbB3 and insulin-like growth factor-I receptor signaling to promote antiestrogen resistance in breast cancer

Knockdown of the tumor suppressor phosphatase Phosphatase and tensin homologue deleted on chromosome 10 (PTEN) with shRNA in three estrogen receptor (ER)-positive breast cancer cell lines resulted in increased phosphatidylinositol-3 kinase (PI3K) and AKT activities, resistance to tamoxifen and fulvestrant, and hormone-independent growth. PTEN knockdown induced the up-regulation of ER transcriptional activity in MCF-7 cells but decreased ER protein levels and transcriptional activity in T47D and MDA-361 cells. Tamoxifen and fulvestrant treatment inhibited estradiol-induced ER transcriptional activity in all shPTEN cell lines but did not abrogate the increased cell proliferation induced by PTEN knockdown. PTEN knockdown increased basal and ligand-induced activation of the insulin-like growth factor-I (IGF-I) and ErbB3 receptor tyrosine kinases, and prolonged the association of the p85 PI3K subunit with the IGF-I receptor (IGF-IR) effector insulin receptor substrate-1 and with ErbB3, implicating PTEN in the modulation of signaling upstream of PI3K. Consistent with these data, PTEN levels inversely correlated with levels of tyrosine-phosphorylated IGF-IR in tissue lysate arrays of primary breast cancers. Inhibition of IGF-IR and/or ErbB2-mediated activation of ErbB3 with tyrosine kinase inhibitors restored hormone dependence and the growth inhibitory effect of tamoxifen and fulvestrant on shPTEN cells, suggesting that cotargeting both ER and receptor tyrosine kinase pathways holds promise for the treatment of patients with ER+, PTEN-deficient breast cancers.

Signal co-operation between integrins and other receptor systems

The multicellular nature of metazoans means that all cellular processes need to be tuned by adhesive interactions between cells and their local microenvironment. The spatial organization of cells within tissues requires sophisticated networks of extracellular signals to control their survival and proliferation, movements and positioning, and differentiated function. These cellular characteristics are mediated by multiple inputs from adhesion systems in combination with soluble and developmental signals. In the present review we explore how one class of adhesion receptor, the integrins, co-operate with other types of receptor to control diverse aspects of cell fate. In particular we discuss: (i) how beta3 and beta1 integrins work together with growth factors to control angiogenesis; (ii) how alpha6beta4 integrin co-operates with receptor tyrosine kinases in normal epithelial function and cancer; (iii) the interplay between beta1 integrins and EGF (epidermal growth factor) receptor; (iv) signal integration connecting integrins and cytokine receptors for interleukins, prolactin and interferons; and (v) how integrins and syndecans co-operate in cell migration.

Cooperation between integrin alphavbeta3 and VEGFR2 in angiogenesis

The cross-talk between receptor tyrosine kinases and integrin receptors are known to be crucial for a number of cellular functions. On endothelial cells, an interaction between integrin alphavbeta3 and VEGFR2 seems to be particularly important process during vascularization. Importantly, the functional association between VEGFR2 and integrin alphavbeta3 is of reciprocal nature since each receptor is able to promote activation of its counterpart. This mutually beneficial relationship regulates a number of cellular activities involved in angiogenesis, including endothelial cell migration, survival and tube formation, and hematopoietic cell functions within vasculature. This article discusses several possible mechanisms reported by different labs which mediate formation of the complex between VEGFR-2 and alphavbeta3 on endothelial cells. The pathological consequences and regulatory events involved in this receptor cross-talk are also presented.

Signal co-operation between integrins and other receptor systems

The multicellular nature of metazoans means that all cellular processes need to be tuned by adhesive interactions between cells and their local microenvironment. The spatial organization of cells within tissues requires sophisticated networks of extracellular signals to control their survival and proliferation, movements and positioning, and differentiated function. These cellular characteristics are mediated by multiple inputs from adhesion systems in combination with soluble and developmental signals. In the present review we explore how one class of adhesion receptor, the integrins, co-operate with other types of receptor to control diverse aspects of cell fate. In particular we discuss: (i) how β3 and β1 integrins work together with growth factors to control angiogenesis; (ii) how α6β4 integrin co-operates with receptor tyrosine kinases in normal epithelial function and cancer; (iii) the interplay between β1 integrins and EGF (epidermal growth factor) receptor; (iv) signal integration connecting integrins and cytokine receptors for interleukins, prolactin and interferons; and (v) how integrins and syndecans co-operate in cell migration.

Integrin and growth factor receptor alliance in angiogenesis

A sequence of events in vascular and stromal cells maintained in a highly coordinated manner regulates angiogenesis and tissue remodeling. These processes are mediated by the ability of cells to respond to environmental cues and activate surface integrins. Physiological and pathological processes in vascular biology are dependent on the specificity of important signaling mechanisms that are activated through the association between growth factors, their receptors, integrins, and their specific extracellular matrix ligands. A large body of evidence from in vitro and in vivo models demonstrates the importance of coordination of signals from the extracellular environment that activates specific tyrosine kinase receptors and integrins in order to regulate angiogenic processes in vivo. In addition to complex formation between growth factor receptors and integrins, growth factors and cytokines also directly interact with integrins, depending upon their concentration levels in the environment, and differentially regulate integrin-related processes. Recent studies from a number of laboratories including ours have provided important novel insights into the involvement of many signaling events that improve our existing knowledge on the cross-talk between growth factor receptors and integrins in the regulation of angiogenesis. In this review, our focus will be on updating the recent developments in the field of integrin-growth factor receptor associations and their implications in the vascular processes.

A divergent role for estrogen receptor-beta in node-positive and node-negative breast cancer classified according to molecular subtypes: an observational prospective study

Introduction

Estrogen receptor-alpha (ER-α) and progesterone receptor (PgR) are consolidated predictors of response to hormonal therapy (HT). In contrast, little information regarding the role of estrogen receptor-beta (ER-β) in various breast cancer risk groups treated with different therapeutic regimens is available. In particular, there are no data concerning ER-β distribution within the novel molecular breast cancer subtypes luminal A (LA) and luminal B (LB), HER2 (HS), and triple-negative (TN).

Methods

We conducted an observational prospective study using immunohistochemistry to evaluate ER-β expression in 936 breast carcinomas. Associations with conventional biopathological factors and with molecular subtypes were analyzed by multiple correspondence analysis (MCA), while univariate and multivariate Cox regression analysis and classification and regression tree analysis were applied to determine the impact of ER-β on disease-free survival in the 728 patients with complete follow-up data.

Results

ER-β evenly distributes (55.5%) across the four molecular breast cancer subtypes, confirming the lack of correlation between ER-β and classical prognosticators. However, the relationships among the biopathological factors, analyzed by MCA, showed that ER-β positivity is located in the quadrant containing more aggressive phenotypes such as HER2 and TN or ER-α/PgR/Bcl2^- tumors. Kaplan-Meier curves and Cox regression analysis identified ER-β as a significant discriminating factor for disease-free survival both in the node-negative LA (P = 0.02) subgroup, where it is predictive of response to HT, and in the node-positive LB (P = 0.04) group, where, in association with PgR negativity, it conveys a higher risk of relapse.

Conclusion

Our data indicated that, in contrast to node-negative patients, in node-positive breast cancer patients, ER-β positivity appears to be a biomarker related to a more aggressive clinical course. In this context, further investigations are necessary to better assess the role of the different ER-β isophorms.