Imatinib mesylate (Gleevec) in advanced breast cancer-expressing C-Kit or PDGFR-beta: clinical activity and biological correlations

Potential therapeutic targets of the JAK2/STAT3 signaling pathway in triple-negative breast cancer

Triple-negative breast cancer (TNBC) poses a significant clinical challenge due to its propensity for metastasis and poor prognosis. TNBC evades the body's immune system recognition and attack through various mechanisms, including the Janus Kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) signaling pathway. This pathway, characterized by heightened activity in numerous solid tumors, exhibits pronounced activation in specific TNBC subtypes. Consequently, targeting the JAK2/STAT3 signaling pathway emerges as a promising and precise therapeutic strategy for TNBC. The signal transduction cascade of the JAK2/STAT3 pathway predominantly involves receptor tyrosine kinases, the tyrosine kinase JAK2, and the transcription factor STAT3. Ongoing preclinical studies and clinical research are actively investigating this pathway as a potential therapeutic target for TNBC treatment. This article comprehensively reviews preclinical and clinical investigations into TNBC treatment by targeting the JAK2/STAT3 signaling pathway using small molecule compounds. The review explores the role of the JAK2/STAT3 pathway in TNBC therapeutics, evaluating the benefits and limitations of active inhibitors and proteolysis-targeting chimeras in TNBC treatment. The aim is to facilitate the development of novel small-molecule compounds that target TNBC effectively. Ultimately, this work seeks to contribute to enhancing therapeutic efficacy for patients with TNBC.

KIT genetic alterations in breast cancer

AIMS

Activating somatic mutations or gene amplification of KIT result in constitutive activation of its receptor tyrosine kinase, which is targetable in various solid tumours. Here, we sought to investigate the presence of KIT genetic alterations in breast cancer (BC) and characterise the histological and genomic features of these tumours.

METHODS

A retrospective analysis of 5,575 BCs previously subjected to targeted sequencing using the FDA-authorised Memorial Sloan Kettering-Integrated Mutation Profiling of Actionable Targets (MSK-IMPACT) assay was performed to identify BCs with KIT alterations. A histological assessment of KIT-altered BCs was conducted, and their repertoire of genetic alterations was compared with that of BCs lacking KIT genetic alterations, matched for age, histological type, oestrogen receptor/HER2 status and sample type.

RESULTS

We identified 18 BCs (0.32%), including 9 primary and 9 metastatic BCs, with oncogenic/likely oncogenic genetic alterations affecting KIT, including activating somatic mutations (n=4) or gene amplification (n=14). All KIT-altered BCs were of high histological grade, although no distinctive histological features were observed. When compared with BCs lacking KIT genetic alterations, no distinctive genetic features were identified. In two metastatic KIT-altered BCs in which the matched primary BC had also been analysed by MSK-IMPACT, the KIT mutations were found to be restricted to the metastatic samples, suggesting that they were late events in the evolution of these cancers.

CONCLUSIONS

KIT genetic alterations are vanishingly rare in BC. KIT-altered BCs are of high grade but lack distinctive histological features. Genetic alterations in KIT might be late events in the evolution and/or progression of BC.

Analysis of CD74 Occurrence in Oncogenic Fusion Proteins

CD74 is a type II cell surface receptor found to be highly expressed in several hematological and solid cancers, due to its ability to activate pathways associated with tumor cell survival and proliferation. Over the past 16 years, CD74 has emerged as a commonly detected fusion partner in multiple oncogenic fusion proteins. Studies have found CD74 fusion proteins in a range of cancers, including lung adenocarcinoma, inflammatory breast cancer, and pediatric acute lymphoblastic leukemia. To date, there are five known CD74 fusion proteins, CD74-ROS1, CD74-NTRK1, CD74-NRG1, CD74-NRG2α, and CD74-PDGFRB, with a total of 16 different variants, each with unique genetic signatures. Importantly, the occurrence of CD74 in the formation of fusion proteins has not been well explored despite the fact that ROS1 and NRG1 families utilize CD74 as the primary partner for the formation of oncogenic fusions. Fusion proteins known to be oncogenic drivers, including those of CD74, are typically detected and targeted after standard chemotherapeutic plans fail and the disease relapses. The analysis reported herein provides insights into the early intervention of CD74 fusions and highlights the need for improved routine assessment methods so that targeted therapies can be applied while they are most effective.

Intercellular adhesion molecule-1 (ICAM-1)-targeted near-infrared photoimmunotherapy of triple-negative breast cancer

Triple-negative breast cancer (TNBC) is the most aggressive subtype of breast cancer and conventional chemotherapy and molecular-targeted therapies show limited efficacy. Near-infrared photoimmunotherapy (NIR-PIT) is a new anti-cancer treatment that selectively damages the cell membrane of cancer cells based on NIR light-induced photochemical reactions of the antibody-photoabsorber (IRDye700Dx) conjugate and the cell membrane. TNBC is known to express several adhesion molecules on the cell surface providing a potential new target for therapy. Here, we investigated the therapeutic efficacy of Intercellular adhesion molecule-1 (ICAM-1)-targeted NIR-PIT using xenograft mouse models subcutaneously inoculated with two human ICAM-1-expressing TNBC cell lines MDAMB468-luc and MDAMB231 cells. In vitro ICAM-1-targeted NIR-PIT damaged both cell types in a light dose-dependent manner. In vivo ICAM-1-targeted NIR-PIT in both models showed early histological signs of cancer cell damage such as cytoplasmic vacuolation. Even among the cancer cells that appeared to be morphologically intact within 2 hours post treatment, abnormal distribution of the actin cytoskeleton and a significant decrease in Ki-67 positivity were observed, indicating widespread cellular injury reflected in cytoplasmic degeneration. Such damage to cancer cells by NIR-PIT significantly inhibited subsequent tumor growth and improved survival. This study suggests that ICAM-1-targeted NIR-PIT may have potential clinical application in the treatment of TNBC.

Effect of imatinib on oral wound healing after extraction: A rare case report

BACKGROUND

Proper tissue repair and healing after oral surgery are vital to achieve optimal outcomes. Certain medications may interfere with wound healing, but this debilitating adverse drug reaction is often not reported in the literature. It is unknown whether imatinib (Gleevec; Novartis Pharmaceuticals) interferes with gingival healing after oral surgery.

CASE DESCRIPTION

A 58-year-old man with a dislodged crown and core buildup of tooth no. 19 sought treatment at a prosthodontic clinic. After examination, the patient consented to extraction, ridge preservation, and future implant placement. He had previous surgical resection of a gastrointestinal stromal tumor and was taking 400 mg of imatinib daily. After extraction and ridge preservation, delayed soft-tissue healing and loss of the coronal portion of bone graft were observed at 8 weeks after surgery. Delayed wound healing was observed again after revision surgery. After imatinib therapy was paused, the adverse effect subsided and the wound healed properly. On the basis of causality assessment and clinical judgment, the authors determined that imatinib was the probable cause of this adverse drug reaction. To their best knowledge, this is the first report of delayed gingival healing after oral surgery secondary to imatinib.

PRACTICAL IMPLICATIONS

Dental practitioners should consider the possibility of impaired healing among their patients taking imatinib, especially before procedures that damage gingival tissue, although this adverse drug reaction is not reported in the drug's package insert. Consult with the patient's oncologist is advised before dental manipulations; temporary discontinuation (or dose reductions) of imatinib may be warranted until wounded tissue heals properly.

Diverse roles of tumor-stromal PDGFB-to-PDGFRβ signaling in breast cancer growth and metastasis

Over the last couple of decades, it has become increasingly apparent that the tumor microenvironment (TME) mediates every step of cancer progression and solid tumors are only able to metastasize with a permissive TME. This intricate interaction of cancer cells with their surrounding TME, or stroma, is becoming more understood with an ever greater knowledge of tumor-stromal signaling pairs such as platelet-derived growth factors (PDGF) and their cognate receptors. We and others have focused our research efforts on understanding how tumor-derived PDGFB activates platelet-derived growth factor receptor beta (PDGFRβ) signaling specifically in the breast cancer TME. In this chapter, we broadly discuss PDGF and PDGFR expression patterns and signaling in normal physiology and breast cancer. We then detail the expansive roles played by the PDGFB-to-PDGFRβ signaling pathway in modulating breast tumor growth and metastasis with a focus on specific cellular populations within the TME, which are responsive to tumor-derived PDGFB. Given the increasingly appreciated importance of PDGFB-to-PDGFRβ signaling in breast cancer progression, specifically in promoting metastasis, we end by discussing how therapeutic targeting of PDGFB-to-PDGFRβ signaling holds great promise for improving current breast cancer treatment strategies.

Effects of tyrosine kinase inhibitors on androgen, estrogen α, glucocorticoid and thyroid receptors

Modern anticancer therapies favor a targeted approach. Tyrosine kinase inhibitors (TKIs) are drugs that target molecular pathways involved in various types of malignancies. Although TKIs are safe and well tolerated, they remain not completely selective; e.g., endocrine-mediated adverse events have been observed with their use. In the present study, the effects of seven TKIs were determined on the activities of androgen receptor, estrogen receptor α (ERα), glucocorticoid receptor and thyroid receptor in vitro using stably transfected cell lines expressing firefly luciferase reporter gene: AR-EcoScreen, hERα-HeLa9903, MDA-kb2, and GH3.TRE-Luc cells, respectively. Antiandrogenic activity was seen for erlotinib, estrogenic activity for imatinib, antiestrogenic activity for dasatinib, erlotinib, nilotinib, regorafenib and sorafenib, glucocorticoid activity for erlotinib and ibrutinib, antiglucocorticoid activity for regorafenib and sorafenib, and antithyroid activity for ibrutinib. Additionally, synergism was seen for 1-5 μM dasatinib and 500 nM hydrocortisone combination for glucocorticoid activity in MDA-kb2 cells. The estrogenic activity of imatinib was confirmed as mediated through ERα, and interference of the TKIs with the reporter gene assays was ruled out in a cell-lysate-based firefly luciferase enzyme inhibition assay. Imatinib in combination with 4-hydroxytamoxifen showed concentration-dependent effects on the metabolic activity of ERα-expressing AN3CA, MCF-7, and SKOV3 cells, and on cell proliferation and adhesion of MCF-7 cells. These findings contribute to the understanding of the endocrine effects of TKIs, in terms of toxicity and effectiveness, and define the need to further evaluate the endocrine disrupting activities of TKIs to safeguard human and environmental health.

ABL allosteric inhibitors synergize with statins to enhance apoptosis of metastatic lung cancer cells

Targeting mitochondrial metabolism has emerged as a treatment option for cancer patients. The ABL tyrosine kinases promote metastasis, and enhanced ABL signaling is associated with a poor prognosis in lung adenocarcinoma patients. Here we show that ABL kinase allosteric inhibitors impair mitochondrial integrity and decrease oxidative phosphorylation. To identify metabolic vulnerabilities that enhance this phenotype, we utilized a CRISPR/Cas9 loss-of-function screen and identified HMG-CoA reductase, the rate-limiting enzyme of the mevalonate pathway and target of statin therapies, as a top-scoring sensitizer to ABL inhibition. Combination treatment with ABL allosteric inhibitors and statins decreases metastatic lung cancer cell survival in vitro in a synergistic manner. Notably, combination therapy in mouse models of lung cancer brain metastasis and therapy resistance impairs metastatic colonization with a concomitant increase in animal survival. Thus, metabolic combination therapy might be effective to decrease metastatic outgrowth, leading to increased survival for lung cancer patients with advanced disease.

Metabolic reprogramming in tumors is an adaptation that generates vulnerabilities that can be exploited for developing new therapies. Here Luttman et al. identify synergism between ABL allosteric inhibitors and lipophilic statins to impair metastatic lung cancer cell outgrowth and colonization, leading to increased survival in mouse models of advanced disease.

In Silico Targeting Human Multidrug Transporter ABCG2 in Breast Cancer: Database Screening, Molecular Docking, and Molecular Dynamics Study

ABCG2 is a substantial member of the ABC transporter superfamily that plays a significant role in multidrug resistance in cancer. Until recently, the 3D structure of ABCG2 has not been resolved, which resulted in the limitation of developing potential ABCG2 inhibitors using structure-based drug discovery. Herein, eMolecules, ChEMBL, and ChEBI databases, containing >25 million compounds, were virtually screened against the ABCG2 transporter in homodimer form. Performance of AutoDock4.2.6 software to predict inhibitor-ABCG2 binding mode and affinity were validated on the basis of available experimental data. The explored databases were filtered based on docking scores. The most potent hits with binding affinities higher than that of experimental bound ligand (MZ29) were then selected and subjected to molecular mechanics minimization, followed by binding energy calculation using molecular mechanics-generalized Born surface area (MM-GBSA) approach. Furthermore, molecular dynamics simulations for 50 ns, followed by MM-GBSA binding energy calculations, were performed for the promising compounds, unveiling eight potential inhibitors with binding affinities <-55.8 kcal/mol. Structural and energetic analyses demonstrated the stability of the eight identified inhibitors over the 50 ns MD simulation. This research sheds light on the potentiality of the identified ABCG2 inhibitors as a therapeutic approach to overcome multidrug resistance cancer therapy.

Targeting CD82/KAI1 for Precision Therapeutics in Surmounting Metastatic Potential in Breast Cancer

Metastasis is the main cause of mortality in breast cancer patients. There is an unmet need to develop therapies that can impede metastatic spread. Precision oncology has shown great promise for the treatment of cancers, as the therapeutic approach is tailored to a specific group of patients who are likely to benefit from the treatment, rather than the traditional approach of "one size fits all". CD82, also known as KAI1, a glycoprotein belonging to the tetraspanin family and an established metastasis suppressor, could potentially be exploited to hinder metastases in breast cancer. This review explores the prospect of targeting CD82 as an innovative therapeutic approach in precision medicine for breast cancer patients, with the goal of preventing cancer progression and metastasis. Such an approach would entail the selection of a subset of breast cancer patients with low levels of CD82, and instituting an appropriate treatment scheme tailored towards restoring the levels of CD82 in this group of patients. Proposed precision treatment regimens include current modalities of treating breast cancer, in combination with either clinically approved drugs that could restore the levels of CD82, CD82 peptide mimics or non-coding RNA-based therapeutics.

Role of the ABL tyrosine kinases in the epithelial-mesenchymal transition and the metastatic cascade

The ABL kinases, ABL1 and ABL2, promote tumor progression and metastasis in various solid tumors. Recent reports have shown that ABL kinases have increased expression and/or activity in solid tumors and that ABL inactivation impairs metastasis. The therapeutic effects of ABL inactivation are due in part to ABL-dependent regulation of diverse cellular processes related to the epithelial to mesenchymal transition and subsequent steps in the metastatic cascade. ABL kinases target multiple signaling pathways required for promoting one or more steps in the metastatic cascade. These findings highlight the potential utility of specific ABL kinase inhibitors as a novel treatment paradigm for patients with advanced metastatic disease. Video abstract.

Tumor Microenvironment-Associated Pericyte Populations May Impact Therapeutic Response in Thyroid Cancer

Thyroid cancer is the most common endocrine malignancy, and aggressive radioactive iodine refractory thyroid carcinomas still lack an effective treatment. A deeper understanding of tumor heterogeneity and microenvironment will be critical to establishing new therapeutic approaches. One of the important influencing factors of tumor heterogeneity is the diversity of cells in the tumor microenvironment. Among these are pericytes, which play an important role in blood vessel stability and angiogenesis, as well as tumor growth and metastasis. Pericytes also have stem cell-like properties and are a heterogeneous cell population, and their lineage, which has been challenging to define, may impact tumor resistance at different tumor stages. Pericytes are also important stroma cell types in the angiogenic microenvironment which express tyrosine-kinase (TK) pathways (e.g., PDGFR-β). Although TK inhibitors (TKI) and BRAF^V600E inhibitors are currently used in the clinic for thyroid cancer, their efficacy is not durable and drug resistance often develops. Characterizing the range of distinct pericyte populations and distinguishing them from other perivascular cell types may enable the identification of their specific functions in the thyroid carcinoma vasculature. This remains an essential step in developing new therapeutic strategies. Also, assessing whether thyroid tumors hold immature and/or mature vasculature with pericyte populations coverage may be key to predicting tumor response to either targeted or anti-angiogenesis therapies. It is also critical to apply different markers in order to identify pericyte populations and characterize their cell lineage. This chapter provides an overview of pericyte ontogenesis and the lineages of diverse cell populations. We also discuss the role(s) and targeting of pericytes in thyroid carcinoma, as well as their potential impact on precision targeted therapies and drug resistance.

Aptamer targeted therapy potentiates immune checkpoint blockade in triple-negative breast cancer

BACKGROUND

Triple-negative breast cancer (TNBC) is a uniquely aggressive cancer with high rates of relapse due to resistance to chemotherapy. TNBC expresses higher levels of programmed cell death-ligand 1 (PD-L1) compared to other breast cancers, providing the rationale for the recently approved immunotherapy with anti-PD-L1 monoclonal antibodies (mAbs). A huge effort is dedicated to identify actionable biomarkers allowing for combination therapies with immune-checkpoint blockade. Platelet-derived growth factor receptor β (PDGFRβ) is highly expressed in invasive TNBC, both on tumor cells and tumor microenvironment. We recently proved that tumor growth and lung metastases are impaired in mouse models of human TNBC by a high efficacious PDGFRβ aptamer. Hence, we aimed at investigating the effectiveness of a novel combination treatment with the PDGFRβ aptamer and anti-PD-L1 mAbs in TNBC.

METHODS

The targeting ability of the anti-human PDGFRβ aptamer toward the murine receptor was verified by streptavidin-biotin assays and confocal microscopy, and its inhibitory function by transwell migration assays. The anti-proliferative effects of the PDGFRβ aptamer/anti-PD-L1 mAbs combination was assessed in human MDA-MB-231 and murine 4 T1 TNBC cells, both grown as monolayer or co-cultured with lymphocytes. Tumor cell lysis and cytokines secretion by lymphocytes were analyzed by LDH quantification and ELISA, respectively. Orthotopic 4 T1 xenografts in syngeneic mice were used for dissecting the effect of aptamer/mAb combination on tumor growth, metastasis and lymphocytes infiltration. Ex vivo analyses through immunohistochemistry, RT-qPCR and immunoblotting were performed.

RESULTS

We show that the PDGFRβ aptamer potentiates the anti-proliferative activity of anti-PD-L1 mAbs on both human and murine TNBC cells, according to its human/mouse cross-reactivity. Further, by binding to activated human and mouse lymphocytes, the aptamer enhances the anti-PD-L1 mAb-induced cytotoxicity of lymphocytes against tumor cells. Importantly, the aptamer heightens the antibody efficacy in inhibiting tumor growth and lung metastases in mice. It acts on both tumor cells, inhibiting Akt and ERK1/2 signaling pathways, and immune populations, increasing intratumoral CD8 + T cells and reducing FOXP3 + Treg cells.

CONCLUSION

Co-treatment of PDGFRβ aptamer with anti-PD-L1 mAbs is a viable strategy, thus providing for the first time an evidence of the efficacy of PDGFRβ/PD-L1 co-targeting combination therapy in TNBC.

Stromal CCL2 Signaling Promotes Mammary Tumor Fibrosis through Recruitment of Myeloid-Lineage Cells

Obesity is correlated with breast tumor desmoplasia, leading to diminished chemotherapy response and disease-free survival. Obesity causes chronic, macrophage-driven inflammation within breast tissue, initiated by chemokine ligand 2 (CCL2) signaling from adipose stromal cells. To understand how CCL2-induced inflammation alters breast tumor pathology, we transplanted oncogenically transformed human breast epithelial cells with breast stromal cells expressing CCL2 or empty vector into murine mammary glands and examined tumor formation and progression with time. As tumors developed, macrophages were rapidly recruited, followed by the emergence of cancer-associated fibroblasts (CAFs) and collagen deposition. Depletion of CD11b + myeloid lineage cells early in tumor formation reduced tumor growth, CAF numbers, and collagen deposition. CCL2 expression within developing tumors also enhanced recruitment of myeloid progenitor cells from the bone marrow into the tumor site. The myeloid progenitor cell population contained elevated numbers of fibrocytes, which exhibited platelet-derived growth factor receptor-alpha (PDGFRα)-dependent colony formation and growth in vitro. Together, these results suggest that chronic inflammation induced by CCL2 significantly enhances tumor growth and promotes the formation of a desmoplastic stroma through early recruitment of macrophages and fibrocytes into the tumor microenvironment. Fibrocytes may be a novel target in the tumor microenvironment to reduce tumor fibrosis and enhance treatment responses for obese breast cancer patients.

Enhanced anticancer activity of combined treatment of imatinib and dipyridamole in solid Ehrlich carcinoma-bearing mice

The current study was designed to evaluate potential enhancement of the anticancer activity of imatinib mesylate (IM) with dipyridamole (DIP) and to investigate the underlying mechanisms of the combined therapy (IM/DIP) to reduce hepatotoxicity of IM in solid Ehrlich carcinoma (SEC)-bearing mice. SEC was induced in female albino mice as a model for experimentally induced breast cancer. Mice were randomly divided into seven groups (n = 10): SEC vehicle, IM₅₀ (50 mg/kg), IM₁₀₀ (100 mg/kg), DIP (35 mg/kg), a combination of IM₅₀/DIP and IM₁₀₀/DIP. On day 28th, mice were sacrificed and blood samples were collected for hematological studies. Biochemical determination of liver markers was evaluated. Glutamic oxaloacetic transaminase (SGOT), glutamic pyruvic transaminase (SGPT) and alkaline phosphatase (ALP) levels were assessed. In addition, MDR-1 gene expression and immunohistochemical staining of BAX and BCL-2 was done. Also, in vitro experiment for determination of IC50 of different treatments and combination index (CI) were assessed in both MCF-7 and HCT-116 cell lines. IM- and/or DIP-treated groups showed a significant reduction in tumor volume, weight, and serum levels of SGOT, SGPT, and AIP compared to vehicle group. In addition, reduction of VEGF, Ki67, and adenosine contents was also reported by treated groups. Also, IM/DIP combination showed lower IC50 than monotherapy. Combination index is less than 1 for IM/DIP combination in both cell lines. DIP as an adjuvant therapy potentiated the cytotoxic effect of IM, ameliorated its hepatic toxicity, and showed synergistic effect with IM in vitro cell lines. Furthermore, the resistance against IM therapy may be overcome by the use of DIP independent on mdr-1 gene expression.

Vascular targeted photodynamic therapy: A review of the efforts towards molecular targeting of tumor vasculature

The therapeutic value of vascular targeted photodynamic therapy (VTP) for cancer has already been recognized in the clinic: TOOKAD® has been clinically approved in Europe and Israel for treatment of men with low-risk prostate cancer. When light is applied shortly after intravenous administration of the photosensitizer, the damage is primarily done to the vasculature. This results in vessel constriction, blood flow stasis, and thrombus formation. Subsequently, the tumor is killed due to oxygen and nutrient deprivation. To further increase treatment specificity and to reduce undesired side effects such as damaging to the surrounding healthy tissues, efforts have been made to selectively target the PS to the tumor vasculature, an approach named molecular targeted VTP (molVTP). Several receptors have already been explored for this approach, namely CD13, CD276, Extra domains of fibronectin (A, B), Integrin αvβ3, Neuropilin-1, Nucleolin, PDGFRβ, tissue factor, and VEGFR-2, which are overexpressed on tumor vasculature. Preclinical studies have shown promising results, further encouraging the investigation and future application of molVTP, to improve selectivity and efficacy of cancer treatment. This strategy will hopefully lead to even more selective treatments for many cancer patients.

Essential oil extracted from erythrina corallodendron L. leaves inhibits the proliferation, migration, and invasion of breast cancer cells

Erythrina corallodendron L., a kind of landscape tree, has long been used as a traditional medicine. In this study, the composition of essential oil extracted from the leaves was analysed by GC-MS (gas chromatograph-mass spectrometer), with linalool identified as the main compound. Its cytotoxicity against MDA-MB-231, MCF-7 and HMLE cells was examined by MTT and cloning assays. Transwell and wound-healing assays were used to examine the inhibition of migration and invasion. Western blot, qRT-PCR and immunofluorescence staining were used to measure the mRNA and protein expression of factors related to EMT (snail, slug, E-cadherin, N-cadherin and vimentin). The essential oil of Erythrina corallodendron leaves was found to inhibit the proliferation, migration and invasion of breast cancer cells in a dose-dependent manner. The findings of this study suggest that the essential oil of E. corallodendron leaves may merit further investigation as a potential clinical or adjuvant drug for treating breast cancer migration and invasion.

Deregulation of VEGFR-2 and PDGFR Expression and Microvascular Density in a Triple-Negative Model of Canine Malignant Mammary Tumors with Lymph Node or Lung Metastasis

Canine mammary tumors (CMT) represent the most common cancer in noncastrated female dogs. Interestingly, triple-negative tumors are the most common molecular subtype in female dogs. In this study, we proposed to evaluate the expression of vascular endothelial growth factor receptor 2 (VEGFR-2), Platelet-derived growth factor receptor (PDGFR), and microvascular density (MVD) in a group of metastatic and nonmetastatic triple-negative CMT and compare the expression based on clinical parameters. Twenty-six female dogs with triple-negative mammary tumors were divided into three groups: nonmetastatic tumors (NMT) (n = 11), tumors with lymph node metastasis (LNM) (n = 10), and tumors with lung metastasis (LM) (n = 5). We observed increased VEGFR-2 expression in LNM compared with NMT and a positive correlation between tumor grade and VEGFR-2 expression. A positive correlation was noted between VEGFR-2 and PDGFR expression. Regarding microvascular density (MVD), we identified a higher number of vessels in primary tumors with lymph node metastasis and lung metastasis compared with tumors with no metastasis. The primary tumors with lung metastasis exhibited an increased MVD compared with carcinoma with lymph node metastasis. Overall, our results suggest a deregulation of VEGFR-2 and PDGFR and high MVD in metastatic tumors, indicating a role for angiogenesis in tumor progression.

Expression of RET is associated with Oestrogen receptor expression but lacks prognostic significance in breast cancer

BACKGROUND

The Rearranged during Transfection (RET) protein is overexpressed in a subset of Estrogen Receptor (ER) positive breast cancer, with both signalling pathways functionally interacting. This cross-talk plays a pivotal role in the resistance of breast cancer cells to anti-endocrine therapies, and RET expression is assumed to correlate with poor prognosis based on findings in small patient cohorts. The aim of our study was to investigate the impact of RET expression on patient outcome in human breast cancer.

METHODS

We performed an immunohistochemical analysis of RET protein expression on a tissue microarray encompassing 990 breast cancer patients and correlated its expression with clinicopathological parameters and survival data.

RESULTS

Expression of RET was detected in 409 out of 990 cases (41.3%). RET and ER expression significantly correlated (p < 0.0001). The Luminal B HER2-positive subtype showed the highest expression rate (48.9%). In univariate and multivariate survival analyses, RET expression had no impact on overall survival.

CONCLUSION

We confirmed the co-expression of RET and ER, but we did not find RET expression to be an independent prognostic factor in human breast cancer. Clinical trials with newly developed RET inhibitors are needed to evaluate if RET inhibition has a beneficial impact on patient survival in ER positive breast cancer.

Targeted imaging and inhibition of triple-negative breast cancer metastases by a PDGFRβ aptamer

While the overall mortality for breast cancer has recently declined, management of triple-negative breast cancer (TNBC) is still challenging because of its aggressive clinical behavior and the lack of targeted therapies. Genomic profiling studies highlighted the high level of heterogeneity of this cancer, which comprises different subtypes with unique phenotypes and response to treatment. Platelet-derived growth factor receptor β (PDGFRβ) is an established mesenchymal/stem cell-specific marker in human glioblastoma and, as recently suggested, it may uniquely mark breast cancer cells with stem-like characteristics and/or that have undergone epithelial-mesenchymal transition.

Methods: Immunohistochemical analysis for PDGFRβ expression was performed on a human TNBC tissue microarray. Functional assays were conducted on mesenchymal-like TNBC cells to investigate the effect of a previously validated PDGFRβ aptamer on invasive cell growth in three-dimensional culture conditions, migration, invasion and tube formation. The aptamer was labeled with a near-infrared (NIR) dye and its binding specificity to PDGFRβ was assessed both in vitro (confocal microscopy and flow cytometry analyses) and in vivo (fluorescence molecular tomography in mice bearing TNBC xenografts). A mouse model of TNBC lung metastases formation was established and NIR-labeled PDGFRβ aptamer was used to detect lung metastases in mice untreated or intravenously injected with unlabeled aptamer.

Results: Here, we present novel data showing that tumor cell expression of PDGFRβ identifies a subgroup of mesenchymal tumors with invasive and stem-like phenotype, and propose a previously unappreciated role for PDGFRβ in driving TNBC cell invasiveness and metastases formation. We show that the PDGFRβ aptamer blocked invasive growth and migration/invasion of mesenchymal TNBC cell lines and prevented TNBC lung metastases formation. Further, upon NIR-labeling, the aptamer specifically bound to TNBC xenografts and detected lung metastases.

Conclusions: We propose PDGFRβ as a reliable biomarker of a subgroup of mesenchymal TNBCs with invasive and stem-like phenotype as well as the use of the PDGFRβ aptamer as a high efficacious tool for imaging and suppression of TNBC lung metastases. This study will allow for the significant expansion of the current repertoire of strategies for managing patients with more aggressive TNBC.

Temperature-sensitive liposomes for co-delivery of tamoxifen and imatinib for synergistic breast cancer treatment

Co-delivery of chemotherapeutic agents using nanocarriers is a promising strategy for enhancing therapeutic efficacy of anticancer agents. The aim of this work was to develop tamoxifen and imatinib dual drug loaded temperature-sensitive liposomes to treat breast cancer. Liposomes were prepared using 1, 2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), monopalmitoyl-2-hydroxy-sn-glycero-3-phosphocholine (MPPC), and different surface active agents. The liposomes were characterized for the average particle size, zeta potential, transition temperature, and drug release below and above liposomal transition temperature. The temperature-sensitive liposomes co-encapsulated with tamoxifen and imatinib were investigated for their synergistic activity against MCF-7 and MDA-MB-231 breast cancer cells. The liposomal nanoparticles showed a transition temperature of 39.4 °C and >70% encapsulation efficiency for tamoxifen and imatinib. The temperature-responsive liposomes showed more than 80% drug released within 30 min above transition temperature. Dual drug loaded liposomes showed synergistic growth inhibition against MCF-7 and MDA-MB-231 breast cancer cells. Co-delivery of tamoxifen and imatinib using temperature-sensitive liposomes can be developed as a potential targeting strategy against breast cancer.

In vivo phosphoproteomics reveals kinase activity profiles that predict treatment outcome in triple-negative breast cancer

Triple-negative breast cancer (TNBC) lacks prognostic and predictive markers. Here, we use high-throughput phosphoproteomics to build a functional TNBC taxonomy. A cluster of 159 phosphosites is upregulated in relapsed cases of a training set (n = 34 patients), with 11 hyperactive kinases accounting for this phosphoprofile. A mass-spectrometry-to-immunohistochemistry translation step, assessing 2 independent validation sets, reveals 6 kinases with preserved independent prognostic value. The kinases split the validation set into two patterns: one without hyperactive kinases being associated with a >90% relapse-free rate, and the other one showing ≥1 hyperactive kinase and being associated with an up to 9.5-fold higher relapse risk. Each kinase pattern encompasses different mutational patterns, simplifying mutation-based taxonomy. Drug regimens designed based on these 6 kinases show promising antitumour activity in TNBC cell lines and patient-derived xenografts. In summary, the present study elucidates phosphosites and kinases implicated in TNBC and suggests a target-based clinical classification system for TNBC.

Triple-negative breast cancer (TNBC) lacks prognostic and predictive markers. Here, the authors use phosphoproteomics to define kinases with distinct activity profiles in TNBC, demonstrating their prognostic value as well as their utility for simplifying TNBC classification and designing drug regimens.

Application of a novel targeting nanoparticle contrast agent combined with magnetic resonance imaging in the diagnosis of intraductal papillary mucinous neoplasm

Intraductal papillary mucinous neoplasm (IPMN) is a severe disease with macroscopic visible mucin secretion that primarily occurs in biliary tracts or pancreatic ducts. In comparison with standard diagnostic imaging, probing the molecular abnormalities associated with the initial stages of diseases rather than imaging the end effects markedly improves the accuracy of diagnosis. In the present study, magnetic resonance imaging (MRI) in combination with the contrast agent PEGylated magnetoliposome consisting of gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA) and target molecules of IPMN were investigated in the diagnosis of patients with suspected IPMN. The present investigation indicated that the novel targeting nanoparticle contrast agent targeted platelet-derived growth factor receptor-β and RET, and maintained a high affinity with tumor markers located on the IPMN surface. The novel targeting nanoparticle contrast agent combined with MRI exhibited increased sensitivity in diagnosing early-stage patients with IPMN. Furthermore, image quality was improved following the use of the novel targeting nanoparticle contrast agent combined with MRI compared with standard MRI. The targeting nanoparticle contrast agent retained sufficient affinity and was present for an adequate amount of time to observe the tumor mass in papillae using MRI. Notably, the targeting nanoparticle contrast agent was metabolized at 12 h post-injection. In conclusion, these outcomes indicate that the novel targeting nanoparticle contrast agent combined with MRI improved image quality and sensitivity compared with standard MRI, which suggests that this approach may be promising for clinical detection in patients with suspected IPMN.

c-Abl inhibits breast cancer tumorigenesis through reactivation of p53-mediated p21 expression

We previously reported that constitutive c-Abl activity (CST-Abl) abrogates the tumorigenicity of triple-negative breast cancer cells through the combined actions of two cellular events: downregulated matrix metalloproteinase (MMP) and upregulated p21^Waf1/Cip1 expression. We now find decreased c-Abl expression to be significantly associated with diminished relapse-fee survival in breast cancer patients, particularly those exhibiting invasive and basal phenotypes. Moreover, CST-Abl expression enabled 4T1 cells to persist innocuously in the mammary glands of mice, doing so by exhausting their supply of cancer stem cells. Restoring MMP-9 expression and activity in CST-Abl-expressing 4T1 cells failed to rescue their malignant phenotypes; however, rendering these same cells deficient in p21 expression not only delayed their acquisition of senescent phenotypes, but also partially restored their tumorigenicity in mice. Although 4T1 cells lacked detectable expression of p53, those engineered to express CST-Abl exhibited robust production and secretion of TGF-β1 that engendered the reactivated expression of p53. Mechanistically, TGF-β-mediated p53 expression transpired through the combined actions of Smad1/5/8 and Smad2, leading to the dramatic upregulation of p21 and its stimulation of TNBC senescence. Collectively, we identified a novel c-Abl:p53:p21 signaling axis that functions as a powerful suppressor of mammary tumorigenesis and metastatic progression.

Targeting cancer stem cells in the clinic: Current status and perspectives

Resistance to chemotherapy and cancer relapse are major clinical challenges attributed to a sub population of cancer stem cells (CSCs). The concept of CSCs has been the subject of intense research by the oncology community since evidence for their existence was first published over twenty years ago. Emerging data indicates that they are also able to evade novel therapies such as targeted agents, immunotherapies and anti-angiogenics. The inability to appropriately identify and isolate CSCs is a major hindrance to the field and novel technologies are now being utilized. Agents that target CSC-associated cell surface receptors and signaling pathways have generated promising pre-clinical results and are now entering clinical trial. Here we discuss and evaluate current therapeutic strategies to target CSCs.

A Drug Repositioning Approach Reveals that Streptococcus mutans Is Susceptible to a Diverse Range of Established Antimicrobials and Nonantibiotics

Streptococcus mutans is the primary causative agent of dental caries and contributes to the multispecies biofilm known as dental plaque. An adenylate kinase-based assay was optimized for S. mutans to detect cell lysis when exposed to the Selleck library (Selleck Chemical, Houston, TX) of 853 FDA-approved drugs in, to our knowledge, the first high-throughput drug screen in S. mutans We found 126 drugs with activity against S. mutans planktonic cultures, and they were classified into six categories: antibacterials (61), antineoplastics (23), ion channel effectors (9), other antimicrobials (7), antifungals (6), and other (20). These drugs were also tested for activity against S. mutans biofilm cultures, and 24 compounds were found to inhibit biofilm formation, 6 killed preexisting biofilms, 84 exhibited biofilm inhibition and killing activity, and 12 had no activity against biofilms. The activities of 9 selected compounds that exhibited antimicrobial activity were further characterized for their activity against S. mutans planktonic and biofilm cultures. Together, our results suggest that S. mutans exhibits a susceptibility profile to a diverse array of established and novel antibacterials.

Estrogen induces c-Kit and an aggressive phenotype in a model of invasive lobular breast cancer

Among the molecular subtypes of breast cancer are luminal (A or B) estrogen receptor positive (ER+), HER2+, and triple negative (basal-like). In addition to the molecular subtypes, there are 18 histologic breast cancer subtypes classified on appearance, including invasive lobular breast carcinoma (ILC), which are 8-15% of all breast cancers and are largely ER+ tumors. We used a new model of ER+ ILC, called BCK4. To determine the estrogen regulated genes in our ILC model, we examined BCK4 xenograft tumors from mice supplemented with or without estrogen using gene expression arrays. Approximately 3000 genes were regulated by estrogen in vivo. Hierarchical cluster analyses of the BCK4 derived tumors compared with ER+ and ER- breast cancer cell lines show the estrogen treated BCK4 tumors group with ER- breast cancers most likely due to a high proliferation score, while tumors from cellulose supplemented mice were more related to ER+ breast tumor cells. To elucidate genes regulated in vitro by estrogen in BCK4 cells, we performed expression profiling using Illumina arrays of the BCK4 cell line, treated with or without estrogen in vitro. A set of ~200 overlapping genes were regulated by estrogen in the BCK4 cell line and xenograft tumors, and pathway analysis revealed that the c-Kit pathway might be a target to reduce estrogen-induced proliferation. Subsequent studies found that inhibition of c-Kit activity using imatinib mesylate (Gleevec®) blocked estrogen mediated stimulation of BCK4 tumors and BCK4 cells in vitro as effectively as the anti-estrogen fulvestrant (Faslodex®). Decreased expression of c-Kit using shRNA also decreased baseline and estrogen induced proliferation in vitro and in vivo. These studies are the first to indicate that c-Kit inhibition is an effective approach to target c-Kit+ ILC.

Characterization and Targeting of Platelet-Derived Growth Factor Receptor alpha (PDGFRA) in Inflammatory Breast Cancer (IBC)

PURPOSE: Inflammatory breast cancer (IBC) is arguably the deadliest form of breast cancer due to its rapid onset and highly invasive nature. IBC carries 5- and 10-year disease-free survival rates of ~45% and <20%, respectively. Multiple studies demonstrate that in comparison with conventional breast cancer, IBC has a unique molecular identity. Here, we have identified platelet-derived growth factor receptor alpha (PDGFRA) as being uniquely expressed and active in IBC patient tumor cells. EXPERIMENTAL DESIGN: Here we focus on characterizing and targeting PDGFRA in IBC. Using gene expression, we analyzed IBC patient samples and compared them with non-IBC patient samples. Further, using IBC cells in culture, we determined the effect of small molecules inhibitors in both in vitro and in vivo assays. RESULTS: In IBC patients, we show more frequent PDGFRA activation signature than non-IBC samples. In addition, the PDGFRA activation signature is associated with shorter metastasis-free survival in both uni- and multivariate analyses. We also demonstrate that IBC cells express active PDGFRA. Finally, we show that PDGFRA targeting by crenolanib (CP-868-596), but not imatinib (STI571), two small molecule inhibitors, interferes with IBC cell growth and emboli formation in vitro and tumor growth in vivo. CONCLUSIONS: Our data suggest that PDGFRA may be a promising target for therapy in IBC.

Selective Inhibitors of Nuclear Export (SINE) compounds block proliferation and migration of triple negative breast cancer cells by restoring expression of ARRDC3

Arrestin-related domain-containing protein-3 (ARRDC3) is one of 6 mammalian arrestins, which suppresses metastasis by inducing degradation of phosphorylated β2-adrenergic receptor (β2 AR) and integrin β4 (ITG β4). Our previous studies demonstrated that expression of ARRDC3 is epigentically silenced in Triple Negative Breast Cancer (TNBC) cells, and the forced expression of ARRDC3 significantly reduced the invasive potential of TNBC cells. In the current study, we found that Selective Inhibitors of Nuclear Export (SINE) compounds (KPT-185 and selinexor (KPT-330)) restore ARRDC3 expression in TNBC cell lines (MDA-MB-231 and MDA-MB-468) at both the mRNA and protein level in a dose and time course dependent manner. SINE compounds inhibit the proliferation, pro-invasive migration and anchorage independent growth of the TNBC cells by restoring ARRDC3 expression. We found that ARRDC3 expression is lower in TNBC cell lines than those of luminal breast cancer cell lines, and inversely correlated with IC_50s of selinexor. Analysis of tissue microarray confirmed that ARRDC3 expression in patient samples is significantly lower in the majority of TNBC tumors relative to normal tissue. In vivo, selinexor inhibited the tumor growth of MDA-MB-231 xenografts by nearly 100% compared with vehicle treated animals. Furthermore, immunohistochemical analysis of TNBC tumors from selinexor treated mice revealed increased ARRDC3 expression versus vehicle treated animals. Our results suggest that restoration of ARRDC3 expression is an important antineoplastic mechanism of SINE compounds in TNBC, and therefore selinexor could be an effective treatment option for breast tumors with down-regulated ARRDC3.

From Type I to Type II: Design, Synthesis, and Characterization of Potent Pyrazin-2-ones as DFG-Out Inhibitors of PDGFRβ

Reversible protein kinase inhibitors that bind in the ATP cleft can be classified as type I or type II binders. Of these, type I inhibitors address the active form, whereas type II inhibitors typically lock the kinase in an inactive form. At the molecular level, the conformation of the flexible activation loop holding the key DFG motif controls access to the ATP site, thereby determining an active or inactive kinase state. Accordingly, type I and type II kinase inhibitors bind to so-called DFG-in or DFG-out conformations, respectively. Based on our former study on highly selective platelet-derived growth factor receptor β (PDGFRβ) pyrazin-2-one type I inhibitors, we expanded this scaffold toward the deep pocket, yielding the highly potent and effective type II inhibitor 5 (4-[(4-methylpiperazin-1-yl)methyl]-N-[3-[[6-oxo-5-(3,4,5-trimethoxyphenyl)-1H-pyrazin-3-yl]methyl]phenyl]benzamide). In vitro characterization, including selectivity panel data from activity-based assays (300 kinases) and affinity-based assays (97 kinases) of these PDGFRβ type I (1; 5-(4-hydroxy-3-methoxy-phenyl)-3-(3,4,5-trimethoxyphenyl)-1H-pyrazin-2-one) and II (5) inhibitors showing the same pyrazin-2-one chemotype are compared. Implications are discussed regarding the data for selectivity and efficacy of type I and type II ligands.

Extracellular Visfatin-Promoted Malignant Behavior in Breast Cancer Is Mediated Through c-Abl and STAT3 Activation

PURPOSE

Visfatin is an adipocytokine involved in cellular metabolism, inflammation, and cancer. This study investigated the roles of extracellular visfatin in breast cancer, and explored underlying mechanisms in clinical and experimental settings.

EXPERIMENTAL DESIGN

Associations of serum visfatin with clinicopathologic characteristics and patient survival were assessed with Cox regression models and Kaplan-Meier analyses. Effects of extracellular visfatin on cultured breast cancer cells were examined, followed by in vivo investigation of tumor growth and metastasis in xenograft animal models. Imatinib and Stattic were used to inhibit c-Abl and STAT3 activation, respectively.

RESULTS

Breast cancer patients with high serum visfatin levels were associated with advanced tumor stage, increased tumor size and lymph node metastasis, and poor survival. Elevated phosphorylation of c-Abl and STAT3 in breast tumor tissues were correlated with high serum visfatin levels in patients. Visfatin-promoted in vitro cell viability and metastatic capability were suppressed by imatinib (c-Abl inhibitor) and Stattic (STAT3 inhibitor). Increased in vivo cell invasiveness was observed in zebrafish xenografted with visfatin-pretreated breast cancer cells. Tumor growth and lung metastasis occurred in visfatin-administered mice xenografted with breast cancer cells. Tail vein-injected mice with visfatin-pretreated breast cancer cells showed increased lung metastasis, which was suppressed by imatinib.

CONCLUSIONS

Serum visfatin levels in breast cancer patients reveal potential prognostic values, and our findings that visfatin promoted breast cancer through activation of c-Abl and STAT3 may provide an important molecular basis for future design of targeted therapies that take into account different serum visfatin levels in breast cancer. Clin Cancer Res; 22(17); 4478-90. ©2016 AACR.

ABL kinases promote breast cancer osteolytic metastasis by modulating tumor-bone interactions through TAZ and STAT5 signaling

Bone metastases occur in up to 70% of advanced breast cancer. For most patients with breast cancer, bone metastases are predominantly osteolytic. Interactions between tumor cells and stromal cells in the bone microenvironment drive osteolytic bone metastasis, a process that requires the activation of osteoclasts, cells that break down bone. We report that ABL kinases promoted metastasis of breast cancer cells to bone by regulating the crosstalk between tumor cells and the bone microenvironment. ABL kinases protected tumor cells from apoptosis induced by TRAIL (TNF-related apoptosis-inducing ligand), activated the transcription factor STAT5, and promoted osteolysis through the STAT5-dependent expression of genes encoding the osteoclast-activating factors interleukin-6 (IL-6) and matrix metalloproteinase 1 (MMP1). Furthermore, in breast cancer cells, ABL kinases increased the abundance of the Hippo pathway mediator TAZ and the expression of TAZ-dependent target genes that promote bone metastasis. Knockdown of ABL kinases or treatment with ABL-specific allosteric inhibitor impaired osteolytic metastasis of breast cancer cells in mice. These findings revealed a role for ABL kinases in regulating tumor-bone interactions and provide a rationale for using ABL-specific inhibitors to limit breast cancer metastasis to bone.

Promotion of Cancer Stem-Like Cell Properties in Hepatitis C Virus-Infected Hepatocytes

We have previously reported that hepatitis C virus (HCV) infection of primary human hepatocytes (PHH) induces the epithelial mesenchymal transition (EMT) state and extends hepatocyte life span (S. K. Bose, K. Meyer, A. M. Di Bisceglie, R. B. Ray, and R. Ray, J Virol 86:13621-13628, 2012, http://dx.doi.org/10.1128/JVI.02016-12). These hepatocytes displayed sphere formation on ultralow binding plates and survived for more than 12 weeks. The sphere-forming hepatocytes expressed a number of cancer stem-like cell (CSC) markers, including high levels of the stem cell factor receptor c-Kit. The c-Kit receptor is regarded as one of the CSC markers in hepatocellular carcinoma (HCC). Analysis of c-Kit mRNA displayed a significant increase in the liver biopsy specimens of chronically HCV-infected patients. We also found c-Kit is highly expressed in transformed human hepatocytes (THH) infected in vitro with cell culture-grown HCV genotype 2a. Further studies suggested that HCV core protein significantly upregulates c-Kit expression at the transcriptional level. HCV infection of THH led to a significant increase in the number of spheres displayed on ultralow binding plates and in enhanced EMT and CSC markers and tumor growth in immunodeficient mice. The use of imatinib or dasatinib as a c-Kit inhibitor reduced the level of sphere-forming cells in culture. The sphere-forming cells were sensitive to treatment with sorafenib, a multikinase inhibitor, that is used for HCC treatment. Further, stattic, an inhibitor of the Stat3 molecule, induced sphere-forming cell death. A combination of sorafenib and stattic had a significantly stronger effect, leading to cell death. These results suggested that HCV infection potentiates CSC generation, and selected drugs can be targeted to efficiently inhibit cell growth.

IMPORTANCE

HCV infection may develop into HCC as an end-stage liver disease. We focused on understanding the mechanism for the risk of HCC from chronic HCV infection and identified targets for treatment. HCV-infected primary and transformed human hepatocytes (PHH or THH) generated CSC. HCV-induced spheres were highly sensitive to cell death from sorafenib and stattic treatment. Thus, our study is highly significant for HCV-associated HCC, with the potential for developing a target-specific strategy for improved therapies.

Gastrointestinal Stromal Tumors (GIST): A Prospective Analysis and an Update on Biomarkers and Current Treatment Concepts

Gastrointestinal stromal tumors (GIST) are the most common sarcomas of the gastrointestinal tract, with transformation typically driven by activating mutations of cKIT and less commonly platelet-derived growth factor receptor alpha (PDGFRA). Successful targeting of tyrosine-protein kinase Kit with imatinib, a tyrosine kinase inhibitor, has had a major impact in the survival of patients with GIST in both the adjuvant and metastatic setting. A recent modification of treatment guidelines for patients with localized, high-risk GIST extended the adjuvant treatment duration from 1 year to 3 years. In this paper, we review the clinical data of patients with GIST treated in the Oncology Outpatient Unit of "Attikon" University Hospital and aim to assess which patients are eligible for prolongation of adjuvant imatinib therapy as currently suggested by treatment recommendations.

BreastMark: an integrated approach to mining publicly available transcriptomic datasets relating to breast cancer outcome

Introduction

Breast cancer is a complex heterogeneous disease for which a substantial resource of transcriptomic data is available. Gene expression data have facilitated the division of breast cancer into, at least, five molecular subtypes, namely luminal A, luminal B, HER2, normal-like and basal. Once identified, breast cancer subtypes can inform clinical decisions surrounding patient treatment and prognosis. Indeed, it is important to identify patients at risk of developing aggressive disease so as to tailor the level of clinical intervention.

Methods

We have developed a user-friendly, web-based system to allow the evaluation of genes/microRNAs (miRNAs) that are significantly associated with survival in breast cancer and its molecular subtypes. The algorithm combines gene expression data from multiple microarray experiments which frequently also contain miRNA expression information, and detailed clinical data to correlate outcome with gene/miRNA expression levels. This algorithm integrates gene expression and survival data from 26 datasets on 12 different microarray platforms corresponding to approximately 17,000 genes in up to 4,738 samples. In addition, the prognostic potential of 341 miRNAs can be analysed.

Results

We demonstrated the robustness of our approach in comparison to two commercially available prognostic tests, oncotype DX and MammaPrint. Our algorithm complements these prognostic tests and is consistent with their findings. In addition, BreastMark can act as a powerful reductionist approach to these more complex gene signatures, eliminating superfluous genes, potentially reducing the cost and complexity of these multi-index assays. Known miRNA prognostic markers, mir-205 and mir-93, were used to confirm the prognostic value of this tool in a miRNA setting. We also applied the algorithm to examine expression of 58 receptor tyrosine kinases in the basal-like subtype, identifying six receptor tyrosine kinases associated with poor disease-free survival and/or overall survival (EPHA5, FGFR1, FGFR3, VEGFR1, PDGFRβ, and TIE1). A web application for using this algorithm is currently available.

Conclusions

BreastMark is a powerful tool for examining putative gene/miRNA prognostic markers in breast cancer. The value of this tool will be in the preliminary assessment of putative biomarkers in breast cancer. It will be of particular use to research groups with limited bioinformatics facilities.

ICAM-1 as a molecular target for triple negative breast cancer

Triple negative breast cancers (TNBCs) have a high mortality rate owing to aggressive proliferation and metastasis and a lack of effective therapeutic options. Herein, we describe the overexpression of intercellular adhesion molecule-1 (ICAM-1) in human TNBC cell lines and tissues, and demonstrate that ICAM-1 is a potential molecular target and biomarker for TNBC therapy and diagnosis. We synthesized ICAM-1 antibody-conjugated iron oxide nanoparticles (ICAM-IONPs) as a magnetic resonance imaging (MRI) probe to evaluate tumor targeting. Quantitative analysis of ICAM-1 surface expression predicted the targeting capability of ICAM-IONPs to TNBC cells. MRI of the TNBC xenograft tumor after systemic administration of ICAM-IONPs, coupled with iron quantification and histology, demonstrated a significant and sustained MRI contrast enhancement and probe accumulation in tumors with ICAM-1 overexpression relative to control. Identification of ICAM-1 as a TNBC target and biomarker may lead to the development of a new strategy and platform for addressing a critical gap in TNBC patient care.

Final safety and efficacy analysis of a phase I/II trial with imatinib and vinorelbine for patients with metastatic breast cancer

BACKGROUND

Imatinib is a tyrosine kinase inhibitor of BCR-ABL, ABL, PDGFR-α and -β, KIT, and DDR. In solid tumors, it inhibits proliferation and invasiveness and facilitates higher intratumoral cytotoxic drug concentrations. Vinorelbine has good tolerability and efficacy in metastatic breast cancer (MBC). This study evaluates the safety and efficacy of imatinib and vinorelbine in combination.

METHODS

In a prospective, open-label, phase I/II trial, 400 mg imatinib p.o. daily (corrected from 600 mg) was combined with an escalating dose of vinorelbine i.v. weekly in four dose levels of 10, 15, 20, and 25 mg/m(2) (each n ≥ 5) to treat patients with MBC (expressing PDGFR-α and/or -β, and/or KIT). The last patient of each level was treated for >28 days, before enrolment for the next dose level started. Study endpoints were feasibility and tolerability, incidence of hematological and nonhematological toxicity, and clinical efficacy (data cutoff: November 18, 2011). A total of 33 patients have been enrolled, and all dose levels have been fully recruited. One patient is still on study medication. A translational subprotocol is ongoing.

RESULTS

All 33 included patients are evaluable for safety (32 within the ITT population). Eleven patients were excluded early from the study (progressive disease, toxicity, and withdrawal of consent). Twenty-two patients participated in the study for >28 days ('ITT >28'). Within the ITT population, the response rate [complete response (CR) and partial response (PR)] was 9.4% (n = 3), the clinical benefit rate (CBR; CR+PR+stable disease) 50% (n = 16), and the median time to progression (TTP) 155 days. A total of 21.3% of the patients were on study medication for >6 months, and 15.2% for >12 months (mean 140 days, range 15-643). Within 'ITT >28', the response rate was 13.6%, CBR 72.7%, and median TTP 176 days. The response was independent of the receptor status (PDGFR-α, -β, and KIT). Toxicities were as follows (safety population): 21.6% severe leukopenia, 9.1% severe neutropenia (with 1 febrile neutropenia), 1 case of bowel perforation, 36% diarrhea (3% severe), 84.8% nausea (severe 15.2%), 48.5% vomiting (severe 9.1%), 27.3% infections (severe 6.1%), 12.1% peripheral neuropathy (severe 9.1%), and 36.4% dyspnea (3% severe). Four patients on trial died (nondrug-related).

CONCLUSION

The combination of imatinib and vinorelbine in MBC appeared to be feasible and tolerable. A CBR of 50% (ITT) in pretreated patients suggests that this combination may be active. Although toxicities were frequent, they appeared to be manageable.

A phosphotyrosine switch determines the antitumor activity of ERβ

Estrogen receptors ERα and ERβ share considerable sequence homology yet exert opposite effects on breast cancer cell proliferation. While the proliferative role of ERα in breast tumors is well characterized, it is not clear whether the antitumor activity of ERβ can be mobilized in breast cancer cells. Here, we have shown that phosphorylation of a tyrosine residue (Y36) present in ERβ, but not in ERα, dictates ERβ-specific activation of transcription and is required for ERβ-dependent inhibition of cancer cell growth in culture and in murine xenografts. Additionally, the c-ABL tyrosine kinase and EYA2 phosphatase directly and diametrically controlled the phosphorylation status of Y36 and subsequent ERβ function. A nonphosphorylatable, transcriptionally active ERβ mutant retained antitumor activity but circumvented control by upstream regulators. Phosphorylation of Y36 was required for ERβ-mediated coactivator recruitment to ERβ target promoters. In human breast cancer samples, elevated phosphorylation of Y36 in ERβ correlated with high levels of c-ABL but low EYA2 levels. Furthermore, compared with total ERβ, the presence of phosphorylated Y36-specific ERβ was strongly associated with both disease-free and overall survival in patients with stage II and III disease. Together, these data identify a signaling circuitry that regulates ERβ-specific antitumor activity and has potential as both a prognostic tool and a molecular target for cancer therapy.

C-kit and PDGFRA gene mutations in triple negative breast cancer

In this study, we evaluated C-kit immunohistochemical expression and C-kit and platelet derived growth factor receptor A (PDGFRA) gene mutations in triple negative breast cancer. 171 cases were analyzed by immunohistochemical staining for the expression of C-kit and 45 cases, including 10 C-kit negative cases and 35 C-kit positive cases, were performed for C-kit gene mutations in exons 9, 11, 13 and 17 and PDGFRA gene mutations in exons 12 and 18. C-kit expression was detected in 42.1% of triple negative breast cancers. Only 1 activating mutation was detected in exon 11 of C-kit gene in 1 case. No activating mutations were found in the other 44 cases. C-kit expression is a frequent finding in triple negative breast cancers; 1 activating mutation which was also found in gastrointestinal stromal tumors was detected; a few cases might benefit from imatinib.

Investigational platelet-derived growth factor receptor kinase inhibitors in breast cancer therapy

INTRODUCTION

Aberrant regulation of platelet-derived growth factors (PDGFs) and their receptors (PDGFR) has been shown to be involved in many solid tumors, including breast cancer. PDGFR-α and PDGFR-β expressions were documented in breast cancer and are correlated with tumor aggressiveness and metastasis. Preclinical evidence further suggests tumor stimulatory roles of PDGFRs expressed by tumor stroma cells and indicates a deleterious effect of stromal PDGFRs on intratumoral drug uptake.

AREAS COVERED

This review summarizes the present understanding of PDGF signaling in breast cancer based on experimental studies and available clinical trials. It also provides a critical discussion of selected ongoing clinical trials in patients with breast cancer involving PDGFR inhibition with tyrosine kinase inhibitors, specifically in endocrine responsive breast cancer.

EXPERT OPINION

An increased molecular understanding of response and resistance mechanisms to endocrine therapy will be essential for therapeutic advances in PDGFR-directed cancer therapy. Future developments in the field will rely on clinical studies where prospective analyses of target expression in breast cancer cells and in the tumor stroma are included. More selective PDGFR inhibitors with reduced side effects will be crucial for combinatorial therapies. Development of sensitive diagnostics is of critical importance for patient selection and monitoring of therapeutic effects.

The relevance of the TGF-β Paradox to EMT-MET programs

The role of transforming growth factor-β (TGF-β) during tumorigenesis is complex and paradoxical, reflecting its ability to function as a tumor suppressor in normal and early-stage cancers, and as a tumor promoter in their late-stage counterparts. The switch in TGF-β function is known as the "TGF-β Paradox," whose manifestations are intimately linked to the initiation of epithelial-mesenchymal transition (EMT) programs in developing and progressing carcinomas. Indeed, as carcinoma cells emerge from EMT programs stimulated by TGF-β, they readily display a variety of acquired phenotypes that provide a selective advantage to growing carcinomas, including (i) enhanced cell migration and invasion; (ii) heightened resistance to cytotoxic agents, targeted chemotherapeutic, and radiation treatments; and (iv) boosted expansion of cancer-initiating and stem-like cell populations that underlie tumor metastasis and disease recurrence. At present, the molecular, cellular, and microenvironmental mechanisms that enable post-EMT and metastatic carcinoma cells to hijack the oncogenic activities of TGF-β remain incompletely understood. Additionally, the molecular mechanisms that counter EMT programs and limit the aggressiveness of late-stage carcinomas, events that transpire via mesenchymal-epithelial transition (MET) reactions, also need to be further elucidated. Here we review recent advances that provide new insights into how TGF-β promotes EMT programs in late-stage carcinoma cells, as well as how these events are balanced by MET programs during the development and metastatic progression of human carcinomas.

Active kinase profiling, genetic and pharmacological data define mTOR as an important common target in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is an aggressive form of breast cancer. Despite response to chemotherapy, relapses are frequent and resistance to available treatments is often seen in the metastatic setting. Therefore, identification of new therapeutic targets is required. With this aim, we have profiled the activation status of 44 receptor tyrosine kinases (RTKs) and their major signaling pathways in patient-derived TNBC tumors. Frequent co-activation of several RTKs as well as the extracellular signal-regulated protein kinases 1 and 2 (Erk1/2) and mammalian target of rapamycin (mTOR) routes was found. Pharmacologic targeting of the activated kinases indicated that agents that attack the mTOR route are more potent and efficient antitumoral treatments than agents targeting RTKs. mTOR signals through two multiprotein complexes, mTORC1 and mTORC2. We used a genetic approach to explore the contribution of each of the two mTOR branches to the regulation of cell number of TNBC cells. RNA interference experiments indicated that mTORC1 predominated over mTORC2 in the control of TNBC cell proliferation. Moreover, RNA interference of mTOR had a superior antiproliferative action than separately acting on mTORC1 or mTORC2. To analyze the relevance of mTOR targeting in vivo, we used mice with TNBC. Treatment of these mice with BEZ235, a drug that targets mTOR, slowed tumor growth. Mechanistically, BEZ235 delayed cell cycle progression without affecting cell viability. Our results show that TNBCs are particularly sensitive to inhibition of the mTOR pathway, and indicate that mTOR targeting may be a more efficient anti-TNBC therapy than exclusively acting on the mTORC1 branch of the pathway. This is relevant as most mTOR inhibitors used in the clinic act on mTORC1. Collectively with the fact that BEZ235 synergized with drugs commonly used in the treatment of TNBC, our data support the clinical development of agents that act on mTOR as a therapy for this disease.

Soluble KIT correlates with clinical outcome in patients with metastatic breast cancer treated with sunitinib

Background

Sunitinib inhibits vascular endothelial growth factor receptors (VEGFRs), platelet-derived growth factor receptors, and stem cell factor receptor (KIT). The ability of soluble (s)KIT, VEGF-A, sVEGFR-2, and sVEGFR-3 to predict clinical outcome was analyzed in 61 patients with previously treated metastatic breast cancer (MBC) in a phase II study of sunitinib monotherapy (ClinicalTrials.gov NCT00078000).

Methods

Plasma concentrations of soluble proteins were measured at baseline and during treatment with sunitinib 50 mg/day (4 weeks on treatment, 2 weeks off treatment). Baseline concentrations and maximal percent change during the first two treatment cycles were stratified by median values and evaluated for correlation with median time to tumor progression (TTP) and overall survival (OS). This latter fixed time period was chosen to avoid bias accruing from patients who were on study for longer periods of time.

Results

TTP was significantly longer in patients having median or higher maximal percent sKIT change compared with patients with less than the median change (21.7 vs. 7.9 weeks; p < 0.0001). Similarly, OS was significantly longer in patients having median or higher sKIT change versus less than the median change (53.7 vs. 25.7 weeks; p = 0.018). Significant prolongation of OS (62.6 vs. 32.3 weeks; p = 0.032), but not TTP, was observed in patients with a median or higher maximal percent VEGF-A change compared with less than the median change. Maximal percent change of sVEGFR-2 or sVEGFR-3 concentrations and baseline concentrations of all four proteins were not predictive of clinical outcome.

Conclusions

This exploratory analysis suggests that changes in sKIT and possibly VEGF-A early during sunitinib treatment may be predictive of clinical outcome in MBC.

Platelet-derived growth factor (PDGF) induces pulmonary vascular remodeling through 15-LO/15-HETE pathway under hypoxic condition

15-lipoxygenase (15-LO) is known to play an important role in chronic pulmonary hypertension. Accumulating evidence for its down-stream participants in the vasoconstriction and remodeling processes of pulmonary arteries, while how hypoxia regulates 15-LO/15-hydroxyeicosatetraenoic acid (15-HETE) to mediate hypoxic pulmonary hypertension is still unknown. Platelet-derived growth factor (PDGF) is an important vascular regulator whose concentration increases under hypoxic condition in the lungs of both humans and mice with pulmonary hypertension. The present study was carried out to determine whether hypoxia advances the pulmonary vascular remodeling through the PDGF/15-LO/15-HETE pathway. We found that pulmonary arterial medial thickening caused by hypoxia was alleviated after a treatment of the hypoxic rats with imatinib, which was associated with down-regulations of 15-LO-2 expression and 15-HETE production. Moreover, the increases in cell proliferation and endogenous 15-HETE content by hypoxia were attenuated by the inhibitors of PDGF-β receptor in pulmonary artery smooth muscle cells (PASMCs). The effects of PDGF-BB on cell proliferation and survival were weakened after the administration of 15-LO inhibitors or 15-LO RNA interference. These results suggest that hypoxia promotes PASMCs proliferation and survival, contributing to pulmonary vascular medial hypertrophy, which is likely to be mediated via the PDGF-BB/15-LO-2/15-HETE pathway.

Targeting invadopodia to block breast cancer metastasis

Better understanding the mechanisms underlying the metastatic process is essential to developing novel targeted therapeutics. Recently, invadopodia have been increasingly recognized as important drivers of local invasion in metastasis. Invadopodia are basally-localized, actin-rich structures that concentrate protease activity to areas of the cell in contact with the extracellular matrix. We recently found that the transcription factor Twist1, a central regulator of the epithelialmesenchymal transition (EMT), promotes invadopodia formation via upregulation of platelet-derived growth factor receptor (PDGFR) expression and activity. This finding, combined with other investigations into the mechanisms of invadopodia formation, reveal several novel targets for clinical inhibition of invadopodia. Here, we provide an overview of clinically-relevant targets for intervention in invadopodia, including Src signaling, PDGFR signaling, and metalloprotease activity.

Inhibitory effect of soluble platelet-derived growth factor receptor β on intraosseous growth of breast cancer cells in nude mice

Bone metastasis is a frequent complication of advanced breast cancer. On the basis of functional and molecular evidence, signaling mediated by the binding of platelet-derived growth factor (PDGF)-BB and -DD to PDGF receptor β (PDGFRβ) is critical for the survival and growth of metastatic breast cancer cells within the bone microenvironment. In this study, we propose a new approach to blocking PDGFRβ signaling using soluble PDGFRβ (sPDGFRβ) as a decoy receptor for PDGF-BB and -DD secreted from tumor cells and bone marrow stromal cells. A bone-seeking TNBCT/Bo cell line was established by in vivo selection from TNBCT human breast cancer cells, which are negative for estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2 protein expression. The TNBCT/Bo cells were transfected with a mammalian expression vector encoding the extracellular domain of PDGFRβ. A stable transfectant (TNBCT/Bo-sPDGFRβ) grew at a similar rate to that of control cells under normal culture conditions, although growth stimulation of human fibroblasts with PDGF-BB was neutralized by the culture medium from TNBCT/Bo-sPDGFRβ cells. Intratibial injection of TNBCT/Bo-sPDGFRβ cells into athymic nude mice resulted in a significant decrease in tumor incidence compared with control mice (P < 0.01). This attenuated growth correlated with decreased cancer cell proliferation, angiogenesis, and recruitment of stromal cells, and with an increase in the number of apoptotic cells. These findings suggest that sPDGFRβ is useful for the treatment of breast cancer bone metastasis.