Drug Insight: intracellular inhibitors of HER2--clinical development of lapatinib in breast cancer

Design, synthesis, molecular docking, and evaluation of sulfonyl quinazoline analogues as promising liver cancer drugs

Inhibiting cyclin-dependent kinases (CDK) offers an important arsenal for cancer treatments by interfering with apoptotic proteins related to cancer. Novel selective cyclin-dependent kinases inhibitors using the Quinazoline as the cap with multiple electronic donating (EDG) and/or electron withdrawing group (EWG) substituted Aniline chain at the C-2 position were designed, synthesized, and evaluated for activity against liver cancer. Among the tested compounds, compounds B34 and B35 emerged as potent candidates in the series, with IC50 values of 0.102 ± 0.04 µM and 0.058 ± 0.003 µM, respectively. They also suppressed the enzymatic activity of CDK2/cyclinA2 selectively. Further biological studies revealed that compounds B34 and B35 arrested the cell cycle, and induced apoptosis in HepG-2 cancer cells through a Caspase-mediated mechanism, facilitating the release of Cyt-c through modulation of Caspase-3 expression. More importantly, compounds B34 and B35 suppressed the xenografted tumor growth in mice in a dose-dependent manner. Finally, through a molecular docking study, it was confirmed that compoundsB34 andB35 retained crucial hydrogen bonding and hydrophobic interactions with CDK receptor, rationalizing their higher efficacy compared to other compounds in the series. Taken together, the Quinazoline derivatives B34 and B35 may serve as novel chemotherapeutic agents through inhibition of CDK.

Exploring the chemotherapeutic potential of currently used kinase inhibitors: An update

Protein kinases are enzymes that transfer phosphate to protein, resulting in the modification of the protein. The human genome encodes approximately 538 kinases. Kinases play a role in maintaining a number of cellular processes, including control of the cell cycle, metabolism, survival, and differentiation. Protein kinase dysregulation causes several diseases, and it has been shown that numerous kinases are deregulated in cancer. The oncogenic potential of these kinases is increased by a number of processes, including overexpression, relocation, fusion point mutations, and the disruption of upstream signaling. Understanding of the mechanism or role played by kinases has led to the development of a large number of kinase inhibitors with promising clinical benefits. In this review, we discuss FDA-approved kinase inhibitors and their mechanism, clinical benefits, and side effects, as well as the challenges of overcoming some of their side effects and future prospects for new kinase inhibitor discovery.

Reverse Engineering Drugs: Lorcaserin as an Example

Novel central nervous system (CNS)-based therapies have been difficult to produce due to the complexity of the brain, limited knowledge of CNS-based disease development and associated pathways, difficulty in penetrating the blood brain barrier, and a lack of reliable biomarkers of disease. Reverse engineering in drug development allows the utilization of new knowledge of disease pathways and the use of innovative technology to develop medications with enhanced efficacy and reduced toxicities. Lorcaserin was developed as a specific 5HT_2C serotonin receptor agonist for the treatment of obesity with limited off-target effects at the 5HT_2A and 5HT_2B receptors. This receptor specificity limited the hallucinogenic and cardiovascular side effects noted with other serotonin receptor agonists. Reverse engineering approaches to drug development reduce the cost of producing new medications, identify specific populations of patients that will derive the most benefit from therapy, and produce novel therapies with greater efficacy and limited toxicity.

Design and synthesis of some new 6-bromo-2-(pyridin-3-yl)-4-substituted quinazolines as multi tyrosine kinase inhibitors

The present study involves design and synthesis of five series of 6-bromo-2-(pyridin-3-yl)-4-substituted quinazolines 9a-l, 11a-e, 13a-c, 14a-f and 15a-e. Candidates 9a-l and 11a-e were evaluated for their EGFR and HER2 inhibitory activity compared to Lapatinib. Compounds 9b, 9d, 9f, 11b and 11c were further screened for their in vitro cytotoxicity against two human breast cancer cell lines: AU-565 and MDA-MB-231 in addition to normal breast cell line MCF10A. Compound 9d revealed a remarkable cytotoxic efficacy against AU-565 cell line (IC₅₀ = 1.54 µM) relative to Lapatinib (IC₅₀ = 0.48 µM), whereas compounds 9d and 11c showed a superior cytotoxicity towards MDA-MB-231 (IC₅₀ = 2.67 and 1.75 µM, respectively) in comparison to Lapatinib (IC₅₀ = 9.29 µM). Moreover, compounds 13a-c, 13a-c, 14a-f and 15a-e were tested for their VEGFR-2 inhibitory activity compared to Sorafenib. Compounds 13a, 14c and 14e exhibited remarkable inhibition (IC₅₀ = 79.80, 50.22 and 78.02 nM, respectively) relative to Sorafenib (IC₅₀ = 51.87 nM). In vitro cytotoxicity of these compounds against HepG2, HCT-116 and normal cell (WISH) revealed a superior cytotoxicity against HepG2, HCT-116 especially 13a (IC₅₀ = 17.51 and 5.56 µM, respectively) and 14c (IC₅₀ = 10.40 and 3.37 µM, respectively) compared to Sorafenib (IC₅₀ = 19.33 and 6.82 µM, respectively). Compounds 9d, 11c and 14c were subjected to cell cycle analysis and apoptotic assay. Molecular docking and ADME prediction studies were fulfilled to illustrate the interaction of the potent derivatives with the hot spots of the active site of EGFR, HER2 and VEGFR-2 along with prediction of their pharmacokinetic and physicochemical properties.

Therapeutic progression of quinazolines as targeted chemotherapeutic agents

Presently cancer is a grave health issue with predominance beyond restrictions. It can affect any organ of the body. Most of the available chemotherapeutic drugs are highly toxic, not much selective and eventually lead to the development of resistance. Therefore, a target specific palliative approach for the treatment of cancer is required. Remarkable advancements in science have illuminated various molecular pathways responsible for cancer. This has resulted in abundant opportunities to develop targeted anticancer agents. Quinazoline nucleus is a privileged scaffold with significant diversified pharmacological activities. Numerous established anticancer quinazoline derivatives constitute a new class of chemotherapeutic agents which are found to act by inhibiting various protein kinases as well as other molecular targets. A recent update on various quinazoline derivatives acting on different types of molecular targets for the treatment of cancer has been compiled in this review. Brief SAR studies of quinazoline derivatives acting through different mechanisms of action have been highlighted. The comprehensive medicinal chemistry aspects of these agents in this review provide a panoramic view to the biologists as well as medicinal chemists working in this area and would assist them in their efforts to design and synthesize novel quinazoline based anticancer compounds.

Glucose-6-phosphate dehydrogenase blockade potentiates tyrosine kinase inhibitor effect on breast cancer cells through autophagy perturbation

Background

Glucose-6-phospate dehydrogenase (G6PD) is the limiting enzyme of the pentose phosphate pathway (PPP) correlated to cancer progression and drug resistance. We previously showed that G6PD inhibition leads to Endoplasmic Reticulum (ER) stress often associated to autophagy deregulation. The latter can be induced by target-based agents such as Lapatinib, an anti-HER2 tyrosine kinase inhibitor (TKI) largely used in breast cancer treatment.

Methods

Here we investigate whether G6PD inhibition causes autophagy alteration, which can potentiate Lapatinib effect on cancer cells. Immunofluorescence and flow cytometry for LC3B and lysosomes tracker were used to study autophagy in cells treated with lapatinib and/or G6PD inhibitors (polydatin). Immunoblots for LC3B and p62 were performed to confirm autophagy flux analyses together with puncta and colocalization studies. We generated a cell line overexpressing G6PD and performed synergism studies on cell growth inhibition induced by Lapatinib and Polydatin using the median effect by Chou-Talay. Synergism studies were additionally validated with apoptosis analysis by annexin V/PI staining in the presence or absence of autophagy blockers.

Results

We found that the inhibition of G6PD induced endoplasmic reticulum stress, which was responsible for the deregulation of autophagy flux. Indeed, G6PD blockade caused a consistent increase of autophagosomes formation independently from mTOR status. Cells engineered to overexpress G6PD became resilient to autophagy and resistant to lapatinib. On the other hand, G6PD inhibition synergistically increased lapatinib-induced cytotoxic effect on cancer cells, while autophagy blockade abolished this effect. Finally, in silico studies showed a significant correlation between G6PD expression and tumour relapse/resistance in patients.

Conclusions

These results point out that autophagy and PPP are crucial players in TKI resistance, and highlight a peculiar vulnerability of breast cancer cells, where impairment of metabolic pathways and autophagy could be used to reinforce TKI efficacy in cancer treatment.

A comprehensive review of protein kinase inhibitors for cancer therapy

INTRODUCTION

Protein kinases are involved in various cellular functions. About 2% of the human genome encodes for protein kinases. Dysregulation of protein kinases is implicated in various processes of carcinogenesis. The advent of protein kinase inhibitors in cancer therapy has led to a paradigm shift in cancer therapy. Several protein kinase inhibitors have been approved by FDA in the last few decades. Areas covered: This article provides a review of the FDA approved protein kinase inhibitors as of December 2017 for the well-known oncogenic protein kinases. A list of FDA approved protein kinase inhibitors and their FDA approved clinical indications were cataloged. The role of the respective oncogenic protein kinases in carcinogenesis and cancer progression and the relevant landmark clinical trials of respective protein kinase inhibitors leading up to the FDA approval were PubMed searched and discussed. Expert commentary: Further understanding of the molecular origin of various cancers would help identify new targets. Use of biomarker profiling might select the patient population that would benefit better from kinase inhibitors. Clinical trials should be designed to identify the appropriate sequence of the available kinase inhibitors. It would prove to be useful to test these drugs in the adjuvant setting.

In vivo near-infrared imaging of ErbB2 expressing breast tumors with dual-axes confocal endomicroscopy using a targeted peptide

ErbB2 expression in early breast cancer can predict tumor aggressiveness and clinical outcomes in large patient populations. Accurate assessment with physical biopsy and conventional pathology can be limited by tumor heterogeneity. We aim to demonstrate real-time optical sectioning using a near-infrared labeled ErbB2 peptide that generates tumor-specific contrast in human xenograft breast tumors in vivo. We used IRDye800CW as the fluorophore, validated performance characteristics for specific peptide binding to cells in vitro, and investigated peak peptide uptake in tumors using photoacoustic tomography. We performed real-time optical imaging using a handheld dual-axes confocal fluorescence endomicroscope that collects light off-axis to reduce tissue scattering for greater imaging depths. Optical sections in either the vertical or horizontal plane were collected with sub-cellular resolution. Also, we found significantly greater peptide binding to pre-clinical xenograft breast cancer in vivo and to human specimens of invasive ductal carcinoma that express ErbB2 ex vivo. We used a scrambled peptide for control. Peptide biodistribution showed high tumor uptake by comparison with other organs to support safety. This novel integrated imaging strategy is promising for visualizing ErbB2 expression in breast tumors and serve as an adjunct during surgery to improve diagnostic accuracy, identify tumor margins, and stage early cancers.

Molecular Mechanisms and Translational Therapies for Human Epidermal Receptor 2 Positive Breast Cancer

Breast cancer is the second leading cause of cancer death among women. Human epidermal receptor 2 (HER2) positive breast cancer (HER2+ BC) is the most aggressive subtype of breast cancer, with poor prognosis and a high rate of recurrence. About one third of breast cancer is HER2+ BC with significantly high expression level of HER2 protein compared to other subtypes. Therefore, HER2 is an important biomarker and an ideal target for developing therapeutic strategies for the treatment HER2+ BC. In this review, HER2 structure and physiological and pathological roles in HER2+ BC are discussed. Two diagnostic tests, immunohistochemistry (IHC) and fluorescent in situ hybridization (FISH), for evaluating HER2 expression levels are briefly introduced. The current mainstay targeted therapies for HER2+ BC include monoclonal antibodies, small molecule tyrosine kinase inhibitors, antibody-drug conjugates (ADC) and other emerging anti-HER2 agents. In clinical practice, combination therapies are commonly adopted in order to achieve synergistic drug response. This review will help to better understand the molecular mechanism of HER2+ BC and further facilitate the development of more effective therapeutic strategies against HER2+ BC.

The erbB3- and IGF-1 receptor-initiated signaling pathways exhibit distinct effects on lapatinib sensitivity against trastuzumab-resistant breast cancer cells

Both erbB3 and IGF-1 receptor (IGF-1R) have been shown to play an important role in trastuzumab resistance. However, it remains unclear whether erbB3- and IGF-1R-initiated signaling pathways possess distinct effects on the sensitivity of lapatinib, a dual tyrosine kinase inhibitor against both EGFR and erbB2, in trastuzumab-resistant breast cancer. Here, we show that the trastuzumab-resistant SKBR3-pool2 and BT474-HR20 breast cancer sublines, as compared the parental SKBR3 and BT474 cells, respectively, exhibit refractoriness to lapatinib. Knockdown of erbB3 inhibited Akt in SKBR3-pool2 and BT474-HR20 cells, significantly increased lapatinib efficacy, and dramatically re-sensitized the cells to lapatinib-induced apoptosis. In contrast, specific knockdown of IGF-1R did not alter the cells' responsiveness to lapatinib. While the levels of phosphorylated Src (P-Src) were reduced upon IGF-1R downregulation, the P-Akt levels remained unchanged. Furthermore, a specific inhibitor of Akt, but not Src, significantly enhanced lapatinib-mediated anti-proliferative/anti-survival effects on SKBR3-pool2 and BT474-HR20 cells. These data indicate that erbB3 signaling is critical for both trastuzumab and lapatinib resistances mainly through the PI-3K/Akt pathway, whereas IGF-1R-initiated Src activation results in trastuzumab resistance without affecting lapatinib sensitivity. Our findings may facilitate the development of precision therapeutic regimens for erbB2-positive breast cancer patients who become resistant to erbB2-targeted therapy.

Lapatinib resistance in HER2+ cancers: latest findings and new concepts on molecular mechanisms

In the era of new and mostly effective molecular targeted therapies, human epidermal growth factor receptor 2 positive (HER2+) cancers are still intractable diseases. Lapatinib, a dual epidermal growth factor receptor (EGFR) and HER2 tyrosine kinase inhibitor, has greatly improved breast cancer prognosis in recent years after the initial introduction of trastuzumab (Herceptin). However, clinical evidence indicates the existence of both primary unresponsiveness and secondary lapatinib resistance, which leads to the failure of this agent in HER2+ cancer patients. It remains a major clinical challenge to target the oncogenic pathways with drugs having low resistance. Multiple pathways are involved in the occurrence of lapatinib resistance, including the pathways of receptor tyrosine kinase, non-receptor tyrosine kinase, autophagy, apoptosis, microRNA, cancer stem cell, tumor metabolism, cell cycle, and heat shock protein. Moreover, understanding the relationship among these mechanisms may contribute to future tumor combination therapies. Therefore, it is of urgent necessity to elucidate the precise mechanisms of lapatinib resistance and improve the therapeutic use of this agent in clinic. The present review, in the hope of providing further scientific support for molecular targeted therapies in HER2+ cancers, discusses about the latest findings and new concepts on molecular mechanisms underlying lapatinib resistance.

Catalytic mechanisms and regulation of protein kinases

Protein kinases transfer a phosphoryl group from ATP onto target proteins and play a critical role in signal transduction and other cellular processes. Here, we review the kinase kinetic and chemical mechanisms and their application in understanding kinase structure and function. Aberrant kinase activity has been implicated in many human diseases, in particular cancer. We highlight applications of technologies and concepts derived from kinase mechanistic studies that have helped illuminate how kinases are regulated and contribute to pathophysiology.

Simultaneous Dual Selective Targeted Delivery of Two Covalent Gemcitabine Immunochemotherapeutics and Complementary Anti-Neoplastic Potency of [Se]-Methylselenocysteine

The anti-metabolite chemotherapeutic, gemcitabine is relatively effective for a spectrum of neoplastic conditions that include various forms of leukemia and adenocarcinoma/carcinoma. Rapid systemic deamination of gemcitabine accounts for a brief plasma half-life but its sustained administration is often curtailed by sequelae and chemotherapeutic-resistance. A molecular strategy that diminishes these limitations is the molecular design and synthetic production of covalent gemcitabine immunochemotherapeutics that possess properties of selective "targeted" delivery. The simultaneous dual selective "targeted" delivery of gemcitabine at two separate sites on the external surface membrane of a single cancer cell types represents a therapeutic approach that can increase cytosol chemotherapeutic deposition; prolong chemotherapeutic plasma half-life (reduces administration frequency); minimize innocent exposure of normal tissues and healthy organ systems; and ultimately enhance more rapid and thorough resolution of neoplastic cell populations.

MATERIALS AND METHODS

A light-reactive gemcitabine intermediate synthesized utilizing succinimidyl 4,4-azipentanoate was covalently bound to anti-EGFR or anti-HER2/neu IgG by exposure to UV light (354-nm) resulting in the synthesis of covalent immunochemotherapeutics, gemcitabine-(C₄-amide)-[anti-EGFR] and gemcitabine-(C₄-amide)-[anti-HER2/neu]. Cytotoxic anti-neoplastic potency of gemcitabine-(C₄-amide)-[anti-EGFR] and gemcitabine-(C₄-amide)-[anti-HER2/neu] between gemcitabine-equivalent concentrations of 10^-12 M and 10^-6 M was determined utilizing chemotherapeutic-resistant mammary adenocarcinoma (SKRr-3). The organoselenium compound, [Se]-methylselenocysteine was evaluated to determine if it complemented the anti-neoplastic potency of the covalent gemcitabine immunochemotherapeutics.

RESULTS

Gemcitabine-(C₄-amide)-[anti-EGFR], gemcitabine-(C₄-amide)-[anti-HER2/neu] and the dual simultaneous combination of gemcitabine-(C₄-amide)-[anti-EGFR] with gemcitabine-(C₄-amide)-[anti-HER2/neu] all had anti-neoplastic cytotoxic potency against mammary adenocarcinoma. Gemcitabine-(C₄-amide)-[anti-EGFR] and gemcitabine-(C₄-amide)-[anti-HER2/neu] produced progressive increases in anti-neoplastic cytotoxicity that were greatest between gemcitabine-equivalent concentrations of 10^-9 M and 10^-6 M. Dual simultaneous combinations of gemcitabine-(C₄-amide)-[anti-EGFR] with gemcitabine-(C₄-amide)-[anti-HER2/neu] produced levels of anti-neoplastic cytotoxicity intermediate between each of the individual covalent gemcitabine immunochemotherapeutics. Total anti-neoplastic cytotoxicity of the dual simultaneous combination of gemcitabine-(C₄-amide)-[anti-EGFR] and gemcitabine-(C₄-amide)-[anti-HER2/neu] against chemotherapeutic-resistant mammary adenocarcinoma (SKBr-3) was substantially higher when formulated with [Se]-methylsele-nocysteine.

ErbB receptor-driven prolactinomas respond to targeted lapatinib treatment in female transgenic mice

As ErbB receptors are expressed in prolactinomas and exhibit downstream effects on prolactin (PRL) production and cell proliferation, we generated transgenic mice using a PRL enhancer/promoter expression system to restrict lactotroph-specific expression of human epidermal growth factor receptor (EGFR) or human EGFR2 (HER2). EGFR or HER2 transgenic mice developed prolactinomas between 13 and 15 months, and confocal immunofluorescence and Western blot analysis confirmed lactotroph-restricted PRL and EGFR or HER2 coexpression. Circulating PRL levels in EGFR and HER2 transgenic mice were increased 5- and 3.8-fold, respectively. Inhibiting EGFR or HER2 signaling with oral lapatinib (100 mg/kg), a dual tyrosine kinase inhibitor for both EGFR and HER2, suppressed circulating PRL by 72% and attenuated tumor PRL expression by 80% and also attenuated downstream tumor EGFR/HER2 signaling. This model demonstrates the role of ErbB receptors underlying prolactinoma tumorigenesis and the feasibility of targeting these receptors for translation to treatment of refractory prolactinomas.

Prolactinoma ErbB receptor expression and targeted therapy for aggressive tumors

As ErbB signaling is a determinant of prolactin synthesis, role of ErbB receptors was tested for prolactinoma outcomes and therapy. The objective of this study was to characterize ErbB receptor expression in prolactinomas and then perform a pilot study treating resistant prolactinomas with a targeted tyrosine kinase inhibitor (TKI). Retrospective analysis of prolactinomas and pilot study for dopamine agonist resistant prolactinomas in tertiary referral center. We performed immunofluorescent staining of a tissue array of 29 resected prolactinoma tissues for EGFR, ErbB2, ErbB3, and ErbB4 correlated with clinical features. Two patients with aggressive resistant prolactinomas enrolled and completed trial. They received lapatinib 1,250 mg daily for 6 months with tumor and hormone assessments. Main outcome measures were positive tumor staining of respective ErbB receptors, therapeutic reduction of prolactin levels and tumor shrinkage. Treated PRL levels and tumor volumes were suppressed in both subjects treated with TKI. EGFR expression was positive in 82 % of adenomas, ErbB2 in 92 %, ErbB3 in 25 %, and ErbB4 in 71 %, with ErbB2 score > EGFR > ErbB4 > ErbB3. Higher ErbB3 expression was associated with optic chiasm compression (p = 0.03), suprasellar extension (p = 0.04), and carotid artery encasement (p = 0.01). Higher DA response rates were observed in tumors with higher ErbB3 expression. Prolactinoma expression of specific ErbB receptors is associated with tumor invasion, symptoms, and response to dopamine agonists. Targeting ErbB receptors may be effective therapy in patients with resistant prolactinomas.

Anti-Neoplastic Cytotoxicity of Gemcitabine-(C4-amide)-[anti-EGFR] in Dual-combination with Epirubicin-(C3-amide)-[anti-HER2/neu] against Chemotherapeutic-Resistant Mammary Adenocarcinoma (SKBr-3) and the Complementary Effect of Mebendazole

AIMS

Delineate the feasibility of simultaneous, dual selective "targeted" chemotherapeutic delivery and determine if this molecular strategy can promote higher levels anti-neoplastic cytotoxicity than if only one covalent immunochemotherapeutic is selectively "targeted" for delivery at a single membrane associated receptor over-expressed by chemotherapeutic-resistant mammary adenocarcinoma.

METHODOLOGY

Gemcitabine and epirubicin were covalently bond to anti-EGFR and anti-HER2/neu utilizing a rapid multi-phase synthetic organic chemistry reaction scheme. Determination that 96% or greater gemcitabine or epirubicin content was covalently bond to immunoglobulin fractions following size separation by micro-scale column chromatography was established by methanol precipitation analysis. Residual binding-avidity of gemcitabine-(C4-amide)-[anti-EG-FR] applied in dual-combination with epirubicin-(C3-amide)-[anti-HER2/neu] was determined by cell-ELIZA utilizing chemotherapeutic-resistant mammary adenocarcinoma (SKBr-3) populations. Lack of fragmentation or polymerization was validated by SDS-PAGE/immunodetection/chemiluminescent autoradiography. Anti-neoplastic cytotoxic potency was determined by vitality stain analysis of chemotherapeutic-resistant mammary adenocarcinoma (SKBr-3) monolayers known to uniquely over-express EGFR (2 × 105/cell) and HER2/neu (1 × 106/cell) receptor complexes. The covalent immunochemotherapeutics gemcitabine-(C4-amide)-[anti-EGFR] and epirubicin-(C3-amide)-[anti-HER2/neu] were applied simultaneously in dual-combination to determine their capacity to collectively evoke elevated levels of anti-neoplastic cytotoxicity. Lastly, the tubulin/microtubule inhibitor mebendazole evaluated to determine if it's potential to complemented the anti-neoplastic cytotoxic properties of gemcitabine-(C4-amide)-[anti-EGFR] in dual-combination with epirubicin-(C3-amide)-[anti-HER2/neu].

RESULTS

Dual-combination of gemcitabine-(C4-amide)-[anti-EGFR] with epirubicin-(C3-amide)-[anti-HER2/neu] produced greater levels of anti-neoplastic cytotoxicity than either of the covalent immunochemotherapeutics alone. The benzimidazole microtubule/tubulin inhibitor, mebendazole complemented the anti-neoplastic cytotoxicity of gemcitabine-(C4-amide)-[anti-EGFR] in dual-combination with epirubicin-(C3-amide)-[anti-HER2/neu].

CONCLUSIONS

The dual-combination of gemcitabine-(C4-amide)-[anti-EGFR] with epirubicin-(C3-amide)-[anti-HER2/neu] produced higher levels of selectively "targeted" anti-neoplastic cytotoxicity against chemotherapeutic-resistant mammary adenocarcinoma (SKBr-3) than either covalent immunochemotherapeutic alone. The benzimidazole tubulin/microtubule inhibitor, mebendazole also possessed anti-neoplastic cytotoxicity against chemotherapeutic-resistant mammary adenocarcinoma (SKBr-3) and complemented the potency and efficacy of gemcitabine-(C4-amide)-[anti-EGFR] in dual-combination with epirubicin-(C3-amide)-[anti-HER2/neu].

Phosphoproteomic analysis identifies activated MET-axis PI3K/AKT and MAPK/ERK in lapatinib-resistant cancer cell line

Lapatinib, a dual inhibitor of epidermal growth factor receptor (EGFR) and human epidermal growth factor receptor 2 (HER2) tyrosine kinases, has shown promising results as a growth inhibitor of HER2-positive cancer cells in vitro. However, similar to other EGFR-targeting drugs, acquired resistance to lapatinib by HER2-positive cancer cells remains a major clinical challenge. To elucidate resistance mechanisms to EGFR/HER2-targeting agents, we performed a systematic quantitative comparison of the phosphoproteome of lapatinib-resistant (LR) human gastric cancer cells (SNU216-LR) versus parental cells (SNU216) using a titanium dioxide (TiO2) phosphopeptide enrichment method and analysis with a Q-Exactive hybrid quadrupole-Orbitrap mass spectrometer. Biological network analysis of differentially expressed phosphoproteins revealed apparent constitutive activation of the MET-axis phosphatidylinositide 3-kinase (PI3K)/α-serine/threonine-protein kinase (AKT) and mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) signaling pathways in SNU216-LR. Inhibition of the PI3K/AKT and MAPK/ERK signaling pathways in SNU216-LR also leads to cell cycle arrest, confirming the biological network analysis. Lapatinib sensitivity was restored when cells were treated with several molecular targeting agents in combination with lapatinib. Thus, by integrating phosphoproteomic data, protein networks and effects of signaling pathway modulation on cell proliferation, we found that SNU216-LR maintains constitutive activation of the PI3K/AKT and MAPK/ERK pathways in a MET-dependent manner. These findings suggest that pathway activation is a key compensatory intracellular phospho-signaling event that may govern gastric cancer cell resistance to drug treatment.

The anti-erbB3 antibody MM-121/SAR256212 in combination with trastuzumab exerts potent antitumor activity against trastuzumab-resistant breast cancer cells

Background

Elevated expression of erbB3 receptor has been reported to induce resistance to therapeutic agents, including trastuzumab in erbB2-overexpressing breast cancer. Our recent studies indicate that erbB3 interacts with both erbB2 and IGF-1 receptor to form a heterotrimeric complex in trastuzumab-resistant breast cancer cells. Herein, we investigate the antitumor activity of MM-121/SAR256212, a fully human anti-erbB3 antibody (Ab), against two erbB2-overexpressing breast cancer cell lines resistant to trastuzumab.

Methods

MTS-based proliferation assays were used to determine cell viability upon treatment of trastuzumab and/or MM-121/SAR256212. Cell cycle progression was examined by flow cytometric analysis. Western blot analyses were performed to determine the expression and activation of proteins. Tumor xenografts were established by inoculation of the trastuzumab-resistant BT474-HR20 cells into nude mice. The tumor-bearing mice were treated with trastuzumab and/or MM-121/SAR256212 via i.p injection to determine the Abs’ antitumor activity. Immunohistochemical analyses were carried out to study the Abs’ inhibitory effects on tumor cell proliferation and induction of apoptosis in vivo.

Results

MM-121 significantly enhanced trastuzumab-induced growth inhibition in two sensitive and two resistant breast cancer cell lines. MM-121 in combination with trastuzumab resulted in a dramatic reduction of phosphorylated erbB3 (P-erbB3) and Akt (P-Akt) in the in vitro studies. MM-121 combined with trastuzumab did not induce apoptosis in the trastuzumab-resistant cell lines under our cell culture condition, rather induced cell cycle G1 arrest mainly associated with the upregulation of p27^kip1. Interestingly, in the tumor xenograft model established from the trastuzumab-resistant cells, MM-121 in combination with trastuzumab as compared to either agent alone dramatically inhibited tumor growth correlated with a significant reduction of Ki67 staining and increase of cleaved caspase-3 in the tumor tissues.

Conclusions

The combination of MM-121 and trastuzumab not only inhibits erbB2-overexpressing breast cancer cell proliferation, but also promotes the otherwise trastuzumab-resistant cells undergoing apoptosis in an in vivo xenografts model. Thus, MM-121 exhibits potent antitumor activity when combined with trastuzumab under the studied conditions. Our data suggest that further studies regarding the suitability of MM-121 for treatment of breast cancer patients whose tumors overexpress erbB2 and become resistant to trastuzumab may be warranted.

18FDG-PET for Early Prediction of Complete Response to Lapatinib and Capecitabine in HER2-Positive Metastatic Breast Cancer: A Case Report

Targeted therapies against HER2 (trastuzumab, lapatinib) have improved the efficacy of treatment and the outcome of patients with HER2-positive breast cancer. Lapatinib is a tyrosine kinase inhibitor targeting EGFR1 and HER2: it binds the intracellular domain of these receptors and blocks their downstream signaling pathways. In combination with capecitabine, it is the standard of care for patients with trastuzumab-resistant advanced breast cancer. We present the case of a patient exhibiting a complete and prolonged clinical response to second-line treatment with lapatinib and capecitabine after failure of trastuzumab-based therapy. 18FDG-PET allowed the detection of disease remission several months before computed tomography. Molecular imaging with 18FDG seems the most powerful way to measure the pharmacodynamic effects of targeted anticancer drugs. This case report confirms that18FDG-PET plays a key role not only in detecting metastatic disease but also in evaluating the response to HER2-directed therapy.

Phase I study evaluating the combination of lapatinib (a Her2/Neu and EGFR inhibitor) and everolimus (an mTOR inhibitor) in patients with advanced cancers: South West Oncology Group (SWOG) Study S0528

PURPOSE

Everolimus, an oral inhibitor of mammalian target of rapamycin, can augment the efficacy of HER inhibitors in preclinical studies. This study was conducted to determine the safety and pharmacokinetics (PK) of the combination of lapatinib, a Her1 and 2 inhibitor, and everolimus and to describe its anti-tumor activity in the Phase I setting.

METHODS

In Part I, dose escalation to define the maximum tolerated dose (MTD) was performed. In Part II, PK of both drugs were analyzed to assess drug-drug interaction.

RESULTS

Twenty-three evaluable patients with advanced cancers were treated on six different dose levels in Part I of the study. The dose-limiting toxicities were diarrhea, rash, mucositis, and fatigue. The MTD of the combination was 1,250 mg of lapatinib and 5 mg of everolimus once daily. In Part II of the study, 54 patients were treated with the combination at the MTD. The mean everolimus time to maximum concentration was increased by 44 %, and mean clearance was decreased by 25 % when co-administered with lapatinib, though these differences were not statistically significant. There was no significant influence on the PK of lapatinib by everolimus. Two patients achieved a partial response [thymic cancer (45+ months) and breast cancer (unconfirmed PR; 7 months)]; 11 patients attained stable disease of at least 4 months.

CONCLUSIONS

Lapatinib and everolimus are well tolerated at doses of 1,250 and 5 mg po daily, respectively. Stable disease ≥4 months/PR was achieved in 13 of 78 patients (17 %).

Dynamics of DNA damage induced pathways to cancer

Chemotherapy is commonly used in cancer treatments, however only 25% of cancers are responsive and a significant proportion develops resistance. The p53 tumour suppressor is crucial for cancer development and therapy, but has been less amenable to therapeutic applications due to the complexity of its action, reflected in 66,000 papers describing its function. Here we provide a systematic approach to integrate this information by constructing a large-scale logical model of the p53 interactome using extensive database and literature integration. The model contains 206 nodes representing genes or proteins, DNA damage input, apoptosis and cellular senescence outputs, connected by 738 logical interactions. Predictions from in silico knock-outs and steady state model analysis were validated using literature searches and in vitro based experiments. We identify an upregulation of Chk1, ATM and ATR pathways in p53 negative cells and 61 other predictions obtained by knockout tests mimicking mutations. The comparison of model simulations with microarray data demonstrated a significant rate of successful predictions ranging between 52% and 71% depending on the cancer type. Growth factors and receptors FGF2, IGF1R, PDGFRB and TGFA were identified as factors contributing selectively to the control of U2OS osteosarcoma and HCT116 colon cancer cell growth. In summary, we provide the proof of principle that this versatile and predictive model has vast potential for use in cancer treatment by identifying pathways in individual patients that contribute to tumour growth, defining a sub population of “high” responders and identification of shifts in pathways leading to chemotherapy resistance.

[Systemic treatment of brain metastases from breast cancer: cytotoxic chemotherapy and targeted therapies]

Prevalence of brain metastases is increasing in breast cancer. Brain metastases represent a poor-prognosis disease for which local treatments continue to play a major role. In spite of the presence of a physiological blood-brain barrier limiting their activity, some systemic treatments may display a significant antitumor activity at the central nervous system level. In HER2-positive metastatic breast cancer with brain metastases not previously treated with whole brain radiotherapy, capecitabine and lapatinib combination obtains a volumetric reponse in two thirds of patients (LANDSCAPE study). If confirmed, these results could modify in selected patients the layout of therapeutic strategies. Promoting novel targeted approaches and innovative therapeutic combinations is a critical need to improve survival of breast cancer patients with brain metastases.

FOXM1 (Forkhead box M1) in tumorigenesis: overexpression in human cancer, implication in tumorigenesis, oncogenic functions, tumor-suppressive properties, and target of anticancer therapy

FOXM1 (Forkhead box M1) is a typical proliferation-associated transcription factor and is also intimately involved in tumorigenesis. FOXM1 stimulates cell proliferation and cell cycle progression by promoting the entry into S-phase and M-phase. Additionally, FOXM1 is required for proper execution of mitosis. In accordance with its role in stimulation of cell proliferation, FOXM1 exhibits a proliferation-specific expression pattern and its expression is regulated by proliferation and anti-proliferation signals as well as by proto-oncoproteins and tumor suppressors. Since these factors are often mutated, overexpressed, or lost in human cancer, the normal control of the foxm1 expression by them provides the basis for deregulated FOXM1 expression in tumors. Accordingly, FOXM1 is overexpressed in many types of human cancer. FOXM1 is intimately involved in tumorigenesis, because it contributes to oncogenic transformation and participates in tumor initiation, growth, and progression, including positive effects on angiogenesis, migration, invasion, epithelial-mesenchymal transition, metastasis, recruitment of tumor-associated macrophages, tumor-associated lung inflammation, self-renewal capacity of cancer cells, prevention of premature cellular senescence, and chemotherapeutic drug resistance. However, in the context of urethane-induced lung tumorigenesis, FOXM1 has an unexpected tumor suppressor role in endothelial cells because it limits pulmonary inflammation and canonical Wnt signaling in epithelial lung cells, thereby restricting carcinogenesis. Accordingly, FOXM1 plays a role in homologous recombination repair of DNA double-strand breaks and maintenance of genomic stability, that is, prevention of polyploidy and aneuploidy. The implication of FOXM1 in tumorigenesis makes it an attractive target for anticancer therapy, and several antitumor drugs have been reported to decrease FOXM1 expression.

Influence of Alternative Tubulin Inhibitors on the Potency of a Epirubicin-Immunochemotherapeutic Synthesized with an Ultra Violet Light-Activated Intermediate: Influence of incorporating an internal/integral disulfide bond structure and Alternative Tubulin/Microtubule Inhibitors on the Cytotoxic Anti-Neoplastic Potency of Epirubicin-(C3-amide)-Anti-HER2/neu Synthesized Utilizing a UV-Photoactivated Anthracycline Intermediate

Immunochemotherapeutics, epirubicin-(C₃-amide)-SS-[anti-HER2/neu] with an internal disulfide bond, and epirubicin-(C₃-amide)-[anti-HER2/neu] were synthesized utilizing succinimidyl 2-[(4,4'-azipentanamido) ethyl]-1,3'-dithioproprionate or succinimidyl 4,4-azipentanoate respectively. Western blot analysis was used to determine the presence of any immunoglobulin fragmentation or IgG-IgG polymerization. Retained HER2/neu binding characteristics of epirubicin-(C₃-amide)-[anti-HER2/neu] and epirubicin-(C₃-amide)-SS-[anti-HER2/neu] were validated by cell-ELISA using a mammary adenocarcinoma (SKBr-3) population that highly over-expresses trophic HER2/neu receptor complexes. Cytotoxic anti-neoplastic potency of epirubicin-(C₃-amide)-[anti-HER2/neu] and epirubicin-(C₃-amide)-SS-[anti-HER2/neu] between epirubicin-equivalent concentrations of 10^-10 M and 10^-6 M was determined by measuring the vitality/proliferation of chemotherapeutic-resistant mammary adenocarcinoma (SKBr-3 cell type). Cytotoxic anti-neoplastic potency of benzimidazoles (albendazole, flubendazole, membendazole) and griseofulvin were assessed between 0-to-2 μg/ml and 0-to-100 μg/ml respectively while mebendazole and griseofulvin were analyzed at fixed concentrations of 0.35 μg/ml and 35 g/ml respectively in dual combination with gradient concentrations of epirubicin-(C₃-amide)-[anti-HER2/neu] and epirubicin-(C₃-amide)-SS-[anti-HER2/neu]. Cytotoxic anti-neoplastic potency for epirubicin-(C₃-amide)-[anti-HER2/neu] and epirubicin-(C₃-amide)-SS-[anti-HER2/neu] against chemotherapeutic-resistant mammary adenocarcinoma (SKBr-3) was nearly identical at epirubicin-equivalent concentrations of 10^-10 M and 10^-6 M. The benzimadazoles also possessed cytotoxic anti-neoplastic activity with flubendazole and albendazole being the most and least potent respectively. Similarly, griseofulvin had cytotoxic anti-neoplastic activity and was more potent than methylselenocysteine. Both mebendazole and griseofulvin when applied in dual combination with either epirubicin-(C₃-amide)-[anti-HER2/neu] or epirubicin-(C₃-amide)-SS-[anti-HER2/neu] produced enhanced levels of cytotoxic anti-neoplatic potency.

HER2/neu as a potential target for immunotherapy in gynecologic carcinosarcomas

Carcinosarcomas of the female genital tract are rare tumors with an aggressive clinical behavior. Trastuzumab, a humanized monoclonal antibody, acts by binding to HER2/neu extracellular domain and exhibits therapeutic efficacy in HER2/neu-overexpressing cancers. Two uterine carcinosarcomas (UMMT-ARK-1, UMMT-ARK-2) and 2 ovarian carcinosarcomas (OMMT-ARK-1, OMMT-ARK-2) were established as primary tumor cell lines in vitro and evaluated for HER2/neu expression by immunohistochemistry, fluorescent in situ hybridization analysis, quantitative real-time polymerase chain reaction, and for membrane-bound complement regulatory proteins CD46, CD55, and CD59 by flow cytometry. Sensitivity to trastuzumab-dependent cell-mediated cytotoxicity (ADCC) and complement-dependent cytotoxicity was studied in 5-hr chromium release assays. HER2/neu expression was demonstrated in OMMT-ARK-1 and OMMT-ARK-2. OMMT-ARK-2 demonstrated an amplification of the c-erbB2 gene by fluorescent in situ hybridization analysis and a high sensitivity to ADCC (mean killing, 45.6%; range, 32.3%-72.6%). A lower level of killing was detected against the fluorescent in situ hybridization analysis-negative OMMT-ARK-1 cell line (mean, 26.5%; range, 21.0%-31.8%). CD46, CD55, and CD59 membrane-bound complement regulatory proteins were expressed at high levels in all primary mixed müllerian tumor cell lines, and all these tumors were found to be highly resistant to complement-dependent cytotoxicity with or without trastuzumab. Addition of untreated and heat-inactivated plasma did not significantly decrease ADCC against OMMT-ARK-2 cell line, suggesting that while the cell line is highly resistant to complement, irrelevant IgG does not significantly alter the ability of trastuzumab to mediate ADCC. Our results suggest that HER2/neu may represent a novel target for the immunotherapy of a subset of human carcinosarcomas refractory to salvage chemotherapy.

Molecular mechanisms of cardiotoxicity induced by ErbB receptor inhibitor cancer therapeutics

The introduction of the so-called “targeted therapies”, particularly those drugs that inhibit the activity of tyrosine kinases, has represented a remarkable progress in the treatment of cancer. Although these drugs improve survival rates in cancer, significant cardiotoxicity, manifesting as left vertricular dysfunction and/or heart failure, has emerged. The ErbB receptor tyrosine kinases are being pursued as therapeutic targets because of their important roles in normal physiology and in cancer. Besides the fact that the ErbB receptors are indispensable during development and in normal adult physiology, epidermal growth factor (EGFR) and ErbB2 in particular have been implicated in the development of many human cancers. This review focuses on the rationale for targeting members of ErbB receptor family and numerous agents that are in use for inhibiting the pathway. We summarize the current knowledge on the physiological role of ErbB signaling in the ventricle and on structural aspects of ErbB receptor activation in cancer and cardiac cells. We examine the underlying mechanisms that result in on-target or off-target cardiotoxicities of ErbB inhibitors, which can influence the design of future anticancer therapies.

Development of high-throughput quantitative assays for glucose uptake in cancer cell lines

PURPOSE

Metabolism, and especially glucose uptake, is a key quantitative cell trait that is closely linked to cancer initiation and progression. Therefore, developing high-throughput assays for measuring glucose uptake in cancer cells would be enviable for simultaneous comparisons of multiple cell lines and microenvironmental conditions. This study was designed with two specific aims in mind: the first was to develop and validate a high-throughput screening method for quantitative assessment of glucose uptake in "normal" and tumor cells using the fluorescent 2-deoxyglucose analog 2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-2-deoxyglucose (2-NBDG), and the second was to develop an image-based, quantitative, single-cell assay for measuring glucose uptake using the same probe to dissect the full spectrum of metabolic variability within populations of tumor cells in vitro in higher resolution.

PROCEDURE

The kinetics of population-based glucose uptake was evaluated for MCF10A mammary epithelial and CA1d breast cancer cell lines, using 2-NBDG and a fluorometric microplate reader. Glucose uptake for the same cell lines was also examined at the single-cell level using high-content automated microscopy coupled with semi-automated cell-cytometric image analysis approaches. Statistical treatments were also implemented to analyze intra-population variability.

RESULTS

Our results demonstrate that the high-throughput fluorometric assay using 2-NBDG is a reliable method to assess population-level kinetics of glucose uptake in cell lines in vitro. Similarly, single-cell image-based assays and analyses of 2-NBDG fluorescence proved an effective and accurate means for assessing glucose uptake, which revealed that breast tumor cell lines display intra-population variability that is modulated by growth conditions.

CONCLUSIONS

These studies indicate that 2-NBDG can be used to aid in the high-throughput analysis of the influence of chemotherapeutics on glucose uptake in cancer cells.

Shared molecular targets in pediatric gliomas and ependymomas

BACKGROUND

Recent advances in multidisciplinary treatment approaches have improved the overall prognosis of pediatric brain tumors, but some patients remain refractory to treatment and do poorly. Several molecularly targeted therapies are under development for the treatment of brain tumors, and high-grade gliomas in adults are a particular area of study.

PROCEDURE

To better understand if these new therapies can be used in pediatric populations, we examined the expression of the following seven marker genes involved in signaling pathways targeted by new therapies: β-catenin, suppressor of fused (SUFU), erythroblastic leukemia viral oncogene homolog (ERBB) 2, platelet-derived growth factor receptorα (PDGFRα), proliferating cell nuclear antigen (PCNA), secreted protein acid and rich in cysteine (SPARC), and granulocyte colony-stimulating factor receptor (G-CSFR). Samples from 27 patients with the primitive neuroectodermal tumor (PNET)/medulloblastomas (MBs) (n = 8), ependymomas (n = 5), or gliomas (n = 14) were assessed by quantitative real-time PCR. [Correction made here after initial online publication]. We assigned an EXP score to compare across samples and determined the levels of gene expression among tumor cell types.

RESULTS

Gene expression varied among the different tumors, but, within a tumor type, clear expression patterns were seen. The expression of SUFU, ERBB2, and PCNA in metastatic MBs were greater than that seen in non-metastatic MBs. Most glioma cases highly expressed PDGFRα and G-CSFR. Additionally, the expression patterns of gliomas and ependymomas were similar (r = 0.77, P = 0.04), but PNET/MBs substantially differed from gliomas (r = -0.37, P = 0.41) or ependymomas (r = 0.23, P = 0.62).

CONCLUSIONS

The development of new drugs targeting up-regulated pathways may be useful for the treatment of pediatric brain tumors. As new drugs are developed, gliomas and ependymomas may be treated with similar compounds.

Mechanistic insights into the activation of oncogenic forms of EGF receptor

Epidermal growth factor receptor (EGFR) is a receptor tyrosine kinase that is commonly activated by mutation in non-small cell lung cancer. The mechanism of this oncogenic activation is not completely understood, but in contrast to that of the wild-type EGFR, it is proposed to be independent of kinase domain dimerization. Mechanistic studies on EGFR have mainly relied on cell-based assays or isolated kinase domain measurements. Here we show, using purified, near full-length human EGFR proteins (tEGFRs), that two oncogenic mutants are fully active independently of EGF and highly resistant to the therapeutic and endogenous inhibitors cetuximab, lapatinib and MIG6. Based on the pattern of inhibition and the effects of additional asymmetric kinase dimer interface mutations, we propose that these oncogenic EGFR mutants drive and strongly depend on the formation of the asymmetric kinase dimer for activation, which has implications for drug design and cancer treatment strategies.

Translational research of a novel humanized epidermal growth factor receptor-related protein: a putative inhibitor of pan-ErbB

PURPOSE

The ErbB family members are protein tyrosine kinases, which play a crucial role in the signal transduction pathways that regulate key cellular functions. Overexpression of the ErbB family members is associated with oncogenicity, metastatic potential, cell proliferation, apoptosis, angiogenesis, and prognosis in cancer. Molecular-targeted therapies centered on the ErbB signaling pathway are the currently promising anti-cancer therapies.

METHODS

We reviewed the literature to summarize the current knowledge of epidermal growth factor receptor (EGFR)-related protein (ERRP) and determine the potential of this protein to be translated into a molecular-targeting treatment for cancer.

RESULTS

ERRP isolated from rat gastroduodenal mucosa is a pan-ErbB inhibitor that targets multiple members of the ErbB family both in vitro and in vivo. Sequestration of ErbB ligands by ERRP results in the formation of inactive ErbB heterodimers and subsequent attenuation of signaling pathways activated by ErbB. We suggest a strategy to develop a humanized ERRP protein based on activity of rat EERP in vitro.

CONCLUSIONS

As rat ERRP protein is expected to generate an immune response in humans, we propose a hypothesis that a humanized version of ERRP has potential therapeutic value for cancer patients.

Novel approaches to treating leptomeningeal metastases

Leptomeningeal metastasis is a devastating complication of the central nervous system in patients with late-stage solid or hematological cancers. Leptomeningeal metastasis results from the multifocal seeding of the leptomeninges by malignant cancer cells. Although central nervous system metastasis usually presents in patients with widely disseminated and progressive late-stage cancer, malignant cells may spread to the cerebrospinal fluid during earlier disease stages in particularly aggressive cancers. Treatment of leptomeningeal metastasis is largely palliative but will often provide stabilization and protection from further neurological deterioration and improve quality of life. There is a need to raise awareness of the impact of leptomeningeal metastases on cancer patients and its known and putative biological basis. Novel diagnostic approaches include identification of biomarkers that may stratify the risk for developing leptomeningeal metastasis. Current therapies can be used more effectively while waiting for advanced treatments to be developed.

Order of amino acids in C-terminal cysteine-containing peptide-based chelators influences cellular processing and biodistribution of 99mTc-labeled recombinant Affibody molecules

Affibody molecules constitute a novel class of molecular display selected affinity proteins based on non-immunoglobulin scaffold. Preclinical investigations and pilot clinical data have demonstrated that Affibody molecules provide high contrast imaging of tumor-associated molecular targets shortly after injection. The use of cysteine-containing peptide-based chelators at the C-terminus of recombinant Affibody molecules enabled site-specific labeling with the radionuclide 99mTc. Earlier studies have demonstrated that position, composition and the order of amino acids in peptide-based chelators influence labeling stability, cellular processing and biodistribution of Affibody molecules. To investigate the influence of the amino acid order, a series of anti-HER2 Affibody molecules, containing GSGC, GEGC and GKGC chelators have been prepared and characterized. The affinity to HER2, cellular processing of 99mTc-labeled Affibody molecules and their biodistribution were investigated. These properties were compared with that of the previously studied 99mTc-labeled Affibody molecules containing GGSC, GGEC and GGKC chelators. All variants displayed picomolar affinities to HER2. The substitution of a single amino acid in the chelator had an appreciable influence on the cellular processing of 99mTc. The biodistribution of all 99mTc-labeled Affibody molecules was in general comparable, with the main difference in uptake and retention of radioactivity in excretory organs. The hepatic accumulation of radioactivity was higher for the lysine-containing chelators and the renal retention of 99mTc was significantly affected by the amino acid composition of chelators. The order of amino acids influenced renal uptake of some conjugates at 1 h after injection, but the difference decreased at later time points. Such information can be helpful for the development of other scaffold protein-based imaging and therapeutic radiolabeled conjugates.

Mechanism of CaM kinase IV activation during hypoxia in neuronal nuclei of the cerebral cortex of newborn piglets: the role of Src kinase

The present study aims to investigate the mechanism of CaM kinase IV activation during hypoxia and tests the hypothesis that hypoxia-induced increased activity of CaM kinase IV is due to Src kinase mediated increased tyrosine phosphorylation of calmodulin and CaM kinase IV in neuronal nuclei of the cerebral cortex of newborn piglets. Piglets were divided into normoxic (Nx, n = 5), hypoxic (Hx, F(i)O(2) of 0.07 for 1 h, n = 5) and hypoxic-pretreated with Src kinase inhibitor PP2 (Hx-Srci, n = 5) groups. Src inhibitor was administered (1.0 mg/kg, I.V.) 30 min prior to hypoxia. Neuronal nuclei were isolated and purified, and tyrosine phosphorylation of calmodulin (Tyr(99)) and CaM kinase IV determined by Western blot using anti-phospho-(pTyr(99))-calmodulin, anti-pTyrosine and anti-CaM kinase IV antibodies. The activity of CaM kinase IV and its consequence the phosphorylation of CREB protein at Ser(133) were determined. Hypoxia resulted in increased tyrosine phosphorylation of calmodulin at Tyr(99), tyrosine phosphorylation of CaM kinase IV, activity of CaM kinase IV and phosphorylation of CREB protein at Ser(133). The data show that administration of Src kinase inhibitor PP2 prevented the hypoxia-induced increased tyrosine phosphorylation of calmodulin (Tyr(99)) and tyrosine phosphorylation of CaM.kinase IV as well as the activity of CaM kinase IV and CREB phosphorylation at Ser(133). We conclude that the mechanism of hypoxia-induced increased activation of CaM kinase IV is mediated by Src kinase-dependent tyrosine phosphorylation of the enzyme and its activator calmodulin. We propose that Tyr(99) phosphorylated calmodulin, as compared to non-phosphorylated, binds with a higher affinity at the calmodulin binding site (rich in basic amino acids) of CaM kinase IV leading to increased activation of CaM kinase IV. Similarly, tyrosine phosphorylated CaM kinase IV binds its substrate with a higher affinity and thus increased tyrosine phosphorylation leads to increased activation of CaM kinase IV resulting in increased CREB phosphorylation that triggers increased transcription of proapoptotic proteins that initiate hypoxic neuronal death.

HDAC inhibitor SNDX-275 enhances efficacy of trastuzumab in erbB2-overexpressing breast cancer cells and exhibits potential to overcome trastuzumab resistance

Trastuzumab (or Herceptin), as the first erbB2-targeted therapy, has been successfully used to treat breast cancer patients with erbB2-overexpressing tumors. However, resistances to trastuzumab frequently occur, and novel strategies/agents are urgently needed to abrogate the resistant phenotype. Our current study explores the potential of SNDX-275, a class I HDAC inhibitor, to overcome trastuzumab resistance and investigates the combinational effects of SNDX-275 and trastuzumab on both sensitive and resistant breast cancer cells. Cell proliferation assays showed that SNDX-275 significantly enhanced trastuzumab-induced growth inhibition in trastuzumab-sensitive, erbB2-overexpressing breast cancer cells. Importantly, SNDX-275 at its therapeutic range re-sensitized trastuzumab-resistant cells to trastuzumab-mediated growth inhibition. SNDX-275 in combination with trastuzumab resulted in a dramatic reduction of erbB3 and its phosphorylation (P-erbB3), and inhibition of Akt signaling. Apoptotic-ELISA and western blot analyses confirmed that the combinations of SNDX-275 and trastuzumab as compared to SNDX-275 alone significantly enhanced DNA fragmentation and induced more PARP cleavage and caspase-3 activation in both trastuzumab-sensitive and -resistant breast cancer cells. Furthermore, co-immunoprecipitation assays revealed that SNDX-275 mainly attenuated the interactions of erbB2 and erbB3 receptors, but had no significant effect on erbB2/IGF-1R or erbB3/IGF-1R associations in the trastuzumab-resistant breast cancer cells. These data indicated that SNDX-275 enhanced trastuzumab efficacy against erbB2-overexpressing breast cancer cells, and exhibited potential to overcome trastuzumab resistance via disrupting erbB2/erbB3 interactions and inactivating PI-3K/Akt signaling. SNDX-275 may be included in erbB2-targeted regimen as a novel strategy to treat breast cancer patients whose tumors overexpress erbB2.

Human epidermal growth factor receptor 2 (HER2) extracellular domain levels are associated with progression-free survival in patients with HER2-positive metastatic breast cancer receiving lapatinib monotherapy

BACKGROUND

Changes in serum human epidermal growth factor receptor 2 (HER2) levels associated with clinical outcomes, including objective response rate, progression-free survival (PFS), and overall survival have been reported in patients with metastatic breast cancer (MBC) receiving trastuzumab and chemotherapy. This study investigated whether baseline or changes in serum HER2 correlated with overall response rate (ORR) and/or PFS in patients with MBC receiving first-line lapatinib monotherapy.

METHODS

The EGF20009 study investigated lapatinib monotherapy in 138 HER2-positive patients with MBC previously untreated for their metastatic disease. Serum was collected and assessed at baseline and every 4 weeks for 16 weeks after treatment initiation. Disease assessment was performed at weeks 8 and 12 and every 12 weeks thereafter. A ≥ 20% decrease or increase in serum HER2 was defined as a significant change.

RESULTS

Seventy-nine percent of patients had elevated baseline serum HER2. Baseline serum HER2 was associated with ORR (P = .043) but not PFS. Patients with a ≥ 20% decrease from baseline of serum HER2 at weeks 4, 8, 12, and 16 had a significantly increased ORR and prolonged PFS. Conversely, those with a ≥ 20% increase from baseline had a significantly lower ORR and shorter PFS.

CONCLUSION

Significant decreases in serum HER2 levels during the first 16 weeks of lapatinib monotherapy were associated with better clinical outcome (longer PFS and increased ORR) in HER2-positive MBC patients.

New targeted therapies for gastric cancer

INTRODUCTION

Inhibitors targeting oncogenic kinases, especially receptor tyrosine kinases (RTKs), are being vigorously developed, and some have been demonstrated to be effective in clinical settings. The amplification of certain RTKs (ErbB2, c-Met and FGFR2) is associated with gastric cancer progression, but the only recently approved inhibitor is trastuzumab, ErbB2-targeting antibody. Other well-known oncogenic kinases (PI3K and RAF) are also activated in a small portion of gastric cancers. Drugs targeting these kinases are promising and should be approved in an appropriate and expeditious way.

AREAS COVERED

This article reviews novel inhibitors emerging in the field of advanced gastric cancer, based on basic research concerning altered oncogenes and the clinical trials of drugs targeting these oncogenes.

EXPERT OPINION

Promising inhibitors of gastric cancer may be found in not only new investigative agents but also agents currently being used against other malignancies. The appropriate design for clinical trials of molecularly targeted therapeutic agents is also important. Targeted therapies tailored to individual genomic profiles would provide a more personalized treatment for advanced gastric cancer.

Brain tissue energy dependence of CaM kinase IV cascade activation during hypoxia in the cerebral cortex of newborn piglets

The present study aims to investigate the dependence of CaM kinase IV cascade activation during hypoxia and tests the hypothesis that hypoxia-induced tyrosine phosphorylation of CaM and CaM kinase IV, activation of CaM kinase IV and phosphorylation of CREB protein during hypoxia increases as a function of increase in cerebral tissue hypoxia as measured by decrease in tissue ATP and phosphocreatine (PCr). 3-5 days old newborn piglets were divided into normoxic (Nx, FiO₂ of 0.21 for 1h) and hypoxic (Hx, FiO₂ of 0.07 for 1h) groups. Cerebral tissue hypoxia was documented by determining the levels of high energy phosphates ATP and phosphocreatine (PCr). Cerebral cortical neuronal nuclei were isolated and purified, and tyrosine phosphorylation of calmodulin (Tyr⁹⁹), the activator of CaM kinase IV, and CaM kinase IV determined by Western blot using anti-phospho-(pTyr⁹⁹)-calmodulin, anti-pTyrosine and anti-CaM kinase IV antibodies. The activity of CaM kinase IV and its consequence the phosphorylation of CREB protein at Ser¹³³ were determined. The levels of ATP (μmole/g brain) ranged from 3.48 to 5.28 in Nx, and 0.41 to 2.26 in Hx. The levels of PCr (μmole/g brain) ranged from 2.46 to 3.91 in Nx and 0.72 to 1.20 in Hx. The pTyr⁹⁹ calmodulin (OD x mm²) ranged from 20.35 to 54.47.60 in Nx, and 84.52 to 181.42 in Hx (r²=0.5309 vs ATP and r²=0.6899 vs PCr). Expression of tyrosine phosphorylated CaM kinase IV ranged from 32.86 to 82.46 in Nx and 96.70 to 131.62 in Hx (r²=0.5132 vs ATP and r²=0.4335 vs PCr). The activity of CaM kinase IV (pmole/mg protein/min) ranged from 1263 to 3448 in Nx and 3767 to 6633 in Hx (r²=0.7113 vs ATP and r²=0.6182 vs PCr). The expression of p-CREB at Ser¹³³ ranged from 44.26 to 70.28 in Nx and 82.70 to 182.86 in Hx (r²=0.6621 vs ATP and r²=0.5485 vs PCr). The data show that hypoxia results in increased tyrosine phosphorylation of calmodulin (Tyr⁹⁹), increased tyrosine phosphorylation of CaM kinase IV, increased activity of CaM kinase IV and increased phosphorylation of CREB at Ser¹³³ as an inverse function of cerebral concentration of high energy phosphates, ATP and PCr. We conclude that the hypoxia-induced increased activation of CaM kinase IV cascade increases with the increase in the degree of cerebral tissue hypoxia as measured by cerebral tissue high energy phosphates in a curvilinear manner. The tyrosine kinases (Src kinase and EGFR kinase) mediated activation of CaM kinase IV cascade potentially results in increased CREB phosphorylation that triggers transcription of proapoptotic proteins during hypoxia.

Optimal specific radioactivity of anti-HER2 Affibody molecules enables discrimination between xenografts with high and low HER2 expression levels

PURPOSE

Overexpression of the HER2 receptor is a biomarker for predicting those patients who may benefit from trastuzumab therapy. Radiolabelled Affibody molecules can be used to visualize HER2 expression in tumour xenografts with high sensitivity. However, previous studies demonstrated that the difference in uptake in xenografts with high and low HER2 expression levels is not proportional to the difference in expression levels. We hypothesized that discrimination between tumours with high and low HER2 expression may be improved by increasing the injected dose (reducing the specific activity) of the tracer.

METHODS

The influence of injected dose of anti-HER2 (111)In-DOTA-Z(HER2 342) Affibody molecule on uptake in SKOV-3 (high HER2 expression) and LS174T (low expression) xenografts was investigated. The optimal range of injected doses enabling discrimination between xenografts with high and low expression was determined. To verify this, tumour uptake was measured in mice carrying both SKOV-3 and LS174T xenografts after injection of either 1 or 15 μg (111)In-DOTA-Z(HER2:342).

RESULTS

An increase in the injected dose caused a linear decrease in the radioactivity accumulation in the LS174T xenografts (low HER2 expression). For SKOV-3 xenografts, the dependence of the tumour uptake on the injected dose was less dramatic. The injection of 10-30 μg (111)In-DOTA-Z(HER2:342) per mouse led to the largest difference in uptake between the two types of tumour. Experiments in mice bearing two xenografts confirmed that the optimized injected dose enabled better discrimination of expression levels.

CONCLUSION

Careful optimization of the injected dose of Affibody molecules is required for maximum discrimination between xenografts with high and low levels of HER2 expression. This information has potential relevance for clinical imaging applications.

Tyrosine kinases in inflammatory dermatologic disease

Tyrosine kinases (TKs) are enzymes that catalyze the phosphorylation of tyrosine residues on protein substrates. They are key components of signaling pathways that drive an array of cellular responses including proliferation, differentiation, migration, and survival. Specific TKs have recently been identified as critical to the pathogenesis of several autoimmune and inflammatory diseases. Small-molecule inhibitors of TKs are emerging as a novel class of therapy that may provide benefit in certain patient subsets. In this review, we highlight TK signaling implicated in inflammatory dermatologic diseases, evaluate strategies aimed at inhibiting these aberrant signaling pathways, and discuss prospects for future drug development.

The role of HER2 in cancer therapy and targeted drug delivery

HER2 is highly expressed in a significant proportion of breast cancer, ovarian cancer, and gastric cancer. Since the discovery of its role in tumorigenesis, HER2 has received great attention in cancer research during the past two decades. Successful development of the humanized monoclonal anti-HER2 antibody (Trastuzumab) for the treatment of breast cancer further spurred scientists to develop various HER2 specific antibodies, dimerization inhibitors and kinase inhibitors for cancer therapy. On the other hand, the high expression of HER2 and the accessibility of its extracellular domain make HER2 an ideal target for the targeted delivery of anti-tumor drugs as well as imaging agents. Although there is no natural ligand for HER2, artificial ligands targeting HER2 have been developed and applied in various targeted drug delivery systems. The emphasis of this review is to elucidate the roles of HER2 in cancer therapy and targeted drug delivery. The structure and signal pathway of HER2 will be briefly described. The role of HER2 in tumorigenesis and its relationship with other tumor markers will be discussed. For the HER2 targeted cancer therapy, numerous strategies including the blockage of receptor dimerization, inhibition of the tyrosine kinase activity, and interruption of the downstream signal pathway will be summarized. For the targeted drug delivery to HER2 positive tumor cells, various targeting ligands and their delivery systems will be described in details.

The vulnerability of the heart as a pluricellular paracrine organ: lessons from unexpected triggers of heart failure in targeted ErbB2 anticancer therapy

In this review, we address clinical aspects and mechanisms of ventricular dysfunction induced by anticancer drugs targeted to the ErbB2 receptor. ErbB2 antagonists prolong survival in cancer, but also interfere with homeostatic processes in the heart. ErbB2 is a coreceptor for ErbB4, which is activated by neuregulin-1. This epidermal growth factor-like growth factor is released from endothelial cells in the endocardium and in the myocardial microcirculation, hence contributing to intercellular crosstalk in the ventricle. We look at the physiological aspects of neuregulin-1/ErbB signaling in the ventricle, and review its (mal)adaptive responses in chronic heart failure. We also compare structural aspects of ErbB receptor activation in cancer and cardiac cells, and analyze the mode of action of current ErbB2 antagonists. This allows us to predict how these drugs interfere with paracrine processes in the ventricle. Differences in the mode of action of individual ErbB2 antagonists affect their impact on the function of the ventricle, considered to be "on-target" or "off-target." Establishing the relation between the cardiac side effects of ErbB2 antagonists and their impact on paracrine ventricular control mechanisms may direct the design of a next generation of ErbB2 inhibitors. For cardiologists, there are lessons to be learned from the unexpected side effects of ErbB2-targeted cancer therapy. The vulnerability of the heart as a pluricellular paracrine system appears greater than anticipated and intercellular crosstalk an essential component of its functional and structural integrity.

Breast cancer genomes--form and function

This review summarizes advances in our understanding of the genomic and epigenomic abnormalities in breast cancers that are being revealed by the increasingly powerful suite of genomic analysis technologies. It summarizes the remarkable genomic heterogeneity that characterizes the disease, describes mechanisms that shape cancer genomes as they evolve toward metastasis, summarizes important recurrent aberrations that exist in spite of the genomic chaos and that contribute to breast cancer pathophysiology, and describes the use of preclinical models to identify drugs that will be effective against subsets of breast cancers carrying specific genomic and epigenomic abnormalities.