Kinase inhibitors in cancer therapy: a look ahead

Design, synthesis, antineoplastic activity of new pyrazolo[3,4-d]pyrimidine derivatives as dual CDK2/GSK3β kinase inhibitors; molecular docking study, and ADME prediction

In the current study, novel pyrazolo[3,4-d]pyrimidine derivatives 5a-h were designed and synthesized as targeted anti-cancer agents through dual CDK2/GSK-3β inhibition. The designed compounds demonstrated moderate to potent activity on the evaluated cancer cell lines (MCF-7 and T-47D). Compounds 5c and 5 g showed the most promising cytotoxic activity against the tested cell lines surpassing that of the used reference standard; staurosporine. On the other hand, both compounds showed good safety and tolerability on normal fibroblast cell line (MCR5). The final compounds 5c and 5 g showed a promising dual CDK2/GSK-3β inhibitory activity with IC50 of 0.244 and 0.128 μM, respectively, against CDK2, and IC50 of 0.317 and 0.160 μM, respectively, against GSK-3β. Investigating the effect of compounds 5c and 5 g on CDK2 and GSK-3β downstream cascades showed that they reduced the relative cellular content of phosphorylated RB1 and β-catenin compared to that in the untreated MCF-7 cells. Moreover, compounds 5c and 5 g showed a reasonable selective inhibition against the target kinases CDK2/GSK-3β in comparison to a set of seven off-target kinases. Furthermore, the most potent compound 5 g caused cell cycle arrest at the S phase in MCF-7 cells preventing the cells' progression to G2/M phase inducing cell apoptosis. Molecular docking studies showed that the final pyrazolo[3,4-d]pyrimidine derivatives have analogous binding modes in the target kinases interacting with the hinge region key amino acids. Molecular dynamics simulations confirmed the predicted binding mode by molecular docking. Moreover, in silico predictions indicated their favorable physicochemical and pharmacokinetic properties in addition to their promising cytotoxic activity.

Pyrazolo[3,4-d]pyrimidine scaffold: A review on synthetic approaches and EGFR and VEGFR inhibitory activities

The pyrazolo[3,4-d]pyrimidine core has received a lot of interest from the medicinal chemistry community as a promising framework for drug design and discovery. It is an isostere of the adenine ring of adenosine triphosphate, which allows it to mimic kinase active site hinge region binding contacts. This scaffold has a wide pharmacological and biological value, one of which is as an anticancer agent. Many successful anticancer medicines have been designed and synthesized using pyrazolo[3,4-d]pyrimidine as a key pharmacophore. The main synthetic routes of pyrazolo[3,4-d]pyrimidines as well as their recent developments as promising anticancer agents acting as endothelial growth factor receptors and vascular endothelial growth factor receptor inhibitors, published in the time frame from 1999 to 2022, are summarized in this review to set the direction for the design and synthesis of novel pyrazolo[3,4-d]pyrimidine derivatives for clinical deployment in cancer treatment.

Discovery of nontriterpenoids from the rot roots of Panax notoginseng with cytotoxicity and their molecular docking study and experimental validation†

Panax notoginseng (PN) is a well-known traditional Chinese medicine, with dammarane-type triterpenoid saponins characterized as major component and active ingredients, together with amino acids, flavonoids, polysaccharides, and polyacetylenes. The roots of PN are susceptible to root rot disease, which causes a huge loss and changes in the chemical components of this precious resource. In this study, sub-fractions of rot PN root extracts were preliminarily found to have admirable cytotoxicity on two human cancer cells. Further bioassay-guided isolation discovered nine new non-triterpenoids, including two novel N-methylacetamido-1-oxotetrahydropyrimidine alkaloids (1, 2), five 2H-furanones or 2H-pyranones (3–7), and two polyacetylenic alcohols (8, 9). Their structures were illuminated by extensive spectroscopic data, calculated ECD, and X-ray diffraction analysis. Among them, 3–7 were considered to be transformed from panaxatriol through the intermediates (8, 9). The new alkaloids (1, 2) displayed noteworthy cytotoxicity against five human cancer cells with IC₅₀ values ranging from 14 to 24 μM. In silico target prediction and molecular docking studies showed that 1 and 2 may interact with EGFR, and were verified by the experimental inhibitory effect on EGFR tyrosine kinase.

Nine new nontriterpenoids were identified from Panax notoginseng rot roots, and their cytotoxicities may be related to the EGFR inhibition.

A systematic comparison of anti-angiogenesis efficacy and cardiotoxicity of receptor tyrosine kinase inhibitors in zebrafish model

Pathological angiogenesis is fundamental to progression of cancerous tumors and blinding eye diseases. Anti-angiogenic receptor tyrosine kinase inhibitors (TKIs) are in broad use for the treatment of these diseases. With more and more TKIs available, it is a challenge to make an optimal choice. It remains unclear whether TKIs demonstrate similar anti-angiogenesis activities in different tissues. Many TKIs have shown varying degrees of toxic effects that should also be considered in clinical use. This study investigates the anti-angiogenic effects of 13 FDA-approved TKIs on the intersegmental vessels (ISVs), subintestinal vessels (SIVs) and retinal vasculature in zebrafish embryos. The results show that vascular endothelial growth factor receptor TKIs (VEGFR-TKIs) exhibit anti-angiogenic abilities similarly on ISVs and SIVs, and their efficacy is consistent with their IC₅₀ values against VEGFR2. In addition, VEGFR-TKIs selectively induces the apoptosis of endothelial cells in immature vessels. Among all TKIs tested, axitinib demonstrates a strong inhibition on retinal neovascularization at a low dose that do not strongly affect ISVs and SIVs, supporting its potential application for retinal diseases. Zebrafish embryos demonstrate cardiotoxicity after VEGFR-TKIs treatment, and ponatinib and sorafenib show a narrow therapeutic window, suggesting that these two drugs may need to be dosed more carefully in patients. We propose that zebrafish is an ideal model for studying in vivo antiangiogenic efficacy and cardiotoxicity of TKIs.

Identification of 3-(piperazinylmethyl)benzofuran derivatives as novel type II CDK2 inhibitors: design, synthesis, biological evaluation, and in silico insights

In the current work, a hybridisation strategy was adopted between the privileged building blocks, benzofuran and piperazine, with the aim of designing novel CDK2 type II inhibitors. The hybrid structures were linked to different aromatic semicarbazide, thiosemicarbazide, or acylhydrazone tails to anchor the designed inhibitors onto the CDK2 kinase domain. The designed compounds showed promising CDK2 inhibitory activity. Compounds 9h, 11d, 11e and 13c showed potent inhibitory activity (IC₅₀ of 40.91, 41.70, 46.88, and 52.63 nM, respectively) compared to staurosporine (IC₅₀ of 56.76 nM). Moreover, benzofurans 9e, 9h, 11d, and 13b showed promising antiproliferative activities towards different cancer cell lines, and non-significant cytotoxicity on normal lung fibroblasts MRC-5 cell line. Furthermore, a cell cycle analysis as well as Annexin V-FITC apoptosis assay on Panc-1 cell line were performed. Molecular docking simulations were performed to explore the ability of target benzofurans to adopt the common binding pattern of CDK2 type II inhibitors.

A medicinal chemist's perspective towards structure activity relationship of heterocycle based anti-cancer agents

AIM

To describe structure activity relationship of heterocyclic derivatives with multi-targeted anticancer activity.

OBJECTIVES

With the following goals in mind, this review tries to describe significant recent advances in the medicinal chemistry of heterocycle-based compounds: (1) To shed light on recent literature focused on heterocyclic derivatives' anticancer potential; (2) To discuss recent advances in the medicinal chemistry of heterocyclic derivatives, as well as their biological implications for cancer eradication; (3) To summarise the comprehensive correlation of structure activity relationship (SAR) with pharmacological outcomes in cancer therapy.

BACKGROUND

Cancer remains one of the major serious health issues devastating the world today. Cancer is a complex disease in which improperly altered cells proliferate at an uncontrolled, rapid, and severe rate. Variables such as poor dietary habits, high stress, age, and smoking, can all contribute to the development of cancer. Cancer can affect almost any organ or tissue, although the brain, breast, liver, and colon are the most frequently affected organs. From several years, surgical operations and irradiation are in use along with chemotherapy as a primary treatment of cancer but still effective treatment of cancer remains a huge challenge. Chemotherapy is now one of the most effective strategies to eradicate cancer, although it has been shown to have a number of cytotoxic and unfavourable effects on normal cells. Despite all of these cancer treatments, there are several other targets for anticancer drugs. Cancer can be effectively eradicated by focusing on these targets, which include both cell-specific and receptor-specific targets such as tyrosine kinase receptors (TKIs). Heterocyclic scaffolds also have a variety of applications in drug development and are a common moiety in the pharmaceutical, agrochemical, and textile industries.

METHODS

The association between structural activity relationship data of many powerful compounds and their anticancer potential in vitro and in vivo has been studied. SAR of powerful heterocyclic compounds can also be generated using molecular docking simulations, as reported vastly in literature.

CONCLUSIONS

Heterocycles have a wide range of applications, from natural compounds to synthesised derivatives with powerful anticancer properties. To avoid cytotoxicity or unfavourable effects on normal mammalian cells due to a lack of selectivity towards the target site, as well as to reduce the occurrence of drug resistance, safer anticancer lead compounds with higher potency and lower cytotoxicity are needed. This review emphasizes on design and development of heterocyclic lead compounds with promising anticancer potential.

Novel oxindole/benzofuran hybrids as potential dual CDK2/GSK-3β inhibitors targeting breast cancer: design, synthesis, biological evaluation, and in silico studies

The serine/threonine protein kinases CDK2 and GSK-3β are key oncotargets in breast cancer cell lines, therefore, in the present study three series of oxindole-benzofuran hybrids were designed and synthesised as dual CDK2/GSK-3β inhibitors targeting breast cancer (5a-g, 7a-h, and 13a-b). The N1 -unsubstituted oxindole derivatives, series 5, showed moderate to potent activity on both MCF-7 and T-47D breast cancer cell lines. Compounds 5d-f showed the most potent cytotoxic activity with IC50 of 3.41, 3.45 and 2.27 μM, respectively, on MCF-7 and of 3.82, 4.53 and 7.80 μM, respectively, on T-47D cell lines, in comparison to the used reference standard (staurosporine) IC50 of 4.81 and 4.34 μM, respectively. On the other hand, the N1 -substituted oxindole derivatives, series 7 and 13, showed moderate to weak cytotoxic activity on both breast cancer cell lines. CDK2 and GSK-3β enzyme inhibition assay of series 5 revealed that compounds 5d and 5f are showing potent dual CDK2/GSK-3β inhibitory activity with IC50 of 37.77 and 52.75 nM, respectively, on CDK2 and 32.09 and 40.13 nM, respectively, on GSK-3β. The most potent compounds 5d-f caused cell cycle arrest in the G2/M phase in MCF-7 cells inducing cell apoptosis because of the CDK2/GSK-3β inhibition. Molecular docking studies showed that the newly synthesised N1 -unsubstituted oxindole hybrids have comparable binding patterns in both CDK2 and GSK-3β. The oxindole ring is accommodated in the hinge region interacting through hydrogen bonding with the backbone CO and NH of the key amino acids Glu81 and Leu83, respectively, in CDK2 and Asp133 and Val135, respectively, in GSK-3β. Whereas, in series 7 and 13, the N1 -substitutions on the oxindole nucleus hinder the compounds from achieving these key interactions with hinge region amino acids what rationalises their moderate to low anti-proliferative activity.

Epidermal growth factor receptor inhibitors as potential anticancer agents: An update of recent progress

Epidermal growth factor receptor (EGFR) is a vital intermediate in cell signaling pathway including cell proliferation, angiogenesis, apoptosis, and metastatic spread and also having four divergent members with similar structural features, such as EGFR (HER1/ErbB1), ErbB2 (HER2/neu), ErbB3 (HER3), and ErbB4 (HER4). Despite this, clinically exploited inhibitors of EGFR (including erlotinib, lapatinib, gefitinib, selumetinib, etc.) are not specific thus provoking unenviable adverse effects. Some of the paramount obstacles to generate and develop new lead molecules of EGFR inhibitors are drug resistance, mutation, and also selectivity which inspire medicinal chemists to generate novel chemotypes. The discovery of therapeutic agents that inhibit the precise stage in tumorous cells such as EGFR is one of the chief successful targets in many cancer therapies, including lung and breast cancers. This review aims to compile the various recent progressions (2016-2021) in the discovery and development of diverse epidermal growth factor receptor (EGFR) inhibitors belonging to distinct structural classes like pyrazoline, pyrazole, imidazole, pyrimidine, coumarin, benzothiazole, etc. We have summarized preclinical and clinical data, structure-activity relationships (SAR) containing mechanistic and in silico studies to provide proposals for the design and invention of new EGFR inhibitors with therapeutic significance. The detailed progress of the work in the field will provide inexorable scope for the development of novel drug candidates with greater selectivity and efficacy.

Design, synthesis, and molecular docking of novel 2-arylbenzothiazole multiangiokinase inhibitors targeting breast cancer

A novel series of 2-arylbenzothiazoles 9, 10, and 12 were designed and synthesized as VEGFR-2/FGFR-1/PDGFR-β multiangiokinase inhibitors targeting breast cancer. Structural elongation of the known 2-phenylbenzothiazole scaffold (type I protein kinase inhibitor [PKI]), was carried out to afford series of type II PKIs 9, 10, and 12. Compounds 9d, 9f, 9i, and 9k exhibited potent multikinase inhibitory activity with IC₅₀ values of 0.19, 0.18, 0.17, and 0.13 μM, respectively, against VEGFR-2; IC₅₀ values of 0.28, 0.37, 0.19, and 0.27 μM, respectively, against FGFR-1; and IC₅₀ values of 0.07, 0.04, 0.08, and 0.14 μM, respectively, against PDGFR-β. Moreover, the synthesized benzothiazoles demonstrated promising cytotoxic activity against the MCF-7 cell line. The most potent benzothiazoles 9d and 9i exhibited IC₅₀ values of 7.83 and 6.58 μM, respectively, on the MCF-7 cell line in comparison to sorafenib (III), which showed IC₅₀  = 4.33 μM. Additionally, 9d and 9i showed VEGFR-2 inhibitory activity in MCF-7 cells of 81% and 83% when compared with sorafenib (III), which showed 88% inhibition. Molecular docking of the designed compounds in the VEGFR-2 and FGFR-1 active sites showed the accommodation of the 2-phenylbenzothiazole moiety, as reported, in the hinge region of the receptor tyrosine kinase (RTK)-binding site, while the amide moiety is involved in hydrogen bond interactions with the key amino acids in the gate area; this in turn directs the aryl group to the hydrophobic allosteric back pocket of the RTKs in a type II-like binding mode. The synthesized benzothiazoles showed satisfactory ADME properties for further optimization in drug discovery.

Novel potent substituted 4-amino-2-thiopyrimidines as dual VEGFR-2 and BRAF kinase inhibitors

In the present study, we report the discovery of a novel class of substituted 4-amino-2-thiopyrimidines as antiangiogenic and antiproliferative agents. Structural hybridization between 4-substituted aminopyrimidines (VEGFR-2 inhibitors) and 2-thioxopyrimidines (BRAF inhibitors) was carried out to afford substituted 4-amino-2-thiopyrimidines as type II dual VEGFR-2/BRAF inhibitors. Our design strategy was tailored such that the 4-amino-2-thiopyrimidine scaffold is to be accommodated in the central gate area of the inactive DFG-out conformation of both enzymes. On one side, the hydrophobic substituent on the 4-amino group would occupy the hydrophobic back pocket and on the other side the substituent on the sulfide moiety should extend to fit in the hinge region (front pocket). Molecular docking simulations confirmed the ability of the designed compounds to accomplish the key interactions in VEGFR-2 and BRAF active sites. Most of the synthesized substituted 4-amino-2-thiopyrimidines demonstrated potent VEGFR-2 inhibitory activity at submicromolar concentrations. Compounds 8a, 8d, 9c and 9e showed IC₅₀ = 0.17, 0.12, 0.17 and 0.19 μM, respectively against VEGFR-2 in comparison to sorafenib (I) IC₅₀ = 0.10 μM and regorafenib (II) IC₅₀ = 0.005 μM. While compounds 9c, 9d and 10a showed IC₅₀ = 0.15, 0.22 and 0.11 μM, respectively against BRAF-WT. At 10 μM concentration 9c revealed promising in vitro broad-spectrum antiproliferative activity against cancer cell lines with growth inhibition percent ranging from 10 to 90%. Moreover, compounds 7b, 8d, 9a, 9b, 9c and 9d showed potent activity against MCF7 cell line (IC₅₀ = 17.18, 17.20, 19.98, 19.61, 13.02 and 16.54 μM, respectively). On the other hand, compounds 9c, 9d and 10d were found to be the most potent compounds against T-47D cell line (IC₅₀ = 2.18, 8.09 and 4.36 μM, respectively). Studying the effect of the most potent compounds on VEGFR-2 level in MCF7 cell line revealed that 9c and 9d showed inhibition percent of 84 and 80%, respectively, in comparison to sorafenib (I) (% inhibition = 90%).

Novel pyrazolo[3,4-d]pyrimidines: design, synthesis, anticancer activity, dual EGFR/ErbB2 receptor tyrosine kinases inhibitory activity, effects on cell cycle profile and caspase-3-mediated apoptosis

A series of novel pyrazolo[3,4-d]pyrimidines was synthesised. Twelve synthesised compounds were evaluated for their anticancer activity against 60 human tumour cell lines by NCI (USA). Compound 7d proved prominent anticancer activity. It showed 1.6-fold more potent anti-proliferative activity against OVCAR-4 cell line with IC₅₀ = 1.74 μM. It also exhibited promising potent anticancer activity against ACHN cell line with IC₅₀ value 5.53 μM, representing 2.2-fold more potency than Erlotinib. Regarding NCI-H460 cell line, compound 7d (IC₅₀ = 4.44 μM) was 1.9-fold more potent than Erlotinib. It inhibited EGFR and ErbB2 kinases at sub-micromolar level (IC₅₀ = 0.18 and 0.25 µM, respectively). Dual inhibition of EGFR and ErbB2 caused induction of apoptosis which was confirmed by a significant increase in the level of active caspase-3 (11-fold). It showed accumulation of cells in pre-G1 phase and cell cycle arrest at G2/M phase.

Type IIA - Type IIB protein tyrosine kinase inhibitors hybridization as an efficient approach for potent multikinase inhibitor development: Design, synthesis, anti-proliferative activity, multikinase inhibitory activity and molecular modeling of novel indolinone-based ureides and amides

Pursuing on our efforts regarding development of novel multikinase inhibitors, herein we report the design and synthesis of novel 2-indolinone-based ureides 6a-u and amides 10a-j. In this work we adopt a hybridization strategy between type IIA PTK inhibitor (sorafenib) and type IIB PTK inhibitors (sunitinib and nintedanib). This was implemented via linking the indolinone core, in both sunitinib and nintedanib, which is well-fitted in the hinge region in the kinase domain front cleft and the biaryl urea extension, in sorafenib, which is accommodated in the gate area and the hydrophobic back pocket. Molecular docking of the designed hybrid compounds in VEGFR-2 and FGFR-1 active sites revealed, as planned, their ability to establish the binding interactions achieved by both original type IIA and type IIB inhibitors. The designed compounds were evaluated for their multikinase inhibitory activity towards VEGFR-2, PDGFR-b and FGFR-1 and anti-proliferative activity towards HepG2, MCF-7, A549 and A498 cancer cell lines. The ureido analogue 6u emerged as the most potent multikinase inhibitor in the ureido series with VEGFR-2, FGFR-1 and PDGFR-b IC₅₀ of 0.18, 0.23 and 0.10 μM, respectively. Whereas, the amido congener 10j emerged as the most potent multikinase inhibitor in the amide series with VEGFR-2, FGFR-1 and PDGFR-b IC₅₀ of 0.28, 0.46 and 0.09 μM, respectively. While, indolinone 6u was the most potent derivative towards HepG2 cells (IC₅₀ = 2.67 ± 0.14 μM), 6r stood out as the most potent indolinone against A498 cells (IC₅₀ = 0.78 ± 0.02 μM). Additionally, the target indolinones displayed non-significant cytotoxic impact towards human normal melanocyte (HFB4). ADME prediction study of the designed compounds showed that they are not only with promising multikinase inhibitory activity but also with favorable pharmacokinetic and drug-likeness properties. Compounds 6r and 10j are revealed to be the best compounds in terms of multikinase activity and pharmacokinetics.

Her-2/Neu Receptor in Prostate Cancer Development and Progression to Androgen Independence

Development of prostate cancer and progression to androgen-independent disease is correlated with increased expression of growth factors and receptors capable of establishing autocrine and/or paracrine growth-stimulatory loops. A thorough review was made of the current literature and recent abstract presentations at scientific meetings focusing on the role of the HER-2/neu (c-erbB2) receptor in prostate cancer and the potential clinical usefulness of its specific inhibitors. In the past 10 years, conflicting results on HER-2/neu expression in prostate cancer have been reported. More recently, four studies have shown experimental evidence of HER-2/neu in the development of prostate cancer and, more specifically, in the progression to a hormone-refractory clinical behavior. Furthermore, it has been proposed that HER-2 family and androgen receptors function synergistically in the absence of androgen, which suggests a crosstalk between the HER-2/neu and androgen receptor pathways. Finally, clinical trials are in progress in prostate cancer patients to test novel agents that selectively interfere with HER-2/neu activity.

Gefitinib (ZD1839, Iressa®): a selective epidermal growth factor receptor-tyrosine kinase inhibitor

Objective: To provide a comprehensive review of the clinical pharmacology and toxicology of gefitinib, with particular attention to its use in early clinical trials.

Data source: A PubMed search was conducted using the terms ZD1839, gefitinib, and epidermal growth factor receptor (EGFR). All data from this search were reviewed and other relevant papers identified. The abstracts from the annual meetings of the American Society of Clinical Oncology were also reviewed.

Data extraction: The aim of the review was to be comprehensive and descriptive. The authors reviewed studies and case reports containing information deemed to be of interest.

Conclusions: EGFR is expressed, overex-pressed, or disregulated in a variety of human solid tumors, resulting in an enhancement of tumor growth. Gefitinib is a selective reversible inhibitor of EGFR that has shown activity in several tumor types. As an oral agent, it is extensively metabolized in the liver through the cytochrome P450 enzyme system, particularly the isoenzyme CYP3A4. In the phase II, IDEAL 1 and 2 trials, gefitinib has shown a response rate of 8.8% -18.4% in refractory lung cancer. Clinical trials in various other nonlung cancer patients include studies of gefitinib as a monotherapy or in combination with various chemotherapy, radiation, and/or hormone therapy regimens. Skin and gastrointestinal toxi-cities are the most frequent adverse events of gefitinib. Recently, interstitial pneumonia has emerged as one of the serious adverse effects among gefitinib patients. In summary, the role of gefitinib in combination or as a monotherapy for a variety of cancers is still evolving.

Angiogenesis, immune system and growth factors: new targets in colorectal cancer therapy

Colorectal cancer is the second most common malignant human neoplasia. Over recent years, many efforts have been performed in order to develop and improve therapeutic protocols, and many advances have been accomplished in both the field of adjuvant and palliative therapy. Most of the chemotherapic agents currently used in the clinical setting are the products of decades of research aimed at inhibiting the uncontrolled growth of dysplastic cells. However, new frontiers in this field have recently been opened, with the identification of key molecules involved in physiologic mechanisms that are of fundamental importance for cancer development and progression. Tumor-induced angiogenesis, the cancer-immune system crosstalk and the effect of growth factors on dysplastic cells represent new fields of investigation for anticancer therapy.

Targeted α-therapy for control of micrometastatic prostate cancer

Carcinoma of the prostate is the second most common cancer in men. In spite of the most aggressive therapies, the control of metastatic prostate cancer remains an elusive objective and many patients die of secondary disease. Targeted alpha-therapy is an emerging therapeutic modality whereby a labeled protein selectively targets cancer cells and delivers a lethal payload, which can kill cancer cells in transit or preangiogenic cell clusters. Recent studies show that targeted alpha-therapy is highly cytotoxic to prostate cancer cells in vitro and can inhibit tumor growth in animal models. This review will consider alpha-emitting radionuclides and current in vitro and in vivo studies with alpha-radioconjugates, and will focus on cell-surface target antigens and targeting vectors for the treatment of prostate cancer.

Targeting the HER2 pathway for the therapy of lower esophageal and gastric adenocarcinoma

INTRODUCTION

The mysteries of complex molecular pathways of tumorigenesis are only beginning to be unraveled. Overexpression of HER2 receptors has been associated with adverse outcomes in certain malignant solid tumors.

AREAS COVERED

The authors give a focused review of the HER2 pathway and its importance for cancer cell survival. Similar to the situation in breast cancer, HER2 overexpression is seen in up to one-quarter of all gastric and gastroesophageal junction adenocarcinomas. The audience will also be familiarized with the existing HER2 targeted agents (both at the bench and at the bedside) for the therapy of gastric and gastroesophageal cancers.

EXPERT OPINION

Despite recent advances, treatment of upper gastrointestinal malignancies remains a significant challenge. Trastuzumab in combination with chemotherapy is the current standard of therapy for patients with metastatic HER2-overexpressing esophageal and gastric cancers. The activity of lapatinib, an active agent in advanced HER2-positive breast cancer, is now being tested in HER2-overexpressing esophageal and gastric adenocarcinomas. A variety of monoclonal antibodies and tyrosine kinase inhibitors with affinity for HER2 are in development and may improve further the outcomes of these malignancies.

Tyrosine kinase inhibitors: Multi-targeted or single-targeted?

Since in most tumors multiple signaling pathways are involved, many of the inhibitors in clinical development are designed to affect a wide range of targeted kinases. The most important tyrosine kinase families in the development of tyrosine kinase inhibitors are the ABL, SCR, platelet derived growth factor, vascular endothelial growth factor receptor and epidermal growth factor receptor families. Both multi-kinase inhibitors and single-kinase inhibitors have advantages and disadvantages, which are related to potential resistance mechanisms, pharmacokinetics, selectivity and tumor environment. In different malignancies various tyrosine kinases are mutated or overexpressed and several resistance mechanisms exist. Pharmacokinetics is influenced by interindividual differences and differs for two single targeted inhibitors or between patients treated by the same tyrosine kinase inhibitor. Different tyrosine kinase inhibitors have various mechanisms to achieve selectivity, while differences in gene expression exist between tumor and stromal cells. Considering these aspects, one type of inhibitor can generally not be preferred above the other, but will depend on the specific genetic constitution of the patient and the tumor, allowing personalized therapy. The most effective way of cancer treatment by using tyrosine kinase inhibitors is to consider each patient/tumor individually and to determine the strategy that specifically targets the consequences of altered (epi)genetics of the tumor. This strategy might result in treatment by a single multi kinase inhibitor for one patient, but in treatment by a couple of single kinase inhibitors for other patients.

Phase I study of icotinib hydrochloride (BPI-2009H), an oral EGFR tyrosine kinase inhibitor, in patients with advanced NSCLC and other solid tumors

PURPOSE

The goal of this study was to assess the safety and tolerability of icotinib hydrochloride (BPI-2009H), a new selective epidermal growth factor receptor tyrosine kinase inhibitor (EGFR TKI), and to explore its pharmacokinetics (PK) and clinical activity in patients with advanced solid tumors, mainly those with non-small-cell lung cancer (NSCLC) after the failure of the prior platinum-based chemotherapy.

EXPERIMENTAL DESIGN

Different doses of oral icotinib were administered once every 8 h (Q8H) for a 28-continuous-day cycle until disease progression and or undue toxicity was observed. PK studies of subjects' blood were performed during cycle one (day 1 through 28). Patients aged ≥18 and ≤70 years with an Eastern Cooperative Oncology Group (ECOG) performance status (PS) of 0-1 and adequate organ functions eligible for the study. Tumor responses were assessed by Response Evaluation Criteria in Solid Tumors (RECIST). K-ras and EGFR mutations in the extracted DNA of fourteen specimens were examined using PCR-based direct sequencing assay.

RESULTS

Thirty-six patients were enrolled in the study. PK analysis demonstrated that the mean elimination half-life of icotinib was 6 h, and the T(max) was around 2 h. The steady-state concentration of icotinib administered at a dose of 125 mg once every 8 h (Q8H) was significantly higher than that achieved by a dose of 100mg Q8H. The most frequent treatment-related adverse events (TRAEs) were an acne-like (folliculitis) rash (16/36, 44.4%), diarrhea (8/36, 22.2%) and a decrease in white blood cells (4/36, 11.1%). The maximum-tolerated dose (MTD) was not reached. Among 33 patients with NSCLC, 7 patients exhibited a partial response, 7 showed stable disease at the 24 weeks. Among 14 patients undergoing DNA sequence for K-ras and EGFR mutations, 3 with K-ras mutation presented 2 stable disease (SD) and 1 partial response (PR), 5 with EGFR exon 19 or 21 mutation 2 PR and 3 SD within 4 weeks.

CONCLUSIONS

Oral icotinib was generally well tolerated, with manageable and reversible adverse events (AEs) and showed positive clinical anti-tumor activities in patients with advanced NSCLC. The recommended dose for phase II/III studies with icotinib is 125 mg or 150 mg Q8H.

Final Report of the First Refractory Germ Cell Tumor Treated with Sunitinib Malate

Patients with advanced germ cell tumors can be cured with cisplatin-based chemotherapy, but the outcome remains unsatisfactory for patients with relapsed disease, including those patients with refractory disease after bone marrow transplantation. Targeted therapies have changed the standard of care for many advanced solid tumors. We have identified, in the literature, potential targets for the treatment of refractory germ cell tumors, and applied to a patient with a refractory disease. We chose sunitinib for this purpose. To our knowledge, this is the first case to be treated with sunitinib, and we have found a promising activity.

Preclinical studies and clinical utilization of monoclonal antibodies in epithelial ovarian cancer

OBJECTIVE

To present an overview of selected monoclonal antibodies (mAbs) that have been studied in epithelial ovarian cancer with a focus on combination treatment with conventional chemotherapy.

METHODS

The authors perform a narrative review of the literature. Preclinical studies that provided rationale for mAb use are examined, and selected clinical trials that evaluated efficacy and tolerability are reviewed.

RESULTS

Numerous mAbs have been utilized in epithelial ovarian cancer, including bevacizumab (anti-vascular endothelial growth factor), trastuzumab (anti-human epidermal growth factor-2), cetuximab (anti-epidermal growth factor receptor), and oregovomab (anti-CA125). Favorable preclinical results have lead to the development of a number of clinical trials. Side-effects have been minimal and combination therapy has been well-tolerated. Efficacy has been variable in the clinical trials.

CONCLUSIONS

Targeted treatment with mAbs in conjunction with cytotoxic chemotherapy has been an important research area during the last decade. This therapeutic approach holds promise for improved outcomes in patients with ovarian cancer.

Molecular-targeted therapies: lessons from years of clinical development

Over the past decade, molecular-targeted therapies have been added to cytotoxic and anti-endocrine drugs in the treatment of cancer, with the aim to target the molecular pathways that underlie the carcinogenic process and maintain the cancer phenotype. Success with some of these agents has suggested that identification and validation of the drug target is the starting point for the route of development of active, safe and effective drugs. Main molecular targets used to the development of anticancer drugs are cell surface receptors, signal transduction pathways, gene transcription targets, ubiquitin-proteasome/heat shock proteins and tumour microenvironment components (especially antiangiogenic agents). Here, we review the development of the main molecular targeted non-cytotoxic agents studied in cancer, highlighting lessons derived from the development of these novel drugs and proposing new horizons for the clinical development of molecular-targeted therapies.

Sunitinib: from rational design to clinical efficacy

Sunitinib (SU011248) is an oral small molecular tyrosine kinase inhibitor that exhibits potent antiangiogenic and antitumor activity. Tyrosine kinase inhibitors such as SU6668 and SU5416 (semaxanib) demonstrated poor pharmacologic properties and limited efficacy; therefore, sunitinib was rationally designed and chosen for its high bioavailability and its nanomolar-range potency against the antiangiogenic receptor tyrosine kinases (RTKs)--vascular endothelial growth factor receptor (VEGFR) and platelet-derived growth factor receptor (PDGFR). Sunitinib inhibits other tyrosine kinases including, KIT, FLT3, colony-stimulating factor 1 (CSF-1), and RET, which are involved in a number of malignancies including small-cell lung cancer, GI stromal tumors (GISTs), breast cancer, acute myelogenous leukemia, multiple endocrine neoplasia types 2A and 2B, and familial medullary thyroid carcinoma. Sunitinib demonstrated robust antitumor activity in preclinical studies resulting not only in tumor growth inhibition, but tumor regression in models of colon cancer, non-small-cell lung cancer, melanoma, renal carcinoma, and squamous cell carcinoma, which were associated with inhibition of VEGFR and PDGFR phosphorylation. Clinical activity was demonstrated in neuroendocrine, colon, and breast cancers in phase II studies, whereas definitive efficacy has been demonstrated in advanced renal cell carcinoma and in imatinib-refractory GISTs, leading to US Food and Drug Administration approval of sunitinib for treatment of these two diseases. Studies investigating sunitinib alone in various tumor types and in combination with chemotherapy are ongoing. The clinical benchmarking of this small-molecule inhibitor of members of the split-kinase domain family of RTKs will lead to additional insights regarding the biology, potential biomarkers, and clinical utility of agents that target multiple signaling pathways in tumor, stromal, and endothelial compartments.

Small molecule tyrosine kinase inhibitors in the treatment of solid tumors: an update of recent developments

Small molecule tyrosine kinase inhibitors (TKIs) are developed to block intracellular signaling pathways in tumor cells, leading to deregulation of key cell functions such as proliferation and differentiation. Over 25 years ago, tyrosine kinases were found to function as oncogenes in animal carcinogenesis; however, only recently TKIs were introduced as anti cancer drugs in human cancer treatment. Tyrosine kinase inhibitors have numerous good qualities. First, in many tumor types they tend to stabilize tumor progression and may create a chronic disease state which is no longer immediately life threatening. Second, side effects are minimal when compared to conventional chemotherapeutic agents. Third, synergistic effects are seen in vitro when TKIs are combined with radiotherapy and/or conventional chemotherapeutic agents. In this article, we will give an update of the tyrosine kinase inhibitors that are currently registered for use or in an advanced stage of development, and we will discuss the future role of TKIs in the treatment of solid tumors. The following TKIs are reviewed: Imatinib (Gleevec/Glivec), Gefitinib (Iressa), Erlotinib (OSI-774, Tarceva), Lapatinib (GW-572016, Tykerb), Canertinib (CI-1033), Sunitinib (SU 11248, Sutent), Zactima (ZD6474), Vatalanib (PTK787/ZK 222584), Sorafenib (Bay 43-9006, Nexavar), and Leflunomide (SU101, Arava).

Sequential administration of docetaxel followed by maintenance gefitinib, as salvage treatment in patients with advanced NSCLC: a multicenter phase II trial

PURPOSE

To evaluate the activity and toxicity of the sequential administration of docetaxel followed by gefitinib in patients with advanced non-small cell lung cancer (NSCLC).

PATIENTS AND TREATMENT

Forty-one patients pre-treated with at least one prior chemotherapy regimen (platinum- or taxane-based) for advanced/metastatic NSCLC received three cycles of docetaxel 30 mg/m2, administered as a 1-h IV infusion, on days 1, 8 and 15 of each 4-week cycle followed by gefitinib 250 mg daily po. Gefitinib treatment was continued until disease progression, development of unacceptable toxicity, or withdrawal of patients consent.

RESULTS

Two (4.9%) patients achieved a partial response and 10 (24.4%) stable disease, for a disease control rate of 29.3% (95% CI: 15.3%-43.2%) while on weekly docetaxel treatment. Additionally, progressive disease (PD) was observed in 29 (70.7%). No objective responses were observed during the gefitinib maintenance therapy; however, 17 (41.5%) patients presented stable disease maintained for more than 2 months. Median time to progression was 3.0 months (range: 1-38.3 months; 95% CI: 2.4-3.6); median overall survival 6.9 months (range: 1.2-40.2 months; 95% CI: 5.34-8.52) while the 1-year survival was 28.8%. Therapy was generally well tolerated with diarrhea and rash being the most frequent toxicities.

CONCLUSIONS

The sequential administration of docetaxel and gefitinib was well tolerated and moderately active against advanced pre-treated NSCLC.

Treatment of primary glioblastoma multiforme with cetuximab, radiotherapy and temozolomide (GERT)--phase I/II trial: study protocol

Background

The implementation of combined radiochemotherapy (RCHT) with temozolomide (TMZ) has lead to a significant increase in overall survival times in patients with Glioblastoma multiforme (GBM), however, outcome still remains unsatisfactory.

The majority of GBMs show an overexpression and/or amplification of the epidermal growth factor receptor (EGFR). Therefore, addition of EGFR-inhibition with cetuximab to the current standard treatment approach with radiotherapy and TMZ seems promising.

Methods/design

GERT is a one-armed single-center phase I/II trial. In a first step, dose-escalation of TMZ from 50 mg/m² to 75 mg/m² together with radiotherapy and cetuximab will be performed. Should safety be proven, the phase II trial will be initiated with the standard dose of 75 mg/m² of TMZ. Cetuximab will be applied in the standard application dose of 400 mg/m² in week 1, thereafter at a dose of 250 mg/m² weekly. A total of 46 patients will be included into this phase I/II trial.

Primary endpoints are feasibility and toxicity, secondary endpoints are overall and progression-free survival. An interim analysis will be performed after inclusion of 15 patients into the main study. Patients' enrolment will be performed over a period of 2 years. The observation time will end 2 years after inclusion of the last patient.

Discussion

The goal of this study is to evaluate the safety and efficacy of combined RCHT-immunotherapy with TMZ and cetuximab as first-line treatment for patients with primary GBM.

HER1/EGFR tyrosine kinase inhibitors for the treatment of glioblastoma multiforme

Glioblastoma multiforme (GBM) is a highly malignant brain tumor with limited therapeutic options, a high recurrence rate and mortality. Standard therapy is maximal surgical resection and radiotherapy (RT). Recent data suggest combining temozolomide with RT is better than RT alone. Adjuvant chemotherapy has a modest impact on survival. For relapsed patients there is no standard therapy, but options include chemotherapeutic agents or new agents in development. One approach to improve outcome is using targeted agents that interfere with cell-surface receptors or intracellular signaling pathways. Between 40% and 50% of GBM tumors show HER1/EGFR dysregulation, and almost half co-express the constitutively active mutant receptor subtype EGFRvIII, which may contribute to the aggressive and refractory course of GBM. Numerous studies show a relationship between aberrant HER1/EGFR biology and tumorigenicity in GBM cells. Two available HER1/EGFR tyrosine kinase inhibitors (TKIs) are gefitinib (Iressa) and erlotinib (Tarceva); both show antitumor and radiosensitization effects in vitro and in animal models of GBM. Clinical trials in patients with GBM and other gliomas are ongoing. Preliminary and published results from trials of gefitinib in recurrent GBM show no increased time to progression or overall survival (OS) compared with historical controls. Studies with erlotinib show greater antitumor activity in patients with GBM than with gefitinib, although the impact of both agents on OS remains unclear. GBM treatment with HER1/EGFR TKIs alone or combined with other targeted therapies and conventional modalities deserve further investigation and refinement, as does our understanding of their mechanisms of action and the role of genetics.

The promise of molecular targeted therapies: Protein kinase inhibitors in the treatment of cutaneous malignancies

A new revolution in cancer therapy has arrived with the development of agents targeting cancer-related protein kinases, critical regulators of malignant behavior. These drugs are selective inhibitors of protein kinases, which mediate most signal transduction pathways in malignant cells and result in increased proliferation, evasion of apoptosis, invasion, and metastasis. Protein kinases are the second largest group of drug targets and they account for 20% to 30% of the drug discovery programs of many biotechnology and pharmaceutical companies. A critical review of the literature is performed, highlighting selective inhibitors of signal transduction molecules involved in nonmelanoma skin cancer, melanoma, dermatofibrosarcoma protuberans, Merkel cell carcinoma, Kaposi's sarcoma, and systemic mastocytosis. Clinical studies were identified by searches of the Proceedings of the American Society of Clinical Oncology Annual Meetings, MedLine, and www.clinicaltrials.gov. Clinical trials of kinase inhibitors in study populations are illustrated, highlighting early results, side effects, and potential improvements in outcomes. Case series and case reports were included for rare diseases. These drugs will have important implications in clinical dermatology, based on their expected frequent use in the treatment of dermatologic malignancies, and their associated cutaneous side effects.

Role of tyrosine kinase inhibitors in cancer therapy

Cancer chemotherapy has been one of the major medical advances in the last few decades. However, the drugs used for this therapy have a narrow therapeutic index, and often the responses produced are only just palliative as well as unpredictable. In contrast, targeted therapy that has been introduced in recent years is directed against cancer-specific molecules and signaling pathways and thus has more limited nonspecific toxicities. Tyrosine kinases are an especially important target because they play an important role in the modulation of growth factor signaling. This review focuses on small molecule inhibitors of tyrosine kinase. They compete with the ATP binding site of the catalytic domain of several oncogenic tyrosine kinases. They are orally active, small molecules that have a favorable safety profile and can be easily combined with other forms of chemotherapy or radiation therapy. Several tyrosine kinase inhibitors (TKIs) have been found to have effective antitumor activity and have been approved or are in clinical trials. The inhibitors discussed in this manuscript are imatinib mesylate (STI571; Gleevec), gefitinib (Iressa), erlotinib (OSI-1774; Tarceva), lapatinib (GW-572016), canertinib (CI-1033), semaxinib (SU5416), vatalanib (PTK787/ZK222584), sorafenib (BAY 43-9006), sutent (SU11248), and leflunomide (SU101). TKIs are thus an important new class of targeted therapy that interfere with specific cell signaling pathways and thus allow target-specific therapy for selected malignancies. The pharmacological properties and anticancer activities of these inhibitors are discussed in this review. Use of these targeted therapies is not without limitations such as the development of resistance and the lack of tumor response in the general population. The availability of newer inhibitors and improved patient selection will help overcome these problems in the future.

Review article: the potential of combinational regimen with non-steroidal anti-inflammatory drugs in the chemoprevention of colorectal cancer

Non-steroidal anti-inflammatory drugs are chemopreventive agents in colorectal cancer. Non-steroidal anti-inflammatory drugs do not, however, offer complete protection against adenoma and carcinoma development. There is increasing interest in combining non-steroidal anti-inflammatory drugs with agents that target specific cell signalling pathways in malignant and premalignant cells. This review aims to describe the current knowledge regarding the efficacy of peroxisome proliferator-activated receptor-gamma ligands, cholesterol synthesis inhibitors (statins), epidermal growth factor signalling inhibitors and tumour necrosis factor-related apoptosis-inducing ligand against colorectal neoplasms and the rationale for combining these drugs with non-steroidal anti-inflammatory drugs to improve efficacy in the chemoprevention of colorectal cancer, a PUBMED computer search of the English language literature was conducted to identify relevant papers published before July 2004. Peroxisome proliferator-activated receptor-gamma ligands and statins, both in clinical use, reduce the growth rate of human colon cancer cells in vitro and in rodents models. In vitro, preclinical in vivo and clinical studies have shown efficacy of epidermal growth factor signalling inhibition in colorectal cancer. In vitro, tumour necrosis factor-related apoptosis-inducing ligand induces apoptosis in human colon cancer cells, but not in normal cells. These drugs have all been shown to interact with non-steroidal anti-inflammatory drugs in colorectal cancer cells and/or in rodent models. Combinational regimen are a promising strategy for the chemoprevention of colorectal cancer and should be further explored.

HER1/EGFR targeting: refining the strategy

Human epidermal growth factor receptor (EGFR), HER, targeting has formed the basis of extensive and growing drug development programs in various companies. However, receptor biology is often poorly explained and confusing. The HER family of four naturally occurring receptors and one tumor-specific mutant can activate signaling via a complex and sophisticated range of mechanisms, which we are only beginning to understand. HER1/EGFR downstream signaling can lead to tumor growth and development via a host of processes, including enhanced cellular proliferation, survival, and metastasis. A range of potential therapeutic targets exists within the HER signaling system, both inside and outside the cell. Monoclonal antibodies and tyrosine kinase inhibitors, acting extracellularly and intracellularly, respectively, comprise two classes of agents most advanced in clinical development or already available for use. Despite promising single-agent activity in chemotherapy-resistant patients with non-small cell lung cancer (NSCLC), disappointing results from two phase III trials of the tyrosine kinase inhibitor gefitinib in NSCLC have been of concern to some. However, many factors may have contributed to this outcome, and it is not necessarily predictive of the future usefulness of these agents. Patient characteristics, lack of patient selection, dosing schedule, and trial design may all have played roles. It is important to remember that intracellular targeting of HER is a relatively novel approach, and our knowledge of how best to optimize such treatment is still unfolding. More clinical experience is needed.

Local cyclin-dependent kinase inhibition by flavopiridol inhibits coronary artery smooth muscle cell proliferation and migration: Implications for the applicability on drug-eluting stents to prevent neointima formation following vascular injury

In-stent restenosis is a hyperproliferative disease which can be successfully treated by drug-eluting stents releasing compounds that exhibit cell-cycle inhibitory properties to inhibit coronary smooth muscle cell (CASMC) proliferation and migration, resembling the key pathomechanisms of in-stent restenosis. Cyclin-dependent kinases (CDK) are key regulators of the eukaryotic cell cycle. CDK activity may be blocked by novel compounds such as flavopiridol. Therefore, CDK inhibitors are attractive drugs to be used for the local prevention of in-stent restenosis. In this study, we demonstrate that flavopiridol leads to potent inhibition of CASMC proliferation and migration. Molecular effects on cell-cycle regulatory mechanisms and distribution were evaluated by post-transcriptional assessment of distinct cyclins and cyclin-dependent kinase inhibitor (CKI) levels and flow cytometry. Cellular necrosis and apoptosis was assessed in CASMC and coronary endothelial cells. Flavopiridol induced a potent antiproliferative effect by cell-cycle inhibition in G1 and G2/M and led to increased protein levels of CKIs p21cip1 and p27kip1 as well as p53 in CASMC. Hyperphosphorylation of retinoblastoma protein was abrogated and mitogen-mediated smooth muscle cell migration significantly reduced. No accelerated cytotoxicity or increased apoptosis was detectable. Flavopiridol-coated stents, implanted in rat carotid arteries, led to significant decrease of neointima formation. As proof of principle, our results demonstrate that stents eluting CDK inhibitors such as flavopiridol effectively inhibit neointima formation. Therefore, this new class of therapeutics may be suitable for further clinical investigations on drug-eluting stents to prevent in-stent restenosis.

The HER receptor family: a rich target for therapeutic development

PURPOSE

The key role of the HER family of receptors in cancer has been widely acknowledged. HER receptor activation occurs via ligand binding or nonligand-dependent receptor dimerization, initiating signals that promote tumorigenesis via cell proliferation, survival, migration, adhesion, and differentiation. Therapeutic strategies designed to target and inhibit HER activation that are in clinical development are reviewed, including examples of both small-molecule tyrosine kinase inhibitors and monoclonal antibodies.

MATERIALS AND METHODS

A literature review.

RESULTS

Tarceva is a potent, highly selective, reversible inhibitor of HER1/epidermal growth factor receptor tyrosine kinase with inhibitory activity against various in vitro and in vivo models of solid human tumors. Phase II trials in refractory non-small-cell lung, head-and-neck, and ovarian cancer have demonstrated clinical activity, including objective responses and prolonged, stable disease. Four Phase III trials are ongoing evaluating primarily the effect on survival of Tarceva in combination with chemotherapy. 2C4 is a humanized anti-HER2 monoclonal antibody that binds to a broad, extracellular epitope, resulting in steric inhibition of HER-receptor complex formation that involves HER2. 2C4 has shown significant activity in xenograft models of prostate, lung, and breast cancer. 2C4's activity, unlike Herceptin's, is not dependent on HER2 amplification. This antibody is in early clinical development.

CONCLUSION

The strategy of targeting the HER system has been further validated by early experience with Tarceva and 2C4. The optimal clinical benefit of these agents will likely involve combinations of biologic agents, with or without traditional chemotherapy, and will be guided by critical predictive diagnostic information.

Adenosine-anchored triphosphate subsite probing: distinguishing between HER-2 and HER-4 tyrosine protein kinases

A strategy of full-site occupancy and stereospecific recognition in the triphosphate subsite was used to specifically inhibit two protein kinases HER-2 and HER-4 from the EGFR family. The SAR profiles of a panel of adenosine-anchored bicyclic heterocycles against HER-2 and HER-4 indicated that specificity can be derived for highly homologous protein kinases from stereospecific recognition in the triphosphate-subsite.

Molecular targets in cancer therapy

OBJECTIVES

To review selected pharmacologic agents that target key cellular processes along with their mechanisms of action and adverse events. Nursing implications including what patients and families need to know, administration issues, and management of common toxicities will be reviewed.

DATA SOURCES

Research articles, clinical trials, abstracts, and book chapters.

CONCLUSION

Knowledge of complex biology and biochemistry regulating normal and abnormal cellular function obtained over the past 30 years is starting to be used clinically for new therapies to treat cancer. By targeting what makes cancer unique, these therapies are able to spare more healthy or normal cells than the standard treatments, such as radiation and chemotherapy. Several molecular targeting agents are now in use and even more are under study as cancer treatments.

IMPLICATIONS FOR NURSING PRACTICE

Oncology nurses must understand the principles underlying targeted treatments and their potential benefits to provide adequate patient education and care.

Novel approaches with targeted therapies in bladder cancer. Therapy of bladder cancer by blockade of the epidermal growth factor receptor family

The improved understanding of the molecular biology of urothelial malignancies is helping to define the role of new targets and prognostic indices that can direct the most appropriate choice of treatment for advanced disease. Many human tumors express high levels of growth factors and their receptors that can be used as potential therapeutical targets. Tyrosine-kinase receptors, including many growth factor receptors such the receptors for epidermal growth factor (EGF), vascular endothelial growth factor (VEGF), and Her2/neu, have been found overexpressed in urothelial tumors. For many of these growth factor receptors, the degree of expression has been associated with the progression of cancer and a poor prognosis. Among the best studied growth factor receptors are the two members of EGF receptor familiy EGFr (ErbB-1), and Her2/neu (ErbB-2). Several preclinical studies in bladder cancer models, have confirmed that systemic administration of growth factor inhibitors inhibits the growth and metastasis of human transitional cell carcinoma established in the bladder wall of athymic nude mice. Additional studies indicate that therapy with EGFR inhibitors enhances the activity of conventional cytoreductive chemotherapeutic agents, in part by inhibiting tumor cell proliferation, angiogenesis, and inducing apoptosis. Novel targeted therapy hold promise to improve the current results of bladder cancer treatment. Based on the success seen with anti-HER2 monoclonal antibodies (Herceptin) and the promising results with EGFR targeted agents (IMC-C225 Cetuximab, ZD1389 Iressa, OSI-774 Tarceva, GW 57016) in other tumor types, and based on the results obtained in preclinical models, there is a great interest in assessing these agents in patients with bladder cancer. Several trials are now ongoing testing these new agents alone or in combination with chemotherapy in bladder cancer patients. The integration of these newer biologic agents, probably to supplement rather than to supplant chemotherapeutic drugs, should be a primary direction of research with the objective to interfere with multiple aspects of bladder cancer progression. However, the value of integration of biologically targeted agents into combined modality treatment for patients with bladder cancer has still to be proven.

ZD1839, a novel, oral epidermal growth factor receptor-tyrosine kinase inhibitor, as salvage treatment in patients with advanced non-small cell lung cancer. Experience from a single center participating in a compassionate use program

OBJECTIVE

We evaluated the efficacy and tolerability of the orally active, selective epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI) ZD1839 in patients with pretreated advanced non-small cell lung cancer (NSCLC) participating in a compassionate use program.

PATIENTS AND METHODS

Thirty-one patients with advanced, unresectable and progressive NSCLC, previously treated with one or two chemotherapy regimens, received ZD1839 250 mg orally once daily. Patients who had received only one prior chemotherapy regimen had to be considered unsuitable for second-line chemotherapy.

RESULTS

The disease control rate was 32% (95% CI: 15.8-48.7) (1/31 patients had a partial response and 9/31 patients had stable disease) and the median overall survival 23 weeks (range 4-40). Symptom improvement was reported by 39% of patients overall and by 83% of patients who achieved disease control. The median time to symptom improvement was 3 weeks (range 2-4). Adverse events were generally mild (grade I or II) and reversible and consisted mostly of skin rash, diarrhea and fatigue.

CONCLUSIONS

ZD1839 demonstrated clinically meaningful antitumor activity with significant improvement in symptoms in this heavily pretreated group of patients with advanced NSCLC. Furthermore, ZD1839 showed a favorable toxicity profile, with the majority of adverse events being mild and reversible.

Involvement of Growth Factor Receptors of the Epidermal Growth Factor Receptor Family in Prostate Cancer Development and Progression to Androgen Independence

The development of prostate cancer and the progression from a normal prostate epithelium to androgen-dependent cancer and eventually to hormone-refractory prostate cancer is a multistep process involving several changes in the function of different growth-regulatory signals. In the past 10 years, conflicting results on epidermal growth factor receptor (EGFR) family expression in prostate cancer have been reported. These differences may result from technical differences, lack of standardization of immunohistochemical assays, or different scoring methodologies. Recently, 4 studies have shown experimental evidence of a role of the EGFR family, particularly ErbB-2, in the development of prostate cancer and, more specifically, in the progression to hormone-refractory clinical behavior. These 4 studies were similar in some relevant aspects, such as the patient population. In fact, the patients in each study were divided into 3 groups that represent the progression of prostate cancer. In 3 of 4 studies, a statistically significant increase in ErbB-2 expression was detected by immunohistochemistry in the progression from hormone-dependent to hormone-independent disease. The expression of EGFR was also evaluated in 1 of the 4 studies. In a recent report from our group, a significant increase in EGFR expression was observed in patients treated with radical surgery, in patients who received hormonal therapy as primary therapy before radical prostatectomy, and, finally, in patients with metastatic and hormone-refractory disease. It has been proposed that EGFR family receptors and androgen receptors function synergistically in the absence of androgen suggesting cross-talk between the ErbB-2 and androgen receptor pathways, and that mitogen-activated protein kinase and phosphatidylinositol 3-kinase can be considered the transduction pathways. Finally, clinical trials are currently in progress in patients with prostate cancer testing novel agents that selectively interfere with these receptors, such as trastuzumab, an anti- ErbB-2 monoclonal antibody, and gefitinib (ZD1839, Iressa), a small-molecule selective EGFR tyrosine kinase inhibitor.

Properties and regulation of the bifunctional enzyme HPr kinase/phosphatase in Bacillus subtilis

The bifunctional allosteric enzyme HPr kinase/phosphatase (HPrK/P) from Bacillus subtilis is a key enzyme in the main mechanism of carbon catabolite repression/activation (i.e. a means for the bacteria to adapt rapidly to environmental changes in carbon sources). In this regulation system, the enzyme can phosphorylate and dephosphorylate two proteins, HPr/HPr(Ser(P)) and Crh/Crh(Ser(P)), sensing the metabolic state of the cell. To acquire further insight into the properties of HPrK/P, electrospray ionization mass spectrometry, dynamic light scattering, and BIACORE were used to determine the oligomeric state of the protein under native conditions, revealing that the enzyme exists as a hexamer at pH 6.8 and as a monomer and dimer at pH 9.5. Using an in vitro radioactive assay, the influence of divalent cations, pH, temperature, and different glycolytic intermediates on the activity as well as kinetic parameters were investigated. The presence of divalent cations was found to be essential for both opposing activities of the enzyme. Furthermore, pH values equal to the internal pH of vegetative cells seem to favor the kinase activity, whereas lower pH values increased the phosphatase activity. Among the glycolytic intermediates evaluated, fructose 1,6-diphosphate and fructose 2,6-diphosphate were found to be allosteric activators in the kinase assay, whereas high concentrations inhibited the phosphatase activity, except for fructose 1,6-diphosphate in the case of HPr(Ser(P)). Phosphatase activity was induced by inorganic phosphate as well as acetyl phosphate and glyceraldehyde 3-phosphate. Kinetic parameters indicate a preference for binding of HPr compared with Crh to the enzyme and supported a strong positive cooperativity. This work suggests that the oligomeric state of the enzyme is influenced by several effectors and is correlated to the kinase or phosphatase activity. The phosphatase activity is mainly supported by the hexameric form.

Transmembrane helix predictions revisited

Methods that predict membrane helices have become increasingly useful in the context of analyzing entire proteomes, as well as in everyday sequence analysis. Here, we analyzed 27 advanced and simple methods in detail. To resolve contradictions in previous works and to reevaluate transmembrane helix prediction algorithms, we introduced an analysis that distinguished between performance on redundancy-reduced high- and low-resolution data sets, established thresholds for significant differences in performance, and implemented both per-segment and per-residue analysis of membrane helix predictions. Although some of the advanced methods performed better than others, we showed in a thorough bootstrapping experiment based on various measures of accuracy that no method performed consistently best. In contrast, most simple hydrophobicity scale-based methods were significantly less accurate than any advanced method as they overpredicted membrane helices and confused membrane helices with hydrophobic regions outside of membranes. In contrast, the advanced methods usually distinguished correctly between membrane-helical and other proteins. Nonetheless, few methods reliably distinguished between signal peptides and membrane helices. We could not verify a significant difference in performance between eukaryotic and prokaryotic proteins. Surprisingly, we found that proteins with more than five helices were predicted at a significantly lower accuracy than proteins with five or fewer. The important implication is that structurally unsolved multispanning membrane proteins, which are often important drug targets, will remain problematic for transmembrane helix prediction algorithms. Overall, by establishing a standardized methodology for transmembrane helix prediction evaluation, we have resolved differences among previous works and presented novel trends that may impact the analysis of entire proteomes.

ZD1839 (Iressa): for more than just non-small cell lung cancer

ZD1839 (Iressa) is an orally active, selective epidermal growth factor receptor tyrosine kinase inhibitor that blocks signal transduction pathways involved in cell proliferation. Preclinical studies demonstrated that ZD1839 is a promising agent for the treatment of a wide range of tumors and has additive-to-synergistic effects when combined with radiation or chemotherapy in various cell lines and xenografts. Phase I clinical trials have reported that ZD1839 has acceptable tolerability and antitumor activity. In addition to non-small cell lung cancer, phase II/III studies are currently investigating ZD1839 as monotherapy or in combination therapy against prostate, breast, head and neck, gastric, and colorectal tumors.