The receptor tyrosine kinase Axl in cancer: Biological functions and therapeutic implications

The receptor tyrosine kinase Axl has been implicated in the malignancy of different types of cancer. Emerging evidence of Axl upregulation in numerous cancers, as well as reports demonstrating that its inhibition blocks tumor formation in animal models, highlight the importance of Axl as a new potential therapeutic target. Furthermore, recent data demonstrate that Axl plays a pivotal role in resistance to chemotherapeutic regimens. In this review we discuss the functions of Axl and its regulation and role in cancer development, resistance to therapy, and its importance as a potential drug target, focusing on acute myeloid leukemia, breast, prostate and non‐small cell lung cancers.     

Prognostic, predictive and therapeutic implications of HER2 in invasive epithelial ovarian cancer

The HER2 oncogene encodes a transmembrane protein partially homologous to epidermal growth factor receptor. This oncogene has been studied mainly in breast cancer where it has prognostic, predictive and therapeutic target value. The expression of HER2 in epithelial ovarian cancer has been less studied. HER2 expression can be determined through IHC, FISH, CISH and ELISA among other tests, with reported positivity frequencies of overexpression varying from 1.8% to 76%. In some studies HER2 overexpression has been associated with advanced stages, poorly differentiated tumors, resistance to chemotherapy and shortened survival. Although trastuzumab is able to produce a low response rate as a single agent in pretreated ovarian cancer patients with overexpression of HER2, its usefulness is limited due to the low frequency of strong expression. To date there is not enough bases for assessment and HER2-based therapies in epithelial ovarian cancer.     

Beyond trastuzumab: novel therapeutic strategies in HER2-positive metastatic breast cancer

The use of trastuzumab, a monoclonal antibody that targets the human epidermal growth factor receptor 2 (HER2) alteration present in 25 to 30% of breast cancers, has been associated with improved survival outcomes in both the adjuvant and metastatic settings. However, despite the robust clinical efficacy of trastuzumab in HER2-positive metastatic breast cancer (MBC), primary and secondary resistance remains a clinical challenge. Although lapatinib has demonstrated modest activity in this setting, trials reported to date have yet to demonstrate improvements in overall survival with its use. Novel therapeutic strategies to circumvent trastuzumab resistance are warranted, and agents targeting the HER, vascular endothelial growth factor, heat shock protein 90, phosphoinositide 3 kinase/Akt/mammalian target of rapamycin, and insulin-like growth factor-1 receptor pathways represent rational approaches in the management of HER2-positive disease. In this review, early-phase and emerging trial data surrounding the use of these promising agents in HER2-positive MBC will be discussed.     

Sphingosine kinase 1 as a potential therapeutic target in epithelial ovarian cancer

Sphingosine kinase 1 (SK1) is over‐expressed in multiple types of human cancer. SK1 has growth‐promoting effects and has been proposed as a potential therapeutic target. We investigated the therapeutic effects of SK1 inhibition in epithelial ovarian carcinoma (EOC). SK1 siRNA or inhibitors were tested in EOC cell lines, including A2780, SKOV3ip1, A2780‐CP20, SKOV3‐TR, ES2 and RMG2. Cells were treated with SK inhibitor or FTY720, and cell proliferation, apoptosis, angiogenesis and invasion were examined by MTT, FACS, ELISA and wound‐healing assays, respectively. In vivo experiments were performed to test the effects of FTY720 on tumor growth in orthotopic mouse xenografts of EOC cell lines A2780 or SKOV3ip1 and a patient‐derived xenograft (PDX) model of clear cell ovarian carcinoma (CCC). Blocking SK1 with siRNA or inhibitors significantly reduced proliferation, angiogenesis and invasion, and increased apoptosis in chemosensitive (A2780 and SKOV3ip1) and chemoresistant (A2780‐CP20, SKOV3‐TR, ES2 and RMG2) EOC cells. SK1 inhibitors also decreased the intracellular enzymatic activity of SK1. Furthermore, FTY720 treatment significantly decreased the in vivo tumor weight in xenograft models of established cell lines (A2780 and SKOV3ip1) and a PDX model for CCC compared to control (p < 0.05). These results support therapeutic targeting of SK1 as a potential new strategy for EOC.     

Lapatinib: a novel dual tyrosine kinase inhibitor

Lapatinib is an active and well-tolerated oral dual tyrosine kinase inhibitor that is able to inhibit epidermal growth factor receptor (EGFR) and HER2 with high specificity. It has shown promising activity in several cancers most notably metastatic breast cancer. Lapatinib is active in both trastuzumab-refractory and -naïve breast cancer and a number of phase III studies are ongoing to fully define its activity. Studies have also been conducted in a range of other cancers including renal cell carcinoma. It is essential that future studies incorporate predictive biomarker subgroup analysis. This will help to ensure that important subgroup activity is not missed and also allow the definition of groups most likely to benefit from lapatinib.     

Pazopanib in ovarian cancer

The majority of women with ovarian cancer present with advanced disease, and ultimately relapse following primary surgery and platinum-taxane chemotherapy. Despite recent advances in the development of targeted agents in ovarian cancer, survival rates remain poor. The promising activity of bevacizumab, a VEGF receptor inhibitor, has stimulated research on the use of additional anti-angiogenic agents in ovarian cancer. Pazopanib, an oral tyrosine kinase inhibitor, targets VEGF receptor-1, -2 and -3, platelet-derived growth factor receptor-α and -β and c-kit; resulting in the inhibition of angiogenesis and tumor proliferation. Early phase studies have demonstrated promising efficacy and tolerability. To date, there has been one Phase III trial of pazopanib in ovarian cancer, demonstrating a progression-free survival benefit in women treated with maintenance pazopanib following primary surgery and systemic therapy. This article summarizes the preclinical and clinical data of pazopanib in ovarian cancer, highlighting future research options for this agent.     

Neurotrophic receptor tyrosine kinase family members in secretory and non-secretory breast carcinomas

BACKGROUNDBreast cancer is the most common female cancer and a major cause of morbidity and mortality. Progress in breast cancer therapeutics has been attained with the introduction of targeted therapies for specific sub-sets. However, other subsets lack targeted interventions and thus there is persisting need for identification and characterization of molecular targets in order to advance breast cancer therapeutics.AIMTo analyze the role of lesions in neurotrophic receptor tyrosine kinase (NTRK) genes in breast cancers.METHODSAnalysis of publicly available genomic breast cancer datasets was performed for identification and characterization of cases with fusions and other molecular abnormalities involving NTRK1, NTRK2 and NTRK3 genes.RESULTSNTRK fusions are present in a small number of breast cancers at the extensive GENIE project data set which contains more than 10000 breast cancers. These cases are not identified as secretory in the database, suggesting that the histologic characterization is not always evident. In the breast cancer The Cancer Genome Atlas (TCGA) cohort the more common molecular lesion in NTRK genes is amplification of NTRK1 observed in 7.9% of breast cancers.CONCLUSIONNeurotrophin receptors molecular lesions other than fusions are observed more often than fusions. However, currently available NTRK inhibitors are effective mainly for fusion lesions. Amplifications of NTRK1, being more frequent in breast cancers, could be a viable therapeutic target if inhibitors efficacious for them become available.     

Differential action of small molecule HER kinase inhibitors on receptor heterodimerization: therapeutic implications

Deregulation of ErbB/HER receptor tyrosine kinases has been linked to several types of cancer. The mechanism of activation of these receptors includes establishment of receptor dimers. Here, we have analyzed the action of different small molecule HER tyrosine kinase inhibitors (TKIs) on HER receptor dimerization. Breast cancer cell lines were treated with distinct TKIs and the formation of HER2‐HER3 dimers was analyzed by coimmunoprecipitation and western blot or by Förster resonance energy transfer assays. Antibody‐dependent cellular cytotoxicity was analyzed by measuring the release of lactate dehydrogenase and cell viability. Lapatinib and neratinib interfered with ligand‐induced dimerization of HER receptors; while pelitinib, gefitinib, canertinib or erlotinib did not. Moreover, lapatinib and neratinib were able to disrupt previously formed receptor dimers. Structural analyses allowed the elucidation of the mechanism by which some TKIs prevent the formation of HER receptor dimers, while others do not. Experiments aimed at defining the functional importance of dimerization indicated that TKIs that impeded dimerization prevented down‐regulation of HER2 receptors, and favored the action of trastuzumab. We postulate that TKIs that prevent dimerization and down‐regulation of HER2 may augment the antitumoral action of trastuzumab, and this mechanism of action should be considered in the treatment of HER2 positive tumors which combine TKIs with antireceptor antibodies.     

Molecular target-based cancer therapy: tyrosine kinase inhibitors

Improved understanding of tumor biology has led to the identification of numerous growth factors that are involved in malignant transformation and tumor progression. Many of these factors induce cellular responses through receptors with intrinsic tyrosine kinase (TK) activity. Therefore, inhibiting the activity of TK receptors is one of the ways to effectively block the disordered proliferation of cancer that arises from these pathways. The human epidermal growth factor receptor (HER) family is overexpressed or dysfunctional in many human malignancies. Therefore, these receptors have been identified as targets for cancer therapy. Several agents have been developed that reversibly or irreversibly inhibit one, two, or all of the HER receptors. Iressa and Tarceva are HER1-specific TK inhibitors that are in advanced development. The large phase II study of Iressa (IDEAL1) in patients with non-small-cell lung cancer (NSCLC) in whom previous platinum-based therapy has failed, found that the median survival time (MST) was 7.6 months, which was no less than that with Docetaxel treatment. Other dual or pan-HER, reversible or irreversible, TK inhibitors are being investigated in phase I trials. Early data show that they are generally well tolerated and have provided evidence of against activity tumors. HER-TK inhibitors are likely to have a substantial impact on the treatment of cancer patients.     

Population pharmacokinetics of a HER2 tyrosine kinase inhibitor CP-724,714 in patients with advanced malignant HER2 positive solid tumors

Purpose To develop a population pharmacokinetic (popPK) model for CP-724,714, a novel HER2 tyrosine kinase inhibitor is under development for the treatment of advanced HER2 positive cancers. Methods Concentration-time data (n = 484) from 30 cancer patients receiving daily oral CP-724,714 at doses of 250 mg QD, 250 mg BID, 250 mg TID, and 400 mg BID in 21-day cycles in an open label First-in-Human dose-escalation study were evaluated. Serum concentrations of CP-724,714 were obtained after single dose and at steady state. Nonlinear mixed effect analysis in NONMEM using first order conditional estimation with interaction (FOCEI) was performed. The effect of covariates was assessed. Diagnostic plots, decrease of objective function value (>7.8), bootstrapping, and predictive check were used as model selection criteria. Results A 2-compartment first-order absorption pharmacokinetic (PK) model with inter-subject variability (ISV) on the apparent oral elimination clearance (CL/F), apparent central volume of distribution (V1/F), apparent peripheral volume of distribution (V2/F), and first-order oral absorption rate constant (ka), interoccasion variability (IOV) on CL/F, and body weight (WT) as covariate on CL/F was developed. There was no evidence of dose-dependent and/or time-dependent PK. CL/F increased with increasing WT. The ISV of CL/F was reduced by approximately 20% with WT as a covariate. Age, race, and liver metastasis did not influence CP-724,714 disposition. Conclusions A popPK model was developed that adequately described the pharmacokinetics of CP-724,714. WT was identified as a covariate on CL/F that reduced ISV and improved model performance. Future studies will further assess the importance of WT as a pharmacokinetic covariate. The proposed popPK model can be used to simulate CP-724,714 Phase 2/3 trials.     

Molecular profiling of platinum resistant ovarian cancer

The aim of this study is to discover a gene set that can predict resistance to platinum-based chemotherapy in ovarian cancer. The study was performed on 96 primary ovarian adenocarcinoma specimens from 2 hospitals all treated with platinum-based chemotherapy. In our search for genes, 24 specimens of the discovery set (5 nonresponders and 19 responders) were profiled in duplicate with 18K cDNA microarrays. Confirmation was done using quantitative RT-PCR on 72 independent specimens (9 nonresponders and 63 responders). Sixty-nine genes were differentially expressed between the nonresponders (n=5) and the responders (n=19) in the discovery phase. An algorithm was constructed to identify predictive genes in this discovery set. This resulted in 9 genes (FN1, TOP2A, LBR, ASS, COL3A1, STK6, SGPP1, ITGAE, PCNA), which were confirmed with qRT-PCR. This gene set predicted platinum resistance in an independent validation set of 72 tumours with a sensitivity of 89% (95% CI: 0.68-1.09) and a specificity of 59% (95% CI: 0.47-0.71)(OR=0.09, p=0.026). Multivariable analysis including patient and tumour characteristics demonstrated that this set of 9 genes is independent for the prediction of resistance (p<0.01). The findings of this study are the discovery of a gene signature that classifies the tumours, according to their response, and a 9-gene set that determines resistance in an independent validation set that outperforms patient and tumour characteristics. A larger independent multicentre study should further confirm whether this 9-gene set can identify the patients who will not respond to platinum-based chemotherapy and could benefit from other therapies.     

Epidermal growth factor receptor family tyrosine kinases as signal integrators and therapeutic targets

Activating mutations, gene amplification and overexpression of human epidermal growth factor receptor (erbB or HER) family kinases have been implicated as integral contributors to a variety of cancers. However, there is increasing evidence that the HER family receptors propagate not only signals initiated by their own ligands but also those initiated by multiple other signaling pathways. Attenuation of HER family signaling is a developing strategy for the management of human malignancies and is the subject of a number of ongoing clinical trials. The purpose of this review is to provide a timely update of recent reports in the rapidly evolving area of HER family biology and the emerging integral role of these receptors in malignant transformation and as targets of cancer therapy.     

新型抗Her-2药物T-DM1

T-DM1是新型抗体-药物偶联物,具有曲妥珠单抗类似的生物活性,可特异性的将强效抗微管药物DM1释放至Her-2过表达的肿瘤细胞内。T-DM1单药疗效优于拉帕替尼联合卡培他滨,有望成为Her-2阳性晚期乳腺癌的标准二线治疗药物。比较T-DM1与曲妥珠单抗联合紫杉类药物一线治疗晚期乳腺癌的试验正在进行中。该药是继曲妥珠单抗之后又一种全新的抗Her-2药物。美国FDA正式批准T-DM1作为治疗Her-2阳性晚期乳腺癌患者的药物。      

The type-1 insulin-like growth factor receptor tyrosine kinase and breast cancer: biology and therapeutic relevance

The development of the mammary gland requires the coordinated expression of hormones and growth factors. Likewise, some transformed breast cells continue to respond to these same extracellular signals. Thus, understanding the mechanisms that control normal development of tissues can lead to new therapeutic targets. The insulin-like growth factor (IGF) system plays an important role in the normal development and function of the mammary gland. Accumulating evidence suggests that the IGFs are also key regulators of the malignant phenotype. The IGFs stimulate proliferation, promote survival, and enhance metastatic potential of breast cancer cells. Although multiple receptors for the IGFs have been identified, the IGFs primarily exert their biologic effects through ligation of the type I IGF receptor tyrosine kinase (IGF1R). IGF binding to the IGF1R initiates an intracellular signaling cascade that leads to changes in gene expression and cell biology. This review will focus on the evidence that the IGF1R is a relevant treatment target in breast cancer.     

Evolution of anti-HER2 therapies for cancer treatment

The development of HER2-directed monoclonal antibodies and tyrosine kinase inhibitors have provided benefits to cancer patients, as well as produced many insights into the biology of the ErbB receptor family. Current therapies based on ErbB family members have resulted in improved overall survival with associated improvements in quality of life for the cancer patients that respond to treatment. Compared to monotherapy using either two antibodies to block the HER2 receptor blockade or combinatorial approaches with HER2 antibodies and standard therapies has provided additional benefits. Despite the therapeutic success of existing HER2 therapies, personalising treatment and overcoming resistance to these therapies remains a significant challenge. The heterogeneous intra-tumoural HER2 expression and lack of fully predictive and prognostic biomarkers remain significant barriers to improving the use of HER2 antibodies. Imaging modalities using radiolabelled pertuzumab and trastuzumab allow quantitative assessment of intra-tumoural HER2 expression, HER2 antibody saturation and the success of different drug delivery systems to be assessed. Molecular imaging with HER2 antibodies has the potential to be a non-invasive, predictive and prognostic technique capable of influencing therapeutic decisions, predicting response and failure of treatments as well as providing insights into receptor recycling and signalling. Similarly, conjugating HER2 antibodies with novel toxic payloads or combining HER2 antibodies with cellular immunotherapy provide exciting new opportunities for the management of tumours overexpressing HER2. Future research will lead to higher therapeutic responses, lower toxicities and providing insight into the mechanisms of resistance to HER2-targeted treatments.     

Evaluation of the tyrosine kinase domain of theMet Proto-oncogene in sporadic ovarian carcinomas

Most of the ovarian cancers originate from the ovarian surface epithelium derived from the coelomic mesothelium. The Met proto-oncogene encodes a transmembrane tyrosine kinase receptor (Met) that has the capacity to regulate cell proliferation and differentation and it is activated by hepatocyte growth factor. Trisomy of chromosome 7 and Met protein overexpression have been were observed in ovarian carcinomas, the papillary renal cancers and other solid tumors. Frequent mutations of Met proto-oncogene have been found in hereditary papillary renal cancer (HPRC) and most of the mutations are located in the tyrosine kinase domain. The aim of this study to perform a mutation analysis of exons 17 19 of Met proto-oncogene in epithelial ovarian tumors (EOTs). We have examined 24 tumor samples from patients, operated with EOTs. Mutation was detected in exon 18 in only one sample of 24 EOTs. Our results indicate that mutations located in the Met proto-oncogene is not a common event in EOT. It is not clear whether the mutation plays a role in the tumorigenesis or progression of EOT or not.