A specific vascular endothelial growth factor receptor tyrosine kinase inhibitor enhances the antiproliferative effect of trastuzumab in human epidermal growth factor receptor 2 overexpressing breast cancer cell lines

Crosstalk between HER2 signaling and angiogenesis in breast cancer: molecular basis, clinical applications and challenges

PURPOSE OF REVIEW

Angiogenesis is an essential hallmark of cancer. Targeting angiogenesis has proven its efficacy in the modern therapeutic paradigm. HER2 positive breast cancer, in particular, is a challenging disease in which resistance to standard therapy has been attributed to parallel and downstream signaling cascades including angiogenesis. This review explores the molecular mechanisms underlying crosstalk between HER2 signaling and angiogenesis. It highlights the role of angiogenesis in the emerging resistance to anti-HER2 therapy. It surveys the current repertoire of clinical trials involving use of combination of anti-HER2 and antiangiogenic therapies. Finally, it entertains the hopes and challenges posed by this novel therapeutic approach.

RECENT FINDINGS

HER2 signaling upregulates angiogenesis at different levels and by different mechanisms. A large number of clinical trials were conducted in attempt to exploit the potential benefit of the combination. Results of early phase trials were promising. However, in the late phase clinical trials, the AVEREL trial did not demonstrate a consistent benefit for bevacizumab in the HER2 positive breast cancer patient population. The BETH trial is ongoing and recruiting patients. Safety issues regarding cardiovascular toxicity of the combination have been already raised. Negative experience of dual EGFR and VEGF targeting in colon cancer cannot be overlooked.

SUMMARY

Angiogenesis and HER2 signaling are closely related at the molecular level. Appraisal of efficacy of antiangiogenic therapies requires revisit of the current literature as well as following the results of ongoing trials.

Her-2/neu testing and therapy in gastroesophageal adenocarcinoma

Despite ongoing advances in the treatment of gastroesophageal cancer, prognosis remains poor. The best promise to improve this poor survival is provided by new targeted agents. Of these, human epidermal growth factor receptor 2 (HER2) is currently in the spotlight. In this review, we provide an overview of recent developments in HER2 testing and results of clinical trials targeting HER2 in gastroesophageal adenocarcinoma. Based on the encouraging ToGA trial findings it is now expected that routine HER2 testing will be included in the diagnostic work-up of patients with advanced gastric cancer. With regard to this testing, overexpression of the HER2 protein seems to possess the best predictive properties. However, HER2 immunohistochemistry (IHC) is subject to assay and interobserver variability, so standardization and internal and external proficiency testing is an absolute prerequisite, especially as the IHC scoring system in gastric cancer is different from that of breast cancer. Further study is needed to investigate the clinical meaning of the significant heterogeneity observed in both gene amplification and protein overexpression in gastroesophageal cancer. Highly effective therapies for gastroesophageal cancer can only be accomplished by a multi-targeted approach, considering crosstalk between pathways and continuing to optimize chemotherapy.

Inhibition of ErbB2 by herceptin reduces viability and survival, induces apoptosis and oxidative stress in Calu-3 cell line

Human epidermal growth factor receptor 2 (ErbB2) amplification and overexpression has been seen in many cancer types including non-small cell lung cancer (NSCLC). Thus, ErbB2 is an important target for cancer therapies. Increased ErbB2 expression has been associated with drug resistance in cancer cells. Herceptin is a humanized monoclonal antibody that targets the extracellular domain of ErbB2. In this study, we aimed to block ErbB2 signaling with Herceptin and assess cytotoxicity and effects on apoptosis, oxidative stress, nuclear factor kappa-B (NF-kB), and Survivin expression in Calu-3 cell line. 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay were used to assess cell viability as a marker of proliferation. Acridine orange/ethidium bromide (AO/EB) staining and caspase 3/7 activity were measured as the markers of apoptosis. The relative expressions of NF-kB-p50 and Survivin mRNAs were evaluated. Activities of antioxidant enzymes such as superoxide dismutase (SOD) and catalase (CAT), and the levels of glutathione (GSH) and reactive oxygen species (ROS) were determined in a time- and dose-dependent manner. Our results show that Herceptin treatment inhibits cell proliferation and activates apoptosis but without effects on Survivin and NF-kB expression in Calu-3 cell line. Intracellular glutathione levels and SOD and CAT activities were decreased in a time- and dose-dependent manner associated with oxidative stress. Also, ROS were increased at 24 h. These results provide evidence that Herceptin can be used as a cytotoxic and apoptotic agent in NSCLC.

Artemin stimulates oncogenicity and invasiveness of human endometrial carcinoma cells

Here, we provide evidence for a functional role of artemin (ARTN) in progression of endometrial carcinoma (EC). Increased ARTN protein expression was observed in EC compared with normal endometrial tissue, and ARTN protein expression in EC was significantly associated with higher tumor grade and invasiveness. Forced expression of ARTN in EC cells significantly increased total cell number as a result of enhanced cell cycle progression and cell survival. In addition, forced expression of ARTN significantly enhanced anchorage-independent growth and invasiveness of EC cells. Moreover, forced expression of ARTN increased tumor size in xenograft models and produced highly proliferative, poorly differentiated, and invasive tumors. The ARTN-stimulated increases in oncogenicity and invasion were mediated by increased expression and activity of AKT1. Small interfering RNA-mediated depletion or antibody inhibition of ARTN significantly reduced oncogenicity and invasion of EC cells. Thus, inhibition of ARTN may be considered as a potential therapeutic strategy to retard progression of EC.