The epidermal growth factor receptor family in breast cancer

HER3/Akt/mTOR pathway is a key therapeutic target for the reduction of triple‑negative breast cancer metastasis via the inhibition of CXCR4 expression

Triple‑negative breast cancer (TNBC), a highly metastatic subtype of breast cancer, and it has the worst prognosis among all subtypes of breast cancer. However, no effective systematic therapy is currently available for TNBC metastasis. Therefore, novel therapies targeting the key molecular mechanisms involved in TNBC metastasis are required. The present study examined whether the expression levels of human epidermal growth factor receptor 3 (HER3) were associated with the metastatic phenotype of TNBC, and evaluated the potential of HER3 as a therapeutic target in vitro and in vivo. A new highly metastatic 4T1 TNBC cell line, termed 4T1‑L8, was established. The protein expression levels in 4T1‑L8 cells were measured using luminex magnetic bead assays and western blot analysis. The HER3 expression levels and distant metastasis‑free survival (DMFS) in TNBC were analyzed using Kaplan‑Meier Plotter. Transwell migration and invasion assays were performed to detect migration and invasion. The anti‑metastatic effects were determined in an experimental mouse model of metastasis. The results revealed that the increased expression of the HER3/Akt/mTOR pathway was associated with a greater level of cell migration, invasion and metastasis of TNBC cells. In addition, it was found that high expression levels of HER3 were associated with a poor DMFS. The inhibition of the HER3/Akt/mammalian target of rapamycin (mTOR) pathway decreased the migration, invasion and metastasis of TNBC cells by decreasing the expression of C‑X‑C chemokine receptor type 4 (CXCR4). Furthermore, treatment of metastatic TNBC cells with everolimus inhibited their migration, invasion and metastasis by decreasing CXCR4 expression. Thus, targeting the HER3/Akt/mTOR pathway opens up a new avenue for the development of therapeutics against TNBC metastasis; in addition, everolimus may prove to be an effective therapeutic agent for the suppression of TNBC metastasis.

The role of pro- and antiangiogenic factors in angiogenesis process by Raman spectroscopy

Raman spectroscopy and Raman imaging are powerful techniques to monitor biochemical composition around blood vessel. The aim of this study was to understand the role of pro- and antiangiogenic factors in angiogenesis process. Raman imaging and Raman single spectrum measurements allow the diagnosis of cancer biochemical changes in blood vessel based on several biomarkers simultaneously. We have demonstrated that Raman imaging combined with statistical methods are useful to monitoring pro- and antiangiogenic factors responsible for angiogenesis process. In this work Raman markers of proangiogenic and antiangiogenic factors were identified based on their vibrational signatures. Obtained results can help understand how growing tumor create its vascular system.

Theranostic Advances in Breast Cancer in Nuclear Medicine

The implication of 'theranostic' refers to targeting an identical receptor for diagnostic and therapeutic purposes, by the same radioligand, simultaneously or separately. In regard to extensive efforts, many considerable theranostic tracers have been developed in recent years. Emerging evidence strongly demonstrates the tendency of nuclear medicine towards therapies based on a diagnosis. This review is focused on the examples of targeted radiopharmaceuticals for the imaging and therapy of breast cancer.

Development of a bispecific immune engager using a recombinant malaria protein

As an immune evasion and survival strategy, the Plasmodium falciparum malaria parasite has evolved a protein named VAR2CSA. This protein mediates sequestration of infected red blood cells in the placenta through the interaction with a unique carbohydrate abundantly and exclusively present in the placenta. Cancer cells were found to share the same expression of this distinct carbohydrate, termed oncofetal chondroitin sulfate on their surface. In this study we have used a protein conjugation system to produce a bispecific immune engager, V-aCD3, based on recombinant VAR2CSA as the cancer targeting moiety and an anti-CD3 single-chain variable fragment linked to a single-chain Fc as the immune engager. Conjugation of these two proteins resulted in a single functional moiety that induced immune mediated killing of a broad range of cancer cells in vitro and facilitated tumor arrest in an orthotopic bladder cancer xenograft model.

Avascular tumour growth models based on anomalous diffusion

In this study, we model avascular tumour growth in epithelial tissue. This can help us to understand that how an avascular tumour interacts with its microenvironment and what type of physical changes can be observed within the tumour spheroid before angiogenesis. This understanding is likely to assist in the development of better diagnostics, improved therapies, and prognostics. In biological systems, most of the diffusive processes are through cellular membranes which are porous in nature. Due to its porous nature, diffusion in biological systems are heterogeneous. The fractional diffusion equation is well suited to model heterogeneous biological systems, though most of the early studies did not use this fact. They described tumour growth with simple diffusion-based model. We have developed a spherical model based on simple diffusion initially, and then the model is upgraded with fractional diffusion equations to express the anomalous nature of biological system. In this study, two types of fractional models are developed: one of fixed order and the other of variable order. The memory formalism technique is also included in these anomalous diffusion models. These three models are investigated from phenomenological point view by measuring some parameters for characterizing avascular tumour growth over time. Tumour microenvironment is very complex in nature due to several concurrent molecular mechanisms. Diffusion with memory (fixed as well as variable) formation may be an oversimplified technique, and does not reflect the detailed view of the tumour microenvironment. However, it is found that all the models offer realistic and insightful information of the tumour microenvironment at the macroscopic level, and approximate well the physical phenomena. Also, it is observed that the anomalous diffusion based models offer a closer description to clinical facts than the simple model. As the simulation parameters get modified due to different biochemical and biophysical processes, the robustness of the model is determined. It is found that the anomalous diffusion models are moderately sensitive to the parameters.

Targeted Toxin Gene Therapy Of Breast Cancer Stem Cells Using CXCR1 Promoter And bFGF 5'UTR

Background

Breast cancer stem cells (BCSCs) are cells with a higher ability to metastasis and resistance to conventional treatments. They have a phenotype of (CD44high/CD24low) and the unlimited ability for proliferation. Development of strategies to target the BCSC population may lead to the establishment of more effective cancer therapies. Pseudomonas exotoxin A (PE) is a potent cytotoxic protein. CXCR1 promoter provides BCSC and HER2 specificity on transcription level. 5′UTR of the basic fibroblast growth factor-2 (bFGF 5ʹUTR) provides tumor specificity on translation level. Here, we utilized a mutant form of PE encoding DNA “PE38”, CXCR1 promoter and bFGF 5ʹUTR to target BCSCs.

Methods

The stemness of SK-BR-3, MDA-MB-231 and MCF10A cell lines were evaluated based on the expression of the CD44high/CD24low stem cell signature and the ability to form mammospheres. Then, the cell lines were transfected with constructs encoding luciferase/PE38 under the control of the CMV/CXCR1 promoter with or without bFGF 5′UTR. Luciferase protein expression was evaluated using dual-luciferase reporter assay. PE38 transcript expression was measured by real-time PCR, and the cytotoxic effect of PE38 protein expression was determined by MTT assay.

Results

The percentage of CD44high/CD24low population did not correlate to mammosphere forming efficiency (MFE). Given that the percentage of CD44 high/CD24 low is not a conclusive BCSC profile, we based our work on the mammosphere assay. However, in comparison with MCF10A, the two tumorigenic cell lines had higher MFE, probably due to their higher BCSC content. Reporter assay and real-time PCR results demonstrated that CXCR1 promoter combined with bFGF 5ʹUTR increased BCSC-specific gene expression. Meanwhile, tightly regulated expression of PE38 using these two gene regulatory elements resulted in high levels of cell death in the two tumorigenic cell lines while having little toxicity toward normal MCF10A.

Conclusion

Our data show that PE38, CXCR1 promoter and bFGF 5ʹUTR in combination can be considered as a promising tool for killer gene therapy of breast cancer.

Correlation of epidermal growth factor receptor (EGFR), androgen receptor (AR) and 14-3-3 sigma expression in breast cancer

Epidermal growth factor receptor (EGFR), androgen receptor (AR) and 14-3-3 sigma have been reported to be implicated in breast tumorigenesis. Their correlations, however, remain elusive in this condition. In order to examine the correlation of EGFR, AR and 14-3-3 sigma in breast cancer, and analyze their relationships with molecular subtypes of breast cancer and their impacts on overall survival, we immunohistochemistrically detected EGFR, AR and 14-3-3 sigma expression in 139 cases of breast cancer. We found that EGFR expression was negatively correlated with AR (r=-0.223, P=0.008) and positively with 14-3-3 sigma expression (r=0.181, P=0.033). There were significant differences in EGFR and AR expression between different molecular subtypes (P=0.000 and P=0.000 respectively). Kaplan-Meier cumulative survival analysis showed that none of the three biomarkers had significant impacts on overall survival of breast cancer patients (P=0.315, P=0.709, P=0.789 respectively). Univariate survival analysis revealed that tumor size (P=0.044), lymph node status (P=0.006) and clinical stage (P=0.008) were significantly associated with overall survival. Multivariate analysis demonstrated that lymph node status was the only statistically significant independent prognostic factor for overall survival [P=0.006, exp (B) =1.511, CI (1.124-2.032)]. In conclusion, EGFR expression is negatively correlated with AR and positively with 14-3-3 sigma expression in breast cancer. Furthermore, there are significant differences in EGFR and AR expression between various molecular subtypes of breast cancer. Lastly, EGFR, AR and 14-3-3 sigma have no significant impacts on overall survival of breast cancer patients.

Activation of cancerous inhibitor of PP2A (CIP2A) contributes to lapatinib resistance through induction of CIP2A-Akt feedback loop in ErbB2-positive breast cancer cells

Lapatinib, a small molecule ErbB2/EGFR inhibitor, is FDA-approved for the treatment of metastatic ErbB2-overexpressing breast cancer; however, lapatinib resistance is an emerging clinical challenge. Understanding the molecular mechanisms of lapatinib-mediated anti-cancer activities and identifying relevant resistance factors are of pivotal significance. Cancerous inhibitor of protein phosphatase 2A (CIP2A) is a recently identified oncoprotein that is overexpressed in breast cancer. Our study investigated the role of CIP2A in the anti-cancer efficacy of lapatinib in ErbB2-overexpressing breast cancer cells. We found that lapatinib concurrently downregulated CIP2A and receptor tyrosine kinase signaling in ErbB2-overexpressing SKBR3 and 78617 cells; however, these effects were attenuated in lapatinib-resistant (LR) cells. CIP2A overexpression rendered SKBR3 and 78617 cells resistant to lapatinib-induced apoptosis and growth inhibition. Conversely, CIP2A knockdown via lentiviral shRNA enhanced cell sensitivity to lapatinib-induced growth inhibition and apoptosis. Results also suggested that lapatinib downregulated CIP2A through regulation of protein stability. We further demonstrated that lapatinib-induced CIP2A downregulation can be recapitulated by LY294002, suggesting that Akt mediates CIP2A upregulation. Importantly, lapatinib induced differential CIP2A downregulation between parental BT474 and BT474/LR cell lines. Moreover, CIP2A shRNA knockdown significantly sensitized the BT474/LR cells to lapatinib. Collectively, our results demonstrate that CIP2A is a molecular target and resistance factor of lapatinib with a critical role in lapatinib-induced cellular responses, including the inhibition of the CIP2A-Akt feedback loop. Further investigation of lapatinib-mediated CIP2A regulation will advance our understanding of lapatinib-associated anti-tumor activities and drug resistance.

Role of EGF/ERBB1 in the transcriptional regulation of the prolactin receptor independent of estrogen and prolactin in breast cancer cells

Prolactin receptor (PRLR) and epidermal growth factor receptor (EGFR/ERBB1) have important roles in the physiology of the human breast and in the etiology and progression of breast cancer. Our present studies in MCF-7 cells revealed that EGF induces up-regulation of PRLR via activation of EGFR signalling pathways leading to activation of estrogen receptor α (ERα). EGF treatment of MCF-7 cells cultured in absence of estradiol induced expression of PRLR that was consistent with the activation of PRLR generic promoter (hPIII). These were abolished by ERα antagonist and siRNA, indicating involvement of ERα in EGF-induced hPIII promoter activity. MEK/MAPK and PI3K/AKT pathways participate in the phosphorylation of ERα induced by EGF/EGFR. PI3K and MEK inhibitors abolished EGF-induced PRLR promoter activity. Increased recruitment of non-DNA bound unliganded ERα to Sp1 and C/EBPβ bound to their sites at hPIII induced by EGF was abrogated by ERα siRNA demonstrating the requisite role of phospho-ERα in PRLR upregulation. EGF/EGFR, independent of endogenous prolactin induced phosphorylation of STAT5b with participation of c-SRC and recruitment of STAT5b:STAT5b to a GAS site at hPIII. STAT5b interaction with ERα was essential for stable phospho-ERα recruitment to the SP1/CEBPβ complex. These studies indicate a role for paracrine EGF via EGFR independent of estrogen and prolactin in the transcriptional activation of PRLR gene expression and its contribution to high levels of PRLRs in breast cancer. These by maximizing the actions of endogenous prolactin could have a role in cancer progression and resistance to endocrine therapy.

Hesperetin and Naringenin sensitize HER2 positive cancer cells to death by serving as HER2 Tyrosine Kinase inhibitors

AIM

Aberrant human epidermal growth factor receptor-2 (HER2) expression and constitutive mutant activation of its tyrosine kinase domain account for tumor aggression and therapy resistance in many types of cancers with major share in breast cancer cases. HER2 specific treatment modalities still face challenges owing to the side effects and acquired resistance of available therapeutics. Recently, the anti-proliferative and pro-apoptotic potential of phytochemicals, especially of flavonoids have become increasingly appreciated as powerful chemo preventive agents. Consequently, the major goal of our study is to identify flavonoids capable of inhibiting HER2 Tyrosine Kinase (HER2-TK) activity and validate their anti-tumor activity against HER2 positive tumors.

MAIN METHODS

Molecular docking studies for identifying flavonoids binding at HER2 kinase domain, ADP-Glo™ Kinase Assay for determining kinase activity, MTT assay to measure growth inhibition, various apoptotic assays and cell cycle analysis by FACS were performed.

KEY FINDINGS

Among the flavonoids screened, Naringenin (NG) and Hesperetin (HP) possessed high glide scores from molecular docking studies of enzyme-inhibitor mode. The interaction analysis revealed their ability to establish stable and strong interaction at the ATP binding site of HER2-TK. These compounds also inhibited in vitro HER2-TK activity suggesting their role as HER2 inhibitors. The study also unraveled the anti-proliferative, pro-apoptotic and anti-cancerous activity of these flavonoids against HER2 positive breast cancer cell line.

SIGNIFICANCE

The study identified two citrus fruit flavonoids, NG and HP as HER2-TK inhibitors and this is the first report on their potential to target preferentially and sensitize HER2 positive cancer cells to cell death.

Epidermal growth factor signaling in transformed cells

Members of the epidermal growth factor receptor (EGFR/ErbB) family play a critical role in normal cell growth and development. However, many ErbB family members, especially EGFR, are aberrantly expressed or deregulated in tumors and are thought to play crucial roles in cancer development and metastatic progression. In this chapter, we provide an overview of key mechanisms contributing to aberrant EGFR/ErbB signaling in transformed cells, which results in many phenotypic changes associated with the earliest stages of tumor formation, including several hallmarks of epithelial-mesenchymal transition (EMT). These changes often occur through interaction with other major signaling pathways important to tumor progression, causing a multitude of transcriptional changes that ultimately impact cell morphology, proliferation, and adhesion, all of which are crucial for tumor progression. The resulting mesh of signaling networks will need to be taken into account as new regimens are designed for targeting EGFR for therapeutic intervention. As new insights are gained into the molecular mechanisms of cross talk between EGFR signaling and other signaling pathways, including their roles in therapeutic resistance to anti-EGFR therapies, a continual reassessment of clinical therapeutic regimes and strategies will be required. Understanding the consequences and complexity of EGF signaling and how it relates to tumor progression is critical for the development of clinical compounds and establishing clinical protocols for the treatment of cancer.

HER-3 expression in HER-2-amplified breast carcinoma

Aim of the study

To determine whether the expression of HER-3 influences the survival of HER-2 positive patients with breast cancer (BC).

Material and methods

In the present work, the expression of HER-3 in a group of 35 HER-2 positive patients with BC was studied by performing immunohistochemistry (IHC) in formalin-fixed paraffin embedded tissues.

Results

Higher HER-3 status if estimated by IHC correlated significantly with older age of the patients. HER-3 expression did not correlate with estrogen or progesterone receptor status, pT or pN. There was also no significant difference in disease-free or overall survival (DFS and OS) between groups with different HER-3 expression, although some tendencies were seen as HER-3 expression in over 50% of cells was a factor of worse 5- and 10-year survival.

Conclusions

Further studies should be performed on a larger group of patients to confirm the prognostic role of HER-3 status determined by IHC in BC.

The in vitro influences of epidermal growth factor and heregulin-β1 on the efficacy of trastuzumab used in Her-2 positive breast adenocarcinoma

Background

Human epidermal growth factor receptor-2 (Her-2) is over expressed in approximately 25-30% of all primary breast tumors resulting in a distinctive breast cancer subtype associated with a poor prognosis and a decrease in overall survival. Trastuzumab (Herceptin®), an anti-Her-2 monoclonal antibody, has dramatically altered the prognosis of Her-2 positive breast cancer. Trastuzumab is, however, associated with primary and acquired resistance.

Aim and methods

To investigate the in-vitro effects of trastuzumab on cell viability (tetrazolium conversion assay), cell cycling (propidium iodide staining), apoptosis (executioner caspases and annexin-V) and relative surface Her-2 receptor expression (anti-Her-2 affibody molecule) in Her-2-positive (SK-Br-3) and oestrogen receptor positive (MCF-7) breast adenocarcinoma cells and to determine potential augmentation of these effects by two endogenous ligands, epidermal growth factor (EGF) and heregulin-β1 (HRG- β1).

Results

Cell viability was decreased in SK-Br-3 cells by exposure to trastuzumab. This was associated with G1 accumulation and decreased relative surface Her-2 receptor density, supporting the cytostatic nature of trastuzumab in vitro. SK-Br-3 cells exposed to EGF and heregulin-β1 produced differential cell responses alone and in combination with trastuzumab, in some instances augmenting cell viability and cell cycling. Relative surface Her-2 receptor density was reduced substantially by trastuzumab, EGF and heregulin-β1. These reductions were amplified when ligands were used in combination with trastuzumab.

Conclusion

Cell type specific interactions of endogenous ligands appear to be dependent on absolute Her-receptor expression and cross activation of signaling pathways. This supports the notion that receptor density of Her-family members and multiplicity of growth ligands are of mutual importance in breast cancer cell proliferation and therefore also in resistance associated with trastuzumab.

The HER2 Receptor in Breast Cancer: Pathophysiology, Clinical Use, and New Advances in Therapy

Human epidermal growth factor receptor 2 (HER2) is overexpressed in around 20-30% of breast cancer tumors. It is associated with a more aggressive disease, higher recurrence rate, and increased mortality. Trastuzumab is a HER2 receptor blocker that has become the standard of care for the treatment of HER2 positive breast cancer. The effectiveness of Trastuzumab has been well validated in research as well as in clinical practice. The addition of Trastuzumab to standard of care chemotherapy in clinical trials has been shown to improve outcomes for early stage as well as metastatic HER2 positive breast cancer. The most clinically significant side effect of Trastuzumab is the risk of cardiac myocyte injury, leading to the development of congestive heart failure. The emergence of patterns of resistance to Trastuzumab has led to the discovery of new monoclonal antibodies and other targeted agents aimed at overcoming Trastuzumab resistance and improving survival in patients diagnosed with HER2 positive breast cancers.