Quantitative measurement of epidermal growth factor receptor is a negative predictive factor for tamoxifen response in hormone receptor positive premenopausal breast cancer

Epidermal growth factor receptor (EGFR) and vascular endothelial growth factor A (VEGF-A) expressions in Ethiopian female breast cancer and their association with histopathologic features

BACKGROUND

Epidermal growth factor receptor (EGFR) and vascular endothelial growth factor receptor (VEGF) play important role in breast tumor growth, invasion, metastasis, patient survival and drug resistance. The aim of this study was to evaluate the protein expression status of EGFR and VEGF-A, as well as their association with hormone receptor status and histopathological characteristics in the invasive type of female breast cancer among Ethiopians.

METHOD

The primary breast tumor tissues were obtained from 85 Ethiopian invasive breast cancer cases that underwent modified radical mastectomy (MRM) from June 2014 to June 2015. Their FFPE blocks were analyzed for EGFR and VEGF protein expressions using immunohistochemical techniques. The expressions were also correlated with histopathologic features.

RESULT

Epidermal growth factor receptor over-expression was observed in 22% of the tumor samples. VEGF-A expression was negative in 13.41%, low in 63.41%, moderate in 20.73%, and high in 2.44%. EGFR expression, but not VEGF-A, showed a significant inverse correlation with both estrogen receptor (ER) (P = 0.01) and progesterone receptor (PR) statuses (P = 0.04). EGFR and VEGF expressions did not show significant association with tumor size, grade, lymph node status or age at diagnosis.

CONCLUSION

Epidermal growth factor receptor expression was most likely associated with ER and PR negative tumors. Assessments of multiple molecular markers aid to understand the biological behavior of the disease in Ethiopian population. It might also help to predict which group of patients might get more benefit from the selected treatment strategies and which are not.

89Zr-Labeled Domain II-Specific scFv-Fc ImmunoPET Probe for Imaging Epidermal Growth Factor Receptor In Vivo

Simple Summary

Abundance of certain proteins such as epidermal growth factor receptor (EGFR) and their growth factors on cancer cells is in part responsible for their uncontrolled growth. Compounds that selectively bind to such proteins have diagnostic and/or therapeutic implications. EGFR has four binding domains (I-IV). Most anti-EGFR therapeutic antibodies bind to domain III. Compounds that bind to other domains have implications not only for diagnosis but also for monitoring therapy response. We describe the development of a diagnostic agent to be used with positron emission tomography (PET) that binds to domain II of EGFR. We developed ⁸⁹Zr-8709-scFv-Fc antibody PET agent and evaluated its binding characteristics in cancer cells and mouse models. The presence of a domain III-binding antibody such as nimotuzumab did not inhibit the binding of ⁸⁹Zr-8709-scFv-Fc, and vice versa. Therefore, ⁸⁹Zr-8709-scFv-Fc PET/CT can be used for diagnosis and monitoring therapy response in the presence of a domain III-binding agent.

Abstract

Epidermal growth factor receptor I (EGFR) is overexpressed in many cancers. The extracellular domain of EGFR has four binding epitopes (domains I- IV). All clinically approved anti-EGFR antibodies bind to domain III. Imaging agents that bind to domains other than domain III of EGFR are needed for accurate quantification of EGFR, patient selection for anti-EGFR therapeutics and monitoring of response to therapies. We recently developed a domain II-specific antibody fragment 8709. In this study, we have evaluated the in vitro and in vivo properties of ⁸⁹Zr-8709-scFv-Fc (105 kDa). We conjugated 8709-scFv-Fc with the deferoxamine (DFO) chelator and radiolabeled the DFO-8970-scFv with ⁸⁹Zr. We evaluated the binding of ⁸⁹Zr-DFO-8709-scFv-Fc in EGFR positive and negative cell lines DLD-1, MDA-MB-231 and MDA-MB-435, respectively, and in mouse xenograft models. Simultaneously, we have compared the binding of ⁸⁹Zr-8709-scFv-Fc with ¹¹¹In-nimotuzumab, a domain III anti-EGFR antibody. DFO-8709-scFv-Fc displayed similar cell binding specificity as 8709-scFv-Fc. Saturation cell binding assay and immunoreactive fraction showed that radiolabeling did not alter the binding of 8709-scFv-Fc. Biodistribution and microPET showed good uptake of ⁸⁹Zr-8709-scFv-Fc in xenografts after 120 h post injection (p.i). and was domain-specific to EGFR domain II. ⁸⁹Zr-8709-scFv-Fc did not compete for binding in vitro and in vivo with a known domain III binder nimotuzumab. The results show that ⁸⁹Zr-8709-scFv-Fc is specific to domain II of EGFR making it favorable for quantification of EGFR in vivo, hence, patient selection and monitoring of response to treatment with anti-EGFR antibodies.

Nimotuzumab Site-Specifically Labeled with 89Zr and 225Ac Using SpyTag/SpyCatcher for PET Imaging and Alpha Particle Radioimmunotherapy of Epidermal Growth Factor Receptor Positive Cancers

Simple Summary

Monoclonal antibodies (IgG) are excellent probes for targeting cell surface receptors for imaging and therapeutic applications. These theranostic agents are often developed by randomly conjugating radioisotopes/drugs/chelators to the primary amine of lysine or the sulfhydryl groups of cysteine on the antibody. Random conjugation often alters the properties of the antibody. We have site-specifically radiolabeled nimotuzumab an anti-epidermal growth factor receptor (EGFR) monoclonal antibody with 89Zr and 225Ac using SpyTag: ∆N-SpyCatcher for positron emission tomography (PET) imaging and alpha particle radiotherapy, and evaluated these agents in a model of EGFR-positive triple negative breast cancer (TNBC). Nimotuzumab-SpyTag-∆N-SpyCatcher constructs showed improved binding in vitro compared with randomly conjugated constructs. 89Zr-nimotuzumab-SpyTag-∆N-SpyCatcher specifically delineated EGFR-positive xenograft in vivo using microPET/CT imaging. Compared with control treatment groups, 225Ac-nimotuzumab-SpyTag-∆N-SpyCatcher more than doubled the survival of mice bearing EGFR-positive MDA-MB-231 TNBC xenograft. This work highlights a facile method to site-specifically radiolabel antibodies using SpyTag: ∆N-SpyCatcher.

Abstract

To develop imaging and therapeutic agents, antibodies are often conjugated randomly to a chelator/radioisotope or drug using a primary amine (NH₂) of lysine or sulfhydryl (SH) of cysteine. Random conjugation to NH₂ or SH groups can require extreme conditions and may affect target recognition/binding and must therefore be tested. In the present study, nimotuzumab was site-specifically labeled using ∆N-SpyCatcher/SpyTag with different chelators and radiometals. Nimotuzumab is a well-tolerated anti-EGFR antibody with low skin toxicities. First, ΔN-SpyCatcher was reduced using tris(2-carboxyethyl)phosphine (TCEP), which was followed by desferoxamine-maleimide (DFO-mal) conjugation to yield a reactive ΔN-SpyCatcher-DFO. The ΔN-SpyCatcher-DFO was reacted with nimotuzumab-SpyTag to obtain stable nimotuzumab-SpyTag-∆N-SpyCatcher-DFO. Radiolabeling was performed with ⁸⁹Zr, and the conjugate was used for the in vivo microPET imaging of EGFR-positive MDA-MB-468 xenografts. Similarly, ∆N-SpyCatcher was conjugated to an eighteen-membered macrocyclic chelator macropa-maleimide and used to radiolabel nimotuzumab-SpyTag with actinium-225 (²²⁵Ac) for in vivo radiotherapy studies. All constructs were characterized using biolayer interferometry, flow cytometry, radioligand binding assays, HPLC, and bioanalyzer. MicroPET/CT imaging showed a good tumor uptake of ⁸⁹Zr-nimotuzumab-SpyTag-∆N-SpyCatcher with 6.0 ± 0.6%IA/cc (n = 3) at 48 h post injection. The EC₅₀ of ²²⁵Ac-nimotuzumab-SpyTag-∆N-SpyCatcher and ²²⁵Ac-control-IgG-SpyTag-∆N-SpyCatcher against an EGFR-positive cell-line (MDA-MB-468) was 3.7 ± 3.3 Bq/mL (0.04 ± 0.03 nM) and 18.5 ± 4.4 Bq/mL (0.2 ± 0.04 nM), respectively. In mice bearing MDA-MB-468 EGFR-positive xenografts, ²²⁵Ac-nimotuzumab-SpyTag-∆N-SpyCatcher significantly (p = 0.0017) prolonged the survival of mice (64 days) compared to ²²⁵Ac-control IgG (28.5 days), nimotuzumab (28.5 days), or PBS-treated mice (30 days). The results showed that the conjugation and labeling using SpyTag/∆N-SpyCatcher to nimotuzumab did not significantly (p > 0.05) alter the receptor binding of nimotuzumab compared with a non-specific conjugation approach. ²²⁵Ac-nimotuzumab-SpyTag-∆N-SpyCatcher was effective in vitro and in an EGFR-positive triple negative breast cancer xenograft model.

Advances in quantitative immunohistochemistry and their contribution to breast cancer

Introduction: Automated image analysis provides an objective, quantitative, and reproducible method of measurement of biomarkers. Image quantification is particularly well suited for the analysis of tissue microarrays which has played a major pivotal role in the rapid assessment of molecular biomarkers. Data acquired from grinding up bulk tissue samples miss spatial information regarding cellular localization; therefore, methods that allow for spatial cell phenotyping at high resolution have proven to be valuable in many biomarker discovery assays. Here, we focus our attention on breast cancer as an example of a tumor type that has benefited from quantitative biomarker studies using tissue microarray format.Areas covered: The history of immunofluorescence and immunohistochemistry and the current status of these techniques, including multiplexing technologies (spectral and non-spectral) and image analysis software will be addressed. Finally, we will turn our attention to studies that have provided proof-of-principle evidence that have been impacted from the use of these techniques.Expert opinion: Assessment of prognostic and predictive biomarkers on tissue sections and TMA using Quantitative immunohistochemistry is an important advancement in the investigation of biologic markers. The challenges in standardization of quantitative technologies for accurate assessment are required for adoption into routine clinical practice.

A radiopharmaceutical [89Zr]Zr-DFO-nimotuzumab for immunoPET with epidermal growth factor receptor expression in vivo

INTRODUCTION

The potential of the positron-emitting zirconium-89 (⁸⁹Zr) (t_1/2 = 78.4 h) has been recently reported for immune positron emission tomography (immunoPET) radioimmunoconjugates design. In our work, we explored the optimized preparation of [⁸⁹Zr]Zr-DFO-nimotuzumab, and evaluated ⁸⁹Zr-labeled monoclonal antibody (mAb) construct for targeted imaging of epidermal growth factor receptor (EGFR) overexpressed in glioma.

METHODS

To optimize the radiolabeling efficiency of ⁸⁹Zr with DFO-nimotuzumab, multiple immunoconjugates and radiolabeling were performed. Radiolabeling yield, radiochemical purity, stability, and activity assay were investigated to characterize [⁸⁹Zr]Zr-DFO-nimotuzumab for chemical and biological integrity. The in vivo behavior of this tracer was studied in mice bearing subcutaneous U87MG (EGFR-positive) tumors received a 3.5 ± 0.2 MBq/dose using PET/CT imaging. One group mice bearing subcutaneous U87MG (EGFR-positive) tumors received [⁸⁹Zr]Zr-DFO-nimotuzumab (3.5 ± 0.2 MBq, ~3 μg) (nonblocking) for immunoPET; the other group had 30 μg predose (blocking) of cold nimotuzumab 24 h prior to [⁸⁹Zr]Zr-DFO-nimotuzumab.

RESULTS

[⁸⁹Zr]Zr-DFO-nimotuzumab was prepared with high radiochemical yield (>90%), radiochemical purity (>99%), and specific activity (115 ± 0.8 MBq/mg). In vitro validation showed that [⁸⁹Zr]Zr-DFO-nimotuzumab had an initial immunoreactive fraction of 0.99 ± 0.05 and remained active for up to 5 days. A biodistribution study revealed excellent stability of [⁸⁹Zr]Zr-DFO-nimotuzumab in vivo compared with ⁸⁹Zr as a bone seeker. High uptake in the liver and heart and modest penetration in the brain were observed, with no significant accumulation of activity in other organs. ImmunoPET studies also indicated prominent image contrast that remarkably high uptake up to ~20%ID/g for nonblocking and ~2%ID/g for blocking in tumor between 12 and 120 h after administration.

CONCLUSION

These studies developed a radiopharmaceutical [⁸⁹Zr]Zr-DFO-nimotuzumab with optimized synthesis. The potential utility of [⁸⁹Zr]Zr-DFO-nimotuzumab in assessing EGFR status in glioma was demonstrated in this study.

Therapeutic potential of nimotuzumab PEGylated-maytansine antibody drug conjugates against EGFR positive xenograft

Nimotuzumab is a humanized anti-epidermal growth factor receptor I (EGFR) monoclonal antibody. We have developed antibody drug conjugates (ADCs) with nimotuzumab conjugated to PEGylated-maytansine (PEG₆-DM1). We generated conjugates with low (nimotuzumab-PEG₆-DM1-Low: DAR = 3.5) and high (nimotuzumab-PEG₆-DM1-High: DAR = 7.3) drug to antibody ratios (DAR). Quality control was performed using UV spectrophotometry, size exclusion HPLC, bioanalyzer, biolayer interferometry (BLI), and flow cytometry in EGFR-positive DLD-1, MDA-MB-468 (high density EGFR), and HT-29 (very low EGFR density) cells. Control antibody drug conjugates were developed using a human anti-maltose binding protein (MBP) antibody. BLI showed that the binding of nimotuzumab-PEG₆-DM1-Low and nimotuzumab-PEG₆-DM1-High was slightly but significantly affected by conjugation of the drug (nimotuzumab K_D 0.89 ± 0.02 nM < nimotuzumab-PEG₆-DM1-Low K_D 1.94 ± 0.02 nM < nimotuzumab-PEG₆-DM1-High K_D 3.75 ± 0.03 nM). In vitro cytotoxicity was determined following incubation of cells with the immunoconjugates and IC₅₀ values were determined. Nimotuzumab-PEG₆-DM1-Low and nimotuzumab-PEG₆-DM1-High were used to treat EGFR positive KRAS mutant DLD-1 colorectal cancer xenograft. DLD-1 cells were transduced with a red fluorescent protein (iRFP702) to allow the use of near infrared imaging (NIR) for tumor response monitoring. In vitro potency correlated with the number of drugs on antibody, with nimotuzumab-PEG₆-DM1-High showing higher activity than nimotuzumab-PEG₆-DM1-Low. Three doses (15 mg/kg) of the ADCs prolonged the survival of DLD-1-iRFP-702 tumor bearing mice as monitored by NIR. Nimotuzumab-PEG₆-DM1-Low resulted in 4/6 complete cure while nimotuzumab-PEG₆-DM1-High resulted in 2/5 complete cure. The novel ADCs were very effective in a colorectal cancer model in vivo.

Preclinical Evaluation of 111In-Labeled PEGylated Maytansine Nimotuzumab Drug Conjugates in EGFR-Positive Cancer Models

Epidermal growth factor receptor I (EGFR) is overexpressed in most cancers of epithelial origin. Antibody drug conjugates (ADCs) with PEGylated-maytansine (PEG-DM1) show promise in vitro and in vivo. However, in vivo biodistribution data for ADCs with PEG-DM1 have not been reported. Development of methods to understand the real-time in vivo behavior of these ADCs is needed to move these compounds to the clinic. Methods: Here we have used noninvasive small-animal SPECT/CT imaging and ex vivo biodistribution to understand the in vivo behavior of PEG₆-DM1 ADCs. We developed nimotuzumab ADCs conjugated to PEG₆-DM1. We generated immunoconjugates with low (nimotuzumab-PEG₆-DM1-Low) and high (nimotuzumab-PEG₆-DM1-High) drug-to-antibody ratios. The drug-to-antibody of nimotuzumab-PEG₆-DM1-Low and nimotuzumab-PEG₆-DM1-High was 3.5 and 7.3, respectively. Quality control was performed using ultraviolet spectrophotometry, size-exclusion high-performance liquid chromatography, bioanalyzer, biolayer interferometry, and flow cytometry in EGFR-positive DLD-1 cells. These immunoconjugates were conjugated with DOTA and radiolabeled with ¹¹¹In. The in vitro binding and internalization rates of ¹¹¹In-nimotuzumab, ¹¹¹In-nimotuzumab-PEG₆-DM1-Low, and ¹¹¹In-nimotuzumab-PEG₆-DM1-High were characterized. Furthermore, the pharmacokinetics, biodistribution, and imaging characteristics were evaluated in normal and DLD-1 tumor-bearing mice. Results: Flow cytometry and biolayer interferometry showed a trend toward decreasing EGFR affinity with increasing number of PEG₆-DM1 on the antibody. Despite the lower overall cellular binding of the PEG₆-DM1 radioimmunoconjugates, internalization was higher for PEG₆-DM1 ADCs than for the non-PEGylated ADC in the following order: ¹¹¹In-nimotuzumab-PEG₆-DM1-High > ¹¹¹In-nimotuzumab-PEG₆-DM1-Low > ¹¹¹In-nimotuzumab. Nuclear uptake of ¹¹¹In-nimotuzumab-PEG₆-DM1-High was 4.4-fold higher than ¹¹¹In-nimotuzumab. Pharmacokinetics and biodistribution showed that ¹¹¹In-nimotuzumab-PEG₆-DM1-High had the slowest blood and whole-body clearance rate. Uptake in DLD-1 tumors of ¹¹¹In-nimotuzumab was similar to ¹¹¹In-nimotuzumab-PEG₆-DM1-Low but was significantly higher than for ¹¹¹In-nimotuzumab-PEG₆-DM1-High. Tumor-to-background ratios for ¹¹¹In-nimotuzumab and ¹¹¹In-nimotuzumab-PEG₆-DM1-Low were higher than for ¹¹¹In-nimotuzumab-PEG₆-DM1-High. Conclusion: The results show that conjugation of multiple PEG₆-DM1 reduces the affinity for EGFR in vitro. However, the reduced affinity is counteracted by the high internalization rate of constructs with PEG₆-DM1 ADCs in vitro. The decreased affinity resulted in low tumor uptake of ¹¹¹In-nimotuzumab-PEG₆-DM1-High, with a slow overall whole-body clearance rate. These data provide insights for evaluating the pharmacokinetics and normal -tissue toxicity and in determining dosing rate of PEGylated ADCs.

89Zr-nimotuzumab for immunoPET imaging of epidermal growth factor receptor I

Rationale

Epidermal growth factor receptor (EGFR) upregulation is associated with enhanced proliferation and drug resistance in a number of cancers. Nimotuzumab is a humanized monoclonal antibody with high affinity for EGFR. The objective of this study was to determine if ⁸⁹Zr-DFO-nimotuzumab could be suitable for human use as a PET probe for quantifying EGFR in vivo.

Methods

To evaluate the pharmacokinetics, biodistribution, microPET imaging, radiation dosimetry, and normal tissue toxicity in tumor and non-tumor bearing mice of ⁸⁹Zr-desferoxamine-nimotuzumab (⁸⁹Zr-DFO-nimotuzumab) of a product prepared under GMP conditions. Nimotuzumab was conjugated to DFO and radiolabeled with ⁸⁹Zr. ⁸⁹Zr-DFO-nimotuzumab was characterized by in vitro gel-electrophoresis, biolayer interferometry (BLI) and flow cytometry. ⁸⁹Zr-DFO-nimotuzumab was evaluated in vivo by microPET and ex vivo by biodistribution in healthy and EGFR-positive tumor bearing mice.

Results

Flow cytometry with A431 cells showed no significant difference in the dissociation constant of nimotuzumab (13 ± 2 nM) compared with DFO-nimotuzumab (17 ± 4 nM). PET imaging in mice xenografts showed persistently high tumor uptake with the highest uptake obtained in DLD-1 xenograft (18.3 %IA/cc) at 168 hp.i. The projected human effective dose was low and was 0.184 mSv/MBq (0.679 rem/mCi) in females and 0.205 mSv/MBq (0.757 rem/mCi) in males. There was no apparent normal tissue toxicity as shown by cell blood counts and blood biochemistry analyses at 168-fold and 25-fold excess of the projected human radioactive and mass dose of the agent.

Conclusion

⁸⁹Zr-DFO-nimotuzumab had low organ absorbed dose and effective dose that makes it suitable for potential human use.

Near infrared fluorescence imaging of EGFR expression in vivo using IRDye800CW-nimotuzumab

Nimotuzumab is a humanized anti-epidermal growth factor receptor (EGFR) monoclonal antibody that is approved in many countries for the treatment of EGFR-positive cancers. Near infrared (NIR) fluorescent dye-labeled antibodies represent an attractive class of image-guided surgical probes because of their high specificity, tumor uptake, and low dissociation from tumor cells that express the antigen. In this study, we developed a NIR fluorescent dye-labeled nimotuzumab immunoconjugate, IRDye800CW-nimotuzumab, and evaluated in vitro binding with EGFR-positive cells, in vivo tumor uptake by NIR fluorescent imaging, and ex vivo biodistribution. There was no difference in binding between nimotuzumab and IRDye800CW-nimotuzumab to EGFR-positive cells. In mice bearing EGFR-positive xenografts, IRDye800CW-nimotuzumab uptake peaked at 4 days post injection and slowly decreased thereafter with high levels of accumulation still observed at 28 days post injection. In EGFR-positive xenografts, IRDye800CW-nimotuzumab showed more than 2-fold higher uptake in tumors compared to IRDye800CW-cetuximab. In addition, liver uptake of IRDye800CW-nimotuzumab was two-fold lower than cetuximab. The lower liver uptake of IRDye800CW-nimotuzumab could have implications on the selected dose for clinical trials of the immunoconjugate. In summary, this study shows that nimotuzumab is a good candidate for NIR fluorescent imaging and image-guided surgery.

The unique transcriptional response produced by concurrent estrogen and progesterone treatment in breast cancer cells results in upregulation of growth factor pathways and switching from a Luminal A to a Basal-like subtype

BACKGROUND

In breast cancer, progesterone receptor (PR) positivity or abundance is positively associated with survival and treatment response. It was initially believed that PR was a useful diagnostic marker of estrogen receptor activity, but increasingly PR has been recognised to play an important biological role in breast homeostasis, carcinogenesis and metastasis. Although PR expression is almost exclusively observed in estrogen receptor positive tumors, few studies have investigated the cellular mechanisms of PR action in the context of ongoing estrogen signalling.

METHODS

In this study, we contrast PR function in estrogen pretreated ZR-75-1 breast cancer cells with vehicle treated ZR-75-1 and T-47D breast cancer cells using expression microarrays and chromatin immunoprecipitation-sequencing.

RESULTS

Estrogen cotreatment caused a dramatic increase in the number of genes regulated by progesterone in ZR-75-1 cells. In T-47D cells that have naturally high levels of PR, estrogen and progesterone cotreatment resulted in a reduction in the number of regulated genes in comparison to treatment with either hormone alone. At a genome level, estrogen pretreatment of ZR-75-1 cells led to a 10-fold increase in the number of PR DNA binding sites detected using ChIP-sequencing. Time course assessment of progesterone regulated genes in the context of estrogen pretreatment highlighted a series of important regulatory pathways, including those driven by epithelial growth factor receptor (EGFR). Importantly, progesterone applied to cells pretreated with estradiol resulted in switching of the PAM50-determined intrinsic breast cancer subtype from Luminal A to Basal-like, and increased the Oncotype DX® Unscaled Recurrence Score.

CONCLUSION

Estrogen pretreatment of breast cancer cells increases PR steady state levels, resulting in an unequivocal progesterone response that upregulates key members of growth factor pathways. The transformative changes progesterone exerts on the breast cancer subtype suggest that these subtyping tools should be used with caution in premenopausal women.

Novel approaches for quantifying protein biomarkers in gliomas: benefits and pitfalls

The therapeutic paradigm of gliomas is changing from a general approach towards an individualized and targeted approach. Accordingly, the search for prognostic and predictive biomarkers, as well as the demand for quantitative, feasible and robust methods for biomarker analysis increases. We find that software classifiers can identify and quantify the expression of a given biomarker within different subcellular compartments and that such classifiers can exclude frequently occurring nontumor cells, thereby avoiding potential bias. The use of a quantitative approach provides a continuous measurement of the expression, allowing establishment of new cut-points and identification of patients with specific prognoses. However, some pitfalls must be noted. This article focuses on benefits and pitfalls of novel approaches for quantifying protein biomarkers in gliomas.

Identifying and targeting tumor-initiating cells in the treatment of breast cancer

Breast cancer is the most common cancer in women (excluding skin cancer), and it is the second leading cause of cancer-related deaths. Although conventional and targeted therapies have improved survival rates, there are still considerable challenges in treating breast cancer, including treatment resistance, disease recurrence, and metastasis. Treatment resistance can be either de novo - because of traits that tumor cells possess before treatment - or acquired - because of traits that tumor cells gain in response to treatment. A recently proposed mechanism of de novo resistance invokes the existence of a specialized subset of cancer cells defined as tumor-initiating cells (TICs), or cancer stem cells (CSCs). TICs have the capacity to self-renew and to generate new tumors that consist entirely of clonally derived cell types present in the parental tumor. There are data to suggest that TICs are resistant to many conventional cancer therapies and that they can survive treatment in spite of dramatic shrinkage of the tumor. Residual TICs can then eventually regrow, which results in disease relapse. It has also been hypothesized that TIC may be responsible for metastatic disease. If these hypotheses are correct, targeting TICs may be imperative for achieving a cure. In the present review, we discuss evidence for breast TICs and their apparent resistance to conventional chemotherapy and radiotherapy as well as to various targeted therapies. We also address the potential impact of breast TIC plasticity and metastatic potential on therapeutic strategies. Finally, we describe several genes and signaling pathways that appear to be important for TIC function and may represent promising therapeutic targets.

The kinome associated with estrogen receptor-positive status in human breast cancer

Estrogen receptor alpha (ERα) regulates and is regulated by kinases involved in several functions associated with the hallmarks of cancer. The following literature review strongly suggests that distinct kinomes exist for ERα-positive and -negative human breast cancers. Importantly, consistent with the known heterogeneity of ERα-positive cancers, different subgroups exist, which can be defined by different kinome signatures, which in turn are correlated with clinical outcome. Strong evidence supports the interplay of kinase networks, suggesting that targeting a single node may not be sufficient to inhibit the network. Therefore, identifying the important hubs/nodes associated with each clinically relevant kinome in ER+ tumors could offer the ability to implement the best therapy options at diagnosis, either endocrine therapy alone or together with other targeted therapies, for improved overall outcome.

Preparation and Evaluation of (99m)Tc-Epidermal Growth Factor Receptor (EGFR)-Peptide Nucleic Acid for Visualization of EGFR Messenger RNA Expression in Malignant Tumors

Epidermal growth factor receptor (EGFR) is overexpressed in many carcinomas and remains a prime target for diagnostic and therapeutic applications. There is a need to develop noninvasive methods to identify the subset of patients that is most likely to benefit from EGFR-targeted treatment. Noninvasive imaging of EGFR messenger RNA (mRNA) expression may be a useful approach. The aim of this study was to develop a method for preparation of single-photon-emitting probes, (99m)Tc-labeled EGFR mRNA antisense peptide nucleic acid (PNA) ((99m)Tc-EGFR-PNA), and nontargeting control ((99m)Tc-CTL-PNA) and to evaluate their feasibility for imaging EGFR mRNA overexpression in malignant tumors in vivo.

METHODS

On the 5' terminus of synthesized single-stranded 17-mer antisense EGFR mRNA antisense PNA and mismatched PNA, a 4-amino-acid (Gly-(D)-Ala-Gly-Gly) linker forming an N4 structure was used for coupling (99m)Tc. Probes were labeled with (99m)Tc by ligand exchange. The radiochemical purity of these (99m)Tc-labeled probes was determined by reversed-phase high-performance liquid chromatography. Cellular uptake, retention, binding specificity, and stability of the probes were studied either in vitro or in vivo. Biodistribution and radionuclide imaging were performed in BALB/c nude mice bearing SKOV3 (EGFR-positive) or MDA-MB-435S (EGFR-negative) carcinoma xenografts, respectively.

RESULTS

The average labeling efficiencies of (99m)Tc-EGFR-PNA and (99m)Tc-CTL-PNA were 98.80% ± 1.14% and 98.63% ± 1.36% (mean ± SD, n = 6), respectively, within 6 h at room temperature, and the radiochemical purity of the probes was higher than 95%. (99m)Tc-EGFR-PNA was highly stable in normal saline and fresh human serum at 37°C in vitro and in urine and plasma samples of nude mice after 2-3 h of injection. Cellular uptake and retention ratios of (99m)Tc-EGFR-PNA in SKOV3 cells were higher than those of (99m)Tc-CTL-PNA and the EGFR-negative control. Meanwhile, EGFR mRNA binding (99m)Tc-EGFR-PNA was blocked with an excess of unlabeled EGFR-PNA in SKOV3 cell lines. The biodistribution study demonstrated accumulation of (99m)Tc-EGFR-PNA primarily in the SKOV3 xenografts and in EGFR-expressing organs. Radionuclide imaging demonstrated clear localization of (99m)Tc-EGFR-PNA in the SKOV3 xenografts shortly after injection but not in (99m)Tc-CTL-PNA and the EGFR-negative control.

CONCLUSION

(99m)Tc-EGFR-PNA has the potential for imaging EGFR mRNA overexpression in tumors.

Prognostic value of Musashi-1 in gliomas

The aim of this study was to investigate the prognostic value of the RNA-binding protein Musashi-1 in adult patients with primary gliomas. Musashi-1 has been suggested to be a cancer stem cell-related marker in gliomas, and high levels of Musashi-1 have been associated with high tumor grades and hence poor prognosis. Samples of 241 gliomas diagnosed between 2005 and 2009 were stained with an anti-Musashi-1 antibody using a fluorescent staining protocol followed by automated image acquisition and processing. Musashi-1 area fraction and intensity in cytoplasm and in nuclei were quantified by systematic random sampling in 2 % of the vital tumor area. In WHO grade III tumors high levels of Musashi-1 were associated with poor survival in multivariate analysis (HR 3.39, p = 0.02). We identified a sub-population of glioblastoma (GBM) patients with high levels of Musashi-1 and a superior prognosis (HR 0.65, p = 0.038). In addition patients with high levels of Musashi-1 benefitted most from post-surgical treatment, indicating that Musashi-1 may be a predictive marker in GBMs. In conclusion, our results suggest that high levels of Musashi-1 are associated with poor survival in patients with WHO grade III tumors and that Musashi-1 may be a predictive marker in GBMs, although further validation is needed. We find the combination of immunofluorescence and automated quantitation to be a feasible, robust, and reproducible approach for quantitative biomarker studies.

Cross-talk between GPER and growth factor signaling

G protein-coupled receptors (GPCRs) and growth factor receptors mediate multiple physio-pathological responses to a diverse array of extracellular stimuli. In this regard, it has been largely demonstrated that GPCRs and growth factor receptors generate a multifaceted signaling network, which triggers relevant biological effects in normal and cancer cells. For instance, some GPCRs transactivate the epidermal growth factor receptor (EGFR), which stimulates diverse transduction pathways leading to gene expression changes, cell migration, survival and proliferation. Moreover, it has been reported that a functional interaction between growth factor receptors and steroid hormones like estrogens is involved in the growth of many types of tumors as well as in the resistance to endocrine therapy. This review highlights recent findings on the cross-talk between a member of the GPCR family, the G protein-coupled estrogen receptor 1 (GPER, formerly known as GPR30) and two main growth factor receptors like EGFR and insulin-like growth factor-I receptor (IGF-IR). The biological implications of the functional interaction between these important mediators of cell responses particularly in cancer are discussed. This article is part of a Special Issue entitled 'CSR 2013'.

Can predictive biomarkers in breast cancer guide adjuvant endocrine therapy?

Personalized medicine for oestrogen receptor-α (ERα)-positive breast cancer requires predictive biomarkers for broad endocrine resistance as well as biomarkers capable of predicting resistance to a specific agent. In addition, biomarkers could be used to select patients that might benefit from the addition of treatments that do not target ERα. However, biomarker identification studies seem to be far from consistent and identified biomarkers seldom face an introduction into clinical practice. Importantly, most of the studies that seek to identify biomarkers have been performed using material from consecutive series of patients treated with tamoxifen (the most commonly prescribed ERα antagonist). Consequently, the predictive value of any biomarker identified is confounded by its prognostic value. Another important issue is the lack of differentiation between premenopausal and postmenopausal patients with breast cancer. The hormonal environment of a tumour in patients who are premenopausal is intrinsically distinct from those arising in postmenopausal women. Biomarkers of different biological mechanisms might enable the prediction of either broad endocrine resistance or resistance to a specific agent in each of these patient subtypes. Ultimately, improvements to study design are needed to establish the clinical validity of the most promising biomarkers to predict benefit from endocrine therapy.

Breast cancer stem cells and their role in resistance to endocrine therapy

Developmentally, tumours can be viewed as aberrant versions of normal tissues. For example, tumours often retain differentiation markers of their tissue of origin. In addition, there is evidence that they contain cancer stem-like cells (CSCs) that drive tumourigenesis. In this review, we summarise current evidence that breast CSCs may partially explain endocrine resistance in breast cancer. In normal breast, the stem cells are known to possess a basal phenotype and to be mainly oestrogen receptor-α-negative (ER-). If the hierarchy in breast cancer reflects this, the breast CSC may be endocrine resistant because it expresses very little ER and can only respond to treatment by virtue of paracrine signalling from neighbouring, differentiated ER+ tumour cells. Normal breast epithelial stem cells are regulated by the epidermal growth factor receptor and other growth factor receptor signals. The observed increase in growth factor receptor expression in endocrine-resistant breast cancers may reflect a bigger proportion of CSCs selected by endocrine therapies. There is evidence from a number of studies that breast CSCs are ER- and EGR+/HER2+, which would support this view. It is reported that CSCs express mesenchymal genes, which are suppressed by ER expression, further indicating the mutual exclusion between ER+ cells and the CSCs. As we learn more about CSCs, differentiation and the expression and functional activity of the ER in these cells in diverse breast tumour sub-types, it is hoped that our understanding will lead to new modalities to overcome the problem of endocrine resistance in the clinic.

Clinical utility of the combination of lapatinib and letrozole in the management of hormone receptor-positive and HER2-positive advanced breast cancer

Breast cancers that overexpress human epidermal growth factor receptor-2 (HER2-positive [HER2+]) tend to be biologically aggressive and associated with a poor prognosis, even those that coexpress receptors for estrogen and/or progesterone (hormone receptor-positive [HR+]). Optimal therapy for patients with "double-positive" (HR+/HER2+) breast cancers is still being defined. In this subset of patients, the efficacy of targeted endocrine therapies appears to be diminished by cross-activation or "crosstalk" between estrogen receptor-mediated gene transcription and pathways activated by other growth factor receptors, including HER2. Lapatinib is a tyrosine kinase inhibitor which binds reversibly to the intracellular domains of the epidermal growth factor receptor and HER2, interfering with their ability to initiate signal transduction cascades that promote cancer cell proliferation, survival, and metastasis. In a recently published randomized, placebo-controlled Phase III study in postmenopausal HR+ metastatic breast cancer, the addition of lapatinib to the aromatase inhibitor letrozole significantly improved progression-free survival solely in women who were also HER2+. This article reviews the biology of "double-positive" breast cancers and the rationale underlying combining endocrine and HER2-targeted therapies, including the lapatinib/letrozole combination, for these tumors. Results from the Phase III trial are examined, as well as available data on other combinations of HR and HER2-targeted therapies. Ongoing trials and potential future applications of these combinations in both HR+/HER2+ and other subgroups of breast cancer patients are also discussed.

Cytoplasmic estrogen receptor in breast cancer

PURPOSE

In addition to genomic signaling, it is accepted that estrogen receptor-α (ERα) has nonnuclear signaling functions, which correlate with tamoxifen resistance in preclinical models. However, evidence for cytoplasmic ER localization in human breast tumors is less established. We sought to determine the presence and implications of nonnuclear ER in clinical specimens.

EXPERIMENTAL DESIGN

A panel of ERα-specific antibodies (SP1, MC20, F10, 60c, and 1D5) was validated by Western blot and quantitative immunofluorescent (QIF) analysis of cell lines and patient controls. Then eight retrospective cohorts collected on tissue microarrays were assessed for cytoplasmic ER. Four cohorts were from Yale (YTMA 49, 107, 130, and 128) and four others (NCI YTMA 99, South Swedish Breast Cancer Group SBII, NSABP B14, and a Vietnamese Cohort) from other sites around the world.

RESULTS

Four of the antibodies specifically recognized ER by Western and QIF analysis, showed linear increases in amounts of ER in cell line series with progressively increasing ER, and the antibodies were reproducible on YTMA 49 with Pearson correlations (r(2) values) ranging from 0.87 to 0.94. One antibody with striking cytoplasmic staining (MC20) failed validation. We found evidence for specific cytoplasmic staining with the other four antibodies across eight cohorts. The average incidence was 1.5%, ranging from 0 to 3.2%.

CONCLUSIONS

Our data show ERα is present in the cytoplasm in a number of cases using multiple antibodies while reinforcing the importance of antibody validation. In nearly 3,200 cases, cytoplasmic ER is present at very low incidence, suggesting its measurement is unlikely to be of routine clinical value.

Clinical perspectives on the role of the human papillomavirus vaccine in the prevention of cancer

The role of human papillomavirus (HPV) in the genesis of cervical cancer has been well documented, and an increasing body of literature exists with regard to the role of HPV in other cancers, including cancers of the head and neck. With the recent expansion of the United States Food and Drug Administration's approval of the quadrivalent HPV virus-like particle vaccine to include men and boys and approval of the bivalent vaccine this year, the controversies regarding who should be vaccinated, at what age is vaccination most appropriate, and the limitations of the available HPV vaccines are increasing. Health care providers are challenged with evaluating the current, but continually changing, clinical evidence when making critical decisions for their patients. A literature search of MEDLINE and SciVerse Scopus was conducted for articles published from 1998-April 2010 regarding HPV, HPV-related cancers, and HPV vaccines. Although both HPV vaccines were greater than 90% effective in the prevention of cervical cancer precursors in an according-to-protocol cohort, both vaccines were significantly less effective in the intent-to-treat population. In patients who achieved seroconversion, the geometric mean titers decrease dramatically within the first 2 years after vaccination, and then continue to decline at a slower rate. No effective antibody titer has been defined for either vaccine, and no studies have been conducted with documented HPV exposure after vaccination. With low efficacy rates in an intent-to-treat population and the potential for waning immunity, it is imperative for women to continue to receive regular Pap tests and gynecologic examinations. Although vaccine administration was shown to be cost-effective when administered to adolescent girls, many of these simulations overestimated the durability of protection, efficacy rates in sexually active women, impact of incomplete vaccination, or necessity of boosters in the future. Whereas the introduction of the HPV vaccine was an enormous advancement in the cancer prevention research arena, optimization of its clinical use is still needed.

The Role of Proteomics in the Diagnosis and Treatment of Women's Cancers: Current Trends in Technology and Future Opportunities

Technological and scientific innovations over the last decade have greatly contributed to improved diagnostics, predictive models, and prognosis among cancers affecting women. In fact, an explosion of information in these areas has almost assured future generations that outcomes in cancer will continue to improve. Herein we discuss the current status of breast, cervical, and ovarian cancers as it relates to screening, disease diagnosis, and treatment options. Among the differences in these cancers, it is striking that breast cancer has multiple predictive tests based upon tumor biomarkers and sophisticated, individualized options for prescription therapeutics while ovarian cancer lacks these tools. In addition, cervical cancer leads the way in innovative, cancer-preventative vaccines and multiple screening options to prevent disease progression. For each of these malignancies, emerging proteomic technologies based upon mass spectrometry, stable isotope labeling with amino acids, high-throughput ELISA, tissue or protein microarray techniques, and click chemistry in the pursuit of activity-based profiling can pioneer the next generation of discovery. We will discuss six of the latest techniques to understand proteomics in cancer and highlight research utilizing these techniques with the goal of improvement in the management of women's cancers.

Standardization of estrogen receptor measurement in breast cancer suggests false-negative results are a function of threshold intensity rather than percentage of positive cells

PURPOSE

Recent misclassification (false negative) incidents have raised awareness concerning limitations of immunohistochemistry (IHC) in assessment of estrogen receptor (ER) in breast cancer. Here we define a new method for standardization of ER measurement and then examine both change in percentage and threshold of intensity (immunoreactivity) to assess sources for test discordance.

METHODS

An assay was developed to quantify ER by using a control tissue microarray (TMA) and a series of cell lines in which ER immunoreactivity was analyzed by quantitative immunoblotting in parallel with the automated quantitative analysis (AQUA) method of quantitative immunofluorescence (QIF). The assay was used to assess the ER protein expression threshold in two independent retrospective cohorts from Yale and was compared with traditional methods.

RESULTS

Two methods of analysis showed that change in percentage of positive cells from 10% to 1% did not significantly affect the overall number of ER-positive patients. The standardized assay for ER on two Yale TMA cohorts showed that 67.9% and 82.5% of the patients were above the 2-pg/μg immunoreactivity threshold. We found 9.1% and 19.7% of the patients to be QIF-positive/IHC-negative, and 4.0% and 0.4% to be QIF-negative/IHC-positive for a total of 13.1% and 20.1% discrepant cases when compared with pathologists' judgment of threshold. Assessment of survival for both cohorts showed that patients who were QIF-positive/pathologist-negative had outcomes similar to those of patients who had positive results for both assays.

CONCLUSION

Assessment of intensity threshold by using a quantitative, standardized assay on two independent cohorts suggests discordance in the 10% to 20% range with current IHC methods, in which patients with discrepant results have prognostic outcomes similar to ER-positive patients with concordant results.

PRO_10--a new tissue-based prognostic multigene marker in patients with early estrogen receptor-positive breast cancer

BACKGROUND/AIMS

Clinicopathological and molecular factors determine the prognosis of breast cancer. PRO_10 is a prognostic score based on quantitative RT-PCR of 10 proliferation-associated genes obtained from formalin-fixed, paraffin-embedded breast cancer tissues. We revalidated PRO_10 in patients treated in a non-trial setting.

METHODS

The charts of 315 patients with postmenopausal estrogen receptor (ER)-positive breast cancer between 1996 and 2004 were reviewed. Forty-eight cases relapsed within 5 years of diagnosis; they were paired with controls by matching the N and T stage, histological grade, percent ER-positive cells, human epidermal growth factor receptor 2, age, adjuvant chemo- and endocrine therapy. The score was tested by conditional logistic regression.

RESULTS

Despite strict matching, PRO_10 remained prognostic for recurrence in the whole group (odds ratio, OR = 4.7, p = 0.005) and in subgroups of grade 2 (OR = 5.5, p = 0.009) and N0 cancers (OR = 15, p = 0.002). Five-year recurrence-free survival was 29% in patients with high and 67% in patients with low scores (p = 0.002). PRO_10 was prognostic for overall survival (5-year overall survival 71 vs. 91%).

CONCLUSION

PRO_10 is an independent prognostic marker in postmenopausal ER-positive breast cancer. It is based on formalin-fixed, paraffin-embedded tissue and could be integrated easily into the routine diagnostic workflow.

G-protein-coupled estrogen receptor GPR30 and tamoxifen resistance in breast cancer

Recently, we have shown that the new G-protein-coupled estrogen receptor GPR30 plays an important role in the development of tamoxifen resistance in vitro. This study was undertaken to evaluate the correlation between GPR30 and tamoxifen resistance in breast cancer patients. GPR30 protein expression was evaluated by immunohistochemical analysis in 323 patients with primary operable breast cancer. The association between GPR30 expression and tamoxifen resistance was confirmed in a second cohort of 103 patients treated only with tamoxifen. Additionally, we evaluated GPR30 expression in 33 primary tumors and in recurrent tumors from the same patients. GPR30 expression was detected in 56.7% of the breast cancer specimens investigated and it correlated with overexpression of HER-2 (P = 0.021), EGFR (P = 0.024) and lymph node status (P = 0.047). In a first cohort, survival analysis showed that GPR30 was negatively correlated with relapse-free survival (RFS) only in patients treated with tamoxifen (tamoxifen with or without chemotherapy). GPR30 expression was associated with shorter RFS (HR = 1.768; 95% CI, 1.156-2.703; P = 0.009). In a subset of patients treated only with tamoxifen, multivariate analysis revealed that GPR30 expression is an independent unfavorable factor for RFS (HR = 4.440; 95% CI, 1.408-13.997; P = 0.011). In contrast, GPR30 tended to be a favorable factor regarding RFS in patients who did not receive tamoxifen. In 33 paired biopsies obtained before and after adjuvant therapy, GPR30 expression significantly increased only under tamoxifen treatment (P = 0.001). GPR30 expression in breast cancer independently predicts a poor RFS in patients treated with tamoxifen.

Loss of nuclear localized and tyrosine phosphorylated Stat5 in breast cancer predicts poor clinical outcome and increased risk of antiestrogen therapy failure

PURPOSE

To investigate nuclear localized and tyrosine phosphorylated Stat5 (Nuc-pYStat5) as a marker of prognosis in node-negative breast cancer and as a predictor of response to antiestrogen therapy.

PATIENTS AND METHODS

Levels of Nuc-pYStat5 were analyzed in five archival cohorts of breast cancer by traditional diaminobenzidine-chromogen immunostaining and pathologist scoring of whole tissue sections or by immunofluorescence and automated quantitative analysis (AQUA) of tissue microarrays.

RESULTS

Nuc-pYStat5 was an independent prognostic marker as measured by cancer-specific survival (CSS) in patients with node-negative breast cancer who did not receive systemic adjuvant therapy, when adjusted for common pathology parameters in multivariate analyses both by standard chromogen detection with pathologist scoring of whole tissue sections (cohort I; n = 233) and quantitative immunofluorescence of a tissue microarray (cohort II; n = 291). Two distinct monoclonal antibodies gave concordant results. A progression array (cohort III; n = 180) revealed frequent loss of Nuc-pYStat5 in invasive carcinoma compared to normal breast epithelia or ductal carcinoma in situ, and general loss of Nuc-pYStat5 in lymph node metastases. In cohort IV (n = 221), loss of Nuc-pYStat5 was associated with increased risk of antiestrogen therapy failure as measured by univariate CSS and time to recurrence (TTR). More sensitive AQUA quantification of Nuc-pYStat5 in antiestrogen-treated patients (cohort V; n = 97) identified by multivariate analysis patients with low Nuc-pYStat5 at elevated risk for therapy failure (CSS hazard ratio [HR], 21.55; 95% CI, 5.61 to 82.77; P < .001; TTR HR, 7.30; 95% CI, 2.34 to 22.78; P = .001). CONCLUSION Nuc-pYStat5 is an independent prognostic marker in node-negative breast cancer. If confirmed in prospective studies, Nuc-pYStat5 may become a useful predictive marker of response to adjuvant hormone therapy.

Analysis of protein biomarkers in human clinical tumor samples: critical aspects to success from tissue acquisition to analysis

There has been increased interest in the analysis of protein biomarkers in clinical tumor tissues in recent years. Tissue-based biomarker assays can add value and aid decision-making at all stages of drug development, as well as being developed for use as predictive biomarkers and for patient stratification and prognostication in the clinic. However, there must be an awareness of the legal and ethical issues related to the sourcing of human tissue samples. This article also discusses the limits of scope and critical aspects on the successful use of the following tissue-based methods: immunohistochemistry, tissue microarrays and automated image analysis. Future advances in standardization of tissue biobanking methods, immunohistochemistry and quantitative image analysis techniques are also discussed.

Antibody-based proteomics: fast-tracking molecular diagnostics in oncology

The effective implementation of personalized cancer therapeutic regimens depends on the successful identification and translation of informative biomarkers to aid clinical decision making. Antibody-based proteomics occupies a pivotal space in the cancer biomarker discovery and validation pipeline, facilitating the high-throughput evaluation of candidate markers. Although the clinical utility of these emerging technologies remains to be established, the traditional use of antibodies as affinity reagents in clinical diagnostic and predictive assays suggests that the rapid translation of such approaches is an achievable goal. Furthermore, in combination with, or as alternatives to, genomic and transcriptomic methods for patient stratification, antibody-based proteomics approaches offer the promise of additional insight into cancer disease states. In this Review, we discuss the current status of antibody-based proteomics and its contribution to the development of new assays that are crucial for the realization of individualized cancer therapy.

Use of molecular markers for predicting therapy response in cancer patients

Predictive markers are factors that are associated with upfront response or resistance to a particular therapy. Predictive markers are important in oncology as tumors of the same tissue of origin vary widely in their response to most available systemic therapies. Currently recommended oncological predictive markers include both estrogen and progesterone receptors for identifying patients with breast cancers likely to benefit from hormone therapy, HER-2 for the identification of breast cancer patients likely to benefit from trastuzumab, specific K-RAS mutations for the identification of patients with advanced colorectal cancer unlikely to benefit from either cetuximab or panitumumab and specific EGFR mutations for selecting patients with advanced non-small-cell lung cancer for treatment with tyrosine kinase inhibitors such as gefitinib and erlotinib. The availability of predictive markers should increase drug efficacy and decrease toxicity, thus leading to a more personalized approach to cancer treatment.

Preventing cervical cancer in the Latina population

Cervical cancer causes great morbidity and mortality worldwide and in the United States. Infection with oncogenic human papillomavirus (HPV), the etiological agent of almost all cervical cancer cases, is common among sexually active women in the United States. Over the past 5 decades, the implementation of Papanicolaou screening programs in the United States has led to a significant decrease in cervical cancer cases. However, notable disparities in the incidence and mortality of cervical cancer and cervical screening rates among Hispanics in the United States remain. If current disparities persist without intervention, the Latina population in the United States may remain at a higher risk of developing and dying from cervical cancer. We discuss disparities in cervical cancer screening, incidence, and mortality among the Latina population, as well as the barriers that may propagate these disparities. We also address how these barriers can be overcome through the coordination of outreach programs and widespread prophylactic HPV vaccination to reduce cervical cancer disparities in Latinas.

Analytic variability in immunohistochemistry biomarker studies

BACKGROUND

Despite the widespread use of immunohistochemistry (IHC), there are no standardization guidelines that control for antibody probe variability. Here we describe the effect of variable antibody reagents in the assessment of cancer-related biomarkers by IHC.

METHODS

Estrogen receptor (ER), epidermal growth factor receptor (EGFR) 1, and human epidermal growth factor receptor 3 (HER3) were evaluated by quantitative immunofluorescence. Correlations between ER clones 1D5, SP1, F10, and ER60c, and EGFR monoclonal 31G7, 2-18C9, H11, and 15F8, and polyclonal 2232 antibodies were assessed in 642 breast cancer patients. HER3 was measured by RTJ1, RTJ2, SGP1, M7297, RB-9211, and C-17 antibodies in 42 lung cancer patients. Survival analysis was done with the use of multiple cutoff points to reveal any prognostic classification.

RESULTS

All ER antibodies were tightly correlated (Pearson's r(2) = 0.94-0.96; P < 0.0001) and western blotting confirmed their specificity in MCF-7 and BT474 cells. All EGFR antibodies but 2232 yielded specific results in western blotting; however, only 31G7 and 2-18C9 were strongly associated (Pearson's r(2) = 0.61; P < 0.0001). HER3 staining was nonspecific and nonreproducible. High EGFR-expressing patients had a worse prognosis when EGFR was measured with H11 or 31G7 (log rank P = 0.015 and P = 0.06). There was no statistically significant correlation between survival and EGFR detected by 2-18C9, 15F8, or polyclonal 2232 antibodies.

CONCLUSIONS

Antibody validation is a critical analytic factor that regulates IHC readings in biomarker studies. Evaluation of IHC proficiency and quality control are key components toward IHC standardization.

IMPACT

This work highlights the importance of IHC standardization and could result in the improvement of clinically relevant IHC protocols.

Epidermal growth factor receptor expression in breast cancer association with biologic phenotype and clinical outcomes

BACKGROUND

Epidermal growth factor receptor (EGFR) expression is associated with aggressive phenotypes in preclinical breast cancer models, but in clinical studies, EGFR has been inconsistently linked to poor outcome. We hypothesized that EGFR expression in human breast tumors, when centrally and uniformly assessed, is associated with an aggressive phenotype and resistance to systemic therapy.

METHODS

In a database of 47,286 patients with breast cancer, EGFR status was known on 2567 tumors. EGFR levels were measured centrally by ligand binding assay, and tumors with > or =10 fmol/mg were prospectively deemed positive. Clinical and biological features of EGFR-positive and EGFR-negative tumors were compared. Clinical outcomes were assessed by systemic therapy status.

RESULTS

Of 2567 tumors, 475 (18%) were EGFR positive. EGFR-positive tumors were more common in younger and in black women, were larger, had a higher S-phase fraction, and were more likely to be aneuploid. EGFR-positive tumors were more likely to be HER2-positive (26% vs 16%, P < .0001), but less likely to be estrogen receptor-positive (60% vs 88%, P < .0001) or progesterone receptor-positive (26% vs 65%, P < .0001). In multivariate analyses, EGFR expression independently correlated with worse disease-free survival (hazard ratio [HR] = 1.66; 95% confidence interval [CI], 1.4-2.41, P = .007) and overall survival (HR = 1.98, 95% CI, 1.36-2.88, P = .0004) in treated patients, but not in untreated patients.

CONCLUSIONS

EGFR expression is more common in breast tumors in younger and black women. It is associated with lower hormone receptor levels, higher proliferation, genomic instability, and HER2 overexpression. It is correlated with higher risk of relapse in patients receiving adjuvant treatment. Blocking EGFR may improve outcome in selected patients.

Endocrine resistance associated with activated ErbB system in breast cancer cells is reversed by inhibiting MAPK or PI3K/Akt signaling pathways

Endocrine therapy resistance is one of the main challenges in the treatment of estrogen receptor positive (ER+) breast cancer patients. This study showed that two ER+ human breast carcinoma cell lines derived from MCF-7 (MVLN cells) that have acquired under OH-Tamoxifen selection two distinct phenotypes of endocrine resistance both displayed constitutive activation of the PI3K/Akt and MAPK pathways. Aberrant expression and activation of the ErbB system (phospho-EGFR, phospho-ErbB2, phospho-ErbB3, over-expression of ErbB4 and over-expression of several ErbB ligands) were also observed in the two resistant cell lines, suggesting the existence of an autocrine loop leading to constitutive activation of MAPK and PI3K/Akt survival pathways. The recent clinical use of specific signal transduction inhibitors is one of the most promising therapeutic approaches in breast cancers. The MEK inhibitor PD98059 and the PI3K inhibitor LY294002 were both able to enhance the cytostatic effect of OH-Tamoxifen or fulvestrant on MVLN sensitive cells. In the two resistant cell lines, inhibition of the MAPK or the PI3K/Akt pathways associated with endocrine therapy was sufficient to reverse OH-Tamoxifen or fulvestrant resistance. Investigating the effect of a combination of both inhibitors on the reversion of OH-Tamoxifen and fulvestrant resistance in the two resistant cell lines suggested that, in clinical practice, a strategy combining the two inhibitors would be the best approach to target the different endocrine resistance phenotypes possibly present in a tumor. In conclusion, the combination of MAPK and PI3K inhibitors represents a promising strategy to overcome endocrine therapy resistance in ER+ breast cancer patients.

Automated analysis of tissue microarrays

The analysis of protein expression in tissue by immunohistochemistry (IHC) presents three significant challenges. They are (1) the time-consuming nature of pathologist-based scoring of slides; (2) the need for objective quantification and localization of protein expression; and (3) the need for a highly reproducible measurement to limit intra- and inter-observer variability. While there are a variety of commercially available platforms for automated chromagen-based and fluorescence-based image acquisition of tissue microarrays, this chapter is focused on the analysis of fluorescent images by AQUA(R) analysis (Automated QUantitative Analysis) and the solutions offered by such a method for research and diagnostics. AQUA analysis is a method for molecularly defining regions of interest or "compartments" within a tissue section. The methodology can be utilized with tissue microarrays to provide rapid, quantitative, localized, and reproducible protein expression data that can then be used to identify statistically relevant correlations in populations. Ultimately this allows for a multiplexed, objective and standardized quantitative approach for biomarker research and diagnostic assay development for protein expression in tissue.

Imaging of EGFR expression in murine xenografts using site-specifically labelled anti-EGFR 111In-DOTA-Z EGFR:2377 Affibody molecule: aspect of the injected tracer amount

INTRODUCTION

Overexpression of epidermal growth factor receptor (EGFR) is a prognostic and predictive biomarker in a number of malignant tumours. Radionuclide molecular imaging of EGFR expression in cancer could influence patient management. However, EGFR expression in normal tissues might complicate in vivo imaging. The aim of this study was to evaluate if optimization of the injected protein dose might improve imaging of EGFR expression in tumours using a novel EGFR-targeting protein, the DOTA-Z(EGFR:2377) Affibody molecule.

METHODS

An anti-EGFR Affibody molecule, Z(EGFR:2377), was labelled with (111)In via the DOTA chelator site-specifically conjugated to a C-terminal cysteine. The affinity of DOTA-Z(EGFR:2377) for murine and human EGFR was measured by surface plasmon resonance. The cellular processing of (111)In-DOTA-Z(EGFR:2377) was evaluated in vitro. The biodistribution of radiolabelled Affibody molecules injected in a broad range of injected Affibody protein doses was evaluated in mice bearing EGFR-expressing A431 xenografts.

RESULTS

Site-specific coupling of DOTA provided a uniform conjugate possessing equal affinity for human and murine EGFR. The internalization of (111)In-DOTA-Z(EGFR:2377) by A431 cells was slow. In vivo, the conjugate accumulated specifically in xenografts and in EGFR-expressing tissues. The curve representing the dependence of tumour uptake on the injected Affibody protein dose was bell-shaped. The highest specific radioactivity (lowest injected protein dose) provided a suboptimal tumour-to-blood ratio. The results of the biodistribution study were confirmed by gamma-camera imaging.

CONCLUSION

The (111)In-DOTA-Z(EGFR:2377) Affibody molecule is a promising tracer for radionuclide molecular imaging of EGFR expression in malignant tumours. Careful optimization of protein dose is required for high-contrast imaging of EGFR expression in vivo.

Standardization of HER2 immunohistochemistry in breast cancer by automated quantitative analysis

CONTEXT

There is critical need for standardization of HER2 immunohistochemistry testing in the clinical laboratory setting. Recently, the American Society of Clinical Oncology and the College of American Pathologists have submitted guidelines recommending that laboratories achieve 95% concordance between assays and observers for HER2 testing.

OBJECTIVE

As a potential aid to pathologists for achieving these new guidelines, we have conducted an examination using automated quantitative analysis (AQUA analysis) to provide a standardized HER2 immunohistochemistry expression score across instruments (sites), operators, and staining runs.

DESIGN

We analyzed HER2 expression by immunohistochemistry in a cohort (n = 669) of invasive breast cancers in tissue microarray format across different instruments (n = 3), operators (n = 3), and staining runs (n = 3). Using light source, instrument calibration techniques, and a new generation of image analysis software, we produced normalized AQUA scores for each parameter and examined their reproducibility.

RESULTS

The average percent coefficients of variation across instruments, operators, and staining runs were 1.8%, 2.0%, and 5.1%, respectively. For positive/negative classification between parameters, concordance rates ranged from 94.5% to 99.3% for all cases. Differentially classified cases only occurred around the determined cut point, not over the entire distribution.

CONCLUSIONS

These data demonstrate that AQUA analysis can provide a standardized HER2 immunohistochemistry test that can meet current guidelines by the American Society of Clinical Oncology/College of American Pathologists. The use of AQUA analysis could allow for standardized and objective HER2 testing in clinical laboratories.

EGFRvIII-induced estrogen-independence, tamoxifen-resistance phenotype correlates with PgR expression and modulation of apoptotic molecules in breast cancer

The tumor-specific, ligand-independent, constitutively active epidermal growth factor receptor (EGFR) variant, EGFRvIII, remains understudied in breast cancer. Here, we report that expression of EGFRvIII in the ErbB-2-overexpressing, estrogen-dependent MDA-MB-361 breast cancer cell line resulted in significant estrogen-independent tumor growth in ovariectomized, athymic nude mice in comparison to MDA-MB-361/wt cells. MDA-MB-361/vIII breast cancer cells maintained estrogen-induced tumor growth, but were tamoxifen-resistant in the presence of estrogen, while MDA-MB-361/wt cells had a significant reduction in tumor growth in the presence of estrogen and tamoxifen. Tamoxifen alone did not have a significant effect on EGFRvIII-mediated estrogen-independent tumor growth. Constitutive signaling from the EGFRvIII receptor resulted in an increased activation of both the Akt and MAPK pathways. Compared to estrogen-dependent, tamoxifen-sensitive MCF-7/vIII breast cancer cells, which had unchanged levels of ERalpha, but an increase in progesterone receptor (PgR) in comparison to MCF-7/wt cells, MDA-MB-361/vIII cells had a reduction in ERalpha expression as well as a more pronounced reduction in PgR compared with MDA-MB-361/wt cells. EGFRvIII expression was also significantly associated with an absence of PgR protein in invasive human breast cancer specimens. Alterations of proapoptotic proteins and antiapoptotic proteins were observed in EGFRvIII transfectants. In conclusion, constitutive signaling through EGFRvIII and its downstream effector proteins crosstalks with the ERalpha pathway, resulting in loss of PgR expression and alterations in the apoptotic pathway, which may result in the estrogen-independent, tamoxifen-resistant phenotype conferred to EGFRvIII-expressing breast cancer cells.

G protein-coupled receptor 30 expression is up-regulated by EGF and TGF alpha in estrogen receptor alpha-positive cancer cells

In the present study, we evaluated the regulation of G protein-coupled receptor (GPR)30 expression in estrogen receptor (ER)-positive endometrial, ovarian, and estrogen-sensitive, as well as tamoxifen-resistant breast cancer cells. We demonstrate that epidermal growth factor (EGF) and TGF alpha transactivate the GPR30 promoter and accordingly up-regulate GPR30 mRNA and protein levels only in endometrial and tamoxifen-resistant breast cancer cells. These effects exerted by EGF and TGF alpha were dependent on EGF receptor (EGFR) expression and activation and involved phosphorylation of the Tyr(1045) and Tyr(1173) EGFR sites. Using gene-silencing experiments and specific pharmacological inhibitors, we have ascertained that EGF and TGF alpha induce GPR30 expression through the EGFR/ERK transduction pathway, and the recruitment of c-fos to the activator protein-1 site located within GPR30 promoter sequence. Interestingly, we show that functional cross talk of GPR30 with both activated EGFR and ER alpha relies on a physical interaction among these receptors, further extending the potential of estrogen to trigger a complex stimulatory signaling network in hormone-sensitive tumors. Given that EGFR/HER2 overexpression is associated with tamoxifen resistance, our data may suggest that ligand-activated EGFR could contribute to the failure of tamoxifen therapy also by up-regulating GPR30, which in turn could facilitates the action of estrogen. In addition, important for resistance is the ability of tamoxifen to bind to and activate GPR30, the expression of which is up-regulated by EGFR activation. Our results emphasize the need for new endocrine agents able to block widespread actions of estrogen without exerting any stimulatory activity on transduction pathways shared by the steroid and growth factor-signaling networks.

Resistance to endocrine therapy: are breast cancer stem cells the culprits?

From a developmental point of view, tumors can be seen as aberrant versions of their tissue of origin. For example, tumors often partially retain differentiation markers of their tissue of origin and there is evidence that they contain cancer stem cells (CSCs) that drive tumorigenesis. In this review, we summarise current evidence that breast CSCs may partly explain endocrine resistance in breast cancer. In normal breast, the stem cells are known to possess a basal phenotype and to be mainly ERalpha-. If the hierarchy in breast cancer reflects this, the breast CSC may be endocrine resistant because it expresses very little ERalpha and can only respond to treatment by virtue of paracrine influences of neighboring, differentiated ERalpha+ tumor cells. Normal breast epithelial stem cells are highly dependent on the EGFR and other growth factor receptors and it may be that the observed increased growth factor receptor expression in endocrine-resistant breast cancers reflects an increased proportion of CSCs selected by endocrine therapies. There is evidence from a number of studies that breast CSCs are ERalpha- and EGFR+/HER2+, which would support this view. CSCs also express mesenchymal genes which are suppressed by ERalpha expression, further indicating the mutual exclusion between ERalpha+ cells and the CSCs. As we learn more about CSCs, differentiation and the expression and functional activity of the ERalpha in these cells in diverse breast tumor sub-types, it is hoped that our understanding will lead to new modalities to overcome the problem of endocrine resistance in the clinic.

Estrogen-mediated suppression of the gene encoding protein tyrosine phosphatase PTPRO in human breast cancer: mechanism and role in tamoxifen sensitivity

We have previously demonstrated the tumor suppressor characteristics of protein tyrosine phosphatase receptor-type O (PTPRO) in leukemia and lung cancer, including its suppression by promoter methylation. Here, we show tumor-specific methylation of the PTPRO CpG island in primary human breast cancer. PTPRO expression was significantly reduced in established breast cancer cell lines MCF-7 and MDA-MB-231 due to promoter methylation compared with its expression in normal human mammary epithelial cells (48R and 184). Further, the silenced gene could be demethylated and reactivated in MCF-7 and MDA-MB-231 cells upon treatment with 5-Azacytidine, a DNA hypomethylating agent. Because PTPRO promoter harbors estrogen-responsive elements and 17beta-estradiol (E2) plays a role in breast carcinogenesis, we examined the effect of E2 and its antagonist tamoxifen on PTPRO expression in human mammary epithelial cells and PTPRO-expressing breast cancer cell line Hs578t. Treatment with E2 significantly curtailed PTPRO expression in 48R and Hs578t cells, which was facilitated by ectopic expression of estrogen receptor (ER)beta but not ERalpha. On the contrary, treatment with tamoxifen increased PTPRO expression. Further, knockdown of ERbeta by small interfering RNA abolished these effects of E2 and tamoxifen. Chromatin immunoprecipitation assay showed association of c-Fos and c-Jun with PTPRO promoter in untreated cells, which was augmented by tamoxifen-mediated recruitment of ERbeta to the promoter. Estradiol treatment resulted in dissociation of c-Fos and c-Jun from the promoter. Ectopic expression of PTPRO in the nonexpressing MCF-7 cells sensitized them to growth-suppressive effects of tamoxifen. These data suggest that estrogen-mediated suppression of PTPRO is probably one of the early events in estrogen-induced tumorigenesis and that expression of PTPRO could facilitate endocrine therapy of breast cancer.

Current situation of Panitumumab, Matuzumab, Nimotuzumab and Zalutumumab

EGFR overexpression usually correlates with a more advanced disease stage, a poorer prognosis and a worse chemotherapy response. EGFR expression increase has been observed in many tumours. For all the aforementioned reasons, EGFR inhibition can be considered an attractive approach in cancer treatment. One strategy has been receptor inhibition of extracellular domain using monoclonal antibodies. Cetuximab is the most developed one and there is plenty information on the literature about its current status. In this review we focus on other EGFR monoclonal antibodies under clinical development. The more developed one is Panitumumab. Its clinical development is taking place very quickly and it has mainly been studied in colorectal cancer showing promising results. There are also other interesting drugs such as Matuzumab, Nimotuzumab and Zalutumumab.