Hydrogel-based protein array for quantifying epidermal growth factor receptor activity in cell lysates

EGFR-conjugated hydrogel accelerates wound healing on ulcer-induced burn wounds by targeting collagen and inflammatory cells using photoimmunomodulatory inhibition

In the present study, we fabricated an epidermal growth factor receptor (EGFR)-conjugated hydrogel to promote wound healing in cold restraint-induced gastric ulceration on burn wounds targeting collagen and inflammatory cells for the treatment of burns and gastric ulcers. Cytotoxicity and cell proliferation assays demonstrated good biocompatibility of hydrogel as a suitable extracellular matrix for targeted cells and support for regenerative cell growth. These findings were confirmed by staining methods. In vitro wound healing was confirmed cell migration in the targeted cells. The effect of the EGFR-H was investigated in cold restraint-induced gastric ulcers in rats, where the treatment was started immediately after ulcer induction. In the in vivo experiment, the EGFR-H demonstrated enhanced ulcer healing ability and less scarring compared to the hydrogel alone and controls. Thus, EGFR-H promotes healing of cold restraint-induced gastric ulcer via EGFR conjugated with a hydrogel. The present study demonstrates a novel pathway to fabricate hydrogels as suitable wound dressing biomaterials to improve deep partial thickness burn wound healing and prevent scar formation when aided by laser therapy.

Epidermal growth factor receptor conjugated fucoidan/alginates loaded hydrogel for activating EGFR/AKT signaling pathways in colon cancer cells during targeted photodynamic therapy

In the present study, we developed epidermal growth factor receptor conjugated fucoidan/alginate loaded hydrogels for targeting the delivery of hydrogel through the signaling pathway of the epidermal growth factor receptor (EGFR) to treat colon cancer. We aim to develop a drug delivery system of chlorin e6 encapsulated in hydrogel and tag it with EFGR to target cancer cells with low toxicity and limited side effects by using photodynamic therapy (PDT). The characterization and in vitro studies were conducted to evaluate the efficiency of the EGFR-hydrogel in colon cancer cells. Also, western blot analysis was used to assess protein expression levels. The in vitro results confirmed significant cell viability, proliferation, and migration of hydrogel in colon cancer. The cellular effects of the EFGR/AKT pathway were cell proliferation, inhibition of apoptosis, cell cycle progression, and cell survival and migration of colon cancer because of significant protein expression levels. The data suggested that hydrogel appears to be a promising targeting approach-PDT for treating colon cancer. Further in vivo studies are needed to conclude the overexpression level of EGFR on cancer cells. The study concluded that EGFR-H improved the targeting efficiency of hydrogel in colon cancer.

Hydrogel-based suspension array for biomarker detection using horseradish peroxidase-mediated silver precipitation

Advances in medical diagnostics and personalized therapy require robust, sensitive yet cost-effective diagnostic tools for rapid measurement of biomolecules including proteins in body fluids. State-of-the-art technologies are complex and rely on expensive or custom made detection system, and therefore, cannot be readily adapted for point-of-care (POC) analysis. The development of a novel detection platform, which leverages horseradish peroxidase (HRP)-mediated silver precipitation within antibody immobilized porosity tuned poly (ethylene) glycol diacrylate (PEGDA) hydrogel microparticles with the operational advantages of suspension arrays for sensitive quantification of biomarkers, is described. In this study, vascular endothelial growth factor (VEGF) has been used as a model protein. The silver deposition corresponded to the concentration of VEGF in solution. The detection limit of 5.2 ± 1.0 pg/mL and assay time of 2 h highlights that this assay exceeds the conventional technologies in terms of sensitivity and speed. The practical applicability of the hydrogel microparticle based detection system has been established by demonstrating the ability of the system to quantify the production of VEGF by highly aggressive (MDA-MB-231) and non-aggressive (MCF-7) breast cancer cells. The reliance on simple instrument for quantification of clinically relevant markers bolsters the adaptability of the detection platform/method in POC settings.

Sensitive, quantitative, and high-throughput detection of angiogenic markers using shape-coded hydrogel microparticles

Demonstration of the application of shape coded hydrogel microparticles for multiplexed detection of angiogenic molecules. Utilization of single fluorophore eliminates the spectral overlap associated with microparticle based multiplexed analysis.

Multiplexed tyrosine kinase activity detection in cancer cells using a hydrogel immobilized substrate

Kinases play a key role in cellular signaling, and the overactivation or overexpression of these kinases has been linked to a variety of cancers. Tyrosine kinase inhibitors treat the mechanism of these cancers by targeting the specific kinases that are overactive. Some patients, however, do not respond to these inhibitors or develop resistance to these inhibitors during treatment. Additionally, even within cancers of the same tissue type, different kinases may be overactive in different patients. For example, some lung cancers overexpress epidermal growth factor receptor (EGFR) and respond to EGFR inhibitors, whereas other lung cancers do not overexpress EGFR and receive no benefit from this treatment. Even among patients exhibiting EGFR overexpression, some do not respond to EGFR kinase inhibitors because other kinases, such as Met kinase, are also overactivated. Here we describe a quantitative and specific multiplexed microfluidic assay using a hydrogel immobilized substrate for measuring the kinase activity of Met and Abl kinase from cancer cells. We immobilized kinase-specific substrates on macroporous hydrogel micropillars in microchannels. These microchannels were incubated with 6 μl of a kinase reaction solution containing cancer cell lysate, and we measured kinase activity via fluorescence detection of a phosphotyrosine antibody. We showed that the assay can specifically measure the activity of both Met and Abl kinase within one microchannel and has the potential to measure the activity of as many as five kinases within one microchannel. The assay also detected Met kinase inhibition from lysates of cancer cells grown in the Met kinase inhibitor PHA665752.

Protein analytical assays for diagnosing, monitoring, and choosing treatment for cancer patients

Cancer treatment is often hindered by inadequate methods for diagnosing the disease or insufficient predictive capacity regarding therapeutic efficacy. Targeted cancer treatments, including Bcr-Abl and EGFR kinase inhibitors, have increased survival for some cancer patients but are ineffective in other patients. In addition, many patients who initially respond to targeted inhibitor therapy develop resistance during the course of treatment. Molecular analysis of cancer cells has emerged as a means to tailor treatment to particular patients. While DNA analysis can provide important diagnostic information, protein analysis is particularly valuable because proteins are more direct mediators of normal and diseased cellular processes. In this review article, we discuss current and emerging protein assays for improving cancer treatment, including trends toward assay miniaturization and measurement of protein activity.

Activity assay of epidermal growth factor receptor tyrosine kinase inhibitors in triple-negative breast cancer cells using peptide-conjugated magnetic beads

Triple-negative breast cancer (TNBC) is a highly aggressive subtype of breast cancer with limited treatment options. Epidermal growth factor receptor I (EGFR) has emerged as a promising target in TNBC. Limited success of the EGFR kinase inhibiting small molecules in clinical trials may be attributed in part to inaccuracy in identifying EGFR signatures in patient tumors. In light of the absence of a simple correlation between EGFR expression and its degree of activation, a simple and reliable tool that can quantify EGFR kinase activity in tumor samples may be of therapeutic value in predicting patient-specific EGFR targeted therapies. This study reports the development of an assay that can quantitatively profile EGFR kinase activities and inhibitor sensitivities in TNBC cell lysates by using peptide reporters covalently tethered to magnetic beads in a controlled orientation. The use of magnetic beads provides rapid sample handling and easy product isolation. The potential of this approach was demonstrated by screening a set of five clinically relevant EGFR tyrosine kinase inhibitors. Formatted for microwell plates, this magnetic bead-based kinase assay may be used as a complementary approach for direct high-throughput screening of small molecule inhibitors.

Macroporous hydrogel micropillars for quantifying Met kinase activity in cancer cell lysates

Overactive and overexpressed kinases have been implicated in the cause and progression of many cancers. Kinase inhibitors offer a targeted approach for treating cancers associated with increased or deregulated kinase activity. Often, however, cancer cells exhibit initial resistance to these inhibitors or evolve to develop resistance during treatment. Additionally, cancers of any one tissue type are typically heterogeneous in their oncogenesis mechanisms, and thus diagnosis of a particular type of cancer does not necessarily provide insight into what kinase therapies may be effective. For example, while some lung cancer cells that overexpress the epidermal growth factor receptor (EFGR) respond to treatment with EGFR kinase inhibitors, overexpression or hyperactivity of Met kinase correlates with resistance to EGFR kinase inhibitors. Here we describe a microfluidic-based assay for quantifying Met kinase activity in cancer cell lysates with the eventual goals of predicting cancer cell responsiveness to kinase inhibitors and monitoring development of resistance to these inhibitors. In this assay, we immobilized a phosphorylation substrate for Met kinase into macroporous hydrogel micropillars. We then exposed the micropillars to a cancer cell lysate and detected substrate phosphorylation using a fluorescently conjugated antibody. This assay is able to quantify Met kinase activity in whole cell lysate from as few as 150 cancer cells. It can also detect cells expressing overactive Met kinase in a background of up to 75% non-cancerous cells. Additionally, the assay can quantify kinase inhibition by the Met-specific kinase inhibitors SU11274 and PHA665752, suggesting predictive capability for cellular response to kinase inhibitors.

Quantification of kinase activity in cell lysates via photopatterned macroporous poly(ethylene glycol) hydrogel arrays in microfluidic channels

The efficacy of tyrosine kinase inhibitors (TKIs) as cancer therapeutics varies amongst individual patients as a result of patient-specific differences in molecular regulation of cancer development and progression, and acquisition of resistance to TKIs during therapy. A sensitive assay that can quantify kinase activity and predict inhibition of that activity from minimally invasive patient tissue samples may aid design of efficacious individualized TKI treatments. A microfluidic format can be useful in reducing limitations in standard protein kinase assays, including sensitivity required and low sample volume available. We present photopatterned macroporous poly(ethylene glycol) diacrylate hydrogel pillars functionalized with kinase substrates within microchannels for quantifying kinase activity in complex cellular lysates. We determined the effect of using a porogen to induce macroporosity in hydrogel pillars and showed that hydrogel poration enhanced the sensitivity of detecting Bcr-Abl activity in cell lysates by an order of magnitude. Bcr-Abl tyrosine kinase activity in K562 cell lysates could be detected from 0.01 μg/μL of cell lysate, corresponding to approximately 500 cells, using GST-Crkl immobilized in macroporous hydrogels. This device was also capable of quantifying inhibition of Bcr-Abl activity by imatinib mesylate, which demonstrates the potential to predict the biochemical response to drug inhibitors. These results indicate that microfluidic devices containing macroporous hydrogels functionalized with kinase substrates provide a promising platform for sensitive and specific quantification of kinase activity and efficacy of kinase inhibitors in cancer cell lysates.

Development of macroporous poly(ethylene glycol) hydrogel arrays within microfluidic channels

The mass transport of solutes through hydrogels is an important design consideration in materials used for tissue engineering, drug delivery, and protein arrays used to quantify protein concentration and activity. We investigated the use of poly(ethylene glycol) (PEG) as a porogen to enhance diffusion of macromolecules into the interior of polyacrylamide and PEG hydrogel posts photopatterned within microfluidic channels. The diffusion of GST-GFP and dextran-FITC into hydrogels was monitored and effective diffusion coefficients were determined by fitting to the Fickian diffusion equations. PEG-diacrylate (M(r) 700) with porogen formed a macroporous structure and permitted significant penetration of 250 kDa dextran. Proteins copolymerized in these macroporous hydrogels retained activity and were more accessible to antibody binding than proteins copolymerized in nonporous gels. These results suggest that hydrogel macroporosity can be tuned to regulate macromolecular transport in applications such as tissue engineering and protein arrays.

Quantifying the sensitivities of EGF receptor (EGFR) tyrosine kinase inhibitors in drug resistant non-small cell lung cancer (NSCLC) cells using hydrogel-based peptide array

Epidermal growth factor receptor (EGFR) signaling plays an important role in non-small cell lung cancer (NSCLC) and therapeutics targeted against EGFR have been effective in treating a subset of patients bearing somatic EFGR mutations. However, the cancer eventually progresses during treatment with EGFR inhibitors, even in the patients who respond to these drugs initially. A large variety of distinct irreversible inhibitors have been developed, which may combat therapeutic resistance. Nonetheless, major challenges in tailoring patient-specific treatment regimens involve predicting the most effective inhibitors and monitoring for acquisition of resistance. A patient-customized, predictive diagnostic that quantifies the effects of specific anti-EGFR therapies may improve outcomes in cancers where EGFR plays a mechanistic role. In this study we used an EGFR-phosphorylatable peptide, AEEEEYFELVAKKK, immobilized within a polyacrylamide hydrogel as a substrate for profiling the activation status of EGFR in the cellular extracts of erlotinib-resistant cancer cells. The hydrogel array was able to detect therapeutic resistance as well as identify inhibitors capable of combating therapeutic resistance. These findings establish the potential of this protein-acrylamide copolymer hydrogel array to not only evaluate EGFR status in cancer cell lysates but also to screen for the most promising therapeutics for individual patients and monitor effects of treatment on acquisition of resistance to EGFR inhibitors.

Cell treatment and lysis in 96-well filter-bottom plates for screening Bcr-Abl activity and inhibition in whole-cell extracts

Although conventional high-throughput screens performed in vitro with purified protein kinases are powerful tools to discover new kinase inhibitors, they are far from ideal for determining efficacy in vivo. As a complementary approach, cell-based, target-driven secondary screens may help predict in vivo compound potency and specificity as well as evaluate bioavailability and toxicity. Here the authors report a simple protocol for treating K562 Bcr-Abl-expressing cells with small-molecule kinase inhibitors in 96-well filter-bottom plates followed by in-plate cell lysis. The lysates were assayed via a solid-phase kinase assay, allowing determination of apparent IC(50) for known Bcr-Abl inhibitors as well as facilitating the screening of a small kinase inhibitor library. This approach may have further applications in generating lysates for analyzing kinase activity and inhibition in other nonadherent suspension cell lines.