Panitumumab: in metastatic colorectal cancer with wild-type KRAS

Mutation analysis of a 10-gene panel for colorectal cancer in Huizhou, Guangdong Province of China

Objective

This study aimed to investigate the type and frequency of mutations in 10 genes in 85 colorectal cancer (CRC) patients in Huizhou and the guiding significance of targeted drug use.

Methods

The 10-gene panel next-generation sequencing (NGS) was used to assess genetic variants in 85 CRC patients from the Huizhou area combined with clinical information for a comprehensive analysis.

Results

Upon initial mutation testing, 68% (58/85) were positive. The mutation frequencies of these genes, including KRAS, PIK3CA, NRAS, ERBB2, BRAF, EGFR, and PDGFRA, were 51%, 20%, 5%, 4%, 4%, 1%, and 1%, respectively. Overall, 29 mutation types were detected from seven genes. More mutations were detected in more advanced cancers. There were three samples with multiple mutations of a single gene, including KRAS (n = 2) and ERBB2 (n = 2), 12 samples with multiple mutations of double genes, including KRAS/PIK3CA (n = 10), BRAF/PIK3CA (n = 1), and NRAS/PIK3CA (n = 1), and one sample with multiple mutations of three genes, including ERBB2/KRAS/PIK3CA (n = 1). Theoretically, 27 patients could receive targeted treatment. During the actual treatment, 10 patients received bevacizumab, cetuximab, or fruquintinib with no progression ranging from 12 to 24 months.

Conclusion

Gene mutations detected by a 10-gene panel were useful for targeting therapy of CRC in Huizhou.

Epitope Mapping of an Antihuman EGFR Monoclonal Antibody (EMab-134) Using the REMAP Method

The epidermal growth factor receptor (EGFR) is a tyrosine kinase receptor that plays an important role in normal epidermal cell physiology. EGFR is overexpressed in cancer cells and has a number of mutations that implicate tumor malignancy, development, and poor patient prognosis; thus, EGFR is an attractive target for cancer therapy. At present, anti-EGFR monoclonal antibodies (mAbs) have been approved and are used for treating patients with a variety of EGFR-expressing cancers. Epitope mapping is important in identifying the therapeutic mechanism of anti-EGFR mAbs; however, the development of epitope mapping techniques lags behind the development of antimolecular target mAbs, including anti-EGFR mAbs. Hence, in this study, a novel epitope mapping method, RIEDL insertion for epitope mapping (REMAP) method, was developed. The results of this study demonstrated that the critical epitope of anti-EGFR mAb EMab-134 is Gly378, Asp379, Ser380, Phe381, Thr382, His383, Thr384, Pro385, and Pro386 of EGFR. The REMAP method could be useful for determining the critical epitope of functional mAbs against many target molecules.

Partitioned Extracts of Bauhinia championii Induce G0/G1 Phase Arrest and Apoptosis in Human Colon Cancer Cells

Bauhinia championii (Benth.) is one of the commonly used herbs in Taiwan. The stem of this plant has been used to treat epigastria pain and rheumatoid arthritis. However, the antitumor activities of this herb have never been reported. This study aims to investigate the mechanism of anticancer activity of the extracts from B. championii (BC). BC was fractionated with a series of organic solvents, including n-hexane (H), ethyl acetate (EA), 1-butanol (B), and water (W). We first investigated the effects of BC-H, BC-EA, BC-B and BC-W partitioned fraction on cell viability. In HCT 116 colon cancer cell lines, BC-EA showed the highest inhibition of cell viability and changed the morphology of cells. With dose- and time-dependent manners, BC-EA inhibited the proliferation of HCT 116 cells by inducing apoptosis and G₀/G₁ phase arrest of cell cycle. To determine the underlying mechanisms, down-regulated CDK2, Cyclin D, and Cyclin E and up-regulated p16, p21, and p53 may account for the cell cycle arrest, while the apoptotic effect of BC-EA may attribute to increased intracellular Ca2+, loss of mitochondria membrane potential (ΔΨm), increase of Bax, Bak, puma, and AIF, and decrease of Bcl-2. Furthermore, the inactivation of Ras signaling pathway by BC-EA also contributed to its apoptotic effect on HCT 116. Our study demonstrates that BC-EA not only inhibits cell growth but also induces apoptosis through inhibiting Ras signal pathway and increasing p53 expression levels. We suggest that BC-EA may be a new dietary supplement and a useful tool to search for therapeutic candidates against colon cancer.

EGFRvIII: An Oncogene with Ambiguous Role

Epidermal growth factor receptor variant III (EGFRvIII) seems to constitute the perfect therapeutic target for glioblastoma (GB), as it is specifically present on up to 28-30% of GB cells. In case of other tumor types, expression and possible role of this oncogene still remain controversial. In spite of EGFRvIII mechanism of action being crucial for the design of small active anticancer molecules and immunotherapies, i.e., CAR-T technology, it is yet to be precisely defined. EGFRvIII is known to be resistant to degradation, but it is still unclear whether it heterodimerizes with EGF-activated wild-type EGFR (EGFRWT) or homodimerizes (including covalent homodimerization). Constitutive kinase activity of this mutated receptor is relatively low, and some researchers even claim that a nuclear, but not a membrane function, is crucial for its activity. Based on the analyses of recurrent tumors that are often lacking EGFRvIII expression despite its initial presence in corresponding primary foci, this oncogene is suggested to play a marginal role during later stages of carcinogenesis, while even in primary tumors EGFRvIII expression is detected only in a small percentage of tumor cells, undermining the rationality of EGFRvIII-targeting therapies. On the other hand, EGFRvIII-positive cells are resistant to apoptosis, more invasive, and characterized with enhanced proliferation rate. Moreover, expression of this oncogenic receptor was also postulated to be a marker of cancer stem cells. Opinions regarding the role that EGFRvIII plays in tumorigenesis and for tumor aggressiveness are clearly contradictory and, therefore, it is crucial not only to determine its mechanism of action, but also to unambiguously define its role at early and advanced cancer stages.

Non-Coding RNAs and Resistance to Anticancer Drugs in Gastrointestinal Tumors

Non-coding RNAs are important regulators of gene expression and transcription. It is well established that impaired non-coding RNA expression especially the one of long non-coding RNAs and microRNAs is involved in a number of pathological conditions including cancer. Non-coding RNAs are responsible for the development of resistance to anticancer treatments as they regulate drug resistance-related genes, affect intracellular drug concentrations, induce alternative signaling pathways, alter drug efficiency via blocking cell cycle regulation, and DNA damage response. Furthermore, they can prevent therapeutic-induced cell death and promote epithelial-mesenchymal transition (EMT) and elicit non-cell autonomous mechanisms of resistance. In this review, we summarize the role of non-coding RNAs for different mechanisms resulting in drug resistance (e.g., drug transport, drug metabolism, cell cycle regulation, regulation of apoptotic pathways, cancer stem cells, and EMT) in the context of gastrointestinal cancers.

Panitumumab-Conjugated and Platinum-Cored pH-Sensitive Apoferritin Nanocages for Colorectal Cancer-Targeted Therapy

Apoferritin (AF) is a natural nontoxic iron carrier and has a natural hollow structure that can be used to deliver small molecules. The surface of AF has many amine functional groups that can be modified to create targeted ligands. We loaded oxaliplatin onto AF, which was then used as a template to conjugate with panitumumab via a polyethylene glycol linker. The oxaliplatin-loaded AF conjugated with panitumumab (AFPO) was designed to specifically target cell lines expressing epidermal growth factor receptor (EGFR). AFPO efficiently released oxaliplatin and suppressed tumor cell growth. Furthermore, the novel AFPO nanocages showed significant inhibition and greater accumulation in tumor models with high EGFR expression in vivo. Our study revealed that combining panitumumab and oxaliplatin into one formulation (AFPO nanocage) could be a promising shortcut in clinical applications.

Exploitation of Gene Expression and Cancer Biomarkers in Paving the Path to Era of Personalized Medicine

Cancer therapy agents have been used extensively as cytotoxic drugs against tissue or organ of a specific type of cancer. With the better understanding of molecular mechanisms underlying carcinogenesis and cellular events during cancer progression and metastasis, it is now possible to use targeted therapy for these molecular events. Targeted therapy is able to identify cancer patients with dissimilar genetic defects at cellular level for the same cancer type and consequently requires individualized approach for treatment. Cancer therapy begins to shift steadily from the traditional approach of “one regimen for all patients” to a more individualized approach, through which each patient will be treated specifically according to their specific genetic defects. Personalized medicine accordingly requires identification of indicators or markers that guide in the decision making of such therapy to the chosen patients for more effective therapy. Cancer biomarkers are frequently used in clinical practice for diagnosis and prognosis, as well as identification of responsive patients and prediction of treatment response of cancer patient. The rapid breakthrough and development of microarray and sequencing technologies is probably the main tool for paving the way toward “individualized biomarker-driven cancer therapy” or “personalized medicine”. In this review, we aim to provide an updated knowledge and overview of the current landscape of cancer biomarkers and their role in personalized medicine, emphasizing the impact of genomics on the implementation of new potential targeted therapies and development of novel cancer biomarkers in improving the outcome of cancer therapy.

Adaptive responses to antibody based therapy

Receptor tyrosine kinases (RTKs) represent a large class of protein kinases that span the cellular membrane. There are 58 human RTKs identified which are grouped into 20 distinct families based upon their ligand binding, sequence homology and structure. They are controlled by ligand binding which activates intrinsic tyrosine-kinase activity. This activity leads to the phosphorylation of distinct tyrosines on the cytoplasmic tail, leading to the activation of cell signaling cascades. These signaling cascades ultimately regulate cellular proliferation, apoptosis, migration, survival and homeostasis of the cell. The vast majority of RTKs have been directly tied to the etiology and progression of cancer. Thus, using antibodies to target RTKs as a cancer therapeutic strategy has been intensely pursued. Although antibodies against the epidermal growth factor receptor (EGFR) and human epidermal growth factor receptor 2 (HER2) have shown promise in the clinical arena, the development of both intrinsic and acquired resistance to antibody-based therapies is now well appreciated. In this review we provide an overview of the RTK family, the biology of EGFR and HER2, as well as an in-depth review of the adaptive responses undertaken by cells in response to antibody based therapies directed against these receptors. A greater understanding of these mechanisms and their relevance in human models will lead to molecular insights in overcoming and circumventing resistance to antibody based therapy.

The future of pharmacogenetics in the treatment of heart failure

Heart failure is a common disease with high levels of morbidity and mortality. Current treatment comprises β-blockers, ACE inhibitors, aldosterone antagonists and diuretics. Variation in clinical response seen in patients begs the question of whether there is a pharmacogenetic component yet to be identified. To date, the genes most studied involve the β-1, β-2, α-2 adrenergic receptors and the renin-angiotensin-aldosterone pathway, mainly focusing on SNPs. However results have been inconsistent. Genome-wide association studies and next-generation sequencing are seen as alternative approaches to discovering genetic variations influencing drug response. Hopefully future research will lay the foundations for genotype-led drug management in these patients with the ultimate aim of improving their clinical outcome.

MR signal amplification for imaging of the mutant EGF receptor in orthotopic human glioma model

PURPOSE

To investigate the potential of targeted MR signal amplification strategy for imaging of EGF receptor variant III (EGFRvIII) overexpression associated with the infiltrating margin of aggressive orthotopic brain tumors.

PROCEDURES

F(ab')2 fragments of humanized anti-EGFRvIII monoclonal antibody (EMD72000) were linked to deglycosylated horseradish peroxidase (HRP) and glucose oxidase (GOX). Detection of the F(ab')2 conjugate pair colocalization in vivo was enabled by a subsequent IV injection of a low molecular weight paramagnetic substrate of HRP, diTyr-GdDTPA.

RESULTS

The delivery of the targeted fragments to the tumor was validated using SPECT/CT imaging of radiolabeled anti-EGFRvIII F(ab')2 conjugates. Further, by using 3 T MRI, we observed time-dependent differences in tumor signal intensity and signal retention at the endpoint depending on whether or not the animals were pre-injected with the anti-EGFRvIII F(ab')2 conjugates.

CONCLUSIONS

Imaging of EGFRvIII expression in vivo was enabled by consecutive administration of targeted F(ab')2 conjugates and a paramagnetic substrate resulting in a tumor-specific receptor detection with high specificity and resolution.

Emerging combination therapies to overcome resistance in EGFR-driven tumors

The epidermal growth factor receptor (EGFR) is responsible for the growth and progression of tumor cells; its overexpression and deregulation of its downstream signaling pathway have been found in many different neoplasms. These characteristics make it an ideal target for cancer treatment. Two classes of EGFR inhibitors, which bind to different parts of this molecule, have been developed and studied: monoclonal antibodies, such as cetuximab and panitumumab and tyrosine kinase inhibitors, including erlotinib and gefitinib. The effectiveness of these new drugs is considerably reduced by a number of mechanisms of resistance developed by tumor cells. Hence, there is a clear need for better characterization of these processes and finding new therapeutic strategies to make the action of these drugs more incisive. Here, we describe some of the mechanisms of resistance to EGFR inhibitors and review the main innovations attempting to overcome these drawbacks.

Metastasis-associated factors facilitating the progression of colorectal cancer

Tumor metastasis remains the principal cause of treatment failure and poor prognosis in patients with colorectal cancer. It is a multistage process which includes proteolysis, motility and migration of cells, proliferation in a new site, and neoangiogenesis. A crucial step in the process of intra- and extra-vasation is the activation of proteolytic enzymes capable of degrading the extracellular matrix (ECM). In this stage, urokinase plasminogen activator receptor (uPAR) and matrix metalloproteinases (MMPs) are necessary. Micrometastases need the presence of growth factor and vascular growth factor so that they can form macrometastasis. In addition, cell adhesion molecules (CAMs) and guanine nucleotide exchange factors (GEFs) play important roles in the progression of colorectal cancer and metastatic migration. Further elucidation of the mechanisms of how these molecules contribute will aid in the identification of diagnostic and prognostic markers as well as therapeutic targets for patients with colorectal metastasis.

Pharmacogenetics: practices and opportunities for study design and data analysis

Pharmacogenetics (PGx) is increasingly used as a way to target treatment to patients who are most likely to benefit. To date, PGx has shown clinical significance across a few applications but widespread use has been limited by the need for further technical, methodological and practical advances and for educating clinical researchers on the value of PGx. Here, I describe the current scope of PGx research, including recent contributions to prospective study design. A case study is included to demonstrate the limitations of current practice and to describe some practical steps for improving the chances of identifying genetic effects. Additionally, I describe some opportunities for the integration and application of disparate data sources in exploratory PGx research.

Targeted signal-amplifying enzymes enhance MRI of EGFR expression in an orthotopic model of human glioma

Epidermal growth factor receptor (EGFR) imaging in brain tumors is essential to visualize overexpression of EGFRvIII variants as a signature of highly aggressive gliomas and to identify patients that would benefit from anti-EGFR therapy. Seeking imaging improvements, we tested a novel pretargeting approach that relies on initial administration of enzyme-linked anti-EGFR monoclonal antibodies (mAb; EMD72000) followed by administration of a low-molecular-weight paramagnetic molecule (diTyr-GdDTPA) retained at the site of EGFR mAb accumulation. We hypothesized that diTyr-GdDTPA would become enzyme activated and retained on cells due to binding to tissue proteins. In support of this hypothesis, mAb-enzyme conjugates reacted with both membrane-isolated wild-type (wt) EGFR and EGFRvIII, but they bound primarily to EGFRvIII-expressing cells and not to EGFRwt-expressing cells. In vivo analysis of magnetic resonance (MR) tumor signal revealed differences in MR signal decay following diTyr-GdDTPA substrate administration. These differences were significant in that they suggested differences in substrate elimination from the tissue which relied on the specificity of the initial mAb binding: a biexponential signal decay was observed in tumors only upon preinjection with EGFR-targeted conjugates. Endpoint MRI in this setting revealed detailed images of tumors which correlated with immunohistochemical detection of EGFR expression. Together, our findings suggest an improved method to identify EGFRvIII-expressing gliomas in vivo that are best suited for treatment with therapeutic EGFR antibodies.