Pharmacotherapy targeting the EGFR oncogene in NSCLC

Natural tyrosine kinase inhibitors acting on the epidermal growth factor receptor: Their relevance for cancer therapy

Epidermal growth factor receptor (EGFR), also known as ErbB-1/HER-1, plays a key role in the regulation of the cell proliferation, migration, differentiation, and survival. Since the constitutive activation or overexpression of EGFR is nearly found in various cancers, the applications focused on EGFR are the most widely used in the clinical level, including the therapeutic drugs of targeting EGFR, monoclonal antibodies (mAbs) and tyrosine kinase inhibitors (TKIs).Over the past decades, the compounds from natural sources have been a productive source of novel drugs, especially in both discovery and development of anti-tumor drugs by targeting the EGFR pathways as the TKIs. This work presents a review of the compounds from natural sources as potential EGFR-TKIs involved in the regulation of cancer. Moreover, high-throughput drug screening of EGFR-TKIs from the natural compounds has also been summarized.

Rethink of EGFR in Cancer With Its Kinase Independent Function on Board

The epidermal growth factor receptor (EGFR) is one of most potent oncogenes that are commonly altered in cancers. As a receptor tyrosine kinase, EGFR's kinase activity has been serving as the primary target for developing cancer therapeutics, namely the EGFR inhibitors including small molecules targeting its ATP binding pocket and monoclonal antibodies targeting its ligand binding domains. EGFR inhibitors have produced impressive therapeutic benefits to responsive types of cancers. However, acquired and innate resistances have precluded current anti-EGFR agents from offering sustainable benefits to initially responsive cancers and benefits to EGFR-positive cancers that are innately resistant. Recent years have witnessed a realization that EGFR possesses kinase-independent (KID) pro-survival functions in cancer cells. This new knowledge has offered a different angle of understanding of EGFR in cancer and opened a new avenue of targeting EGFR for cancer therapy. There are already many excellent reviews on the role of EGFR with a focus on its kinase-dependent functions and mechanisms of resistance to EGFR targeted therapies. The present opinion aims to initiate a fresh discussion about the function of EGFR in cancer cells by laying out some unanswered questions pertaining to EGFR in cancer cells, by rethinking the unmet therapeutic challenges from a view of EGFR's KID function, and by proposing novel approaches to target the KID functions of EGFR for cancer treatment.

Overexpression of LIMD2 promotes the progression of non-small cell lung cancer

LIM domain containing 2 (LIMD2) is a small LIM-only protein that has been demonstrated to promote tumor progression; however, the expression and function of LIMD2 in non-small cell lung cancer (NSCLC) has not previously been reported. In the present study, reverse transcription-quantitative PCR and western blot analysis were conducted to examine the mRNA and protein expression levels of LIMD2. Cell Counting Kit-8, Transwell and wound-healing assays were performed in order to examine cell proliferation, invasion and migration, respectively. The data revealed that the LIMD2 expression levels were significantly increased in NSCLC tissues and cell lines, compared with adjacent non-tumor tissues and normal lung epithelial cells, respectively. In addition, the high expression of LIMD2 was significantly associated with lymph node metastasis, distant metastasis and advanced clinical stage in NSCLC. The patients with NSCLC with a high expression of LIMD2 exhibited shorter survival times than those with low LIMD2 expression. The knockdown of LIMD2 caused remarkable decreases in NSCLC cell proliferation, migration and invasion. Bioinformatics analysis and luciferase reporter gene assay data further confirmed that LIMD2 was a direct target gene of microRNA-124 (miR-124), a well-known tumor suppressor in NSCLC. The expression of LIMD2 was negatively regulated by miR-124 in NSCLC cells. In addition, miR-124 was downregulated in NSCLC tissues compared with adjacent non-tumor tissues, and an inverse correlation was observed between the expression of LIMD2 and miR-124 in NSCLC tissues. In conclusion, the present study demonstrates that LIMD2 serves an oncogenic role in NSCLC, suggesting that it may be used as a potential therapeutic target for the treatment of NSCLC.

STAT3 signaling mediates tumour resistance to EGFR targeted therapeutics

Several EGFR inhibitors are currently undergoing clinical assessment or are approved for the clinical management of patients with varying tumour types. However, treatment often results in a lack of response in many patients. The majority of patients that initially respond eventually present with tumours that display acquired resistance to the original therapy. A large number of receptor tyrosine and intracellular kinases have been implicated in driving signaling that mediates this tumour resistance to anti-EGFR targeted therapy, and in a few cases these discoveries have led to overall changes in prospective tumour screening and clinical practice (K-RAS in mCRC and EGFR T790M in NSCLC). In this mini-review, we specifically focus on the role of the STAT3 signaling axis in providing both intrinsic and acquired resistance to inhibitors of the EGFR. We also focus on STAT3 pathway targeting in an attempt to overcome resistance to anti-EGFR therapeutics.

Prevalence of EGFR Mutations in Lung Cancer in Uruguayan Population

BACKGROUND

Incorporation of molecular analysis of the epidermal growth factor receptor (EGFR) gene into routine clinical practice represents a milestone for personalized therapy of the non-small-cell lung cancer (NSCLC). However, the genetic testing of EGFR mutations has not yet become a routine clinical practice in developing countries. In view of different prevalence of such mutations among different ethnicities and geographic regions, as well as the limited existing data from Latin America, our aim was to study the frequency of major types of activating mutations of the EGFR gene in NSCLC patients from Uruguay.

METHODS

We examined EGFR mutations in exons 18 through 21 in 289 NSCLC Uruguayan patients by PCR-direct sequencing.

RESULTS

EGFR mutations were detected in 53 of the 289 (18.3%) patients, more frequently in women (23.4%) than in men (14.5%). The distribution by exon was similar to that generally reported in the literature.

CONCLUSIONS

This first epidemiological study of EGFR mutations in Uruguay reveals a wide spectrum of mutations and an overall prevalence of 18.3%. The background ethnic structure of the Uruguayan population could play an important role in explaining our findings.

Extreme assay sensitivity in molecular diagnostics further unveils intratumour heterogeneity in metastatic colorectal cancer as well as artifactual low-frequency mutations in the KRAS gene

Background:

Gene mutations in the RAS family rule out metastatic colorectal carcinomas (mCRCs) from anti-EGFR therapies.

Methods:

We report a retrospective analysis by Sequenom Massarray and fast COLD-PCR followed by Sanger sequencing on 240 mCRCs.

Results:

By Sequenom, KRAS and NRAS exons 2-3-4 were mutated in 52.9% (127/240) of tumours, while BRAF codon 600 mutations reached 5% (12/240). Fast COLD-PCR found extra mutations at KRAS exon 2 in 15/166 (9%) of samples, previously diagnosed by Sequenom as wild-type or mutated at RAS (exons 3-4) or BRAF genes. After UDG digestion results were reproduced in 2/12 analysable subclonally mutated samples leading to a frequency of true subclonal KRAS mutations of 1.2% (2.1% of the previous Sequenom wild-type subgroup). In 10 out of 12 samples, the subclonal KRAS mutations disappeared (9 out of 12) or turned to a different sequence variant (1 out of 12).

Conclusions:

mCRC can harbour coexisting multiple gene mutations. High sensitivity assays allow the detection of a small subset of patients harbouring true subclonal KRAS mutations. However, DNA changes with mutant allele frequencies <3% detected in formalin-fixed paraffin-embedded samples may be artifactual in a non-negligible fraction of cases. UDG pre-treatment of DNA is mandatory to identify true DNA changes in archival samples and avoid misinterpretation due to artifacts.

Short-term EGFR blockade enhances immune-mediated cytotoxicity of EGFR mutant lung cancer cells: rationale for combination therapies

The epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) erlotinib has been approved for years as a first-line therapy for patients harboring EGFR-sensitizing mutations. With the promising implementation of immunotherapeutic strategies for the treatment of lung cancer, there is a growing interest in developing combinatorial therapies that could utilize immune approaches in the context of conventional or targeted therapies. Tumor cells are known to evade immune attack by multiple strategies, including undergoing phenotypic plasticity via a process designated as the epithelial–mesenchymal transition (EMT). As signaling through EGFR is a major inducer of EMT in epithelial cells, we have investigated the effect of EGFR inhibition with erlotinib on tumor phenotype and susceptibility to immune attack. Our data shows that short-term exposure of tumor cells to low-dose erlotinib modulates tumor plasticity and immune-mediated cytotoxicity in lung cancer cells harboring a sensitizing EGFR mutation, leading to a remarkable enhancement of tumor lysis mediated by innate NK cells and antigen-specific T cells. This effect positively correlated with the ability of short-term EGFR blockade to modulate tumor phenotype towards a more epithelial one, as well as to increase susceptibility to caspase-mediated apoptosis. The effect, however, was lost when erlotinib was utilized for long periods of time in vitro or in vivo, which resulted in gain of mesenchymal features and decreased (rather than increased) tumor lysis in response to immune effector mechanisms. Our data provides rationale for potential combinations of erlotinib and immunotherapies for the treatment of lung carcinomas in the early setting, before the establishment of tumor relapse with long-term EGFR inhibition.

MicroRNA-133b inhibits the migration and invasion of non small cell lung cancer cells via targeting FSCN1

MicroRNA (miR)-133b has been reported to act as a tumor suppressor in multiple types of human cancers, including non small cell lung cancer (NSCLC). However, the underlying mechanism by which miR-133b inhibits NSCLC metastasis remains largely unclear. In the present study, reverse transcription-quantitative polymerase chain reaction and western blotting were used to detect messenger RNA and protein expression. A wound healing assay and transwell assay were used to examine the cell migration and invasion. The expression level of miR-133b was found to be significantly downregulated in NSCLC cell lines compared with normal lung epithelial BEAS-2B cells. Further investigation identified fascin1 (FSCN1) as a direct target of miR-133b in NSCLC cells. The expression of FSCN1 was significantly increased in NSCLC cell lines compared with BEAS-2B cells, and its protein expression was negatively regulated by miR-133b in NSCLC A549 cells. Further investigation showed that the upregulation of miR-133b notably inhibited NSCLC cell migration and invasion, while the overexpression of FSCN1 significantly promoted NSCLC cell migration and invasion. Furthermore, the overexpression of FSCN1 reversed the suppressive effect of miR-133b overexpression on NSCLC cell migration and invasion. Accordingly, the present study suggests that miR-133b inhibits the migration and invasion of NSCLC cells via directly targeting FSCN1, and thus may be used for the treatment of NSCLC metastasis.

Autophagy is not uniformly cytoprotective: a personalized medicine approach for autophagy inhibition as a therapeutic strategy in non-small cell lung cancer

BACKGROUND

Lung cancer is the leading cause of cancer-related death worldwide. In addition to surgical resection, which is considered first-line treatment at early stages of the disease, chemotherapy and radiation are widely used when the disease is advanced. Of multiple responses that may occur in the tumor cells in response to cancer therapy, the functional importance of autophagy remains equivocal; this is likely to restrict current efforts to sensitize this malignancy to chemotherapy and/or radiation by pharmacological interference with the autophagic response.

SCOPE OF REVIEW

In this review, we attempt to summarize the current state of knowledge based on studies that evaluated the function of autophagy in non-small cell lung cancer (NSCLC) cells in response to radiation and the most commonly used chemotherapeutic agents.

MAJOR CONCLUSIONS

In addition to the expected prosurvival function of autophagy, where autophagy inhibition enhances the response to therapy, autophagy appears also to have a "non-cytoprotective" function, where autophagy blockade does not affect cell viability, clonogenicity or tumor volume in response to therapy. In other cases, autophagy may actually mediate drug action via expression of its cytotoxic function.

GENERAL SIGNIFICANCE

These observations emphasize the complexity of autophagy function when examined in different tumor cell lines and in response to different chemotherapeutic agents. A more in-depth understanding of the conditions that promote the unique functions of autophagy is required in order to translate preclinical findings of autophagy inhibition to the clinic for the purpose of improving patient response to chemotherapy and radiation.

ABT-414, an Antibody-Drug Conjugate Targeting a Tumor-Selective EGFR Epitope

Targeting tumor-overexpressed EGFR with an antibody-drug conjugate (ADC) is an attractive therapeutic strategy; however, normal tissue expression represents a significant toxicity risk. The anti-EGFR antibody ABT-806 targets a unique tumor-specific epitope and exhibits minimal reactivity to EGFR in normal tissue, suggesting its suitability for the development of an ADC. We describe the binding properties and preclinical activity of ABT-414, an ABT-806 monomethyl auristatin F conjugate. In vitro, ABT-414 selectively kills tumor cells overexpressing wild-type or mutant forms of EGFR. ABT-414 inhibits the growth of xenograft tumors with high EGFR expression and causes complete regressions and cures in the most sensitive models. Tumor growth inhibition is also observed in tumor models with EGFR mutations, including activating mutations and those with the exon 2-7 deletion [EGFR variant III (EGFRvIII)], commonly found in glioblastoma multiforme. ABT-414 exhibits potent cytotoxicity against glioblastoma multiforme patient-derived xenograft models expressing either wild-type EGFR or EGFRvIII, with sustained regressions and cures observed at clinically relevant doses. ABT-414 also combines with standard-of-care treatment of radiation and temozolomide, providing significant therapeutic benefit in a glioblastoma multiforme xenograft model. On the basis of these results, ABT-414 has advanced to phase I/II clinical trials, and objective responses have been observed in patients with both amplified wild-type and EGFRvIII-expressing tumors. Mol Cancer Ther; 15(4); 661-9. ©2016 AACR.

Inhibition of non-small cell lung cancer (NSCLC) growth by a novel small molecular inhibitor of EGFR

The epidermal growth factor receptor (EGFR) is a therapeutic target (oncotarget) in NSCLC. Using in vitro EGFR kinase activity system, we identified a novel small molecule, WB-308, as an inhibitor of EGFR. WB-308 decreased NSCLC cell proliferation and colony formation, by causing G2/M arrest and apoptosis. Furthermore, WB-308 inhibited the engraft tumor growths in two animal models in vivo (lung orthotopic transplantation model and patient-derived engraft mouse model). WB-308 impaired the phosphorylation of EGFR, AKT, and ERK1/2 protein. WB-308 was less cytotoxic than Gefitinib. Our study suggests that WB-308 is a novel EGFR-TKI and may be considered to substitute for Gefitinib in clinical therapy for NSCLC.

CIMAvax EGF (EGF-P64K) vaccine for the treatment of non-small-cell lung cancer

Epidermal growth factor receptor (EGFR) is overexpressed in many epithelial tumors and its role in the development of non-small-cell lung cancer (NSCLC) is widely documented. CIMAvax-EGF is a therapeutic cancer vaccine composed by recombinant EGF conjugated to a carrier protein and emulsified in Montanide ISA51. Vaccination induces antibodies against self-EGF that block EGF-EGFR interaction and inhibit EGFR phosphorylation. Five clinical trials were conducted to optimize vaccine formulation and schedule. Then, two randomized studies were completed in advanced NSCLC, where CIMAvax-EGF was administered after chemotherapy, as 'switch maintenance'. The vaccine was very well tolerated and the most frequent adverse events consisted of grade 1/2 injection site reactions, fever, headache, vomiting and chills. CIMAvax was immunogenic and EGF concentration was reduced after vaccination. Subjects receiving a minimum of 4 vaccine doses had a significant survival advantage. NSCLC patients with high EGF concentration at baseline had the largest benefit, comparable with best maintenance therapies.