Mediating EGFR-TKI Resistance by VEGF/VEGFR Autocrine Pathway in Non-Small Cell Lung Cancer

Simple Summary

Non-small cell lung cancer (NSCLC) patients acquire resistance to tyrosine kinase inhibitors (TKIs) via EGFR mutations or overexpression of vascular endothelial growth factor receptor-2 (VEGFR-2). In this study, we elucidated the mechanism of EGFR-TKI resistance mediated by VEGF/VEGFR in EGFR-mutated NSCLC cell lines and Erlotinib-resistant cell lines as compared to parental cell lines. Increased expression of VEGF, VEGFR-2, and NP1 was observed in Erlotinib-resistant cell lines. Furthermore, we observed an increased efficacy of Erlotinib in combination with a VEGFR-2 inhibitor in Erlotinib-resistant cell lines. Late-stage NSCLC patients with high expression of VEGFR-2 had shorter survival times compared to patients with low VEGFR-2 expression. These results indicate that VEGFR-2 may play a key role in EGFR-TKI resistance that can be overcome with a combination treatment of Erlotinib and a VEGFR-2 inhibitor, which may serve as an effective treatment option for NSCLC patients with EGFR mutations.

Abstract

NSCLC treatment includes targeting of EGFR with tyrosine kinase inhibitors (TKIs) such as Erlotinib; however, resistance to TKIs is commonly acquired through T790M EGFR mutations or overexpression of vascular endothelial growth factor receptor-2 (VEGFR-2). We investigated the mechanisms of EGFR-TKI resistance in NSCLC cell lines with EGFR mutations or acquired resistance to Erlotinib. These studies showed upregulated gene and protein expression of VEGF, VEGFR-2, and a VEGF co-receptor neuropilin-1 (NP-1) in Erlotinib-resistant (1.4–5.3-fold) and EGFR double-mutant (L858R and T790M; 4.1–8.3-fold) NSCLC cells compared to parental and EGFR single-mutant (L858R) NSCLC cell lines, respectively. Immunofluorescence and FACS analysis revealed increased expression of VEGFR-2 and NP-1 in EGFR-TKI-resistant cell lines compared to TKI-sensitive cell lines. Cell proliferation assays showed that treatment with a VEGFR-2 inhibitor combined with Erlotinib lowered cell survival in EGFR double-mutant NSCLC cells to 9% compared to 72% after treatment with Erlotinib alone. Furthermore, Kaplan–Meier analysis revealed shorter median survival in late-stage NSCLC patients with high vs. low VEGFR-2 expression (14 mos vs. 21 mos). The results indicate that VEGFR-2 may play a key role in EGFR-TKI resistance and that combined treatment of Erlotinib with a VEGFR-2 inhibitor may serve as an effective therapy in NSCLC patients with EGFR mutations.

Abstract 3329: Lung cancer screening initiative and identification of novel blood biomarkers for early detection of lung cancer

In lung cancer, 81% of patients detected are late-stage, since early-stage patients are generally asymptomatic. Winnebago County has a 14% higher mortality rate for lung cancer when compared to the national rate; hence, to improve early detection of lung cancer in the Winnebago County, we implemented low-dose computed tomography (LDCT) screening. Currently, LDCT is used to detect lung cancer at early-stages, and the CDC has proposed new guidelines for early screening of lung cancer in individuals between 55-77 years of age with a 30 pack/year smoking history. Using circulating DNA from lung cancer patients and examining changes in methylation patterns in genes that are expressed in lung cancer patients can be used for early detection. Epidermal growth factor receptor (EGFR) is shown to be expressed in lung cancer patients’ serum in all stages; hence, it can be used as a potential biomarker for early detection. To improve early detection of lung cancer in the Winnebago County, we educated physicians/smokers about LDCT screenings to promote early detection of lung cancer. We evaluated the number of LDCTs performed and recorded the number of lung cancer cases detected in the Winnebago County between June 2015 to October 2017. To explore EGFR as a promising biomarker, plasma was separated from whole blood and collected. Circulating DNA was extracted with the MagMax cell-free circulating kit and bisulfite converted. Identification of percent methylation patterns in the EGFR promoter region in CpG islands was obtained after next generation sequencing (NGS) followed by bioinformatics analysis. In our study, 1,116 LDCT screenings occurred in the Winnebago County. Lung cancer was diagnosed in 19 patients, out of which 11 patients (57.8%) were early-stage patients. We detected 45.4% of patients screened that were present with nodules compared to 24.2% of patients in the National Lung Cancer Screening Trial. We observed that 1.70% of patients referred for LDCT screening were diagnosed with lung cancer, compared to 0.87% of patients in the National Lung Cancer Screening Trial. This may be due to the higher incidence of smoking in Winnebago County (18%) compared to the nation (15.5%). Our screening study had 96.3% false positives, which is comparable (96.4%) to the results obtained in the National Lung Cancer Screening Trial. Using NGS, methylation in the promoter region of EGFR was studied using degenerate EGFR primers. In the promoter region of EGFR, our analysis showed that there are regions of hypermethylation (68-86%) in three CpG islands in sequences at the beginning of the promoter (8-241 bases). However, there was hypomethylation (6-21%) at four CpG island further downstream (375-689 bases from the beginning of the promoter). Currently we are studying the methylation patterns in normal subjects to determine whether these regions which could be used as predictive biomarkers for early detection.

Citation Format: Adijan Kuckovic, Joseph Berei, Shylendra Sreenivasappa, Joseph Ross, Sandra Martell, Connie Vitali, William Schulz, Neelu Puri. Lung cancer screening initiative and identification of novel blood biomarkers for early detection of lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3329.

Oligonucleotides Targeting Telomeres and Telomerase in Cancer

Telomeres and telomerase have become attractive targets for the development of anticancer therapeutics due to their involvement in cancer cell immortality. Currently, several therapeutics have been developed that directly target telomerase and telomeres, such as telomerase inhibitors and G-quadruplex stabilizing ligands. Telomere-specific oligonucleotides that reduce telomerase activity and disrupt telomere architecture are also in development as novel anticancer therapeutics. Specifically, GRN163L and T-oligos have demonstrated promising anticancer activity in multiple cancers types via induction of potent DNA damage responses. Currently, several miRNAs have been implicated in the regulation of telomerase activity and may prove to be valuable targets in the development of novel therapies by reducing expression of telomerase subunits. Targeting miRNAs that are known to increase expression of telomerase subunits may be another strategy to reduce carcinogenesis. This review aims to provide a comprehensive understanding of current oligonucleotide-based anticancer therapies that target telomeres and telomerase. These studies may help design novel therapeutic approaches to overcome the challenges of oligonucleotide therapy in a clinical setting.

Current Molecular-Targeted Therapies in NSCLC and Their Mechanism of Resistance

Lung cancer is treated with many conventional therapies, such as surgery, radiation, and chemotherapy. However, these therapies have multiple undesirable side effects. To bypass the side effects elicited by these conventional treatments, molecularly-targeted therapies are currently in use or under development. Current molecularly-targeted therapies effectively target specific biomarkers, which are commonly overexpressed in lung cancers and can cause increased tumorigenicity. Unfortunately, several molecularly-targeted therapies are associated with initial dramatic responses followed by acquired resistance due to spontaneous mutations or activation of signaling pathways. Acquired resistance to molecularly targeted therapies presents a major clinical challenge in the treatment of lung cancer. Therefore, to address this clinical challenge and to improve lung cancer patient prognosis, we need to understand the mechanism of acquired resistance to current therapies and develop additional novel therapies. This review concentrates on various lung cancer biomarkers, including EGFR, ALK, and BRAF, as well as their potential mechanisms of drug resistance.