Intratumoral Heterogeneity in EGFR-Mutant NSCLC Results in Divergent Resistance Mechanisms in Response to EGFR Tyrosine Kinase Inhibition

DUSP5 regulated by YTHDF1-mediated m6A modification promotes epithelial-mesenchymal transition and EGFR-TKI resistance via the TGF-β/Smad signaling pathway in lung adenocarcinoma

BACKGROUND

Lung adenocarcinoma (LUAD) patients have a dismal survival rate because of cancer metastasis and drug resistance. The study aims to identify the genes that concurrently modulate EMT, metastasis and EGFR-TKI resistance, and to investigate the underlying regulatory mechanisms.

METHODS

Cox regression and Kaplan-Meier analyses were applied to identify prognostic oncogenes in LUAD. Gene set enrichment analysis (GSEA) was used to indicate the biological functions of the gene. Wound-healing and Transwell assays were used to detect migratory and invasive ability. EGFR-TKI sensitivity was evaluated by assessing the proliferation, clonogenic survival and metastatic capability of cancer cells with treatment with gefitinib. Methylated RNA immunoprecipitation (MeRIP) and RNA immunoprecipitation (RIP) analyses established the level of m6A modification present on the target gene and the protein's capability to interact with RNA, respectively. Single-sample gene set enrichment (ssGSEA) algorithm used to investigate levels of immune cell infiltration.

RESULTS

Our study identified dual-specificity phosphatase 5 (DUSP5) as a novel and powerful predictor of adverse outcomes for LUAD by using public datasets. Functional enrichment analysis found that DUSP5 was positively enriched in EMT and transforming growth factor-beta (TGF-β) signaling pathway, a prevailing pathway involved in the induction of EMT. As expected, DUSP5 knockdown suppressed EMT via inhibiting the canonical TGF-β/Smad signaling pathway in in vitro experiments. Consistently, knockdown of DUSP5 was first found to inhibit migratory ability and invasiveness of LUAD cells in in vitro and prevent lung metastasis in in vivo. DUSP5 knockdown re-sensitized gefitinib-resistant LUAD cells to gefitinib, accompanying reversion of EMT progress. In LUAD tissue samples, we found 14 cytosine-phosphate-guanine (CpG) sites of DUSP5 that were negatively associated with DUSP5 gene expression. Importantly, 5'Azacytidine (AZA), an FDA-approved DNA methyltransferase inhibitor, restored DUSP5 expression. Moreover, RIP experiments confirmed that YTH N6-methyladenosine RNA binding protein 1 (YTHDF1), a m6A reader protein, could bind DUSP5 mRNA. YTHDF1 promoted DUSP5 expression and the malignant phenotype of LUAD cells. In addition, the DUSP5-derived genomic model revealed the two clusters with distinguishable immune features and tumor mutational burden (TMB).

CONCLUSIONS

Briefly, our study discovered DUSP5 which was regulated by epigenetic modification, might be a potential therapeutic target, especially in LUAD patients with acquired EGFR-TKI resistance.

A comprehensive single-cell breast tumor atlas defines epithelial and immune heterogeneity and interactions predicting anti-PD-1 therapy response

We present an integrated single-cell RNA sequencing atlas of the primary breast tumor microenvironment (TME) containing 236,363 cells from 119 biopsy samples across eight datasets. In this study, we leverage this resource for multiple analyses of immune and cancer epithelial cell heterogeneity. We define natural killer (NK) cell heterogeneity through six subsets in the breast TME. Because NK cell heterogeneity correlates with epithelial cell heterogeneity, we characterize epithelial cells at the level of single-gene expression, molecular subtype, and 10 categories reflecting intratumoral transcriptional heterogeneity. We develop InteractPrint, which considers how cancer epithelial cell heterogeneity influences cancer-immune interactions. We use T cell InteractPrint to predict response to immune checkpoint inhibition (ICI) in two breast cancer clinical trials testing neoadjuvant anti-PD-1 therapy. T cell InteractPrint was predictive of response in both trials versus PD-L1 (AUC = 0.82, 0.83 vs. 0.50, 0.72). This resource enables additional high-resolution investigations of the breast TME.

Targeting SMAD3 Improves Response to Oxaliplatin in Esophageal Adenocarcinoma Models by Impeding DNA Repair

PURPOSE

TGFβ signaling is implicated in the progression of most cancers, including esophageal adenocarcinoma (EAC). Emerging evidence indicates that TGFβ signaling is a key factor in the development of resistance toward cancer therapy.

EXPERIMENTAL DESIGN

In this study, we developed patient-derived organoids and patient-derived xenograft models of EAC and performed bioinformatics analysis combined with functional genetics to investigate the role of SMAD family member 3 (SMAD3) in EAC resistance to oxaliplatin.

RESULTS

Chemotherapy nonresponding patients showed enrichment of SMAD3 gene expression when compared with responders. In a randomized patient-derived xenograft experiment, SMAD3 inhibition in combination with oxaliplatin effectively diminished tumor burden by impeding DNA repair. SMAD3 interacted directly with protein phosphatase 2A (PP2A), a key regulator of the DNA damage repair protein ataxia telangiectasia mutated (ATM). SMAD3 inhibition diminished ATM phosphorylation by enhancing the binding of PP2A to ATM, causing excessive levels of DNA damage.

CONCLUSIONS

Our results identify SMAD3 as a promising therapeutic target for future combination strategies for the treatment of patients with EAC.

The Impact of Inadequate Exposure to Epidermal Growth Factor Receptor-Tyrosine Kinase Inhibitors on the Development of Resistance in Non-Small-Cell Lung Cancer Cells

Epidermal growth factor receptor (EGFR)-mutant non-small-cell lung cancer (NSCLC) patients treated with EGFR-tyrosine kinase inhibitors (TKIs) inevitably develop resistance through several biological mechanisms. However, little is known on the molecular mechanisms underlying acquired resistance to suboptimal EGFR-TKI doses, due to pharmacodynamics leading to inadequate drug exposure. To evaluate the effects of suboptimal EGFR-TKI exposure on resistance in NSCLC, we obtained HCC827 and PC9 cell lines resistant to suboptimal fixed and intermittent doses of gefitinib and compared them to cells exposed to higher doses of the drug. We analyzed the differences in terms of EGFR signaling activation and the expression of epithelial-mesenchymal transition (EMT) markers, whole transcriptomes byRNA sequencing, and cell motility. We observed that the exposure to low doses of gefitinib more frequently induced a partial EMT associated with an induced migratory ability, and an enhanced transcription of cancer stem cell markers, particularly in the HCC827 gefitinib-resistant cells. Finally, the HCC827 gefitinib-resistant cells showed increased secretion of the EMT inducer transforming growth factor (TGF)-β1, whose inhibition was able to partially restore gefitinib sensitivity. These data provide evidence that different levels of exposure to EGFR-TKIs in tumor masses might promote different mechanisms of acquired resistance.

Joint analysis of mutational and transcriptional landscapes in human cancer reveals key perturbations during cancer evolution

BACKGROUND

Tumors are able to acquire new capabilities, including traits such as drug resistance and metastasis that are associated with unfavorable clinical outcomes. Single-cell technologies have made it possible to study both mutational and transcriptomic profiles, but as most studies have been conducted on model systems, little is known about cancer evolution in human patients. Hence, a better understanding of cancer evolution could have important implications for treatment strategies.

RESULTS

Here, we analyze cancer evolution and clonal selection by jointly considering mutational and transcriptomic profiles of single cells acquired from tumor biopsies from 49 lung cancer samples and 51 samples with chronic myeloid leukemia. Comparing the two profiles, we find that each clone is associated with a preferred transcriptional state. For metastasis and drug resistance, we find that the number of mutations affecting related genes increases as the clone evolves, while changes in gene expression profiles are limited. Surprisingly, we find that mutations affecting ligand-receptor interactions with the tumor microenvironment frequently emerge as clones acquire drug resistance.

CONCLUSIONS

Our results show that lung cancer and chronic myeloid leukemia maintain a high clonal and transcriptional diversity, and we find little evidence in favor of clonal sweeps. This suggests that for these cancers selection based solely on growth rate is unlikely to be the dominating driving force during cancer evolution.

The cell line models to study tyrosine kinase inhibitors in non-small cell lung cancer with mutations in the epidermal growth factor receptor: A scoping review

Non-Small Cell Lung Cancer (NSCLC) represents ∼85% of all lung cancers and ∼15-20% of them are characterized by mutations affecting the Epidermal Growth Factor Receptor (EGFR). For several years now, a class of tyrosine kinase inhibitors was developed, targeting sensitive mutations affecting the EGFR (EGFR-TKIs). To date, the main burden of the TKIs employment is due to the onset of resistance mutations. This scoping review aims to resume the current situation about the cell line models employed for the in vitro evaluation of resistance mechanisms induced by EGFR-TKIs in oncogene-addicted NSCLC. Adenocarcinoma results the most studied NSCLC histotype with the H1650, H1975, HCC827 and PC9 mutated cell lines, while Gefitinib and Osimertinib the most investigated inhibitors. Overall, data collected frame the current advancement of this topic, showing a plethora of approaches pursued to overcome the TKIs resistance, from RNA-mediated strategies to the innovative combination therapies.

Multifaceted TGF-β signaling, a master regulator: From bench-to-bedside, intricacies, and complexities

Physiological embryogenesis and adult tissue homeostasis are regulated by transforming growth factor-β (TGF-β), an evolutionarily conserved family of secreted polypeptide factors, acting in an autocrine and paracrine manner. The role of TGF-β in inflammation, fibrosis, and cancer is complex and sometimes even contradictory, exhibiting either inhibitory or promoting effects depending on the stage of the disease. Under pathological conditions, especially fibrosis and cancer, overexpressed TGF-β causes extracellular matrix deposition, epithelial-mesenchymal transition, cancer-associated fibroblast formation, and/or angiogenesis. In this review article, we have tried to dive deep into the mechanism of action of TGF-β in inflammation, fibrosis, and carcinogenesis. As TGF-β and its downstream signaling mechanism are implicated in fibrosis and carcinogenesis blocking this signaling mechanism appears to be a promising avenue. However, targeting TGF-β carries substantial risk as this pathway is implicated in multiple homeostatic processes and is also known to have tumor-suppressor functions. There is a need for careful dosing of TGF-β drugs for therapeutic use and patient selection.

Deep learning untangles the resistance mechanism of p53 reactivator in lung cancer cells

Tumor suppressor p53 plays a pivotal role in suppressing cancer, so various drugs has been suggested to upregulate its function. However, drug resistance is still the biggest hurdle to be overcome. To address this, we developed a deep learning model called AnoDAN (anomalous gene detection using generative adversarial networks and graph neural networks for overcoming drug resistance) that unravels the hidden resistance mechanisms and identifies a combinatorial target to overcome the resistance. Our findings reveal that the TGF-β signaling pathway, alongside the p53 signaling pathway, mediates the resistance, with THBS1 serving as a core regulatory target in both pathways. Experimental validation in lung cancer cells confirms the effects of THBS1 on responsiveness to a p53 reactivator. We further discovered the positive feedback loop between THBS1 and the TGF-β pathway as the main source of resistance. This study enhances our understanding of p53 regulation and offers insights into overcoming drug resistance.

Cisplatin-induced activation of TGF-β signaling contributes to drug resistance

Growing evidence suggests an association between epithelial-mesenchymal transition (EMT), a hallmark of tumor malignancy, and chemoresistance to a number of anti-cancer drugs. However, the mechanism of EMT induction in the process of acquiring anti-cancer drug resistance remains unclear. To address this issue, we obtained a number of cisplatin-resistant clones from LoVo cells and found that almost all of them lost cell-cell contacts. In these clones, the epithelial marker E-cadherin was downregulated, whereas the mesenchymal marker N-cadherin was upregulated. Moreover, the expression of EMT-related transcription factors, including Slug, was elevated. On the other hand, the upregulation of other mesenchymal marker Vimentin was weak, suggesting that the mesenchymal-like phenotypic changes occurred in these cisplatin-resistant clones. These mesenchymal-like features of cisplatin-resistant clones were partially reversed to parental epithelial-like features by treatment with transforming growth factor-β (TGF-β) receptor kinase inhibitors, indicating that TGF-β signaling is involved in cisplatin-induced the mesenchymal-like phenotypic changes. Moreover, cisplatin was observed to enhance the secretion of TGF-β into the culture media without influencing TGF-β gene transcription. These results suggest that cisplatin may induce the mesenchymal-like phenotypic changes by enhancing TGF-β secretion, ultimately resulting in drug resistance.

CDK4/6 signaling attenuates the effect of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors in EGFR-mutant non-small cell lung cancer

Background

Epidermal growth factor receptor (EGFR) mutations, such as exon 19 deletion and exon 21 L858R, are driver oncogenes of non-small cell lung cancer (NSCLC), with EGFR tyrosine kinase inhibitors (TKIs) being effective against EGFR-mutant NSCLC. However, the efficacy of EGFR-TKIs is transient and eventually leads to acquired resistance. Herein, we focused on the significance of cell cycle factors as a mechanism to attenuate the effect of EGFR-TKIs in EGFR-mutant NSCLC before the emergence of acquired resistance.

Methods

Using several EGFR-mutant cell lines, we investigated the significance of cell cycle factors to attenuate the effect of EGFR-TKIs in EGFR-mutant NSCLC.

Results

In several EGFR-mutant cell lines, certain cancer cells continued to proliferate without EGFR signaling, and the cell cycle regulator retinoblastoma protein (RB) was not completely dephosphorylated. Further inhibition of phosphorylated RB with cyclin-dependent kinase (CDK) 4/6 inhibitors, combined with the EGFR-TKI osimertinib, enhanced G0/G1 cell cycle accumulation and growth inhibition of the EGFR-mutant NSCLC in both in vitro and in vivo models. Furthermore, residual RB phosphorylation without EGFR signaling was maintained by extracellular signal-regulated kinase (ERK) signaling, and the ERK inhibition pathway showed further RB dephosphorylation.

Conclusions

Our study demonstrated that the CDK4/6-RB signal axis, maintained by the MAPK pathway, attenuates the efficacy of EGFR-TKIs in EGFR-mutant NSCLC, and targeting CDK4/6 enhances this efficacy. Thus, combining CDK4/6 inhibitors and EGFR-TKI could be a novel treatment strategy for TKI-naïve EGFR-mutant NSCLC.

Effectiveness of Stereotactic Ablative Radiotherapy for Systemic Therapy Respondents with Inoperable Pulmonary Oligometastases and Oligoprogression

Stereotactic ablative radiotherapy (SABR) may improve survival in patients with inoperable pulmonary oligometastases. However, the impact of pulmonary oligometastatic status after systemic therapy on SABR outcomes remains unclear. Hence, we investigated the outcomes of SABR in 45 patients with 77 lung tumors and the prognostic value of pulmonary oligoprogression. Eligibility criteria were pulmonary oligometastases (defined as ≤5 metastatic lung tumors), controlled extrapulmonary disease (EPD) after front-line systemic therapy, SABR as primary local treatment for inoperable pulmonary metastases, and consecutive imaging follow-up. Oligometastatic lung tumor was classified into controlled or oligoprogressive status. Overall survival (OS), in-field progression-free survival (IFPFS), out-field progression-free survival (OFPFS), and prognostic variables were evaluated. With 21.8 months median follow-up, the median OS, IFPFS, and OFPFS were 28.3, not reached, and 6.5 months, respectively. Two-year OS, IFPFS, and OFPFS rates were 56.0%, 74.2%, and 17.3%, respectively. Oligoprogressive status (p = 0.003), disease-free interval < 24 months (p = 0.041), and biologically effective dose (BED₁₀) < 100 Gy (p = 0.006) were independently associated with inferior OS. BED₁₀ ≥ 100 Gy (p = 0.029) was independently correlated with longer IFPFS. Oligoprogressive status (p = 0.017) and EPD (p = 0.019) were significantly associated with inferior OFPFS. Grade ≥ 2 radiation pneumonitis occurred in four (8.9%) patients. Conclusively, SABR with BED₁₀ ≥ 100 Gy could provide substantial in-field tumor control and longer OS for systemic therapy respondents with inoperable pulmonary oligometastases. Oligoprogressive lung tumors exhibited a higher risk of out-field treatment failure and shorter OS. Hence, systemic therapy should be tailored for patients with oligoprogression to reduce the risk of out-field treatment failure. However, in the absence of effective systemic therapy, SABR is a reasonable alternative to reduce resistant tumor burden.

Ultrasound-mediated mesoporous silica nanoparticles loaded with PDLIM5 siRNA inhibit gefitinib resistance in NSCLC cells by attenuating EMT

Epidermal growth factor receptor tyrosine kinase inhibitor (EGFR TKIs) was one of the main drugs in the treatment of non-small cell lung cancer (NSCLC). Previous studies had demonstrated that PDZ and LIM Domain 5 (PDLIM5) played an important role in EGFR TKIs resistance. However, there was no feasible method to eliminate EGFR TKIs resistance by suppressing this gene. Here, we formulated a novel mesoporous silica-loaded PDLIM5 siRNA (Small interfering RNA) nanoplatforms. The results have shown that PDLIM5 siRNA could be effectively bound to the nanoplatforms and had good biocompatibility. Further exploration suggested that the nano-platform combined with ultrasonic irradiation could be very effective for siRNA delivery and ultrasound imaging. Moreover, Epithelial-mesenchymal transformation (EMT) changes occurred in PC-9 Gefitinib resistance (PC-9/GR) cells during the development of drug resistance. When PDLIM5 siRNA entered PC-9/GR cells, the sensitivity of drug-resistant cells to gefitinib could be restored through the transforming growth factor-β (TGF-β)/EMT pathway. Therefore, PDLIM5 may be an important reason for the resistance of NSCLC cells to gefitinib, and this nanoplatform may become a novel treatment for EGFR TKIs resistance in NSCLC patients.

MET Amplification as a Resistance Driver to TKI Therapies in Lung Cancer: Clinical Challenges and Opportunities

Targeted therapy has emerged as an important pillar for the standard of care in oncogene-driven non-small cell lung cancer (NSCLC), which significantly improved outcomes of patients whose tumors harbor oncogenic driver mutations. However, tumors eventually develop resistance to targeted drugs, and mechanisms of resistance can be diverse. MET amplification has been proven to be a driver of resistance to tyrosine kinase inhibitor (TKI)-treated advanced NSCLC with its activation of EGFR, ALK, RET, and ROS-1 alterations. The combined therapy of MET-TKIs and EGFR-TKIs has shown outstanding clinical efficacy in EGFR-mutated NSCLC with secondary MET amplification-mediated resistance in a series of clinical trials. In this review, we aimed to clarify the underlying mechanisms of MET amplification-mediated resistance to tyrosine kinase inhibitors, discuss the ways and challenges in the detection and diagnosis of MET amplifications in patients with metastatic NSCLC, and summarize the recently published clinical data as well as ongoing trials of new combination strategies to overcome MET amplification-mediated TKI resistance.

Protein tyrosine kinase inhibitor resistance in malignant tumors: molecular mechanisms and future perspective

Protein tyrosine kinases (PTKs) are a class of proteins with tyrosine kinase activity that phosphorylate tyrosine residues of critical molecules in signaling pathways. Their basal function is essential for maintaining normal cell growth and differentiation. However, aberrant activation of PTKs caused by various factors can deviate cell function from the expected trajectory to an abnormal growth state, leading to carcinogenesis. Inhibiting the aberrant PTK function could inhibit tumor growth. Therefore, tyrosine kinase inhibitors (TKIs), target-specific inhibitors of PTKs, have been used in treating malignant tumors and play a significant role in targeted therapy of cancer. Currently, drug resistance is the main reason for limiting TKIs efficacy of cancer. The increasing studies indicated that tumor microenvironment, cell death resistance, tumor metabolism, epigenetic modification and abnormal metabolism of TKIs were deeply involved in tumor development and TKI resistance, besides the abnormal activation of PTK-related signaling pathways involved in gene mutations. Accordingly, it is of great significance to study the underlying mechanisms of TKIs resistance and find solutions to reverse TKIs resistance for improving TKIs efficacy of cancer. Herein, we reviewed the drug resistance mechanisms of TKIs and the potential approaches to overcome TKI resistance, aiming to provide a theoretical basis for improving the efficacy of TKIs.

The current state of the art and future trends in RAS-targeted cancer therapies

Despite being the most frequently altered oncogenic protein in solid tumours, KRAS has historically been considered ‘undruggable’ owing to a lack of pharmacologically targetable pockets within the mutant isoforms. However, improvements in drug design have culminated in the development of inhibitors that are selective for mutant KRAS in its active or inactive state. Some of these inhibitors have proven efficacy in patients with KRAS^G12C-mutant cancers and have become practice changing. The excitement associated with these advances has been tempered by drug resistance, which limits the depth and/or duration of responses to these agents. Improvements in our understanding of RAS signalling in cancer cells and in the tumour microenvironment suggest the potential for several novel combination therapies, which are now being explored in clinical trials. Herein, we provide an overview of the RAS pathway and review the development and current status of therapeutic strategies for targeting oncogenic RAS, as well as their potential to improve outcomes in patients with RAS-mutant malignancies. We then discuss challenges presented by resistance mechanisms and strategies by which they could potentially be overcome.

The RAS oncogenes are among the most common drivers of tumour development and progression but have historically been considered undruggable. The development of direct KRAS inhibitors has changed this paradigm, although currently clinical use of these novel therapeutics is limited to a select subset of patients, and intrinsic or acquired resistance presents an inevitable challenge to cure. Herein, the authors provide an overview of the RAS pathway in cancer and review the ongoing efforts to develop effective therapeutic strategies for RAS-mutant cancers. They also discuss the current understanding of mechanisms of resistance to direct KRAS inhibitors and strategies by which they might be overcome.

Owing to intrinsic and extrinsic factors, KRAS and other RAS isoforms have until recently been impervious to targeting with small-molecule inhibitors.

Inhibitors of the KRAS^G12C variant constitute a potential breakthrough in the treatment of many cancer types, particularly non-small-cell lung cancer, for which such an agent has been approved by the FDA.

Several forms of resistance to KRAS inhibitors have been defined, including primary, adaptive and acquired resistance; these resistance mechanisms are being targeted in studies that combine KRAS inhibitors with inhibitors of horizontal or vertical signalling pathways.

Mutant KRAS has important effects on the tumour microenvironment, including the immunological milieu; these effects must be considered to fully understand resistance to KRAS inhibitors and when designing novel treatment strategies.

Non-small cell lung carcinoma spheroid models in agarose microwells for drug response studies

There is a growing interest in developing personalized treatment strategies for each cancer patient, especially those with non-small cell lung carcinoma (NSCLC) which annually accounts for the majority of cancer related deaths in the US. Yet identifying the optimal NSCLC treatment strategy for each cancer patient is critical due to a multitude of mutations, some of which develop following initial therapy and can result in drug resistance. A key difficulty in developing personalized therapies in NSCLC is the lack of clinically relevant assay systems that are suitable to evaluate drug sensitivity using a minuscule amount of patient-derived material available following biopsies. Herein we leverage 3D printing to demonstrate a platform based on miniature microwells in agarose to culture cancer cell spheroids. The agarose wells were shaped by 3D printing molds with 1000 microwells with a U-shaped bottom. Three NSCLC cell lines (HCC4006, H1975 and A549) were used to demonstrate size uniformity, spheroid viability, biomarker expressions and drug response in 3D agarose microwells. Results show that our approach yielded spheroids of uniform size (coefficient of variation <22%) and high viability (>83% after 1 week-culture). Studies using epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKIs) drugs gefitinib and osimertinib showed clinically relevant responses. Based on the physical features, cell phenotypes, and responses to therapy of our spheroid models, we conclude that our platform is suitable for in vitro culture and drug evaluation, especially in cases when tumor sample is limited.

Impact of stereotactic body radiotherapy (SBRT) in oligoprogressive metastatic disease

PURPOSE

There is increasing interest in using stereotactic body radiation therapy (SBRT) in areas of oligoprogressive metastatic disease (OPD). Our main objective was to investigate the impact of SBRT on overall survival (OS) and the incidence of systemic therapy treatment switches in this population.

METHODS

A retrospective institutional review of patients treated with SBRT for OPD was performed. Patients were included if they received SBRT for 1-3 discrete progressing metastases, using a dose of at least 5 Gy per fraction. The study aimed to calculate progression-free survival (PFS), overall survival (OS), local control (LC), and incidence of treatment switch (TS). PFS and OS were calculated using the Kaplan-Meier methodology, while LC and TS were determined using cumulative incidence.

RESULTS

Eighty-one patients with a total of 118 lesions were treated with SBRT from July 2014 to November 2020. The Median SBRT dose was 40 (18-60) Gy in 5 (2-8) fractions. Patients had primarily kidney, lung, or breast cancer. Most patients were treated with a tyrosine kinase inhibitor (TKI) (30.9%) or chemotherapy (29.6%) before OPD. The median follow-up post-SBRT was 14 months. Median OS and PFS were 25.1 (95% CI 11.2-39.1) months and 7.8 (95% CI 4.6-10.9) months, respectively. The cumulative incidence of local progression of treated lesions was 5% at 1 year and 7.3% at 2 years. Sixty patients progressed after SBRT and 17 underwent additional SBRT. Thirty-eight patients (47%) changed systemic therapy following SBRT; the cumulative incidence of TS was 28.5% at 6 months, 37.4% at 1 year, and 43.9% at 2 years.

CONCLUSIONS

SBRT effectively controls locally progressing lesions but distant progression still occurs frequently. A sizeable number of patients can be salvaged by further SBRT or have minimally progressing diseases that may not warrant an immediate initiation/switch in systemic therapy. Further prospective studies are needed to validate this benefit.

Early On-Treatment Prediction of the Mechanisms of Acquired Resistance to EGFR Tyrosine Kinase Inhibitors

BACKGROUND

Prediction of resistance mechanisms for epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) remains challenging. Thus, we investigated whether resistant cancer cells that expand shortly after EGFR-TKI treatment would eventually cause the resistant phenotype.

METHODS

We generated two EGFR-mutant lung cancer cell lines resistant to gefitinib (PC9GR and HCC827GR). The parent cell lines were exposed to short-term treatment with gefitinib or paclitaxel and then were assessed for EGFR T790M mutation and C-MET expression. These experiments were repeated in vivo and in clinically relevant patient-derived cell (PDC) models. For validation in clinical cases, we measured these gene alterations in plasma circulating tumor DNA (ctDNA) before and 8 weeks after starting EGFR-TKIs in four patients with EGFR-mutant lung cancer.

RESULTS

T790M mutation was only detected in the PC9GR cells, whereas C-MET amplification was detected in the HCC827GR cells. The T790M mutation level significantly increased in PC9 cells after short-term treatment with gefitinib but not in the paclitaxel. C-MET mRNA expression was only significantly increased in gefitinib-treated HCC827 cells. We confirmed that the C-MET copy number in HCC827 cells that survived after short-term gefitinib treatment was significantly higher than that in dead HCC827 cells. These findings were reproduced in the in vivo and PDC models. An early on-treatment increase in the plasma ctDNA level of these gene alterations was correlated with the corresponding resistance mechanism to EGFR-TKIs, a finding that was confirmed in post-treatment tumor tissues.

CONCLUSIONS

Early on-treatment kinetics in resistance-related gene alterations may predict the final mechanism of EGFR-TKI resistance.

Heterogeneity among tumors with acquired resistance to EGFR tyrosine kinase inhibitors harboring EGFR ‐T790M mutation in non‐small cell lung cancer cells

EGFR‐T790M mutation is a major mechanism underlying acquired resistance to first‐ and second‐generation EGFR tyrosine kinase inhibitors (EGFR‐TKIs) in lung cancer with mutated EGFR. However, differences in the biological characteristics of T790M tumors based on treatment regimens with each generation of EGFR‐TKI are not fully understood. We established cell lines with acquired resistance harboring EGFR‐T790M mutation derived from xenograft tumors treated with each generation of EGFR‐TKI and examined their biological characteristics with respect to third‐generation EGFR‐TKI osimertinib sensitivity. Second‐generation EGFR‐TKI dacomitinib‐resistant cells with T790M‐exhibited higher sensitivity to osimertinib than first‐generation EGFR‐TKI gefitinib‐resistant cells with T790M via inhibition of AKT and ERK signaling and promotion of apoptosis. Furthermore, gefitinib‐resistant cells showed enhanced intratumor heterogeneity accompanied by genomic instability and activation of alternative resistance mechanisms compared with dacomitinib‐resistant cells; this suggests that the maintenance of EGFR dependency after acquiring resistance might depend on the type of EGFR‐TKI. Our results demonstrate that the progression of tumor heterogeneity via both genetic and non‐genetic mechanisms might affect osimertinib sensitivity in tumors with acquired resistance harboring EGFR‐T790M mutation.

Use of Circulating Tumour DNA (ctDNA) for Measurement of Therapy Predictive Biomarkers in Patients with Cancer

Biomarkers that predict likely response or resistance to specific therapies are critical in personalising treatment for cancer patients. Such biomarkers are now available for an increasing number of anti-cancer therapies, especially targeted therapy and immunotherapy. The gold-standard method for determining predictive biomarkers requires tumour tissue. Obtaining tissue, however, is not always possible and even if possible, the amount or quality of tissue obtained may be inadequate for biomarker analysis. Tumour DNA, however, can be released into the bloodstream, giving rise to what is referred to as circulating tumour DNA (ctDNA). In contrast to tissue, blood can be obtained from effectively all patients in a minimally invasive and safe manner. Other advantages of blood over tissue for biomarker testing include a shorter turn-around time and an ability to perform serial measurements. Furthermore, blood should provide a more complete profile of mutations present in heterogeneous tumours than a single-needle tissue biopsy. A limitation of blood vis-à-vis tissue, however, is lower sensitivity and, thus, the possibility of missing an actionable mutation. Despite this limitation, blood-based predictive biomarkers, such as mutant EGFR for predicting response to EGFR tyrosine kinase inhibitors in advanced non-small-cell lung cancer and mutant PIK3CA for predicting response to alpelisib in combination with fulvestrant in advanced breast cancer, may be used when tissue is unavailable. Although tissue remains the gold standard for detecting predictive biomarkers, it is likely that several further blood-based assays will soon be validated and used when tissue is unavailable or unsuitable for analysis.

TGF-β Signaling and Resistance to Cancer Therapy

The transforming growth factor β (TGF-β) pathway, which is well studied for its ability to inhibit cell proliferation in early stages of tumorigenesis while promoting epithelial-mesenchymal transition and invasion in advanced cancer, is considered to act as a double-edged sword in cancer. Multiple inhibitors have been developed to target TGF-β signaling, but results from clinical trials were inconsistent, suggesting that the functions of TGF-β in human cancers are not yet fully explored. Multiple drug resistance is a major challenge in cancer therapy; emerging evidence indicates that TGF-β signaling may be a key factor in cancer resistance to chemotherapy, targeted therapy and immunotherapy. Finally, combining anti-TGF-β therapy with other cancer therapy is an attractive venue to be explored for the treatment of therapy-resistant cancer.

First-line osimertinib in patients with epidermal growth factor receptor-mutant non-small-cell lung cancer and with a coexisting low allelic fraction of Thr790Met

AIM OF THE STUDY

The AZENT (NCT02841579) study aimed to assess the efficacy and safety of first-line osimertinib in patients with epidermal growth factor receptor(EGFR)mutation-positive advanced non-small-cell lung cancer (NSCLC) and with a coexisting low allelic fraction of Thr790Met.

METHODS

In this multicentre, single-arm, open-label, phase IIa study, patients with locally advanced or metastatic NSCLC harbouring centrally confirmedEGFR Thr790Met mutation received 80 mg osimertinib daily. The primary end-point was objective response rate (ORR). The secondary end-points included disease control rate (DCR), progression-free survival (PFS), overall survival (OS) and safety. Efficacy was assessed as per Response Evaluation Criteria in Solid Tumours, version 1.1. Blood samples collected at baseline, end of week 2 and disease progression were analysed using next-generation sequencing. As osimertinib was approved as a first-line therapy during the trial, this led to early termination of phase II; thus, analysis is considered exploratory.

RESULTS

Twenty-two patients were enrolled and received osimertinib. All 22 patients were included in the efficacy and safety analysis. At the data cutoff, 10 (50%) patients remained on treatment. The median duration of follow-up was 24.4 months (interquartile range 12.9 to 26.0). The ORR was 77.3% (17/22 [95% confidence interval {CI} 54.6 to 89.3]). The DCR was 86.4% (19/22, [95% CI 65.1 to 97.1]). The median PFS was 23.1 months (95% CI 14.1 to NE). The median OS was 28·4 months (95% CI 25.6 to NE).

CONCLUSION

Despite early study termination, osimertinib first-line therapy yields an overall PFS of 23.1 months in EGFR-mutant patients harbouring a coexisting low allelic fraction of EGFR Thr790Met mutation.

Tumor immune microenvironment in epidermal growth factor receptor-mutated non-small cell lung cancer before and after epidermal growth factor receptor tyrosine kinase inhibitor treatment: a narrative review

Objective

To review and summarize the characteristics of the tumor immune microenvironment (TIME) in EGFR-mutated non-small cell lung cancer (NSCLC) after EGFR-TKI treatment and its role in TKI resistance.

Background

Lung cancer is one of the most commonly diagnosed cancer and the leading cause of death from cancer in both men and women around the world. Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) are considered a first-line treatment for EGFR-mutated NSCLC. However, almost all patients eventually develop acquired resistance to EGFR-TKIs, with a median progression-free survival (PFS) of 9–14 months. As immunotherapy has developed, it has become apparent that interactions between the TIME and tumor cells also affect EGFR-TKI treatment. The TIME comprises a variety of components but previous studies of the TIME following EGFR-TKI therapy of NSCLC are inconsistent. Here, we reviewed the characteristics of the TIME in NSCLC after EGFR-TKI treatment and its role in TKI resistance.

Methods

PubMed, Embase, and Web of Science were searched to July 1, 2021 with the following key words: “NSCLC”, “EGFR”, and “immunotherapy”.

Conclusions

The TIME of EGFR-mutated NSCLC is different from that of non-mutated NSCLC, an explanation for EGFR-mutated NSCLC displaying a poor response to ICIs. The TIME of EGFR-mutated NSCLC also changes during treatment with EGFR-TKIs. The TIME in EGFR-TKI-resistant lung cancer can be summarized as follows: (I) compared with EGFR-TKI-sensitive tumors, EGFR-TKI-resistant tumors have a greater number of immunosuppressive cells and fewer immune-activated cells, while the tumor microenvironment is in an immunosuppressive state; (II) tumor cells and immunosuppressive cells secrete multiple negative immune regulatory factors, inhibit the recognition and presentation of tumor antigens and the antitumor effect of immune cells, resulting in immune escape; 3.EGFR-TKI-resistant tumors promote EMT. These three characteristics interact, resulting in a regulatory signaling network, which together leads to EGFR-TKI resistance.

ADNP prompts the cisplatin-resistance of bladder cancer via TGF-β-mediated epithelial-mesenchymal transition (EMT) pathway

Activity-dependent neuroprotective protein (ADNP) is vital for embryonic development and brain formation. Besides, the upregulated expression of ADNP enhances tumorigenesis in some human tumors like bladder cancer (BC). However, the potential roles of ADNP in drug resistance and the related mechanisms in BC is unknown. We performed this study to elucidate the influence of ADNP in the chemoresistance of BC and tried to explore the underlying molecular mechanism. The expressions of ADNP in BC from progression and non-progression patient specimens were measured by quantitative real-time PCR (qRT-PCR) and immunohistochemistry (IHC). In vitro experiments including colony formation, cell counting kit-8 (CCK-8), wound healing, and in vivo tumorigenesis assay were performed to explore the effects of ADNP on chemoresistance of BC. The impacts of ADNP on TGF-β/Smad signaling pathways were explored by western blot. Our results showed that the expression of ADNP mRNA and protein were significantly upregulated in BC tissues of the patients who suffered tumor-progression via RT-PCR and western blot. Cox regression survival analysis revealed that patients with high ADNP expression closely linked to shorter tumor-free survival. ADNP downregulation in BC showed more sensitive to cisplatin in vivo, while ADNP overexpression showed the opposite results. Additionally, we confirmed that ADNP promoted cell migration and EMT, thereby inducing cisplatin resistance, which may be related to TGF-β / Smad signaling pathway.

Exosome-derived miR-210 involved in resistance to osimertinib and epithelial-mesenchymal transition in EGFR mutant non-small cell lung cancer cells

Background

Osimertinib is a third‐generation epidermal growth factor receptor‐tyrosine kinase inhibitor (EGFR‐TKI) approved for the treatment of patients with EGFR‐mutant non‐small cell lung cancer (NSCLC). However, the mechanisms of acquired drug resistance to osimertinib have not as yet been clarified. Exosomes and microRNAs (miRNAs) are involved in carcinogenesis and drug resistance in human cancers.

Methods

We used previously established osimertinib‐resistant HCC827 (HCC827‐OR) and PC‐9 (PC‐9‐OR) cells. We evaluated the profiles of exosomal miRNA associated with resistance to osimertinib in EGFR‐mutant NSCLC cells.

Results

Epithelial–mesenchymal transition (EMT) phenomenon was observed in HCC827‐OR and PC‐9‐OR cells. Microarray and quantitative reverse transcription‐polymerase chain reaction analysis revealed that miR‐210‐3p was co‐upregulated in exosomes isolated from HCC827‐OR and PC‐9‐OR cells compared with those isolated from parental HCC827 and PC‐9 cells. HCC827‐OR cell‐derived exosomes induced EMT changes and resistance to osimertinib in HCC827 cells. Subsequently, the induction of miR‐210‐3p directly promoted the EMT phenomenon and resistance to osimertinib in HCC827 cells.

Conclusions

Exosomal miR‐210‐3p may play a crucial role in resistance to osimertinib in the tumor microenvironment of EGFR‐mutant NSCLC.

Local Ablative Therapies for Oligometastatic and Oligoprogressive Non-Small Cell Lung Cancer

More than half of all patients with non-small cell lung cancer (NSCLC) have metastatic disease at the time of diagnosis. A subset of these patients has oligometastatic disease, which exists in an intermediary state between locoregional and disseminated metastatic disease. In addition, some metastatic patients on systemic therapy may have limited disease progression, or oligoprogression. Historically, treatment of metastatic NSCLC was palliative in nature, with little expectation of long-term survival. However, an accumulation of evidence over the past 3 decades now demonstrates that local ablative therapy to sites of limited metastases or progression can improve patient outcomes for this complex disease. This review examines the evidence behind local ablative therapy in oligometastatic and oligoprogressive NSCLC, with a focus on surgery, stereotactic radiotherapy, and radiofrequency ablation.

Long intergenic non-coding RNA (lincRNA)-01317 suppresses human gastric cancer growth by inhibiting migration and invasion of cancer cells

Long intergenic noncoding RNAs (lincRNAs) are strongly associated with several kinds of cancer, including gastric cancer. Here, we found significantly decreased lincRNA-01317 levels in cancer tissue compared with paracancer tissue of patients with gastric cancer, and lincRNA-01317 expression levels positively correlated with clinical survival rate. Furthermore, using a gastric cancer cell line and a xenograft mouse model, we found that transfection of a gastric cancer cell line with lincRNA-01317 significantly inhibited the proliferation, migration, and invasion of gastric cancer cells. Finally, we demonstrated that lincRNA-01317 may target KCNQ1, as KCNQ1 was downregulated after transfection of cells with lincRNA-01317. This study aimed to assess lincRNA-01317 as a potential therapeutic target to treat cancers.

Cancer Stem Cells-Key Players in Tumor Relapse

Tumor relapse and treatment failure are unfortunately common events for cancer patients, thus often rendering cancer an uncurable disease. Cancer stem cells (CSCs) are a subset of cancer cells endowed with tumor-initiating and self-renewal capacity, as well as with high adaptive abilities. Altogether, these features contribute to CSC survival after one or multiple therapeutic approaches, thus leading to treatment failure and tumor progression/relapse. Thus, elucidating the molecular mechanisms associated with stemness-driven resistance is crucial for the development of more effective drugs and durable responses. This review will highlight the mechanisms exploited by CSCs to overcome different therapeutic strategies, from chemo- and radiotherapies to targeted therapies and immunotherapies, shedding light on their plasticity as an insidious trait responsible for their adaptation/escape. Finally, novel CSC-specific approaches will be described, providing evidence of their preclinical and clinical applications.

Development and Validation of a Machine Learning Model to Explore Tyrosine Kinase Inhibitor Response in Patients With Stage IV EGFR Variant-Positive Non-Small Cell Lung Cancer

IMPORTANCE

An end-to-end efficacy evaluation approach for identifying progression risk after epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitor (TKI) therapy in patients with stage IV EGFR variant-positive non-small cell lung cancer (NSCLC) is lacking.

OBJECTIVE

To propose a clinically applicable large-scale bidirectional generative adversarial network for predicting the efficacy of EGFR-TKI therapy in patients with NSCLC.

DESIGN, SETTING, AND PARTICIPANTS

This diagnostic/prognostic study enrolled 465 patients from January 1, 2010, to August 1, 2017, with follow-up from February 1, 2010, to June 1, 2020. A deep learning (DL) semantic signature to predict progression-free survival (PFS) was constructed in the training cohort, validated in 2 external validation and 2 control cohorts, and compared with the radiomics signature.

EXPOSURES

An end-to-end bidirectional generative adversarial network framework was designed to predict the progression risk in patients with NSCLC.

MAIN OUTCOMES AND MEASURES

The primary end point was PFS, considering the time from the initiation of therapy to the date of recurrence, confirmed disease progression, or death.

RESULTS

A total of 342 patients with stage IV EGFR variant-positive NSCLC receiving EGFR-TKI therapy met the inclusion criteria. Of these, 145 patients from 2 of the hospitals (n = 117 and 28) formed a training cohort (mean [SD] age, 61 [11] years; 87 [60.0%] female), and the patients from 2 other hospitals comprised 2 external validation cohorts (validation cohort 1: n = 101; mean [SD] age, 57 [12] years; 60 [59.4%] female; and validation cohort 2: n = 96, mean [SD] age, 58 [9] years; 55 [57.3%] female). Fifty-six patients with advanced-stage EGFR variant-positive NSCLC (mean [SD] age, 52 [11] years; 26 [46.4%] female) and 67 patients with advanced-stage EGFR wild-type NSCLC (mean [SD] age, 54 [10] years; 10 [15.0%] female) who received first-line chemotherapy were included. A total of 90 (26%) receiving EGFR-TKI therapy with a high risk of rapid disease progression were identified (median [range] PFS, 7.3 [1.4-32.0] months in the training cohort, 5.0 [0.6-34.6] months in validation cohort 1, and 6.4 [1.8-20.1] months, in validation cohort 2) using the DL semantic signature.The PFS decreased by 36% (hazard ratio, 2.13; 95% CI, 1.30-3.49; P < .001) compared with that in other patients (median [range] PFS, 11.5 [1.5-64.2] months in the training cohort, 10.9 [1.1-50.5] in validation cohort 1, and 8.9 [0.8-40.6] months in validation cohort 2. No significant differences were observed when comparing the PFS of high-risk patients receiving EGFR-TKI therapy with the chemotherapy cohorts (median PFS, 6.9 vs 4.4 months; P = .08). In terms of predicting the tumor progression risk after EGFR-TKI therapy, clinical decisions based on the DL semantic signature led to better survival outcomes than those based on radiomics signature across all risk probabilities by the decision curve analysis.

CONCLUSIONS AND RELEVANCE

This diagnostic/prognostic study provides a clinically applicable approach for identifying patients with stage IV EGFR variant-positive NSCLC who are not likely to benefit from EGFR-TKI therapy. The end-to-end DL-derived semantic features eliminated all manual interventions required while using previous radiomics methods and have a better prognostic performance.

Targeting 14-3-3ζ Overcomes Resistance to Epidermal Growth Factor Receptor-Tyrosine Kinase Inhibitors in Lung Adenocarcinoma via BMP2/Smad/ID1 Signaling

Background: The 14-3-3ζ protein, which acts as a putative oncoprotein, has been found to promote the proliferation, metastasis, and chemoresistance of cancer cells in several cancers including lung adenocarcinoma (LUAD); however, its significance in epidermal growth factor receptor–tyrosine kinase inhibitor (EGFR-TKI) resistance remains unknown.

Methods: The Cancer Genome Atlas (TCGA) database was used to determine 14-3-3ζ expression in pancancer and LUAD. 14-3-3ζ and ID1 expression was then examined in clinical LUAD samples by immunohistochemistry (IHC). Lentiviral transfection with 14-3-3ζ-specific small hairpin RNA (shRNA) was used to establish stable 14-3-3ζ knockdown gefitinib-resistant PC9 (PC9/GR) and H1975 cell lines. The effect of 14-3-3ζ knockdown on reversing EGFR-TKI resistance was determined in vitro by Cell Counting Kit-8 (CCK-8), wound healing, Transwell assays, and flow cytometry. A xenograft tumor model was established to evaluate the role of 14-3-3ζ in EGFR-TKI resistance. Microarray analysis results showed multiple pathways regulated by 14-3-3ζ-shRNA.

Results: In the present study, we demonstrated that based on the TCGA, pancancer and LUAD 14-3-3ζ expression was elevated and predicted unfavorable prognosis. In addition, high 14-3-3ζ expression was associated with advanced T stage, TNM stage, presence of lymph node metastasis and, importantly, poor treatment response to EGFR-TKIs in LUAD patients with EGFR-activating mutations. 14-3-3ζ shRNA sensitized EGFR-TKI-resistant human LUAD cells to gefitinib and reversed epithelial-to-mesenchymal transition (EMT). After 14-3-3ζ depletion, bone morphogenetic protein (BMP) signaling activation was decreased in EGFR-TKI-resistant cells in microarray analysis, which was further validated by Western blot analysis. Furthermore, the expression of 14-3-3ζ positively correlates with ID1 expression in human EGFR-mutant LUAD patient samples. In vivo, there was a reduction in the tumor burden in mice treated with 14-3-3ζ shRNA and gefitinib compared to mice treated with gefitinib alone.

Conclusion: Our work uncovers a hitherto unappreciated role of 14-3-3ζ in EGFR-TKI resistance. This study might provide a potential therapeutic approach for treating LUAD patients harboring EGFR mutations.

SHOC2 Is a Critical Modulator of Sensitivity to EGFR-TKIs in Non-Small Cell Lung Cancer Cells

EGFR mutation-positive patients with non-small cell lung cancer (NSCLC) respond well to treatment with EGFR-tyrosine kinase inhibitors (EGFR-TKI); however, treatment with EGFR-TKIs is not curative, owing to the presence of residual cancer cells with intrinsic or acquired resistance to this class of drugs. Additional treatment targets that may enhance the efficacy of EGFR-TKIs remain elusive. Using a CRISPR/Cas9-based screen, we identified the leucine-rich repeat scaffold protein SHOC2 as a key modulator of sensitivity to EGFR-TKI treatment. On the basis of in vitro assays, we demonstrated that SHOC2 expression levels strongly correlate with the sensitivity to EGFR-TKIs and that SHOC2 affects the sensitivity to EGFR-TKIs in NSCLC cells via SHOC2/MRAS/PP1c and SHOC2/SCRIB signaling. The potential SHOC2 inhibitor celastrol phenocopied SHOC2 depletion. In addition, we confirmed that SHOC2 expression levels were important for the sensitivity to EGFR-TKIs in vivo. Furthermore, IHC showed the accumulation of cancer cells that express high levels of SHOC2 in lung cancer tissues obtained from patients with NSCLC who experienced acquired resistance to EGFR-TKIs. These data indicate that SHOC2 may be a therapeutic target for patients with NSCLC or a biomarker to predict sensitivity to EGFR-TKI therapy in EGFR mutation-positive patients with NSCLC. Our findings may help improve treatment strategies for patients with NSCLC harboring EGFR mutations. IMPLICATIONS: This study showed that SHOC2 works as a modulator of sensitivity to EGFR-TKIs and the expression levels of SHOC2 can be used as a biomarker for sensitivity to EGFR-TKIs.

Endothelin-1-Mediated Drug Resistance in EGFR-Mutant Non-Small Cell Lung Carcinoma

Progression on therapy in non-small cell lung carcinoma (NSCLC) is often evaluated radiographically, however, image-based evaluation of said therapies may not distinguish disease progression due to intrinsic tumor drug resistance or inefficient tumor penetration of the drugs. Here we report that the inhibition of mutated EGFR promotes the secretion of a potent vasoconstrictor, endothelin-1 (EDN1), which continues to increase as the cells become resistant with a mesenchymal phenotype. As EDN1 and its receptor (EDNR) is linked to cancer progression, EDNR-antagonists have been evaluated in several clinical trials with disappointing results. These trials were based on a hypothesis that the EDN1-EDNR axis activates the MAPK-ERK signaling pathway that is vital to the cancer cell survival; the trials were not designed to evaluate the impact of tumor-derived EDN1 in modifying tumor microenvironment or contributing to drug resistance. Ectopic overexpression of EDN1 in cells with mutated EGFR resulted in poor drug delivery and retarded growth in vivo but not in vitro. Intratumoral injection of recombinant EDN significantly reduced blood flow and subsequent gefitinib accumulation in xenografted EGFR-mutant tumors. Furthermore, depletion of EDN1 or the use of endothelin receptor inhibitors bosentan and ambrisentan improved drug penetration into tumors and restored blood flow in tumor-associated vasculature. Correlatively, these results describe a simplistic endogenous yet previously unrealized resistance mechanism inherent to a subset of EGFR-mutant NSCLC to attenuate tyrosine kinase inhibitor delivery to the tumors by limiting drug-carrying blood flow and the drug concentration in tumors. SIGNIFICANCE: EDNR antagonists can be repurposed to improve drug delivery in VEGFA-secreting tumors, which normally respond to TKI treatment by secreting EDN1, promoting vasoconstriction, and limiting blood and drug delivery.

Radiofrequency Ablation with Continued EGFR Tyrosine Kinase Inhibitor Therapy Prolongs Disease Control in EGFR-Mutant Advanced Lung Cancers with Acquired Resistance to EGFR Tyrosine Kinase Inhibitors: Two Case Reports

Objective

Lung cancer remains the leading cause of malignant tumor-related death globally. There is mounting evidence that a large proportion of patients harboring epidermal growth factor receptor (EGFR) mutation and treated with EGFR TKI experience oligoprogressive disease. The optimal treatment strategy for these patients is undetermined. Thus, in this article, we report two cases of EGFR-mutant NSCLC patients with locally resistant lesions achieving disease control via combination therapy.

Patients and Methods

We present two cases of lung adenocarcinoma patients that developed oligoprogressive disease during TKI treatment. For further treatment, the patient then received radiofrequency ablation.

Results

Through follow-up observation, we found that the addition of radiofrequency ablation might provide the clinical benefit of these two NSCLC patients.

Conclusion

Our two cases provide a promising treatment for oligoprogressive disease during the first-line EGFR-TKI therapy.

Clinical Impact of the Epithelial-Mesenchymal Transition in Lung Cancer as a Biomarker Assisting in Therapeutic Decisions

Lung cancer is one of the most common solid cancers and represents the leading cause of cancer death worldwide. Over the last decade, research on the epithelial-mesenchymal transition (EMT) in lung cancer has gained increasing attention. Here, we review clinical and histological features of non-small-cell lung cancer associated with EMT. We then aimed to establish potential clinical implications of EMT in current therapeutic options, including surgery, radiation, targeted therapy against oncogenic drivers, and immunotherapy.

Acquired Resistance of EGFR-Mutated Lung Cancer to Tyrosine Kinase Inhibitor Treatment Promotes PARP Inhibitor Sensitivity

Lung cancers with oncogenic mutations in the epidermal growth factor receptor (EGFR) invariably acquire resistance to tyrosine kinase inhibitor (TKI) treatment. Vulnerabilities of EGFR TKI-resistant cancer cells that could be therapeutically exploited are incompletely understood. Here, we describe a poly (ADP-ribose) polymerase 1 (PARP-1) inhibitor-sensitive phenotype that is conferred by TKI treatment in vitro and in vivo and appears independent of any particular TKI resistance mechanism. We find that PARP-1 protects cells against cytotoxic reactive oxygen species (ROS) produced by nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX). Compared to TKI-naive cells, TKI-resistant cells exhibit signs of increased RAC1 activity. PARP-1 catalytic function is required for PARylation of RAC1 at evolutionarily conserved sites in TKI-resistant cells, which restricts NOX-mediated ROS production. Our data identify a role of PARP-1 in controlling ROS levels upon EGFR TKI treatment, with potentially broad implications for therapeutic targeting of the mechanisms that govern the survival of oncogene-driven cancer cells.

Influence of Biopsy Technique on Molecular Genetic Tumor Characterization in Non-Small Cell Lung Cancer-The Prospective, Randomized, Single-Blinded, Multicenter PROFILER Study Protocol

The detection of molecular alterations is crucial for the individualized treatment of advanced non-small cell lung cancer (NSCLC). Missing targetable alterations may have a major impact on patient's progression free and overall survival. Although laboratory testing for molecular alterations has continued to improve; little is known about how biopsy technique affects the detection rate of different mutations. In the retrospective study detection rate of epidermal growth factor (EGFR) mutations in tissue extracted by bronchoscopic cryobiopsy (CB was significantly higher compared to other standard biopsy techniques. This prospective, randomized, multicenter, single blinded study evaluates the accuracy of molecular genetic characterization of NSCLC for different cell sampling techniques. Key inclusion criteria are suspected lung cancer or the suspected relapse of known NSCLC that is bronchoscopically visible. Patients will be randomized, either to have a CB or a bronchoscopic forceps biopsy (FB). If indicated, a transbronchial needle aspiration (TBNA) of suspect lymph nodes will be performed. Blood liquid biopsy will be taken before tissue biopsy. The primary endpoint is the detection rate of molecular genetic alterations in NSCLC, using CB and FB. Secondary endpoints are differences in the combined detection of molecular genetic alterations between FB and CB, TBNA and liquid biopsy. This trial plans to recruit 540 patients, with 178 evaluable patients per study cohort. A histopathological and molecular genetic evaluation will be performed by the affiliated pathology departments of the national network for genomic medicine in lung cancer (nNGM), Germany. We will compare the diagnostic value of solid tumor tissue, lymph node cells and liquid biopsy for the molecular genetic characterization of NSCLC. This reflects a real world clinical setting, with potential direct impact on both treatment and survival.

Astragalus polysaccharides reverse gefitinib resistance by inhibiting mesenchymal transformation in lung adenocarcinoma cells

Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) have been used as first-line recommended therapy for EGFR mutant non-small cell lung cancer patients. However, epithelial-mesenchymal transition (EMT) can reduce EGFR-TKI sensitivity and lead to resistance. This study was designed to investigate the reversal effect of astragalus polysaccharides (APS) on gefitinib resistance (GR) and to elucidate the underlying mechanisms. PC9 and HCC827 lung cancer cells were stimulated by TGF-β1 to develop EMT-associated GR cells. Cell proliferation, migration and apoptosis assays were used to confirm the effect of gefitinib on GR cells and the therapeutic effect of APS on GR cells after knockdown and over-expression of related signaling pathways. Reverse transcription polymerase chain reaction, western blotting, and immunofluorescent staining assays were used to evaluate the expression levels of E-cadherin, N-cadherin, vimentin, PD-L1, and SREBP-1. Furthermore, proliferation and migration abilities were enhanced, while apoptosis ability was weakened in EMT-associated GR cells. After over-expression of PD-L1, expression levels of N-cadherin, vimentin and SREBP-1 increased, while expression of E-cadherin decreased. After knockdown of PD-L1 or SREBP-1, E-cadherin expression increased, while expression of N-cadherin and vimentin decreased. Further studies revealed that APS promoted apoptosis and reduced proliferation and migration abilities in GR cells. Moreover, APS increased expression of E-cadherin and decreased expression of N-cadherin and vimentin, indicating that it may be related to inhibition of the PD-L1/SREBP-1/EMT signaling pathway. Based on these findings, it can be concluded that APS can reverse acquired resistance to gefitinib in lung cancer cells by inhibiting the PD-L1/SREBP-1/EMT signaling pathway.

Epigenetics and metabolism at the crossroads of stress-induced plasticity, stemness and therapeutic resistance in cancer

Despite the recent advances in the treatment of cancers, acquired drug resistance remains a major challenge in cancer management. While earlier studies suggest Darwinian factors driving acquired drug resistance, recent studies point to a more dynamic process involving phenotypic plasticity and tumor heterogeneity in the evolution of acquired drug resistance. Chronic stress after drug treatment induces intrinsic cellular reprogramming and cancer stemness through a slow-cycling persister state, which subsequently drives cancer progression. Both epigenetic and metabolic mechanisms play an important role in this dynamic process. In this review, we discuss how epigenetic and metabolic reprogramming leads to stress-induced phenotypic plasticity and acquired drug resistance, and how the two reprogramming mechanisms crosstalk with each other.

Impact of pulmonary interstitial lesions on efficacy and prognosis of EGFR-TKI-treated advanced non-small cell lung cancers

Background

This study aimed to assess the impact of pre-existing pulmonary interstitial lesions (PIL) on the efficacy and prognosis of patients with epidermal growth factor receptor (EGFR) mutant non-small cell lung cancer (NSCLC) treated with EGFR tyrosine kinase inhibitor (TKI).

Methods

Patients with advanced NSCLC harboring EGFR exon 19 deletion (E19 del) or exon 21 (E21) L858R were enrolled in this study. All patients underwent high resolution computed tomography (HRCT) chest scans prior to EGFR-TKI treatment. Pre-existing PIL was graded according to HRCT imaging (PIL 0, 1, 2, and 3). Cox proportional-hazards regression models were used to identify the prognostic factors for progression-free survival (PFS).

Results

A total of 134 eligible patients were enrolled. The overall objective response rate (ORR) and median PFS were 73.1% and 10.0 months (95% CI: 7.51–12.49), respectively. There were 62 (46.3%), 25 (18.7%), 28 (20.9%), and 19 (14.1%) cases of PIL grade 0, 1, 2, and 3, respectively, with median PFS and ORR of 12.9 months and 80.6%, 11.0 months and 72.0%, 10.0 months and 71.4%, and 7.0 months and 52.6%, respectively. Multivariate analysis showed that squamous cell carcinoma (vs. adenocarcinoma, HR =4.33), E21 L858R (vs. E19 del, HR =1.57), and PIL grade 3 (vs. grade 0–2, HR =1.60–2.48) were poor prognostic factors for PFS (P<0.05 for all).

Conclusions

Pre-existing PIL grade is an independent prognostic factor for predicting resistance to EGFR-TKIs in patients with EGFR-mutant advanced NSCLC. Higher PIL grade suggests higher risk of early progression.

Frontiers of ctDNA, targeted therapies, and immunotherapy in non-small-cell lung cancer

Non-small-cell lung cancer (NSCLC), a main subtype of lung cancer, is one of the most common causes of cancer death in men and women worldwide. Circulating tumor DNA (ctDNA), tyrosine kinase inhibitors (TKIs) and immunotherapy have revolutionized both our understanding of NSCLC, from its diagnosis to targeted NSCLC therapies, and its treatment. ctDNA quantification confers convenience and precision to clinical decision making. Furthermore, the implementation of TKI-based targeted therapy and immunotherapy has significantly improved NSCLC patient quality of life. This review provides an update on the methods of ctDNA detection and its impact on therapeutic strategies; therapies that target epidermal growth factor receptor (EGFR) and anaplastic lymphoma kinase (ALK) using TKIs such as osimertinib and lorlatinib; the rise of various resistant mechanisms; and the control of programmed cell death-1 (PD-1), programmed cell death ligand-1 (PD-L1), and cytotoxic T-lymphocyte antigen-4 (CTLA-4) by immune checkpoint inhibitors (ICIs) in immunotherapy; blood tumor mutational burden (bTMB) calculated by ctDNA assay as a novel biomarker for immunotherapy. However, NSCLC patients still face many challenges. Further studies and trials are needed to develop more effective drugs or therapies to treat NSCLC.

Timing in combination with radiotherapy and patterns of disease progression in non-small cell lung cancer treated with EGFR-TKI

OBJECTIVES

Tyrosine kinase inhibitor (TKI) has been the standard of care for advanced non-small cell lung cancers (NSCLC) harboring epidermal growth factor receptor (EGFR) mutation, but these tumors invariably develop drug resistance. As progression most frequently advances in sites of original disease, our study sought to explore the time to response for NSCLC to TKI therapy and the patterns of disease progression, to provide evidence for timing and candidates for local therapy intervention.

MATERIALS AND METHODS

A cohort of 105 EGFR-mutated IIIB or IV NSCLC patients treated with EGFR-TKI were retrospectively analyzed. The disease progression patterns were divided into 3 categories: progression in sites of original disease, progression in new distant sites, and combined progression.

RESULTS

Before cut-off date, 80 patients had disease progression. Thirty-three (41.25 %) patients had progression in sites of original disease, 34 (42.5 %) patients had progression in new sites and 13 (16.25 %) patients had combined progression, respectively. The median time to response for responders was 2.00 months (95 %CI 1.28-2.92 months), and the median time to maximal tumor shrinkage for SD patients was 2.00 months (95 %CI 1.42-2.58 months). Multivariate logistic regression model showed that the 21 exon mutation is related to the incidence of original site failure.

CONCLUSION

Over 1/3 of the patients progress at the original sites, which indicated that this subset of patients may benefit from local therapy. Moreover, as the results indicate that considerable shrinkage for TKI therapy occurs in first two months after TKI initiation, local therapy can be adopted after this timepoint, before disease progression. We also propose EGFR gene mutation type as potential inclusion criteria to identify candidates for combined local therapy.

The microcosmos of intratumor heterogeneity: the space-time of cancer evolution

The Cancer Genome Atlas consortium brought us terabytes of information about genetic alterations in different types of human tumors. While many cancer-driver genes have been identified through these efforts, interrogating cancer genomes has also shed new light on tumor complexity. Mutations were found to vary tremendously in their allelic frequencies within the same tumor. Based on those variant allelic frequencies grouping, an estimate of genetically distinct "clones" of cancer cells can be determined for each tumor. It was estimated that 4-8 clones are present in every human tumor. Presence of distinct clones, cells that differ in their genotype and/or phenotype, is one of the roots for the major challenge of effectively curing cancer patients. Any given treatment applied to a heterogeneous mixture of cancer cells will yield distinct responses in different cells and may be ineffective in killing particular clones. Moreover, in highly heterogeneous tumors, stochastically, there is a higher chance of presence of traits, such as point mutations in key receptor tyrosine kinases, that drive drug resistance. Thus, intratumor heterogeneity is like an arsenal, providing a variety of weapons for self-defense against cancer-targeted therapy. However, in this arsenal the supplies are constantly changing, as cancer cells are accumulating new mutations. What is also changing is the battlefield-the tumor microenvironment including all noncancerous cells within the tumor and surrounding tissue, which also contribute to the diversification of cancer's forces. In order to design more effective therapies that would target this ever-changing landscape, we need to learn more about the two elusive variables that shape the tumor ecosystem: the space-how could we exploit the organization of tumor microenvironment? and the time-how could we predict the changes in heterogeneous tumors?

EMT-Mediated Acquired EGFR-TKI Resistance in NSCLC: Mechanisms and Strategies

Acquired resistance inevitably limits the curative effects of epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs), which represent the classical paradigm of molecular-targeted therapies in non-small-cell lung cancer (NSCLC). How to break such a bottleneck becomes a pressing problem in cancer treatment. The epithelial-mesenchymal transition (EMT) is a dynamic process that governs biological changes in various aspects of malignancies, notably drug resistance. Progress in delineating the nature of this process offers an opportunity to develop clinical therapeutics to tackle resistance toward anticancer agents. Herein, we seek to provide a framework for the mechanistic underpinnings on the EMT-mediated acquisition of EGFR-TKI resistance, with a focus on NSCLC, and raise the question of what therapeutic strategies along this line should be pursued to optimize the efficacy in clinical practice.

Drug-adapted cancer cell lines as preclinical models of acquired resistance

Acquired resistance formation limits the efficacy of anti-cancer therapies. Acquired and intrinsic resistance differ conceptually. Acquired resistance is the consequence of directed evolution, whereas intrinsic resistance depends on the (stochastic) presence of pre-existing resistance mechanisms. Preclinical model systems are needed to study acquired drug resistance because they enable: (1) in depth functional studies; (2) the investigation of non-standard treatments for a certain disease condition (which is necessary to identify small groups of responders); and (3) the comparison of multiple therapies in the same system. Hence, they complement data derived from clinical trials and clinical specimens, including liquid biopsies. Many groups have successfully used drug-adapted cancer cell lines to identify and elucidate clinically relevant resistance mechanisms to targeted and cytotoxic anti-cancer drugs. Hence, we argue that drug-adapted cancer cell lines represent a preclinical model system in their own right that is complementary to other preclinical model systems and clinical data.

Advances in Molecular Mechanisms and Immunotherapy Involving the Immune Cell-Promoted Epithelial-to-Mesenchymal Transition in Lung Cancer

Immunotherapy has offered a new opportunity for the treatment of many malignancies. In patients with lung cancer, immune checkpoint inhibitors have significantly improved survival. However, little is known about predictive factors or primary and acquired resistance mechanisms. Epithelial-to-mesenchymal transition (EMT) is a complex of phenotypic changes involved in carcinogenesis and resistance to cancer treatments. Specifically, immune cells in the tumor microenvironment can promote EMT, and mesenchymal phenotype acquisition negatively regulates the anticancer immune response. EMT is associated with higher expression of PD-L1 and other immune checkpoints. In this review, we focused on the role of EMT in the interplay between tumor cells and the immune system, with particular emphasis on lung cancer. On the basis of our findings, we hypothesize that the effects of EMT on immune cells could be overcome in this disease by a new combination of immune checkpoint inhibitors.

Understanding the Mechanisms of Resistance in EGFR-Positive NSCLC: From Tissue to Liquid Biopsy to Guide Treatment Strategy

Liquid biopsy has emerged as an alternative source of nucleic acids for the management of Epidermal Growth Factor Receptor (EGFR)-mutant non-Small Cell Lung Cancer (NSCLC). The use of circulating cell-free DNA (cfDNA) has been recently introduced in clinical practice, resulting in the improvement of the identification of druggable EGFR mutations for the diagnosis and monitoring of response to targeted therapy. EGFR-dependent (T790M and C797S mutations) and independent (Mesenchymal Epithelial Transition [MET] gene amplification, Kirsten Rat Sarcoma [KRAS], Phosphatidyl-Inositol 4,5-bisphosphate 3-Kinase Catalytic subunit Alpha isoform [PI3KCA], and RAF murine sarcoma viral oncogene homolog B1 [BRAF] gene mutations) mechanisms of resistance to EGFR tyrosine kinase inhibitors (TKIs) have been evaluated in plasma samples from NSCLC patients using highly sensitive methods (i.e., digital droplet PCR, Next Generation Sequencing), allowing for the switch to other therapies. Therefore, liquid biopsy is a non-invasive method able to detect the molecular dynamic changes that occur under the pressure of treatment, and to capture tumor heterogeneity more efficiently than is allowed by tissue biopsy. This review addresses how liquid biopsy may be used to guide the choice of treatment strategy in EGFR-mutant NSCLC.

CPSF3 is a promising prognostic biomarker and predicts recurrence of non-small cell lung cancer

Cleavage polyadenylation specificity factor (CPSF) is the core component of the 3′-end processing complex, which determines the site of 3′-end cleavage interactions of specific sequence elements within pre-mRNAs. The present study revealed that all members of the CPSF complex were overexpressed in lung cancer tissue from The Cancer Genome Atlas (TCGA) Lung Cancer Cohort compared with normal lung tissue. Analysis of overall survival and recurrence-free survival verified that only CPSF3 was associated with prognosis and recurrence of lung adenocarcinoma (LUAD), and thus could be a promising biomarker. Additionally, receiver operating characteristic curve analysis revealed that CPSF3 may function as a diagnostic biomarker to distinguish between two histological subtypes of non-small cell lung cancer. Furthermore, analysis of the association of CPSF3 expression with clinicopathological parameters indicated that CPSF3 was associated with smoking history, tumor diameter, lymph node metastasis, clinical stage and radiation therapy in LUAD. Additionally, analysis of the DNA methylation data of the TCGA-LUAD Cohort revealed that CPSF3 DNA CpG sites (cg12057242 and cg25739938) were generally hypomethylated in LUAD compared with normal lung tissue. Correlation analysis identified the CPSF3 DNA CpG site cg25739938 to be negatively correlated with CPSF3 expression, while no correlation was identified with cg12057242. In addition, correlation analysis demonstrated that the overexpression of CPSF3 was correlated with CPSF3 DNA copy number variants (CNAs). The findings indicate that abnormal expression of CPSF3 may be caused by DNA CNAs; and DNA hypermethylation and function may be a promising diagnostic and prognostic indicator for LUAD.

Genomic and Transcriptomic Determinants of Therapy Resistance and Immune Landscape Evolution during Anti-EGFR Treatment in Colorectal Cancer

Despite biomarker stratification, the anti-EGFR antibody cetuximab is only effective against a subgroup of colorectal cancers (CRCs). This genomic and transcriptomic analysis of the cetuximab resistance landscape in 35 RAS wild-type CRCs identified associations of NF1 and non-canonical RAS/RAF aberrations with primary resistance and validated transcriptomic CRC subtypes as non-genetic predictors of benefit. Sixty-four percent of biopsies with acquired resistance harbored no genetic resistance drivers. Most of these had switched from a cetuximab-sensitive transcriptomic subtype at baseline to a fibroblast- and growth factor-rich subtype at progression. Fibroblast-supernatant conferred cetuximab resistance in vitro, confirming a major role for non-genetic resistance through stromal remodeling. Cetuximab treatment increased cytotoxic immune infiltrates and PD-L1 and LAG3 immune checkpoint expression, potentially providing opportunities to treat cetuximab-resistant CRCs with immunotherapy.