Overcoming EMT-associated resistance to anti-cancer drugs via Src/FAK pathway inhibition

Targeting a key FAK-tor: the therapeutic potential of combining focal adhesion kinase (FAK) inhibitors and chemotherapy for chemoresistant non-small cell lung cancer

INTRODUCTION

NSCLC is the leading cause of cancer-related deaths globally, with a low survival rate primarily due to NSCLC frequently becoming chemoresistant. Focal adhesion kinase (FAK) is a non-receptor tyrosine kinase involved in pathways regulating multiple processes in the cell, including survival, migration, and the TME, that contribute to both tumor progression and drug resistance. Recently, FAK inhibitors (FAKi) have shown promising potential for the treatment of NSCLC.

AREAS COVERED

This narrative review aims to summarize key signaling pathways involving FAK that contribute to tumor progression and drug resistance. It will further provide an overview of FAKi currently in pre- and early-phase clinical trials for solid tumors, as well as the therapeutic potential of combining FAKi with chemotherapy, as this has emerged as a promising strategy to overcome chemoresistance in NSCLC.

EXPERT OPINION

It is becoming increasingly clear that FAK is not an oncogenic driver but rather contributes to tumor progression and drug resistance. Hence, while FAKi have only demonstrated modest results in clinical trials when given by themselves, treatment regimens combining other therapies with FAKi have shown promising potential to overcome drug resistance. Lastly, of particular novelty are FAK-PROTACs (proteolysis-targeting chimaeras), which uniquely target both cytosolic and nuclear FAK.

A novel FAK-degrading PROTAC molecule exhibited both anti-tumor activities and efficient MDR reversal effects

FAK (focal adhesion kinase) is widely involved in cancer growth and drug resistance development. Thus, FAK inhibition has emerged as an effective strategy for tumor treatment both as a monotherapy or in combination with other treatments. But the current FAK inhibitors mainly concentrate on its kinase activity, overlooking the potential significance of FAK scaffold proteins. In this study we employed the PROTAC technology, and designed a novel PROTAC molecule F2 targeting FAK based on the FAK inhibitor IN10018. F2 exhibited potent inhibitory activities against 4T1, MDA-MB-231, MDA-MB-468 and MDA-MB-435 cells with IC50 values of 0.73, 1.09, 5.84 and 3.05 μM, respectively. On the other hand, F2 also remarkably reversed the multidrug resistance (MDR) in HCT8/T, A549/T and MCF-7/ADR cells. Both the effects of F2 were stronger than the FAK inhibitor IN10018. To our knowledge, F2 was the first reported FAK-targeted PROTAC molecule exhibiting reversing effects on chemotherapeutic drug resistance, and its highest reversal fold could reach 158 times. The anti-tumor and MDR-reversing effects of F2 might be based on its inhibition on AKT (protein kinase B, PKB) and ERK (extracellular signal-regulated kinase) signaling pathways, as well as its impact on EMT (epithelial-mesenchymal transition). Furthermore, we found that F2 could reduce the protein level of P-gp in HCT8/T cells, thereby contributing to reverse drug resistance from another perspective. Our results will boost confidence in future research focusing on targeting FAK and encourage further investigation of PROTAC with potent in vivo effects.

Phenotypic Plasticity and Cancer: A System Biology Perspective

Epithelial-to-mesenchymal transition (EMT) is a major axis of phenotypic plasticity not only in diseased conditions such as cancer metastasis and fibrosis but also during normal development and wound healing. Yet-another important axis of plasticity with metastatic implications includes the cancer stem cell (CSCs) and non-CSC transitions. However, in both processes, epithelial (E) and mesenchymal (M) phenotypes are not merely binary states. Cancer cells acquire a spectrum of phenotypes with traits, properties, and markers of both E and M phenotypes, giving rise to intermediary hybrid (E/M) phenotypes. E/M cells play an important role in tumor initiation, metastasis, and disease progression in multiple cancers. Furthermore, the hybrid phenotypes also play a major role in causing therapeutic resistance in cancer. Here, we discuss how a systems biology perspective on the problem, which is implicit in the 'Team Medicine' approach outlined in the theme of this Special Issue of The Journal of Clinical Medicine and includes an interdisciplinary team of experts, is more likely to shed new light on EMT in cancer and help us to identify novel therapeutics and strategies to target phenotypic plasticity in cancer.

The EPRS-ATF4-COLI pathway axis is a potential target for anaplastic thyroid carcinoma therapy

BACKGROUND

Anaplastic thyroid carcinoma (ATC) is recognized as the most aggressive and malignant form of thyroid cancer, underscoring the critical need for effective therapeutic strategies to curb its progression and improve patient prognosis. Halofuginone (HF), a derivative of febrifugine, has displayed antitumor properties across various cancer types. However, there is a paucity of published research focused on the potential of HF to enhance the clinical efficacy of treating ATC.

OBJECTIVE

In this study, we thoroughly investigated the antitumor effects and mechanisms of HF in ATC, aiming to discover lead compounds for treating ATC and reveal novel therapeutic targets for ATC tumors.

METHODS

A series of assays, including CCK8, colony formation, tumor xenograft models, and ATC tumor organoid experiments, were conducted to evaluate the anticancer properties of HF both in vitro and in vivo. Techniques such as drug affinity responsive target stability (DARTS), western blot, immunofluorescence, and immunohistochemistry were employed to pinpoint HF target proteins within ATC. Furthermore, we harnessed the GEPIA and GEO databases and performed immunohistochemistry to validate the therapeutic potential of the glutamyl-prolyl-tRNA-synthetase (EPRS)- activating transcription factor 4 (ATF4)- type I collagen (COLI) pathway axis in the context of ATC. The study also incorporated RNA sequencing analysis, confocal imaging, and flow cytometry to delve into the molecular mechanisms of HF in ATC.

RESULTS

HF exhibited a substantial inhibitory impact on cell proliferation in vitro and on tumor growth in vivo. The DARTS results highlighted HF's influence on EPRS within ATC cells, triggering an amino acid starvation response (AASR) by suppressing EPRS expression, consequently leading to a reduction in COLI expression in ATC cells. The introduction of proline mitigated the effect of HF on ATF4 and COLI expression, indicating that the EPRS-ATF4-COLI pathway axis was a focal target of HF in ATC. Analysis of the expression levels of the EPRS, ATF4, and COLI proteins in thyroid tumors, along with an examination of the relationship between COLI expression and thyroid tumor stage, revealed that HF significantly inhibited the growth of ATC tumor organoids, demonstrating the therapeutic potential of targeting the EPRS-ATF4-COLI pathway axis in ATC. RNA sequencing analysis revealed significant differences in the pathways associated with metastasis and apoptosis between control and HF-treated cells. Transwell assays and flow cytometry experiments provided evidence of the capacity of HF to impede cell migration and induce apoptosis in ATC cells. Furthermore, HF hindered cell metastasis by suppressing the epithelial-mesenchymal transition (EMT) pathway, acting through the inhibition of FAK-AKT-NF-κB/Wnt-β-catenin signaling and restraining angiogenesis via the VEGF pathway. HF also promoted apoptosis through the mitochondrial apoptotic pathway.

CONCLUSION

This study provided inaugural evidence suggesting that HF could emerge as a promising therapeutic agent for the treatment of ATC. The EPRS-ATF4-COLI pathway axis stood out as a prospective biomarker and therapeutic target for ATC.

Development of novel N-aryl-2,4-bithiazole-2-amine-based CYP1B1 degraders for reversing drug resistance

Extrahepatic cytochrome P450 1B1 (CYP1B1), which is highly expressed in non-small cell lung cancer, is an attractive target for cancer prevention, therapy, and overcoming drug resistance. Historically, CYP1B1 inhibition has been the primary therapeutic approach for treating CYP1B1-related malignancies, but its success has been limited. This study introduced CYP1B1 degradation as an alternative strategy to counter drug resistance and metastasis in CYP1B1-overexpressing non-small cell lung cancer A549/Taxol cells via a PROTAC strategy. Our investigation revealed that the identification of the potent CYP1B1 degrader PV2, achieving DC50 values of 1.0 nM and inducing >90 % CYP1B1 degradation at concentrations as low as 10 nM in A549/Taxol cells. Importantly, PV2 enhanced the sensitivity of the A549/Taxol subline to Taxol, possibly due to its stronger inhibitory effects on P-gp through CYP1B1 degradation. Additionally, compared to the CYP1B1 inhibitor A1, PV2 effectively suppressed the migration and invasion of A549/Taxol cells by inhibiting the FAK/SRC and EMT pathways. These findings hold promise for a novel therapy targeting advanced CYP1B1+ non-small cell lung cancer.

Focal adhesion kinase-YAP signaling axis drives drug-tolerant persister cells and residual disease in lung cancer

Targeted therapy is effective in many tumor types including lung cancer, the leading cause of cancer mortality. Paradigm defining examples are targeted therapies directed against non-small cell lung cancer (NSCLC) subtypes with oncogenic alterations in EGFR, ALK and KRAS. The success of targeted therapy is limited by drug-tolerant persister cells (DTPs) which withstand and adapt to treatment and comprise the residual disease state that is typical during treatment with clinical targeted therapies. Here, we integrate studies in patient-derived and immunocompetent lung cancer models and clinical specimens obtained from patients on targeted therapy to uncover a focal adhesion kinase (FAK)-YAP signaling axis that promotes residual disease during oncogenic EGFR-, ALK-, and KRAS-targeted therapies. FAK-YAP signaling inhibition combined with the primary targeted therapy suppressed residual drug-tolerant cells and enhanced tumor responses. This study unveils a FAK-YAP signaling module that promotes residual disease in lung cancer and mechanism-based therapeutic strategies to improve tumor response.

Targeting of vulnerabilities of drug-tolerant persisters identified through functional genetics delays tumor relapse

Drug-tolerant persisters (DTPs) are a rare subpopulation of cells within a tumor that can survive therapy through nongenetic adaptive mechanisms to develop relapse and repopulate the tumor following drug withdrawal. Using a cancer cell line with an engineered suicide switch to kill proliferating cells, we perform both genetic screens and compound screens to identify the inhibition of bromodomain and extraterminal domain (BET) proteins as a selective vulnerability of DTPs. BET inhibitors are especially detrimental to DTPs that have reentered the cell cycle (DTEPs) in a broad spectrum of cancer types. Mechanistically, BET inhibition induces lethal levels of ROS through the suppression of redox-regulating genes highly expressed in DTPs, including GPX2, ALDH3A1, and MGST1. In vivo BET inhibitor treatment delays tumor relapse in both melanoma and lung cancer. Our study suggests that combining standard of care therapy with BET inhibitors to eliminate residual persister cells is a promising therapeutic strategy.

Colibactin-producing Escherichia coli enhance resistance to chemotherapeutic drugs by promoting epithelial to mesenchymal transition and cancer stem cell emergence

Human colorectal cancers (CRCs) are readily colonized by colibactin-producing E. coli (CoPEC). CoPEC induces DNA double-strand breaks, DNA mutations, genomic instability, and cellular senescence. Infected cells produce a senescence-associated secretory phenotype (SASP), which is involved in the increase in tumorigenesis observed in CRC mouse models infected with CoPEC. This study investigated whether CoPEC, and the SASP derived from CoPEC-infected cells, impacted chemotherapeutic resistance. Human intestinal epithelial cells were infected with the CoPEC clinical 11G5 strain or with its isogenic mutant, which is unable to produce colibactin. Chemotherapeutic resistance was assessed in vitro and in a xenograft mouse model. Expressions of cancer stem cell (CSC) markers in infected cells were investigated. Data were validated using a CRC mouse model and human clinical samples. Both 11G5-infected cells, and uninfected cells incubated with the SASP produced by 11G5-infected cells exhibited an increased resistance to chemotherapeutic drugs in vitro and in vivo. This finding correlated with the induction of the epithelial to mesenchymal transition (EMT), which led to the emergence of cells exhibiting CSC features. They grew on ultra-low attachment plates, formed colonies in soft agar, and overexpressed several CSC markers (e.g. CD133, OCT-3/4, and NANOG). In agreement with these results, murine and human CRC biopsies colonized with CoPEC exhibited higher expression levels of OCT-3/4 and NANOG than biopsies devoid of CoPEC. Conclusion: CoPEC might aggravate CRCs by inducing the emergence of cancer stem cells that are highly resistant to chemotherapy.

Molecular subtypes of breast cancer predicting clinical benefits of radiotherapy after breast-conserving surgery: a propensity-score-matched cohort study

BACKGROUND

Based on the molecular expression of cancer cells, molecular subtypes of breast cancer have been applied to classify patients for predicting clinical outcomes and prognosis. However, further evidence is needed regarding the influence of molecular subtypes on the efficacy of radiotherapy (RT) after breast-conserving surgery (BCS), particularly in a population-based context. Hence, the present study employed a propensity-score-matched cohort design to investigate the potential role of molecular subtypes in stratifying patient outcomes for post-BCS RT and to identify the specific clinical benefits that may emerge.

METHODS

From 2006 to 2019, the present study included 59,502 breast cancer patients who underwent BCS from the Taiwan National Health Insurance Research Database. Propensity scores were utilized to match confounding variables between patients with and without RT within each subtype of breast cancer, namely luminal A, luminal B/HER2-negative, luminal B/HER2-positive, basal-like, and HER2-enriched ones. Several clinical outcomes were assessed, in terms of local recurrence (LR), regional recurrence (RR), distant metastasis (DM), disease-free survival (DFS), and overall survival (OS).

RESULTS

After post-BCS RT, patients with luminal A and luminal B/HER2-positive breast cancers exhibited a decrease in LR (adjusted hazard ratio [aHR] = 0.18, p < 0.0001; and, 0.24, p = 0.0049, respectively). Furthermore, reduced RR and improved DFS were observed in patients with luminal A (aHR = 0.15, p = 0.0004; and 0.29, p < 0.0001), luminal B/HER2-negative (aHR = 0.06, p = 0.0093; and, 0.46, p = 0.028), and luminal B/HER2-positive (aHR = 0.14, p = 0.01; and, 0.38, p < 0.0001) breast cancers. Notably, OS benefits were found in patients with luminal A (aHR = 0.62, p = 0.002), luminal B/HER2-negative (aHR = 0.30, p < 0.0001), basal-like (aHR = 0.40, p < 0.0001), and HER2-enriched (aHR = 0.50, p = 0.03), but not luminal B/HER2-positive diseases. Remarkably, when considering DM, luminal A patients who received RT demonstrated a lower cumulative incidence of DM than those without RT (p = 0.02).

CONCLUSION

In patients with luminal A breast cancer who undergo BCS, RT could decrease the likelihood of tumor metastasis. After RT, the tumor's hormone receptor status may predict tumor control regarding LR, RR, and DFS. Besides, the HER2 status of luminal breast cancer patients may serve as an additional predictor of OS after post-BCS RT. However, further prospective studies are required to validate these findings.

Dissecting signaling regulators driving AXL-mediated bypass resistance and associated phenotypes by phosphosite perturbations

Receptor tyrosine kinase (RTK)-targeted therapies are often effective but invariably limited by drug resistance. A major mechanism of acquired resistance involves "bypass" switching to alternative pathways driven by non-targeted RTKs that restore proliferation. One such RTK is AXL whose overexpression, frequently observed in bypass resistant tumors, drives both cell survival and associated malignant phenotypes such as epithelial-to-mesenchymal (EMT) transition and migration. However, the signaling molecules and pathways eliciting these responses have remained elusive. To explore these coordinated effects, we generated a panel of mutant lung adenocarcinoma PC9 cell lines in which each AXL intracellular tyrosine residue was mutated to phenylalanine. By integrating measurements of phosphorylation signaling and other phenotypic changes associated with resistance through multivariate modeling, we mapped signaling perturbations to specific resistant phenotypes. Our results suggest that AXL signaling can be summarized into two clusters associated with progressive disease and poor clinical outcomes in lung cancer patients. These clusters displayed favorable Abl1 and SFK motifs and their phosphorylation was consistently decreased by dasatinib. High-throughput kinase specificity profiling showed that AXL likely activates the SFK cluster through FAK1 which is known to complex with Src. Moreover, the SFK cluster overlapped with a previously established focal adhesion kinase (FAK1) signature conferring EMT-mediated erlotinib resistance in lung cancer cells. Finally, we show that downstream of this kinase signaling, AXL and YAP form a positive feedback loop that sustains drug tolerant persister cells. Altogether, this work demonstrates an approach for dissecting signaling regulators by which AXL drives erlotinib resistance-associated phenotypic changes.

The Role of Proteomics and Phosphoproteomics in the Discovery of Therapeutic Targets and Biomarkers in Acquired EGFR-TKI-Resistant Non-Small Cell Lung Cancer

The discovery of potent EGFR-tyrosine kinase inhibitors (EGFR-TKIs) has revolutionized the treatment of EGFR-mutated lung cancer. Despite the fact that EGFR-TKIs have yielded several significant benefits for lung cancer patients, the emergence of resistance to EGFR-TKIs has been a substantial impediment to improving treatment outcomes. Understanding the molecular mechanisms underlying resistance is crucial for the development of new treatments and biomarkers for disease progression. Together with the advancement in proteome and phosphoproteome analysis, a diverse set of key signaling pathways have been successfully identified that provide insight for the discovery of possible therapeutically targeted proteins. In this review, we highlight the proteome and phosphoproteomic analyses of non-small cell lung cancer (NSCLC) as well as the proteome analysis of biofluid specimens that associate with acquired resistance in response to different generations of EGFR-TKI. Furthermore, we present an overview of the targeted proteins and potential drugs that have been tested in clinical studies and discuss the challenges of implementing this discovery in future NSCLC treatment.

Acquired radioresistance in EMT6 mouse mammary carcinoma cell line is mediated by CTLA-4 and PD-1 through JAK/STAT/PI3K pathway

Cancer recurrence is often associated with the acquisition of radioresistance by cancer tissues due to failure in radiotherapy. The underlying mechanism leading to the development of acquired radioresistance in the EMT6 mouse mammary carcinoma cell line and the potential pathway involved was investigated by comparing differential gene expressions between parental and acquired radioresistance cells. EMT6 cell line was exposed to 2 Gy/per cycle of gamma-ray and the survival fraction between EMT6-treated and parental cells was compared. EMT6RR_MJI (acquired radioresistance) cells was developed after 8 cycles of fractionated irradiation. The development of EMT6RR_MJI cells was confirmed with further irradiation at different doses of gamma-ray, and both the survival fraction and migration rates were measured. Higher survival fraction and migration rates were obtained in EMT6RR_MJI cells after exposure to 4 Gy and 8 Gy gamma-ray irradiations compared to their parental cells. Gene expression between EMT6RR_MJI and parental cells was compared, and 16 genes identified to possess more than tenfold changes were selected and validated using RT-PCR. Out of these genes, 5 were significantly up-regulated i.e., IL-6, PDL-1, AXL, GAS6 and APCDD1. Based on pathway analysis software, the development of acquired radioresistance in EMT6RR_MJI was hypothesized through JAK/STAT/PI3K pathway. Presently, CTLA-4 and PD-1 were determined to be associated with JAK/STAT/PI3K pathway, where both their expressions were significantly increased in EMT6RR_MJI compared to parental cells in the 1st, 4th and 8th cycle of radiation. As a conclusion, the current findings provided a mechanistic platform for the development of acquired radioresistance in EMT6RR_MJI through overexpression of CTLA-4 and PD-1, and novel knowledge on therapeutic targets for recurrent radioresistant cancers.

MicroRNA-506 as a tumor suppressor in anaplastic thyroid carcinoma by regulation of WNT and NOTCH signaling pathways

Objectives

Anaplastic thyroid carcinoma (ATC) is an aggressive thyroid tumor type that has a poor prognosis due to its high therapeutic resistance. Since ATC accounts for half of thyroid cancer-related deaths, it is required to introduce novel therapeutic targets to increase survival in ATC patients. WNT and NOTCH signaling pathways are the pivotal regulators of cell proliferation and migration that can be regulated by microRNAs. We assessed the role of miR-506 in the regulation of cell migration, apoptosis, and drug resistance via NOTCH and WNT pathways in ATC cells.

Materials and Methods

The levels of miR-506 expressions were assessed in ATC cells and tissues. The levels of NOTCH, WNT, and EMT-related gene expressions were also assessed in miR-506 ectopic expressed cells compared with controls. Cell migration and drug resistance were also evaluated to assess the role of miR-506 in the regulation of ATC aggressiveness.

Results

There were significant miR-506 down-regulations in ATC cells and clinical samples compared with normal cells and margins. MiR-506 suppressed NOTCH and WNT signaling pathways through LEF1, DVL, FZD1, HEY2, HES5, and HEY2 down-regulations, and APC and GSK3b up-regulations. MiR-506 significantly inhibited ATC cell migration and EMT (P=0.028). Moreover, miR-506 significantly increased Cisplatin (P=0.004), Paclitaxel (P<0.0001), and Doxorubicin (P=0.0014) sensitivities in ATC cells.

Conclusion

MiR-506 regulated EMT, cell migration, and chemoresistance through regulation of WNT and NOTCH signaling pathways in ATC cells. Therefore, after confirmation with animal studies, it can be introduced as an efficient novel therapeutic factor for ATC tumors.

The epigenome and the many facets of cancer drug tolerance

The use of chemotherapeutic agents and the development of new cancer therapies over the past few decades has consequently led to the emergence of myriad therapeutic resistance mechanisms. Once thought to be explicitly driven by genetics, the coupling of reversible sensitivity and absence of pre-existing mutations in some tumors opened the way for discovery of drug-tolerant persisters (DTPs): slow-cycling subpopulations of tumor cells that exhibit reversible sensitivity to therapy. These cells confer multi-drug tolerance, to targeted and chemotherapies alike, until the residual disease can establish a stable, drug-resistant state. The DTP state can exploit a multitude of distinct, yet interlaced, mechanisms to survive otherwise lethal drug exposures. Here, we categorize these multi-faceted defense mechanisms into unique Hallmarks of Cancer Drug Tolerance. At the highest level, these are comprised of heterogeneity, signaling plasticity, differentiation, proliferation/metabolism, stress management, genomic integrity, crosstalk with the tumor microenvironment, immune escape, and epigenetic regulatory mechanisms. Of these, epigenetics was both one of the first proposed means of non-genetic resistance and one of the first discovered. As we describe in this review, epigenetic regulatory factors are involved in most facets of DTP biology, positioning this hallmark as an overarching mediator of drug tolerance and a potential avenue to novel therapies.

Structure-Based Drug Design and Synthesis of Novel N-Aryl-2,4-bithiazole-2-amine CYP1B1-Selective Inhibitors in Overcoming Taxol Resistance in A549 Cells

As a promising therapeutic target for cancer, CYP1B1 is overexpressed in Taxol-resistant A549 cells; however, its role in drug resistance still remains unclear. Bioinformatic analysis data indicated that CYP1B1 was closely correlated with AKT/ERK1/2 and focal adhesion pathways, thereby playing an important role in Taxol resistance and cancer migration/invasion. Along similar lines, the AhR agonist 7,12-dimethylbenz[a]anthracene (DMBA) enhanced Taxol resistance and promoted migration/invasion of A549 and H460 cells likely stemming from CYP1B1 upregulation. Moreover, 83 novel N-aryl-2,4-bithiazole-2-amine CYP1B1-selective inhibitors were designed and synthesized to verify the role of CYP1B1 in Taxol-resistant A549 cells. Impressively, the most potent and selective one, namely, 77, remarkably inhibited AKT/ERK1/2 and FAK/SRC pathways and thereby reversed Taxol resistance as well as inhibited both migration and invasion of A549/Taxol cells. Collectively, this study not only displayed the role of CYP1B1 in Taxol resistance and cancer migration/invasion but also helped unlock the CYP1B1-oriented anticancer discovery.

A Phase I Study of the Non-Receptor Kinase Inhibitor Bosutinib in Combination with Pemetrexed in Patients with Selected Metastatic Solid Tumors

Src is overexpressed in various cancers, including 27% of non-small cell lung cancer NSCLC, and is correlated with poor clinical outcomes. We hypothesize that Src kinase inhibitors, including Bosutinib, may exhibit clinical synergy in combination with the antifolate drug pemetrexed. In this Phase I, dose-escalation, safety, and maximum tolerated dose (MTD)-determining study, 14 patients with advanced metastatic solid tumors that had progressed on "standard of care" chemotherapy were enrolled in a 3 + 3 dose escalation study. Oral Bosutinib was administered once daily beginning on day 1, where the first cohort started at an oral dose of 200 mg daily with pemetrexed 500 mg/m² IV on a three-week schedule. The study's primary objective was to determine the dose-limiting toxicity (DLT), the MTD of Bosutinib in combination with pemetrexed, and the type and frequency of adverse events associated with this treatment. Twelve patients were evaluable for response, including ten patients with adenocarcinoma of the lung, one patient with metastatic adenocarcinoma of the appendix, and one patient with urothelial carcinoma. The median number of Bosutinib and pemetrexed cycles received was 4 (range, 1-4). The MTD of oral Bosutinib in this combination was 300 mg daily. Two patients (17%) had a partial response (PR), and seven patients (58%) showed stable disease (SD) as the best response after the fourth cycle (end of treatment). One patient had disease progression after the second cycle, while three patients had disease progression after the fourth cycle. The two responders and the two patients with the longest stable disease duration or stabilization of disease following progression on multiple systemic therapies demonstrated Src overexpression on immunohistochemical staining of their tumor. The median progression-free survival (PFS) was 6.89 months (95% CI (3.48, 30.85)), and the median overall survival (OS) was 11.7 months (95% CI (3.87, 30.85)). Despite the limitations of this Phase I study, there appears to be potential efficacy of this combination in previously treated patients.

Neutrophil Transcriptional Deregulation by the Periodontal Pathogen Fusobacterium nucleatum in Gastric Cancer: A Bioinformatic Study

Background

Infection with the periodontal pathogen Fusobacterium nucleatum (F. nucleatum) has been associated with gastric cancer. The present study is aimed at uncovering the putative biological mechanisms underlying effects of F. nucleatum–mediated neutrophil transcriptional deregulation in gastric cancer.

Materials and Methods

A gene expression dataset pertaining to F. nucleatum-infected human neutrophils was utilized to identify differentially expressed genes (DEGs) using the GEO2R tool. Candidate genes associated with gastric cancer were sourced from the “Candidate Cancer Gene Database” (CCGD). Overlapping genes among these were identified as link genes. Functional profiling of the link genes was performed using “g:Profiler” tool to identify enriched Gene Ontology (GO) terms, pathways, miRNAs, transcription factors, and human phenotype ontology terms. Protein-protein interaction (PPI) network was constructed for the link genes using the “STRING” tool, hub nodes were identified as key candidate genes, and functionally enriched terms were determined.

Results

The gene expression dataset GEO20151 was downloaded, and 589 DEGs were identified through differential analysis. 886 candidate gastric cancer genes were identified in the CGGD database. Among these, 36 overlapping genes were identified as the link genes. Enriched GO terms included molecular function “enzyme building,” biological process “protein folding,'” cellular components related to membrane-bound organelles, transcription factors ER71 and Sp1, miRNAs miR580 and miR155, and several human phenotype ontology terms including squamous epithelium of esophagus. The PPI network contained 36 nodes and 53 edges, where the top nodes included PH4 and CANX, and functional terms related to intracellular membrane trafficking were enriched.

Conclusion

F nucleatum-induced neutrophil transcriptional activation may be implicated in gastric cancer via several candidate genes including DNAJB1, EHD1, IER2, CANX, and PH4B. Functional analysis revealed membrane-bound organelle dysfunction, intracellular trafficking, transcription factors ER71 and Sp1, and miRNAs miR580 and miR155 as other candidate mechanisms, which should be investigated in experimental studies.

The Development of AXL Inhibitors in Lung Cancer: Recent Progress and Challenges

AXL, along with MER and TYRO3, is a receptor tyrosine kinase from the TAM family. Although AXL itself is not thought to be a potent oncogenic driver, overexpression of AXL is known to trigger tumor cell growth, survival, invasion, metastasis, angiogenesis, epithelial to mesenchymal transition, and immune suppression. Overexpression of AXL is associated with therapy resistance and poor prognosis. Therefore, it is being studied as a marker of prognosis in cancer treatment or as a target in various cancer types. Recently, many preclinical and clinical studies on agents with various mechanisms targeting AXL have been actively conducted. They include small molecule inhibitors, monoclonal antibodies, and antibody-drug conjugates. This article reviewed the fundamental role of AXL in solid tumors, and the development in research of AXL inhibitors in recent years. Emphasis was placed on the function of AXL in acquired therapy resistance in patients with non-small cell lung cancer (NSCLC). Since clinical needs increase in NSCLC patients with acquired resistance after initial therapy, recent research efforts have focused on a combination treatment with AXL inhibitors and tyrosine kinase inhibitors or immunotherapy to overcome resistance. Lastly, we deal with challenges and limitations encountered in the development of AXL inhibitors.

DIPG Harbors Alterations Targetable by MEK Inhibitors, with Acquired Resistance Mechanisms Overcome by Combinatorial Inhibition

The survival of children with diffuse intrinsic pontine glioma (DIPG) remains dismal, with new treatments desperately needed. In a prospective biopsy-stratified clinical trial, we combined detailed molecular profiling and drug screening in newly established patient-derived models in vitro and in vivo. We identified in vitro sensitivity to MEK inhibitors in DIPGs harboring MAPK pathway alterations, but treatment of patient-derived xenograft models and a patient at relapse failed to elicit a significant response. We generated trametinib-resistant clones in a BRAFG469V model through continuous drug exposure and identified acquired mutations in MEK1/2 with sustained pathway upregulation. These cells showed hallmarks of mesenchymal transition and expression signatures overlapping with inherently trametinib-insensitive patient-derived cells, predicting sensitivity to dasatinib. Combined trametinib and dasatinib showed highly synergistic effects in vitro and on ex vivo brain slices. We highlight the MAPK pathway as a therapeutic target in DIPG and show the importance of parallel resistance modeling and combinatorial treatments for meaningful clinical translation.

SIGNIFICANCE

We report alterations in the MAPK pathway in DIPGs to confer initial sensitivity to targeted MEK inhibition. We further identify for the first time the mechanism of resistance to single-agent targeted therapy in these tumors and suggest a novel combinatorial treatment strategy to overcome it in the clinic. This article is highlighted in the In This Issue feature, p. 587.

Translational Strategies for Repotrectinib in Neuroblastoma

Limited clinical data are available regarding the utility of multikinase inhibition in neuroblastoma. Repotrectinib (TPX-0005) is a multikinase inhibitor that targets ALK, TRK, JAK2/STAT, and Src/FAK, which have all been implicated in the pathogenesis of neuroblastoma. We evaluated the preclinical activity of repotrectinib monotherapy and in combination with chemotherapy as a potential therapeutic approach for relapsed/refractory neuroblastoma. In vitro sensitivity to repotrectinib, ensartinib, and cytotoxic chemotherapy was evaluated in neuroblastoma cell lines. In vivo antitumor effect of repotrectinib monotherapy, and in combination with chemotherapy, was evaluated using a genotypically diverse cohort of patient-derived xenograft (PDX) models of neuroblastoma. Repotrectinib had comparable cytotoxic activity across cell lines irrespective of ALK mutational status. Combination with chemotherapy demonstrated increased antiproliferative activity across several cell lines. Repotrectinib monotherapy had notable antitumor activity and prolonged event-free survival compared with vehicle and ensartinib in PDX models (P < 0.05). Repotrectinib plus chemotherapy was superior to chemotherapy alone in ALK-mutant and ALK wild-type PDX models. These results demonstrate that repotrectinib has antitumor activity in genotypically diverse neuroblastoma models, and that combination of a multikinase inhibitor with chemotherapy may be a promising treatment paradigm for translation to the clinic.

How to Achieve Therapeutic Response in Erlotinib-Resistant Head and Neck Squamous Cell Carcinoma? New Insights from Stable Isotope Labeling with Amino Acids in Cell Culture-Based Quantitative Tyrosine Phosphoproteomics

Resistance to cancer chemotherapy is a major global health burden. Epidermal growth factor receptor (EGFR) is a proven therapeutic target for multiple cancers of epithelial origin. Despite its overexpression in >90% of head and neck squamous cell carcinoma (HNSCC) patients, tyrosine kinase inhibitors such as erlotinib have shown a modest response in clinical trials. Cellular heterogeneity is thought to play an important role in HNSCC therapeutic resistance. Genomic alterations alone cannot explain all resistance mechanisms at play in a heterogeneous system. It is thus important to understand the biochemical mechanisms associated with drug resistance to determine potential strategies to achieve clinical response. We investigated tyrosine kinase signaling networks in erlotinib-resistant cells using quantitative tyrosine phosphoproteomics approach. We observed altered phosphorylation of proteins involved in cell adhesion and motility in erlotinib-resistant cells. Bioinformatics analysis revealed enrichment of pathways related to regulation of the actin cytoskeleton, extracellular matrix (ECM)-receptor interaction, and endothelial migration. Of importance, enrichment of the focal adhesion kinase (PTK2) signaling pathway downstream of EGFR was also observed in erlotinib-resistant cells. To the best of our knowledge, we present the first report of tyrosine phosphoproteome profiling in erlotinib-resistant HNSCC, with an eye to inform new ways to achieve clinical response. Our findings suggest that common signaling networks are at play in driving resistance to EGFR-targeted therapies in HNSCC and other cancers. Most notably, our data suggest that the PTK2 pathway genes may potentially play a significant role in determining clinical response to erlotinib in HNSCC tumors.

Targeting HSF1 as a Therapeutic Strategy for Multiple Mechanisms of EGFR Inhibitor Resistance in EGFR Mutant Non-Small-Cell Lung Cancer

Simple Summary

We attempted to identify target proteins and compounds that can be used to overcome EGFR-TKI resistance in NSCLC. To accomplish this, we generated EGFR inhibitor erlotinib-resistant HCC827-ErlR cells and obtained a list of differentially expressed genes. Then, we performed connectivity map analysis and identified heat shock factor 1 (HSF1) as a potential target protein to overcome erlotinib resistance. Using specific HSF1 shRNAs and KRIBB11 (N²-(1H-Indazol-5-yl)-N⁶-methyl-3-nitropyridine-2,6-diamine), we proved the effectiveness of HSF1 inhibition for overcoming erlotinib resistance in vitro. In addition, we proved the efficacy of emetine in inhibiting HSF1 activity and the tumor growth of erlotinib-resistant PC9-ErlR cells in a mouse model.

Abstract

Although EGFR-TKI treatment of NSCLC (non-small-cell lung cancer) patients often achieves profound initial responses, the efficacy is transient due to acquired resistance. Multiple receptor tyrosine kinase (RTK) pathways contribute to the resistance of NSCLC to first- and third-generation EGFR-TKIs, such as erlotinib and osimertinib. To identify potential targets for overcoming EGFR-TKI resistance, we performed a gene expression signature-based strategy using connectivity map (CMap) analysis. We generated erlotinib-resistant HCC827-ErlR cells, which showed resistance to erlotinib, gefitinib, osimertinib, and doxorubicin. A list of differentially expressed genes (DEGs) in HCC827-ErlR cells was generated and queried using CMap analysis. Analysis of the top 4 compounds from the CMap list suggested HSF1 as a potential target to overcome EGFR-TKI resistance. HSF1 inhibition by using HSF1 shRNAs or KRIBB11 decreased the expression of HSF1 downstream proteins, such as HSP70 and HSP27, and also decreased the expression of HSP90/HSP70/BAG3 client proteins, such as BCL2, MCL1, EGFR, MET, and AXL, causing apoptosis of EGFR-TKI-resistant cancer cells. Finally, we demonstrated the efficacy of the HSF1 inhibitor on PC9-ErlR cells expressing mutant EGFR (T790M) in vivo. Collectively, these findings support a targetable HSF1-(HSP90/HSP70/BAG3)-(BCL2/MCL1/EGFR/MET/AXL) pathway to overcome multiple mechanisms of EGFR-TKI resistance.

The role of epithelial-mesenchymal transition-regulating transcription factors in anti-cancer drug resistance

The complex orchestration of gene expression that mediates the transition of epithelial cells into mesenchymal cells is implicated in cancer development and metastasis. As the primary regulator of the process, epithelial-mesenchymal transition-regulating transcription factors (EMT-TFs) play key roles in metastasis. They are also highlighted in recent preclinical studies on resistance to cancer therapy. This review describes the role of three main EMT-TFs, including Snail, Twist1, and zinc-finger E homeobox-binding 1 (ZEB1), relating to drug resistance and current possible approaches for future challenges targeting EMT-TFs.

Thinking Differently about Cancer Treatment Regimens

Most experimental cancer drugs ultimately fail during the course of clinical development, contributing to the high cost of the few that are granted regulatory approval. Moreover, approved drugs often deliver only modest clinical benefit to patients with advanced disease due to the development of resistance. Here, we discuss opportunities we consider promising to overcome drug resistance associated with interactions between signaling pathways and the presence of multiple coexisting cell states within tumors with distinct vulnerabilities. We highlight how understanding drug-resistance mechanisms can enable innovative treatment regimens that deliver longer-lasting benefit to patients.

Resistance to paclitaxel induces glycophenotype changes and mesenchymal-to-epithelial transition activation in the human prostate cancer cell line PC-3

The development of the multidrug resistance phenotype is one of the major challenges faced in the treatment of cancer. The multidrug resistance phenotype is characterized by cross-resistance to drugs with different chemical structures and mechanisms of action. In this work, we hypothesized that the acquisition of resistance in cancer is accompanied by activation of the epithelial-to-mesenchymal transition process, where the tumor cell acquires a more mobile and invasive phenotype; a fundamental step in tumor progression and in promoting the invasion of other organs and tissues. In addition, it is known that atypical glycosylations are characteristic of tumor cells, being used as biomarkers. We believe that the acquisition of the multidrug resistance phenotype and the activation of epithelial-to-mesenchymal transition provoke alterations in the cell glycophenotype, which can be used as glycomarkers for chemoresistance and epithelial-to-mesenchymal transition processes. Herein, we induced the multidrug resistance phenotype in the PC-3 human prostate adenocarcinoma line through the continuous treatment with the drug paclitaxel. Our results showed that the induced cell multidrug resistance phenotype (1) acquired a mixed profile between epithelial and mesenchymal phenotypes and (2) modified the glycophenotype, showing an increase in the level of sialylation and in the number of branched glycans. Both mechanisms are described as indicators of poor prognosis.

Inhibition of ELF3 confers synthetic lethality of PARP inhibitor in non-small cell lung cancer

BACKGROUND

E74 Like ETS Transcription Factor 3 (ELF3) functions as a transcriptional factor to regulate non-small cell lung cancer (NSCLC) differentiation and progression. Poly(ADP-ribose) polymerase (PARP) inhibitors demonstrate anti-tumor effect in NSCLC. This study aimed to investigate whether ELF3 confers synthetic lethal with PARP inhibitor in NSCLC.

MATERIALS AND METHODS

The sensitivity of PARP inhibitor, Olaparib, to different NSCLC cell lines was determined by half maximal inhibitory concentration (IC₅₀). Expression of ELF3 in NSCLC cell lines was evaluated by western blot. The effects of ELF3 on cytotoxicity of Olaparib to NSCLC were investigated by MTT (3-(4,5- di methyl thiazol -2-yl)-2,5-di phenyl tetrazolium bromide) and colony formation assays. The underlying mechanism involved in synthetic lethality with ELF3 and PARP inhibitors in NSCLC were detected by immunofluorescence and Western blot.

RESULTS

ELF3 was up-regulated in NSCLC cell lines exhibiting resistance to PARP inhibitor, Olaparib. Knock down of ELF3 decreased the sensitivity and enhanced cytotoxicity of Olaparib to NSCLC cells. Moreover, knock down of ELF3 increased S139 phosphorylated histone H2AX (γH2AX), and inhibited homologous recombination activity via down-regulation of DNA repair protein RAD51 homolog 1 (RAD51), thus showing deficiency in DNA damage repair. Over-expression of ELF3 could up-regulate phosphorylation of AKT (Protein kinase B), while knock down of ELF3 regulated homologous recombination-mediated DNA repair via down-regulation of phosphorylation of AKT.

CONCLUSION

Knock down of ELF3 revealed homologous recombination deficiency via AKT signaling pathway, and synthetic lethality with ELF3 inhibition and PARP inhibitor indicated the clinical significance of PARP inhibitor in ELF3-deficient NSCLC.

Drug resistance in cancer: mechanisms and tackling strategies

Drug resistance developed towards conventional therapy is one of the important reasons for chemotherapy failure in cancer. The various underlying mechanism for drug resistance development in tumor includes tumor heterogeneity, some cellular levels changes, genetic factors, and others novel mechanisms which have been highlighted in the past few years. In the present scenario, researchers have to focus on these novel mechanisms and their tackling strategies. The small molecules, peptides, and nanotherapeutics have emerged to overcome the drug resistance in cancer. The drug delivery systems with targeting moiety enhance the site-specificity, receptor-mediated endocytosis, and increase the drug concentration inside the cells, thus minimizing drug resistance and improve their therapeutic efficacy. These therapeutic approaches work by modulating the different pathways responsible for drug resistance. This review focuses on the different mechanisms of drug resistance and the recent advancements in therapeutic approaches to improve the sensitivity and effectiveness of chemotherapeutics.

Src Family Kinases as Therapeutic Targets in Advanced Solid Tumors: What We Have Learned so Far

Src is the prototypal member of Src Family tyrosine Kinases (SFKs), a large non-receptor kinase class that controls multiple signaling pathways in animal cells. SFKs activation is necessary for the mitogenic signal from many growth factors, but also for the acquisition of migratory and invasive phenotype. Indeed, oncogenic activation of SFKs has been demonstrated to play an important role in solid cancers; promoting tumor growth and formation of distant metastases. Several drugs targeting SFKs have been developed and tested in preclinical models and many of them have successfully reached clinical use in hematologic cancers. Although in solid tumors SFKs inhibitors have consistently confirmed their ability in blocking cancer cell progression in several experimental models; their utilization in clinical trials has unveiled unexpected complications against an effective utilization in patients. In this review, we summarize basic molecular mechanisms involving SFKs in cancer spreading and metastasization; and discuss preclinical and clinical data highlighting the main challenges for their future application as therapeutic targets in solid cancer progression

Convergent Evolution, Evolving Evolvability, and the Origins of Lethal Cancer

Advances in curative treatment to remove the primary tumor have increased survival of localized cancers for most solid tumor types, yet cancers that have spread are typically incurable and account for >90% of cancer-related deaths. Metastatic disease remains incurable because, somehow, tumors evolve resistance to all known compounds, including therapies. In all of these incurable patients, de novo lethal cancer evolves capacities for both metastasis and resistance. Therefore, cancers in different patients appear to follow the same eco-evolutionary path that independently manifests in affected patients. This convergent outcome, that always includes the ability to metastasize and exhibit resistance, demands an explanation beyond the slow and steady accrual of stochastic mutations. The common denominator may be that cancer starts as a speciation event when a unicellular protist breaks away from its multicellular host and initiates a cancer clade within the patient. As the cancer cells speciate and diversify further, some evolve the capacity to evolve: evolvability. Evolvability becomes a heritable trait that influences the available variation of other phenotypes that can then be acted upon by natural selection. Evolving evolvability may be an adaptation for cancer cells. By generating and maintaining considerable heritable variation, the cancer clade can, with high certainty, serendipitously produce cells resistant to therapy and cells capable of metastasizing. Understanding that cancer cells can swiftly evolve responses to novel and varied stressors create opportunities for adaptive therapy, double-bind therapies, and extinction therapies; all involving strategic decision making that steers and anticipates the convergent coevolutionary responses of the cancers.

Boosted photocatalytic activity induced NAMPT-Regulating therapy based on elemental bismuth-humic acids heterojunction for inhibiting tumor proliferation/migration/inflammation

Due to the highly complex biological formation procedure, tumor is still difficult to be treated efficiently and always associated with proliferation, migration and inflammation during treatment. Herein, a novel strategy of boosted photocatalytic activity induced NAMPT-regulating therapy is used for tumors inhibition based on FK866 loaded bismuth-humic acids heterojunction (Bi-HA/FK866). With the reduction function of HA, Bi (Ⅲ) can be reduced to elemental Bi, which can be excited by NIR laser to form electron-hole pair due to the narrow bandgap. Moreover, the coated HA and Bi could form a heterojunction structure, which could decrease the electron-hole recombination, and further boost the photocatalytic activity, leading to highly efficient ROS generation and GSH depletion. The resulted ROS could induce DNA damage of the tumor cells, thus enhancing the sensitivity to the inhibitor of NAMPT (FK866) to downregulate NAD/ERK/NF-κB signal pathways, and eventually simultaneously prevent cancer progression. Moreover, the decreased NAD could downregulate NADPH and further suppress the innate antioxidant defense system by inhibiting reduction of GSSG. The boosted photocatalytic activity induced NAMPT-regulating therapy offers a promising way to address the important issue of penetration depth limitation induced cancer relapse and migration, providing more possibilities toward successful clinical application.

P4HB modulates epithelial-mesenchymal transition and the β-catenin/Snail pathway influencing chemoresistance in liver cancer cells

The aim of the present study was to investigate the role of prolyl 4-hydroxylase beta polypeptide (P4HB) in the chemoresistance of liver cancer. Drug-resistant liver cancer cell lines, such as HepG2/adriamycin (ADR) cells, were treated and screened using adriamycin. Gene interference was used to silence the expression of P4HB in liver cancer cells. Cell viability, invasiveness and migration were assessed using CCK8, Transwell and wound healing assays, respectively. In addition, changes to key genes and proteins in the epithelial-mesenchymal transition (EMT) and β-catenin/Snail pathway were analyzed using reverse transcription-quantitative PCR and western blotting. Drug-resistant HepG2/ADR cells were successfully cultivated; the IC₅₀ to ADR for HepG2/ADR and HepG2 cell lines was 4.85 and 0.61 µM, respectively. HepG2/ADR cells exhibited higher invasion and migration abilities compared with HepG2 cells (P<0.05). E-cadherin mRNA and protein expression levels in HepG2/ADR cells were decreased significantly, whereas P4HB, N-cadherin and vimentin mRNA and protein levels were significantly increased compared with HepG2 cells (all P<0.05). Knockdown of P4HB significantly decreased cell viability and the invasion and migration ability of HepG2/ADR cells. In addition, P4HB knockdown enhanced E-cadherin mRNA and protein expression levels, whereas N-cadherin, vimentin, total β-catenin, nuclear β-catenin and Snail mRNA and protein levels were significantly decreased (all P<0.05). Overall, the present study demonstrated that EMT and β-catenin/Snail pathway influence P4HB modulation in liver cancer chemoresistance.

Feeling Things Out: Bidirectional Signaling of the Cell-ECM Interface, Implications in the Mechanobiology of Cell Spreading, Migration, Proliferation, and Differentiation

Biophysical cues stemming from the extracellular environment are rapidly transduced into discernible chemical messages (mechanotransduction) that direct cellular activities-placing the extracellular matrix (ECM) as a potent regulator of cell behavior. Dynamic reciprocity between the cell and its associated matrix is essential to the maintenance of tissue homeostasis and dysregulation of both ECM mechanical signaling, via pathological ECM turnover, and internal mechanotransduction pathways contribute to disease progression. This review covers the current understandings of the key modes of signaling used by both the cell and ECM to coregulate one another. By taking an outside-in approach, the inherent complexities and regulatory processes at each level of signaling (ECM, plasma membrane, focal adhesion, and cytoplasm) are captured to give a comprehensive picture of the internal and external mechanoregulatory environment. Specific emphasis is placed on the focal adhesion complex which acts as a central hub of mechanical signaling, regulating cell spreading, migration, proliferation, and differentiation. In addition, a wealth of available knowledge on mechanotransduction is curated to generate an integrated signaling network encompassing the central components of the focal adhesion, cytoplasm and nucleus that act in concert to promote durotaxis, proliferation, and differentiation in a stiffness-dependent manner.

Cyclooxygenase-2 mediates gefitinib resistance in non-small cell lung cancer through the EGFR/PI3K/AKT axis

Gefitinib is a potent inhibitor of EGFR and represents the front-line treatment for non-small cell lung cancer (NSCLC) therapeutics. However, NSCLC patients are prone to develop acquired resistance through as yet, undefined mechanisms of resistance. Here, we investigated the role of COX-2 during gefitinib resistance in NSCLC cells and revealed its underlying mechanism(s) of action. We report the upregulation of COX-2 in gefitinib-resistant NSCLC tissues and cells, which is associated with poor prognosis. In vitro assays in NSCLC cells (PC9/GR) showed that COX-2 facilitates gefitinib resistance in NSCLC cells through its effects on P-gp, MRP1, and BCRP, and cancer cell migration and invasion. In vivo, COX-2 silencing could repress tumor growth. We found that the overexpression of COX-2 enhances the transcription of MMP-2, MMP-7, and MMP-9 which mediates PI3K-AKT activation. In summary, we demonstrate that COX-2 mediates the gefitinib resistance of NSCLC cells through its interaction with EGFR and the PI3K-AKT axis. This highlights COX-2 as a novel molecular target for NSCLC.

Acquired resistance to targeted therapies in NSCLC: Updates and evolving insights

While significant advancements have been made in the available therapies for metastatic non-small cell lung cancer (NSCLC), acquired resistance remains a major barrier to treatment. We have not yet achieved the ability to cure advanced NSCLC with systemic therapy, despite our growing understanding of many of the oncogenic drivers of this disease. Rather, the emergence of drug-tolerant and drug-resistant cells remains the rule, even in the face of increasingly potent targeted therapies. In this review, we provide a broad overview of the mechanisms of resistance to targeted therapy that have been demonstrated across molecular subtypes of NSCLC, highlighting the dynamic interplay between driver oncogene, bypass signaling pathways, shifting cellular phenotypes, and surrounding tumor microenvironment.

Combined treatment with N-acetylcysteine and gefitinib overcomes drug resistance to gefitinib in NSCLC cell line

We aimed to explore the molecular substrate underlying EGFR‐TKI resistance and investigate the effects of N‐acetylcysteine (NAC) on reversing EGFR‐TKI resistance. In the current research, the effects of NAC in combination with gefitinib on reversing gefitinib resistance were examined using CCK‐8 assay, combination index (CI) method, matrigel invasion assay, wound‐healing assay, flow cytometry, western blot, and quantitative real‐time PCR (qRT‐PCR). CCK8 assay showed that NAC plus gefitinib combination overcame EGFR‐TKI resistance in non‐small cell lung cancer (NSCLC) cells by lowering the value of half maximal inhibitory concentration (IC50). CI calculations demonstrated a synergistic effect between the two drugs (CI < 1). Matrigel invasion assay and wound healing assay demonstrated a decrease in migration and invasion ability of PC‐9/GR cells after NAC and gefitinib treatment. Flow cytometry displayed enhanced apoptosis in the combination group. Western blot and qRT‐PCR revealed that increased E‐cadherin and decreased vimentin in the combination group. When PP2 was administered with gefitinib, the same effects were seen. Our findings suggest that NAC could restore the sensitivity of gefitinib‐resistant NSCLC cells to gefitinib via suppressing Src activation and reversing epithelial‐mesenchymal transition.

Role of Focal Adhesion Kinase in Small-Cell Lung Cancer and Its Potential as a Therapeutic Target

Small-cell lung cancer (SCLC) represents 15% of all lung cancers and it is clinically the most aggressive type, being characterized by a tendency for early metastasis, with two-thirds of the patients diagnosed with an extensive stage (ES) disease and a five-year overall survival (OS) as low as 5%. There are still no effective targeted therapies in SCLC despite improved understanding of the molecular steps leading to SCLC development and progression these last years. After four decades, the only modest improvement in OS of patients suffering from ES-SCLC has recently been shown in a trial combining atezolizumab, an anti-PD-L1 immune checkpoint inhibitor, with carboplatin and etoposide, chemotherapy agents. This highlights the need to pursue research efforts in this field. Focal adhesion kinase (FAK) is a non-receptor protein tyrosine kinase that is overexpressed and activated in several cancers, including SCLC, and contributing to cancer progression and metastasis through its important role in cell proliferation, survival, adhesion, spreading, migration, and invasion. FAK also plays a role in tumor immune evasion, epithelial-mesenchymal transition, DNA damage repair, radioresistance, and regulation of cancer stem cells. FAK is of particular interest in SCLC, being known for its aggressiveness. The inhibition of FAK in SCLC cell lines demonstrated significative decrease in cell proliferation, invasion, and migration, and induced cell cycle arrest and apoptosis. In this review, we will focus on the role of FAK in cancer cells and their microenvironment, and its potential as a therapeutic target in SCLC.

Leptin Promotes Expression of EMT-Related Transcription Factors and Invasion in a Src and FAK-Dependent Pathway in MCF10A Mammary Epithelial Cells

Leptin is one of the main adipokines secreted in breast tissue. Leptin promotes epithelial-mesenchymal transition (EMT), cell migration and invasion in epithelial breast cells, leading to tumor progression. Although, the molecular mechanisms that underlie these events are not fully understood, the activation of different signaling pathways appears to be essential. In this sense, the effects of leptin on the activation of kinases like Src and FAK, which regulate signaling pathways that activate the EMT program, are not completely described. Therefore, we investigated the involvement of these kinases using an in vitro model for leptin-induced EMT process in the non-tumorigenic MCF10A cell line. To this end, MCF10A cells were stimulated with leptin, and Src and FAK activation was assessed. Specific events occurring during EMT were also evaluated in the presence or absence of the kinases' chemical inhibitors PP2 and PF-573228. For instance, we tested the expression and subcellular localization of the EMT-related transcription factors Twist and β-catenin, by western blot and immunofluorescence. We also evaluated the secretion and activation of matrix metalloproteases (MMP-2 and MMP-9) by gelatin zymography. Invasiveness properties of leptin-stimulated cells were determined by invadopodia formation assays, and by the Transwell chamber method. Our results showed that leptin promotes EMT through Src and FAK activation, which leads to the secretion and activation of MMP-2 and MMP-9, invadopodia formation and cell invasion in MCF10A cells. In conclusion, our data suggest that leptin promotes an increase in the expression levels of Twist and β-catenin, the secretion of MMP-2, MMP-9, the invadopodia formation and invasion in MCF10A cells in a Src and FAK-dependent manner.

CXCR7 Reactivates ERK Signaling to Promote Resistance to EGFR Kinase Inhibitors in NSCLC

Although EGFR mutant-selective tyrosine kinase inhibitors (TKI) are clinically effective, acquired resistance can occur by reactivating ERK. We show using in vitro models of acquired EGFR TKI resistance with a mesenchymal phenotype that CXCR7, an atypical G protein-coupled receptor, activates the MAPK-ERK pathway via β-arrestin. Depletion of CXCR7 inhibited the MAPK pathway, significantly attenuated EGFR TKI resistance, and resulted in mesenchymal-to-epithelial transition. CXCR7 overexpression was essential in reactivation of ERK1/2 for the generation of EGFR TKI-resistant persister cells. Many patients with non-small cell lung cancer (NSCLC) harboring an EGFR kinase domain mutation, who progressed on EGFR inhibitors, demonstrated increased CXCR7 expression. These data suggest that CXCR7 inhibition could considerably delay and prevent the emergence of acquired EGFR TKI resistance in EGFR-mutant NSCLC. SIGNIFICANCE: Increased expression of the chemokine receptor CXCR7 constitutes a mechanism of resistance to EGFR TKI in patients with non-small cell lung cancer through reactivation of ERK signaling.

The prognosis comparison of different molecular subtypes of breast tumors after radiotherapy and the intrinsic reasons for their distinct radiosensitivity

Radiotherapy can increase the cell cycle arrest that promotes apoptosis, reduces the risk of tumor recurrence and has become an irreplaceable component of systematic treatment for patients with breast cancer. Substantial advances in precise radiotherapy unequivocally indicate that the benefits of radiotherapy vary depending on intrinsic subtypes of the disease; luminal A breast cancer has the highest benefit whereas human epidermal growth factor receptor 2 (HER2)-positive and triple negative breast cancer (TNBC) are affected to a lesser extent irrespective of the selection of radiotherapy strategies, such as conventional whole-breast irradiation (CWBI), accelerated partial-breast irradiation (APBI), and hypofractionated whole-breast irradiation (HWBI). The benefit disparity correlates with the differential invasiveness, malignance, and radiosensitivity of the subtypes. A combination of a number of molecular mechanisms leads to the strong radioresistant profile of HER2-positive breast cancer, and sensitization to irradiation can be induced by multiple drugs or compounds in luminal disease and TNBC. In this review, we aimed to summarize the prognostic differences between various subtypes of breast tumors after CWBI, APBI, and HWBI, the potential reasons for drug-enhanced radiosensitivity in luminal breast tumors and TNBC, and the robust radioresistance of HER2-positive cancer.

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Simultaneous Inhibition of EGFR and HER2 via Afatinib Augments the Radiosensitivity of Nasopharyngeal Carcinoma Cells

Ionizing radiation (IR) is the central component of the therapeutic scheme for nasopharyngeal carcinoma (NPC) at present. Previous studies show that inhibition of epidermal growth factor receptor (EGFR) enhances the radiosensitivity of NPC; however the effects of EGFR-targeted agents are limited. In this study, we observed that simultaneously inhibition of EGFR and HER2 by afatinib could augment the radiosensitivity of NPC cells; this approach has an advantage over erlotinib-mediated inhibition of EGFR alone. The afatinib-induced augmentation of NPC cell radiosensitivity was associated with increases in apoptosis and accumulation of DNA damage that were induced by radiation. In addition, the crosstalk between radiation-induced activities and EGFR-, and HER2-related downstream pathways may contribute to the enhancement of radiosensitivity. Our findings indicate the potential of repositioning afatinib or other ERBB-family-targeted agents for improving radiation response in NPC cells.

Resistance to Src inhibition alters the BRAF-mutant tumor secretome to promote an invasive phenotype and therapeutic escape through a FAK>p130Cas>c-Jun signaling axis

Few therapy options exist for patients with advanced papillary and anaplastic thyroid cancer. We and others have previously identified c-Src as a key mediator of thyroid cancer pro-tumorigenic processes and a promising therapeutic target for thyroid cancer. To increase the efficacy of targeting Src in the clinic, we sought to define mechanisms of resistance to the Src inhibitor, dasatinib, to identify key pathways to target in combination. Using a panel of thyroid cancer cell lines expressing clinically relevant mutations in BRAF or RAS, which were previously developed to be resistant to dasatinib, we identified a switch to a more invasive phenotype in the BRAF-mutant cells as a potential therapy escape mechanism. This phenotype switch is driven by FAK kinase activity, and signaling through the p130Cas>c-Jun signaling axis. We have further shown this more invasive phenotype is accompanied by alterations in the secretome through the increased expression of pro-inflammatory cytokines, including IL-1β, and the pro-invasive metalloprotease, MMP-9. Furthermore, IL-1β signals via a feedforward autocrine loop to promote invasion through a FAK>p130Cas>c-Jun>MMP-9 signaling axis. We further demonstrate that upfront combined inhibition of FAK and Src synergistically inhibits growth and invasion, and induces apoptosis in a panel of BRAF- and RAS-mutant thyroid cancer cell lines. Together our data demonstrate that acquired resistance to single-agent Src inhibition promotes a more invasive phenotype through an IL-1β>FAK>p130Cas>c-Jun >MMP signaling axis, and that combined inhibition of FAK and Src has the potential to block this inhibitor-induced phenotype switch.

MicroRNA-574-3p regulates epithelial mesenchymal transition and cisplatin resistance via targeting ZEB1 in human gastric carcinoma cells

MicroRNA-574-3p (miR-574-3p) has different roles in different cancer types. However, the exact regulation mechanism of miR-574-3p in gastric cancer (GC) progression remains unclear. Thus, we aimed to evaluate the role of miR-574-3p in GC metastasis. We investigated the mechanism via which miR-574-3p regulated cancer cell migration and invasion to determine the relationship between epithelial mesenchymal transition (EMT) and drug resistance. Our results indicated that human GC cell line SGC7901 cells were more sensitive to cisplatin (DDP), but SGC7901 cisplatin-resistant cells (SGC7901/DDP) were more resistant to DDP and had mesenchymal characteristics. In addition, miR-574-3p overexpression up-regulated E-cadherin expression, and concomitantly down-regulated the expression of vimentin. We also identified zinc finger E-box binding homeobox transcription factor 1 (ZEB1), a crucial EMT inducer gene, as a new target of miR-574-3p. In fact, miR-574-3p bound the 3' untranslated region (3'-UTR) of ZEB1, regulating expression of this transcription factor at both the mRNA and protein levels. Furthermore, miR-574-3p overexpression reduced the migratory and invasive properties of the SGC7901/DDP cells and inhibited cisplatin (DDP) resistance in vitro and in vivo. In conclusion, the results indicated that miR-574-3p inhibited the EMT and enhanced cisplatin sensitivity in GC cells by suppressing ZEB1. These results provide further evidence for the critical roles of miR-574-3p and ZEB1 in invasion and migration regulation characteristics of GC cells.

Principles of Resistance to Targeted Cancer Therapy: Lessons from Basic and Translational Cancer Biology

Identification of the genomic drivers of cancer has led to the clinical development of targeted therapies that strike at the heart of many malignancies. Nonetheless, many cancers outsmart such precision-medicine efforts, and thus therapeutic resistance contributes significantly to cancer mortality. Attempts to understand the basis for resistance in patient samples and laboratory models has yielded two major benefits: one, more effective chemical inhibitors and rational combination therapies are now employed to prevent or circumvent resistance pathways; and two, our understanding of how oncogenic mutations drive cancer cell survival and oncogene addiction is deeper and broader, highlighting downstream or parallel cellular programs that shape these phenotypes. This review discusses emerging principles of resistance to therapies targeted against key oncogenic drivers.

FAK is Required for Tumor Metastasis-Related Fluid Microenvironment in Triple-Negative Breast Cancer

Cancer cell metastasis is the main cause of death in patients with cancer. Many studies have investigated the biochemical factors that affect metastasis; however, the role of physical factors such as fluid shear stress (FSS) in tumorigenesis and metastasis have been less investigated. Triple-negative breast cancer (TNBC) has a higher incidence of lymph node invasion and distant metastasis than other subtypes of breast cancer. In this study, we investigated the influence of FSS in regulating the malignant behavior of TNBC cells. Our data demonstrate that low FSS promotes cell migration, invasion, and drug resistance, while high FSS has the opposite results; additionally, we found that these phenomena were regulated through focal adhesion kinase (FAK). Using immunohistochemistry staining, we show that FAK levels correlate with the nodal stage and that FAK is a significant independent predictor of overall survival in patients. Altogether, these data implicate FAK as a fluid mechano-sensor that regulates the cell motility induced by FSS and provide a strong rationale for cancer treatments that combine the use of anti-cancer drugs and strategies to modulate tumor interstitial fluid flow.

[Research Progress of the Role of EMT in EGFR-TKIs Resistance of Non-small Cell Lung Cancer]

肺癌是全世界范围内发病率和死亡率最高的恶性肿瘤之一，其中大约80%是非小细胞肺癌（non-small cell lung cancer, NSCLC）。目前分子靶向治疗已成为NSCLC的一线治疗方法，其中表皮生长因子受体-酪氨酸激酶抑制剂（epidermal growth factor receptor-tyrosine kinase inhibitors, EGFR-TKIs）越来越多地应用于临床治疗，但EGFR-TKI的获得性耐药成为制约EGFR-TKI继续使用的瓶颈。上皮间质转化（epithelial-mesenchymal transition, EMT）是上皮细胞转化为间质表型细胞的生物学现象，可促进肺癌转移、侵袭以及肿瘤细胞获得干性。此外，EMT也是引起NSCLC对EGFR-TKIs耐药的原因之一。有研究发现，逆转NSCLC细胞的间质表型，耐药的细胞能恢复对吉非替尼的敏感性，提示靶向EMT的治疗，或能阻止甚至是逆转NSCLC细胞对EGFR-TKIs的耐药，本文对EMT在NSCLC EGFR-TKIs耐药中的研究进展作一综述。

Simultaneous Fluorescence Visualization of Epithelial-Mesenchymal Transition and Apoptosis Processes in Tumor Cells for Evaluating the Impact of Epithelial-Mesenchymal Transition on Drug Efficacy

The epithelial-mesenchymal transition (EMT) process plays a pivotal role in acquiring invasive and metastatic properties and has been recognized as a crucial driver of epithelial-derived tumor malignancies. It is necessary to determine the role of EMT in promoting or suppressing carcinoma progression through investigating the relationship between EMT and apoptosis. We designed a multicolor fluorescent nanoprobe for simultaneously imaging the epithelial biomarker E-cadherin mRNA, the mesenchymal marker vimentin mRNA, and the apoptotic marker caspase-3. EMT and apoptosis progresses could be visually detected, which were used to study the effect of EMT on apoptosis and further assess the influence of EMT on drug efficacy in different cancer cells. We believe the designed nanoprobe can offer a new strategy for visualizing EMT and apoptosis in tumor cells and will be a promising tool to investigate the efficiency of drugs targeting EMT-related therapies in living cells.

Mifepristone inhibits proliferation, migration and invasion of HUUA cells and promotes its apoptosis by regulation of FAK and PI3K/AKT signaling pathway

Purpose

The aim was to investigate mifepristone effects on endometrial carcinoma and the related mechanism.

Methods

HHUA cells were treated with DMEM containing different concentrations of mifepristone. HHUA cells treated with 100 μmol/L mifepristone were named the Mifepristone group. HHUA cells co-transfected with pcDNA3.1-PI3K and pcDNA3.1-AKT overexpression vectors were treated with 100 μmol/L mifepristone and named the Mifepristone + PI3K/AKT group. mRNA expression was detected by quantitative reverse transcription PCR. Protein expression was performed by Western blot. Cell proliferation was conducted by MTT assay. Wound-healing assay was conducted. Transwell was used to detect cells migration and invasion. Apoptosis detection was performed by flow cytometry.

Results

Mifepristone inhibited HHUA cells proliferation in a dose-dependent manner. Compared with HHUA cells treated with 0 μmol/L mifepristone, HHUA cells treated by 50–100 μmol/L mifepristone had a lower wound-healing rate, a greater number of migrating and invasive cells (P<0.01), as well as a higher percentage of apoptotic cells and Caspase-3 expression (P<0.01). When HHUA cells were treated with 50–100 μmol/L of mifepristone, FAK, p-FAK, p-PI3K and p-AKT relative expression was all significantly lower than HHUA cells treated with 0 μmol/L of mifepristone (P<0.01). Compared with the Mifepristone group, HHUA cells of the Mifepristone + PI3K/AKT group had a lower cell growth inhibition rate and percentage of apoptotic cells (P<0.01).

Conclusion

Mifepristone inhibited HUUA cells proliferation, migration and invasion and promoted its apoptosis by regulation of FAK and PI3K/AKT signaling pathway.

Personalized therapy for lung cancer: striking a moving target

Molecular targeted therapy heralded a new era for the treatment of patients with oncogene-driven advanced-stage non-small-cell lung cancer (NSCLC). Molecular testing at the time of diagnosis guides therapy selection, and targeted therapies in patients with activating mutations in EGFR, BRAF, and rearrangements in anaplastic lymphoma kinase (ALK) and ROS1 have become part of routine care. These therapies have extended the median survival from a mere few months to greater than 3 years for patients with stage 4 disease. However, despite the initial success, these treatments are eventually met with molecular resistance. Selective pressure leads to cellular adaption to maintain cancer growth, making resistance complex and the treatment challenging. This review focuses on recent advances in targeted therapy, mechanisms of resistance, and therapeutic strategies to overcome resistance in patients with lung cancer.