Targeting AXL and mTOR Pathway Overcomes Primary and Acquired Resistance to WEE1 Inhibition in Small-Cell Lung Cancer

Prospects of current AXL-targeting therapies in early phase cancer trials

INTRODUCTION

AXL, a member of the TAM (TYRO3, AXL, and MERTK) family of receptor tyrosine kinases, controls pro-tumorigenic signaling cascades and cancer-immunological functions, and promotes drug resistance. Due to AXL's multifaceted role and therapeutic activity in preclinical studies, a variety of AXL inhibitors are being developed and tested in clinical trials for cancer treatment. Some clinical studies are showing promising results for AXL inhibitors as monotherapy and in combination with standard of care therapeutics. Currently, no selective AXL-targeting therapy has reached FDA-approval, but several compounds have entered phase II and III studies.

AREA COVERED

We elaborate on the role of AXL in cancer progression and suppressing anti-cancer immunity at both the molecular level and immune cell interaction level. Additionally, we review pre-clinical and clinical data of AXL-targeting agents.

EXPERT OPINION

Preclinical and several early clinical trials demonstrated the safety of AXL-targeting monotherapies with some evidence of efficacy. Additionally, multiple novel combination regimens including AXL-targeting agents to overcome resistance mechanisms are being actively examined with some promising results. However, patient selection and companion biomarkers may be critical for the success of AXL-targeting therapies.

AXL kinase inhibitor exhibits antitumor activity by inducing apoptotic cell death in triple-negative breast cancer cells

Triple-negative breast cancer (TNBC) is a subtype of breast cancer associated with a poor prognosis and decreased patient survival. It is intimately linked to AXL overexpression and AXL hyperactivation. Here, we explored the therapeutic potential of AX-0085, a small molecule AXL inhibitor. While AX-0085 was previously characterized in the context of lung adenocarcinoma, this study demonstrates its application in triple-negative breast cancer (TNBC) models. AX-0085 exhibited high binding affinity to the ATP binding site located beneath the conserved glycine-rich loop (P-loop) that links the β1 and β2 strands of the AXL kinase domain. Furthermore, it was demonstrated that the benzamide group of AX-0085 and LyS567's Nζ atom could generate a hydrogen bond. AX-0085 efficiently suppressed the AXL/GAS6 signaling pathway activation in TNBC cells in vitro, which in turn prevented AXL/GAS6 signaling-dependent pro-cancerous behavior like cell proliferation, invasion, migration, and epithelial-mesenchymal transition (EMT). In TNBC, an AX-0085-induced cell cycle arrest that took place during the G1 phase reduced the expression of CYCLIN E and CDK2. Additionally, AX-0085 facilitated apoptotic cell death in TNBC. Treatment of AX-0085 on in vivo mouse xenografts transplanted with 4 T1 cells showed a significant tumor reduction. Thus, our findings demonstrate that AX-0085 has an effective therapeutic role in TNBC by inhibiting AXL activation.

A Hybrid Energy-Based and AI-Based Screening Approach for the Discovery of Novel Inhibitors of AXL

AXL, part of the TAM receptor tyrosine kinase family, plays a significant role in the growth and survival of various tissues and tumors, making it a critical target for cancer therapy. This study introduces a novel high-throughput virtual screening (HTVS) methodology that merges an AI-enhanced graph neural network, PLANET, with a geometric deep learning algorithm, DeepDock. Using this approach, we identified potent AXL inhibitors from our database. Notably, compound 9, with an IC50 of 9.378 nM, showed excellent inhibitory activity, suggesting its potential as a candidate for further research. We also performed molecular dynamics simulations to explore the interactions between compound 9 and AXL, providing insights for future enhancements. This hybrid screening method proves effective in finding promising AXL inhibitors, and advancing the development of new cancer therapies.

Novel affibody molecules targeting the AXL extracellular structural domain for molecular imaging and targeted therapy of gastric cancer

Gastric cancer (GC) has a poor prognosis and high mortality because it is often diagnosed at an advanced stage. Targeted therapeutics are considered an important class for advanced GC treatment. However, the fewer effective therapeutic targets and the poor coverage of the GC population limit the use of GC targeted therapies. Recent research suggests that the AXL receptor tyrosine kinase (AXL) plays an vital role in the survival and proliferation of GC cells, and blocking AXL pathway may be an effective strategy for targeted therapies. On the other hand, the affibody molecule, with its small size and faster penetration of tissue, has great potential in tumor imaging and targeted therapy. In this study, we report the novel AXL-binding affibody molecules (ZAXL:239) screened by a phage-displayed peptide library. The ZAXL:239 could specifically bind and interact with AXL proteins in vitro and in vivo, as demonstrated by surface plasmon resonance, co-immunoprecipitation, immuno-fluorescence co-localization, and near infrared fluorescent imaging. In addition, ZAXL:239 affibody molecules could significantly inhibit the proliferative activity and induce apoptosis of AXL-positive GC cells by decreasing the phosphorylation levels of the PI3K/AKT1 and MEK/ERK pathway, leading to the suppression of the downstream nuclear protein c-myc. Moreover, ZAXL:239 was found to have significant anti-tumor effects in AXL-positive GC transplantation tumor nude mouse models. In brief, we provide strong evidence that the novel ZAXL:239 affibody molecules have great potential as a potent tumor-specific molecular imaging and targeted therapeutic agents for GC.

Genomic Profiling of Extensive Stage Small-Cell Lung Cancer Patients Identifies Molecular Factors Associated with Survival

Objective

Extensive stage Small-Cell Lung Cancer (ES-SCLC) is the most lethal lung cancer, and the addition of immunotherapy conferred a slight survival benefit for patients. Extensive molecular profiling of patients treated with chemotherapy (CT) or chemotherapy plus immunotherapy (CT+IO) would be able to identify molecular factors associated with patients' survival.

Material and Methods

In this retrospective study, 99 ES-SCLC patients were considered. Of the 79 includible patients, 42 received CT (median age 71 y/o, I-IIIQ: 65-76), and 37 received CT+IO (median age 71 y/o, I-IIIQ 66-75). The FoundationOne CDx assay was performed on patients' tumor tissues.

Results

The most mutated genes were TP53 (99%), RB1 (78%), PTEN (23%) and MLL2 (20%), with no significant differences between the treatment groups. As a continuous variable, Tumor Mutation Burden (TMB) had an effect on patients' progression-free survival (PFS) by type of treatment (HR 1.81 (95%, CI: 0.99-3.31) and HR 0.84 (95%, CI: 0.56-1.26) for patients treated with CT and CT+IO, respectively). TMB was also computed and dichotomized using two different cut-offs: considering cut-offs of 10 mut/Mb and >16 mut/Mb, 45 patients (57%) and 68 patients (86.1%) had a low TMB, respectively. A high TMB (cut-off 10 mut/Mb) predicted worse PFS in patients treated with CT (p=0.046); even though not statistically significant, a high TMB (cut-off 16 mut/Mb) predicted a better survival in patients treated with CT+IO. Moreover, at univariate analysis, MLL2 mutations were associated with better prognosis in the overall case series (HRPFS = 0.51, 95% CI: 0.28-0.94), and overall survival (HROS = 0.52, 95% CI: 0.28-0.97).

Conclusion

In ES-SCLC, TMB is associated with worse survival in patients treated with CT alone, and with better survival in patients treated with CT+IO, whether considered as a continuous or a dichotomized variable, at different cut-offs. Alterations in epigenetic factors are also associated to better patient prognosis.

AXL signaling in cancer: from molecular insights to targeted therapies

AXL, a member of the TAM receptor family, has emerged as a potential target for advanced-stage human malignancies. It is frequently overexpressed in different cancers and plays a significant role in various tumor-promoting pathways, including cancer cell proliferation, invasion, metastasis, epithelial-mesenchymal transition (EMT), angiogenesis, stemness, DNA damage response, acquired therapeutic resistance, immunosuppression, and inflammatory responses. Beyond oncology, AXL also facilitates viral infections, including SARS-CoV-2 and Zika highlighting its importance in both cancer and virology. In preclinical models, small-molecule kinase inhibitors targeting AXL have shown promising anti-tumorigenic potential. This review primarily focuses on the induction, regulation and biological functions of AXL in mediating these tumor-promoting pathways. We discuss a range of therapeutic strategies, including recently developed small-molecule tyrosine kinase inhibitors (TKIs), monoclonal antibodies, and antibody-drug conjugates (ADCs), anti-AXL-CAR, and combination therapies. These interventions are being examined in both preclinical and clinical studies, offering the potential for improved drug sensitivity and therapeutic efficacy. We further discuss the mechanisms of acquired therapeutic resistance, particularly the crosstalk between AXL and other critical receptor tyrosine kinases (RTKs) such as c-MET, EGFR, HER2/HER3, VEGFR, PDGFR, and FLT3. Finally, we highlight key research areas that require further exploration to enhance AXL-mediated therapeutic approaches for improved clinical outcomes.

AZD1775 synergizes with SLC7A11 inhibition to promote ferroptosis

Tumor suppressor p53-mediated cell cycle arrest and DNA damage repair may exert cytoprotective effects against cancer therapies, including WEE1 inhibition. Considering that p53 activation can also lead to multiple types of cell death, the role of this tumor suppressor in WEE1 inhibitor-based therapies remains disputed. In this study, we reported that nucleolar stress-mediated p53 activation enhanced the WEE1 inhibitor AZD1775-induced ferroptosis to suppress lung cancer growth. Our findings showed that AZD1775 promoted ferroptosis by blocking cystine uptake, an action similar to that of Erastin. Meanwhile, inhibition of WEE1 by the WEE1 inhibitors or siRNAs induced compensatory upregulation of SLC7A11, which conferred resistance to ferroptosis. Mechanistically, AZD1775 prevented the enrichment of H3K9me3, a histone marker of transcriptional repression, on the SLC7A11 promoter by repressing the expression of the histone methyltransferase SETDB1, thereby enhancing NRF2-mediated SLC7A11 transcription. This finding was also validated using the H3K9me3 inhibitor BRD4770. Remarkably, we found that the nucleolar stress-inducing agent Actinomycin D (Act. D) inhibited SLC7A11 expression by activating p53, thus augmenting AZD1775-induced ferroptosis. Moreover, the combination of AZD1775 and Act. D synergistically suppressed wild-type p53-harboring lung cancer cell growth both in vitro and in vivo. Altogether, our study demonstrates that AZD1775 promotes ferroptosis by targeting cystine uptake but also mediates the adaptive activation of SLC7A11 through the WEE1-SETDB1 cascade and NRF2-induced transcription, and inhibition of SLC7A11 by Act. D boosts the anti-tumor efficacy of AZD1775 by enhancing ferroptosis in cancers with wild-type p53.

State of Lung Cancer in Egypt: Moving Towards Improved Guidelines for Prevention, Screening, Treatment, and Clinical Care Programs

Lung cancer remains a leading cause of cancer-related mortality globally and presents significant challenges in Egypt. In 2023, the first annual meeting of the Thoracic Oncology Multidisciplinary Faculty, organized by the Egyptian Cancer Research Network and the Egyptian Society of Respiratory Neoplasms, was held in Cairo, Egypt. The meeting aimed to address gaps in lung cancer management across Egypt and the broader Middle East and North Africa region. The discussions focused on the challenges posed by NSCLC and SCLC and emphasized the need for enhanced prevention, early detection, and treatment strategies. Key areas of concern include limited access to advanced diagnostics, such as comprehensive genomic profiling, and the underutilization of targeted therapies and immunotherapies, mainly owing to financial barriers. The meeting highlighted the importance of strengthening lung cancer screening programs, improving smoking cessation efforts, and addressing environmental risk factors like air pollution. Furthermore, the event underscored the need for greater research and collaboration, particularly in areas like precision oncology. The conference concluded with strategic recommendations to improve lung cancer prevention, screening, and treatment, aligning Egypt's lung cancer care with global advancements and ensuring equitable access to cutting-edge therapies.

Schlafen 11 Expression in Patients With Small Cell Lung Cancer and Its Association With Clinical Outcomes

BACKGROUND

Schlafen 11 (SLFN-11) has been identified as a sensitizer of tumor cells to DNA-damaging agents. However, the relationship between SLFN-11 expression and clinical outcomes in patients with small cell lung cancer (SCLC) remains unexplored. Thus, we aimed to evaluate the impact of SLFN-11 expression on survival in patients with limited-stage (LS) SCLC.

METHODS

We conducted a retrospective review of data from patients pathologically diagnosed with LS-SCLC post-surgery between January 2008 and December 2018. SLFN-11 expression was assessed using immunohistochemistry in tissue microarrays and scored using a histology (H)-score (range: 0-300).

RESULTS

Overall, 86 patients were included in the analysis with a median H-score of 43 for SLFN-11 expression. Among the patients, 44 had high SLFN-11 expression (provisionally defined as H-score ≥ 43). No significant differences in clinical profiles were observed between the two groups (high and low SLFN expression). The median survival durations were not reached (NR; 95% confidence interval [CI]: 65.1 months to NR) and 33.5 months (95% CI: 24.2 months to NR) for patients with high and low SLFN-11 expression, respectively (hazard ratio [HR]: 0.40, 95% CI: 0.19-0.81; p = 0.012). Among patients who relapsed post-surgery (n = 21), the median survival durations were 22.0 (95% CI: 7.6-44.9 months) and 8.1 (95% CI: 1.8-24.6 months) months in patients with high and low SLFN-11 expression, respectively (HR: 0.22, 95% CI: 0.06-0.84; p = 0.026).

CONCLUSIONS

High SLFN-11 expression is associated with relatively longer survival in patients with LS-SCLC in both those undergoing surgery and those who have relapsed.

WEE1 confers resistance to KRASG12C inhibitors in non-small cell lung cancer

KRASG12C inhibitors sotorasib and adagrasib have been approved for the treatment of KRASG12C-mutant non-small cell lung cancer (NSCLC). However, the efficacy of single-agent treatments is limited, presumably due to multiple resistance mechanisms. To overcome these therapeutic limitations, combination strategies that potentiate the antitumor efficacy of KRASG12C inhibitors must be developed. Through unbiased high-throughput screening of 1395 kinase inhibitors, we identified adavosertib, a WEE1 inhibitor, as a promising combination partner of sotorasib. The combination of sotorasib and adavosertib exhibited synergistic antiproliferative activities both in vitro and in vivo, irrespective of TP53, STK11, and KEAP1 co-mutation profiles. WEE1 inhibition potentiated MCL-1-mediated apoptosis in sotorasib-treated cancer cells. Mechanistically, the combination downregulated MCL-1 protein levels by attenuating de novo translation and enhancing its degradation. WEE1 overexpression conferred resistance against sotorasib via MCL-1 upregulation. Moreover, cells that acquired sotorasib resistance profoundly upregulated both WEE1 and MCL-1 proteins, highlighting WEE1 as a crucial driver of sotorasib resistance. Importantly, WEE1 inhibition re-sensitized resistant cells to sotorasib treatment. The current findings demonstrate that combined inhibition of KRASG12C and WEE1 not only exhibits synergistic antitumor efficacy but also overcomes resistance to KRASG12C inhibitors, thus representing a novel therapeutic strategy for KRASG12C-mutant NSCLC.

Lurbinectedin sensitizes PD-L1 blockade therapy by activating STING-IFN signaling in small-cell lung cancer

Lurbinectedin is an approved second-line treatment for small-cell lung cancer (SCLC). SCLC clinical trials combining lurbinectedin with PD-L1 blockade are currently ongoing. However, the immunomodulatory effects of lurbinectedin remain largely unknown. In this study, we demonstrate that lurbinectedin treatment activates the STING pathway, which increases interferon (IFN) signaling, pro-inflammatory chemokines, and major histocompatibility complex class I (MHC-I) in SCLC models. Lurbinectedin treatment augments the anti-tumor immune response of PD-L1 blockade with significant tumor regression in first-line and maintenance settings in SCLC mouse models. In vivo, lurbinectedin treatment increases CD8+ T cells and M1 macrophages and decreases immunosuppressive M2 macrophages. STING and CD8 depletion reverses the anti-tumor response. Interestingly, our study shows that lurbinectedin treatment upregulates MHC-I/II genes and CD8 in SCLC clinical samples. We provide mechanistic insights into the effect of lurbinectedin on STING-mediated multimodal immune activation and demonstrate that lurbinectedin treatment represents a promising therapeutic strategy to potentiate the efficacy of immunotherapy in SCLC.

Knockdown of ribosomal protein L22-like 1 arrests the cell cycle and promotes apoptosis in colorectal cancer

Objective

Colorectal cancer (CRC) remains a remarkable challenge despite considerable advancements in its treatment, due to its high recurrence rate, metastasis, drug resistance, and heterogeneity. Molecular targets that can effectively inhibit CRC growth must be identified to address these challenges. Therefore, we aim to reveal the regulatory effect of ribosomal protein L22-like 1 (RPL22L1) on the proliferation and apoptosis of CRC cells and its potential mechanism.

Material and Methods

We detected the expression of RPL22L1 from the Cancer Genome Atlas, Gene Expression Omnibus and UALCAN databases. The effects of RPL22L1 on CRC growth and migration were determined by knocking down RPL22L1 in human CRC cell lines and those on the cell cycle and apoptosis using flow cytometry. The influence of RPL22L1 knockdown on xenograft tumor growth was verified in vivo. The potential RPL22L1 mechanisms in promoting cancer were predicted with RNA sequencing (RNAseq). The molecular mechanism of enhanced apoptosis and cell cycle arrest in RPL22L1 knockdown was revealed using real-time reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR) and Western blotting.

Results

The present study reveals a considerable upregulation of RPL22L1 expression in CRC as well as in diverse tumor tissues, and most cells within the CRC tumor microenvironment (TME) demonstrate RPL22L1 expression. Notably, this elevated expression level of RPL22L1 exhibits a strong association with an unfavorable prognosis among patients diagnosed with CRC (P < 0.05). Furthermore, the association between RPL22L1 expression and the CRC TME index did not exhibit statistical significance (P > 0.05). However, RPL22L1 knockdown experiments revealed a substantial suppression of growth and migratory capacities in CRC cells RKO and HCT116 (P < 0.05). Flow cytometry analysis exhibited that on RPL22L1 knockdown, a remarkable arrest of the G1 and S phases of the cell cycle (P < 0.05) occurred. In addition, a remarkable elevation in the level of cell apoptosis was observed (P < 0.001). RNAseq exhibited that cell cycle, DNA replication, and mechanistic target of rapamycin (mTOR) complex 1pathway were inhibited after RPL22L1 knockdown, whereas the apoptosis pathway was activated (P < 0.05). Validation through RT-qPCR and western blot analysis also corroborated the downregulation of P70S6K, MCM3, MCM7, GADD45B, WEE1, and MKI67 expression levels, following RPL22L1 knockdown (P < 0.05). Consequent rescue experiments offered supportive evidence, indicating the involvement of the mTOR pathway in mediating the influence of RPL22L1 on the promotion of cell cycle progression. Moreover, in vivo assays involving tumor-bearing mice exhibited that diminished RPL22L1 levels led to arrested CRC growth (P < 0.05).

Conclusion

These findings support RPL22L1 as a possible prognostic and therapeutic target in CRC, providing novel insights into the development of anticancer medications.

A Phase I First-in-Human Study of ABBV-011, a Seizure-Related Homolog Protein 6-Targeting Antibody-Drug Conjugate, in Patients with Small Cell Lung Cancer

PURPOSE

Seizure-related homolog protein 6 (SEZ6) is a novel target expressed in small cell lung cancer (SCLC). ABBV-011, a SEZ6-targeted antibody conjugated to calicheamicin, was evaluated in a phase I study (NCT03639194) in patients with relapsed/refractory SCLC. We report initial outcomes of ABBV-011 monotherapy.

PATIENTS AND METHODS

ABBV-011 was administered intravenously once every 3 weeks during dose escalation (0.3-2 mg/kg) and expansion. Patients with SEZ6-positive tumors (≥25% of tumor cells with ≥1+ staining intensity by IHC) were preselected for expansion. Safety, tolerability, antitumor activity, and pharmacokinetics were evaluated.

RESULTS

As of August 2022, 99 patients received ABBV-011 monotherapy [dose escalation, n = 36; Japanese dose evaluation, n = 3; dose expansion, n = 60 (1 mg/kg, n = 40)]; the median age was 63 years (range, 41-79 years). Also, 32%, 41%, and 26% of patients received 1, 2, and ≥3 prior therapies, respectively. The maximum tolerated dose was not reached through 2.0 mg/kg. The most common treatment-emergent adverse events were fatigue (50%), nausea (42%), and thrombocytopenia (41%). The most common hepatic treatment-emergent adverse events were increased aspartate aminotransferase (22%), increased γ-glutamyltransferase (21%), and hyperbilirubinemia (17%); two patients experienced veno-occlusive liver disease. The objective response rate was 19% (19/98). In the 1-mg/kg dose-expansion cohort (n = 40), the objective response rate was 25%; the median response duration was 4.2 months (95% confidence interval, 2.6-6.7); and the median progression-free survival was 3.5 months (95% confidence interval, 1.5-4.2).

CONCLUSIONS

ABBV-011 1.0 mg/kg every 3 weeks monotherapy was well tolerated and demonstrated encouraging antitumor activity in heavily pretreated patients with relapsed/refractory SCLC. SEZ6 is a promising novel SCLC target and warrants further investigation.

Strategies to Target Chemoradiotherapy Resistance in Small Cell Lung Cancer

Background: Small cell lung cancer (SCLC) is a lethal form of lung cancer with few treatment options and a high rate of relapse. While SCLC is initially sensitive to first-line DNA-damaging chemo- and radiotherapy, relapse disease is almost universally therapy-resistant. As a result, there has been interest in understanding the mechanisms of therapeutic resistance in this disease. Conclusions: Progress has been made in elucidating these mechanisms, particularly as they relate to the DNA damage response and SCLC differentiation and transformation, leading to many clinical trials investigating new therapies and combinations. Yet there remain many gaps in our understanding, such as the effect of epigenetics or the tumor microenvironment on treatment response, and no single mechanism has been found to be ubiquitous, suggesting a significant heterogeneity in the mechanisms of acquired resistance. Nevertheless, the advancement of techniques in the laboratory and the clinic will improve our ability to study this disease, especially in patient populations, and identify methods to surmount therapeutic resistance.

ATR inhibition activates cancer cell cGAS/STING-interferon signaling and promotes antitumor immunity in small-cell lung cancer

Patients with small-cell lung cancer (SCLC) have poor prognosis and typically experience only transient benefits from combined immune checkpoint blockade (ICB) and chemotherapy. Here, we show that inhibition of ataxia telangiectasia and rad3 related (ATR), the primary replication stress response activator, induces DNA damage-mediated micronuclei formation in SCLC models. ATR inhibition in SCLC activates the stimulator of interferon genes (STING)-mediated interferon signaling, recruits T cells, and augments the antitumor immune response of programmed death-ligand 1 (PD-L1) blockade in mouse models. We demonstrate that combined ATR and PD-L1 inhibition causes improved antitumor response than PD-L1 alone as the second-line treatment in SCLC. This study shows that targeting ATR up-regulates major histocompatibility class I expression in preclinical models and SCLC clinical samples collected from a first-in-class clinical trial of ATR inhibitor, berzosertib, with topotecan in patients with relapsed SCLC. Targeting ATR represents a transformative vulnerability of SCLC and is a complementary strategy to induce STING-interferon signaling-mediated immunogenicity in SCLC.

GCN2 is a determinant of the response to WEE1 kinase inhibition in small-cell lung cancer

Patients with small-cell lung cancer (SCLC) are in dire need of more effective therapeutic options. Frequent disruption of the G1 checkpoint in SCLC cells creates a dependency on the G2/M checkpoint to maintain genomic integrity. Indeed, in pre-clinical models, inhibiting the G2/M checkpoint kinase WEE1 shows promise in inhibiting SCLC growth. However, toxicity and acquired resistance limit the clinical effectiveness of this strategy. Here, using CRISPR-Cas9 knockout screens in vitro and in vivo, we identified multiple factors influencing the response of SCLC cells to the WEE1 kinase inhibitor AZD1775, including the GCN2 kinase and other members of its signaling pathway. Rapid activation of GCN2 upon AZD1775 treatment triggers a stress response in SCLC cells. Pharmacological or genetic activation of the GCN2 pathway enhances cancer cell killing by AZD1775. Thus, activation of the GCN2 pathway represents a promising strategy to increase the efficacy of WEE1 inhibitors in SCLC.

Emerging advances in defining the molecular and therapeutic landscape of small-cell lung cancer

Small-cell lung cancer (SCLC) has traditionally been considered a recalcitrant cancer with a dismal prognosis, with only modest advances in therapeutic strategies over the past several decades. Comprehensive genomic assessments of SCLC have revealed that most of these tumours harbour deletions of the tumour-suppressor genes TP53 and RB1 but, in contrast to non-small-cell lung cancer, have failed to identify targetable alterations. The expression status of four transcription factors with key roles in SCLC pathogenesis defines distinct molecular subtypes of the disease, potentially enabling specific therapeutic approaches. Overexpression and amplification of MYC paralogues also affect the biology and therapeutic vulnerabilities of SCLC. Several other attractive targets have emerged in the past few years, including inhibitors of DNA-damage-response pathways, epigenetic modifiers, antibody-drug conjugates and chimeric antigen receptor T cells. However, the rapid development of therapeutic resistance and lack of biomarkers for effective selection of patients with SCLC are ongoing challenges. Emerging single-cell RNA sequencing data are providing insights into the plasticity and intratumoural and intertumoural heterogeneity of SCLC that might be associated with therapeutic resistance. In this Review, we provide a comprehensive overview of the latest advances in genomic and transcriptomic characterization of SCLC with a particular focus on opportunities for translation into new therapeutic approaches to improve patient outcomes.

Recent discovery and development of AXL inhibitors as antitumor agents

AXL, a receptor tyrosine kinase (RTK), plays a pivotal role in various cellular functions. It is primarily involved in processes such as epithelial-mesenchymal transition (EMT) in tumor cells, angiogenesis, apoptosis, immune regulation, and chemotherapy resistance mechanisms. Therefore, targeting AXL is a promising therapeutic approach for the treatment of cancer. AXL inhibitors that have entered clinical trials, such as BGB324(1), have shown promising efficacy in the treatment of melanoma and non-small cell lung cancer. Additionally, novel AXL-targeted drugs, such as AXL degraders, offer a potential solution to overcome the limitations of traditional small-molecule AXL inhibitors targeting single pathways. We provide an overview of the structure and biological functions of AXL, discusses its correlation with various cancers, and critically analyzes the structure-activity relationship of AXL small-molecule inhibitors in cellular contexts. Additionally, we summarize multiple research and development strategies, offering insights for the future development of innovative AXL inhibitors.

Adavosertib-encapsulated metal-organic frameworks for p53-mutated gallbladder cancer treatment via synthetic lethality

Adavosertib (ADA) is a WEE1 inhibitor that exhibits a synthetic lethal effect on p53-mutated gallbladder cancer (GBC). However, drug resistance due to DNA damage response compensation pathways and high toxicity limits further applications. Herein, estrone-targeted ADA-encapsulated metal-organic frameworks (ADA@MOF-EPL) for GBC synthetic lethal treatment by inducing conditional factors are developed. The high expression of estrogen receptors in GBC enables ADA@MOF-EPL to quickly enter and accumulate near the cell nucleus through estrone-mediated endocytosis and release ADA to inhibit WEE1 upon entering the acidic tumor microenvironment. Ultrasound irradiation induces ADA@MOF-EPL to generate reactive oxygen species (ROS), which leads to a further increase in DNA damage, resulting in a higher sensitivity of p53-mutated cancer cells to WEE1 inhibitor and promoting cell death via conditional synthetic lethality. The conditional factor induced by ADA@MOF-EPL further enhances the antitumor efficacy while significantly reducing systemic toxicity. Moreover, ADA@MOF-EPL demonstrates similar antitumor abilities in other p53-mutated solid tumors, revealing its potential as a broad-spectrum antitumor drug.

Targeting DHX9 Triggers Tumor-Intrinsic Interferon Response and Replication Stress in Small Cell Lung Cancer

Activating innate immunity in cancer cells through cytoplasmic nucleic acid sensing pathways, a phenomenon known as "viral mimicry," has emerged as an effective strategy to convert immunologically "cold" tumors into "hot." Through a curated CRISPR-based screen of RNA helicases, we identified DExD/H-box helicase 9 (DHX9) as a potent repressor of double-stranded RNA (dsRNA) in small cell lung cancers (SCLC). Depletion of DHX9 induced accumulation of cytoplasmic dsRNA and triggered tumor-intrinsic innate immunity. Intriguingly, ablating DHX9 also induced aberrant accumulation of R-loops, which resulted in an increase of DNA damage-derived cytoplasmic DNA and replication stress in SCLCs. In vivo, DHX9 deletion promoted a decrease in tumor growth while inducing a more immunogenic tumor microenvironment, invigorating responsiveness to immune-checkpoint blockade. These findings suggest that DHX9 is a crucial repressor of tumor-intrinsic innate immunity and replication stress, representing a promising target for SCLC and other "cold" tumors in which genomic instability contributes to pathology.

SIGNIFICANCE

One promising strategy to trigger an immune response within tumors and enhance immunotherapy efficacy is by inducing endogenous "virus-mimetic" nucleic acid accumulation. Here, we identify DHX9 as a viral-mimicry-inducing factor involved in the suppression of double-stranded RNAs and R-loops and propose DHX9 as a novel target to enhance antitumor immunity. See related commentary by Chiappinelli, p. 389. This article is featured in Selected Articles from This Issue, p. 384.

Promises of Protein Kinase Inhibitors in Recalcitrant Small-Cell Lung Cancer: Recent Scenario and Future Possibilities

SCLC is refractory to conventional therapies; targeted therapies and immunological checkpoint inhibitor (ICI) molecules have prolonged survival only marginally. In addition, ICIs help only a subgroup of SCLC patients. Different types of kinases play pivotal roles in therapeutics-driven cellular functions. Therefore, there is a significant need to understand the roles of kinases in regulating therapeutic responses, acknowledge the existing knowledge gaps, and discuss future directions for improved therapeutics for recalcitrant SCLC. Here, we extensively review the effect of dysregulated kinases in SCLC. We further discuss the pharmacological inhibitors of kinases used in targeted therapies for recalcitrant SCLC. We also describe the role of kinases in the ICI-mediated activation of antitumor immune responses. Finally, we summarize the clinical trials evaluating the potential of kinase inhibitors and ICIs. This review overviews dysregulated kinases in SCLC and summarizes their potential as targeted therapeutic agents. We also discuss their clinical efficacy in enhancing anticancer responses mediated by ICIs.

An update of predictive biomarkers related to WEE1 inhibition in cancer therapy

PURPOSE

WEE1 is a crucial kinase involved in the regulation of G2/M checkpoint within the cell cycle. This article aims to comprehensively review the existing knowledge on the implication of WEE1 as a therapeutic target in tumor progression and drug resistance. Furthermore, we summarize the current predictive biomarkers employed to treat cancer with WEE1 inhibitors.

METHODS

A systematic review of the literature was conducted to analyze the association between WEE1 inhibition and cancer progression, including tumor advancement and drug resistance. Special attention was paid to the identification and utilization of predictive biomarkers related to therapeutic response to WEE1 inhibitors.

RESULTS

The review highlights the intricate involvement of WEE1 in tumor progression and drug resistance. It synthesizes the current knowledge on predictive biomarkers employed in WEE1 inhibitor treatments, offering insights into their prognostic significance. Notably, the article elucidates the potential for precision medicine by understanding these biomarkers in the context of tumor treatment outcomes.

CONCLUSION

WEE1 plays a pivotal role in tumor progression and is a promising therapeutic target. Distinguishing patients that would benefit from WEE1 inhibition will be a major direction of future research.

Adavosertib and beyond: Biomarkers, drug combination and toxicity of WEE1 inhibitors

WEE1 kinase is renowned as an S-G2 checkpoint inhibitor activated by ATR-CHK1 in response to replication stress. WEE1 inhibition enhances replication stress and effectively circumvents checkpoints into mitosis, which triggers significant genetic impairs and culminates in cell death. This approach has been validated clinically for its promising anti-tumor efficacy across various cancer types, notably in cases of ovarian cancers. Nonetheless, the initial stage of clinical trials has shown that the first-in-human WEE1 inhibitor adavosertib is limited by dose-limiting adverse events. As a result, recent efforts have been made to explore predictive biomarkers and smart combination schedules to alleviate adverse effects. In this review, we focused on the exploration of therapeutic biomarkers, as well as schedules of combination utilizing WEE1 inhibitors and canonical anticancer drugs, according to the latest preclinical and clinical studies, indicating that the optimal application of WEE1 inhibitors will likely be as part of dose-reducing combination and be tailored to specific patient populations.

Structure-based drug discovery of novel fused-pyrazolone carboxamide derivatives as potent and selective AXL inhibitors

As a novel and promising antitumor target, AXL plays an important role in tumor growth, metastasis, immunosuppression and drug resistance of various malignancies, which has attracted extensive research interest in recent years. In this study, by employing the structure-based drug design and bioisosterism strategies, we designed and synthesized in total 54 novel AXL inhibitors featuring a fused-pyrazolone carboxamide scaffold, of which up to 20 compounds exhibited excellent AXL kinase and BaF3/TEL-AXL cell viability inhibitions. Notably, compound 59 showed a desirable AXL kinase inhibitory activity (IC50: 3.5 nmol/L) as well as good kinase selectivity, and it effectively blocked the cellular AXL signaling. In turn, compound 59 could potently inhibit BaF3/TEL-AXL cell viability (IC50: 1.5 nmol/L) and significantly suppress GAS6/AXL-mediated cancer cell invasion, migration and wound healing at the nanomolar level. More importantly, compound 59 oral administration showed good pharmacokinetic profile and in vivo antitumor efficiency, in which we observed significant AXL phosphorylation suppression, and its antitumor efficacy at 20 mg/kg (qd) was comparable to that of BGB324 at 50 mg/kg (bid), the most advanced AXL inhibitor. Taken together, this work provided a valuable lead compound as a potential AXL inhibitor for the further antitumor drug development.

Myt1 overexpression mediates resistance to cell cycle and DNA damage checkpoint kinase inhibitors

Cell cycle checkpoint kinases serve as important therapeutic targets for various cancers. When they are inhibited by small molecules, checkpoint abrogation can induce cell death or further sensitize cancer cells to other genotoxic therapies. Particularly aberrant Cdk1 activation at the G2/M checkpoint by kinase inhibitors causing unscheduled mitotic entry and mitotic arrest was found to lead to DNA damage and cell death selectively in cancer cells. Promising drugs inhibiting kinases like Wee1 (Adavosertib), Wee1+Myt1 (PD166285), ATR (AZD6738) and Chk1 (UCN-01) have been developed, but clinical data has shown variable efficacy for them with poorly understood mechanisms of resistance. Our lab recently identified Myt1 as a predictive biomarker of acquired resistance to the Wee1 kinase inhibitor, Adavosertib. Here, we investigate the role of Myt1 overexpression in promoting resistance to inhibitors (PD166285, UCN-01 and AZD6738) of other kinases regulating cell cycle progression. We demonstrate that Myt1 confers resistance by compensating Cdk1 inhibition in the presence of these different kinase inhibitors. Myt1 overexpression leads to reduced premature mitotic entry and decreased length of mitosis eventually leading to increased survival rates in Adavosertib treated cells. Elevated Myt1 levels also conferred resistance to inhibitors of ATR or Chk1 inhibitor. Our data supports that Myt1 overexpression is a common mechanism by which cancer cells can acquire resistance to a variety of drugs entering the clinic that aim to induce mitotic catastrophe by abrogating the G2/M checkpoint.

TAM family kinases as therapeutic targets at the interface of cancer and immunity

Novel treatment approaches are needed to overcome innate and acquired mechanisms of resistance to current anticancer therapies in cancer cells and the tumour immune microenvironment. The TAM (TYRO3, AXL and MERTK) family receptor tyrosine kinases (RTKs) are potential therapeutic targets in a wide range of cancers. In cancer cells, TAM RTKs activate signalling pathways that promote cell survival, metastasis and resistance to a variety of chemotherapeutic agents and targeted therapies. TAM RTKs also function in innate immune cells, contributing to various mechanisms that suppress antitumour immunity and promote resistance to immune-checkpoint inhibitors. Therefore, TAM antagonists provide an unprecedented opportunity for both direct and immune-mediated therapeutic activity provided by inhibition of a single target, and are likely to be particularly effective when used in combination with other cancer therapies. To exploit this potential, a variety of agents have been designed to selectively target TAM RTKs, many of which have now entered clinical testing. This Review provides an essential guide to the TAM RTKs for clinicians, including an overview of the rationale for therapeutic targeting of TAM RTKs in cancer cells and the tumour immune microenvironment, a description of the current preclinical and clinical experience with TAM inhibitors, and a perspective on strategies for continued development of TAM-targeted agents for oncology applications.

Smoking induces WEE1 expression to promote docetaxel resistance in esophageal adenocarcinoma

Esophageal adenocarcinoma (EAC) patients have poor clinical outcomes, with an overall 5-year survival rate of 20%. Smoking is a significant risk factor for EAC. The role of WEE1, a nuclear kinase that negatively regulates the cell cycle in normal conditions, in EAC tumorigenesis and drug resistance is not fully understood. Immunohistochemistry staining shows significant WEE1 overexpression in human EAC tissues. Nicotine, nicotine-derived nitrosamine ketone, or 2% cigarette smoke extract treatment induces WEE1 protein expression in EAC, detected by western blot and immunofluorescence staining. qRT-PCR and reporter assay indicates that smoking induces WEE1 expression through miR-195-5p downregulation in EAC. ATP-Glo cell viability and clonogenic assay confirmed that WEE1 inhibition sensitizes EAC cells to docetaxel treatment in vitro. A TE-10 smoking machine with EAC patient-derived xenograft mouse model demonstrated that smoking induces WEE1 protein expression and resistance to docetaxel in vivo. MK-1775 and docetaxel combined treatment improves EAC patient-derived xenograft mouse survival in vivo. Our findings demonstrate, for the first time, that smoking-induced WEE1 overexpression through miRNA dysregulation in EAC plays an essential role in EAC drug resistance. WEE1 inhibition is a promising therapeutic method to overcome drug resistance and target treatment refractory cancer cells.

Potent molecular-targeted therapies for gastro-entero-pancreatic neuroendocrine carcinoma

Neuroendocrine neoplasms (NENs), which are characterized by neuroendocrine differentiation, can arise in various organs. NENs have been divided into well-differentiated neuroendocrine tumors (NETs) and poorly differentiated neuroendocrine carcinomas (NECs) based on morphological differentiation, each of which has a distinct etiology, molecular profile, and clinicopathological features. While the majority of NECs originate in the pulmonary organs, extrapulmonary NECs occur most predominantly in the gastro-entero-pancreatic (GEP) system. Although platinum-based chemotherapy is the main therapeutic option for recurrent or metastatic GEP-NEC patients, the clinical benefits are limited and associated with a poor prognosis, indicating the clinically urgent need for effective therapeutic agents. The clinical development of molecular-targeted therapies has been hampered due to the rarity of GEP-NECs and the paucity of knowledge on their biology. In this review, we summarize the biology, current treatments, and molecular profiles of GEP-NECs based on the findings of pivotal comprehensive molecular analyses; we also highlight potent therapeutic targets for future precision medicine based on the most recent results of clinical trials.

Orchestrating smart therapeutics to achieve optimal treatment in small cell lung cancer: recent progress and future directions

Small cell lung cancer (SCLC) is a recalcitrant malignancy with elusive mechanism of pathogenesis and dismal prognosis. Over the past decades, platinum-based chemotherapy has been the backbone treatment for SCLC. However, subsequent chemoresistance after initial effectiveness urges researchers to explore novel therapeutic targets of SCLC. Recent years have witnessed significant improvements in targeted therapy in SCLC. New molecular candidates such as Ataxia telangiectasia and RAD3-related protein (ATR), WEE1, checkpoint kinase 1 (CHK1) and poly-ADP-ribose polymerase (PARP) have shown promising therapeutic utility in SCLC. While immune checkpoint inhibitor (ICI) has emerged as an indispensable treatment modality for SCLC, approaches to boost efficacy and reduce toxicity as well as selection of reliable biomarkers for ICI in SCLC have remained elusive and warrants our further investigation. Given the increasing importance of precision medicine in SCLC, optimal subtyping of SCLC using multi-omics have gradually applied into clinical practice, which may identify more drug targets and better tailor treatment strategies to each individual patient. The present review summarizes recent progress and future directions in SCLC. In addition to the emerging new therapeutics, we also focus on the establishment of predictive model for early detection of SCLC. More importantly, we also propose a multi-dimensional model in the prognosis of SCLC to ultimately attain the goal of accurate treatment of SCLC.

The effect of inhibition of receptor tyrosine kinase AXL on DNA damage response in ovarian cancer

AXL is a receptor tyrosine kinase that is often overexpressed in cancers. It contributes to pathophysiology in cancer progression and therapeutic resistance, making it an emerging therapeutic target. The first-in-class AXL inhibitor bemcentinib (R428/BGB324) has been granted fast track designation by the U.S. Food and Drug Administration (FDA) in STK11-mutated advanced metastatic non-small cell lung cancer and was also reported to show selective sensitivity towards ovarian cancers (OC) with a Mesenchymal molecular subtype. In this study, we further explored AXL's role in mediating DNA damage responses by using OC as a disease model. AXL inhibition using R428 resulted in the increase of DNA damage with the concurrent upregulation of DNA damage response signalling molecules. Furthermore, AXL inhibition rendered cells more sensitive to the inhibition of ATR, a crucial mediator for replication stress. Combinatory use of AXL and ATR inhibitors showed additive effects in OC. Through SILAC co-immunoprecipitation mass spectrometry, we identified a novel binding partner of AXL, SAM68, whose loss in OC cells harboured phenotypes in DNA damage responses similar to AXL inhibition. In addition, AXL- and SAM68-deficiency or R428 treatment induced elevated levels of cholesterol and upregulated genes in the cholesterol biosynthesis pathway. There might be a protective role of cholesterol in shielding cancer cells against DNA damage induced by AXL inhibition or SMA68 deficiency.

AXL in cancer: a modulator of drug resistance and therapeutic target

AXL is a member of the TAM (TYRO3, AXL, and MERTK) receptor tyrosine kinases family (RTKs), and its abnormal expression has been linked to clinicopathological features and poor prognosis of cancer patients. There is mounting evidence supporting AXL's role in the occurrence and progression of cancer, as well as drug resistance and treatment tolerance. Recent studies revealed that reducing AXL expression can weaken cancer cells' drug resistance, indicating that AXL may be a promising target for anti-cancer drug treatment. This review aims to summarize the AXL's structure, the mechanisms regulating and activating it, and its expression pattern, especially in drug-resistant cancers. Additionally, we will discuss the diverse functions of AXL in mediating cancer drug resistance and the potential of AXL inhibitors in cancer treatment.

Synthetic and Medicinal Chemistry Approaches Toward WEE1 Kinase Inhibitors and Its Degraders

WEE1 is a checkpoint kinase critical for mitotic events, especially in cell maturation and DNA repair. Most cancer cells' progression and survival are linked with elevated levels of WEE1 kinase. Thus, WEE1 kinase has become a new promising druggable target. A few classes of WEE1 inhibitors are designed by rationale or structure-based techniques and optimization approaches to identify selective acting anticancer agents. The discovery of the WEE1 inhibitor AZD1775 further emphasized WEE1 as a promising anticancer target. Therefore, the current review provides a comprehensive data on medicinal chemistry, synthetic approaches, optimization methods, and the interaction profile of WEE1 kinase inhibitors. In addition, WEE1 PROTAC degraders and their synthetic procedures, including a list of noncoding RNAs necessary for regulation of WEE1, are also highlighted. From the standpoint of medicinal chemistry, the contents of this compilation serve as an exemplar for the further design, synthesis, and optimization of promising WEE1-targeted anticancer agents.

Inhibiting WEE1 Augments the Antitumor Efficacy of Cisplatin in Urothelial Carcinoma by Enhancing the DNA Damage Process

Urothelial carcinoma (UC) is characterized by a high incidence of TP53 mutation, and overcoming resistance to cisplatin-based chemotherapy in UC is a major concern. Wee1 is a G2/M phase regulator that controls the DNA damage response to chemotherapy in TP53-mutant cancers. The combination of Wee1 blockade with cisplatin has shown synergistic efficacy in several types of cancers, but little is known regarding UC. The antitumor efficacy of the Wee1 inhibitor (AZD-1775) alone or in combination with cisplatin was evaluated in UC cell lines and a xenograft mouse model. AZD-1775 enhanced the anticancer activity of cisplatin by increasing cellular apoptosis. AZD-1775 inhibited the G2/M checkpoint, improving the sensitivity of mutant TP53 UC cells to cisplatin by enhancing the DNA damage process. We confirmed that AZD-1775 combined with cisplatin reduced tumor volume and proliferation activity and increased the markers of cell apoptosis and DNA damage in the mouse xenograft model. In summary, the Wee1 inhibitor AZD-1775 combined with cisplatin elicited a promising anticancer efficacy in UC, and constitutes an innovative and promising therapeutic strategy.

Gas6/AXL pathway: immunological landscape and therapeutic potential

Cancer is a disease with ecological and evolutionary unity, which seriously affects the survival and quality of human beings. Currently, many reports have suggested Gas6 plays an important role in cancer. Binding of gas6 to TAM receptors is associated with the carcinogenetic mechanisms of multiple malignancies, such as in breast cancer, chronic lymphocytic leukemia, non-small cell lung cancer, melanoma, prostate cancer, etc., and shortened overall survival. It is accepted that the Gas6/TAM pathway can promote the malignant transformation of various types of cancer cells. Gas6 has the highest affinity for Axl, an important member of the TAM receptor family. Knockdown of the TAM receptors Axl significantly affects cell cycle progression in tumor cells. Interestingly, Gas6 also has an essential function in the tumor microenvironment. The Gas6/AXL pathway regulates angiogenesis, immune-related molecular markers and the secretion of certain cytokines in the tumor microenvironment, and also modulates the functions of a variety of immune cells. In addition, evidence suggests that the Gas6/AXL pathway is involved in tumor therapy resistance. Recently, multiple studies have begun to explore in depth the importance of the Gas6/AXL pathway as a potential tumor therapeutic target as well as its broad promise in immunotherapy; therefore, a timely review of the characteristics of the Gas6/AXL pathway and its value in tumor treatment strategies is warranted. This comprehensive review assessed the roles of Gas6 and AXL receptors and their associated pathways in carcinogenesis and cancer progression, summarized the impact of Gas6/AXL on the tumor microenvironment, and highlighted the recent research progress on the relationship between Gas6/AXL and cancer drug resistance.

A multiplexed in vivo approach to identify driver genes in small cell lung cancer

Small cell lung cancer (SCLC) is a lethal form of lung cancer. Here, we develop a quantitative multiplexed approach on the basis of lentiviral barcoding with somatic CRISPR-Cas9-mediated genome editing to functionally investigate candidate regulators of tumor initiation and growth in genetically engineered mouse models of SCLC. We found that naphthalene pre-treatment enhances lentiviral vector-mediated SCLC initiation, enabling high multiplicity of tumor clones for analysis through high-throughput sequencing methods. Candidate drivers of SCLC identified from a meta-analysis across multiple human SCLC genomic datasets were tested using this approach, which defines both positive and detrimental impacts of inactivating 40 genes across candidate pathways on SCLC development. This analysis and subsequent validation in human SCLC cells establish TSC1 in the PI3K-AKT-mTOR pathway as a robust tumor suppressor in SCLC. This approach should illuminate drivers of SCLC, facilitate the development of precision therapies for defined SCLC genotypes, and identify therapeutic targets.

ODF2L acts as a synthetic lethal partner with WEE1 inhibition in epithelial ovarian cancer models

WEE1 has emerged as an attractive target in epithelial ovarian cancer (EOC), but how EOC cells may alter their sensitivity to WEE1 inhibition remains unclear. Here, through a cell cycle machinery-related gene RNAi screen, we found that targeting outer dense fiber of sperm tails 2-like (ODF2L) was a synthetic lethal partner with WEE1 kinase inhibition in EOC cells. Knockdown of ODF2L robustly sensitized cells to treatment with the WEE1 inhibitor AZD1775 in EOC cell lines in vitro as well as in xenografts in vivo. Mechanistically, the increased sensitivity to WEE1 inhibition upon ODF2L loss was accompanied by accumulated DNA damage. ODF2L licensed the recruitment of PKMYT1, a functionally redundant kinase of WEE1, to the CDK1-cyclin B complex and thus restricted the activity of CDK1 when WEE1 was inhibited. Clinically, upregulation of ODF2L correlated with CDK1 activity, DNA damage levels, and sensitivity to WEE1 inhibition in patient-derived EOC cells. Moreover, ODF2L levels predicted the response to WEE1 inhibition in an EOC patient-derived xenograft model. Combination treatment with tumor-targeted lipid nanoparticles that packaged ODF2L siRNA and AZD1775 led to the synergistic attenuation of tumor growth in the ID8 ovarian cancer syngeneic mouse model. These data suggest that WEE1 inhibition is a promising precision therapeutic strategy for EOC cells expressing low levels of ODF2L.

Discovery of 3-Aminopyrazole Derivatives as New Potent and Orally Bioavailable AXL Inhibitors

The receptor tyrosine kinase AXL is a promising target for anticancer drug discovery. Herein, we describe the discovery of 3-aminopyrazole derivatives as new potent and selective AXL kinase inhibitors. One of the representative compounds, 6li, potently inhibited AXL enzymatic activity with an IC50 value of 1.6 nM, and tightly bound with AXL protein with a Kd value of 0.26 nM, while was obviously less potent against most of the 403 wild-type kinases evaluated. Cell-based assays demonstrated that compound 6li potently inhibited AXL signaling, suppressed Ba/F3-TEL-AXL cell proliferation, reversed TGF-β1-induced epithelial-mesenchymal transition, and dose-dependently impeded cancer cell migration and invasion. Compound 6li also showed reasonable pharmacokinetic properties in rats and exhibited significant in vivo antitumor efficacy in a xenograft model of highly metastatic murine breast cancer 4T1 cells. Taken together, this study provides a new potent and selective AXL inhibitor for further anticancer drug discovery.

Small cell lung cancer: Novel treatments beyond immunotherapy

Small cell lung cancer (SCLC) arises in peribronchial locations and infiltrates the bronchial submucosa, including about 15% of lung cancer cases. Despite decades of research, the prognosis for SCLC patients remains poor because this tumor is characterized by an exceptionally high proliferative rate, strong tendency for early widespread metastasis and acquired chemoresistance. Omics profiling revealed that SCLC harbor extensive chromosomal rearrangements and a very high mutation burden. This led to the development of immune-checkpoint inhibitors as single agents or in combination with chemotherapy, which however resulted in a prolonged benefit only for a small subset of patients. Thus, the present review discusses the rationale and limitations of immunotherapeutic approaches, presenting the current biological understanding of aberrant signaling pathways that might be exploited with new potential treatments. In particular, new agents targeting DNA damage repair, cell cycle checkpoint, and apoptosis pathways showed several promising results in different preclinical models. Epigenetic alterations, gene amplifications and mutations can act as biomarkers in this context. Future research and improved clinical outcome for SCLC patients will depend on the integration between these omics and pharmacological studies with clinical translational research, in order to identify specific predictive biomarkers that will be hopefully validated using clinical trials with biomarker-selected targeted treatments.

Current Landscape of Therapeutic Resistance in Lung Cancer and Promising Strategies to Overcome Resistance

Lung cancer is one of the leading causes of cancer-related deaths worldwide with a 5-year survival rate of less than 18%. Current treatment modalities include surgery, chemotherapy, radiation therapy, targeted therapy, and immunotherapy. Despite advances in therapeutic options, resistance to therapy remains a major obstacle to the effectiveness of long-term treatment, eventually leading to therapeutic insensitivity, poor progression-free survival, and disease relapse. Resistance mechanisms stem from genetic mutations and/or epigenetic changes, unregulated drug efflux, tumor hypoxia, alterations in the tumor microenvironment, and several other cellular and molecular alterations. A better understanding of these mechanisms is crucial for targeting factors involved in therapeutic resistance, establishing novel antitumor targets, and developing therapeutic strategies to resensitize cancer cells towards treatment. In this review, we summarize diverse mechanisms driving resistance to chemotherapy, radiotherapy, targeted therapy, and immunotherapy, and promising strategies to help overcome this therapeutic resistance.

Novel therapeutic combinations with PARP inhibitors for small cell lung cancer: A bench-to-bedside review

Small cell lung cancer (SCLC) is treated as a monolithic disease despite the evident intra- and intertumoral heterogeneity. Non-specific DNA-damaging agents have remained the first-line treatment for decades. Recently, emerging transcriptomic and genomic profiling of SCLC tumors identified distinct SCLC subtypes and vulnerabilities towards targeted therapeutics, including inhibitors of the nuclear enzyme poly (ADP-ribose) polymerase (PARPi). SCLC cell lines and tumors exhibited an elevated level of PARP1 protein and mRNA compared to healthy lung tissues and other subtypes of lung tumors. Notable responses to PARPi were also observed in preclinical SCLC models. Clinically, PARPi monotherapy exerted variable benefits for SCLC patients. To date, research is being vigorously conducted to examine predictive biomarkers of PARPi response and various PARPi combination strategies to maximize the clinical utility of PARPi. This narrative review summarizes existing preclinical evidence supporting PARPi monotherapy, combination therapy, and respective translation to the clinic. Specifically, we covered the combination of PARPi with DNA-damaging chemotherapy (cisplatin, etoposide, temozolomide), thoracic radiotherapy, immunotherapy (immune checkpoint inhibitors), and many other novel therapeutic agents that target DNA damage response, tumor microenvironment, epigenetic modulation, angiogenesis, the ubiquitin-proteasome system, or autophagy. Putative biomarkers, such as SLFN11 expression, MGMT methylation, E2F1 expression, and platinum sensitivity, which may be predictive of response to distinct therapeutic combinations, were also discussed. The future of SCLC treatment is undergoing rapid change with a focus on tailored and personalized treatment strategies. Further development of cancer therapy with PARPi will immensely benefit at least a subset of biomarker-defined SCLC patients.

Signal pathways and precision therapy of small-cell lung cancer

Small-cell lung cancer (SCLC) encounters up 15% of all lung cancers, and is characterized by a high rate of proliferation, a tendency for early metastasis and generally poor prognosis. Most of the patients present with distant metastatic disease at the time of clinical diagnosis, and only one-third are eligible for potentially curative treatment. Recently, investigations into the genomic make-up of SCLC show extensive chromosomal rearrangements, high mutational burden and loss-of-function mutations of several tumor suppressor genes. Although the clinical development of new treatments for SCLC has been limited in recent years, a better understanding of oncogenic driver alterations has found potential novel targets that might be suitable for therapeutic approaches. Currently, there are six types of potential treatable signaling pathways in SCLC, including signaling pathways targeting the cell cycle and DNA repair, tumor development, cell metabolism, epigenetic regulation, tumor immunity and angiogenesis. At this point, however, there is still a lack of understanding of their role in SCLC tumor biology and the promotion of cancer growth. Importantly optimizing drug targets, improving drug pharmacology, and identifying potential biomarkers are the main focus and further efforts are required to recognize patients who benefit most from novel therapies in development. This review will focus on the current learning on the signaling pathways, the status of immunotherapy, and targeted therapy in SCLC.

Targeting HER2-AXL heterodimerization to overcome resistance to HER2 blockade in breast cancer

Anti-HER2 therapies have markedly improved prognosis of HER2-positive breast cancer. However, different mechanisms play a role in treatment resistance. Here, we identified AXL overexpression as an essential mechanism of trastuzumab resistance. AXL orchestrates epithelial-to-mesenchymal transition and heterodimerizes with HER2, leading to activation of PI3K/AKT and MAPK pathways in a ligand-independent manner. Genetic depletion and pharmacological inhibition of AXL restored trastuzumab response in vitro and in vivo. AXL inhibitor plus trastuzumab achieved complete regression in trastuzumab-resistant patient-derived xenograft models. Moreover, AXL expression in HER2-positive primary tumors was able to predict prognosis. Data from the PAMELA trial showed a change in AXL expression during neoadjuvant dual HER2 blockade, supporting its role in resistance. Therefore, our study highlights the importance of targeting AXL in combination with anti-HER2 drugs across HER2-amplified breast cancer patients with high AXL expression. Furthermore, it unveils the potential value of AXL as a druggable prognostic biomarker in HER2-positive breast cancer.

WEE1 inhibition enhances the antitumor immune response to PD-L1 blockade by the concomitant activation of STING and STAT1 pathways in SCLC

Small cell lung cancers (SCLCs) have high mutational burden but are relatively unresponsive to immune checkpoint blockade (ICB). Using SCLC models, we demonstrate that inhibition of WEE1, a G2/M checkpoint regulator induced by DNA damage, activates the STING-TBK1-IRF3 pathway, which increases type I interferons (IFN-α and IFN-β) and pro-inflammatory chemokines (CXCL10 and CCL5), facilitating an immune response via CD8⁺ cytotoxic T cell infiltration. We further show that WEE1 inhibition concomitantly activates the STAT1 pathway, increasing IFN-γ and PD-L1 expression. Consistent with these findings, combined WEE1 inhibition (AZD1775) and PD-L1 blockade causes remarkable tumor regression, activation of type I and II interferon pathways, and infiltration of cytotoxic T cells in multiple immunocompetent SCLC genetically engineered mouse models, including an aggressive model with stabilized MYC. Our study demonstrates cell-autonomous and immune-stimulating activity of WEE1 inhibition in SCLC models. Combined inhibition of WEE1 plus PD-L1 blockade represents a promising immunotherapeutic approach in SCLC.

RAS-mediated tumor stress adaptation and the targeting opportunities it presents

Cellular stress is known to function in synergistic cooperation with oncogenic mutations during tumorigenesis to drive cancer progression. Oncogenic RAS is a strong inducer of a variety of pro-tumorigenic cellular stresses, and also enhances the ability of cells to tolerate these stresses through multiple mechanisms. Many of these oncogenic, RAS-driven, stress-adaptive mechanisms have also been implicated in tolerance and resistance to chemotherapy and to therapies that target the RAS pathway. Understanding how oncogenic RAS shapes cellular stress adaptation and how this functions in drug resistance is of vital importance for identifying new therapeutic targets and therapeutic combinations to treat RAS-driven cancers.

Multimodal platform for assessing drug distribution and response in clinical trials

BACKGROUND

Response to targeted therapy varies between patients for largely unknown reasons. Here, we developed and applied an integrative platform using mass spectrometry imaging (MSI), phosphoproteomics, and multiplexed tissue imaging for mapping drug distribution, target engagement, and adaptive response to gain insights into heterogeneous response to therapy.

METHODS

Patient-derived xenograft (PDX) lines of glioblastoma were treated with adavosertib, a Wee1 inhibitor, and tissue drug distribution was measured with MALDI-MSI. Phosphoproteomics was measured in the same tumors to identify biomarkers of drug target engagement and cellular adaptive response. Multiplexed tissue imaging was performed on sister sections to evaluate spatial co-localization of drug and cellular response. The integrated platform was then applied on clinical specimens from glioblastoma patients enrolled in the phase 1 clinical trial.

RESULTS

PDX tumors exposed to different doses of adavosertib revealed intra- and inter-tumoral heterogeneity of drug distribution and integration of the heterogeneous drug distribution with phosphoproteomics and multiplexed tissue imaging revealed new markers of molecular response to adavosertib. Analysis of paired clinical specimens from patients enrolled in the phase 1 clinical trial informed the translational potential of the identified biomarkers in studying patient's response to adavosertib.

CONCLUSIONS

The multimodal platform identified a signature of drug efficacy and patient-specific adaptive responses applicable to preclinical and clinical drug development. The information generated by the approach may inform mechanisms of success and failure in future early phase clinical trials, providing information for optimizing clinical trial design and guiding future application into clinical practice.

PKMYT1, exacerbating the progression of clear cell renal cell carcinoma, is implied as a biomarker for the diagnosis and prognosis

Clear cell renal cell carcinoma (ccRCC) is one of the most lethal urological malignancies with high tumor heterogeneity, and reliable biomarkers are still needed for its diagnosis and prognosis. WEE family kinases function as key regulators of the G2/M transition, have essential roles in maintaining cellular genomic stability and have the potential to be promising therapeutic targets in various tumors. However, the roles of WEE family kinases in ccRCC remain undetermined. In the present study, we first explored multiple public datasets and found that PKMYT1 was up-regulated in both RCC tumors and cell lines. Expression levels of PKMYT1 were highly associated with pathological stage and grade. Kaplan-Meier curves showed that high PKMYT1 expression was associated with lower overall survival and disease-free survival. Receiver operating characteristic curves revealed that the expression of PKMYT1 could better distinguish ccRCC from normal samples. Functional enrichment analysis demonstrated that cell cycle- related pathways and epithelial to mesenchymal transition (EMT) might be potential mechanisms of PKMYT1 in ccRCC tumorigenesis. Moreover, knockdown of PKMYT1 in vitro attenuated the proliferation, migration and invasion of RCC cell lines, promoted cell apoptosis and prevented the EMT phenotype in vitro. In conclusion, our study demonstrated that PKMYT1 has the potential to act as a diagnostic and prognostic biomarker for RCC patients. Targeting PKMYT1 may be considered as a new potential therapeutic method and direction in RCCs.

Overcoming PLK1 inhibitor resistance by targeting mevalonate pathway to impair AXL-TWIST axis in colorectal cancer

New therapeutic targets are revolutionizing colorectal cancer clinical management, opening new horizons in metastatic patients' outcome. Polo Like Kinase1 (PLK1) inhibitors have high potential as antitumoral agents, however, the emergence of drug resistance is a major challenge for their use in clinical practice. Overcoming this challenge represents a hot topic in current drug discovery research. BI2536-resistant colorectal cancer cell lines HT29R, RKOR, SW837R and HCT116R, were generated in vitro and validated by IG50 assays and xenografts models by the T/C ratio. Exons 1 and 2 of PLK1 gene were sequenced by Sanger method. AXL pathway, Epithelial-to-Mesenchymal transition (EMT) and Multidrug Resistance (MDR1) were studied by qPCR and western blot in resistant cells. Simvastatin as a re-sensitizer drug was tested in vitro and the drug combination strategies were validated in vitro and in vivo. PLK1 gene mutation R136G was found for RKOR. AXL pathway trough TWIST1 transcription factor was identified as one of the mechanisms involved in HT29R, SW837R and HCT116R lines, inducing EMT and upregulation of MDR1. Simvastatin was able to impair the mechanisms activated by adaptive resistance and its combination with BI2536 re-sensitized resistant cells in vitro and in vivo. Targeting the mevalonate pathway contributes to re-sensitizing BI2536-resistant cells in vitro and in vivo, raising as a new strategy for the clinical management of PLK1 inhibitors.

Targeting MERTK and AXL in EGFR Mutant Non-Small Cell Lung Cancer

MERTK and AXL are members of the TAM family of receptor tyrosine kinases and are abnormally expressed in 69% and 93% of non-small cell lung cancers (NSCLCs), respectively. Expression of MERTK and/or AXL provides a survival advantage for NSCLC cells and correlates with lymph node metastasis, drug resistance, and disease progression in patients with NSCLC. The TAM receptors on host tumor infiltrating cells also play important roles in the immunosuppressive tumor microenvironment. Thus, MERTK and AXL are attractive biologic targets for NSCLC treatment. Here, we will review physiologic and oncologic roles for MERTK and AXL with an emphasis on the potential to target these kinases in NSCLCs with activating EGFR mutations.

BRCA1 Expression and Outcome in Patients With EGFR-Mutant NSCLC Treated With Gefitinib Alone or in Combination With Olaparib

Introduction

DNA repair capacity, as exemplified by BRCA1 gene expression, is related with outcome to EGFR tyrosine kinase inhibitors in patients with EGFR-mutant NSCLC. Olaparib, a PARP inhibitor, reduces BRCA1 expression. Olaparib was tested in combination with gefitinib versus gefitinib single agent, as a first-line therapy for patients with EGFR-mutant NSCLC in the GOAL study (trial registration: NCT01513174). Here, we report the results of the biomarker-related prespecified secondary objectives of the GOAL study.

Methods

We evaluated the impact of BRCA1 mRNA expression in 91 patients with EGFR-mutant NSCLC. Of those 91 patients, 51 were randomized to treatment with gefitinib and 40 were randomized to treatment with gefitinib plus olaparib. We explored in vitro whether BRCA1 mRNA levels are related with outcome to gefitinib plus olaparib. The expression levels of 53BP1, CtIP, and AXL were also explored and correlated with the treatment outcome.

Results

Overall, as what happened in the GOAL study, no statistically significant difference was observed in median progression-free survival (PFS) between the two treatment arms, for the 91 patients of the present study (p = 0.2419). For patients with high BRCA1 mRNA expression (BRCA1-high group), median PFS was 12.9 months in the gefitinib plus olaparib arm, compared with 9.2 months in the gefitinib arm (p = 0.0449). In the gefitinib arm, median PFS was 9.1 months for the BRCA1-high group and 10.2 months for the BRCA1-low group (p = 0.0193). We observed a more pronounced synergism of gefitinib plus olaparib in cells with higher BRCA1 compared with those with low BRCA1 mRNA expression.

Conclusions

High BRCA1 mRNA expression identified patients with NSCLC who benefited from gefitinib plus olaparib in the GOAL phase 2 clinical trial.