Activating EGFR (epidermal growth factor receptor) mutations can be inhibited by specific tyrosine kinase inhibitors (TKIs), which have changed the landscape of lung cancer therapy. However, due to secondary mutations and bypass receptors, such as AXL (AXL receptor tyrosine kinase), drug resistance eventually emerges in most patients treated with the first-, second-, or third-generation TKIs (e.g., osimertinib). To inhibit AXL and resistance to osimertinib, we compare two anti-AXL drugs, an antibody (mAb654) and a TKI (bemcentinib). While no pair of osimertinib and an anti-AXL drug is able to prevent relapses, triplets combining osimertinib, cetuximab (an anti-EGFR antibody), and either anti-AXL drug are initially effective. However, longer monitoring uncovers superiority of the mAb654-containing triplet, possibly due to induction of receptor endocytosis, activation of immune mechanisms, or disabling intrinsic mutators. Hence, we constructed a bispecific antibody that engages both AXL and EGFR. When combined with osimertinib, the bispecific antibody consistently inhibits tumor relapses, which warrants clinical trials.

White matter injury (WMI) subsequent to subarachnoid hemorrhage (SAH) frequently leads to an unfavorable patient prognosis. Previous studies have indicated that microglial M1 polarization following SAH results in the accumulation of amyloid precursor protein (APP) and degradation of myelin basic protein (MBP), thereby catalyzing the exacerbation of WMI. Consequently, transitioning microglial polarization towards the M2 phenotype (neuroprotective state) represents a potential therapeutic approach for reversing WMI. The SIRT2 gene is pivotal in neurological disorders such as neurodegeneration and ischemic stroke. However, its function and underlying mechanisms in SAH, particularly how it influences microglial function to ameliorate WMI, remain unclear. Our investigations revealed that in post-SAH, there was a temporal increase in SIRT2 expression, predominantly in the cerebral corpus callosum area, with notable colocalization with microglia. However, following the administration of the SIRT2 inhibitor AK-7, a shift in microglial polarization towards the M2 phenotype and an improvement in both short-term and long-term neuronal functions in rats were observed. Mechanistically, CO-IP experiments confirmed that SIRT2 can interact with the receptor tyrosine kinase Axl within the TAM receptor family and act as a deacetylase to regulate the deacetylation of Axl. Concurrently, the inhibition of SIRT2 by AK-7 can lead to increased expression of Axl and activation of the anti-inflammatory pathway PI3K/Akt signaling pathway, which regulates microglial M2 polarization and consequently reduces WMI. However, when Axl expression was inhibited by the injection of the shAxl virus into the lateral ventricles, the downstream signaling pathways were significantly suppressed. Rescue experiments also confirmed that the neuroprotective effects of AK-7 can be reversed by PI3K inhibitors. These data suggest that SIRT2 influences WMI by affecting microglial polarization through the Axl/PI3K/AKT pathway, and that AK-7 could serve as an effective therapeutic drug for improving neurological functions in SAH patients.

We previously reported that combined therapy with epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) osimertinib and AXL inhibitor ONO-7475 is effective in preventing the survival of drug-tolerant cells in high-AXL-expressing EGFR-mutated non-small cell lung cancer (NSCLC) cells. Nevertheless, certain residual cells are anticipated to eventually develop acquired resistance to this combination therapy. In this study, we attempted to establish a multidrug combination therapy from the first-line setting to overcome resistance to this combination therapy in high-AXL-expressing EGFR-mutated NSCLC. siRNA screening assay showed that fibroblast growth factor receptor 1 (FGFR1) knockdown induced pronounced inhibition of cell viability in the presence of the osimertinib-ONO-7475 combination, which activates FGFR1 by upregulating FGF2 via the c-Myc pathway. Cell-based assays showed that triple therapy with osimertinib, ONO-7475, and the FGFR inhibitor BGJ398 significantly increased apoptosis by increasing expression of proapoptotic factor Bim and reduced cell viability compared with that observed for the osimertinib-ONO-7475 therapy. Xenograft models showed that triple therapy considerably suppressed tumor regrowth. A novel therapeutic strategy of additional initial FGFR1 inhibition may be highly effective in suppressing the emergence of osimertinib- and ONO-7475-resistant cells.

Lazertinib, a novel third-generation epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI), demonstrates marked efficacy in EGFR-mutant lung cancer. However, resistance commonly develops, prompting consideration of therapeutic strategies to overcome initial drug resistance mechanisms. This study aimed to elucidate the adaptive resistance to lazertinib and advocate novel combination treatments that demonstrate efficacy in preventing resistance as a first-line treatment for EGFR mutation-positive NSCLC. We found that AXL knockdown significantly inhibited lung cancer cell viability in the presence of lazertinib, indicating that AXL activation contributes to lazertinib resistance. However, long-term culture with a combination of lazertinib and AXL inhibitors led to residual cell proliferation and increased the MCL-1 expression level, which was mediated by the nuclear translocation of the transcription factor YAP. Triple therapy with an MCL-1 or YAP inhibitor in combination with lazertinib and an AXL inhibitor significantly reduced cell viability and increased the apoptosis rate. These results demonstrate that AXL and YAP/MCL-1 signals contribute to adaptive lazertinib resistance in EGFR-mutant lung cancer cells, suggesting that the initial dual inhibition of AXL and YAP/MCL-1 might be a highly effective strategy in eliminating lazertinib-resistant cells.

Virus receptors determine the tissue tropism of viruses and have a certain relationship with the clinical outcomes caused by viral infection, which is of great importance for the identification of virus receptors to understand the infection mechanism of viruses and to develop entry inhibitor. Proximity labeling (PL) is a new technique for studying protein-protein interactions, but it has not yet been applied to the identification of virus receptors or co-receptors. Here, we attempt to identify co-receptor of SARS-CoV-2 by employing TurboID-catalyzed PL. The membrane protein angiotensin-converting enzyme 2 (ACE2) was employed as a bait and conjugated to TurboID, and a A549 cell line with stable expression of ACE2-TurboID was constructed. SARS-CoV-2 pseudovirus were incubated with ACE2-TurboID stably expressed cell lines in the presence of biotin and ATP, which could initiate the catalytic activity of TurboID and tag adjacent endogenous proteins with biotin. Subsequently, the biotinylated proteins were harvested and identified by mass spectrometry. We identified a membrane protein, AXL, that has been functionally shown to mediate SARS-CoV-2 entry into host cells. Our data suggest that PL could be used to identify co-receptors for virus entry.

Triple-negative breast cancer (TNBC) is the most aggressive subtype with high metastasis and mortality rates. Given the lack of actionable targets such as ER and HER2, TNBC still remains an unmet therapeutic challenge. Despite harboring high CDK4/6 expression levels, the efficacy of CDK4/6 inhibition in TNBC has been limited due to the emergence of resistance. The resistance to CDK4/6 inhibition is mainly mediated by RB1 inactivation. Since our aim is to overcome resistance to CDK4/6 inhibition, in this study, we primarily used the cell lines that do not express RB1. Following a screening for activated receptor tyrosine kinases (RTKs) upon CDK4/6 inhibition, we identified the TAM (Tyro3, Axl, and MerTK) RTKs as a crucial therapeutic vulnerability in TNBC. We show that targeting the TAM receptors with a novel inhibitor, sitravatinib, significantly sensitizes TNBC to CDK4/6 inhibitors. Upon prolonged HER2 inhibitor treatment, HER2+ breast cancers suppress HER2 expression, physiologically transforming into TNBC-like cells. We further show that the combined treatment is highly effective against drug-resistant HER2+ breast cancer as well. Following quantitative proteomics and RNA-seq data analysis, we extended our study into the immunophenotyping of TNBC. Given the roles of the TAM receptors in promoting the creation of an immunosuppressive tumor microenvironment (TME), we further demonstrate that the combination of CDK4/6 inhibitor abemaciclib and sitravatinib modifies the immune landscape of TNBC to favor immune checkpoint blockade. Overall, our study offers a novel and highly effective combination therapy against TNBC and potentially treatment-resistant HER2+ breast cancer that can be rapidly moved to the clinic.

EGFR tyrosine kinase inhibitor (TKI) resistance is a major challenge for EGFR-mutant non-small cell lung cancer (NSCLC) treatment. Our previous work revealed that overexpression of AXL promoted EGFR-TKI resistance through epithelial-mesenchymal transition (EMT) in a subset of NSCLC patients. Compared with erlotinib resistant and sensitive cells, RP11-874 J12.4 was upregulated in erlotinib-resistant NSCLC cells (HCC827-ER3). Interestingly, the expression of RP11-874 J12.4 positively correlated with AXL. Besides, RP11-874 J12.4 promotes NSCLC cell proliferation and metastasis in vitro. Mechanistically, RP11-874 J12.4 promoted AXL expression through sponge with miR-34a-5p, which was reported to inhibit the translation of AXL mRNA. Meanwhile, the expression of RP11-874 J12.4 in lung cancer tumors were higher than the adjacent tissue, and those patients with high expression of RP11-874 J12.4 showed a poor prognosis in clinical. High expression of RP11-874 J12.4 might be a biomarker for NSCLC patients with erlotinib resistance. These findings reveal a novel insight into the mechanism of erlotinib resistance in NSCLC, and it might be a promising target for the diagnosis and treatment of NSCLC.

Cardiac fibrosis caused by ventricular remodeling and dysfunction such as post-myocardial infarction (MI) can lead to heart failure. RNA N6-methyladenosine (m6A) methylation has been shown to play a pivotal role in the occurrence and development of many illnesses. In investigating the biological function of the m6A reader YTHDF1 in cardiac fibrosis, adeno-associated virus 9 was used to knock down or overexpress the YTHDF1 gene in mouse hearts, and MI surgery in vivo and transforming growth factor-β (TGF-β)-activated cardiac fibroblasts in vitro were performed to establish fibrosis models. Our results demonstrated that silencing YTHDF1 in mouse hearts can significantly restore impaired cardiac function and attenuate myocardial fibrosis, whereas YTHDF1 overexpression could further enhance cardiac dysfunction and aggravate the occurrence of ventricular pathological remodeling and fibrotic development. Mechanistically, zinc finger BED-type containing 6 mediated the transcriptional function of the YTHDF1 gene promoter. YTHDF1 augmented AXL translation and activated the TGF-β-Smad2/3 signaling pathway, thereby aggravating the occurrence and development of cardiac dysfunction and myocardial fibrosis. Consistently, our data indicated that YTHDF1 was involved in activation, proliferation, and migration to participate in cardiac fibrosis in vitro. Our results revealed that YTHDF1 could serve as a potential therapeutic target for myocardial fibrosis.

UNASSIGNED: The severity, symptoms, and outcome of COVID-19 is thought to be closely linked to how the virus enters host cells. This process involves the key roles of angiotensin-converting enzyme 2 (ACE2) and the Tyrosine protein kinase receptor UFO (AXL) receptors. However, there is limited research on the circulating levels of ACE2 and AXL and their implications in COVID-19.
UNASSIGNED: A control group of 71 uninfected individuals was also included in the study. According to the Guidance for Corona Virus Disease 2019 (10th edition), a cohort of 358 COVID-19 patients were categorized into non-severe and severe cases. Serum ACE2/AXL levels in COVID-19 patients were detected by enzyme-linked immunosorbent assay (ELISA) at different time points post-COVID-19 infection, including days 0-7, 8-15, 31-179 and >180 days. Serum SARS-CoV-2 IgG/IgM antibodies in COVID-19 patients at the same intervals were assessed by using an iFlash 3000 Chemiluminescence Immunoassay Analyzer. The receiver operating characteristic (ROC) curves were used to assess the diagnostic value of the biological markers, and the association between laboratory parameters and illness progression were explored.
UNASSIGNED: Compared with the uninfected group, the levels of ACE2 and AXL in the COVID-19 group were decreased, and the SARS-COV-2 IgG level was increased. AXL (AUC = 0.774) demonstrated a stronger predictive ability for COVID-19 than ACE2. In the first week after infection, only the level of AXL was statistically different between severe group and non-severe group. After first week, the levels of ACE2 and AXL were different in two groups. Moreover, in severe COVID-19 cases, the serum ACE2, AXL, and SARS-COV-2 IgM levels reached a peak during days 8-15 before declining, whereas serum SARS-COV-2 IgG levels continued to rise, reaching a peak at day 31-180 days before decreasing. In addition, the AXL level continued to decrease and the SARS-COV-2 IgG level continued to increase in the infected group after 180 days compared to the uninfected group.
UNASSIGNED: The levels of serum ACE2 and AXL correlate with COVID-19 severity. However, AXL can also provide early warning of clinical deterioration in the first week after infection. AXL appears to be a superior potential molecular marker for predicting COVID-19 progression.

Rationale: AXL expression has been identified as a prognostic factor in acute myeloid leukemia (AML) and is detectable in approximately 50% of AML patients. In this study, we developed AXL-specific single domain antibodies (sdAbs), cross-reactive for both mouse and human AXL protein, to non-invasively image and treat AXL-expressing cancer cells. Methods: AXL-specific sdAbs were induced by immunizing an alpaca with mouse and human AXL proteins. SdAbs were characterized using ELISA, flow cytometry, surface plasmon resonance and the AlphaFold2 software. A lead compound was selected and labeled with 99mTc for evaluation as a diagnostic tool in mouse models of human (THP-1 cells) or mouse (C1498 cells) AML using SPECT/CT imaging. For therapeutic purposes, the lead compound was fused to a mouse IgG2a-Fc tail and in vitro functionality tests were performed including viability, apoptosis and proliferation assays in human AML cell lines and primary patient samples. Using these in vitro models, its anti-tumor effect was evaluated as a single agent, and in combination with standard of care agents venetoclax or cytarabine. Results: Based on its cell binding potential, cross-reactivity, nanomolar affinity and GAS6/AXL blocking capacity, we selected sdAb20 for further evaluation. Using SPECT/CT imaging, we observed tumor uptake of 99mTc-sdAb20 in mice with AXL-positive THP-1 or C1498 tumors. In THP-1 xenografts, an optimized protocol using pre-injection of cold sdAb20-Fc was required to maximize the tumor-to-background signal. Besides its diagnostic value, we observed a significant reduction in tumor cell proliferation and viability using sdAb20-Fc in vitro. Moreover, combining sdAb20-Fc and cytarabine synergistically induced apoptosis in human AML cell lines, while these effects were less clear when combined with venetoclax. Conclusions: Because of their diagnostic potential, sdAbs could be used to screen patients eligible for AXL-targeted therapy and to follow-up AXL expression during treatment and disease progression. When fused to an Fc-domain, sdAbs acquire additional therapeutic properties that can lead to a multidrug approach for the treatment of AXL-positive cancer patients.