EGFR-mutant Non-small Cell Lung Cancer Cell Lines Research Articles

Abstract 5843: Exploring the implications of LPAR-1 expression in TKI-resistant NSCLC

Abstract Introduction: Non-small cell lung cancer (NSCLC) is the most common type of lung cancer in the United States with a 5-year survival rate hovering between 20-30%. Mutations in EGFR can initially cause the tumors to respond to tyrosine kinase inhibitors (TKI). Osimertinib, a third generation TKI, is the preferred first or second line of treatment and despite being effective, recent reports indicate that patients develop resistance within 10-18 months of treatment. TKI resistance limits therapeutic options for patients and therefore, alternative strategies are being explored. In this context, Lysophosphatidic acid receptors (LPARs), a family of G-protein coupled receptors consisting of LPARs 1-6 expressed differentially in prostate, breast, ovarian, pancreatic, and brain cancers are being explored as potential targets for drug resistant cancers. Specifically, LPAR-1 has been shown to play a role in tumor cell clonogenicity, migration, and response to therapy in EGFR mutant NSCLC cells. Pharmacological inhibition or CRIPSR based deletion of LPAR-1 in EGFR mutant NSCLC cell lines HCC827 and NCI-H3255, increased TKI sensitivity by reducing clonogenic potential. Further, detailed pathway analysis in TKI sensitive and resistant EGFR mutant cell lines suggests that LPAR-1 expression influences drug sensitivity. Surprisingly, the role of LPAR-1 in TKI sensitivity is not well understood. In the present study, we have performed detailed investigation on the implications of LPAR-1 expression in the development of Osimertinib resistance. Methods: Osimertinib resistant EGFR mutant cell lines (OR) were generated using dose-escalation method and drug-tolerant persisters (DTPs) were generated using a short-term high exposure method. Gene and protein expressions were examined using qPCR and western blotting. Subcutaneous tumor cell derived xenografts were generated for in vivo studies. Results: LPAR-1 is downregulated in Osimertinib resistant NSCLC cells. Further, we also observe that LPAR-1 levels are lower in DTP cells, confirming a progressive loss of LPAR-1 with Osimertinib treatment. In vivo studies in cell derived xenografts correlated with the in vitro studies. Conclusion: Our studies indicate LPAR-1 downregulation correlates to Osimertinib resistance in EGFR mutant NSCLC cell lines. LPAR-1 downregulation has a key role in development of Osimertinib resistance. Future studies will focus on delineating LPAR-1 signaling pathways related to TKI resistance and investigating the effect of LPAR-1 overexpression using CRISPR technology. Citation Format: Varsha Srinivasan, Zhaohui Li, Raghuraman Kannan, Anandhi Upendran. Exploring the implications of LPAR-1 expression in TKI-resistant NSCLC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5843.

Abstract 4746: PIM kinase inhibition synergizes with a MERTK inhibitor to treat osimertinib resistant EGFR-mutant non-small cell lung cancer

Abstract There is an unmet need for effective treatment in the setting of acquired osimertinib resistance in EGFR-mutant non-small cell lung cancer (NSCLC) patients and MERTK tyrosine kinase is a potential therapeutic target in this context. Treatment with the MERTK inhibitor MRX-2843 was sufficient to abrogate downstream PI3K-AKT and MAPK-ERK signaling, cell expansion, and colony formation in osimertinib-resistant EGFR-mutant NSCLC cell lines, suggesting dependence on MERTK signaling for tumor cell proliferation/survival. Further, two structurally distinct PIM kinase inhibitors, SGI-1776 and PIM447, provided synergistic inhibition of cell expansion and colony formation in osimertinib-resistant cell line cultures when combined with MRX-2843 treatment. Mechanistically, treatment with MRX-2843 in combination with either PIM kinase inhibitor decreased downstream PI3K-AKT and MAPK-ERK signaling more effectively than single agents. Furthermore, knockdown of PIM kinases (PIM1, 2, 3) using nine sets of siRNAs led to various changes in expression of TAM receptor family members (TYRO3, AXL, MERTK), indicating a role for PIM kinases in regulation of TAM kinase expression. These studies suggest a novel treatment strategy for osimertinib-resistant EGFR-mutant NSCLC using a first-in-class MERTK kinase inhibitor that is currently under evaluation in multiple Phase I clinical trials. Citation Format: Dan Yan, Xiaodong Wang, Stephen V. Frye, H. Shelton Earp, Deborah DeRyckere, Douglas K. Graham. PIM kinase inhibition synergizes with a MERTK inhibitor to treat osimertinib resistant EGFR-mutant non-small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4746.

Upregulation of long non‑coding RNA LINC00460 in EGFR‑mutant lung cancer indicates a poor prognosis in patients treated with osimertinib.

The long non-coding RNA (lncRNA) LINC00460 is involved in tumor growth, metastasis and drug resistance. The present study investigated the clinical significance of LINC00460 expression in patients with epidermal growth factor receptor (EGFR) mutation-positive lung cancer treated with osimertinib. Osimertinib-resistant cells we derived from EGFR-mutant non-small-cell lung cancer (NSCLC) cell lines, after which, small interfering RNA (siRNA)-mediated silencing and in vitro-transcribed (IVT), synthetic LINC00460 RNA transfection were used to investigate the effects of LINC00460 expression on acquired resistance to osimertinib. Reverse transcription-quantitative polymerase chain reaction was performed to evaluate LINC00460 expression in 54 samples (RNA extracted from the tumor tissues of 30 cases and cell-free RNA from 24 cases) obtained from patients with EGFR mutation-positive lung cancer who had received osimertinib as the initial treatment. The acquisition of osimertinib resistance increased the expression of LINC00460 in the EGFR-mutant NSCLC cell lines. By contrast, knockdown of LINC00460 in osimertinib-resistant cell lines increased their sensitivity to osimertinib, whereas treatment of NSCLC cells with IVT LINC00460 RNA decreased their sensitivity to osimertinib. The present study examined LINC00460 expression at the primary tumor site and demonstrated that compared with in the low-expression group (n=24), the high-expression group (n=6) had a significantly lower best overall response rate to osimertinib (16.6% vs. 60.0%; P=0.044), significantly shorter median progression-free survival (PFS; 224 days vs. 669 days; P=0.001) and significantly shorter median overall survival (724 days vs. not reached; P=0.011). Moreover, following osimertinib therapy, PFS was significantly shorter for patients with high LINC00460 expression in plasma cell-free RNA (n=12) than for those with low LINC00460 expression (n=12) (median PFS: 655 days vs. 210 days; P=0.020). In conclusion, the upregulation of LINC00460, the expression of which is implicated in osimertinib resistance, in the primary site and plasma of patients with EGFR mutation-positive lung cancer may be associated with a poor prognosis in those treated with osimertinib.

AX-0085, a novel AXL kinase inhibitor, and effects on osimertinib-resistance in non–small-cell lung cancer.

e15121 Background: Osimertinib is a third-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) having high efficacy in treating patients with advanced non-small cell lung cancer (NSCLC) with EGFR activating mutations and EGFR T70M mutations. Although, osimertinib is a frontline anticancer agent for treating NSCLC, many patients inevitably develop osimertinib-resistance tumor recurrence. The activation of AXL was reported to be a major factor driving osimertinib-resistance in NSCLC. Thus, AXL is a promising therapeutic target for the treatment of osimertinib-resistant NSCLC, and we developed a new small-molecule AXL inhibitor, AX-0085. Methods: We established osimertinib-resistant cell lines from EGFR-mutated NSCLC cell lines, HCC827 and H1975, after high dose exposure and stepwise exposure to osimertinib in culture. We investigated the cell viability of AX-0085 and other kinase inhibitors, and the anti-tumor activity of AX-0085 on the proliferation, migration, apoptosis, and epithelial-mesenchymal transition (EMT) in osimertinib-resistant cells. Results: Compared to the parental cells, IC50 of resistant cell to osimertinib was significantly increased and osimertinib-resistant cells showed remarkably increased expression of AXL/pAXL and p-SRC as compared to the parental HCC827 cell. AX-0085 was completely blocked the AXL and SRC activation but EGFR inhibitors (gefitinib and osimertinib) did not inhibit the activation of AXL and SRC in the osimertinib-resistant cell line. AX-0085 (IC50: 4.4nM for AXL kinase in cell-based kinase assay) was one of the most potent AXL inhibitors and showed the strongest cytotoxicity against osimertinib-resistant cells compared to other kinase inhibitors. AX-0085 effectively down-regulated mRNA level of AXL and AXL regulating transcription factors in NSCLC cell lines such as HCC827 and H1975. AX-0085 treatment effectively inhibited the activation of AXL in acquired osimertinib-resistant cells and decreased the mRNA level of AXL and AXL regulating transcription factors. AX-0085 significantly inhibited the cell proliferation, apoptosis, migration, and EMT in acquired osimertinib-resistant cells. Conclusions: Our results showed that AX-0085 selectively inhibits the activation of AXL to overcome acquired resistance to osimertinib, suggesting an effective AXL-based therapy for patients with osimertinib-resistant tumors. Currently, AX-0085 is undergoing non-clinical trials.

DMU-212 against EGFR-mutant non-small cell lung cancer via AMPK/PI3K/Erk signaling pathway

Although some important advances have been achieved in clinical and diagnosis in the past few years, the management of non-small cell lung cancer (NSCLC) is ultimately dissatisfactory due to the low overall cure and survival rates. Epidermal growth factor (EGFR) has been recognized as a carcinogenic driver and is a crucial pharmacological target for NSCLC. DMU-212, an analog of resveratrol, has been reported to have significant inhibitory effects on several types of cancer. However, the effect of DMU-212 on lung cancer remains unclear. Therefore, this study aims to determine the effects and underlying mechanism of DMU-212 on EGFR-mutant NSCLC cells. The data found that the cytotoxicity of DMU-212 on three EGFR-mutant NSCLC cell lines was significantly higher than that of normal lung epithelial cell. Further study showed that DMU-212 can regulate the expression of cell cycle-related proteins including p21 and cyclin B1 to induce G2/M phase arrest in both H1975 and PC9 cells. Moreover, treatment with DMU-212 significantly promoted the activation of AMPK and simultaneously down-regulated the expression of EGFR and the phosphorylation of PI3K, Akt and ERK. In conclusion, our study suggested that DMU-212 inhibited the growth of NSCLCs via targeting of AMPK and EGFR.

Analyses of single extracellular vesicles from non-small lung cancer cells to reveal effects of epidermal growth factor receptor inhibitor treatments

Precision cancer medicine has changed the treatment landscape of non-small cell lung cancer (NSCLC) as illustrated by the introduction of tyrosine kinase inhibitors (TKIs) towards mutated epidermal growth factor receptor (EGFR). However, as responses to EGFR-TKIs are heterogenous among NSCLC patients, there is a need for ways to early monitor changes in treatment response in a non-invasive way e.g., in patient's blood samples. Recently, extracellular vesicles (EVs) have been identified as a source of tumor biomarkers which could improve on non-invasive liquid biopsy-based diagnosis of cancer. However, the heterogeneity in EVs is high. Putative biomarker candidates may be hidden in the differential expression of membrane proteins in a subset of EVs hard to identify using bulk techniques. Using a fluorescence-based approach, we demonstrate that a single-EV technique can detect alterations in EV surface protein profiles. We analyzed EVs isolated from an EGFR-mutant NSCLC cell line, which is refractory to EGFR-TKIs erlotinib and responsive to osimertinib, before and after treatment with these drugs and after cisplatin chemotherapy. We studied expression level of five proteins; two tetraspanins (CD9, CD81), and three markers of interest in lung cancer (EGFR, programmed death-ligand 1 (PD-L1), human epidermal growth factor receptor 2 (HER2)). The data reveal alterations induced by the osimertinib treatment compared to the other two treatments. These include the growth of the PD-L1/HER2-positive EV population, with the largest increase in vesicles exclusively expressing one of the two proteins. The expression level per EV decreased for these markers. On the other hand, both the TKIs had a similar effect on the EGFR-positive EV population.

Abstract 3267: EGFR inhibition in EGFR-mutant lung cancer triggers the innate immune response associated with tumor immune escape

Abstract EGFR-tyrosine kinase inhibitors (TKIs) benefit patients with EGFR-mutant non-small cell lung cancer (NSCLC). Still, the majority of patients eventually develop resistance to the therapy. This study thus explored therapeutic targets to overcome this resistance immunologically. Our screening in the public database and in vitro confirmatory experiments revealed that the expression of the innate immune checkpoint CD24 was induced in EGFR-mutant NSCLC cell lines such as PC9 and H1975 when treated with EGFR-TKIs. Immunohistochemistry revealed tissue samples from patients who developed resistance to EGFR inhibition without the acquired T790M mutation demonstrated increased tumor CD24 expression compared to pre-treatment samples. Tumor CD24 binds to Siglec-10 on macrophages and inhibits tumor cell phagocytosis in breast and ovarian cancer. However, in NSCLC, we found that the transcriptional expression levels of SIGLEC-10 across human tumor-associated macrophages were quite heterogeneous, as evidenced by scRNA-seq. In addition, human monocyte-derived macrophages (MDMs) required M-CSF, IL-10, and TGF-β to express Siglec-10. Its expression was absent in MDMs differentiated either by GM-CSF±IFN-γ/LPS or M-CSF±IL-4. These data suggest that the CD24/Siglec-10 inhibitory pathway may be present but partial in NSCLC. Therefore, we asked whether CD24-targeted therapy could be beneficial regardless of the presence of the CD24/Siglec-10 inhibitory pathway. Using our MDM differentiation protocols mentioned above, MDMs devoid of Siglec-10 facilitated antibody-dependent cellular phagocytosis of EGFR-TKI-treated PC9 tumor cells when co-cultured with anti-CD24 monoclonal antibodies. Subsequently, we focused on cell-free DNA (cfDNA) released from dying tumor cells. The amounts of cfDNA from dying tumor cells were at least twice and more by EGFR-TKIs than conventional cytotoxic drugs such as paclitaxel. cfDNA from EGFR-mutant cells following EGFR inhibition activated the IRF pathway in THP-1 monocytes in a STING-dependent manner. Moreover, PMA-differentiated THP-1 monocytes no longer produced CXCL9 upon interferon-γ stimulation when pre-treated with cfDNA. The same results were obtained when they were pre-treated with interferon-α. In conclusion, we demonstrated two potential mechanisms which could facilitate tumor immune escape. Targeting these pathways may overcome the resistance to EGFR inhibition in patients with EGFR-mutant NSCLC. Citation Format: Akihiko Shiiya, Takuro Noguchi, Utano Tomaru, Shin Ariga, Yuta Takashima, Yoshihito Ohhara, Jun Taguchi, Satoshi Takeuchi, Yasushi Shimizu, Ichiro Kinoshita, Tomonobu Koizumi, Yoshihiro Matsuno, Naofumi Shinagawa, Jun Sakakibara-Konishi, Hirotoshi Dosaka-Akita. EGFR inhibition in EGFR-mutant lung cancer triggers the innate immune response associated with tumor immune escape [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3267.

Abstract 3907: Targeting adaptive resistance to EGFR and KRAS G12C inhibitors by TT125-802, a novel and specific CBP/p300 bromodomain inhibitor

Abstract Resistance to targeted therapies is a major challenge in oncology. Disease progression is caused by multiple resistance mechanisms. Besides pre-existing and acquired genetic alternations, adaptive non-mutational reprogramming as well as modulation of phenotypic plasticity have emerged as drivers of disease progression. For example, in epidermal growth factor receptor (EGFR)-mutated non-small cell lung cancer (NSCLC) patients who were treated with osimertinib, ~50% of progressive disease could not be attributed to genetic mutations (Leonetti et al., BJC 2019). Similarly, in ~ 40% of patients suffering from KRAS G12C-mutated NSCLC and colorectal cancer (CRC), disease progressed under sotorasib treatment without identifiable acquired mutations (Zhao et al., Nature 2021). Thus, targeting non-genetic adaptive resistance mechanism such as drug-induced transcriptional reprogramming might be of great therapeutic benefit. Here we identified small molecules, that interfere with cancer drug-induced transcriptional escape mechanisms using a phenotypic screen based on an SRY-Box Transcription Factor 2 (SOX2) reporter system. The screen led to the development of TT125-802, a highly specific and potent, orally available small molecule inhibitor of the bromodomain of the transcriptional and epigenetic regulator CBP [cyclic adenosine monophosphate response element binding protein (CREB) binding protein] and its paralogue p300. TT125-802 dose-dependently prevented osimertinib resistance development in EGFR-mutated NSCLC cell lines HCC827 and HCC4006, as well as sotorasib resistance development in KRAS G12C-mutated NCI-H358 (NSCLC), SW837 and SNU-1411 (CRCs) as assessed by label-free long-term live microscopy assays. Data generated in mouse xenograft studies confirmed the ability of TT125-802 increasing response rates and prolonging the duration of response to osimertinib and sotorasib in vivo. In cells and tumours which were already resistant to osimertinib or sotorasib, TT125-802 could still delay cell or tumor growth. Complementary and longitudinal analysis of transcriptional changes using RNA sequencing in vitro and in vivo identified several early adaptive and late acquired resistance signatures that were reversed by TT125-802. A first-in-human study of TT125-802 in cancer patients is on track to start in 2023. Citation Format: Thomas Bohnacker, Dorothea Gruber, Sara Laudato, Martin Schwill, Charles-Henry Fabritius, Raquel Herrador, Katrin Westritschnig, Thushara Pattupara, Vikram Ayinampudi, Stefanie Flückiger-Mangual. Targeting adaptive resistance to EGFR and KRAS G12C inhibitors by TT125-802, a novel and specific CBP/p300 bromodomain inhibitor. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3907.

EGFR inhibition in EGFR-mutant lung cancer cells perturbs innate immune signaling pathways in the tumor microenvironment.

Epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKIs) elicit potent cell cycle arrest in EGFR-mutant non-small-cell lung cancer (NSCLC) cells. However, little is known about the mechanisms through which these drugs alter the tumor phenotype that contributes to the immune escape of EGFR-mutant cells. Using EGFR-mutant NSCLC cell lines and tissue samples from patients, we investigated the changes in immune checkpoints expressed in tumor cells following EGFR inhibition. Subsequently, we also analyzed the role of soluble factors from the dying tumor cells in the activation of immune signaling pathways involved in therapy resistance. Upon EGFR-TKI treatment, we found that EGFR-mutant cells upregulated the expression of innate immune checkpoint CD24 in vitro. We then analyzed biopsy samples from six patients who developed resistance to a first-generation EGFR-TKI without the acquired T790M mutation. Immunohistochemistry revealed that levels of tumor CD24 expression were increased upon treatment compared with those from pre-treatment samples. Monocyte-derived macrophages facilitated antibody-dependent cellular phagocytosis when EGFR-TKI-treated EGFR-mutant cells were incubated with anti-CD24 antibodies in vitro, suggesting that CD24 may be a therapeutical target for EGFR-mutant lung cancer. Moreover, EGFR inhibition accelerated the release of cell-free DNA (cfDNA) from dying tumor cells, which activated the type I interferon signaling pathways in human THP-1 monocytes in a stimulator of interferon genes-dependent manner. Our study indicates that EGFR inhibition in EGFR-mutant NSCLC cells fosters a tumor microenvironment associated with immune escape. Thus, CD24 targeted therapy and cfDNA monitoring may contribute to improved treatment outcomes in patients with EGFR-mutant NSCLC.

PD‐L1 blockade by immune checkpoint inhibitors impairs sensitivity to osimertinib in EGFR‐mutant non‐small cell lung cancer cells

In the previous studies, it was shown that osimertinib plus durvalumab did not achieve satisfactory efficacy, even inferior to osimertinib alone. We found that PD-L1 blockade impaired the efficacy of osimertinib in EGFR-mutant NSCLC cells despite the presence of the tumor microenvironment. Therefore, durvalumab has no synergistic effect on osimertinib, and combination therapy will not enhance the efficacy of osimertinib. In recent years, the management of advanced non-small cell lung cancer (NSCLC) with epidermal growth factor receptor (EGFR) mutation has developed rapidly. Osimertinib is a third generation EGFR tyrosine kinase inhibitor (TKI), which has achieved satisfactory efficacy and tolerability as the first-line (FLARUA study [ref]) and second-line (AURA series of studies [ref]) treatment of patients with EGFR-mutant NSCLC. This suggested that EGFR signaling is involved in the upregulation of programmed cell death ligand 1 (PD-L1) expression, which induces apoptosis of T cells, thereby promoting immune escape of tumor cells [1]. Therefore, several studies were conducted to explore the efficacy and safety of osimertinib combined with PD-L1 monoclonal antibody durvalumab in patients with EGFR-mutant NSCLC. The TATTON study is a phase Ib trial of osimertinib combination therapy, including durvalumab, in treatment of advanced EGFR-mutant NSCLC. Results showed that the combination of osimertinib and durvalumab resulted in an objective response rate (ORR) of 43%, but an increased incidence of interstitial lung disease (ILD) (22%). Another phase III study of osimertinib versus osimertinib plus durvalumab, the CAURAL trial, whose recruitment was terminated early due to the high incidence of ILD in the TATTON trial, showed an ORR of 80% in the osimertinib arm compared with an ORR of 64% in the combination arm [2]. Therefore, the combination of osimertinib plus durvalumab did not appear to provide a significant improvement in efficacy compared with osimertinib alone [3]. Regardless of the impact of durvalumab on the tumor microenvironment and the high incidences of adverse events, whether PD-L1 blockade itself has a synergistic effect on osimertinib treatment is still unknown. The role of PD-L1 blockade in the treatment of EGFR-mutant NSCLC with osimertinib, regardless of the effect on the tumor immune microenvironment, has not been reported. Here, we used a human EGFR-mutant NSCLC cell line HCC4006 (ATCC® CRL-2871™) to test the IC50 of osimertinib alone or in combination with different concentrations of durvalumab to explore the effect of osimertinib in blocking PD-L1. After seeding cells in 96-well plates, the cells were treated with a concentration gradient of osimertinib (manufacturer, city and country) ranging from 1 to 40 µm, diluted in serum-free medium alone or with 0.5 mg/mL durvalumab (manufacturer, city and country), 1 mg/mL durvalumab or 2 mg/mL durvalumab, respectively. After an additional 24 h of incubation, an MTS assay was performed to examine the IC50 of osimertinib against EGFR-mutant NSCLC cells using different solvents. It was proved that the IC50 of osimertinib continued to increase with the increase of durvalumab concentration compared with osimertinib alone, which was 6.202 µm, 9.28 µm, 13.37 µm, and 15.18 µm for osimertinib plus 0.5 mg/mL durvalumab, osimertinib plus 1 mg/mL durvalumab and osimertinib plus 2 mg/mL durvalumab, respectively (Figure 1). Currently, there is still a lack of evidence for first-line osimertinib combined with durvalumab or other immune checkpoint inhibitors (ICIs) in patients with EGFR-mutant NSCLC. In the above-mentioned previous studies, it was shown that combination therapy did not achieve satisfactory efficacy, even inferior to osimertinib alone. Durvalumab blocks PD-L1 on the surface of tumor cells and relieves the suppressive effect of immune cells in the tumor stroma. However, based on in vitro experiments, we found that PD-L1 blockade impaired the efficacy of osimertinib in EGFR-mutant NSCLC cells despite the presence of the tumor microenvironment. Therefore, durvalumab has no synergistic effect on osimertinib, and combination therapy will not enhance the efficacy of osimertinib. In summary, we should be cautious when choosing first-line EGFR-TKIs combined with immunotherapy. Conception/design: Dantong Sun and Junling Li. Collection and/or assembly of data: Dantong Sun and Puyuan Xing. Manuscript writing: Dantong Sun and Junling Li. Final approval of manuscript: All authors. None. The authors declare no conflict of interest. All experiments were carried out following the National Health and Family Planning Commission of the Professional Regulation Commission (PRC) guidelines. Not applicable. Data supporting this report are available from the corresponding authors on reasonable request.

Therapeutic potential of the novel Bcl-2/Bcl-XL dual inhibitor, APG1252, alone or in combination against non-small cell lung cancer.

Targeting the induction of apoptosis is a promising cancer therapeutic strategy with some clinical success. This study focused on evaluating the therapeutic efficacy of the novel Bcl-2/Bcl-XL dual inhibitor, APG1252-M1 (also named APG-1244; an in vivo active metabolite of APG1252 or pelcitoclax), as a single agent or in combination, against non-small cell lung cancer (NSCLC) cells. APG1252-M1 effectively decreased the survival of some NSCLC cell lines expressing low levels of Mcl-1 and induced apoptosis. Overexpression of ectopic Mcl-1 in the sensitive cells substantially compromised APG1252-M1's cell-killing effects, whereas inhibition of Mcl-1 greatly sensitized insensitive cell lines to APG1252-M1, indicating the critical role of Mcl-1 levels in impacting cell response to APG1252-M1. Moreover, APG1252-M1, when combined with the third generation epidermal growth factor receptor (EGFR) inhibitor, osimertinib, synergistically decreased the survival of EGFR-mutant NSCLC cell lines including those resistant to osimertinib with enhanced induction of apoptosis and abrogated emergence of acquired resistance to osimertinib. Importantly, the combination was effective in inhibiting the growth of osimertinib-resistant tumors in vivo. Collectively, these results demonstrate the efficacy of APG1252 alone or in combination against human NSCLC cells.

Drug repositioning of tranilast to sensitize a cancer therapy by targeting cancer-associated fibroblast.

Cancer‐associated fibroblasts (CAFs) are a major component of the tumor microenvironment that mediate resistance of cancer cells to anticancer drugs. Tranilast is an antiallergic drug that suppresses the release of cytokines from various inflammatory cells. In this study, we investigated the inhibitory effect of tranilast on the interactions between non–small cell lung cancer (NSCLC) cells and the CAFs in the tumor microenvironment. Three EGFR‐mutant NSCLC cell lines, two KRAS‐mutant cell lines, and three CAFs derived from NSCLC patients were used. To mimic the tumor microenvironment, the NSCLC cells were cocultured with the CAFs in vitro, and the molecular profiles and sensitivity to molecular targeted therapy were assessed. Crosstalk between NSCLC cells and CAFs induced multiple biological effects on the NSCLC cells both in vivo and in vitro, including activation of the STAT3 signaling pathway, promotion of xenograft tumor growth, induction of epithelial‐mesenchymal transition (EMT), and acquisition of resistance to molecular‐targeted therapy, including EGFR‐mutant NSCLC cells to osimertinib and of KRAS‐mutant NSCLC cells to selumetinib. Treatment with tranilast led to inhibition of IL‐6 secretion from the CAFs, which, in turn, resulted in inhibition of CAF‐induced phospho‐STAT3 upregulation. Tranilast also inhibited CAF‐induced EMT in the NSCLC cells. Finally, combined administration of tranilast with molecular‐targeted therapy reversed the CAF‐mediated resistance of the NSCLC cells to the molecular‐targeted drugs, both in vitro and in vivo. Our results showed that combined administration of tranilast with molecular‐targeted therapy is a possible new treatment strategy to overcome drug resistance caused by cancer‐CAF interaction.

The EGFR-STYK1-FGF1 axis sustains functional drug tolerance to EGFR inhibitors in EGFR-mutant non-small cell lung cancer

Non-small cell lung cancer (NSCLC) patients harboring activating mutations in epidermal growth factor receptor (EGFR) are sensitive to therapy with EGFR tyrosine kinase inhibitors (TKI). Despite remarkable clinical responses using EGFR TKI, surviving drug tolerant cells serve as a reservoir from which drug resistant tumors may emerge. This study addresses the need for improved efficacy of EGFR TKI by identifying targets involved in functional drug tolerance against them. To this aim, a high-throughput siRNA kinome screen was performed using two EGFR TKI-sensitive EGFR-mutant NSCLC cell lines in the presence/absence of the second-generation EGFR TKI afatinib. From the screen, Serine/Threonine/Tyrosine Kinase 1 (STYK1) was identified as a target that when downregulated potentiates the effects of EGFR inhibition in vitro. We found that chemical inhibition of EGFR combined with the siRNA-mediated knockdown of STYK1 led to a significant decrease in cancer cell viability and anchorage-independent cell growth. Further, we show that STYK1 selectively interacts with mutant EGFR and that the interaction is disrupted upon EGFR inhibition. Finally, we identified fibroblast growth factor 1 (FGF1) as a downstream effector of STYK1 in NSCLC cells. Accordingly, downregulation of STYK1 counteracted the afatinib-induced upregulation of FGF1. Altogether, we unveil STYK1 as a valuable target to repress the pool of surviving drug tolerant cells arising upon EGFR inhibition. Co-targeting of EGFR and STYK1 could lead to a better overall outcome for NSCLC patients.

Abstract 417: Identification of next-generation EGFR degraders to treat non-small cell lung cancer (NSCLC) patients

Abstract Although EGFR-targeted tyrosine kinase inhibitors (TKIs) developed over a couple of decades have made great progress in the treatment of EGFR-mutant driven NSCLC, patients are at great risk to their lives due to drug resistance caused by constantly emerging EGFR mutations. Targeted protein degraders (TPDs), also known as heterobifunctional protein degraders or PROteolysis TArgeting Chimeras (PROTACs), have drawn great attention as a new modality to overcome drug resistance by achieving selective degradation of disease-causing proteins, like an EGFR mutant protein, which are required for the survival and proliferation of various malignant tumor cells. Therefore, we have developed a series of EGFR mutant degraders using BBT-176, a 4th generation EGFR TKI developed by Bridge BioTherapeutics, and novel EGFR inhibitors as warheads which are expected not only to treat various EGFR mutated NSCLC including C797S but also to delay drug resistant-mechanisms by further mutations in the EGFR TKI target site. We synthesized a set of heterobifunctional degraders applying Cyrus BiFx Degrader (CBD) library platform containing different types of linkers and E3 ligase binders. DC50 (half-maximal degradation concentrations) values of the EGFR degraders were obtained in multiple human EGFR mutant NSCLC cell lines, where C-2051, C-2482, and C-4383 showed excellent EGFR degradation potency (DC50 = 7-25 nM, Dmax at 100 nM = 80-97%) with high selectivity against WT EGFR. Among those compounds, C-4383 was potent in cell viability assays with EGFR mutant HCC827 (Del19) and NCI-H1975 (L858R, T790M) cell lines showing a range of GI50 values from 77 to 81 nM at 72 h of compound exposure. By contrast, the compound was much less potent in A549 cells harboring wild-type EGFR (GI50 value at 72 h of treatment, 4.2 μM). We also performed proteomic analysis of C-4383 in H1975 cells resulting that EGFR was the most degraded protein with no off-target events at 100 nM (Dmax dose). A PK study of C-4383 in rats showed good exposure with moderate CL when administered intravenously (CL = 8.51 mL/min/kg, AUC = 5911 ng•h/mL). In summary, we identified heterobifunctional degraders using a 4th generation EGFR inhibitor, BBT-176, that are active in EGFR mutant NSCLC cells harboring single or C797S-containing multiple mutations. We are currently making our efforts on the improvement of physicochemical properties of EGFR mutant targeted heterobifunctional compounds. Citation Format: Dong Hyuk Ki, Joonwoo Nam, Eunjung Kim, Hunmi Choi, Chulwon Kim, Jiyeon Kim, Jimmy Jin, Sang-Uk Kang, Wooseok Han. Identification of next-generation EGFR degraders to treat non-small cell lung cancer (NSCLC) patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 417.

LPIN1 Induces Gefitinib Resistance in EGFR Inhibitor-Resistant Non-Small Cell Lung Cancer Cells.

Simple SummaryHere, we attempted to identify targets that could be used to overcome resistance toward epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors in non-small cell lung cancer (NSCLC). To accomplish this, we chose LPIN1 among the candidate targets that were identified from a previously performed genome-wide RNAi screening assay and validated it as a key factor regulating gefitinib resistance in EGFR-mutant NSCLC cells. We confirmed that LPIN1 depletion increased gefitinib sensitivity in drug-resistant H1650 NSCLC cells, as well as patient-derived YL05 lung cancer cells. Moreover, we found that LPIN1 expression was induced following gefitinib treatment, and activities of protein kinase C delta and nuclear factor kappa B, and lipid droplet formation were induced in an LPIN1-dependent manner. Additionally, we validated that targeting LPIN1 synergistically retarded tumor growth in an in vivo mouse xenograft model.Drug resistance limits the efficacy of targeted therapies, including tyrosine kinase inhibitors (TKIs); however, a substantial portion of the drug resistance mechanisms remains unexplained. In this study, we identified LPIN1 as a key factor that regulates gefitinib resistance in epidermal growth factor receptor (EGFR)-mutant non-small cell lung cancer (NSCLC) cells. Unlike TKI-sensitive HCC827 cells, gefitinib treatment induced LPIN1 expression and increased diacylglycerol concentration in TKI-resistant H1650 cells, followed by the activation of protein kinase C delta and nuclear factor kappa B (NF-κB) in an LPIN1-dependent manner, resulting in cancer cell survival. Additionally, LPIN1 increased the production of lipid droplets, which play an important role in TKI drug resistance. All results were recapitulated in a patient-derived EGFR-mutant NSCLC cell line. In in vivo tumorigenesis assay, we identified that both shRNA-mediated depletion and pharmaceutical inhibition of LPIN1 clearly reduced tumor growth and confirmed that gefitinib treatment induced LPIN1 expression and LPIN1-dependent NF-κB activation (an increase in p-IκBα level) in tumor tissues. These results suggest an effective strategy of co-treating TKIs and LPIN1 inhibitors to prevent TKI resistance in NSCLC patients.

The natural product berberine synergizes with osimertinib preferentially against MET-amplified osimertinib-resistant lung cancer via direct MET inhibition

Berberine is a natural product that has long been used in traditional Chinese medicine due to its antimicrobial, anti-inflammatory and metabolism-regulatory properties. Osimertinib is the first third-generation EGFR-tyrosine kinase inhibitor (TKI) approved for the treatment of non-small cell lung cancer (NSCLC) with activating EGFR mutations and those resistant to earlier generation EGFR-TKIs due to a T790M mutation. However, emergence of acquired resistance to osimertinib limits its long-term efficacy in the clinic. One known mechanism of acquired resistance to osimertinib and other EGFR-TKIs is MET (c-MET) gene amplification. Here, we report that berberine, when combined with osimertinib, synergistically and selectively decreased the survival of several MET-amplified osimertinib-resistant EGFR mutant NSCLC cell lines with enhanced induction of apoptosis likely through Bim elevation and Mcl-1 reduction. Importantly, this combination effectively enhanced suppressive effect on the growth of MET-amplified osimertinib-resistant xenografts in nude mice and was well tolerated. Molecular modeling showed that berberine was able to bind to the kinase domain of non-phosphorylated MET, occupy the front of the binding pocket, and interact with the activation loop, in a similar way as other known MET inhibitors do. MET kinase assay showed clear concentration-dependent inhibitory effects of berberine against MET activity, confirming its kinase inhibitory activity. These findings collectively suggest that berberine can act as a naturally-existing MET inhibitor to synergize with osimertinib in overcoming osimertinib acquired resistance caused by MET amplification.

Induction of SREBP1 degradation coupled with suppression of SREBP1-mediated lipogenesis impacts the response of EGFR mutant NSCLC cells to osimertinib.

Emergence of acquired resistance to osimertinib (AZD9291), the first-approved third-generation EGFR inhibitor that selectively and irreversibly inhibits the activating EGFR mutations and the resistant T790M mutation, is a giant and urgent clinical challenge. Fully understanding the biology underlying the response of EGFR mutant non-small cell lung cancer (NSCLC) to osimertinib is the foundation for development of mechanism-driven strategies to overcome acquired resistance to osimertinib or other third-generation EGFR inhibitors. This study focused on tackling this important issue by elucidating the critical role of sterol regulatory element-binding protein 1 (SREBP1) degradation in conferring the response of EGFR mutant NSCLC cells to osimertinib and by validating the strategy via directly targeting SREBP1 for overcoming osimertinib acquired resistance. Osimertinib facilitated degradation of the mature form of SREBP1 (mSREBP1) in a GSK3/FBXW7-dependent manner and reduced protein levels of its regulated genes in EGFR-mutant NSCLC cells/tumors accompanied with suppression of lipogenesis. Once resistant, EGFR-mutant NSCLC cell lines possessed elevated levels of mSREBP1, which were resistant to osimertinib modulation. Both genetic and pharmacological inhibition of SREBP1 sensitized osimertinib-resistant cells and tumors to osimertinib primarily through enhancing Bim-dependent induction of apoptosis, whereas enforced expression of ectopic SREBP1 in sensitive EGFR-mutant NSCLC cells compromised osimertinib's cell-killing effects. Collectively, we have demonstrated a novel connection between osimertinib and SREBP1 degradation and its impact on the response of EGFR mutant NSCLC cells to osimertinib and suggested an effective strategy for overcoming acquired resistance to osimertinib, and possibly other EGFR inhibitors, via targeting SREBP1.

Inhibition of MEK5/ERK5 signaling overcomes acquired resistance to the third generation EGFR inhibitor, osimertinib, via enhancing Bim-dependent apoptosis.

The promising therapeutic efficacy of the third generation EGFR inhibitor, osimertinib (AZD9291), for the treatment of patients with EGFR-mutant non-small cell lung cancer (NSCLC) has been demonstrated in the clinic both as first-line and second line therapy. However, inevitable acquired resistance limits its long-term benefit to patients and is thus a significant clinical challenge. The current study focuses on studying the potential role of targeting MEK5-ERK5 signaling in overcoming acquired resistance to osimertinib. Osimertinib and other third generation EGFR inhibitors exerted a rapid and sustained suppressive effect on ERK5 phosphorylation primarily in EGFR-mutant NSCLC cell lines and lost this activity in some osimertinib-resistant cell lines. Osimertinib combined with either ERK5 or MEK5 inhibitors synergistically decreased the survival of osimertinib-resistant cell lines with enhanced induction of apoptosis primarily via augmenting Bim expression. Moreover, the combination effectively inhibited the growth of osimertinib-resistant xenografts in vivo. Together, these findings suggest the potential role of MEK5-ERK5 signaling in modulating development of acquired resistance to osimertinib and value of targeting this signaling as a potential strategy in overcoming acquired resistance to osimertinib and possibly other third generation EGFR inhibitors.

Trametinib overcomes KRAS-G12V-induced osimertinib resistance in a leptomeningeal carcinomatosis model of EGFR-mutant lung cancer.

Leptomeningeal carcinomatosis (LMC) occurs frequently in non–small cell lung cancer (NSCLC) harboring epidermal growth factor receptor (EGFR) mutations and is associated with acquired resistance to EGFR tyrosine kinase inhibitors (EGFR‐TKIs). However, the mechanism by which LMC acquires resistance to osimertinib, a third‐generation EGFR‐TKI, is unclear. In this study, we elucidated the resistance mechanism and searched for a novel therapeutic strategy. We induced osimertinib resistance in a mouse model of LMC using an EGFR‐mutant NSCLC cell line (PC9) via continuous oral osimertinib treatment and administration of established resistant cells and examined the resistance mechanism using next‐generation sequencing. We detected the Kirsten rat sarcoma (KRAS)‐G12V mutation in resistant cells, which retained the EGFR exon 19 deletion. Experiments involving KRAS knockdown in resistant cells and KRAS‐G12V overexpression in parental cells revealed the involvement of KRAS‐G12V in osimertinib resistance. Cotreatment with trametinib (a MEK inhibitor) and osimertinib resensitized the cells to osimertinib. Furthermore, in the mouse model of LMC with resistant cells, combined osimertinib and trametinib treatment successfully controlled LMC progression. These findings suggest a potential novel therapy against KRAS‐G12V–harboring osimertinib‐resistant LMC in EGFR‐mutant NSCLC.

Targeting c-Myc to Overcome Acquired Resistance of EGFR Mutant NSCLC Cells to the Third-Generation EGFR Tyrosine Kinase Inhibitor, Osimertinib.

Osimertinib (AZD9291 or TAGRISSO) is a promising and approved third-generation EGFR tyrosine kinase inhibitor (TKI) for treating patients with advanced non-small cell lung cancer (NSCLC) harboring EGFR-activating mutations or the resistant T790M mutation. However, the inevitable emergence of acquired resistance limits its long-term efficacy. A fuller understanding of the mechanism of action of osimertinib and its linkage to acquired resistance will enable the development of more efficacious therapeutic strategies. Consequently, we have identified a novel connection between osimertinib or other EGFR-TKIs and c-Myc. Osimertinib rapidly and sustainably decreased c-Myc levels primarily via enhancing protein degradation in EGFR-mutant (EGFRm) NSCLC cell lines and xenograft tumors. c-Myc levels were substantially elevated in different EGFRm NSCLC cell lines with acquired resistance to osimertinib in comparison with their corresponding parental cell lines and could not be reduced any further by osimertinib. Consistently, c-Myc levels were elevated in the majority of EGFRm NSCLC tissues relapsed from EGFR-TKI treatment compared with their corresponding untreated baseline c-Myc levels. Suppression of c-Myc through knockdown or pharmacologic targeting with BET inhibitors restored the response of resistant cell lines to osimertinib. These findings indicate that c-Myc modulation mediates the therapeutic efficacy of osimertinib and the development of osimertinib acquired resistance. Furthermore, they establish c-Myc as a potential therapeutic target and warrant clinical testing of BET inhibition as a potential strategy to overcome acquired resistance to osimertinib or other EGFR inhibitors. SIGNIFICANCE: This study demonstrates a critical role of c-Myc modulation in mediating therapeutic efficacy of osimertinib including osimertinib acquired resistance and suggests targeting c-Myc as a potential strategy to overcome osimertinib acquired resistance.