LTK mutations responsible for resistance to lorlatinib in non-small cell lung cancer harboring CLIP1-LTK fusion.

The CLIP1-LTK fusion was recently discovered as a novel oncogenic driver in non-small cell lung cancer (NSCLC). Lorlatinib, a third-generation ALK inhibitor, exhibited a dramatic clinical response in a NSCLC patient harboring CLIP1-LTK fusion. However, it is expected that acquired resistance will inevitably develop, particularly by LTK mutations, as observed in NSCLC induced by oncogenic tyrosine kinases treated with corresponding tyrosine kinase inhibitors (TKIs). In this study, we evaluate eight LTK mutations corresponding to ALK mutations that lead to on-target resistance to lorlatinib. All LTK mutations show resistance to lorlatinib with the L650F mutation being the highest. In vitro and in vivo analyses demonstrate that gilteritinib can overcome the L650F-mediated resistance to lorlatinib. In silico analysis suggests that introduction of the L650F mutation may attenuate lorlatinib-LTK binding. Our study provides preclinical evaluations of potential on-target resistance mutations to lorlatinib, and a novel strategy to overcome the resistance.

Prognostic impact and gene expression analysis of peri-tumoral alveolar macrophage in resected lung adenocarcinoma.

The prognostic significance and role of extratumoral alveolar macrophages (exAMs) in lung adenocarcinoma (LUAD) patients remain unknown. In this study, we investigated the prognostic impact and gene expression of exAMs in LUAD patients. The density of alveolar macrophages (AMs) in the peri-tumoral lung field (p-exAMs) and distant lung field (d-exAMs) was evaluated in 217 LUAD patients with lymph node metastasis. Patients with high p-exAMs showed significantly shorter recurrence-free (RFS) and shorter overall survival (OS) than those with low p-exAMs (p = 0.02 and p = 0.03, respectively), whereas there was no survival difference between patients with high d-exAMs and those with low d-exAMs. Multivariate analysis revealed that high p-exAMs was an independent predictive factor for RFS (HR: 1.54; 95% confidence interval [CI]:1.10-2.16; p = 0.01). Later, we collected AMs from the tumor periphery and distant segments in 13 resected lungs by bronchoalveolar lavage (BAL) procedure and compared mRNA expression. AMs in the tumor periphery expressed significantly higher levels of IL-10 and CCL2 than those in the distant segment (p < 0.01 and p = 0.03, respectively). Additionally, IL-10 and CCL2 significantly induced the growth and migration of the PC9 cells in vitro. This study suggests that p-exAMs should be considered as a tumor-promoting component in the tumor microenvironment.

The EGFR C797S Mutation Confers Resistance to a Novel EGFR Inhibitor CLN-081 to EGFR Exon 20 Insertion Mutations.

Introduction: EGFR exon 20 insertion mutations account for 5% to 10% of EGFR-mutated NSCLC. CLN-081 (formerly known as TAS6417), a novel covalent EGFR tyrosine kinase inhibitor, exhibits pan-mutation selective efficacy, including exon 20 insertions, in the clinical setting. Nevertheless, some patients may not respond to CLN-081 and resistance to CLN-081 may emerge over time in others. Methods: We exposed Ba/F3 cells transduced with EGFR exon 20 insertions (Y764_V765 insHH or A767_S768insSVD) to increasing concentrations of CLN-081 to generate resistant cells and then subjected their complementary DNA to sequencing to identify acquired mutations. We then evaluated effects of small molecules on engineered Ba/F3 cells on the basis of proliferation assays, Western blotting, and xenograft models. Results: All CLN-081 resistant clones harbored the EGFR C797S mutation. Ba/F3 cells with C797S (Ba/F3-C797S) were resistant to EGFR tyrosine kinase inhibitors targeting EGFR exon 20 insertion mutations, including CLN-081. Pimitespib, a selective heat shock protein 90 inhibitor, induced apoptosis in Ba/F3-C797S cells in vitro and inhibited growth of Ba/F3-C797S tumors in vivo. Ba/F3 cells with A763_Y764insFQEA-C797S remained sensitive to erlotinib. Conclusions: We conclude that the EGFR C797S mutation confers resistance to CLN-081. Our preclinical data suggest a potential small molecule to overcome CLN-081 resistance, which may benefit patients with lung cancer with EGFR exon 20 insertions.

Clinicopathological significance of peritumoral alveolar macrophages in patients with resected early-stage lung squamous cell carcinoma.

INTRODUCTION: This study aimed to clarify the correlation between the number of AMs and prognosis and to examine the gene expression of AMs in lung squamous cell carcinoma (SqCC). METHODS: We reviewed 124 stage I lung SqCC cases in our hospital and 139 stage I lung SqCC cases in The Cancer Genome Atlas (TCGA) cohort in this study. We counted the number of AMs in the peritumoral lung field (P-AMs) and in the lung field distant from the tumor (D-AMs). Moreover, we performed a novel ex vivo bronchoalveolar lavage fluid (BALF) analysis to select AMs from surgically resected lung SqCC cases and examined the expression of IL10, CCL2, IL6, TGFß, and TNFα (n = 3). RESULTS: Patients with high P-AMs had significantly shorter overall survival (OS) (p < 0.01); however, patients with high D-AMs did not have significantly shorter OS. Moreover, in TCGA cohort, patients with high P-AMs had a significantly shorter OS (p < 0.01). In multivariate analysis, a higher number of P-AMs were an independent poor prognostic factor (p = 0.02). Ex vivo BALF analysis revealed that AMs collected from the tumor vicinity showed higher expression of IL10 and CCL2 than AMs from distant lung fields in all 3 cases (IL-10: 2.2-, 3.0-, and 10.0-fold; CCL-2: 3.0-, 3.1-, and 3.2-fold). Moreover, the addition of recombinant CCL2 significantly increased the proliferation of RERF-LC-AI, a lung SqCC cell line. CONCLUSION: The current results indicated the prognostic impact of the number of peritumoral AMs and suggested the importance of the peritumoral tumor microenvironment in lung SqCC progression.

Primary advanced pulmonary synovial sarcoma treated with a multidisciplinary approach.

A 61-year-old woman was referred to our hospital due to right chest pain. A huge, 13-cm-diameter tumor was detected in the right lower lobe. For diagnostic and treatment purposes, pneumonectomy was performed, and the tumor was diagnosed as advanced pulmonary synovial sarcoma (SS) with pleural metastasis, according to immunohistochemistry analysis. Due to recurrence with brain metastases, treatment sequence composed of radiosurgery, doxorubicin, eribulin, and pazopanib was selected. The patient died after a considerably long survival of 29 months after the first visit. This case suggests that multimodal treatment may provide prolonged survival even for patients with advanced SS.