HMGB1 promotes chemoresistance in small cell lung cancer by inducing PARP1-related nucleophagy.

INTRODUCTION: Small cell lung cancer (SCLC) is prone to chemoresistance, which is closely related to genome homeostasis-related processes, such as DNA damage and repair. Nucleophagy is the elimination of specific nuclear substances by cells themselves and is responsible for maintaining genome and chromosome stability. However, the roles of nucleophagy in tumour chemoresistance have not been investigated. OBJECTIVES: The aim of this work was to elucidate the mechanism of chemoresistance in SCLC and reverse this chemoresistance. METHODS: RNA-seq data from SCLC cohorts, chemosensitive SCLC cells and the corresponding chemoresistant cells were used to discover genes associated with chemoresistance and patient prognosis. In vitro and in vivo experiments were performed to verify the effect of high-mobility group box 1 (HMGB1) knockdown or overexpression on the chemotherapeutic response in SCLC. The regulatory effect of HMGB1 on nucleophagy was then investigated by coimmunoprecipitation (co-IP) and mass spectrometry (MS), and the underlying mechanism was explored using pharmacological inhibitors and mutant proteins. RESULTS: HMGB1 is a factor indicating poor prognosis and promotes chemoresistance in SCLC. Mechanistically, HMGB1 significantly increases PARP1-LC3 binding to promote nucleophagy via PARP1 PARylation, which leads to PARP1 turnover from DNA lesions and chemoresistance. Furthermore, chemoresistance in SCLC can be attenuated by blockade of the PARP1-LC3 interaction or PARP1 inhibitor (PARPi) treatment. CONCLUSIONS: HMGB1 can induce PARP1 self-modification, which promotes the interaction of PARP1 with LC3 to promote nucleophagy and thus chemoresistance in SCLC. HMGB1 could be a predictive biomarker for the PARPi response in patients with SCLC. Combining chemotherapy with PARPi treatment is an effective therapeutic strategy for overcoming SCLC chemoresistance.

METTL3 promotes chemoresistance in small cell lung cancer by inducing mitophagy.

BACKGROUND: Small cell lung cancer (SCLC) is the most aggressive subtype of lung cancer. Although most patients are initially sensitive to first-line combination chemotherapy with cisplatin and etoposide, chemotherapy drug resistance easily develops and quickly leads to tumour progression. Therefore, understanding the mechanisms of chemotherapy drug resistance and how to reverse it is key to improving the prognosis of patients with SCLC. Moreover, N6-methyladenosine (m6A) is the most abundant mRNA modification and is catalysed by the methyltransferase complex, in which methyltransferase-like 3 (METTL3) is the sole catalytic subunit. METHODS: The effects of METTL3 on chemoresistance in SCLC cells were determined using qRT-PCR, Western blotting, immunohistochemistry, cell counting kit (CCK-8) assays, flow cytometry, and tumorigenicity experiments. Methylated RNA immunoprecipitation sequencing (MeRIP-seq), MeRIP qPCR, immunofluorescence, and drug inhibitor experiments were performed to confirm the molecular mechanism of Decapping Protein 2 (DCP2), which is involved in the chemoresistance of SCLC. RESULTS: In the present study, we found that METTL3 is a marker for poor SCLC prognosis, and it is highly expressed in chemoresistant SCLC cells. METTL3 promotes SCLC chemoresistance by positively regulating mitophagy. METTL3 induces m6A methylation of DCP2 and causes the degradation of DCP2, which promotes mitochondrial autophagy through the Pink1-Parkin pathway, leading to chemotherapy resistance. We also found that STM2457, a novel METTL3 inhibitor, can reverse SCLC chemoresistance. CONCLUSIONS: The m6A methyltransferase METTL3 regulates Pink1-Parkin pathway-mediated mitophagy and mitochondrial damage in SCLC cells by targeting DCP2, thereby promoting chemotherapy resistance in patients with SCLC.

NRBF2 regulates the chemoresistance of small cell lung cancer by interacting with the P62 protein in the autophagy process.

Reversing chemotherapy resistance in small cell lung cancer (SCLC) is crucial to improve patient prognosis. The present study aims to investigate the underlying mechanisms in SCLC chemoresistance. We see that nuclear receptor binding factor 2 (NRBF2) is a poor prognostic factor in SCLC. The effects of NRBF2 on chemoresistance were determined in SCLC. The underlying molecular mechanisms of NRBF2 in the autophagy process in SCLC were examined. NRBF2 positively regulated autophagy, leading to drug resistance in SCLC. The MIT domain of NRBF2 directly interacted with the PB1 domain of P62. This interaction increased autophagic P62 body formation, revealing the regulatory role of NRBF2 in autophagy. Notably, NRBF2 was directly modulated by the transcription factor XRCC6. The MIT domain of NRBF2 interacts with the PB1 domain of P62 to regulate the autophagy process, resulting in SCLC chemoresistance. NRBF2 is likely a useful chemotherapy response marker and therapeutic target in SCLC.

Single-Cell RNA Sequencing Reveals the Heterogeneity of Tumor-Associated Macrophage in Non-Small Cell Lung Cancer and Differences Between Sexes.

Non-Small Cell Lung Cancer (NSCLC) is a disease with high morbidity and mortality, which has sex-related differences in prognosis and immunotherapy efficacy. However, the difference in the mechanisms remains unclear. Macrophages, characterized by high plasticity and heterogeneity, act as one of the key cells that exert anti-tumor effects in the tumor microenvironment (TME) and play a complicated role in the process of tumor progression. To elucidate the subtype composition and functional heterogeneity of tumor-associated macrophages (TAMs) in NSCLC and further compare the sex-mediated differences, we conducted a single-cell level analysis in early-stage smoking NSCLC patients, combined with ssGSEA analysis, pseudotime ordering, and SCENIC analysis. We found two universally presented immune-suppressive TAMs with different functional and metabolic characteristics in the TME of NSCLC. Specifically, CCL18+ macrophages exerted immune-suppressive effects by inhibiting the production of inflammatory factors and manifested high levels of fatty acid oxidative phosphorylation metabolism. Conversely, the main metabolism pathway for SPP1+ macrophage was glycolysis which contributed to tumor metastasis by promoting angiogenesis and matrix remodeling. In terms of the differentially expressed genes, the complement gene C1QC and the matrix remodeling relevant genes FN1 and SPP1 were differentially expressed in the TAMs between sexes, of which the male upregulated SPP1 showed the potential as an ideal target for adjuvant immunotherapy and improving the efficacy of immunotherapy. According to the early-stage TCGA-NSCLC cohort, high expression of the above three genes in immune cells were associated with poor prognosis and acted as independent prognostic factors. Moreover, through verification at the transcription factor, transcriptome, and protein levels, we found that TAMs from women showed stronger immunogenicity with higher interferon-producing and antigen-presenting ability, while men-derived TAMs upregulated the PPARs and matrix remodeling related pathways, thus were more inclined to be immunosuppressive. Deconstruction of the TAMs at the single-cell level deepens our understanding of the mechanism for tumor occurrence and progress, which could be helpful to achieve the precise sex-specific tumor treatment sooner.

The Effect of Smoking on the Immune Microenvironment and Immunogenicity and Its Relationship With the Prognosis of Immune Checkpoint Inhibitors in Non-small Cell Lung Cancer.

Background: The emergence of immune checkpoint inhibitors (ICIs) has opened a new chapter for the treatment of non-small cell lung cancer (NSCLC), and the best beneficiaries of ICI treatment are still being explored. Smoking status has been repeatedly confirmed to affect the efficacy of ICIs in NSCLC patients, but the specific mechanism is still unclear. Methods: We performed analysis on the Memorial Sloan Kettering Cancer Center (MSKCC) clinical NSCLC cohort receiving ICI treatment, The Cancer Genome Atlas (TCGA) Pan-Lung Cancer cohort, and Gene Expression Omnibus (GEO) database GSE41271 lung cancer cohort that did not receive ICI treatment, including survival prognosis, gene mutation, copy number variation, immunogenicity, and immune microenvironment, and explored the impact of smoking status on the prognosis of NSCLC patients treated with ICIs and possible mechanism. In addition, 8 fresh NSCLC surgical tissue samples were collected for mass cytometry (CyTOF) experiments to further characterize the immune characteristics and verify the mechanism. Result: Through the analysis of the clinical data of the NSCLC cohort treated with ICIs in MSKCC, it was found that the smokers in NSCLC receiving ICI treatment had a longer progression-free survival (HR: 0.69, 95% CI: 0.49-0.97, p = 0.031) than those who never smoked. Further analysis of the TCGA and GEO validation cohorts found that the differences in prognosis between different groups may be related to the smoking group's higher immunogenicity, higher gene mutations, and stronger immune microenvironment. The results of the CyTOF experiment further found that the immune microenvironment of smoking group was characterized by higher expression of immune positive regulatory chemokine, and higher abundance of immune activated cells, including follicular helper CD4+ T cells, gamma delta CD4+ T cells, activated DC, and activated CD8+ T cells. In contrast, the immune microenvironment of non-smoking group was significantly enriched for immunosuppressive related cells, including regulatory T cells and M2 macrophages. Finally, we also found highly enriched CD45RAhighCD4+ T cells and CD45RAhighCD8+ T cells in the non-smoking group. Conclusion: Our research results suggest that among NSCLC patients receiving ICI treatment, the stronger immunogenicity and activated immune microenvironment of the smoking group make their prognosis better.