Loss of LKB1-NUAK1 signalling enhances NF-κB activity in a spheroid model of high-grade serous ovarian cancer.

High-grade serous ovarian cancer (HGSOC) is an aggressive malignancy often diagnosed at an advanced stage. Although most HGSOC patients respond initially to debulking surgery combined with cytotoxic chemotherapy, many ultimately relapse with platinum-resistant disease. Thus, improving outcomes requires new ways of limiting metastasis and eradicating residual disease. We identified previously that Liver kinase B1 (LKB1) and its substrate NUAK1 are implicated in EOC spheroid cell viability and are required for efficient metastasis in orthotopic mouse models. Here, we sought to identify additional signalling pathways altered in EOC cells due to LKB1 or NUAK1 loss-of-function. Transcriptome analysis revealed that inflammatory signalling mediated by NF-κB transcription factors is hyperactive due to LKB1-NUAK1 loss in HGSOC cells and spheroids. Upregulated NF-κB signalling due to NUAK1 loss suppresses reactive oxygen species (ROS) production and sustains cell survival in spheroids. NF-κB signalling is also activated in HGSOC precursor fallopian tube secretory epithelial cell spheroids, and is further enhanced by NUAK1 loss. Finally, immunohistochemical analysis of OVCAR8 xenograft tumors lacking NUAK1 displayed increased RelB expression and nuclear staining. Our results support the idea that NUAK1 and NF-κB signalling pathways together regulate ROS and inflammatory signalling, supporting cell survival during each step of HGSOC pathogenesis. We propose that their combined inhibition may be efficacious as a novel therapeutic strategy for advanced HGSOC.

Diosmetin inhibits apoptosis and activates AMPK-induced autophagy in myocardial damage under hypoxia environment.

Inhibition of hypoxia-induced cardiomyocyte apoptosis is considered as an important treatment method for ischemic heart diseases, but related drugs are still insufficient. The present study aims to explore the protective function and mechanism of the key Chinese medicine monomer diosmetin (DIOS) on the injury of cardiomyocytes induced by hypoxia. Here, AC16 and HCM-a cells were treated with 40 µM of DIOS under hypoxic environment and a hypoxic rat model was built to study the role of DIOS. The viability and autophagy of cardiomyocytes were increased, but the apoptosis of cells was suppressed by 40 µM DIOS, under hypoxic environment. Intriguingly, 10 mM 3-methyladenine, an inhibitor of autophagy, reversed the effect of DIOS on autophagy and apoptosis of the cardiomyocytes under hypoxia. Furthermore, DIOS induced AMP-activated protein kinase (AMPK) activation and Compound C (5 µM), an AMPK inhibitor, attenuated the inhibition of DIOS on the apoptosis of cardiomyocytes under hypoxia environment. In isoprenaline-induced hypoxic rats, it was verified that DIOS inhibited apoptosis, accelerated autophagy, and activated AMPKα pathway in vivo. Our findings indicated that DIOS alleviated hypoxia-induced myocardial apoptosis via inducing the activation of AMPK-induced autophagy. In summary, the study suggested that DIOS inhibited the apoptosis and induced the autophagy of hypoxia-induced cardiomyocytes through AMPK activation.

LKB1 deficiency upregulates RELM-α to drive airway goblet cell metaplasia.

Targeting airway goblet cell metaplasia is a novel strategy that can potentially reduce the chronic obstructive pulmonary disease (COPD) symptoms. Tumor suppressor liver kinase B1 (LKB1) is an important regulator of the proliferation and differentiation of stem/progenitor cells. In this study, we report that LKB1 expression was downregulated in the lungs of patients with COPD and in those of cigarette smoke-exposed mice. Nkx2.1Cre; Lkb1f/f mice with conditional loss of Lkb1 in mouse lung epithelium displayed airway mucus hypersecretion and pulmonary macrophage infiltration. Single-cell transcriptomic analysis of the lung tissues from Nkx2.1Cre; Lkb1f/f mice further revealed that airway goblet cell differentiation was altered in the absence of LKB1. An organoid culture study demonstrated that Lkb1 deficiency in mouse airway (club) progenitor cells promoted the expression of FIZZ1/RELM-α, which drove airway goblet cell differentiation and pulmonary macrophage recruitment. Additionally, monocyte-derived macrophages in the lungs of Nkx2.1Cre; Lkb1f/f mice exhibited an alternatively activated M2 phenotype, while expressing RELM-α, which subsequently aggravated airway goblet cell metaplasia. Our findings suggest that the LKB1-mediated crosstalk between airway progenitor cells and macrophages regulates airway goblet cell metaplasia. Moreover, our data suggest that LKB1 agonists might serve as a potential therapeutic option to treat respiratory disorders associated with goblet cell metaplasia.

STK11/LKB1 Loss of Function Is Associated with Global DNA Hypomethylation and S-Adenosyl-Methionine Depletion in Human Lung Adenocarcinoma.

STK11 (liver kinase B1, LKB1) is the fourth most frequently mutated gene in lung adenocarcinoma, with loss of function observed in up to 30% of all cases. Our previous work identified a 16-gene signature for LKB1 loss of function through mutational and nonmutational mechanisms. In this study, we applied this genetic signature to The Cancer Genome Atlas (TCGA) lung adenocarcinoma samples and discovered a novel association between LKB1 loss and widespread DNA demethylation. LKB1-deficient tumors showed depletion of S-adenosyl-methionine (SAM-e), which is the primary substrate for DNMT1 activity. Lower methylation following LKB1 loss involved repetitive elements (RE) and altered RE transcription, as well as decreased sensitivity to azacytidine. Demethylated CpGs were enriched for FOXA family consensus binding sites, and nuclear expression, localization, and turnover of FOXA was dependent upon LKB1. Overall, these findings demonstrate that a large number of lung adenocarcinomas exhibit global hypomethylation driven by LKB1 loss, which has implications for both epigenetic therapy and immunotherapy in these cancers. SIGNIFICANCE: Lung adenocarcinomas with LKB1 loss demonstrate global genomic hypomethylation associated with depletion of SAM-e, reduced expression of DNMT1, and increased transcription of repetitive elements.