Systematic Analysis of Cytostatic TGF-Beta Response in Mesenchymal-Like Hepatocellular Carcinoma Cell Lines

Acetamiprid-induced pulmonary toxicity via oxidative stress, epithelial-mesenchymal transition, apoptosis, and extracellular matrix accumulation in human lung epithelial cells and fibroblasts: Protective role of heat-killed Lactobacilli

Acetamiprid (ACE) is a neonicotinoid insecticide with widespread global application, resulting in persistent human exposure. The current research examined the toxicological implications of ACE exposure on human lung fibroblasts (MRC-5 cells) and bronchial epithelial cells (BEAS-2B cells). The following implications were explored: oxidative stress, epithelial-mesenchymal transition, apoptosis, cellular proliferation, and extracellular matrix accumulation. The prospective protective properties of heat-killed Lactobacillus fermentum and Lactobacillus delbrueckii (HKL) were further studied. The 14-day exposure to ACE at 4 μM triggered oxidative stress and inflammation. ACE promoted epithelial-mesenchymal transition, as evidenced by the decline of protein and mRNA abundances of E-cadherin alongside increased protein and mRNA quantities of α-SMA and N-cadherin in BEAS-2B cells. Additionally, it elicited apoptosis in BEAS-2B cells and stimulated the cellular growth of MRC-5 cells. The TGF-β1/Smad pathway was activated upon ACE exposure, leading to the accumulation of extracellular matrix. HKL demonstrated antioxidant, anti-apoptotic, anti-proliferative, and anti-fibrotic properties, mitigating ACE-induced toxicity. Our findings delineate the molecular mechanisms underlying epithelial-mesenchymal transition, inflammation, oxidative stress, and extracellular matrix accumulation in ACE-induced pulmonary fibrosis, which provides new insights into pulmonary injury. Additionally, this investigation would offer us an approach to mitigate lung deterioration induced by ACE through utilizing heat-killed probiotic supplementation.

Escape from TGF-β-induced senescence promotes aggressive hallmarks in epithelial hepatocellular carcinoma cells

Transforming growth factor-β (TGF-β) signaling and cellular senescence are key hallmarks of hepatocellular carcinoma (HCC) pathogenesis. Despite provoking senescence-associated growth arrest in epithelial HCC cells, elevated TGF-β activity paradoxically correlates with increased aggressiveness and poor prognosis in advanced tumors. Whether the transition between these dichotomous functions involves modulation of the senescence phenotype during disease progression remains elusive. Exploiting the epithelial HCC cell line Huh7 as a robust model, we demonstrate that chronic exposure to TGF-β prompts escape from Smad3-mediated senescence, leading to the development of TGF-β resistance. This altered state is characterized by an optimal proliferation rate and the acquisition of molecular and functional traits of less-differentiated mesenchymal cells, coinciding with differential growth capacity in 2D and 3D culture conditions, epithelial-to-mesenchymal transition (EMT), and increased invasiveness in vitro, and metastasis in vivo. Mechanistically, resistant cells exhibit defective activation and nuclear trafficking of Smad molecules, particularly Smad3, as ectopic activation of the TGF-β/Smad3 axis is able to reinstate TGF-β sensitivity. An integrated transcriptomic landscape reveals both shared and distinct gene signatures associated with senescent and TGF-β resistant states. Importantly, genetic ablation and molecular studies identify microtubule affinity regulating kinase 1 (MARK1) and glutamate metabotropic receptor 8 (GRM8) as critical modulators of the resistance phenomenon, potentially by impairing spatiotemporal signaling dynamics of Smad activity. Our findings unveil a novel phenomenon wherein epithelial HCC cells may exploit senescence plasticity as a mechanism to oppose TGF-β anti-tumor responses and progress towards more aggressive HCC phenotypes.

The paracaspase MALT1 is a downstream target of Smad3 and potentiates the crosstalk between TGF-β and NF-kB signaling pathways in cancer cells

TGF-β signaling mediates its biological effects by engaging canonical Smad proteins and crosstalking extensively with other signaling networks, including the NF-kB pathway. The paracaspase MALT1 is an intracellular signaling molecule essential for NF-kB activation downstream of several key cell surface receptors. Despite intensive research on TGF-β and NF-kB interactions, the significance of MALT1 in this context remains undecoded. Here we provide experimental evidence supporting that MALT1 functions to converge these pathways. Using A549 and Huh7 cancer cell line models, we report that TGF-β stimulation enhances MALT1 protein and transcript levels in a time- and dose-dependent manner. Systematic and selective perturbation of TGF-β signaling components identifies MALT1 as a downstream target of Smad3. Rescue experiments in SMAD3 knockout cells confirm that C-terminal phosphorylation of Smad3 is central to MALT1 induction. Corroborating these data, we document that the expression of SMAD3 and MALT1 genes are positively correlated in TCGA cohorts, and we trace the molecular basis of MALT1 elevation to promoter activation. Functional studies in parental as well as NF-kB p65 signaling reporter engineered cells conclusively reveal that MALT1 is paramount for TGF-β-stimulated nuclear translocation and transcriptional activation of NF-kB p65. Furthermore, we find that BCL10 is also implicated in TGF-β activation of NF-kB target genes, potentially coupling the TGF-β-MALT1-NF-kB signaling axis to the CARMA-BCL10-MALT1 (CBM) signalosome. The novel findings of this study indicate that MALT1 is a downstream target of the canonical TGF-β/Smad3 pathway and plays a critical role in modulating TGF-β and NF-kB crosstalk in cancer.

MALT1 paracaspase is overexpressed in hepatocellular carcinoma and promotes cancer cell survival and growth

Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer and the third leading cause of cancer-related deaths worldwide. Despite recent advances in treatment options, therapeutic management of HCC remains a challenge, emphasizing the importance of exploring novel targets. MALT1 paracaspase is a druggable signaling molecule whose dysregulation has been linked to hematological and solid tumors. However, the role of MALT1 in HCC remains poorly understood, leaving its molecular functions and oncogenic implications unclear. Here we provide evidence that MALT1 expression is elevated in human HCC tumors and cell lines, and that correlates with tumor grade and differentiation state, respectively. Our results indicate that ectopic expression of MALT1 confers increased cell proliferation, 2D clonogenic growth, and 3D spheroid formation in well differentiated HCC cell lines with relatively low MALT1 levels. In contrast, stable silencing of endogenous MALT1 through RNA interference attenuates these aggressive cancer cell phenotypes, as well as migration, invasion, and tumor-forming ability, in poorly differentiated HCC cell lines with higher paracaspase expression. Consistently, we find that pharmacological inhibition of MALT1 proteolytic activity with MI-2 recapitulates MALT1 depletion phenotypes. Finally, we show that MALT1 expression is positively correlated with NF-kB activation in human HCC tissues and cell lines, suggesting that its tumor promoting functions may involve functional interaction with the NF-kB signaling pathway. This work unveils new insights into the molecular implications of MALT1 in hepatocarcinogenesis and places this paracaspase as a potential marker and druggable liability in HCC.

The Bright and the Dark Side of TGF-β Signaling in Hepatocellular Carcinoma: Mechanisms, Dysregulation, and Therapeutic Implications

Simple Summary

Transforming growth factor β (TGF-β) signaling is a preeminent regulator of diverse cellular and physiological processes. Frequent dysregulation of TGF-β signaling has been implicated in cancer. In hepatocellular carcinoma (HCC), the most prevalent form of primary liver cancer, the autocrine and paracrine effects of TGF-β have paradoxical implications. While acting as a potent tumor suppressor pathway in the early stages of malignancy, TGF-β diverts to a promoter of tumor progression in the late stages, reflecting its bright and dark natures, respectively. Within this context, targeting TGF-β represents a promising therapeutic option for HCC treatment. We discuss here the molecular properties of TGF-β signaling in HCC, attempting to provide an overview of its effects on tumor cells and the stroma. We also seek to evaluate the dysregulation mechanisms that mediate the functional switch of TGF-β from a tumor suppressor to a pro-tumorigenic signal. Finally, we reconcile its biphasic nature with the therapeutic implications.

Abstract

Hepatocellular carcinoma (HCC) is associated with genetic and nongenetic aberrations that impact multiple genes and pathways, including the frequently dysregulated transforming growth factor β (TGF-β) signaling pathway. The regulatory cytokine TGF-β and its signaling effectors govern a broad spectrum of spatiotemporally regulated molecular and cellular responses, yet paradoxically have dual and opposing roles in HCC progression. In the early stages of tumorigenesis, TGF-β signaling enforces profound tumor-suppressive effects, primarily by inducing cell cycle arrest, cellular senescence, autophagy, and apoptosis. However, as the tumor advances in malignant progression, TGF-β functionally switches to a pro-tumorigenic signal, eliciting aggressive tumor traits, such as epithelial–mesenchymal transition, tumor microenvironment remodeling, and immune evasion of cancer cells. On this account, the inhibition of TGF-β signaling is recognized as a promising therapeutic strategy for advanced HCC. In this review, we evaluate the functions and mechanisms of TGF-β signaling and relate its complex and pleiotropic biology to HCC pathophysiology, attempting to provide a detailed perspective on the molecular determinants underlying its functional diversion. We also address the therapeutic implications of the dichotomous nature of TGF-β signaling and highlight the rationale for targeting this pathway for HCC treatment, alone or in combination with other agents.