Functional heterogeneity of non-small lung adenocarcinoma cell sub-populations

Construction of a prognostic model based on memory CD4+ T cell-associated genes for lung adenocarcinoma and its applications in immunotherapy

The association between memory CD4+ T cells and cancer prognosis is increasingly recognized, but their impact on lung adenocarcinoma (LUAD) prognosis remains unclear. In this study, using the cell-type identification by estimating relative subsets of RNA transcripts algorithm, we analyzed immune cell composition and patient survival in LUAD. Weighted gene coexpression network analysis helped identify memory CD4+ T cell-associated gene modules. Combined with module genes, a five-gene LUAD prognostic risk model (HOXB7, MELTF, ABCC2, GNPNAT1, and LDHA) was constructed by regression analysis. The model was validated using the GSE31210 data set. The validation results demonstrated excellent predictive performance of the risk scoring model. Correlation analysis was conducted between the clinical information and risk scores of LUAD samples, revealing that LUAD patients with disease progression exhibited higher risk scores. Furthermore, univariate and multivariate regression analyses demonstrated the model independent prognostic capability. The constructed nomogram results demonstrated that the predictive performance of the nomogram was superior to the prognostic model and outperformed individual clinical factors. Immune landscape assessment was performed to compare different risk score groups. The results revealed a better prognosis in the low-risk group with higher immune infiltration. The low-risk group also showed potential benefits from immunotherapy. Our study proposes a memory CD4+ T cell-associated gene risk model as a reliable prognostic biomarker for personalized treatment in LUAD patients.

CD43 (sialophorin) is involved in the induction of extracellular matrix remodeling and angiogenesis by lung cancer cells

Aberrant expression of CD43 in malignant tumors of nonhematopoietic origin such as those from lung, cervix, colon, and breast has been shown to correlate with poor prognosis, providing tumor cells with enhanced motility, anchorage-independent growth, and in vivo tumor size, while protecting the cells of NK lysis and apoptosis. To further characterize the role of CD43 in cell transformation, we tested whether interfering its expression modified the capacity of the A549 non-small cell lung cancer cells to secrete molecules contributing to malignancy. The proteomic analysis of the secretome of serum-starved A549 cells revealed that cells expressing normal levels of CD43 released significantly high levels of molecules involved in extracellular matrix organization, angiogenesis, platelet degranulation, collagen degradation, and inflammation, as compared to CD43 RNAi cells. This data reveals a novel and unexpected role for CD43 in lung cancer development, mainly in remodeling the tumor microenvironment.

Fenofibrate Interferes with the Diapedesis of Lung Adenocarcinoma Cells through the Interference with Cx43/EGF-Dependent Intercellular Signaling

Extravasation of circulating cancer cells is regulated by the intercellular/intracellular signaling pathways that locally impair the endothelial barrier function. Co-cultures of human umbilical vein endothelial cells (HUVECs) with lung adenocarcinoma A549 cells enabled us to identify these pathways and to quantify the effect of fenofibrate (FF) on their activity. A549 cells induced the disruption and local activation of endothelial continuum. These events were accompanied by epidermal growth factor (EGF) up-regulation in endothelial cells. Impaired A549 diapedesis and HUVEC activation were seen upon the chemical inhibition of connexin(Cx)43 functions, EGF/ERK1/2-dependent signaling, and RhoA/Rac1 activity. A total of 25 μM FF exerted corresponding effects on Cx43-mediated gap junctional coupling, EGF production, and ERK1/2 activation in HUVEC/A549 co-cultures. It also directly augmented endothelial barrier function via the interference with focal adhesion kinase (FAK)/RhoA/Rac1-regulated endothelial cell adhesion/contractility/motility and prompted the selective transmigration of epithelioid A549 cells. N-acetyl-L-cysteine abrogated FF effects on HUVEC activation, suggesting the involvement of PPARα-independent mechanism(s) in its action. Our data identify a novel Cx43/EGF/ERK1/2/FAK/RhoA/Rac1-dependent signaling axis, which determines the efficiency of lung cancer cell diapedesis. FF interferes with its activity and reduces the susceptibility of endothelial cells to A549 stimuli. These findings provide the rationale for the implementation of FF in the therapy of malignant lung cancers.

Invasive bronchial fibroblasts derived from asthmatic patients activate lung cancer A549 cells in vitro

Epidemiological data suggests that there are functional links between bronchial asthma and lung carcinogenesis. Bronchial fibroblasts serve a prominent role in the asthmatic process; however, their involvement in lung cancer progression remains unaddressed. To estimate the effect of the asthmatic microenvironment on the invasiveness of lung cancer cells, the present study compared the behavior of human non-small cell lung cancer A549 cells exposed to the signals from human bronchial fibroblasts (HBFs) derived from non-asthmatic donors (NA HBFs) and from asthmatic patients (AS HBFs). NA HBFs did not significantly affect A549 motility, whereas AS HBFs and the media conditioned with AS HBF/A549 co-cultures increased Snail-1/connexin43 expression and motility of A549 cells. In contrast to NA HBFs, which formed A549-impenetrable lateral barriers, α-SMA⁺ AS HBFs actively infiltrated A549 monolayers and secreted chemotactic factors that arrested A549 cells within AS HBF/A549 contact zone. However, small sub-populations of A549 cells could release from this arrest and colonize distant regions of AS HBF monolayers. These data indicated that the interactions between lung cancer cells and HBFs in asthmatic bronchi may facilitate the colonization of lung tumors by fibroblasts. It further stabilizes the tumor microenvironment and potentially facilitates collective colonization of novel bronchial loci by cancer cells. Potential mechanistic links between the asthmatic process and lung cancer progression suggest that bronchial asthma should be included in the list of potential prognostic markers for lung cancer therapy.

Adaptable stirred-tank culture strategies for large scale production of multicellular spheroid-based tumor cell models

Currently there is an effort toward the development of in vitro cancer models more predictive of clinical efficacy. The onset of advanced analytical tools and imaging technologies has increased the utilization of spheroids in the implementation of high throughput approaches in drug discovery. Agitation-based culture systems are commonly proposed as an alternative method for the production of tumor spheroids, despite the scarce experimental evidence found in the literature. In this study, we demonstrate the robustness and reliability of stirred-tank cultures for the scalable generation of 3D cancer models. We developed standardized protocols to a panel of tumor cell lines from different pathologies and attained efficient tumor cell aggregation by tuning hydrodynamic parameters. Large numbers of spheroids were obtained (typically 1000-1500 spheroids/mL) presenting features of native tumors, namely morphology, proliferation and hypoxia gradients, in a cell line-dependent mode. Heterotypic 3D cancer models, based on co-cultures of tumor cells and fibroblasts, were also established in the absence or presence of additional physical support from an alginate matrix, with maintenance of high cell viability. Altogether, we demonstrate that 3D tumor cell model production in stirred-tank culture systems is a robust and versatile approach, providing reproducible tools for drug screening and target verification in pre-clinical oncology research.

Functional links between Snail-1 and Cx43 account for the recruitment of Cx43-positive cells into the invasive front of prostate cancer

Suppressive function of connexin(Cx)43 in carcinogenesis was recently contested by reports that showed a multifaceted function of Cx43 in cancer progression. These studies did not attempt to model the dynamics of intratumoral heterogeneity involved in the metastatic cascade. An unorthodox look at the phenotypic heterogeneity of prostate cancer cells in vitro enabled us to identify links between Cx43 functions and Snail-1-regulated functional speciation of invasive cells. Incomplete Snail-1-dependent phenotypic shifts accounted for the formation of phenotypically stable subclones of AT-2 cells. These subclones showed diverse predilection for invasive behavior. High Snail-1 and Cx43 levels accompanied high motility and nanomechanical elasticity of the fibroblastoid AT-2_Fi2 subclone, which determined its considerable invasiveness. Transforming growth factor-β and ectopic Snail-1 overexpression induced invasiveness and Cx43 expression in epithelioid AT-2 subclones and DU-145 cells. Functional links between Snail-1 function and Cx43 expression were confirmed by Cx43 downregulation and phenotypic shifts in AT-2_Fi2, DU-145 and MAT-LyLu cells upon Snail-1 silencing. Corresponding morphological changes and Snail-1 downregulation were seen upon Cx43 silencing in AT-2_Fi2 cells. This indicates that feedback loops between both proteins regulate cell invasive behavior. We demonstrate that Cx43 may differentially predispose prostate cancer cells for invasion in a coupling-dependent and coupling-independent manner. When extrapolated to in vivo conditions, these data show the complexity of Cx43 functions during the metastatic cascade of prostate cancer. They may explain how Cx43 confers a selective advantage during cooperative invasion of clonally evolving, invasive prostate cancer cell subpopulations.

Connexins, gap junctions and tissue invasion

Formation of metastases negatively impacts the survival prognosis of cancer patients. Globally, if the various steps involved in their formation are relatively well identified, the molecular mechanisms responsible for the emergence of invasive cancer cells are still incompletely resolved. Elucidating what are the mechanisms that allow cancer cells to evade from the tumor is a crucial point since it is the first step of the metastatic potential of a solid tumor. In order to be invasive, cancer cells have to undergo transformations such as down-regulation of cell-cell adhesions, modification of cell-matrix adhesions and acquisition of proteolytic properties. These transformations are accompanied by the capacity to "activate" stromal cells, which may favor the motility of the invasive cells through the extracellular matrix. Since modulation of gap junctional intercellular communication is known to be involved in cancer, we were interested to consider whether these different transformations necessary for the acquisition of invasive phenotype are related with gap junctions and their structural proteins, the connexins. In this review, emerging roles of connexins and gap junctions in the process of tissue invasion are proposed.

Triterpene saponosides from Lysimachia ciliata differentially attenuate invasive potential of prostate cancer cells

Neither androgen ablation nor chemotherapeutic agents are effective in reducing the risk of prostate cancer progression. On the other hand, multifaceted effects of phytochemicals, such as triterpene saponins, on cancer cells have been suggested. A promising safety and tolerability profile indicate their possible application in the treatment of advanced prostate cancers. We analyzed the specificity, selectivity and versatility of desglucoanagalloside B effects on human prostate cancer cells derived from prostate cancer metastases to brain (DU-145 cells) and bone (PC-3 cells). Prominent growth arrest and apoptotic response of both cell types was observed in the presence of sub-micromolar desglucoanagalloside B concentrations. This was accompanied by cytochrome c release and caspase 3/7 activation. A relatively low cytostatic and pro-apoptotic response of cancer cells to a desglucoanagalloside B analog, anagallosaponin IV, illustrated the specificity of the effects of desglucoanagalloside B, whereas the low sensitivity of normal prostate PNT2 cells to desglucoanagalloside B showed the selectivity of its action. Inhibition of cancer cell motility was observed in the presence of both saponins, however only desglucoanagalloside B attenuated cancer cell invasive potential, predominantly through an effect on cell elastic properties. These data demonstrate the versatility of its effects on prostate cancer cells. In contrast to PNT2 cells, cancer cells tested in this study were relatively resistant to mitoxantrone. The multifaceted action of desglucoanagalloside B on basic cellular traits, crucial for prostate cancer progression, opens perspectives for elaboration of combined palliative therapies and new prostate cancer prophylaxis regimens.