In recent years, cancer immunotherapy based on immune checkpoint inhibitors (ICIs) has achieved considerable success in the clinic. However, ICIs are significantly limited by the fact that only one third of patients with most types of cancer respond to these agents. The induction of cell death mechanisms other than apoptosis has gradually emerged as a new cancer treatment strategy because most tumors harbor innate resistance to apoptosis. However, to date, the possibility of combining these two modalities has not been discussed systematically. Recently, a few studies revealed crosstalk between distinct cell death mechanisms and antitumor immunity. The induction of pyroptosis, ferroptosis, and necroptosis combined with ICIs showed synergistically enhanced antitumor activity, even in ICI-resistant tumors. Immunotherapy-activated CD8+ T cells are traditionally believed to induce tumor cell death via the following two main pathways: (i) perforin-granzyme and (ii) Fas-FasL. However, recent studies identified a new mechanism by which CD8+ T cells suppress tumor growth by inducing ferroptosis and pyroptosis, which provoked a review of the relationship between tumor cell death mechanisms and immune system activation. Hence, in this review, we summarize knowledge of the reciprocal interaction between antitumor immunity and distinct cell death mechanisms, particularly necroptosis, ferroptosis, and pyroptosis, which are the three potentially novel mechanisms of immunogenic cell death. Because most evidence is derived from studies using animal and cell models, we also reviewed related bioinformatics data available for human tissues in public databases, which partially confirmed the presence of interactions between tumor cell death and the activation of antitumor immunity.

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Ferroptosis, necroptosis, and pyroptosis in anticancer immunity

Programmed cell death (PCD) refers to the way in which cells die depending on specific genes encoding signals or activities. Apoptosis, autophagy, and pyroptosis are all mechanisms of PCD. Among these mechanisms, pyroptosis is mediated by the gasdermin family, accompanied by inflammatory and immune responses. The relationship between pyroptosis and cancer is complex, and the effects of pyroptosis on cancer vary in different tissues and genetic backgrounds. On one hand, pyroptosis can inhibit the occurrence and development of tumors; on the other hand, as a type of proinflammatory death, pyroptosis can form a suitable microenvironment for tumor cell growth and thus promote tumor growth. In addition, the induction of tumor pyroptosis is also considered a potential cancer treatment strategy. Studies have shown that DFNA5 (nonsyndromic hearing impairment protein 5)/GSDME (Gasdermin-E) mRNA methylation results in lower expression levels of DFNA5/GSDME in most tumor cells than in normal cells, making it difficult to activate the pyroptosis in most tumor cells. During the treatment of malignant tumors, appropriate chemotherapeutic drugs can be selected according to the expression levels of DFNA5/GSDME, which can be upregulated in tumor cells, thereby increasing the sensitivity to chemotherapeutic drugs and reducing drug resistance. Therefore, induced pyroptosis may play a predominant role in the treatment of cancer. Here, we review the latest research on the anti- and protumor effects of pyroptosis and its potential applications in cancer treatment.

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The role of pyroptosis in cancer: pro-cancer or pro-"host"?

Trillium tschonoskii Maxim (TTM), a traditional Chinese medicine, has been demonstrated to have a potent anti-tumor effect. Recently, polyphyllin VI (PPVI), a main saponin isolated from TTM, was reported by us to significantly suppress the proliferation of non-small cell lung cancer (NSCLC) via the induction of apoptosis and autophagy in vitro and in vivo. In this study, we further found that the NLRP3 inflammasome was activated in PPVI administrated A549-bearing athymic nude mice. As is known to us, pyroptosis is an inflammatory form of caspase-1-dependent programmed cell death that plays an important role in cancer. By using A549 and H1299 cells, the in vitro effect and action mechanism by which PPVI induces activation of the NLRP3 inflammasome in NSCLC were investigated. The anti-proliferative effect of PPVI in A549 and H1299 cells was firstly measured and validated by MTT assay. The activation of the NLRP3 inflammasome was detected by using Hoechst33324/PI staining, flow cytometry analysis and real-time live cell imaging methods. We found that PPVI significantly increased the percentage of cells with PI signal in A549 and H1299, and the dynamic change in cell morphology and the process of cell death of A549 cells indicated that PPVI induced an apoptosis-to-pyroptosis switch, and, ultimately, lytic cell death. In addition, belnacasan (VX-765), an inhibitor of caspase-1, could remarkably decrease the pyroptotic cell death of PPVI-treated A549 and H1299 cells. Moreover, by detecting the expression of NLRP3, ASC, caspase-1, IL-1β, IL-18 and GSDMD in A549 and h1299 cells using Western blotting, immunofluorescence imaging and flow cytometric analysis, measuring the caspase-1 activity using colorimetric assay, and quantifying the cytokines level of IL-1β and IL-18 using ELISA, the NLRP3 inflammasome was found to be activated in a dose manner, while VX-765 and necrosulfonamide (NSA), an inhibitor of GSDMD, could inhibit PPVI-induced activation of the NLRP3 inflammasome. Furthermore, the mechanism study found that PPVI could activate the NF-κB signaling pathway via increasing reactive oxygen species (ROS) levels in A549 and H1299 cells, and N-acetyl-L-cysteine (NAC), a scavenger of ROS, remarkably inhibited the cell death, and the activation of NF-κB and the NLRP3 inflammasome in PPVI-treated A549 and H1299 cells. Taken together, these data suggested that PPVI-induced, caspase-1-mediated pyroptosis via the induction of the ROS/NF-κB/NLRP3/GSDMD signal axis in NSCLC, which further clarified the mechanism of PPVI in the inhibition of NSCLC, and thereby provided a possibility for PPVI to serve as a novel therapeutic agent for NSCLC in the future.

Polyphyllin VI Induces Caspase-1-Mediated Pyroptosis via the Induction of ROS/NF-κB/NLRP3/GSDMD Signal Axis in Non-Small Cell Lung Cancer

Metformin induces human esophageal carcinoma cell pyroptosis by targeting the miR-497/PELP1 axis.

Emerging evidence suggests that 17β-estradiol (E2) and estrogen receptor (ER) signaling are protective against hepatocellular carcinoma (HCC) In our previous study, we showed that E2 suppressed the carcinogenesis and progression of HCC by targeting NLRP3 inflammasome activation, whereas the molecular mechanism by which the NLRP3 inflammasome initiated cancer cell death was not elucidated The present study aimed to investigate the effect of NLRP3 inflammasome activation on cell death pathways and autophagy of HCC cells First, we observed an increasing mortality in E2-treated HCC cells, and then apoptotic and pyroptotic cell death were both detected The mortality of HCC cells was largely reversed by the caspase 1 antagonist, YVAD-cmk, suggesting that E2-induced cell death was associated with caspase 1-dependent pyroptosis Second, the key role of the NLRP3 inflammasome in autophagy of HCC cells was assessed by E2-induced activation of the NLRP3 inflammasome, and we demonstrated that autophagy was inhibited by the NLRP3 inflammasome via the E2/ERβ/AMPK/mTOR pathway Last, the interaction of pyroptosis and autophagy was confirmed by flow cytometry methods We observed that E2-induced pyroptosis was dramatically increased by 3-methyladenine (3-MA) treatment, which was abolished by YVAD-cmk treatment, suggesting that caspase 1-dependent pyroptosis was negatively regulated by autophagy In conclusion, E2-induced activation of the NLRP3 inflammasome may serve as a suppressor in HCC progression, as it triggers pyroptotic cell death and inhibits protective autophagy

E2-Induced Activation of the NLRP3 Inflammasome Triggers Pyroptosis and Inhibits Autophagy in HCC Cells.

Pyroptosis is a form of caspase-1-dependent programmed cell death with anti-tumor properties, but the underlying molecular mechanisms are not fully understood. The results of our study showed that the antihyperlipidemic drug simvastatin induced pyroptosis in non-small cell lung cancer (NSCLC) cell lines and a xenograft mouse model. Inhibition of pyroptosis attenuated the effects of simvastatin on tumor cell viability and migration. These data suggest that simvastatin may induce pyroptosis, thereby potentially serving as a novel therapeutic agent for NSCLC.

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Simvastatin Suppresses Proliferation and Migration in Non-small Cell Lung Cancer via Pyroptosis.

Background/aims Lung cancer is one of the leading causes for cancer mortality. The poor therapeutic outcome of non-small cell lung carcinoma (NSCLC) is mainly due to late diagnosis and chemoresistance. In this study, we investigated the role of Musashi1 (MSI1) in NSCLC malignancy and chemoresistance. Methods Colony formation, MTT, glucose uptake and lactate production assays were employed to study lung cancer cell malignancy and chemoresistance. RT-PCR and Western blotting were performed to detect mRNA and protein expressions of genes. We used immunohistochemistry and Pearson correlation analysis to study the relationship of gene expression. Results We demonstrated that MSI1 was able to promote the proliferation and glucose metabolism of NSCLC cells, and to mediate the sensitivity to chemotherapy drugs in NSCLC cells. Importantly, we found that MSI1 could regulate the activity of Akt signaling. The regulation of NSCLC proliferation, glucose metabolism and chemoresistance by MSI1 was dependent on the modulation of the activity of the Akt signaling pathway. We also found that MSI1 was a target of miR-181a-5p, a microRNA involved in the regulation of cancer development. The expression levels of MSI1 and miR-181a-5p were negatively correlated in NSCLC. Conclusion MSI1 promotes non-small cell lung carcinoma malignancy and chemoresistance via activating the Akt signaling pathway, which provides a new strategy for the therapy of NSCLC.

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Musashi1 Promotes Non-Small Cell Lung Carcinoma Malignancy and Chemoresistance via Activating the Akt Signaling Pathway.

Background/aims Assistance with tumor-associated vascularization is needed for the growth and invasion of non-small cell lung cancer (NSCLC). Recently, it was shown that placental growth factor (PLGF) expressed by NSCLC cells had a critical role in promoting the metastasis of NSCLC cells. However, the underlying molecular mechanisms remain elusive. Methods Here, we first established a NSCLC model in mice that allows us not only to isolate tumor cells from non-tumor cells in the tumor, but also to trace tumor cells in living animals. Levels of PLGF, its unique receptor Flt-1, as well as transforming growth factor β1 (TGFβ1) was examined in tumor cells and tumor-associated macrophages (TAM) by RT-qPCR. A transwell well co-culture system and HUVEC assay were applied to study the crosstalk between NSCLC cells and TAM. Results NSCLC cells produced and secreted PLGF to signal to tumor-associated macrophages (TAM) through surface expression of Flt-1 on macrophages. In a transwell co-culture system, PLGF secreted by NSCLC cells triggered macrophage polarization to a TAM subtype that promote growth of NSCLC cells. Moreover, polarized TAM seemed to secrete TGFβ1 to enhance the growth of endothelial cells in a HUVEC assay. Conclusion The cross-talk between TAM and NSCLC cells via PLGF/Flt-1 and TGFβ receptor signaling may promote the growth and vascularization of NSCLC.

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Placental Growth Factor Mediates Crosstalk Between Lung Cancer Cells and Tumor-Associated Macrophages in Controlling Cancer Vascularization and Growth.

This study aimed to investigate the potential pathogenesis of early non-small cell lung cancer (NSCLC), including lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSC), by constructing a global transcriptional regulatory landscape to identify hub genes and key pathways. A total of 1,206 differentially expressed genes (DEGs) in early NSCLC were identified compared to normal lung tissue samples in GSE33532 and GSE29013. DEGs-related protein-protein interaction networks (PPIs) were constructed based on the STRING database and were then modularly analyzed using the ClusterOne tool. The enrichment analysis revealed that multiple modules were significantly involved in pathways such as the TNF signaling pathway, PPAR signaling pathway and PI3K/AKt signaling pathway. Ten genes were identified as hub genes in the PPIs and also found up-regulated at protein level. The prognostic value of the hub genes and the ten hub gene set variation score varied according to the different pathological types of NSCLC, which suggested the ten hub gene expression patterns can reflect the heterogeneity of two types of NSCLC. In conclusion, by carrying out a series of in-depth analyses, hub genes and key pathways associated with early NSCLC were identified by a global transcriptional regulatory landscape.

https://paperchase-aging.s3-us-west-1.amazonaws.com/pdf/5f3fc19cee918f00072c1816.pdf

Constructing a global transcriptional regulatory landscape for early non-small cell lung cancer to identify hub genes and key pathways

Lung cancer (LC) is one of the malignant tumors with growing morbidity and mortality. The involvement of runt-related transcription factor 1 (RUNX1) in LC patients has been elucidated. We intended to research mechanisms of RUNX1 and tartrate-resistant acid phosphatase 5 (ACP5) in LC. Firstly, ACP5 levels in LC tissues, paracancerous tissues, LC cells and tracheal epithelial cells were detected. RUNX1 overexpression plasmid and interference plasmid were constructed and transfected into 95C cells and A549 cells, respectively. The binding of RUNX1 to ACP5 promoter was tested. Additionally, the gain- and loss-of-function were performed to explore the effects of ACP5 and RUNX1 on LC biological process. The xenograft tumor in nude mice was constructed in vivo to verify in vitro results. Functional rescue experiment was performed by adding MAPK-specific activator P79350 to A549 cells with si-ACP5 to measure the effects of ERK/MAPK axis on LC progression. Consequently, we found ACP5 expression was higher in LC tissues and cells, and ACP5 silencing suppressed LC cell growth. Overexpression of ACP5 promoted malignant biological behavior of LC cells. RUNX1 could bind to ACP5 promoter, and overexpressed RUNX1 promoted ACP5 expression and LC cell growth. Moreover, ACP5 upregulated the ERK/MAPK axis and thus promoted LC progression. The results of xenograft tumor in nude mice showed that silencing ACP5 could inhibit the growth of LC cells in vivo. To conclude, silenced RUNX1 inhibits LC progression through the ERK/MAPK axis by binding to ACP5. This study may provide new approaches for LC treatment.

Kaibin Zhu

Papers

Simvastatin Suppresses Proliferation and Migration in Non-small Cell Lung Cancer via Pyroptosis.

Musashi1 Promotes Non-Small Cell Lung Carcinoma Malignancy and Chemoresistance via Activating the Akt Signaling Pathway.

Placental Growth Factor Mediates Crosstalk Between Lung Cancer Cells and Tumor-Associated Macrophages in Controlling Cancer Vascularization and Growth.

Constructing a global transcriptional regulatory landscape for early non-small cell lung cancer to identify hub genes and key pathways

Runt-related transcription factor 1 contributes to lung cancer development by binding to tartrate-resistant acid phosphatase 5.