Chromodomain-helicase-DNA binding protein 5, 7 and pronecrotic mixed lineage kinase domain-like protein serve as potential prognostic biomarkers in patients with resected pancreatic adenocarcinomas

Characterizing the prognostic and therapeutic value of necroptosis in sarcoma based on necroptosis subtypes

Necroptosis, a type of necrotic cell death independent of caspase regulation, is mainly mediated by receptor interacting serine/threonine kinase 1 (RIPK1), receptor interacting serine/threonine kinase 3 (RIPK3) and mixed lineage kinase domain-like (MLKL). Necroptosis plays an essential role in many tumors. However, the potential roles of necroptosis in tumor microenvironment (TME) of sarcoma (SARC) remain unknown. This study analyzed the expression, prognosis, genetic alterations of necroptosis genes in SARC. We identified two subtypes (cluster A and B) by performing unsupervised consensus clustering. Cluster A and B greatly differed in prognosis and immune infiltration, with cluster A showing more favorable prognosis, higher immune infiltration and higher expression levels of necroptosis genes than cluster B. Based on the differentially expressed genes (DEGs) between two clusters, a necroptosis scoring system was developed for predicting overall survival of SARC patients. Patients with high necroptosis score had worse survival status, with a decreased infiltration level of most immune cells. Our findings demonstrated the potential role of necroptosis in regulating tumor microenvironment and the prognostic value of necroptosis-related genes for SARC patients.

Pan-cancer analysis of a novel indicator of necroptosis with its application in human cancer

As a type of programmed cell death, necroptosis is thought to play a dual role in tumorigenesis. However, a comprehensive assessment of necroptosis-related regulators across human cancers has not been reported. Therefore, in this study, we established a quantitative index to evaluate the necroptosis rate and determine its correlations with clinical prognosis, signaling pathways and molecular features, immune cell infiltration and regulation, immunotherapy, and chemotherapy sensitivity across cancers. Our results indicated that the necroptosis score can act as a favorable or risky prognostic factor in various cancer types. A gene set variation analysis suggested that necroptosis is significantly associated with immune- and inflammation-related signaling pathways, cell growth and apoptosis, and energy metabolism. Furthermore, necroptosis can affect the tumor microenvironment and immunity regulation, and the effect of necroptosis on immunity is different in different tumor types. There is crosstalk between components of necroptosis, pyroptosis, ferroptosis and autophagy pathways in multiple types of cancers. Finally, the necroptosis rate can be an indicator of immunotherapy effectiveness in multiple cancers and can affect the chemotherapy sensitivity of cancer cells. Our study presents a characterization of necroptosis across human cancers, highlights the potential necroptotic effects on immune regulation, and provides new insights into the development of individualized tumor treatments and clinical applications of immunotherapy.

Regulated cell death (RCD) in cancer: key pathways and targeted therapies

Regulated cell death (RCD), also well-known as programmed cell death (PCD), refers to the form of cell death that can be regulated by a variety of biomacromolecules, which is distinctive from accidental cell death (ACD). Accumulating evidence has revealed that RCD subroutines are the key features of tumorigenesis, which may ultimately lead to the establishment of different potential therapeutic strategies. Hitherto, targeting the subroutines of RCD with pharmacological small-molecule compounds has been emerging as a promising therapeutic avenue, which has rapidly progressed in many types of human cancers. Thus, in this review, we focus on summarizing not only the key apoptotic and autophagy-dependent cell death signaling pathways, but the crucial pathways of other RCD subroutines, including necroptosis, pyroptosis, ferroptosis, parthanatos, entosis, NETosis and lysosome-dependent cell death (LCD) in cancer. Moreover, we further discuss the current situation of several small-molecule compounds targeting the different RCD subroutines to improve cancer treatment, such as single-target, dual or multiple-target small-molecule compounds, drug combinations, and some new emerging therapeutic strategies that would together shed new light on future directions to attack cancer cell vulnerabilities with small-molecule drugs targeting RCD for therapeutic purposes.

MLKL deficiency in BrafV600EPten−/− melanoma model results in a modest delay of nevi development and reduced lymph node dissemination in male mice

Cancers acquire several capabilities to survive the multistep process in carcinogenesis. Resisting cell death is one of them. Silencing of the necroptosis initiator Ripk3 occurs in a wide variety of cancer types including melanoma. Little is known about the role of the necroptosis executioner MLKL in tumor development. Studies often indicate opposing roles for MLKL as a tumor-suppressing or a tumor-promoting protein. This study investigates the role of MLKL during melanoma initiation and progression using a tamoxifen-inducible melanoma mouse model driven by melanocyte-specific overexpression of mutated Braf and simultaneous deletion of Pten (Braf^V600EPten^−/−). In this model we observed a clear sex difference: melanoma initiation and progression were faster in females mice. Mlkl deficiency in male mice resulted in a modest but significant reduction of nevi growth rate compared to the littermate control. In these mice, infiltration and expansion of melanoma cells in the inguinal lymph node were also modestly decreased. This is likely to be a consequence of the delay in nevi development. No significant difference was observed in the Mlkl-deficient condition in female mice in which melanoma development was faster. Overall, our results indicate that in this genetic model MLKL has a minor role during melanoma initiation and progression.

MLKL in cancer: more than a necroptosis regulator

Mixed lineage kinase domain-like protein (MLKL) emerged as executioner of necroptosis, a RIPK3-dependent form of regulated necrosis. Cell death evasion is one of the hallmarks of cancer. Besides apoptosis, some cancers suppress necroptosis-associated mechanisms by for example epigenetic silencing of RIPK3 expression. Conversely, necroptosis-elicited inflammation by cancer cells can fuel tumor growth. Recently, necroptosis-independent functions of MLKL were unraveled in receptor internalization, ligand-receptor degradation, endosomal trafficking, extracellular vesicle formation, autophagy, nuclear functions, axon repair, neutrophil extracellular trap (NET) formation, and inflammasome regulation. Little is known about the precise role of MLKL in cancer and whether some of these functions are involved in cancer development and metastasis. Here, we discuss current knowledge and controversies on MLKL, its structure, necroptosis-independent functions, expression, mutations, and its potential role as a pro- or anti-cancerous factor. Analysis of MLKL expression patterns reveals that MLKL is upregulated by type I/II interferon, conditions of inflammation, and tissue injury. Overall, MLKL may affect cancer development and metastasis through necroptosis-dependent and -independent functions.

Bacterial DNA induces the formation of heat-resistant disease-associated proteins in human plasma

Our study demonstrated for the first time that bacterial extracellular DNA (eDNA) can change the thermal behavior of specific human plasma proteins, leading to an elevation of the heat-resistant protein fraction, as well as to de novo acquisition of heat-resistance. In fact, the majority of these proteins were not known to be heat-resistant nor do they possess any prion-like domain. Proteins found to become heat-resistant following DNA exposure were named "Tetz-proteins". Interestingly, plasma proteins that become heat-resistant following treatment with bacterial eDNA are known to be associated with cancer. In pancreatic cancer, the proportion of proteins exhibiting eDNA-induced changes in thermal behavior was found to be particularly elevated. Therefore, we analyzed the heat-resistant proteome in the plasma of healthy subjects and in patients with pancreatic cancer and found that exposure to bacterial eDNA made the proteome of healthy subjects more similar to that of cancer patients. These findings open a discussion on the possible novel role of eDNA in disease development following its interaction with specific proteins, including those involved in multifactorial diseases such as cancer.

Interleukin-1 receptor activation aggravates autosomal dominant polycystic kidney disease by modulating regulated necrosis

Autosomal dominant polycystic kidney disease (ADPKD) is associated with increased chemokines, cytokines, and growth factors in the diseased kidney. We found that both isoforms of IL-1, IL-1α and IL-1β, were upregulated in ADPKD tissues. Here, we used a unique murine ADPKD model with selective deletion of polycystin-1 (pkd1) in the kidney (KPKD1) to study the role of IL-1 signaling in ADPKD progression. In KPKD mice, genetic deletion of the IL-1 receptor [IL-1 receptor (IL-1R) knockout (KO)] prolongs survival and attenuates cyst volume. Compared with IL-1R wild-type KPKD1 kidneys, IL-1R KO KPKD1 kidneys have upregulated TNF-α gene expression, with consequent elevations in markers for TNF-dependent regulated necrosis. We further observed that regulated necrosis was increased in ADPKD tissues from both humans and mice. To confirm that enhanced necroptosis is protective in ADPKD, we treated KPKD1 mice with an inhibitor of regulated necrosis (Nec-1). Regulated necrosis suppression augments kidney weights, suggesting that regulated necrosis is required to limit kidney growth in ADPKD. Thus, IL-1R activation drives ADPKD progression by paradoxically limiting regulated necrosis.

Progress in studies of necroptosis and its relationship to disease processes

This review briefly introduces the mechanism and detection methods of necroptosis in recent years. The most significant points of this review focus on the involvement of necroptotic proteins in disease progression. The following aspects are summarized: 1) RIPs, MLKL, and the upstream and downstream molecules that mediate necroptosis; 2) The development of detection methods for necroptosis; 3) The involvement of related necroptotic proteins in diverse diseases etiology; and 4) The application of necroptotic proteins in disease diagnosis.

Decreased expression of chromodomain helicase DNA-binding protein 9 is a novel independent prognostic biomarker for colorectal cancer

Previous studies suggested that chromodomain helicase DNA-binding proteins (CHDs), including CHD 1-8, were associated with several human diseases and cancers including lymphoma, liver cancer, colorectal cancer, stomach cancer, etc. To date, little research on CHD 9 in human cancers has been reported. In this study, we assessed the prognostic value of CHD 9 in patients with colorectal cancer (CRC). We screened for CHD 9 expression using immunohistochemical analysis in 87 surgical CRC specimens and found that the expression was upregulated in 81.5% of the cases, while 7.4% were decreased; in the remaining 11.1% of the cases, levels were not altered. Kaplan-Meier analysis showed that patients with high CHD 9 expression had better prognosis than those with low CHD 9 expression (54.5 vs 32.1%, P=0.034). Subsequently, Cox multi-factor survival regression analysis revealed that expression of CHD 9 protein was an independent predictor for CRC, with a hazard ratio of 0.503 (P=0.028). In addition, we found that CHD 9 expression was positively correlated with MSH2 (rs=0.232, P=0.036). We speculated that CHD9 might be a putative tumor suppressor gene, and could inhibit the development of CRC by participating in DNA repair processes. Our findings suggest that CHD 9 could be a novel prognostic biomarker and a therapeutic target for CRC. Further studies are needed to detect the effect of CHD 9 on cellular function and the expression of mismatch repair genes.

High CHD9 expression is associated with poor prognosis in clear cell renal cell carcinoma

Clear cell renal cell carcinoma (ccRCC) is the most common subtype of renal cell carcinoma. The chromo-helicase-DNA binding proteins (CHDs), containing nine members named CHD1-9, act as regulators of the chromatin remodeling process and gene expression. To determine the correlation between CHD9 expression and ccRCC, we performed an immunohistochemical staining in a tissue microarray (TMAs) containing tissue samples from 88 ccRCC patients. The results showed that cytoplasm CHD9 expression was statistically decreased in tumor tissues compared to adjacent tissues (8.54±2.90 vs 12.61±2.05, P=0.000), while nuclear CHD9 expression was upregulated in the tumor tissues (1.47±2.93 vs 0.29±1.24, P=0.000). A univariate analysis found that cytoplasm CHD9 expression in cancer tissues was correlated with the patients' pathological grading (P=0.002, r=0.330), the clinical stages (P=0.02, r=0.250) and the T grading (P=0.024, r=0.241) significantly. In addition, cytoplasm CHD9 expression in non-tumor tissues was correlated with the ccRCC patients' pathological grading (P=0.031, r=-0.231) significantly. Patients with high cytoplasm CHD9 expression had a significantly worse prognosis than those with low cytoplasm CHD9 expression levels (59.7% vs 85.7%, P=0. 042). In conclusion, our study indicated the important role of CHD9 in ccRCC and suggested CHD9 may be a potential biomarker for prognostic prediction and a new target for therapy.