HtrA4 Protease Promotes Chemotherapeutic-Dependent Cancer Cell Death

A Comprehensive Analysis of the Effect of A>I(G) RNA-Editing Sites on Genotoxic Drug Response and Progression in Breast Cancer

Dysregulated A>I(G) RNA editing, which is mainly catalyzed by ADAR1 and is a type of post-transcriptional modification, has been linked to cancer. A low response to therapy in breast cancer (BC) is a significant contributor to mortality. However, it remains unclear if there is an association between A>I(G) RNA-edited sites and sensitivity to genotoxic drugs. To address this issue, we employed a stringent bioinformatics approach to identify differentially RNA-edited sites (DESs) associated with low or high sensitivity (FDR 0.1, log2 fold change 2.5) according to the IC50 of PARP inhibitors, anthracyclines, and alkylating agents using WGS/RNA-seq data in BC cell lines. We then validated these findings in patients with basal subtype BC. These DESs are mainly located in non-coding regions, but a lesser proportion in coding regions showed predicted deleterious consequences. Notably, some of these DESs are previously reported as oncogenic variants, and in genes related to DNA damage repair, drug metabolism, gene regulation, the cell cycle, and immune response. In patients with BC, we uncovered DESs predominantly in immune response genes, and a subset with a significant association (log-rank test p < 0.05) between RNA editing level in LSR, SMPDL3B, HTRA4, and LL22NC03-80A10.6 genes, and progression-free survival. Our findings provide a landscape of RNA-edited sites that may be involved in drug response mechanisms, highlighting the value of A>I(G) RNA editing in clinical outcomes for BC.

The NtDEGP5 gene improves drought tolerance in tobacco (Nicotiana tabacum L.) by dampening plastid extracellular Ca2+ and flagellin signaling and thereby reducing ROS production

Tobacco is an essential cash crop, but drought has become a major factor in the decline of global tobacco production as a result of changes in the global climate. The HtrA protease is an oligomeric serine endopeptidase that responds to stress in plants. DEGP5 is a member of the gene family that encodes HtrA protease, which promotes plant adaptation to adversity. The aim of this study was to investigate the role and mechanism employed by the DEGP5 gene in response to drought stress in tobacco. NtDEGP5-overexpression lines were obtained by genetic transformation and the phenotypes and transcriptomes of NtDEGP5-overexpression lines and wild-type (K326) tobacco seedlings were compared under drought stress. The results demonstrated that plants overexpressing NtDEGP5 exhibited greater drought tolerance. The differentially expressed genes involved in the regulation of drought tolerance by DEGP5 were enriched in metabolic pathways, such as plant-pathogen interaction and glutathione metabolism, with the plant-pathogen interaction pathway having the most differentially expressed genes. An analysis of the plant-pathogen interaction pathway revealed that these genes contributed to the suppression of plastid extracellular Ca2+ signaling and flagellin signaling to inhibit reactive oxygen species production, and that lower levels of reactive oxygen species act as a signal to regulate the activation of the antioxidant system, further balancing the production and removal of reactive oxygen species in tobacco seedlings under drought stress. These findings suggest that the NtDEGP5 gene can enhance the drought tolerance of tobacco by regulating the homeostasis of reactive oxygen species by inhibiting extracellular plastids.

Cellular Functions of High-Temperature Requirement Factor A4 in Placenta

The expression of High-temperature requirement factor A4 (HtrA4) mRNA is significantly lower in the chorionic villi of patients with recurrent pregnancy loss (RPL) than in the control group. We conducted an investigation into the cellular functions of HtrA4 using the CRISPR/Cas9 system and shRNA-HtrA4 to create knockout BeWo cells and HtrA4 knockdown JEG3 cells. Our results indicated that the knockout BeWo cells exhibited reduced capacity for invasion and fusion, but increased levels of proliferation and migration, with a significantly shortened cell cycle compared to wild-type cells. Wild-type BeWo cells highly expressed cell invasion- and fusion-related factors, while knockout BeWo cells highly expressed migration-, proliferation-, and cell cycle-related factors. The shRNA-HtrA4 JEG3 cells showed a decreased capacity for invasion, but an increased capacity for migration, accompanied by a decrease in the expression of cell invasion-related factors and an increase in migration-related factors. Moreover, our ELISA results revealed that the serum HtrA4 level was lower in patients with RPL than in the controls. These findings suggest that HtrA4 depletion may be associated with placental dysfunction.

A Receptor Tyrosine Kinase Inhibitor Sensitivity Prediction Model Identifies AXL Dependency in Leukemia

Despite incredible progress in cancer treatment, therapy resistance remains the leading limiting factor for long-term survival. During drug treatment, several genes are transcriptionally upregulated to mediate drug tolerance. Using highly variable genes and pharmacogenomic data for acute myeloid leukemia (AML), we developed a drug sensitivity prediction model for the receptor tyrosine kinase inhibitor sorafenib and achieved more than 80% prediction accuracy. Furthermore, by using Shapley additive explanations for determining leading features, we identified AXL as an important feature for drug resistance. Drug-resistant patient samples displayed enrichment of protein kinase C (PKC) signaling, which was also identified in sorafenib-treated FLT3-ITD-dependent AML cell lines by a peptide-based kinase profiling assay. Finally, we show that pharmacological inhibition of tyrosine kinase activity enhances AXL expression, phosphorylation of the PKC-substrate cyclic AMP response element binding (CREB) protein, and displays synergy with AXL and PKC inhibitors. Collectively, our data suggest an involvement of AXL in tyrosine kinase inhibitor resistance and link PKC activation as a possible signaling mediator.

Allosteric inhibition of HTRA1 activity by a conformational lock mechanism to treat age-related macular degeneration

The trimeric serine protease HTRA1 is a genetic risk factor associated with geographic atrophy (GA), a currently untreatable form of age-related macular degeneration. Here, we describe the allosteric inhibition mechanism of HTRA1 by a clinical Fab fragment, currently being evaluated for GA treatment. Using cryo-EM, X-ray crystallography and biochemical assays we identify the exposed LoopA of HTRA1 as the sole Fab epitope, which is approximately 30 Å away from the active site. The cryo-EM structure of the HTRA1:Fab complex in combination with molecular dynamics simulations revealed that Fab binding to LoopA locks HTRA1 in a non-competent conformational state, incapable of supporting catalysis. Moreover, grafting the HTRA1-LoopA epitope onto HTRA2 and HTRA3 transferred the allosteric inhibition mechanism. This suggests a conserved conformational lock mechanism across the HTRA family and a critical role of LoopA for catalysis, which was supported by the reduced activity of HTRA1-3 upon LoopA deletion or perturbation. This study reveals the long-range inhibition mechanism of the clinical Fab and identifies an essential function of the exposed LoopA for activity of HTRA family proteases.

PSMC2 knockdown inhibits the progression of oral squamous cell carcinoma by promoting apoptosis via PI3K/Akt pathway

Proteasome 26S subunit, ATPase 2 (PSMC2) is a recently identified gene which is potentially associated with human carcinogenesis. However, the effects of PSMC2 on oral squamous cell carcinoma (OSCC) is still unclear. Here, we investigated PSMC2 expression in OSCC tissues and explored its effects on the biological behaviors of OSCC cells. PSMC2 expression was evaluated by immunohistochemistry in a tissue microarray containing 60 OSCC tissues and 9 normal tissues. PSMC2 was knocked down through lentivirus infection in OSCC cell lines. MTT, colony formation, flow cytometry, transwell, and scratch assays were performed to detect effects of PSMC2 knockdown on phenotypes of OSCC cells. Human apoptosis antibody array was used to screen potential downstream of PSMC2 in OSCC. Finally, the effects of PSMC2 knockdown on tumor growth were assessed in a tumor xenograft model using BALB/c nude mice. PSMC2 expression was significantly upregulated in OSCC tissues compared with normal tissues and correlated with poor prognosis. PSMC2 knockdown significantly suppressed cell proliferation, migration, but promoted apoptosis of OSCC cells. Additionally, we confirmed that PSMC2 knockdown can increase the expression of pro-apoptotic proteins. Furthermore, we found that PSMC2 knockdown downregulated expression of p100, p-Akt, CDK6, and upregulated of MAPK9. Xenograft experiments revealed that PSMC2 knockdown can suppress OSCC tumor growth and promote apoptosis. This study demonstrated that PSMC2 plays a critical role in OSCC progression through affecting pro-apoptotic protein expression and apoptosis pathways. It indicated that targeting PSMC2 might be a promising strategy for OSCC treatment.

Comprehensive Analysis of Prognostic Microenvironment-Related Genes in Invasive Breast Cancer

Recent studies reveal that tumor microenvironment contributes to breast cancer (BRCA) development, progression, and therapeutic response. However, the contribution of the tumor microenvironment-related genes in routine diagnostic testing or therapeutic decision making for BRCA remains elusive. Immune/stromal/ESTIMATE scores calculated by the ESTIMATE algorithm quantify immune and stromal components in a tumor, and thus can reflect tumor microenvironment. To investigate the association of the tumor microenvironment-related genes with invasive BRCA prognosis, here we analyzed the immune/stromal/ESTIMATE scores in combination with The Cancer Genome Atlas (TCGA) database in invasive BRCA. We found that immune/stromal/ESTIMATE scores were significantly correlated with the invasive BRCA clinicopathological factors. Based on the immune/stromal/ESTIMATE scores, we extracted a series of differential expression genes (DEGs) related to the tumor microenvironment. Survival analysis was further performed to identify a list of high-frequency DEGs (HF-DEGs), which exhibited prognostic value in invasive BRCA. Importantly, consistent with the results of bioinformatics analysis, immunohistochemistry results showed that high SASH3 expression was associated with a good prognosis in invasive BRCA patients. Our findings suggest that the tumor microenvironment-related HF-DEGs identified in this study have prognostic values and may serve as potential biomarkers and therapeutic targets for invasive BRCA.

Overview of Human HtrA Family Proteases and Their Distinctive Physiological Roles and Unique Involvement in Diseases, Especially Cancer and Pregnancy Complications

The mammalian high temperature requirement A (HtrA) proteins are a family of evolutionarily conserved serine proteases, consisting of four homologs (HtrA1-4) that are involved in many cellular processes such as growth, unfolded protein stress response and programmed cell death. In humans, while HtrA1, 2 and 3 are widely expressed in multiple tissues with variable levels, HtrA4 expression is largely restricted to the placenta with the protein released into maternal circulation during pregnancy. This limited expression sets HtrA4 apart from the rest of the family. All four HtrAs are active proteases, and their specific cellular and physiological roles depend on tissue type. The dysregulation of HtrAs has been implicated in many human diseases such as cancer, arthritis, neurogenerative ailments and reproductive disorders. This review first discusses HtrAs broadly and then focuses on the current knowledge of key molecular characteristics of individual human HtrAs, their similarities and differences and their reported physiological functions. HtrAs in other species are also briefly mentioned in the context of understanding the human HtrAs. It then reviews the distinctive involvement of each HtrA in various human diseases, especially cancer and pregnancy complications. It is noteworthy that HtrA4 expression has not yet been reported in any primary tumour samples, suggesting an unlikely involvement of this HtrA in cancer. Collectively, we accentuate that a better understanding of tissue-specific regulation and distinctive physiological and pathological roles of each HtrA will improve our knowledge of many processes that are critical for human health.

KIF15 is involved in development and progression of Burkitt lymphoma

BACKGROUND

Burkitt lymphoma (BL) is a highly aggressive, fast-growing B-cell non-Hodgkin's lymphoma, manifested in several subtypes, including sporadic, endemic, and immunodeficiency-related forms, the mechanism of which is still not clear. Abundant evidence reported that KIF15 was involved in the progression of human cancer. The emphasis of this study is to explore the functions of KIF15 in the development of BL.

METHODS

Firstly, tumor and normal tissues were collected for detecting expression of KIF15 in BL. Lentivirus-mediated shRNA knockdown of KIF15 was used to construct BL cell model, which was verified by qRT-PCR and Western Blot. The cell proliferation was detected by CCK8 assay, cell apoptosis and cell cycle were measured through flow cytometry. Transwell assay was conducted to detect the migration.

RESULTS

We first found that KIF15 is highly expressed in BL. Knockdown of KIF15 can inhibit proliferation and migration, promote apoptosis and arrest the cell cycle. Moreover, KIF15 is involved in BL cell activity through regulating expression of apoptosis-related proteins (Caspase3, Caspase8, HTRA, IGFBP-6, p53, SMAC, sTNF-R1, TNF-β and Bcl-2) and downstream pathways, such as p-Akt, CCND1, CDK6 and PIK3CA.

CONCLUSIONS

These findings justify the search for small molecule inhibitors targeting KIF15 as a novel therapeutic strategy in BL.

HtrA serine proteases in cancers: A target of interest for cancer therapy

The HtrA protein family is composed by evolutionally-conserved serine proteases, which are homologous to the HtrA protein of the model bacterium Escherichia coli. They are widely distributed in organisms including humans, prokaryotes and eukaryotes. Moreover, HtrA family proteins are important regulators of a variety of human physiological processes, which contains the maintenance of mitochondrial homeostasis, cellular signal transduction and apoptosis regulation. The HtrA family has been found to be associated with cancer and could be used as a target for future cancer treatments. The purpose of this article is to review the relationship between these HtrA and cancer and to summarize the latest researches on HtrA and cancer.