LACTB mRNA expression is increased in pancreatic adenocarcinoma and high expression indicates a poor prognosis

The Pivotal Role of LACTB in the Process of Cancer Development

The mitochondrial serine β-lactamase-like protein LACTB has emerged as a critical regulator in cancer biology, distinguished by its unique structural and functional attributes. Defined by its conserved penicillin-binding proteins and β-lactamases (PBP-βLs) domain and SXXK catalytic motif, LACTB demonstrates properties distinct from its prokaryotic homologs, including the ability to polymerize into filaments. These structural characteristics enable LACTB to modulate mitochondrial organization and enzymatic activity, influencing lipid metabolism and indirectly affecting cellular proliferation. Importantly, the expression and functional roles of LACTB exhibit cancer-type-specific variation, underscoring its dual function as both a tumor suppressor and an oncogene. Decreased LACTB expression is associated with poor clinical outcomes in cancers such as breast cancer, lung cancer, and colorectal cancer, while specific mutations and regulatory mechanisms have been linked to its oncogenic activity in osteosarcoma and pancreatic adenocarcinoma. Mechanistically, LACTB regulates key processes in cancer progression, including mitochondrial dynamics, epithelial-mesenchymal transition (EMT), and cell death pathways. This duality highlights LACTB as a promising therapeutic target and underscores its relevance in advancing precision oncology strategies. This review provides a comprehensive analysis of expression level, structure-function relationships, and the diverse roles of LACTB in oncogenesis, underscoring its promise as a focal point for precision cancer therapies.

ZP3 Expression in Pancreatic Adenocarcinoma: Its Implications for the Prognosis and Therapy

BACKGROUND

The role of Zona pellucida glycoprotein 3 (ZP3) is unclear in pancreatic adenocarcinoma (PAAD).

OBJECTIVE

This study aimed to explore the role of ZP3 in PAAD.

METHODS

A comparative analysis of ZP3 gene expression was performed to discern differences between various types of cancer and PAAD, leveraging data sourced from The Cancer Genome Atlas (TCGA). This study aimed to assess the role of ZP3 as a potential diagnostic marker for PAAD. The relationship between ZP3 levels and clinical characteristics, as well as patient outcomes, was scrutinized. Additionally, genomic enrichment analysis was carried out to uncover the underlying regulatory mechanisms associated with ZP3. The study further delved into the association of ZP3 with immune system interactions, checkpoint gene expression, Tumor Mutational Burden (TMB), microsatellite instability (MSI), and tumor stemness index (mRNAsi). The aberrant expression patterns of ZP3 in PAAD cell cultures were confirmed through the application of quantitative reverse transcription PCR (qRT-PCR) techniques.

RESULTS

ZP3 exhibited aberrant expression in both pan-cancer and PAAD. A significant correlation was observed between increased levels of ZP3 expression in PAAD patients and histologic grade (p = 0.026). Elevated ZP3 expression in PAAD was found to be significantly associated with poorer overall survival (p = 0.003), progression-free survival (p = 0.012), and disease-specific survival (p = 0.002). In PAAD, the level of ZP3 gene expression was statistically significant (p < 0.001) and recognized as a key determinant of patient prognosis. ZP3 exhibited associations with various biological pathways, including primary immunodeficiency, oxidative phosphorylation, and other pathways. ZP3 expression demonstrated correlations with immune infiltration, immune checkpoint genes, TMB, MSI, and mRNAsi in PAAD. Moreover, a pronounced negative correlation was detected between ZP3 expression levels and the therapeutic effectiveness of various medications, including selumetinib, bleomycin, FH535, docetaxel, and tanespimycin, within the context of PAAD. Elevated levels of ZP3 were consistently observed in cell line models of PAAD.

CONCLUSION

ZP3 has the potential to serve as a prognostic biomarker and therapeutic target for patients with PAAD.

SNPs Give LACTB Oncogene-Like Functions and Prompt Tumor Progression via Dual-Regulating p53

LACTB is identified as a tumor suppressor in several tumors. However, preliminary study reveals that LACTB is overexpressed in osteosarcoma and indicates poor prognosis. Two missense mutations (rs34317102 and rs2729835) exist simultaneously in 92.31% of osteosarcoma patients and cause M5L and R469K double mutations in LACTB, suggesting the biologic function of LACTB protein may be altered in osteosarcoma. Moreover, LACTBM5L+R469K overexpression can promote malignant progression in different tumors, which suggests that the M5L and R469K mutations confer oncogene-like functions to LACTB. Mechanistically, LACTBM5L+R469K not only reduces the wild type p53 via enhancing PSMB7 catalytic activity, but also protects p53R156P protein from lysosomal degradation, which suggesting LACTBM5L+R469K is a dual-regulator for wt-p53 and mutant p53, and derive oncogene-like functions. More importantly, clavulanate potassium, a bacterial β-lactamase inhibitor, can inhibit osteosarcoma proliferation and sensitize osteosarcoma to cisplatin by binding and blocking LACTBM5L+R469K. These findings revealed that the M5L and R469K double mutations can diminish the tumor suppressive ability of wild type LACTB and provide oncogene-like functions to LACTB. Inhibiting LACTBM5L+R469K can suppress the progression of osteosarcoma harbouring wild-type or mutant p53. Clavulanate potassium is a promising drug by targeting LACTBM5L+R469K-p53 pathway for the treatment of osteosarcoma patients.

Mitochondrial proteases modulate mitochondrial stress signalling and cellular homeostasis in health and disease

Maintenance of mitochondrial homeostasis requires a plethora of coordinated quality control and adaptations' mechanisms in which mitochondrial proteases play a key role. Their activation or loss of function reverberate beyond local mitochondrial biochemical and metabolic remodelling into coordinated cellular pathways and stress responses that feedback onto the mitochondrial functionality and adaptability. Mitochondrial proteolysis modulates molecular and organellar quality control, metabolic adaptations, lipid homeostasis and regulates transcriptional stress responses. Defective mitochondrial proteolysis results in disease conditions most notably, mitochondrial diseases, neurodegeneration and cancer. Here, it will be discussed how mitochondrial proteases and mitochondria stress signalling impact cellular homeostasis and determine the cellular decision to survive or die, how these processes may impact disease etiopathology, and how modulation of proteolysis may offer novel therapeutic strategies.

LACTB suppresses liver cancer progression through regulation of ferroptosis

Ferroptosis, driven by iron-dependent phospholipid peroxidation, is emerging as an intrinsic cancer defense mechanism. However, the regulatory networks involved in ferroptosis remain largely unknown. Here, we found that serine beta-lactamase-like protein (LACTB) inhibits liver cancer progression by regulating ferroptosis. LACTB is downregulated in liver cancer, and the ectopic expression of LACTB markedly inhibits cell viability, colony formation, and tumour growth. LACTB knockout exerts the opposite effects. Further investigation revealed that LACTB blocks HSPA8 transcription in a p53-dependent manner, resulting in the elevation of NCOA4-mediated ferritinophagy and inhibition of SLC7A11/GSH/GPX4 signalling, thereby triggering ferroptosis and suppressing liver cancer progression. Liver cancer cells with an endogenous mutation of p53 binding site in the HSPA8 promoter exhibited increased resistance to ferroptosis inducers, and the ferroptosis-promoting effect of LACTB was significantly weakened in these mutant cells. Importantly, LACTB is identified as a downstream target of lenvatinib, and adeno-associated virus-mediated overexpression and knockdown of LACTB notably enhance and attenuate the anti-tumour efficacy of lenvatinib in vivo, respectively. Taken together, our study reveals a novel action of LACTB and provides potential therapeutic strategies for enhancing the efficacy of lenvatinib in liver cancer.

Systematic analysis of expression and prognostic significance for MCM family in head and neck squamous cell carcinoma

BACKGROUND

Head and neck squamous cell carcinoma (HNSC) is a common malignant tumor in the world and has a poor prognosis. The family of minichromosome maintenance proteins (MCM) improves the stability of genome replication by inhibiting the rate of DNA replication in eukaryotic cells, thus, small changes in physiological MCM levels would increase the instability of gene replication and increase the incidence of tumor formation, most of which are significantly elevated in multiple cancers. However, the expression of different MCM families in HNSC and their prognostic value remain unclear.

METHODS

ONCOMINE and GEPIA databases were used to analyze the expression of MCMs in HNSC. The Kaplan-Meier plotter database was used to identify molecules with prognostic values. We collected 77 HNSC tissues and 50 normal tissues to validate the results of the bioinformatics analysis by immunohistochemical staining.

RESULTS

The expression of MCM3, MCM5 and MCM6 in mRNA and protein levels were higher in HNSC. Moreover, the increased expression of MCM3, MCM5 and MCM6 in mRNA and protein levels predicted better prognosis of HNSC patients. Furthermore, multivariate analysis showed that high expressions of MCM3, MCM5 and MCM6 in protein level may be independent prognostic factors for HNSC patients.

CONCLUSION

The results of this study indicated that MCM3, MCM5 and MCM6 play an important role in occurrence and development in HNSC and might be risk factors for the survival of HNSC patients.

Prognostic and predictive value of super-enhancer-derived signatures for survival and lung metastasis in osteosarcoma

BACKGROUND

Risk stratification and personalized care are crucial in managing osteosarcoma due to its complexity and heterogeneity. However, current prognostic prediction using clinical variables has limited accuracy. Thus, this study aimed to explore potential molecular biomarkers to improve prognostic assessment.

METHODS

High-throughput inhibitor screening of 150 compounds with broad targeting properties was performed and indicated a direction towards super-enhancers (SEs). Bulk RNA-seq, scRNA-seq, and immunohistochemistry (IHC) were used to investigate SE-associated gene expression profiles in osteosarcoma cells and patient tissue specimens. Data of 212 osteosarcoma patients who received standard treatment were collected and randomized into training and validation groups for retrospective analysis. Prognostic signatures and nomograms for overall survival (OS) and lung metastasis-free survival (LMFS) were developed using Cox regression analyses. The discriminatory power, calibration, and clinical value of nomograms were evaluated.

RESULTS

High-throughput inhibitor screening showed that SEs significantly contribute to the oncogenic transcriptional output in osteosarcoma. Based on this finding, focus was given to 10 SE-associated genes with distinct characteristics and potential oncogenic function. With multi-omics approaches, the hyperexpression of these genes was observed in tumor cell subclusters of patient specimens, which were consistently correlated with poor outcomes and rapid metastasis, and the majority of these identified SE-associated genes were confirmed as independent risk factors for poor outcomes. Two molecular signatures were then developed to predict survival and occurrence of lung metastasis: the SE-derived OS-signature (comprising LACTB, CEP55, SRSF3, TCF7L2, and FOXP1) and the SE-derived LMFS-signature (comprising SRSF3, TCF7L2, FOXP1, and APOLD1). Both signatures significantly improved prognostic accuracy beyond conventional clinical factors.

CONCLUSIONS

Oncogenic transcription driven by SEs exhibit strong associations with osteosarcoma outcomes. The SE-derived signatures developed in this study hold promise as prognostic biomarkers for predicting OS and LMFS in patients undergoing standard treatments. Integrative prognostic models that combine conventional clinical factors with these SE-derived signatures demonstrate substantially improved accuracy, and have the potential to facilitate patient counseling and individualized management.

A potential therapeutic approach for gastric cancer: inhibition of LACTB transcript 1

BACKGROUND

This study sought to investigate the role of LACTB transcript 1 in regulating adaptive immune resistance and stemness in gastric cancer and its potential as a therapeutic target for precision medicine.

METHODS

Bioinformatics analysis and RT-qPCR were used to analyze the expression level of LACTB and its transcripts in gastric cancer cells. The effects of LACTB transcript 1 on adaptive immune resistance and stemness were evaluated using in vitro cell experiments and western blotting experiments.

RESULTS

Our study findings revealed that LACTB transcript 1 modulated adaptive immune resistance and inhibited the stemness of gastric cancer cells. Knocking down the expression level of LACTB transcript 1 activated autophagy and inhibited EMT. As expected, overexpression of LACTB transcript 1 yielded the opposite findings. The expression level of LACTB transcript 1 in the peripheral blood of gastric cancer patients was consistent with the bioinformatics analysis, suggesting its potential as a biomarker of gastric cancer.

CONCLUSIONS

LACTB transcript 1 is a promising therapeutic target for precision medicine in gastric cancer by modulating immune evasion mechanisms and stemness. These findings provide insights into leveraging long non-coding RNAs (lncRNAs) in immunotherapy, radiotherapy, and chemotherapy to enhance cancer therapy efficacy, particularly in the context of targeting tumor heterogeneity and stemness.

Mitochondria-Related Transcriptome Characterization Associated with the Immune Microenvironment, Therapeutic Response and Survival Prediction in Pancreatic Cancer

(1) Background: Pancreatic cancer (PC) is one of the most lethal tumors. Mitochondrial dysfunction has been reported to be involved in cancer development; however, its role in PC has remained unclear. (2) Methods: The differentially expressed NMGs were selected between PC and normal pancreatic tissue. The NMG-related prognostic signature was established by LASSO regression. A nomogram was developed based on the 12-gene signature combined with other significant pathological features. An extensive analysis of the 12 critical NMGs was performed in multiple dimensions. The expression of some key genes was verified in our external cohort. (3) Results: Mitochondria-related transcriptome features was obviously altered in PC compared with normal pancreas tissue. The 12-NMG signature showed good performance in predicting prognosis in various cohorts. The high- and low-risk groups exhibited notable diversity in gene mutation characteristics, biological characteristics, chemotherapy response, and the tumor immune microenvironment. Critical gene expression was demonstrated in our cohort at the mRNA and protein levels and in organelle localization. (4) Conclusions: Our study analyzed the mitochondrial molecular characterization of PC, proving the crucial role of NMGs in PC development. The established NMG signature helps classify patient subtypes in terms of prognosis prediction, treatment response, immunological features, and biological function, providing a potential therapeutic strategy targeting mitochondrial transcriptome characterization.

LACTB, a Metabolic Therapeutic Target in Clinical Cancer Application

Serine beta-lactamase-like protein (LACTB) is the only mammalian mitochondrial homolog evolved from penicillin-binding proteins and β-lactamases (PBP-βLs) in bacteria. LACTB, an active-site serine protease, polymerizes into stable filaments, which are localized to the intermembrane space (IMS) of mitochondrion and involved in the submitochondrial organization, modulating mitochondrial lipid metabolism. Cancer pathogenesis and progression are relevant to the alterations in mitochondrial metabolism. Metabolic reprogramming contributes to cancer cell behavior. This article (1) evidences the clinical implications of LACTB on neoplastic cell proliferation and migration and tumor growth and metastasis as well as LACTB’s involvement in chemotherapeutic and immunotherapeutic responses; (2) sketches the structural basis for LACTB activity and function; and (3) highlights the relevant regulatory mechanisms to LACTB. The abnormal expression of LACTB has been associated with clinicopathological features of cancer tissues and outcomes of anticancer therapies. With the current pioneer researches on the tumor-suppressed function, structural basis, and regulatory mechanism of LACTB, the perspective hints at a great appeal of enzymic property, polymerization, mutation, and epigenetic and post-translational modifications in investigating LACTB’s role in cancer pathogenesis. This perspective provides novel insights for LACTB as a metabolic regulator with potential to develop targeted cancer therapies or neoadjuvant therapeutic interventions.

Unveiling the Function of the Mitochondrial Filament-Forming Protein LACTB in Lipid Metabolism and Cancer

LACTB is a relatively unknown mitochondrial protein structurally related to the bacterial penicillin-binding and beta-lactamase superfamily of serine proteases. LACTB has recently gained an increased interest due to its potential role in lipid metabolism and tumorigenesis. To date, around ninety studies pertaining to LACTB have been published, but the exact biochemical and cell biological function of LACTB still remain elusive. In this review, we summarise the current knowledge about LACTB with particular attention to the implications of the recently published study on the cryo-electron microscopy structure of the filamentous form of LACTB. From this and other studies, several specific properties of LACTB emerge, suggesting that the protein has distinct functions in different physiological settings. Resolving these issues by further research may ultimately lead to a unified model of LACTB’s function in cell and organismal physiology. LACTB is the only member of its protein family in higher animals and LACTB may, therefore, be of particular interest for future drug targeting initiatives.

Structural basis for the catalytic activity of filamentous human serine beta-lactamase-like protein LACTB

Serine beta-lactamase-like protein (LACTB) is a mammalian mitochondrial serine protease that can specifically hydrolyze peptide bonds adjacent to aspartic acid residues and is structurally related to prokaryotic penicillin-binding proteins. Here, we determined the cryoelectron microscopy structures of human LACTB (hLACTB) filaments from wild-type protein, a middle region deletion mutant, and in complex with the inhibitor Z-AAD-CMK at 3.0-, 3.1-, and 2.8-Å resolution, respectively. Structural analysis and activity assays revealed that three interfaces are required for the assembly of hLACTB filaments and that the formation of higher order helical structures facilitates its cleavage activity. Further structural and enzymatic analyses of middle region deletion constructs indicated that, while this region is necessary for substrate hydrolysis, it is not required for filament formation. Moreover, the inhibitor-bound structure showed that hLACTB may cleave peptide bonds adjacent to aspartic acid residues. These findings provide the structural basis underlying hLACTB catalytic activity.

LACTB suppresses carcinogenesis in lung cancer and regulates the EMT pathway

Lung cancer causes thousands of deaths worldwide every year, and present therapeutics show little benefit for advanced-stage patients. Researchers do not know why and how lung cancer begins. Lactamase β (LACTB) is a tumor-suppressor in some cancers. However, its role in lung cancer is unknown. By analyzing the TCGA database and Kaplan-Meier Plotter database, LACTB was found to be downregulated in lung cancer tissues but the methylation level was increased. Patients with high LACTB expression exhibited improved survival. Then, in vitro assays demonstrated that LACTB overexpression inhibited cell migration and invasion, and induced apoptosis in H1299 and H1975 cells. Knockdown of LACTB caused the reverse effects. Moreover, a much higher apoptotic rate and more potent inhibitory effects on H1299 and H1975 cells were obtained when LACTB was combined with docetaxel. In addition, members of the epithelial-mesenchymal transition (EMT) signaling pathway were assessed using western blot analysis. The expression of E-cadherin was decreased while levels of N-cadherin and vimentin were increased after knockdown of LACTB in lung cancer cells. By contrast, overexpression of LACTB increased the level of E-cadherin but decreased N-cadherin and vimentin. Therefore, LACTB is a tumor suppressor in lung cancer that inhibits cell migration and invasion and induces cell apoptosis. Meanwhile, LACTB was found to strengthen the anticancer role of docetaxel and to suppress the EMT pathway in lung cancer.

Mitochondrial Tumor Suppressors-The Energetic Enemies of Tumor Progression

Tumor suppressors represent a critical line of defense against tumorigenesis. Their mechanisms of action and the pathways they are involved in provide important insights into cancer progression, vulnerabilities, and treatment options. Although nuclear and cytosolic tumor suppressors have been extensively investigated, relatively little is known about tumor suppressors localized within the mitochondria. However, recent research has begun to uncover the roles of these important proteins in suppressing tumorigenesis. Here, we review this newly developing field and summarize available information on mitochondrial tumor suppressors.