The Deep Proteomics Approach Identified Extracellular Vesicular Proteins Correlated to Extracellular Matrix in Type One and Two Endometrial Cancer

Among gynecological cancers, endometrial cancer is the most common in developed countries. Extracellular vesicles (EVs) are cell-derived membrane-surrounded vesicles that contain proteins involved in immune response and apoptosis. A deep proteomic approach can help to identify dysregulated extracellular matrix (ECM) proteins in EVs correlated to key pathways for tumor development. In this study, we used a proteomics approach correlating the two acquisitions-data-dependent acquisition (DDA) and data-independent acquisition (DIA)-on EVs from the conditioned medium of four cell lines identifying 428 ECM proteins. After protein quantification and statistical analysis, we found significant changes in the abundance (p < 0.05) of 67 proteins. Our bioinformatic analysis identified 26 pathways associated with the ECM. Western blotting analysis on 13 patients with type 1 and type 2 EC and 13 endometrial samples confirmed an altered abundance of MMP2. Our proteomics analysis identified the dysregulated ECM proteins involved in cancer growth. Our data can open the path to other studies for understanding the interaction among cancer cells and the rearrangement of the ECM.

A novel mutation in MECOM affects MPL regulation in vitro and results in thrombocytopenia and bone marrow failure

MECOM-associated syndrome (MECOM-AS) is a rare disease characterized by amegakaryocytic thrombocytopenia, progressive bone marrow failure, pancytopenia and radioulnar synostosis with high penetrance. The clinical phenotype may also include finger malformations, cardiac and renal alterations, hearing loss, B-cell deficiency and predisposition to infections. The syndrome, usually diagnosed in the neonatal period because of severe thrombocytopenia, is caused by mutations in the MECOM gene, encoding for the transcription factor EVI1. The mechanism linking the alteration of EVI1 function and thrombocytopenia is poorly understood. In a paediatric patient affected by severe thrombocytopenia, we identified a novel variant of the MECOM gene (p.P634L), whose effect was tested on pAP-1 enhancer element and promoters of targeted genes showing that the mutation impairs the repressive activity of the transcription factor. Moreover, we demonstrated that EVI1 controls the transcriptional regulation of MPL, a gene whose mutations are responsible for congenital amegakaryocytic thrombocytopenia (CAMT), potentially explaining the partial overlap between MECOM-AS and CAMT.

A Multi-Omics Approach Revealed Common Dysregulated Pathways in Type One and Type Two Endometrial Cancers

Endometrial cancer (EC) is the most frequent gynecologic cancer in postmenopausal women. Pathogenetic mechanisms that are related to the onset and progression of the disease are largely still unknown. A multi-omics strategy can help identify altered pathways that could be targeted for improving therapeutical approaches. In this study we used a multi-omics approach on four EC cell lines for the identification of common dysregulated pathways in type 1 and 2 ECs. We analyzed proteomics and metabolomics of AN3CA, HEC1A, KLE and ISHIKAWA cell lines by mass spectrometry. The bioinformatic analysis identified 22 common pathways that are in common with both types of EC. In addition, we identified five proteins and 13 metabolites common to both types of EC. Western blotting analysis on 10 patients with type 1 and type 2 EC and 10 endometria samples confirmed the altered abundance of NPEPPS. Our multi-omics analysis identified dysregulated proteins and metabolites involved in EC tumor growth. Further studies are needed to understand the role of these molecules in EC. Our data can shed light on common pathways to better understand the mechanisms involved in the development and growth of EC, especially for the development of new therapies.

Phospho-DIGE Identified Phosphoproteins Involved in Pathways Related to Tumour Growth in Endometrial Cancer

Endometrial cancer (EC) is the most common gynecologic malignancy of the endometrium. This study focuses on EC and normal endometrium phosphoproteome to identify differentially phosphorylated proteins involved in tumorigenic signalling pathways which induce cancer growth. We obtained tissue samples from 8 types I EC at tumour stage 1 and 8 normal endometria. We analyzed the phosphoproteome by two-dimensional differential gel electrophoresis (2D-DIGE), combined with immobilized metal affinity chromatography (IMAC) and mass spectrometry for protein and phosphopeptide identification. Quantities of 34 phosphoproteins enriched by the IMAC approach were significantly different in the EC compared to the endometrium. Validation using Western blotting analysis on 13 patients with type I EC at tumour stage 1 and 13 endometria samples confirmed the altered abundance of HBB, CKB, LDHB, and HSPB1. Three EC samples were used for in-depth identification of phosphoproteins by LC-MS/MS analysis. Bioinformatic analysis revealed several tumorigenic signalling pathways. Our study highlights the involvement of the phosphoproteome in EC tumour growth. Further studies are needed to understand the role of phosphorylation in EC. Our data shed light on mechanisms that still need to be ascertained but could open the path to a new class of drugs that could hinder EC growth.

Defective binding of ETS1 and STAT4 due to a mutation in the promoter region of THPO as a novel mechanism of congenital amegakaryocytic thrombocytopenia

Congenital amegakaryocytic thrombocytopenia (CAMT) is a recessive disorder characterized by severe reduction of megakaryocytes and platelets at birth, which evolves toward bone marrow aplasia in childhood. CAMT is mostly caused by mutations in MPL (CAMT-MPL), the gene encoding the receptor of thrombopoietin (THPO), a crucial cytokine regulating hematopoiesis. CAMT can be also due to mutations affecting the THPO coding region (CAMT-THPO). In a child with CAMT clinical picture, we identified the homozygous c.-323C>T substitution, affecting a potential regulatory region of THPO. Though mechanisms controlling the THPO transcription are not characterized, bioinformatics and in vitro analysis showed that c.-323C>T prevents the binding of transcription factors ETS1 and STAT4 to the putative THPO promoter, impairing THPO expression. Accordingly, in the proband the serum THPO concentration indicates defective THPO production. Based on these findings, the patient was treated with the THPOmimetic agent eltrombopag, inducing a significant increase in platelet count and stable remission of bleeding symptoms. Herein, we report a novel pathogenic variant responsible for CAMT and provide new insights into the mechanisms regulating the transcription of the THPO gene.

A Targeted Proteomics Approach for Screening Serum Biomarkers Observed in the Early Stage of Type I Endometrial Cancer

Endometrial cancer (EC) is the most common gynecologic malignancy, and it arises in the inner part of the uterus. Identification of serum biomarkers is essential for diagnosing the disease at an early stage. In this study, we selected 44 healthy controls and 44 type I EC at tumor stage 1, and we used the Immuno-oncology panel and the Target 96 Oncology III panel to simultaneously detect the levels of 92 cancer-related proteins in serum, using a proximity extension assay. By applying this methodology, we identified 20 proteins, associated with the outcome at binary logistic regression, with a p-value below 0.01 for the first panel and 24 proteins with a p-value below 0.02 for the second one. The final multivariate logistic regression model, combining proteins from the two panels, generated a model with a sensitivity of 97.67% and a specificity of 83.72%. These results support the use of the proposed algorithm after a validation phase.

Amplifying Tumor-Stroma Communication: An Emerging Oncogenic Function of Mutant p53

TP53 mutations are widespread in human cancers. An expanding body of evidence highlights that, in addition to their manifold cell-intrinsic activities boosting tumor progression, missense p53 mutants enhance the ability of tumor cells to communicate amongst themselves and with the tumor stroma, by affecting both the quality and the quantity of the cancer secretome. In this review, we summarize recent literature demonstrating that mutant p53 enhances the production of growth and angiogenic factors, inflammatory cytokines and chemokines, modulates biochemical and biomechanical properties of the extracellular matrix, reprograms the cell trafficking machinery to enhance secretion and promote recycling of membrane proteins, and affects exosome composition. All these activities contribute to the release of a promalignant secretome with both local and systemic effects, that is key to the ability of mutant p53 to fuel tumor growth and enable metastatic competence. A precise knowledge of the molecular mechanisms underlying the interplay between mutant p53 and the microenvironment is expected to unveil non-invasive biomarkers and actionable targets to blunt tumor aggressiveness.

A mutant p53/Hif1α/miR-30d axis reprograms the secretory pathway promoting the release of a prometastatic secretome

TP53 missense mutations are frequent driver events during tumorigenesis. The majority of TP53 mutations are missense and occur within the DNA binding domain of p53, leading to expression of mutant p53 (mut-p53) proteins that not only lose the tumor suppressive functions of the wild-type (wt-p53) form, but can also acquire novel oncogenic features fostering tumor growth, metastasis and chemoresistance. Mut-p53 affects fundamental cellular pathways and functions through different mechanisms, a major one being the alteration of gene expression. In our recent work (Capaci et al., 2020, Nat Commun) we found that mut-p53, via miR-30d, modifies structure and function of the Golgi apparatus (GA) and induces increased rate of trafficking. This culminates in the release of a pro-malignant secretome, which is capable of remodeling the tumor microenvironment (TME), to increase stiffness of the extracellular matrix (ECM), favouring metastatic colonization, as shown by cell-based assays and experiments of metastatic niche preconditioning in mouse xenograft models. This study provides new insights into the mechanisms by which mut-p53, through induction of non-coding RNAs, can exert pro-tumorigenic functions in a non-cell-autonomous fashion, and highlights potential non-invasive biomarkers and therapeutic targets to treat tumors harboring mut-p53 (Figure 1).

Mutant p53 induces Golgi tubulo-vesiculation driving a prometastatic secretome

TP53 missense mutations leading to the expression of mutant p53 oncoproteins are frequent driver events during tumorigenesis. p53 mutants promote tumor growth, metastasis and chemoresistance by affecting fundamental cellular pathways and functions. Here, we demonstrate that p53 mutants modify structure and function of the Golgi apparatus, culminating in the increased release of a pro-malignant secretome by tumor cells and primary fibroblasts from patients with Li-Fraumeni cancer predisposition syndrome. Mechanistically, interacting with the hypoxia responsive factor HIF1α, mutant p53 induces the expression of miR-30d, which in turn causes tubulo-vesiculation of the Golgi apparatus, leading to enhanced vesicular trafficking and secretion. The mut-p53/HIF1α/miR-30d axis potentiates the release of soluble factors and the deposition and remodeling of the ECM, affecting mechano-signaling and stromal cells activation within the tumor microenvironment, thereby enhancing tumor growth and metastatic colonization.

MCM7 and its hosted miR-25, 93 and 106b cluster elicit YAP/TAZ oncogenic activity in lung cancer

Lung cancer is the first cause of cancer death worldwide and the Hippo pathway transcriptional coactivators YAP/TAZ have a pro-oncogenic role in this context. In order to understand the mechanisms through which YAP/TAZ elicit their oncogenic role in different systems, many studies are focused on YAP/TAZ target genes involved in the regulation of cell proliferation/survival and migration. However, there is scarce evidence on the role of YAP/TAZ in microRNA regulation while there is increasing evidence supporting the role of microRNAs in the main oncogenic processes. Here, we showed that YAP/TAZ were able to regulate several microRNAs in non-small cell lung cancer (NSCLC) cell lines. In detail, we focused on a cluster of three oncogenic microRNAs (miR-25, 93 and 106b) hosted in the MCM7 gene that were overexpressed in lung tumors compared to normal tissues. In addition, similar behavior was observed in breast cancer and head and neck tumor casuistries, where they showed a prognostic role. In NSCLC cells, YAP/TAZ induced the transcription of the MCM7 gene and its hosted miRs, thereby promoting cell proliferation through the post-transcriptional inhibition of the p21 cell cycle regulator. Accordingly, p21 was maintained at low levels in lung tumors compared to normal tissues. Conversely, its expression was restored in NSCLC cells upon YAP/TAZ interference or upon treatment with the statin cerivastatin. In summary, we provide evidence for a novel mechanism of modulation supporting the protumorigenic functions of the YAP/TAZ factors through the modulation of a bioncogenic locus consisting of one gene and three hosted microRNAs.

The cytoplasmic side of p53's oncosuppressive activities

The tumor suppressor p53 is a transcription factor that in response to a plethora of stress stimuli activates a complex and context-dependent cellular response ultimately protecting genome integrity. In the last two decades, the discovery of cytoplasmic p53 localization has driven an intense research on its extra-nuclear functions. The ability to induce apoptosis acting directly at mitochondria and the related mechanisms of p53 localization and translocation in the cytoplasm and mitochondria have been dissected. However, recent works indicate the involvement of cytoplasmic p53 also in biological processes such as autophagy, metabolism, oxidative stress and drug response. This review will focus on the mechanisms of cytoplasmic p53 activation and the pathophysiological role of p53's transcription-independent functions, highlighting possible therapeutic implications.

Oncogenic miR-181a/b affect the DNA damage response in aggressive breast cancer

Breast cancer is a heterogeneous tumor type characterized by a complex spectrum of molecular aberrations, resulting in a diverse array of malignant features and clinical outcomes. Deciphering the molecular mechanisms that fuel breast cancer development and act as determinants of aggressiveness is a primary need to improve patient management. Among other alterations, aberrant expression of microRNAs has been found in breast cancer and other human tumors, where they act as either oncogenes or tumor suppressors by virtue of their ability to finely modulate gene expression at the post-transcriptional level. In this study, we describe a new role for miR-181a/b as negative regulators of the DNA damage response in breast cancer, impacting on the expression and activity of the stress-sensor kinase ataxia telangiectasia mutated (ATM). We report that miR-181a and miR-181b were overexpressed in more aggressive breast cancers, and their expression correlates inversely with ATM levels. Moreover we demonstrate that deregulated expression of miR-181a/b determines the sensitivity of triple-negative breast cancer cells to the poly-ADP-ribose-polymerase1 (PARP1) inhibition. These evidences suggest that monitoring the expression of miR-181a/b could be helpful in tailoring more effective treatments based on inhibition of PARP1 in breast and other tumor types.

A Pin1/mutant p53 axis promotes aggressiveness in breast cancer

TP53 missense mutations dramatically influence tumor progression, however, their mechanism of action is still poorly understood. Here we demonstrate the fundamental role of the prolyl isomerase Pin1 in mutant p53 oncogenic functions. Pin1 enhances tumorigenesis in a Li-Fraumeni mouse model and cooperates with mutant p53 in Ras-dependent transformation. In breast cancer cells, Pin1 promotes mutant p53 dependent inhibition of the antimetastatic factor p63 and induction of a mutant p53 transcriptional program to increase aggressiveness. Furthermore, we identified a transcriptional signature associated with poor prognosis in breast cancer and, in a cohort of patients, Pin1 overexpression influenced the prognostic value of p53 mutation. These results define a Pin1/mutant p53 axis that conveys oncogenic signals to promote aggressiveness in human cancers.