Generation of an Obese Diabetic Mouse Model upon Conditional Atrx Disruption.

Atrx loss was recently ascertained as insufficient to drive pancreatic neuroendocrine tumour (PanNET) formation in mice islets. We have identified a preponderant role of Atrx in the endocrine dysfunction in a Rip-Cre;AtrxKO genetically engineered mouse model (GEMM). To validate the impact of a different Cre-driver line, we used similar methodologies and characterised the Pdx1-Cre;AtrxKO (P.AtrxKO) GEMM to search for PanNET formation and endocrine fitness disruption for a period of up to 24 months. Male and female mice presented different phenotypes. Compared to P.AtrxWT, P.AtrxHOM males were heavier during the entire study period, hyperglycaemic between 3 and 12 mo., and glucose intolerant only from 6 mo.; in contrast, P.AtrxHOM females started exhibiting increased weight gains later (after 6 mo.), but diabetes or glucose intolerance was detected by 3 mo. Overall, all studied mice were overweight or obese from early ages, which challenged the histopathological evaluation of the pancreas and liver, especially after 12 mo. Noteworthily, losing Atrx predisposed mice to an increase in intrapancreatic fatty infiltration (FI), peripancreatic fat deposition, and macrovesicular steatosis. As expected, no animal developed PanNETs. An obese diabetic GEMM of disrupted Atrx is presented as potentially useful for metabolic studies and as a putative candidate for inserting additional tumourigenic genetic events.

Prognostic Value of Bladder Involvement in the Outcome of Upper Tract Urothelial Carcinoma.

Accurately predicting the clinical prognosis of upper tract urothelial carcinoma (UTUC) seems crucial. We evaluated the effect of the involvement of urothelial bladder carcinoma (UBC) as a potential prognostic factor for overall survival (OS) and progression-free survival (PFS). The cohort included 115 patients with UTUC, subgrouped between January 2009 and December 2019 as follows: (1) only UTUC and (2) UTUC with synchronous or metachronous UBC (UTUC + UBC). Univariate and multivariate analyses were performed to identify independent prognostic factors for OS and PFS. Synchronous or metachronous UBC diagnosis in UTUC patients was an independent predictor of worse PFS (HR 3.326 CI 95% 1.474−7.503, p = 0.004), but it was not identified as a prognostic factor for OS (p > 0.05). Lymphovascular invasion (LVI) was associated with decreased PFS (HR 2.687 CI 95%1.172−6.163, p = 0.020) and OS (HR 4.980 CI 95%1.763−14.064, p = 0.002). This study indicates that concomitant or later UBC could predict a poor PFS, but it is not associated with a significantly worse OS in UTUC patients. The prognostic impact of LVI underlines its inclusion in the tumor staging system of UTUC.

An update on genetically engineered mouse models of pancreatic neuroendocrine neoplasms.

Pancreatic neuroendocrine neoplasms (PanNENs) are rare and clinically challenging entities. At the molecular level, PanNENs' genetic profile is well characterized, but there is limited knowledge regarding the contribution of the newly identified genes to tumor initiation and progression. Genetically engineered mouse models (GEMMs) are the most versatile tool for studying the plethora of genetic variations influencing PanNENs' etiopathogenesis and behavior over time. In this review, we present the state of the art of the most relevant PanNEN GEMMs available and correlate their findings with the human neoplasms' counterparts. We discuss the historic GEMMs as the most used and with higher translational utility models. GEMMs with Men1 and glucagon receptor gene germline alterations stand out as the most faithful models in recapitulating human disease; RIP-Tag models are unique models of early-onset, highly vascularized, invasive carcinomas. We also include a section of the most recent GEMMs that evaluate pathways related to cell cycle and apoptosis, Pi3k/Akt/mTOR, and Atrx/Daxx. For the latter, their tumorigenic effect is heterogeneous. In particular, for Atrx/Daxx, we will require more in-depth studies to evaluate their contribution; even though they are prevalent genetic events in PanNENs, they have low/inexistent tumorigenic capacity per se in GEMMs. Researchers planning to use GEMMs can find a road map of the main clinical features in this review, presented as a guide that summarizes the chief milestones achieved. We identify pitfalls to overcome, concerning the novel designs and standardization of results, so that future models can replicate human disease more closely.

Patients and healthcare professionals perspectives on creating a chronic pain support line in Portugal: A qualitative study protocol.

Chronic pain affects almost 38% of the Portuguese adult population, with high costs for both patients and society. Those who suffer with chronic pain frequently complain of feeling misunderstood and of lack of support. These complaints are the main reason why support telephone lines for chronic pain were created in some countries. However, there is no scientific data supporting their creation or evaluating their performance. This paper presents a qualitative study protocol to assess patients and healthcare professionals' perspectives on the creation of a telephone support line for chronic pain. It constitutes the first step to attain the main goal of developing and implementing a functioning support line for chronic pain in Portugal. The methodology to assess patients and healthcare professionals' perspectives and needs is presented. In order to gather information as close to reality as possible, focus groups interviews were chosen as data sources. Given the present context of the COVID-19 pandemic, meetings will take place online, using a digital platform. All interviews will be transcribed verbatim, coded and synthesised into categories and main themes. Thematic analysis will be conducted using NVivo® V12 software, employing an iterative and reflexive approach. Finally, comparative and relational analysis will be performed in order to identify topics where patients and professionals converge or greatly diverge. The findings will be useful for grounding the creation of a telephone support line for chronic pain patients. Results dissemination will be important for policy-makers to develop a new perspective towards chronic pain services available.

Characterisation of an Atrx Conditional Knockout Mouse Model: Atrx Loss Causes Endocrine Dysfunction Rather Than Pancreatic Neuroendocrine Tumour.

ATRX is a chromatin remodeller that maintains telomere homeostasis. Loss of ATRX is described in approximately 10% of pancreatic neuroendocrine tumours (PanNETs) and associated with poorer prognostic features. Here, we present a genetically engineered mouse model (GEMM) addressing the role of Atrx loss (AtrxKO) in pancreatic ß cells, evaluating a large cohort of ageing mice (for up to 24 months (mo.)). Atrx loss did not cause PanNET formation but rather resulted in worsening of ageing-related pancreatic inflammation and endocrine dysfunction in the first year of life. Histopathological evaluation highlighted an exacerbated prevalence and intensity of pancreatic inflammation, ageing features, and hepatic steatosis in AtrxKO mice. Homozygous floxed mice presented hyperglycaemia, increased weights, and glucose intolerance after 6 months, but alterations in insulinaemia were not detected. Floxed individuals presented an improper growth of their pancreatic endocrine fraction that may explain such an endocrine imbalance. A pilot study of BRACO-19 administration to AtrxKO mice resulted in telomere instability, reinforcing the involvement of Atrx in the maintenance of ß cell telomere homeostasis. Thereby, a non-obese dysglycaemic GEMM of disrupted Atrx is here presented as potentially useful for metabolic studies and putative candidate for inserting additional tumourigenic genetic events.

Connexin Expression in Pituitary Adenomas and the Effects of Overexpression of Connexin 43 in Pituitary Tumor Cell Lines.

Gap junction intercellular communication (GJIC) is considered a key mechanism in the regulation of tissue homeostasis. GJIC structures are organized in two transmembrane channels, with each channel formed by connexins (Cxs). GJIC and Cxs expression alterations are related to the process of tumorigenesis in different cell types. Pituitary neuroendocrine tumors (PitNETs) represent 15-20% of intracranial neoplasms, and usually display benign behavior. Nevertheless, some may have aggressive behavior, invading adjacent tissues, and featuring a high proliferation rate. We aimed to assess the expression and relevance of GJIC and Cxs proteins in PitNETs. We evaluated the mRNA expression levels of Cx26, 32, and 43, and the protein expression of Cx43 in a series of PitNETs. In addition, we overexpressed Cx43 in pituitary tumor cell lines. At the mRNA level, we observed variable expression of all the connexins in the tumor samples. Cx43 protein expression was absent in most of the pituitary tumor samples that were studied. Moreover, in vitro studies revealed that the overexpression of Cx43 decreases cell growth and induces apoptosis in pituitary tumor cell lines. Our results indicate that the downregulation of Cx43 protein might be involved in the tumorigenesis of most pituitary adenomas and have a potential therapeutic value for pituitary tumor therapy.

Clinicopathological features of head and neck cutaneous basal cell carcinoma observed at the Centro Hospitalar de Trás-os-Montes e Alto Douro ENT Department.

Background: Cutaneous basal cell carcinoma (cBCC) incidence has been increasing, but there are no available data on its epidemiological, clinical, and pathological patterns in Northeast Portugal. cBCC is mainly located in the head and neck, where the ear, neck, and throat (ENT) surgeon may have a major role. We aimed to verify the clinicopathological characteristics of basal cell carcinomas diagnosed in an ENT department. Methods: We performed a retrospective clinicopathological evaluation of the head and neck cBCC cases followed up at the Centro Hospitalar de Trás-os-Montes e Alto Douro (CHTMAD) ENT Department between January 2007 and April 2021. Results: One hundred seventy-four patients with 293 cBCCs were included in this retrospective study. We observed that about one-third of the patients had multiple cBCCs (30.5%) and an infiltrative-type growth pattern (39.3%), both features considered as patterns that are more aggressive. Infiltrative-type growth pattern cBCCs were significantly larger when compared with the indolent-type growth pattern (16.2 mm vs 10.8 mm). Conclusions: To the best of our knowledge, this is the first study about cBCC in a patient population followed up at an ENT hospital department. This study has shown that these patients had cBCCs with more aggressive features, making these tumors an important issue for the ENT surgeon.

TERT Promoter Mutational Status in the Management of Cutaneous Melanoma: Comparison with Sentinel Lymph Node Biopsy.

BACKGROUND: While BRAF mutations seem important for early melanomagenesis, mutations in the TERT promoter (TERTp) are related to metastasis. Yet, in conventional melanoma management, risk stratification does not depend on molecular biomarkers that can indicate the stage of progression, but rather on clinical, pathological, sentinel lymph node (SLN), and radiologic evaluation. The aim of this work was to evaluate the frequency and prognostic impact of TERTp mutations, comparing their predictive value to those of conventional procedures in melanoma management. METHODS: Mutational analysis of a series of 91 cases was performed. The correlations between TERTp and BRAF mutational status and clinicopathological features were assessed. RESULTS: The mutation rate was 33% for TERTp and 30% for BRAF. There was 68% concordance between primary and metastatic samples for TERTp mutations and 92% for BRAF mutations. TERTp mutations are significantly associated with the presence of BRAF mutations, features of worse prognosis, and a reduced disease-free survival. Also, TERTp mutational status was similar to SLN biopsy as a predictive factor of cutaneous melanoma recurrence and metastasis. CONCLUSIONS: The predictive value of TERTp mutations may be similar to that of SLN biopsy and its integration in the management algorithm of melanoma patients should be considered.

Pain as the fifth vital sign-A comparison between public and private healthcare systems.

BACKGROUND: The assessment of pain as the fifth vital sign (P5VS) is of paramount importance since it leads to the management of undertreated pain, consequently reducing suffering, readmissions and emergency department visits after hospital discharge. OBJECTIVE: To evaluate the implementation of P5VS in public and private hospitals. METHODS: Data analysis on validated questionnaires was sent to all 171 Portuguese hospitals via an official letter. RESULTS: When compared to private hospitals, public hospitals presented a higher adherence to the process related to the P5VS. It has demonstrated superiority in the charts properly placed to record P5VS, in the number of emergency departments recording P5VS, in the regularity of audits, and in the existence of guidelines and staff training on pain assessment and management. CONCLUSION: The standardization of both evaluation and recording of pain intensity constitutes a measure of good clinical practice. Public hospitals demonstrated better commitment to these procedures that should be properly carried out in all health care institutions.

TLR4 Antagonism Reduces Movement-Induced Nociception and ATF-3 Expression in Experimental Osteoarthritis.

INTRODUCTION: Toll-like receptor 4 (TLR4) is a pattern recognition receptor involved in the detection of pathogen-associated molecular patterns (PAMPs), but also a "danger-sensing" receptor that recognizes host-derived endogenous molecules called damage-associated molecular patterns (DAMPs). The involvement of TLR4 in rheumatic diseases is becoming evident, as well as its potential role as a target for therapeutic intervention. Moreover, increasing evidence also suggests that TLR4 is implicated in chronic pain states. Thus, in this study, we evaluated whether a systemic administration of a synthetic antagonist of TLR4 (TLR4-A1) could decrease nociception and cartilage degradation in experimental osteoarthritis (OA). Furthermore, as the activation transcription factor (ATF)-3 serves as a negative regulator for TLR4-stimulated inflammatory response, we also evaluated the effect of TLR4 inhibition on ATF-3 expression in primary afferent neurons at the dorsal root ganglia (DRG). METHODS: OA was induced in adult male Wistar rats through an intra-articular injection of 2 mg of sodium mono-iodoacetate (MIA) into the left knee. From days 14 to 28 after OA induction, animals received an intraperitoneal injection of either TLR4-A1 (10 mg/kg) or vehicle. Movement- and loading-induced nociception was evaluated in all animals, by the Knee-Bend and CatWalk tests, before and at several time-points after TLR4-A1/vehicle administration. Immunofluorescence for TLR4 and ATF-3 was performed in L3-L5 DRG. Knee joints were processed for histopathological evaluation. RESULTS: Administration of TLR4-A1 markedly reduced movement-induced nociception in OA animals, particularly in the Knee-Bend test. Moreover, the increase of ATF-3 expression observed in DRG of OA animals was significantly reduced by TLR4-A1. However, no effect was observed in cartilage loss nor in the neuronal cytoplasmic expression of TLR4 upon antagonist administration. CONCLUSION: The TLR4 antagonist administration possibly interrupts the TLR4 signalling cascade, thus decreasing the neurotoxic environment at the joint, which leads to a reduction in ATF-3 expression and in nociception associated with experimental OA.

Langerhans Cell Histiocytosis-A Benign Presentation Heralding a Serious Disease.

A 3-year old White boy was referred to our dermatology department with a papular disseminated eruption, evolving for 7 months. Several topical antibiotics and corticosteroids were used without improvement. The dermatosis was locally asymptomatic, and systemic symptoms were absent. Examination revealed multiple, skin-colored to pinkish monomorphic papules with a generalized distribution involving the face, trunk, and limbs (Figure 1). The lesions spared the scalp, palms, and soles. Cervical, axillary, and inguinal lymphatic nodes were not palpable. Cutaneous biopsy of one of the abdominal lesions revealed an unremarkable epidermis but a reticular dermis with clusters of histiocytic, lymphocytic, and rare eosinophil cells. In the immunohistochemical study, expression of CD1a was observed in the histiocytic cells and S100 in the antigen-presenting cells of the dermal infiltrate (Figures 2 and 3). Taking into account the clinical presentation and the histopathologic result, a diagnosis of Langerhans cell histiocytosis (LCH) was established.

Combinatorial Therapies to Overcome BRAF/MEK Inhibitors Resistance in Melanoma Cells: An in vitro Study.

BACKGROUND: Melanoma accounts for only 1% of all skin malignant tumors; however, it is the deadliest form of skin cancer. Since 2011, FDA (Food and Drug Administration) approved several novel therapeutic strategies, such as MAPK pathway targeted therapies, to treat cutaneous melanoma patients. However, their improvements in overall survival were limited, due to the development of resistance. METHODS: In this work, several combinations of therapies, including the metabolic modulator DCA, were tested in melanoma cell lines, considering that MAPK and PI3K/AKT/mTOR pathways are deregulated and interconnected in melanoma and that the presence of the Warburg effect in melanoma cells may influence the response to therapy. The effect of the treatments was assessed in the proliferation and survival of melanoma cell lines with different genetic profiles. Also, the possibility to overcome resistance to the treatment with vemurafenib was tested. RESULTS: In general, higher decrease in cell viability and cell proliferation and increase in apoptosis were obtained after the combination treatments, comparing with single treatments, in all the studied cell lines. The combination of cobimetinib and everolimus appear to be the best treatment option. The BRAFV600E -vemurafenib resistant melanoma cell line showed to retain sensitivity to both everolimus and DCA. DISCUSSION AND CONCLUSION: Our results suggest that the combination of MAPK pathway inhibitors with mTOR pathway inhibitors and DCA should be considered as therapeutic options to treat melanoma patients, as the combinations potentiated the effects of each drug alone. In a cell line resistant to vemurafenib, we verified that combined MAPK inhibitors with inhibition of mTOR pathway and/or DCA metabolism modulation might constitute possible strategies in order to overcome resistance to MAPK inhibition.

TERTp mutations and p53 expression in head and neck cutaneous basal cell carcinomas with different aggressive features.

Cutaneous basal cell carcinoma (cBCC) is an economic burden to health services, due to its great morbidity and increasing incidence in old people. Infiltrative cBCCs and cBCCs with micronodular pattern are considered as more aggressive. The role of p53 expression and TERTp mutation on cBCC behavior remains to be clarified. We aimed to assess TERTp mutations and p53 expression in relation to the cBCC histological subtype in a cohort of patients referred to an ENT Department of a tertiary Hospital of Northern Portugal. We performed a retrospective clinicopathological and histological review of the head and neck cBCCs followed-up at the otorhinolaryngology department of Trás-os-Montes e Alto Douro hospital (January 2007-June 2018). We assessed TERTp mutations in 142 cBCCs and p53 protein expression, through immunohistochemistry, in 157 cBCCs. We detected TERTp mutations in 43.7% of cBCCs and p53 overexpression in 60.5% of cBCCs. We spotted association of p53 overexpression and TERTp mutation with necrosis. In the infitrative-growth pattern cBCCs, there was no significant association with the clinical and histological features evaluated, except for necrosis. In the indolent-growth cBCCs, we identified a significant association of TERTp mutation status with female sex, necrosis, multiple cBCCs, and p53 positive expression. Our results suggest that TERTp mutation may be useful to identify more aggressive features in the indolent-growth pattern cBCCs (nodular and superficial subtypes). Further studies with larger cohorts are warranted to clarify the relevance of TERTp mutation in cBCCs.

The role of c-Met and VEGFR2 in glioblastoma resistance to bevacizumab.

Dismal prognosis of glioblastoma (GBM) prompts for the identification of response predictors and therapeutic resistance mechanisms of current therapies. The authors investigated the impact of c-Met, HGF, VEGFR2 expression and microvessel density (MVD) in GBM patients submitted to second-line chemotherapy with bevacizumab. Immunohistochemical expression of c-Met, HGF, VEGFR2, and MVD was assessed in tumor specimens of GBM patients treated with bevacizumab, after progression under temozolomide. Survival analysis was evaluated according to the expression of the aforementioned biomarkers. c-Met overexpression was associated with a time-to-progression (TTP) after bevacizumab of 3 months (95% CI, 1.5-4.5) compared with a TTP of 7 months (95% CI, 4.6-9.4) in patients with low or no expression of c-Met (p = 0.05). VEGFR2 expression was associated with a TTP after bevacizumab of 3 months (95% CI, 1.8-4.2) compared with a TTP of 7 months (95% CI, 5.7-8.3) in patients with no tumoral expression of VEGFR2 (p = 0.009). Concomitant c-Met/VEGFR2 overexpression was associated with worse overall survival (13 months) compared with concomitant c-Met/VEGFR2 negative expression (19 months; p = 0.025). Our data support the hypothesis that c-Met and VEGFR2 overexpression have a role in the development of glioblastoma early resistance and might predict poorer responses to anti-angiogenic therapies.

Embryonal Tumors of the Central Nervous System: The WHO 2016 Classification and New Insights.

Central nervous system tumors comprise 26% of cancer in children, representing the most frequent solid neoplasms. Embryonal tumors comprise 15% of them, and they are defined as "small round blue cells" in which morphology is reminiscent of the developing embryonic nervous system. They are the most common high-grade central nervous system neoplasms. Over the years, molecular research has been improving our knowledge concerning these neoplasms, stressing the need for tumor reclassification. Indeed, the revised 2016 fourth edition of the World Health Organization classification introduced genetic parameters in the classification. Specific molecular signatures allow a more accurate risk assessment, leading to proper therapeutic approach and potentially improved prognosis. Holding this new approach, medulloblastoma is noteworthy. The present classification combines the previous histologic classification with a new genetic definition in WNT-activated, sonic hedgehog-activated and non-WNT/non-sonic hedgehog. Molecular data are also a defining feature in the diagnosis of atypical teratoid/rhabdoid tumors and embryonal tumors with multilayered rosettes. However, there are still embryonal tumors that challenge the present World Health Organization classification, and new molecular data have been underlining the need for novel tumor entities. Likewise, recent research has been highlighting heterogeneity in recognized entities. How to translate these molecular developments into routine clinical practice is still a major challenge.

MOHS micrographic surgery for head and neck nonmelanoma skin cancer: An approach for ENT surgeons.

Surgery is the main approach for skin cancer, with Mohs micrographic surgery (MMS) allowing the highest cure rates, best esthetics and superior functional outcomes. Ear, nose, and throat (ENT) surgeons are often challenged with patients presenting skin cancer, needing appropriate expertise to its adequate management. This paper highlights the most important aspects of MMS, enabling ENT surgeons to become familiar with its fundamental aspects. A review of the literature was performed, concomitantly presenting the author's outcomes as an ENT surgeon. A total of 51 MMSs were performed in 41 patients, and 78.4% of the tumors were cutaneous basal cell carcinomas (cBCCs), 19.6% were cutaneous squamous cell carcinomas (cSCCs), and one case was a microcystic adnexal carcinoma. Most tumors were located in high-risk areas (88.2%), and 84.3% of them were ≥10 mm in diameter. Most tumors (90.2%) required no more than two MMS excision steps to be completely removed. All cases were managed by reconstruction either using flaps or grafts. Recurrence occurred in only 2% of the cases. This study addressed the main issues of MMS, which may be important in ENT surgeons' daily practice.

Clinical characteristics and incidence of glucose metabolism disorders during the follow-up of surgically treated insulinomas.

PURPOSE: Insulinomas are pancreatic endocrine tumors characterized by hypoglycemia resulting from hypersecretion of insulin. The long-term impact of surgical treatment of insulinomas, particularly the risk of glucose metabolism disorders, remains largely unknown. METHODS: We retrospectively evaluated all patients with insulinoma submitted to surgery at Centro Hospitalar Universitário de São João (Porto, Portugal) between 1980 and 2016. We evaluated baseline characteristics of patients at presentation, imaging evaluation, surgical treatment, characteristics of the tumors, perioperative complications, disease remission, and long-term follow-up and metabolic outcomes. RESULTS: Twenty-eight patients with insulinomas submitted to surgical treatment were included. Sixty-one percent were female, and the average age was 46.4 years. The most reported symptoms were confusion (72%) and diaphoresis (56%). The most used imaging technique was abdominal CT (72%), and the test with the highest percentage of positive results was endoscopic ultrasound (80%). The most used surgical procedure was partial pancreatic resection (71%). The mean tumor diameter was 2.1 cm and 11% of the tumors had lymph node involvement at diagnosis. Pancreatic fistula was the most common postoperative acute complications (21%). After surgery, patients were followed for a median time of 80 months (25th-75th percentile: 20-148 months). Eight patients (32%) developed glucose metabolism disorders (seven developed diabetes and one prediabetes). One of these patients developed albuminuria, and no macrovascular complications were observed during the follow-up. CONCLUSIONS: Disorders of glucose metabolism are a frequent complication during follow-up of surgically treated insulinomas. The prevention, early diagnosis, and treatment of diabetes should be a priority in the follow-up of these patients.

Cutaneous Angiosarcoma in an Unusual Location and Without Predisposing Factors.

Cutaneous angiosarcoma is a rare, highly malignant tumour of vascular endothelial origin. It usually arises in the skin and superficial soft tissue, mostly on the head and neck. It presents as a variety of lesions, and so is considered a great mimicker, leading to a delay in diagnosis and evidencing the importance of biopsy with immunohistochemistry confirmation. There are few reports of extremity involvement in patients with pre-existing chronic lymphoedema, or exposure to radiation therapy. We report the case of an 82-year-old woman with lower limb extensive cutaneous involvement, distant metastatic disease, and poor therapy response. Its rare location without predisposing factors highlights the need to raise awareness about this disease. LEARNING POINTS: Extremity involvement of cutaneous angiosarcoma has been rarely described. The marked heterogeneity in presentation leads to a delay in diagnosis and poor prognosis, so the index of suspicion should be high.The cases reported in the literature describe a well-known relationship between cutaneous angiosarcoma and predisposing factors, but its absence should not exclude the diagnosis.This case highlights the importance of recognizing and biopsy suspected skin lesions for immunohistochemistry diagnostic confirmation.

Regulation of invasion and peritoneal dissemination of ovarian cancer by mesothelin manipulation.

Peritoneal dissemination is a particular form of metastasis typically observed in ovarian cancer and the major cause for poor patient's outcome. Identification of the molecular players involved in ovarian cancer dissemination can offer an approach to develop treatment strategies to improve clinical prognosis. Here, we identified mesothelin (MSLN) as a crucial protein in the multistep process of peritoneal dissemination of ovarian cancer. We demonstrated that MSLN is overexpressed in primary and matched peritoneal metastasis of high-grade serous carcinomas (HGSC). Using several genetically engineered ovarian cancer cell lines, resulting in loss or gain of function, we found that MSLN increased cell survival in suspension and invasion of tumor cells through the mesothelial cell layer in vitro. Intraperitoneal xenografts established with MSLNhigh ovarian cancer cell lines showed enhanced tumor burden and spread within the peritoneal cavity. These findings provide strong evidences that MSLN is a key player in ovarian cancer progression by triggering peritoneal dissemination and provide support for further clinical investigation of MSLN as a therapeutic target in HGSC.