Expression of matrix metalloproteinases 2 and 7 in tumor cells correlates with the World Health Organization classification subtype and clinical stage of thymic epithelial tumors

Thymic epithelial tumours: histopathological classification and differential diagnosis

The epithelial and lymphoid compartments of the thymus can give rise to a wide variety of tumours, including thymomas, thymic carcinomas, lymphoreticular proliferations, germ cell tumours, and sarcomas. While some of these have close similarity to their counterparts in other organs, both in terms of histology and immunohistochemistry, as well as molecular features, others are unique to the thymus. The epithelial tumours, which can develop in the thymus, will be discussed in this review, with a particular emphasis on resolving differential diagnosis by means of morphology, immunohistochemical profiles, and molecular diagnostics.

Molecular and Functional Key Features and Oncogenic Drivers in Thymic Carcinomas

Thymic epithelial tumors, comprising thymic carcinomas and thymomas, are rare neoplasms. They differ in histology, prognosis, and association with autoimmune diseases such as myasthenia gravis. Thymomas, but not thymic carcinomas, often harbor GTF2I mutations. Mutations of CDKN2A, TP53, and CDKN2B are the most common thymic carcinomas. The acquisition of mutations in genes that control chromatin modifications and epigenetic regulation occurs in the advanced stages of thymic carcinomas. Anti-angiogenic drugs and immune checkpoint inhibitors targeting the PD-1/PD-L1 axis have shown promising results for the treatment of unresectable tumors. Since thymic carcinomas are frankly aggressive tumors, this report presents insights into their oncogenic drivers, categorized under the established hallmarks of cancer.

Prognostic factors and genetic markers in thymic epithelial tumors: A narrative review

Thymic epithelial tumors (TET) are a group of rare neoplasms of the anterior mediastinum comprising thymomas and thymic carcinomas. The carcinogenesis of TET is mostly unknown. Many studies, mostly retrospective case series, have tried to establish prognostic factors in TET. TET is a very heterogeneous group of tumors with many subtypes for which diagnosis and treatment remains a very challenging task. Despite the disparities among retrospective studies, there are some prognostic factors that are more pertinent such as the completeness of resection, TNM stage and the Masaoka-Koga classification. On the other hand, the identification of different genetic pathways that result in the pathogenesis of TET represents a fascinating field of study that could possibly lead to the development of new targeted therapies. The aim of this review is to discuss the different prognostic factors and genetic markers of TET. The meticulous use of national and international databases could provide sufficient number of patients in order to draw more valid conclusions.

Altered Extracellular Matrix as an Alternative Risk Factor for Epileptogenicity in Brain Tumors

Seizures are one of the most common symptoms of brain tumors. The incidence of seizures differs among brain tumor type, grade, location and size, but paediatric-type diffuse low-grade gliomas/glioneuronal tumors are often highly epileptogenic. The extracellular matrix (ECM) is known to play a role in epileptogenesis and tumorigenesis because it is involved in the (re)modelling of neuronal connections and cell-cell signaling. In this review, we discuss the epileptogenicity of brain tumors with a focus on tumor type, location, genetics and the role of the extracellular matrix. In addition to functional problems, epileptogenic tumors can lead to increased morbidity and mortality, stigmatization and life-long care. The health advantages can be major if the epileptogenic properties of brain tumors are better understood. Surgical resection is the most common treatment of epilepsy-associated tumors, but post-surgery seizure-freedom is not always achieved. Therefore, we also discuss potential novel therapies aiming to restore ECM function.

GAD1 expression and its methylation as indicators of malignant behavior in thymic epithelial tumors

Thymic epithelial tumors (TETs) comprise thymomas and thymic carcinoma (TC). TC has more aggressive features and a poorer prognosis than thymomas. Genetic and epigenetic alterations in thymomas and TC have been investigated in an attempt to identify novel target molecules for TC. In the present study, genome-wide screening was performed on aberrantly methylated CpG islands in thymomas and TC, and the glutamate decarboxylase 1 gene (GAD1) was identified as the 4th significantly hypermethylated CpG island in TC compared with thymomas. GAD1 catalyzes the production of γ-aminobutyric acid from L-glutamic acid. GAD1 expression is abundant in the brain but rare in other tissues, including the thymus. A total of 73 thymomas and 17 TC tissues were obtained from 90 patients who underwent surgery or biopsy at Tokushima University Hospital between 1990 and 2017. DNA methylation was examined by bisulfite pyrosequencing, and the mRNA and protein expression levels of GAD1 were analyzed using reverse transcription-quantitative PCR and immunohistochemistry, respectively. The DNA methylation levels of GAD1 were significantly higher in TC tissues than in the normal thymus and thymoma tissues, and GAD1 methylation exhibited high sensitivity and specificity for discriminating between TC and thymoma. The mRNA and protein expression levels of GAD1 were significantly higher in TC tissues than in thymomas. Patients with TET with high GAD1 DNA hypermethylation and high mRNA and protein expression levels had significantly shorter relapse-free survival rates than those with low levels. In conclusion, significantly more epigenetic alterations were observed in TC tissues compared with in thymomas, which may contribute to the clinical features and prognosis of patients.

An integrated bioinformatics analysis of potential therapeutic targets among matrix metalloproteinases in breast cancer

Breast cancer (BC) is one of the most aggressive malignancies worldwide among females. Matrix metalloproteinases (MMPs), as the most abundant class of non-serine proteases present in invasive and metastatic tumors, can regulate a variety of alterations in the microenvironment during tumor progression. However, the differential expression of MMPs and its prognostic values in BC is yet to be elucidated. In this research, using the ONCOMINE dataset, The Cancer Genome Atlas, Breast Cancer Gene-Expression Miner v4.1 (Bc-GenExMiner), Kaplan-Meier Plotter and cBioPortal, the transcriptional MMPs and survival outcome data of patients with BC was compared. It was indicated that mRNA levels of MMP1/3/9/10/11/12/13 were increased compared with non-tumor tissues, whereas mRNA expression of MMP2/16/19/23B/28 was lower in BC tissues. Kaplan-Meier plots showed that high mRNA levels of MMP2/10/16/19/20/23B/27 in patients with BC were associated with better recurrence-free survival. In contrast, high MMP1/8/9/11/12 conferred worse RFS rate. Meanwhile, high transcription levels of MMP1/3/11/12/13 predicted shorter distant metastasis-free survival, while high levels of MMP1/12 demonstrated worse overall survival in patients with BC. From Bc-GenExMiner, it was indicated that high expression of MMP16/20 was correlated with better prognosis, while MMP1/9/11/12/13/14/15 exerted a negative effect on patient prognosis. The integrative bioinformatics analysis performed in the present study suggests that MMP1/9/12/16, compared with other MMPs, are potentially appropriate targets for targeted therapy in patients with BC.

Prognostic factors and genetic markers in thymoma

In this literature review prognostic factors and genetic markers that play a role in the staging of thymomas are discussed. The effect on prognosis of different factors, such as paraneoplastic syndromes, age, gender, classification, capsular invasion and surgical treatment, is evaluated. There is no generally accepted pathological classification of thymomas. More recently developed surgical techniques such as video-assisted or robotic thoracic surgery require longer follow-up times to determine whether they have equal long-term results compared to the classical surgical techniques. Many genetic markers have been described but at the present time no definite guidelines can be provided regarding screening and staging of thymomas.

State of the art of genetic alterations in thymic epithelial tumors

The rapid advent of technology in recent years has resulted in a substantial increase in our knowledge of the molecular underpinnings of thymic epithelial tumors. In addition to previously described chromosomal aberrations and alterations in DNA methylation, genome sequencing has helped unravel hitherto unknown mutations in these tumors. Attempts are also being made to develop gene signatures to help in the identification of patients likely to benefit from adjuvant therapy. Some of the recently identified genetic alterations have the potential to serve as targets for biological therapy, thus opening newer avenues for treatment of thymic epithelial tumors and increasing the number of effective options for treatment of recurrent or refractory disease.

A gene signature to determine metastatic behavior in thymomas

Purpose

Thymoma represents one of the rarest of all malignancies. Stage and completeness of resection have been used to ascertain postoperative therapeutic strategies albeit with limited prognostic accuracy. A molecular classifier would be useful to improve the assessment of metastatic behaviour and optimize patient management.

Methods

qRT-PCR assay for 23 genes (19 test and four reference genes) was performed on multi-institutional archival primary thymomas (n = 36). Gene expression levels were used to compute a signature, classifying tumors into classes 1 and 2, corresponding to low or high likelihood for metastases. The signature was validated in an independent multi-institutional cohort of patients (n = 75).

Results

A nine-gene signature that can predict metastatic behavior of thymomas was developed and validated. Using radial basis machine modeling in the training set, 5-year and 10-year metastasis-free survival rates were 77% and 26% for predicted low (class 1) and high (class 2) risk of metastasis (P = 0.0047, log-rank), respectively. For the validation set, 5-year metastasis-free survival rates were 97% and 30% for predicted low- and high-risk patients (P = 0.0004, log-rank), respectively. The 5-year metastasis-free survival rates for the validation set were 49% and 41% for Masaoka stages I/II and III/IV (P = 0.0537, log-rank), respectively. In univariate and multivariate Cox models evaluating common prognostic factors for thymoma metastasis, the nine-gene signature was the only independent indicator of metastases (P = 0.036).

Conclusion

A nine-gene signature was established and validated which predicts the likelihood of metastasis more accurately than traditional staging. This further underscores the biologic determinants of the clinical course of thymoma and may improve patient management.

Clinicopathological analysis of small-sized thymoma with podoplanin and Ki 67 expression analysis

Thymoma is the most common tumor of the anterior mediastinum for which surgical resection is currently the primary form of treatment. An increase in the incidence of a small-sized (≤3 cm) thymoma (SST) has recently been noted. Clinicopathological factors and prognosis of SST have not been reported previously. In this study, the clinicopathological data of 21 SST patients were reviewed and podoplanin and Ki67 immunohistochemistry were assessed to determine the biological behavior of SSTs. Pathological diagnosis of SSTs revealed the following types: A (n=1), AB (n=8), B1 (n=5), B2 (n=6) and B3 (n=1). The Masaoka-Koga stages of 21 thymoma patients were I (n=16), II (n=3), III (n=1) and IVb (n=1). In the case of the stage IVb thymoma, phrenic nerve, mediastinal pleura invasion and anterior mediastinal lymph node metastasis were observed. The Ki67 labeling index of this stage IVb was found to be 3.2. This case was also positive for podoplanin and was one of the only 2 cases that were positive for podoplanin. This patient succumbed to thymoma. Advanced stage thymomas are possibly included in SSTs although the majority of SSTs are classified into early stages of disease. Findings of this study suggest that podoplanin analyzed by immunohistochemistry may be useful to determine the malignant behavior of SSTs.

Expression of podoplanin in thymoma: its correlation with tumor invasion, nodal metastasis, and poor clinical outcome

Recent studies have shown that podoplanin overexpression is associated with lymph node metastasis and poor clinical outcome in several malignant tumors. To investigate the role of podoplanin in thymoma, we examined 111 thymomas by immunohistochemistry using monoclonal antibody D2-40, which recognizes podoplanin. The tumors consisted of 8 type A, 40 type AB, 15 type B1, 23 type B2, 15 type B3, and 10 combined thymomas according to the World Health Organization histological classification system and of 41 stage I, 28 stage II, 16 stage III, 20 stage IVa, and 6 stage IVb thymomas according to the Masaoka staging system. We have found podoplanin expression in 0 (0%) type A, 4 (10%) type AB, 4 (27%) type B1, 16 (70%) type B2, 10 (67%) type B3, and 7 (70%) combined thymomas and in 5 (12%) cases of stage I, 7 (25%) of stage II, 11 (69%) of stage III, 12 (60%) of stage IVa, and all (100%) of stage IVb thymomas. Podoplanin was significantly expressed in B2/B3/combined thymomas and advanced stage thymomas (P < .0001). On survival analysis, podoplanin expression was significantly associated with an increased risk of death for the whole group of thymomas (P = .0002), although it was not identified as an independent prognostic factor in multivariate analysis. The significant survival curve differences of podoplanin expression were also seen for stage III/IVa/IVb thymomas (P = .0409) and B2/B3/combined thymomas (P = .0478). In conclusion, D2-40 immunostaining seems to be valuable for predicting the aggressive and metastatic potential of thymomas and the prognosis of the patients.

Potential diagnostic markers in nodular lesions of the thyroid gland: an immunohistochemical study

AIMS

The differential diagnosis of thyroid nodules in routine practice can be problemmatic for both pathologists and clinicians. Effective treatment requires a determination of the biological nature of the lesions. For this reason, ancilliary diagnostic markers along with histological examination of the nodules may be useful. The objective of this study was to evaluate the diagnostic usefulness of novel markers in the diagnosis of hyperplastic and neoplastic nodules.

METHODS

Forty eight thyroid lesions forming four diagnostic groups including adenomatous goiters (AS), follicular adenomas (FA), follicular (FC) and papillary carcinomas (PC) were examined using standard immunohistochemical methods. Monoclonal antibodies against galectin-3, matrix metalloproteinases (MMPs) -2 and -7 and endothelial markers CD31 and CD105 were used.

RESULTS

The cytoplasmatic expression of galectin-3 was positive in all cases of papillary carcinoma. Moreover, statistically significant differences between fused groups of benign (AS and FA) and malignant lesions (FC and PC) were found Fischer's exact test (p = 0.0001). No significant differences in cytoplasmic expression of MMPs -2 and -7 and in vascular density assessed by using of both endothelial markers between benign lesions and malignant tumors were revealed.

CONCLUSIONS

Galectin-3 appears to be a useful marker in the diagnosis of papillary carcinoma only. The matrix metalloproteinases-2 and -7 are not helpful in distinguishing hyperplastic and neoplastic thyroid nodules. Endothelial markers do not appear to be suitable for thyroid differential diagnosis. A panel of antibodies in the differential diagnosis of thyroid nodular lesions would seem most suitable and further studies with larger sets of patients are awaited.

Molecular pathology of thymic epithelial neoplasms

The etiology and molecular pathogenesis of thymic tumors are unknown. However, during the last two decades there has been some progress on elucidating the genetic abnormalities present and molecular pathways altered in thymic tumors. These abnormalities, while bearing distinctions and similarities to those described in other tumors, can be organized under the "hallmarks of cancer," as proposed by Hanahan and Weinberg. These changes include self-sufficiency in growth signaling, insensitivity to antigrowth signals, ability to evade apoptosis, limitless replicative potential, ability to sustain angiogenesis, and tissue invasion and metastasis. However, this progress is still limited and has not led to better tumor classifications, prognostication of outcome, and design of molecular targeted therapy.

Activation ratio of MMP-2 and expression of MT1-MMP are correlated in thymic epithelial tumours

AIMS

To study the relationships between the activation of pro-MMP-2 and the mRNA levels of MT1-MMP and TIMP-2 in thymic tissues and thymic epithelial tumours.

METHODS

We examined the mRNA expressions of MMP-2, MT1-MMP and TIMP-2 with real-time reverse transcription-polymerase chain reaction (RT-PCR). The gelatinolytic activity and MMP-2 activation ratio of thymic tissues, thymomas, and thymic carcinomas were determined with gelatin zymography. The cellular localisation of MMP-2 was detected with film in situ gelatin zymography. We then examined the mRNA expression of MMP-2 in the epithelial tumour cells or lymphocytes and stromal cells distant from the tumour (obtained from two invasive thymomas) using laser-capture microdissection (LCM).

RESULTS

The mRNA levels of MMP-2, MT1-MMP and TIMP-2 were significantly increased from thymic tissue, Stage I-II, III-IV thymomas to thymic carcinomas (p<0.005). They were also significantly increased from AB-B1 (lymphocyte rich and mixed types), B2-B3 (cortical and predominantly polygonal cells types) thymomas to thymic carcinomas (p<0.05). The MMP-2 activation ratio also had the same tendency among the above groups (p<0.05) and was directly correlated to MT1-MMP and TIMP-2 mRNA expression (Spearman rank correlation: r = 0.8627, r = 0.8314; p<0.005). Film in situ zymography demonstrated that positive expression is mainly localised in tumour cell nests and adjacent stroma cells. LCM and real-time RT-PCR results confirmed that the expression of MMP-2 was higher in epithelial tumour cells than in lymphocytes and stromal cells.

CONCLUSIONS

MMP-2, MT1-MMP and TIMP-2 mRNA expression levels were correlated with clinical stages and histological subtypes of thymic epithelial tumours. The activation of pro-MMP-2 might be mediated by MT1-MMP and TIMP-2 up-regulation.

MMP-7 (matrilysin) expression in human brain tumors

Matrix metalloproteinases (MMP) which degrades protein components of the extra-cellular matrix and basement membrane seems to be largely involved in cancer invasiveness. MMP proteolitic activity essentially comes from stromal cells but matrilysin (MMP-7) is produced by the tumor itself. Thus, MMP-7 is investigated to address the particular invasive behavior of human glioma. Both MMP-7 mRNA and protein were clearly identified in human glioma. MMP-7 mRNA expression was highly variable within our glioma population. When analyzing MMP-7 mRNA expression in different primary brain tumors, we found highly variable levels of expression not related to their invasive behavior. In successive biopsies obtained in the same patients with glioblastoma, MMP-7 mRNA was quantified and appeared variable, but intra-individual variations were lower than inter-individual differences. With a xenograft model of U87 human tumors in RAG2/gamma(c) immune-deficient mice, the strict tumor origin of MMP-7 was shown. Additionally, MMP-7 expression by U87 cells which is low in culture was stimulated by these cells while forming tumors and the level of expression was higher when the tumor cells were implanted within the brain. These data provide some consistent information about cross-talk occurring between the tumor and the surrounding stroma to regulate MMP-7 expression.

Expression of matrix metalloproteinases in benign and malignant follicular thyroid lesions

AIMS

To examine expression of matrix metalloproteinases (MMPs) and related proteins in follicular thyroid lesions (FTLs) and to determine their usefulness for differential diagnosis of FTLs, particularly between minimally invasive carcinoma and adenoma.

METHODS AND RESULTS

Six widely invasive follicular carcinomas (WIFCs), 15 minimally invasive follicular carcinomas (MIFCs), 19 follicular adenomas (FAs) and 10 adenomatous goitres (AGs) were analysed immunohistochemically for MMP-1, MMP-2, MMP-7, MMP-9, membrane-type 1-MMP (MT1-MMP) and tissue inhibitor of matrix metalloproteinase-2 (TIMP-2). MMP-1 was positive in all FTLs. MMP-2 and MMP-7 were positive in more than 80% of WIFC and MIFC cases, whereas they were negative in all FA and AG cases except one MMP-2+ FA (P < 0.001). MMP-9 stained positive significantly more in MIFC than FA or AG cases (P < 0.05, respectively). The positivity of MT1-MMP and TIMP-2 was different among some of the FTLs, but with no significant difference between MIFC and FA cases. In-situ hybridization of MMP-2 and MMP-7 mRNA in selected cases demonstrated the expression of these enzymes in the tumour cells as well as in some stromal cells.

CONCLUSIONS

Our results confirm MMP expression mainly in malignant FTLs and suggest that MMP-2 and MMP-7 may be useful markers to distinguish MIFC from FA.

Glia maturation factor-beta is produced by thymoma and may promote intratumoral T-cell differentiation

AIMS

To investigate whether Glia maturation factor-beta (GMFB) is expressed in thymomas and is associated with T-cell development.

METHODS AND RESULTS

We investigated the expression of GMFB by immunohistochemistry in 86 cases of thymoma classified into five type A, 35 type AB, 11 type B1, 26 type B2, and nine type B3 thymomas according to the World Health Organization classification system. Immunoblotting and in situ hybridization (ISH) studies were also performed in selected cases. The results of the immunoblot analysis were in accordance with those of immunohistochemical scoring. The ISH study ascertained the tumour cells producing the protein. Immunohistochemically, GMFB expression was observed in one (20%) of type A, 32 (80%) of type AB, all (100%) of type B1 and B2, and eight (89%) of type B3 thymoma with statistically significant differences between type A and type AB, type B1, or type B2 thymoma, and between type B3 and type AB or type B2 thymoma. There was a significant correlation between GMFB expression and the amount of accompanying non-neoplastic T cells. GMFB promoted T-cell differentiation into CD4-/CD8+ cells when analysed by two-colour flow cytometry.

CONCLUSIONS

The present study suggests that T-cell development in thymoma may be maintained partly by GMFB produced by the tumour cells.