Promoter hypermethylation inactivates CDKN2A, CDKN2B and RASSF1A genes in sporadic parathyroid adenomas

Advances and challenges in thyroid cancer: The interplay of genetic modulators, targeted therapies, and AI-driven approaches

Thyroid cancer continues to exhibit a rising incidence globally, predominantly affecting women. Despite stable mortality rates, the unique characteristics of thyroid carcinoma warrant a distinct approach. Differentiated thyroid cancer, comprising most cases, is effectively managed through standard treatments such as thyroidectomy and radioiodine therapy. However, rarer variants, including anaplastic thyroid carcinoma, necessitate specialized interventions, often employing targeted therapies. Although these drugs focus on symptom management, they are not curative. This review delves into the fundamental modulators of thyroid cancers, encompassing genetic, epigenetic, and non-coding RNA factors while exploring their intricate interplay and influence. Epigenetic modifications directly affect the expression of causal genes, while long non-coding RNAs impact the function and expression of micro-RNAs, culminating in tumorigenesis. Additionally, this article provides a concise overview of the advantages and disadvantages associated with pharmacological and non-pharmacological therapeutic interventions in thyroid cancer. Furthermore, with technological advancements, integrating modern software and computing into healthcare and medical practices has become increasingly prevalent. Artificial intelligence and machine learning techniques hold the potential to predict treatment outcomes, analyze data, and develop personalized therapeutic approaches catering to patient specificity. In thyroid cancer, cutting-edge machine learning and deep learning technologies analyze factors such as ultrasonography results for tumor textures and biopsy samples from fine needle aspirations, paving the way for a more accurate and effective therapeutic landscape in the near future.

Molecular and Clinical Spectrum of Primary Hyperparathyroidism

Recent data suggest an increase in the overall incidence of parathyroid disorders, with primary hyperparathyroidism (PHPT) being the most prevalent parathyroid disorder. PHPT is associated with morbidities (fractures, kidney stones, chronic kidney disease) and increased risk of death. The symptoms of PHPT can be nonspecific, potentially delaying the diagnosis. Approximately 15% of patients with PHPT have an underlying heritable form of PHPT that may be associated with extraparathyroidal manifestations, requiring active surveillance for these manifestations as seen in multiple endocrine neoplasia type 1 and 2A. Genetic testing for heritable forms should be offered to patients with multiglandular disease, recurrent PHPT, young onset PHPT (age ≤40 years), and those with a family history of parathyroid tumors. However, the underlying genetic cause for the majority of patients with heritable forms of PHPT remains unknown. Distinction between sporadic and heritable forms of PHPT is useful in surgical planning for parathyroidectomy and has implications for the family. The genes currently known to be associated with heritable forms of PHPT account for approximately half of sporadic parathyroid tumors. But the genetic cause in approximately half of the sporadic parathyroid tumors remains unknown. Furthermore, there is no systemic therapy for parathyroid carcinoma, a rare but potentially fatal cause of PHPT. Improved understanding of the molecular characteristics of parathyroid tumors will allow us to identify biomarkers for diagnosis and novel targets for therapy.

Cyclin Dependent Kinase Inhibitor 2A Genetic and Epigenetic Alterations Interfere with Several Immune Components and Predict Poor Clinical Outcome

Cyclin dependent kinase inhibitor 2A (CDKN2A) is a well-known tumor suppressor gene as it functions as a cell cycle regulator. While several reports correlate the malfunction of CDKN2A with the initiation and progression of several types of human tumors, there is a lack of a comprehensive study that analyzes the potential effect of CDKN2A genetic alterations on the human immune components and the consequences of that effect on tumor progression and patient survival in a pan-cancer model. The first stage of the current study was the analysis of CDKN2A differential expression in tumor tissues and the corresponding normal ones and correlating that with tumor stage, grade, metastasis, and clinical outcome. Next, a detailed profile of CDKN2A genetic alteration under tumor conditions was described and assessed for its effect on the status of different human immune components. CDKN2A was found to be upregulated in cancerous tissues versus normal ones and that predicted the progression of tumor stage, grade, and metastasis in addition to poor prognosis under different forms of tumors. Additionally, CDKN2A experienced different forms of genetic alteration under tumor conditions, a characteristic that influenced the infiltration and the status of CD8, the chemokine CCL4, and the chemokine receptor CCR6. Collectively, the current study demonstrates the potential employment of CDKN2A genetic alteration as a prognostic and immunological biomarker under several types of human cancers.

Sporadic parathyroid adenoma: an updated review of molecular genetics

Introduction

Primary HPT (PHPT) is a common disorder, affecting approximately 1% of the general population. Parathyroid adenomas emerge as non-familial sporadic in 90% of cases. The aim of this review is to give a detailed update of molecular genetics of sporadic parathyroid adenoma reported in international literature.

Methods

A bibliographic research was conducted in PubMed, Google Scholar, and Scopus.

Results

Seventy-eight articles were included in our review. CaSR, MEN1, CCND1/PRAD, CDKI, angiogenic factors like VEGF, FGF, TGFβ, and IGF1, and apoptotic factors are important genes in parathyroid adenomas pathogenesis that have been established by several studies. A huge list of proteins is differently expressed in parathyroid adenomas measured by Western Blotting, MALDI/TOF, MS spectrometry, and immunohistochemistry. These proteins take part in several cell processes such as cell metabolism, cytoskeleton structural stability, cell oxidative stress regulation, cell death, transcription, translation, cell connection, and cell signaling transmission, while they can be found over- or underexpressed in abnormal tissues.

Conclusion

This review gives a detailed analysis of all reported data on genomics and proteomics of parathyroid adenoma. Further studies should be applied on understanding parathyroid adenoma pathogenesis and introducing new biomarkers for early detection of primary hyperparathyroidism.

Quantitative application of dual-phase 99mTc-sestamibi SPECT/CT imaging of parathyroid lesions: identification of optimal timing in secondary hyperparathyroidism

PURPOSE

In this retrospective study, we compared the maximum standardized uptake values (SUVmax) of parathyroid lesions and the target-to-background ratio (TBR) of parathyroid lesions to thyroid tissue in early-phase single-photon emission computed tomography/computed tomography (SPECT/CT) versus delayed-phase SPECT/CT in patients with secondary hyperparathyroidism (SHPT) in order to determine the optimal timing of 99mTc- methoxyisobutylisonitrile (99mTc-MIBI) SPECT/CT imaging.

METHODS

Seventeen patients with a history of chronic kidney failure stage 5 on hemodialysis, underwent pre-operative parathyroid scintigraphy for detection and localization of parathyroid lesions. Retrospective analysis was conducted for lesions with focal accumulation of 99mTc-MIBI. All patients underwent dual-phase 99mTc-MIBI parathyroid scintigraphy and dual-phase SPECT/CT. SUVmax of parathyroid lesions and thyroid tissues was measured.

RESULTS

Mean SUVmax of parathyroid lesions was 4.86 on early-phase and 2.58 on delayed-phase SPECT/CT, respectively. Mean TBR was 1.14 on early phase and 1.48 on delayed-phase SPECT/CT, respectively. Statistically significant differences in SUVmax and TBR between dual-phase SPECT/CT were observed (P < 0.001).

CONCLUSIONS

Delayed-phase SPECT/CT in SHPT is required because of the better image contrast.

Comparison of biochemical markers and technetium 99m methoxyisobutylisonitrile imaging in primary and secondary hyperparathyroidism

OBJECTIVE

To investigate the differences in biochemical marker levels and the extent of lesion visualization on technetium 99m methoxyisobutylisonitrile (^99mTc-MIBI) imaging between primary hyperparathyroidism (PHPT) and secondary hyperparathyroidism (SHPT).

METHODS

Nineteen patients with PHPT and 14 patients with SHPT were enrolled in the study, all of whom underwent routine ^99mTc-MIBI dual-phase planar imaging, single-photon emission computed tomography combined with computed tomography (SPECT/CT fusion) imaging, and serum biochemical and hormonal investigations prior to surgery. The target-to-non-target (T/NT) ratios were calculated based on images from the early and delayed phases of ^99mTc-MIBI planar imaging and also based on SPECT/CT fusion imaging. The volume of the parathyroid glands was measured following their excision.

RESULTS

A total of 62 parathyroid glands were removed: 14 parathyroid adenomas and five parathyroid carcinomas in PHPT patients; and 18 parathyroid adenomas, 17 parathyroid hyperplasia lesions, and eight instances of nodular hyperplasia with adenoma in SHPT patients. The median volume of the lesions in PHPT and SHPT was 1.69 cm³ and 0.52 cm³ respectively, and the difference between them was statistically significant (P = 0.001). The median T/NT ratios calculated at the early phase of ^99mTc-MIBI planar imaging, the delayed phase of ^99mTc-MIBI planar imaging, and the subsequent SPECT/CT fusion imaging were 1.51, 1.34, and 2.75, respectively, in PHPT, and 1.46, 1.30, and 1.38, in SHPT, respectively. The T/NT ratio difference between PHPT and SHPT on the SPECT/CT fusion imaging was statistically significant (P = 0.002). The histopathology subtypes of the lesions were associated with significant differences in two areas: the T/NT ratios on the SPECT/CT fusion imaging and the volume of the lesions (P=0.002, P<0.001).

CONCLUSION

The proportion of positive findings on ^99mTc-MIBI dual-phase planar imaging and the T/NT ratios of ^99mTc-MIBI SPECT/CT fusion imaging were higher in PHPT than in SHPT. The volume of parathyroid lesions in SHPT was smaller than in PHPT.

Large parathyroid adenomas: Potential mechanisms to reconcile adenoma size and disease phenotype

Parathyroid adenomas weighing more than 3.5 g are reported variously as "atypical", "large" or "giant" parathyroid adenomas. All such adenomas are rare variants accounting for no more than 1.5% of all parathyroid adenomas. Large parathyroid adenomas are often associated with more severe form of the disease, including osteitis fibrosa cystica (OFC) and share many biochemical, histological, and molecular features of both benign and malignant parathyroid neoplasms, and are considered a distinct clinical entity. However, the pathogenesis of oversized parathyroid adenomas and the often-associated skeletal phenotype remains unclear. We present 5 cases of primary hyperparathyroidism (PHPT) with OFC, an uncommon manifestation of contemporary PHPT, associated with larger parathyroid adenomas, seen in the Bone and Mineral Disorders Clinic of the Henry Ford Health in the last 30 years to illustrate the critical role of vitamin D nutrition in the pathogenesis of both the OFC and adenoma size. The estimated prevalence of OFC was very low 0.2%, 5 of the >3000 surgically confirmed cases of PHPT seen during this time. The mean ± SD values were: age: 36.8 ± 22.1 years (4 of the 5 <36years), serum calcium 11.6 ± 1.1 mg/dl, alkaline phosphatase 799 ± 487 IU/L, PTH 1440 ± 477 pg/ml, 25-hydroxyvitamin D 13.0 ± 8.9 ng/ml, 1,25-dihyroxyvitamin D 26.5 ± 13.7 pg/ml, urine calcium 562 ± 274 mg/day, and parathyroid adenoma weight 4.53 ± 2.2 g. Parathyroidectomy led to the resolution of both the biochemical indices and OFC in each patient without recurrence over >10 years of follow-up. Because OFC is a very rare in the West, but very common areas of endemic vitamin D deficiency, we also examined the relationship between vitamin D nutrition, as assessed by serum 25-hydroxyvitamin D level, and parathyroid adenoma weight as well as prevalence of OFC in two large secularly diverse cohorts of patients with PHPT (Detroit, USA and Chandigarh, India). Based on this relationship and the relative prevalence of OFC in these two large cohorts, we propose that vitamin D nutrition (and perhaps calcium nutrition) best explains both the adenoma size and prevalence of OFC.

Use of Publication Dynamics to Distinguish Cancer Genes and Bystander Genes

de Magalhães has shown recently that most human genes have several papers in PubMed mentioning cancer, leading the author to suggest that every gene is associated with cancer, a conclusion that contradicts the widely held view that cancer is driven by a limited number of cancer genes, whereas the majority of genes are just bystanders in carcinogenesis. We have analyzed PubMed to decide whether publication metrics supports the distinction of bystander genes and cancer genes. The dynamics of publications on known cancer genes followed a similar pattern: seminal discoveries triggered a burst of cancer-related publications that validated and expanded the discovery, resulting in a rise both in the number and proportion of cancer-related publications on that gene. The dynamics of publications on bystander genes was markedly different. Although there is a slow but continuous time-dependent rise in the proportion of papers mentioning cancer, this phenomenon just reflects the increasing publication bias that favors cancer research. Despite this bias, the proportion of cancer papers on bystander genes remains low. Here, we show that the distinctive publication dynamics of cancer genes and bystander genes may be used for the identification of cancer genes.

DNMT1-Mediated DNA Methylation Targets CDKN2B to Promote the Repair of Retinal Ganglion Cells in Streptozotocin-Induced Mongolian Gerbils during Diabetic Retinopathy

Objective

DNA methylation played a vital role in the progression of diabetic retinopathy. In this study, we aimed to explore the role of DNA cytosine-5-methyltransferase 1 (DNMT1) in the development of early diabetic retinopathy and its potential underlying mechanism.

Methods

Eight-week-old healthy Mongolian gerbils were used to establish type 1 diabetes using streptozotocin (STZ). Alteration of weight, fasting blood glucose, density of RGCs (Tuj1-labeled), and H&E-stained retinal cross sections were applied to evaluate the diabetic retinopathy mouse model. The global DNA methylation level of the retina at different time points after STZ injection was measured using the global methylation assay. Western blot was used to detect the protein expression of DNMT1, DNA methyltransferase 3A (DNMT3A), and 3B (DNMT3B). Quantitative reverse transcription-polymerase chain reactions (qRT-PCR) and western blot were used to determine the expression of CDKN2B. Cell proliferation and cell cycle were evaluated by the MTS assay and flow cytometry.

Results

STZ injection caused the increased global DNA methylation level, which reached a maximum at 6 weeks after injection. Moreover, STZ injection caused the damage of RGCs. At 6 weeks after STZ injection, the expression levels of DNMT1 and DNMT3B were significantly increased in the STZ group. DNMT1-induced DNA hypermethylation inhibited the expression of CDKN2B (a negative regulator of cell cycle). DNMT1-mediated DNA methylation facilitated RGC proliferation via regulating the expression of CDKN2B.

Conclusion

DNMT1-mediated DNA methylation played an important role in STZ-induced diabetic retinopathy via modulating CDKN2B expression.

Overview of the 2022 WHO Classification of Parathyroid Tumors

The 2022 WHO classification reflects increases in the knowledge of the underlying pathogenesis of parathyroid disease. In addition to the classic characteristic features of parathyroid neoplasms, subtleties in histologic features which may indicate an underlying genetic abnormality reflect increased understanding of the clinical manifestations, histologic, and genetic correlation in parathyroid disease. The importance of underlying genetic aberrancies is emphasized due to their significance to the care of the patient. Traditionally, the term "parathyroid hyperplasia" has been applied to multiglandular parathyroid disease; however, the concept of hyperplasia is generally no longer supported in the context of primary hyperparathyroidism since affected glands are usually composed of multiple "clonal" neoplastic proliferations. In light of these findings and management implications for patient care, the 2022 WHO classification endorses primary hyperparathyroidism-related multiglandular parathyroid disease (multiglandular multiple parathyroid adenomas) as a germline susceptibility-driven multiglandular parathyroid neoplasia. From such a perspective, pathologists can provide additional value to genetic triaging by recognizing morphological and immunohistochemical harbingers of MEN1, CDKN1B, MAX, and CDC73-related manifestations. In the current WHO classification, the term "parathyroid hyperplasia" is now used primarily in the setting of secondary hyperplasia which is most often caused by chronic renal failure. In addition to expansion in the histological features, including those that may be suggestive of an underlying genetic abnormality, there are additional nomenclature changes in the 2022 WHO classification reflecting increased understanding of the underlying pathogenesis of parathyroid disease. The new classification no longer endorses the use of "atypical parathyroid adenoma". This entity is now being replaced with the term of "atypical parathyroid tumor" to reflect a parathyroid neoplasm of uncertain malignant potential. The differential diagnoses of atypical parathyroid tumor are discussed along with the details of worrisome clinical and laboratory findings, and also features that define atypical histological and immunohistochemical findings to qualify for this diagnosis. The histological definition of parathyroid carcinoma still requires one of the following findings: (i) angioinvasion (vascular invasion) characterized by tumor invading through a vessel wall and associated thrombus, or intravascular tumor cells admixed with thrombus, (ii) lymphatic invasion, (iii) perineural (intraneural) invasion, (iv) local malignant invasion into adjacent anatomic structures, or (v) histologically/cytologically documented metastatic disease. In parathyroid carcinomas, the documentation of mitotic activity (e.g., mitoses per 10mm²) and Ki67 labeling index is recommended. Furthermore, the importance of complete submission of parathyroidectomy specimens for microscopic examination, and the crucial role of multiple levels along with ancillary biomarkers have expanded the diagnostic workup of atypical parathyroid tumors and parathyroid carcinoma to ensure accurate characterization of parathyroid neoplasms. The concept of parafibromin deficiency has been expanded upon and term "parafibromin deficient parathyroid neoplasm" is applied to a parathyroid neoplasm showing complete absence of nuclear parafibromin immunoreactivity. Nucleolar loss is considered as abnormal finding that requires further molecular testing to confirm its biological significance. The 2022 WHO classification emphasizes the role of molecular immunohistochemistry in parathyroid disease. By adopting a question-answer framework, this review highlights advances in knowledge of histological features, ancillary studies, and associated genetic findings that increase the understanding of the underlying pathogenesis of parathyroid disease that are now reflected in the updated classification and new entities in the 2022 WHO classification.

Aberrant Epigenetic Alteration of PAX1 Expression Contributes to Parathyroid Tumorigenesis

CONTEXT

Primary hyperparathyroidism (PHPT) results from the hypersecretion of parathyroid hormone from parathyroid tumors. A transcription factor, namely Paired box1 (PAX1), is active in parathyroid gland development.

OBJECTIVE

We aimed to study potential epigenetic-mediated mechanism of PAX1 gene in sporadic parathyroid adenomas.

METHODS

In parathyroid adenomas tissues, we analyzed the DNA methylation via bisulfite-specific polymerase chain reaction (BSP) and histone modifications via chromatin immunoprecipitation in regulating the differential expression of PAX1.

RESULTS

The results showed that mRNA and protein expression of PAX1 was significantly reduced in parathyroid adenomas. Bisulfite sequencing demonstrated hypermethylation in the promoter region of PAX1 (35%; 14/40) and lower levels of histone 3 lysine 9 acetylation (H3K9ac) were observed on the promoter region of PAX1 (6-fold; P < .004) in parathyroid adenomas. Furthermore, upon treatment with a pharmacologic inhibitor, namely 5'aza-2 deoxycytidine, in rat parathyroid continuous cells, we found re-expression of PAX1 gene.

CONCLUSION

Our study not only reveals expression of PAX1 is epigenetically deregulated but also paves a way for clinical and therapeutic implications in patients with PHPT.

Association of Famine Exposure on the Changing Clinical Phenotypes of Primary Hyperparathyroidism in 20 years

BACKGROUND & AIMS

Primary hyperparathyroidism(PHPT) has been evolving into a milder asymptomatic disease. No study has assessed the association between famine exposure and such a shift. We aim to explore the effects of China's Great Famine exposure on the changing pattern of PHPT phenotypes.

METHODS

750 PHPT patients diagnosed from 2000 to 2019 were studied. The clinical presentations were compared between them in recent 10 years (2010-2019) and previous 10 years (2000-2009). Participants were then categorized into fetal, childhood, adolescent, adult exposure, and unexposed groups. Logistic regression was used to estimate the odds ratios (ORs) and confidence intervals (CIs) of famine exposure as factors contributing to the changes in the clinical presentations of PHPT.

RESULTS

Serum levels of PTH, albumin-corrected Ca, tumor size, eGFR, BMDs (all P<0.001), and clinical symptoms became milder in recent 10 years. Famine exposure (72.6% vs 58.4%, P<0.001), especially the adult exposure (18.8% vs 4.1%, P<0.001)was significant less in recent 10 years. The ORs (95%CIs) of having upper 3^rd tertile PTH were 2.79(1.34,5.8), 2.07(1.04,4.11), 3.10(1.15,8.38) and 8.85(2.56,30.56) for patients with fetal, childhood, adolescent and adult famine exposure, respectively. The ORs (95%CIs) of upper 3^rd tertile albumin-corrected Ca and upper 3^rd tertile of tumor size was 4.78(1.39, 16.38) and 4.07(1.12,14.84) for participants with adult famine exposure, respectively. All these associations were independent of age, sex, disease duration and other confounders.

CONCLUSIONS

The clinical manifestations of PHPT in China continue to be milder. Exposure to famine is associated with PHPT. Less famine exposure might be responsible for the mile form of PHPT in recent years.

GCM2 Silencing in Parathyroid Adenoma Is Associated With Promoter Hypermethylation and Gain of Methylation on Histone 3

CONTEXT

Glial cells missing 2 (GCM2), a zinc finger-transcription factor, is essentially required for the development of the parathyroid glands.

OBJECTIVE

We sought to identify whether the epigenetic alterations in GCM2 transcription are involved in the pathogenesis of sporadic parathyroid adenoma. In addition, we examined the association between promoter methylation and histone modifications with disease indices.

METHODS

Messenger RNA (mRNA) and protein expression of GCM2 were analyzed by reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR) and immunohistochemistry in 33 adenomatous and 10 control parathyroid tissues. DNA methylation and histone methylation/acetylation of the GCM2 promoter were measured by bisulfite sequencing and chromatin immunoprecipitation-qPCR. Additionally, we investigated the role of epigenetic modifications on GCM2 and DNA methyltransferase 1 (DNMT1) expression in parathyroid (PTH)-C1 cells by treating with 5-aza-2'-deoxycytidine (DAC) and BRD4770 and assessed for GCM2 mRNA and DNMT1 protein levels.

RESULTS

mRNA and protein expression of GCM2 were lower in sporadic adenomatous than in control parathyroid tissues. This reduction correlated with hypermethylation (P < .001) and higher H3K9me3 levels in the GCM2 promoter (P < .04) in adenomas. In PTH-C1 cells, DAC treatment resulted in increased GCM2 transcription and decreased DNMT1 protein expression, while cells treated with the BRD4770 showed reduced H3K9me3 levels but a nonsignificant change in GCM2 transcription.

CONCLUSION

These findings suggest the concurrent association of promoter hypermethylation and higher H3K9me3 with the repression of GCM2 expression in parathyroid adenomas. Treatment with DAC restored GCM2 expression in PTH-C1 cells. Our results showed a possible epigenetic landscape in the tumorigenesis of parathyroid adenoma and also that DAC may be a promising avenue of research for parathyroid adenoma therapeutics.

Differences in Primary Hyperparathyroidism Between Pre- and Postmenopausal Women in India

OBJECTIVE

Primary hyperparathyroidism (PHPT) is a common endocrine disorder in women which becomes more prevalent after menopause. In this study, we compared the demographic, clinical, and biochemical variables between premenopausal (pre-M) and postmenopausal (post-M) women with PHPT.

METHODS

A retrospective analysis (from 2005 to 2019) of enrolled women PHPT patients from an online Indian PHPT registry.

RESULTS

Of the women with PHPT, 232 and 122 were pre-M and post-M, respectively. The number of post-M PHPT cases registered had a 3.3-fold increase in 2015-2019 from 2005-2009 compared with only a 2.5-fold increase in pre-M cases in the same duration. The majority were symptomatic (90%), although pre-M had a higher proportion of symptomatic than post-M (92% vs 85%; P = .04). Pre-M women showed more prevalence of osteitis fibrosa cystica than post-M women (28% vs 13%; P = .03), although hypertension and gallstone disease were seen more frequently in post-M PHPT women. Pre-M women had a significantly higher median PTH (403 vs 246 pg/mL; P = .02) and median alkaline phosphatase (202 vs 145 pg/mL; P = .02) than post-M women, and vitamin D deficiency was more common in pre-M women (58% vs 45%; P = .03). Gland localization, tumor weight, and disease cure rates did not differ according to menopausal status.

CONCLUSION

PHPT was more prevalent in pre-M women, although the number of post-M cases had significantly increased in the last 10 years. Pre-M women had generally more severe clinical and biochemical variables than post-M PHPT women.

Genomics and Epigenomics in Parathyroid Neoplasia: from Bench to Surgical Pathology Practice

The majority of parathyroid disease encountered in routine practice is due to single parathyroid adenoma, of which the majority arise as sporadic tumors. This is usually a straightforward diagnosis in endocrine pathology when in the appropriate clinical setting, although subsets of cases will exhibit atypical histological features that may warrant additional immunohistochemical and genetic analyses to estimate the malignant potential. Parathyroid carcinomas on the other hand, are bona fide malignant tumors characterized by their unequivocal invasion demonstrated through routine histology or metastasis. The ultimate endpoint for any molecular marker discovered through laboratory investigations is to be introduced in clinical routine practice and guide the surgical pathologist in terms of diagnostics and prognostication. For parathyroid tumors, the two main diagnostic challenges include the distinction between parathyroid adenoma and parathyroid carcinoma, as well as the pinpointing of hereditable disease for familial screening purposes. While numerous markers on genetic, epigenetic, and protein levels have been proposed as discriminative in these aspects, this review aims to condense the scientific coverage of these enigmatic topics and to propose a focused surgical pathology approach to the subject.

Molecular analysis of cyclin D1 modulators PRKN and FBX4 as candidate tumor suppressors in sporadic parathyroid adenomas

OBJECTIVE

Primary hyperparathyroidism is most often caused by a sporadic single-gland parathyroid adenoma (PTA), a tumor type for which cyclin D1 is the only known and experimentally validated oncoprotein. However, the molecular origins of its frequent overexpression have remained mostly elusive. In this study, we explored a potential tumorigenic mechanism that could increase cyclin D1 stability through a defect in molecules responsible for its degradation.

METHODS

We examined two tumor suppressor genes known to modulate cyclin D1 ubiquitination, PRKN and FBXO4 (FBX4), for evidence of classic two-hit tumor suppressor inactivation within a cohort of 82 PTA cases. We examined the cohort for intragenic inactivating and splice site mutations by Sanger sequencing and for locus-associated loss of heterozygosity (LOH) by microsatellite analysis.

RESULTS

We identified no evidence of bi-allelic tumor suppressor inactivation of PRKN or FBXO4 via inactivating mutation or splice site perturbation, neither in combination with nor independent of LOH. Among the 82 cases, we encountered previously documented benign single nucleotide polymorphisms (SNPs) in 35 tumors at frequencies similar to those reported in the germlines of the general population. Eight cases exhibited intragenic LOH at the PRKN locus, in some cases extending to cover at least an additional 1.7 Mb of chromosome 6q25-26. FBXO4 was not affected by LOH.

CONCLUSION

The absence of evidence for specific bi-allelic inactivation in PRKN and FBXO4 in this sizeable cohort suggests that these genes only rarely, if ever, serve as classic driver tumor suppressors responsible for the growth of PTAs.

Integrated Whole-Exome and Transcriptome Sequencing of Sporadic Parathyroid Adenoma

PURPOSE

Hyperparathyroidism is the third most common endocrine disease. Parathyroid adenoma (PA) accounts for approximately 85% of cases of primary hyperparathyroidism, but the molecular mechanism is not fully understood. Herein, we aimed to investigate the genetic and transcriptomic profiles of sporadic PA.

METHODS

Whole-exome sequencing (WES) and transcriptome sequencing (RNA-seq) of 41 patients with PA and RNA-seq of 5 normal parathyroid tissues were performed. Gene mutations and characterized expression changes were identified. To elucidate the molecular mechanism underlying PA, unsupervised consensus clustering of RNA-seq data was performed. The correlations between the sequencing data and clinicopathological features of these patients were analyzed.

RESULTS

Previously reported PA driver gene mutations, such as MEN1 (9/41), mTOR (4/41), ZFX (3/41), CASR (3/41), EZH2 (2/41) and FAT1 (2/41), were also identified in our cohort. Furthermore, somatic mutation of EZH1, which had not been reported in PA, was found in 4 samples. RNA-seq showed that the expression levels of 84 genes were upregulated and 646 were downregulated in PA samples compared with normal samples. Unsupervised clustering analysis of RNA-seq data clustered these patients into 10 subgroups related to mutation or abnormal expression of a group of potential pathogenic genes.

CONCLUSION

MEN1, EZH2, CASR, EZH1, ZFX, mTOR and FAT1 mutations in PA were revealed. According to the RNA-seq data clustering analysis, cyclin D1, β-catenin, VDR, CASR and GCM2 may be important factors contributing to the PA gene expression profile.

Reduced Calcium Sensing Receptor (CaSR) Expression Is Epigenetically Deregulated in Parathyroid Adenomas

AIM

Reduced calcium sensing receptor (CaSR) expression has been implicated in parathyroid tumorigenesis, but the underlying mechanism remains elusive. Accordingly, we aimed to explore the epigenetic changes (DNA methylation and histone modifications) involved in CaSR regulation in sporadic parathyroid adenomas and correlate epigenetic state with disease indices.

EXPERIMENTAL DESIGN

Forty sporadic parathyroid adenomas and 10 control parathyroid tissues were studied. Real-time quantitative PCR (qPCR) for mRNA and immunohistochemistry for protein expression of CaSR were performed. The methylation status of the CaSR promoter 2 was determined by bisulphite sequencing analysis of sodium bisulphite-converted DNA. To determine the role of histone modifications in the CaSR regulation, chromatin immunoprecipitation-qPCR assay was performed.

RESULTS

Real-time qPCR revealed reduced CaSR mRNA expression with a fold reduction of 0.12 (P < 0.0001) in parathyroid adenomas. Immunohistochemistry revealed reduced protein expression of CaSR in 90% (36/40) of adenomas. The promoter 2 region of CaSR displayed significant hypermethylation in 45% (18/40) of the adenomas compared with the controls (6.7%; 1 of 10) (P < 0.002). Bisulphite sequencing analysis revealed maximum methylated CpG at glial cell missing 2 binding site on the CaSR promoter 2 compared to other CpG sites. The methylation status of CaSR correlated directly with plasma intact parathyroid hormone levels in patients with parathyroid adenoma. With chromatin immunoprecipitation-qPCR analysis, H3K9me3 levels showed increased enrichment by 10-fold in adenomas and correlated with CaSR-mRNA expression (r = 0.61; P < 0.003). Treatment with 5-aza-2'deoxycytidine restored the expression of CaSR in a parathyroid cell line.

CONCLUSION

Our data suggest that hypermethylation and increased H3K9me3 of the CaSR promoter 2 are involved in silencing CaSR expression in sporadic parathyroid adenoma.

Identification by TCGA database search of five genes that are aberrantly expressed and involved in hepatocellular carcinoma potentially via DNA methylation changes

BACKGROUND

Various treatments for hepatocellular carcinoma (HCC) are utilized in clinical practice; however, the prognosis is still poor on account of high recurrence rates. DNA methylation levels of CpG islands around promoters (promoter CpGis) inversely regulate gene expression and closely involved in carcinogenesis. As a new strategy, several chemicals globally inhibiting DNA methylation have been developed aiming at reducing DNA methylation levels and maintaining the expression of tumor suppressor genes. On the other hand, since these drugs nonspecifically modify DNA methylation, they can cause serious adverse effects. In order to ameliorate the methods by targeting specific CpGs, information of cancer-related genes that are regulated by DNA methylation is required.

METHODS

We searched candidate genes whose expressions were regulated by DNA methylation of promoter CpGi and which are involved in HCC cases. To do so, we first identified genes whose expression were changed in HCC by comparing gene expressions of 371 HCC tissues and 41 non-tumor tissues using the Cancer Genome Atlas (TCGA) database. The genes were further selected for poor prognosis by log-rank test of Kaplan-Meier plot and for cancer relevance by Pubmed search. Expression profiles of upregulated genes in HCC tissues were assessed by Gene Ontology (GO) analysis. Finally, using DNA methylation data of TCGA database, we selected genes whose promoter DNA methylation levels were inversely correlated with gene expression.

RESULTS

We found 115 genes which were significantly up- or downregulated in HCC tissues and were associated with poor prognosis and cancer relevance. The upregulated genes were significantly enriched in cell division, cell cycle, and cell proliferation. Among the upregulated genes in HCC, we identified hypomethylation of CpGis around promoters of FANCB, KIF15, KIF4A, ERCC6L, and UBE2C. In addition, TCGA data showed that the tumor suppressor gene P16 is unexpectedly overexpressed in many types of cancers.

CONCLUSIONS

We identified five candidate genes whose expressions were regulated by DNA methylation of promoter CpGi and associate with cancer cases and poor prognosis in HCC. Modification of site-specific DNA methylation of these genes enables a different approach for HCC treatment with higher selectivity and lower adverse effects.

Dysregulated mitogen-activated protein kinase pathway mediated cell cycle disruption in sporadic parathyroid tumors

OBJECTIVES

The study was designed to evaluate expression profiling of mitogen-activated protein kinase (MAPK) signalling pathway genes in sporadic parathyroid adenoma.

METHODS

Expression of MAPK signalling pathway genes including activated transcription factors and cell cycle regulatory genes was analysed by real-time PCR- based array in parathyroid adenoma (N = 20) and normal parathyroid tissue (N = 4).

RESULTS

MAPK signalling pathway as studied by PCR array revealed that a total of 22 genes were differentially expressed (≥ twofold change, p ≤ 0.05) in parathyroid adenoma. Up-regulated genes were ARAF, MAPK12, CREBBP, MYC, HSPB1, HRAS, CDK4, CCND1, and E2F1, and down-regulated genes were MAP4K1, DLK1, MAP3K4, MAPK10, MAPK8, ATF2, SMAD4, MEF2C, LAMTOR3, FOS, CDKN2A CDKN2B, and RB1. The present study revealed that ERK1/2 signalling pathway with up-regulation of HRAS, ARAF, and MEK1 genes and up-regulation of positive regulators of cell cycle (CCND1, CDK4, and E2F1) and down-regulation negative regulators of cell cycle (CDKN2A, CDKN2B, and RB1) made highly dysregulated MAPK signalling pathway in parathyroid adenoma. Expression of CDK4 was positively associated with plasma PTH level (r = 0.60, p = 0.04) and tumor weight (r = 0.80, p = 0.02) of the adenoma patients, respectively. Expression of CDKN2A was correlated negatively with PTH level (r = - 0.52, p = 0.04) of the adenoma patients.

CONCLUSION

The current study revealed that ERK pathway and associated cell cycle regulator genes are dysregulated in sporadic parathyroid adenoma.

miR-639 Expression Is Silenced by DNMT3A-Mediated Hypermethylation and Functions as a Tumor Suppressor in Liver Cancer Cells

Emerging evidence has indicated that abnormal methylation of DNA contributes to hepatocarcinogenesis. However, the regulatory mechanisms are not well known. Here, we revealed that microRNA-639 (miR-639) expression is downregulated in liver cancer tissues and cells. The repression of miR-639 expression was attributed to hypermethylation in its promoter region, and DNA methyltransferase (DNMT3A) was found to mediate this hypermethylation. Repression of miR-639 expression promoted cell growth and migration/invasion in vitro and the growth of tumors in xenograft mouse models. Furthermore, miR-639 bound to the 3' UTR of both MYST2 and ZEB1 and suppressed their expression. MYST2 promoted the growth of liver cancer cells and ZEB1 facilitated the migration/invasion of liver cancer cells. Ectopic expression of MYST2 and ZEB1 counteracted the repression of malignancy induced by miR-639, which coincided with the reciprocal correlation between miR-639 and MYST2 and ZEB1 expression in clinical hepatocellular carcinoma (HCC) tissues. Thus, DNMT3A-mediated hypermethylation suppressed miR-639 expression, derepressing the expression of MSYT2 and ZEB1, which promoted tumorigenesis of liver cancer. These findings may shed light on the mechanism of abnormal expression of miRNAs involved in the malignancy of liver cancer and provide new biomarkers for liver cancer.

[Correlation between methylation level of CDKN2A and CDKN2B genes and aging in healthy individuals]

OBJECTIVE

To analyze the relationship between CDKN2A and CDKN2B gene methylation with aging in the general population.

METHODS

We collected peripheral blood samples from 284 male and 246 female healthy subjects for detection of methylation levels of CDKN2A and CDKN2B genes using quantitative methylation-specific PCR (qMSP). The relationship between the methylation levels of CDKN2A and CDKN2B genes and aging was analyzed using Spearman or Pearson correlation test.

RESULTS

We found a significant positive correlation between the methylation levels of the two genes in these subjects (P &lt; 0.05). In the overall population as well in the female subjects, CDKN2A methylation was found to be inversely correlated with age (P &lt; 0.05). The methylation levels of CDKN2A and CDKN2B genes were inversely correlated with TG, ApoE, Lp(a) and AST in the overall population (P &lt; 0.05). In both the female and male subjects, the methylation levels of the two genes were inversely correlated with Lp(a) (P &lt; 0.05). In the male subjects, CDKN2A methylation was inversely correlated with AST (P &lt; 0.05), while CDKN2B methylation was inversely correlated with HDL and ApoE (P &lt; 0.05). In the female subjects, CDKN2A methylation was positively correlated with LDL and inversely correlated with ApoE and AST (P &lt; 0.05).

CONCLUSIONS

The methylation levels of CDKN2A and CDKN2B are closely related to age and the levels of multiple proteins in healthy subjects.

Quantitative proteomics analysis of sporadic parathyroid adenoma tissue samples

OBJECTIVE

Molecular pathogenesis of parathyroid tumors is incompletely understood. Identification of novel molecules and understanding their role in parathyroid tumorigenesis by proteomics approach would be informative with potential clinical implications.

METHOD

Adenomatous (n = 5) and normal (n = 2) parathyroid tissue lysates were analyzed for protein profile by LC-MS/MS method and the proteins were classified using bioinformatics tools such as PANTHER and toppfun functional enrichment tool. Identified proteins were further validated by western blotting and qRT-PCR (n = 20).

RESULT

Comparative proteomics analysis revealed that a total of 206 proteins (74 upregulated and 132 downregulated) were differentially expressed (≥ twofold change) in adenomas. Bioinformatics analysis revealed that 48 proteins were associated with plasma membrane, 49 with macromolecular complex, 39 were cytoplasm, 38 were organelle related, 21 were cell junction and 10 were extracellular proteins. These proteins belonged to a diverse protein family such as enzymes, transcription factors, cell signalling, cell adhesion, cytoskeleton proteins, receptors, and calcium-binding proteins. The major biological processes predicted for the proteins were a cellular, metabolic and developmental process, cellular localization, and biological regulation. The differentially expressed proteins were found to be associated with MAPK, phospholipase C (PLC) and phosphatidylinositol (PI) signalling pathways, and with chromatin organization. Western blot and qRT-PCR analysis of three proteins (DNAJC2, ACO2, and PRDX2) validated the LC-MS/MS findings.

CONCLUSION

This exploratory study demonstrates the feasibility of proteomics approach in finding the dysregulated proteins in benign parathyroid adenomas, and our preliminary results suggest that MAPK, PLC and PI signalling pathways and chromatin organization are involved in parathyroid tumorigenesis.

DNA Methylation Regulates Corneal Epithelial Wound Healing by Targeting miR-200a and CDKN2B

Purpose

DNA methylation is a key epigenetic modification involved in various biological processes and diseases. Corneal epithelial wound healing (CEWH) is essential for restoring corneal integrity and transparency after injury. However, the role of DNA methylation in CEWH remains elusive. Here, we investigate the function and underlying mechanism of DNA methylation in regulating CEWH.

Methods

Dot blots and global methylation assays determined DNA methylation levels during CEWH. Quantitative RT-PCR and Western blot analysis examined the expression of DNA methyltransferases (DNMTs), cyclin-dependent kinase inhibitor 2B (CDKN2B), and miR-200a during CEWH, respectively. MTS assays and flow cytometry were used to analyze human corneal epithelial cell (HCEC) proliferation and cell cycle, respectively. The in vitro scratch wound assay assessed HCEC migration and an in vivo murine corneal epithelial debridement model evaluated wound healing. Using bisulfite sequencing PCR, we determined the DNA methylation status of the candidate genes. Transfection of miR-200a mimic or inhibitor assessed the function of miR-200a in HCECs. Rescue experiments were performed to clarify the correlation between DNMT1 and miR-200a/CDKN2B during CEWH.

Results

DNMT1 and DNMT3B expression was significantly upregulated during CEWH, resulting in a significant global DNA hypermethylation. DNMT1 downregulation dramatically delayed CEWH in vivo, and suppressed HCEC proliferation and migration. MiR-200a inhibited HCEC migration. Furthermore, miR-200a and CDKN2B were identified as molecular targets of DNA methylation and as having a causal connection with DNMT1.

Conclusions

DNMT1-mediated DNA hypermethylation can enhance the process of CEWH by directly targeting miR-200a and CDKN2B. This insight pinpoints novel potential drug targets for promoting CEWH.

A Role for Circular Non-Coding RNAs in the Pathogenesis of Sporadic Parathyroid Adenomas and the Impact of Gender-Specific Epigenetic Regulation

Epigenetic changes, including altered small non-coding RNAs, appear to be implicated in the pathogenesis of sporadic parathyroid adenomas (PAs). In this study, we investigated the circular RNAs (circRNAs) expression profile in sporadic PAs. Sixteen tissue samples of sporadic PAs, and four samples of normal parathyroid tissue (NPT) were investigated. Sample preparation and microarray hybridization were performed based on the Arraystar’s standard protocols, and circRNAs sequences were predicted by bioinformatics tools. We identified 35 circRNAs that were differentially expressed in sporadic PAs compared to NPT; 22 were upregulated, and 13 were downregulated, according to the pre-defined thresholds of fold-change > 2.0 and p< 0.05. In the subgroup analysis of PAs from male patients (n = 7) compared to PAs from female patients (n = 9), we also find a different expression profile. In particular, 19 circRNAs were significantly upregulated, and four circRNAs were significantly downregulated in male patients, compared to female counterparts. We show here for the first time a differential circRNA expression pattern in sporadic PAs compared to NPT, and a different expression profile in PA samples from male compared to female patients, suggesting an epigenetic role in the PA pathogenesis, and also an effect of gender in the epigenetic regulation of PAs.