Parafibromin expression is an independent prognostic factor for colorectal carcinomas

Phenotypic Profiling and Molecular Mechanisms in Hyperparathyroidism-jaw Tumor Syndrome

CONTEXT

Hyperparathyroidism-jaw tumor (HPT-JT) syndrome is a heritable form of primary hyperparathyroidism caused by germline inactivating mutations in CDC73 encoding parafibromin and is associated with an increased risk of parathyroid cancer. There is little evidence to guide the management of patients with the disease.

OBJECTIVE

(1) Characterize the natural history of HPT-JT, (2) correlate genotype and histology of parathyroid tumors with parafibromin immunostaining, (3) understand molecular changes downstream to CDC73 loss.

DESIGN

Retrospective study of patients with HPT-JT syndrome (genetically confirmed or affected first-degree relatives). Independent review of uterine tumor from 2 patients and staining for parafibromin on parathyroid tumors from 19 patients (13 adenomas, 6 carcinomas) was performed. RNA-sequencing was performed in 21 parathyroid samples (8 HPT-JT-related adenomas, 6 HPT-JT-related carcinomas, and 7 sporadic carcinomas with wild-type CDC73).

RESULTS

We identified 68 patients from 29 kindreds with HPT-JT with median age at last follow-up of 39 [interquartile range, 29-53] years. A total of 55/68 (81%) developed primary hyperparathyroidism; 17/55 (31%) had parathyroid carcinoma. Twelve of 32 (38%) females developed uterine tumors. Of the 11 patients who had surgical resection for uterine tumors, 12/24 (50%) tumors were rare mixed epithelial mesenchymal polypoid lesions. Four of 68 patients (6%) developed solid kidney tumors; 3/4 had a CDC73 variant at p.M1 residue. Parafibromin staining of parathyroid tumors did not correlate with tumor histology or genotype. RNA-sequencing showed a significant association of HPT-JT-related parathyroid tumors with transmembrane receptor protein tyrosine kinase signaling pathway, mesodermal commitment pathway, and cell-cell adhesion.

CONCLUSIONS

Multiple, recurrent atypical adenomyomatous uterine polyps appear to be enriched in women with HPT-JT and appear characteristic of the disease. Patients with CDC73 variants at p.M1 residue appear predisposed to kidney tumors.

CLINICAL TRIAL NUMBER

NCT04969926.

WNT5A: a double-edged sword in colorectal cancer progression

The Wnt signaling pathway is known to play a crucial role in cancer, and WNT5A is a member of this pathway that binds to the Frizzled (FZD) and Receptor Tyrosine Kinase-Like Orphan Receptor (ROR) family members to activate non-canonical Wnt signaling pathways. The WNT5A pathway is involved in various cellular processes, such as proliferation, differentiation, migration, adhesion, and polarization. In the case of colorectal cancer (CRC), abnormal activation or inhibition of WNT5A signaling can lead to both oncogenic and antitumor effects. Moreover, WNT5A is associated with inflammation, metastasis, and altered metabolism in cancer cells. This article aims to discuss the molecular mechanisms and dual roles of WNT5A in CRC.

The roles of the tumor suppressor parafibromin in cancer

In this review, we discuss parafibromin protein, which is encoded by CDC73. A mutation in this gene causes hyperparathyroidism-jaw tumor (HPT-JT) syndrome, an autosomal dominant disease. CDC73 is transcriptionally downregulated by the Wilms’ tumor suppressor gene WT1 and translationally targeted by miR-182-3p and miR-155. In the nucleus, parafibromin binds to RNA polymerase II and PAF1 complex for transcription. Parafibromin transcriptionally increases the expression of c-Myc, decreases CPEB1 expression by interacting with H3M4, and reduces cyclin D1 expression by binding to H3K9. The RNF20/RNF40/parafibromin complex induces monoubiquitination of H2B-K120, and SHP2-mediated dephosphorylation of parafibromin promotes the parafibromin/β-catenin interaction and induces the expression of Wnt target genes, which is blocked by PTK6-medidated phosphorylation. Parafibromin physically associates with the CPSF and CstF complexes that are essential for INTS6 mRNA maturation. In the cytosol, parafibromin binds to hSki8 and eEF1Bγ for the destabilization of p53 mRNA, to JAK1/2-STAT1 for STAT1 phosphorylation, and to actinin-2/3 to bundle/cross-link actin filaments. Mice with CDC73 knockout in the parathyroid develop parathyroid and uterine tumors and are used as a model for HPT-JT syndrome. Conditional deletion of CDC73 in mesenchymal progenitors results in embryos with agenesis of the heart and liver while its abrogation in mature osteoblasts and osteocytes increases cortical and trabecular bone. Heterozygous germline mutations in CDC73 are associated with parathyroid carcinogenesis. The rates of CDC73 mutation and parafibromin loss decrease from parathyroid adenoma to atypical adenoma to carcinoma. In addition, down-regulated parafibromin is closely linked to the tumorigenesis, subsequent progression, or poor prognosis of head and neck, gastric, lung, colorectal, and ovarian cancers, and its overexpression might reverse the aggressiveness of these cancer cells. Therefore, parafibromin might be useful as a biological marker of malignancies and a target for their gene therapy.

Parafibromin Is Highly Expressed in Hepatocellular Carcinoma and Its Expression Correlates with Poor Prognosis

Hepatocellular carcinoma (HCC) is the second leading cause of cancer-related death worldwide. Much progress has been made regarding the understanding of hepatocarcinogenesis, yet the long-term survival rate of HCC patients remains poor. Recent efforts have shown parafibromin has a pathologic role in many human cancers, but little is known about the effects of parafibromin in HCC. This study aimed to investigate the pattern of parafibromin expression and its clinicopathologic significance in human HCC. Immunohistochemical analysis of HCC and matched non-tumor liver tissues from 50 HCC patients showed that the nuclear expression of parafibromin was higher in HCC tissues (50/50 cases) than in non-tumor liver tissues (17/50 cases). Moreover, elevated parafibromin expression was found to be significantly correlated with the presence of microvascular invasion (p = 0.017), hepatitis virus infection-induced occurrence (p = 0.005), and poorer tumor differentiation (Edmondson-Steiner grade; p = 0.000). Kaplan-Meier analysis showed that HCC patients with elevated parafibromin expression had poorer recurrence-free (p = 0.014, log-rank test = 6.079) and overall survival (p = 0.036, log-rank test = 4.414). These findings indicate parafibromin may be related to the pathogenesis of HCC and a potential prognostic marker for HCC patients after hepatectomy.

WNT5a in Colorectal Cancer: Research Progress and Challenges

Despite the clinical development of new adjuvant and neoadjuvant chemotherapy drugs, colorectal cancer is still one of the leading causes of cancer-related death in human beings. WNT5a, an autocrine and paracrine β-catenin independent ligand, has been shown to induce tumor inhibition and carcinogenic signals, depending on the type of cancer. In patients with colorectal cancer, WNT5a triggers a variety of downstream signaling pathways, which mainly affect the migration and invasion of tumor cells. This article reviews the mechanism and therapeutic potential of WNT5a in colorectal cancer. In short, an in-depth understanding of the role of WNT5a in colorectal cancer is very helpful to better deal with this disease.

Prognostic role of parafibromin staining and CDC73 mutation in patients with parathyroid carcinoma: A systematic review and meta-analysis based on individual patient data

BACKGROUND AND OBJECTIVE

Parathyroid carcinoma (PC) is a rare malignant neoplasm with a relatively poor prognosis. The loss of parafibromin expression or the presence of CDC73 mutation has been found to be remarkably associated with malignancy in parathyroid tumours. However, the prognostic role of them in PC has not yet been shown due to sampling limitations. We conducted a systematic review and meta-analysis based on individual patient data to clarify the performance of parafibromin immunohistochemical staining and CDC73 gene sequencing in predicting outcomes for patients PC.

METHODS

Published studies from PubMed/MEDLINE, EMBASE, Cochrane and Scopus Databases were searched using the terms 'parafibromin', 'CDC73', 'HRPT2' and 'parathyroid' to identify eligible studies. From the included studies, the survival data of patients with PC were extracted, and a Cox proportional hazards model was used to assess hazard ratio (HR) for disease-free survival (DFS) and overall survival (OS).

RESULTS

A total of 193 patients from 9 studies were included in this survival analysis. Negative immunohistochemical staining of parafibromin was shown to be a risk factor for recurrence/metastasis (HR 2.73, P = .002) and death (HR 2.54, P = .004). Patient age ≥ 50 years was significantly related to lower OS (HR 2.37, P = .004) but not to DFS. CDC73 mutation was not statistically related to DFS or OS.

CONCLUSIONS

Negative parafibromin staining indicated a higher risk of recurrence/metastasis and mortality. The immunohistochemical staining of parafibromin seems to be more promising in predicting outcomes for patients with PC than the sequencing of CDC73.

Inhibition of microRNA-21-3p suppresses proliferation as well as invasion and induces apoptosis by targeting RNA-binding protein with multiple splicing through Smad4/extra cellular signal-regulated protein kinase signalling pathway in human colorectal cancer HCT116 cells

MicroRNA-21-3p (miR-21-3p), the passenger strand of pre-mir-21, has been found to be high-expressing in various cancers and to be associated with tumour malignancy, which is proposed as a novel focus in malignant tumours. Colorectal cancer (CRC), currently known as one of the most prevalent malignancy, is a leading cause of cancer death. This study aimed to investigate the key role of miR-21-3p in CRC by inhibiting its expression using transfection with miR-21-3p inhibitors into human CRC HCT116 cells. Results showed that the expression of miR-21-3p was higher than other CRC cells used in the study including Lovo, HT29, Colo320 and SW480 cells, inhibition of which suppressed the proliferation and induced cell cycle arrest in HCT116 cells. Besides, transfection with miR-21-3p inhibitors also attenuated cell migration and invasion, and induced apoptosis as well. Moreover, luciferase assay confirmed RBPMS as a direct target of miR-21-3p in HCT116 cells. Further, miR-21-3p inhibitors increased the nuclear accumulation of Smad4 and reduced phosphorylation of ERK. Interestingly, we found that silence of RBPMS using RNA interference (siRNA) not only elevated the cell viability but also increased the phosphorylation of ERK and reversed the nuclear accumulation of Smad4 induced by miR-21-3p inhibitors in HCT116 cells. Data suggest that inhibition of miR-21-3p suppresses cell proliferation, invasion as well as migration and induces apoptosis by directly targeting RBPMS through Smad4/ERK signalling pathway in HCT116 cells. Our study demonstrates miR-21-3p as a potent target for suppressing tumour progression of CRC which may have implications in CRC therapy in the future.

The clinicopathological and prognostic significances of CDC73 expression in cancers: a bioinformatics analysis

CDC73 interacts with human PAF1 complex, histone methyltransferase complex and RNA polymerase II for transcription elongation and 3’ end processing. Its down-regulated expression was immunohistochemically detected in gastric, colorectal, ovarian and head and neck cancers, and positively correlated with aggressive behaviors and unfavorable prognosis of malignancies. We performed a bioinformatics analysis by using Oncomine, TCGA and KM plotter databases. It was found that CDC73 mRNA was overexpressed in gastric, lung, breast and ovarian cancers, even stratified by histological subtypes (p<0.05). CDC73 mRNA expression was stronger in gastric intestinal- than diffuse-type carcinomas (p<0.05), and positively correlated with distant metastasis and TNM staging of lung cancer (p<0.05). CDC73 mRNA expression was positively related to both overall and progression-free survival rates of the patients with gastric cancer, even stratified by gender, lymph node involvement, or treatment (p<0.05), while versa for breast cancer (p<0.05). The prognostic significance of CDC73 mRNA was dependent on the datasets and pathological grouping in lung and ovarian cancers. These findings indicated the CDC73 mRNA overexpression was positively linked to carcinogenesis. It is cautious to employ CDC73 mRNA to evaluate the clinicopathological behaviors and prognosis of cancers.

The in vitro and vivo effects of nuclear and cytosolic parafibromin expression on the aggressive phenotypes of colorectal cancer cells: a search of potential gene therapy target

Down-regulated parafibromin is positively linked to the pathogenesis of parathyroid, lung, breast, ovarian, gastric and colorectal cancers. Here, we found that wild-type (WT) parafibromin overexpression suppressed proliferation, tumor growth, induced cell cycle arrest and apoptosis in colorectal cancer cells (p<0.05), but it was the converse for mutant-type (MT, mutation in nucleus localization sequence) parafibromin (p<0.05). Both WT and MT transfectants inhibited migration and invasion, and caused better differentiation (p<0.05) of cancer cells. WT parafibromin transfectants showed the overexpression of Cyclin B1, Cyclin D1, Cyclin E, p38, p53, and AIF in HCT-15 and HCT-116 cells, while MT parafibromin only up-regulated p38 expression. There was lower mRNA expression of bcl-2 in parafibromin transfectants than the control and mock, while higher expression of c-myc, Cyclin D1, mTOR, and Raptor. According to transcriptomic analysis, WT parafibromin suppressed PI3K-Akt and FoxO signaling pathways, while MT one promoted PI3K-Akt pathway, focal adhesion, and regulation of actin cytoskeleton. Parafibromin was less expressed in colorectal cancer than paired mucosa (p<0.05), and inversely correlated with its differentiation at both mRNA and protein levels (p<0.05). These findings indicated that WT parafibromin might reverse the aggressive phenotypes of colorectal cancer cells and be employed as a target for gene therapy. Down-regulated parafibromin expression might be closely linked to colorectal carcinogenesis and cancer differentiation.

Significance of Parafibromin Expression in Laryngeal Squamous Cell Carcinomas

BACKGROUND

Parafibromin is a product of the tumor suppressor gene that has been studied as a potential indicator of tumor aggressiveness in the parathyroid, breast, colorectum, and stomach. However, the clinical significance and potential function of parafibromin expression in head and neck squamous cell carcinomas remain largely unknown. The aim of this study was to evaluate the expression of parafibromin in laryngeal squamous cell carcinoma (LSCC) and to verify its potential as a biomarker of tumor behavior.

METHODS

Parafibromin expression was evaluated in 30 cases of LSCC using immunohistochemistry. The correlations between parafibromin expression and clinicopathologic parameters were investigated.

RESULTS

Parafibromin expression was positive in 15 cases (50%) and negative in 15 cases (50%). Tumor size and T stage showed a statistically significant inverse relationship with parafibromin expression (p=.028 and p<.001, respectively). Parafibromin expression was not associated with age, sex, lymph node metastasis, tumor differentiation, or tumor location. There was no statistically significant relationship between parafibromin expression and progression-free survival in the patients (p>.05).

CONCLUSIONS

Our results indicate that the downregulation or loss of parafibromin expression can be employed as a novel marker of tumor progression or aggressiveness in LSCC.

The Role of Parafibromin, Galectin-3, HBME-1, and Ki-67 in the Differential Diagnosis of Parathyroid Tumors

OBJECTIVES

Parathyroid carcinoma (PC) is a rare parathyroid tumor compared to parathyroid adenoma (PA) and atypical parathyroid adenoma (APA). Recent studies have suggested parafibromin has a role in the differential diagnosis of parathyroid tumors. We sought to determine the role of parafibromin as well as galectin-3, Ki-67, and HBME-1 as diagnostic markers in the differential diagnosis of parathyroid tumors.

METHODS

A total of 92 cases diagnosed with PA, APA, or PC at Sifa University and Private Ege Pathology Laboratory between 2006-2012 were included in the study. Parafibromin (microarray), galectin-3, Ki-67, and HBME-1 were evaluated using immunohistochemistry in all parathyroid tumors.

RESULTS

Eighty-four cases were diagnosed with PA, six with APA, and two with PC. The study group consisted of 82 females and 10 males. Their mean age was 50.9 years, and the mean tumor diameter was 1.97 cm. Parafibromin was negative in the two PC cases but positive in all APA and PA cases. Positivity was observed with galectin-3 in 17 adenoma cases, three atypical adenomas, and two carcinoma cases. Positivity with HBME-1 was found in 26 PA cases and one PC case. Parafibromin and galectin-3 expression was significant between the three tumor groups but not for HBME-1 expression. Parafibromin expression increased in PA whereas galectin-3 expression decreased. A statistical significance was found between the three tumor groups according to the Ki-67 score (p=0.010). Additionally, the Ki-67 proliferation index was under 1% in PAs.

CONCLUSION

The number of PCs in our series was small so our data mostly reflects the immunohistochemical characteristics of PAs. Parafibromin expression, galectin-3 negativity, and a Ki-67 proliferation index under 1% were estimated as beneficial in the differential diagnosis of difficult parathyroid tumors.

The roles of parafibromin expression in ovarian epithelial carcinomas: a marker for differentiation and prognosis and a target for gene therapy

Parafibromin is a protein encoded by hyperparathyroidism 2 (HRPT2) and its downregulated expression is involved in the pathogenesis of parathyroid, breast, gastric, colorectal, lung, head and neck cancers. We aimed to investigate the roles of parafibromin expression in tumorigenesis, progression, or prognostic evaluation of ovarian cancers. HRPT2-expressing plasmid was transfected into ovarian cancer cells with the phenotypes and related molecules examined. The messenger RNA (mRNA) and protein expression of parafibromin were also examined in ovarian normal tissue, benign and borderline tumors and cancers by reverse transcription-polymerase chain reaction (RT-PCR), Western blot, or immunohistochemistry respectively. It was found that parafibromin overexpression caused a lower growth, migration and invasion, higher sensitivity to cisplatin and apoptosis than the mock and control (P < 0.05). The transfectants showed the hypoexpression of phosphoinositide 3-kinase (PI3K), Akt, p70 ribosomal protein S6 kinase (p70s6k), Wnt5a, B cell lymphoma-extra large (Bcl-xL), survivin, vascular endothelial growth factor (VEGF) and matrix metallopeptidase 9 (MMP-9) than the mock and control at both mRNA and protein levels (P < 0.05). According to real-time PCR, parafibromin mRNA level was lower in ovarian benign tumors and cancers than normal ovary (P < 0.05), while parafibromin was strongly expressed in metastatic cancers in omentum than primary cancers by Western blot. Immunohistochemically, parafibromin expression was stronger in primary cancers than that in ovarian normal tissue (P < 0.05) but weaker than the metastatic cancers (P < 0.05) with a positive correlation with dedifferentiation, ki-67 expression and the lower cumulative survival rate (P < 0.05). These findings indicate that parafibromin downregulation might promote the pathogenesis, dedifferentiation and metastasis of ovarian cancers possibly by suppressing aggressive phenotypes, such as proliferation, cell cycle, apoptosis, migration and invasion.

Parafibromin Staining Characteristics in Urothelial Carcinomas and Relationship with Prognostic Parameters

Background:

Parafibromin is a recently defined tumor suppressor gene. The aim of our study was to determine the relationships of parafibromin expression in urothelial carcinomas (UCs) with prognostic parameters and to evaluate the use of parafibromin as a potential marker of UC.

Methods:

Parafibromin expression was assessed in 49 UC specimens using immunohistochemistry. The correlations between parafibromin expression and clinical and pathologic parameters were investigated.

Results:

Of the patients, 42 (85.7%) were male, and the mean age was 69.6 ± 8.2 years (range, 54 to 88 years). Morphologically, the UCs were divided into two groups: papillary (n = 27) and non-papillary (n = 22). There were seven low-grade (14.3%) and 42 high-grade (85.7%) tumors. Parafibromin was negative in 13 tumors (26.5%), partially positive in 19 tumors (38.8%), and positive in 17 tumors (34.7%). Parafibromin expression was more negative in UCs from upper urinary locations (n=17) and with muscularis propria invasion (n=28), which was statistically significant (p = .009 and p = .007, respectively). There was no statistically significant relationship between parafibromin expression and gender, age, tumor grade, survival, or disease-free survival.

Conclusions:

We found that UC cases with parafibromin positivity had less of a tendency to show muscularis propria invasion and were more commonly located in the lower urinary system. These results need to be confirmed with studies based on larger case series.

The clinicopathological significances and biological functions of parafibromin expression in head and neck squamous cell carcinomas

Downregulated parafibromin expression is involved in the pathogenesis and progression of parathyroid, breast, gastric, colorectal, and lung cancers. To investigate the roles of parafibromin expression in tumorigenesis, progression, and prognostic evaluation of head and neck squamous cell carcinomas (HNSCCs), we transfected parafibromin-expressing plasmid into HNSCC cell and examined the phenotypes and their relevant molecules. Parafibromin expression was detected on tissue microarray containing squamous epithelium, dysplasia, and carcinoma of head and neck by immunohistochemistry. Parafibromin overexpression was found to suppress growth, migration, and invasion, and induce apoptosis, S arrest, and mesenchymal to epithelial transition (EMT), compared with the mock and control (P < 0.05). Both overexpression of Cyclin E1, Bax, and E-cadherin and hypoexpression of c-myc, Bcl-xL, and slug were detected in B88 transfectants, in comparison to mock and control by real-time PCR. Parafibromin expression was weaker in primary cancers than those in normal squamous tissue and dysplasia (P < 0.05), but stronger than the metastatic cancers in lymph node (P < 0.05). Parafibromin expression was negatively correlated with lymph node metastasis, tumor-node-metastasis (TNM) staging, but positively with human papillomavirus (HPV) positivity (P < 0.05). The HNSCCs in tongue showed more parafibromin expression than those in larynx (P < 0.05). There was stronger parafibromin expression in moderately-than poorly-differentiated carcinomas (P < 0.05). The significantly positive correlation was observed between parafibromin expression and relapse-free survival rate by Kaplan-Meier curves (P < 0.05). Cox's proportional hazard model indicated that distant metastasis and parafibromin expression were independent prognostic factors for overall and relapse-free survival of HNSCC, respectively (P < 0.05). These findings suggest that downregulated expression of parafibromin protein plays an important role in the pathogenesis, differentiation, and metastasis of HNSCCs possibly by inducing apoptosis, suppressing proliferation, cell cycle progression, migration, invasion, and EMT. Parafibromin expression is an independent factor for relapse-free survival of HNSCCs.

Effects of parafibromin expression on the phenotypes and relevant mechanisms in the DLD-1 colon carcinoma cell line

BACKGROUND

Parafibromin is a protein encoded by the HRPT2 (hyperparathyroidism 2) oncosuppressor gene and its down-regulated expression is involved in pathogenesis of parathyroid, breast, gastric and colorectal carcinomas. This study aimed to clarify the effects of parafibromin expression on the phenotypes and relevant mechanisms of DLD-1 colon carcinoma cells.

METHODS

DLD-1 cells transfected with a parafibromin-expressing plasmid were subjected to examination of phenotype, including proliferation, differentiation, apoptosis, migration and invasion. Phenotype-related proteins were measured by Western blot. Parafibromin and ki-67 expression was detected by immunohistochemistry on tissue microarrays.

RESULTS

The transfectants showed higher proliferation by CCK-8, better differentiation by electron microscopy and ALP activity and more apoptotic resistance to cisplatin by DNA fragmentation than controls. There was no difference in early apoptosis by annexin V, capase-3 activity, migration and invasion between DLD-1 cells and their transfectants. Ectopic parafibromin expression resulted in down-regulated expression of smad4, MEKK, GRP94, GRP78, GSK3β-ser9, and Caspase-9. However, no difference was detectable in caspase-12 and -8 expression. A positive relationship was noted between parafibromin and ki-67 expression in colorectal carcinoma.

CONCLUSIONS

Parafibromin overexpression could promote cell proliferation, apoptotic resistance, and differentiation of DLD-1 cells.

Expression of parafibromin in major renal cell tumors

Parafibromin, encoded by HRPT2 gene, is a recently identified tumor suppressor. Complete and partial loss of its expression have been observed in hyperparathyroidism-jaw tumor (HPT-JT), parathyroid carcinoma, breast carcinoma, lung carcinoma, gastric and colorectal carcinoma. However, little has been known about its expression in renal tumors. In order to study the expression of parafibromin in a series of the 4 major renal cell tumors - clear cell renal cell carcinoma (ccRCC), papillary renal cell carcinoma (pRCC), chromophobe renal cell carcinoma (chRCC) and oncocytoma, one hundred thirty nine renal tumors including 61 ccRCCs, 37 pRCCs, 22 chRCCs and 19 oncocytomas were retrieved and used for the construction of renal tissue microarrays (TMAs). The expression of parafibromin was detected by immunohistochemical method on the constructed TMAs. Positive parafibromin stains are seen in 4 out of 61 ccRCCs (7%), 7 out of 37 pRCCs (19%), 12 out of 23 chRCCs (52%) and all 19 oncocytomas (100%). Parafibromin expression varies significantly (P<8.8×10⁻¹⁶) among the four major renal cell tumors and were correlated closely with tumor types. No correlation of parafibromin expression with tumor staging in ccRCCs, pRCCs and chRCCs, and Fuhrman nuclear grading in ccRCCs and pRCCs was seen. In summary, parafibromin expression was strongly correlated with tumor types, which may suggest that it plays a role in the tumorigenesis in renal cell tumors.

The many roles of the conserved eukaryotic Paf1 complex in regulating transcription, histone modifications, and disease states

The Paf1 complex was originally identified over fifteen years ago in budding yeast through its physical association with RNA polymerase II. The Paf1 complex is now known to be conserved throughout eukaryotes and is well studied for promoting RNA polymerase II transcription elongation and transcription-coupled histone modifications. Through these critical regulatory functions, the Paf1 complex participates in numerous cellular processes such as gene expression and silencing, RNA maturation, DNA repair, cell cycle progression and prevention of disease states in higher eukaryotes. In this review, we describe the historic and current research involving the eukaryotic Paf1 complex to explain the cellular roles that underlie its conservation and functional importance. This article is part of a Special Issue entitled: RNA polymerase II Transcript Elongation.

The pathobiological features of gastrointestinal cancers (Review)

Gastrointestinal adenocarcinoma (GIA) is a common malignant disease worldwide. Its tumorigenesis and progression is a multistage process with the involvement of a multifactorial etiology. Knowledge regarding altered expression of these genes during carcinogenesis may not only provide information about the molecular events during the initiation and progression of cancer, but may also result in the discovery of biological markers for the evaluation of cancer diagnosis and prognosis. In this review, we assessed molecular markers of pathogenesis, invasion, metastasis and prognosis, such as tumor suppressor and metastasis suppressor genes, and angiogenesis, cell adhesion, cell mobility, ER stress, mucin production, threonine protein kinase and REG family protein expression, by the establishment of tissue microarray (TMA) of GIA and immunohistochemistry (IHC) by intermittent microwave irradiation and in situ hybridization (ISH). Finally, we characterized the pathobiological features of Lauren's and WHO subtypes. It was found that the aberrant and cell-specific expression of these molecules is important in the malignant transformation of gastrointestinal epithelium and subsequent progression. These molecules also underlie the histogenic mechanisms of gastric carcinoma according to Lauren's and WHO classification. The combination of TMA, IHC and ISH may be widely applied to screen for molecular markers in GIA.

The tumor suppressor CDC73 interacts with the ring finger proteins RNF20 and RNF40 and is required for the maintenance of histone 2B monoubiquitination

Monoubiquitination of histone H2B is a dynamic post-translational histone modification associated with transcriptional elongation and the DNA damage response. To date, dysregulation of histone monoubiquitination has not been linked to pathogenic mutations in genes encoding proteins, or co-factors, catalyzing this modification. The tumor suppressor cell division cycle 73 (CDC73) is mutated and/or down-regulated in parathyroid carcinoma, renal, breast, gastric and colorectal tumors, as well as in the germline of patients with the familial disorder-hyperparathyroidism jaw tumor syndrome. Using CDC73 as bait in a yeast two-hybrid assay, we identified the ring finger proteins RNF20 and RNF40 as binding partners of this tumor suppressor. These polypeptides constitute a heterodimeric complex that functions as the E3 ubiquitin ligase for monoubiquitination of histone H2B at lysine 120 (H2B-K120). We show that RNF20 and RNF40 bind to discrete, but closely located, residues on CDC73. Monoubiquitinated H2B-K120 was significantly reduced after loss of nuclear CDC73, both in vitro upon down-regulation of CDC73, and in CDC73 mutant parathyroid tumors. A second histone modification, trimethylation of histone 3 at lysine 4 (H3-K4me3), remained unchanged in the presence of mutant or down-regulated CDC73, suggesting that H3-K4me3 is not always tightly linked to H2B-K120 monoubiquitination for transcription as previously described. This is the first report of pathogenic mutations affecting histone monoubiquitination. We conclude that CDC73 is required for the maintenance of H2B-K120 monoubiquitination and propose that reduction in levels of monoubiquitinated H2B-K120 is a major mechanism whereby mutations in CDC73 exert their tumorigenic effect.