RB1 in cancer: different mechanisms of RB1 inactivation and alterations of pRb pathway in tumorigenesis

Transcription Factors in Cancer Development and Therapy

Cancer is a multi-step process and requires constitutive expression/activation of transcription factors (TFs) for growth and survival. Many of the TFs reported so far are critical for carcinogenesis. These include pro-inflammatory TFs, hypoxia-inducible factors (HIFs), cell proliferation and epithelial-mesenchymal transition (EMT)-controlling TFs, pluripotency TFs upregulated in cancer stem-like cells, and the nuclear receptors (NRs). Some of those, including HIFs, Myc, ETS-1, and β-catenin, are multifunctional and may regulate multiple other TFs involved in various pro-oncogenic events, including proliferation, survival, metabolism, invasion, and metastasis. High expression of some TFs is also correlated with poor prognosis and chemoresistance, constituting a significant challenge in cancer treatment. Considering the pivotal role of TFs in cancer, there is an urgent need to develop strategies targeting them. Targeting TFs, in combination with other chemotherapeutics, could emerge as a better strategy to target cancer. So far, targeting NRs have shown promising results in improving survival. In this review, we provide a comprehensive overview of the TFs that play a central role in cancer progression, which could be potential therapeutic candidates for developing specific inhibitors. Here, we also discuss the efforts made to target some of those TFs, including NRs.

Human papillomavirus type 38 alters wild-type p53 activity to promote cell proliferation via the downregulation of integrin alpha 1 expression

Tumor suppressors can exert pro-proliferation functions in specific contexts. In the beta human papillomavirus type 38 (HPV38) experimental model, the viral proteins E6 and E7 promote accumulation of a wild-type (WT) p53 form in human keratinocytes (HKs), promoting cellular proliferation. Inactivation of p53 by different means strongly decreases the proliferation of HPV38 E6/E7 HKs. This p53 form is phosphorylated at S392 by the double-stranded RNA-dependent protein kinase PKR, which is highly activated by HPV38. PKR-mediated S392 p53 phosphorylation promotes the formation of a p53/DNMT1 complex, which inhibits expression of integrin alpha 1 (ITGA1), a repressor of epidermal growth factor receptor (EGFR) signaling. Ectopic expression of ITGA1 in HPV38 E6/E7 HKs promotes EGFR degradation, inhibition of cellular proliferation, and cellular death. Itga1 expression was also inhibited in the skin of HPV38 transgenic mice that have an elevated susceptibility to UV-induced skin carcinogenesis. In summary, these findings reveal the existence of a specific WT p53 form that displays pro-proliferation properties.

PRMT5 promotes cancer cell migration and invasion through the E2F pathway

The pRb-E2F pathway is a critical point of regulation in the cell cycle and loss of control of the pathway is a hallmark of cancer. E2F1 is the major target through which pRb exerts its effects and arginine methylation by PRMT5 plays a key role in dictating E2F1 activity. Here we have explored the functional role of the PRMT5-E2F1 axis and highlight its influence on different aspects of cancer cell biology including viability, migration, invasion and adherence. Through a genome-wide expression analysis, we identified a distinct set of genes under the control of PRMT5 and E2F1, including some highly regulated genes, which influence cell migration, invasio and adherence through a PRMT5-dependent mechanism. Most significantly, a coincidence was apparent between the expression of PRMT5 and E2F1 in human tumours, and elevated levels of PRMT5 and E2F1 correlated with poor prognosis disease. Our results suggest a causal relationship between PRMT5 and E2F1 in driving the malignant phenotype and thereby highlight an important pathway for therapeutic intervention.

Cryptorchidism, gonocyte development, and the risks of germ cell malignancy and infertility: A systematic review

BACKGROUND/AIM

Cryptorchidism, or undescended testis (UDT) occurs in 1%-4% of newborn males and leads to a risk of infertility and testicular malignancy. Recent research suggests that infertility and malignancy in UDT may be caused by abnormal development of the neonatal germ cells, or gonocytes, which normally transform into spermatogonial stem cells (SSC) or undergo apoptosis during minipuberty at 2-6 months in humans (2-6 days in mice). We aimed to identify the current knowledge on how UDT is linked to infertility and malignancy.

METHODS

Here we review the literature from 1995 to the present to assess the possible causes of infertility and malignancy in UDT, from both human studies and animal models.

RESULTS

Both the morphological steps and many of the genes involved in germ cell development are now characterized, but the factors involved in gonocyte transformation and apoptosis in both normal and cryptorchid testes are not fully identified. During minipuberty there is evidence for the hypothalamic-pituitary axis stimulating gonocyte transformation, but without known direct control by LH and androgen, although FSH may have a role. An arrested gonocyte maybe the origin of later malignancy at least in syndromic cryptorchid testes in humans, which is consistent with the recent finding that gonocytes are normally absent in a rodent model of congenital cryptorchidism, where malignancy has not been reported.

CONCLUSION

The results of this review strengthen the view that malignancy and infertility in men with previous UDT may be caused by abnormalities in germ cell development during minipuberty.

TYPE OF STUDY

Systematic review (secondary, filtered) LEVEL OF EVIDENCE: Level I.

Functional Significance and Therapeutic Potential of miRNA-20b-5p in Esophageal Squamous Cell Carcinoma

Novel therapies tailored to the molecular composition mechanism of esophageal squamous cell carcinoma (ESCC) are needed to improve patient survival. miR-20b-5p expression was significantly upregulated in cancerous tissues and associated with lymph node metastasis, clinical stage, and overall survival (OS). An analysis of the methylation status of the miR-20b-5p gene indicated that the hypomethylation of the CpG sites located upstream of the miR-20b-5p gene in the ESCC tissues was more frequent than in the adjacent normal tissues, and the methylation status of miR-20b-5p correlated inversely with its expression levels. Notably, a series of gain- and loss-of-function assays elucidated that miR-20b-5p promoted ESCC cell proliferation, migration, and invasion both in vitro and in vivo. Luciferase reporter assays, western blot, and qRT-PCR revealed that RB1 and TP53INP1 were the direct targets of miR-20b-5p. Moreover, the effects of ectopic miR-20b-5p expression were abrogated by RB1 and TP53INP1 overexpression. In contrast, the effects of miR-20b-5p depletion were impaired by RB1 and TP53INP1 knockdown. Treatment with a miR-20b-5p antagomir dramatically increased tumor growth and inhibited RB1 and TP53INP1 protein expression in nude mice. This work provided novel insights on the molecular mechanism of ESCC and further provided suggestions for therapy development.

Acquired resistance to combined BET and CDK4/6 inhibition in triple-negative breast cancer

BET inhibitors are promising therapeutic agents for the treatment of triple-negative breast cancer (TNBC), but the rapid emergence of resistance necessitates investigation of combination therapies and their effects on tumor evolution. Here, we show that palbociclib, a CDK4/6 inhibitor, and paclitaxel, a microtubule inhibitor, synergize with the BET inhibitor JQ1 in TNBC lines. High-complexity DNA barcoding and mathematical modeling indicate a high rate of de novo acquired resistance to these drugs relative to pre-existing resistance. We demonstrate that the combination of JQ1 and palbociclib induces cell division errors, which can increase the chance of developing aneuploidy. Characterizing acquired resistance to combination treatment at a single cell level shows heterogeneous mechanisms including activation of G1-S and senescence pathways. Our results establish a rationale for further investigation of combined BET and CDK4/6 inhibition in TNBC and suggest novel mechanisms of action for these drugs and new vulnerabilities in cells after emergence of resistance.

RABL6A Is an Essential Driver of MPNSTs that Negatively Regulates the RB1 Pathway and Sensitizes Tumor Cells to CDK4/6 Inhibitors

PURPOSE

Malignant peripheral nerve sheath tumors (MPNST) are deadly sarcomas that lack effective therapies. In most MPNSTs, the retinoblastoma (RB1) tumor suppressor is disabled by hyperactivation of cyclin-dependent kinases (CDK), commonly through loss of CDK-inhibitory proteins such as p27(Kip1). RABL6A is an inhibitor of RB1 whose role in MPNSTs is unknown. To gain insight into MPNST development and establish new treatment options, we investigated RABL6A-RB1 signaling and CDK inhibitor-based therapy in MPNSTs.

EXPERIMENTAL DESIGN

We examined patient-matched MPNSTs and precursor lesions by RNA sequencing (RNA-Seq) and IHC. Molecular and biological effects of silencing RABL6A and/or p27 in MPNST lines and normal human Schwann cells were determined. Tumor-suppressive effects of CDK inhibitors were measured in MPNST cells and orthotopic tumors.

RESULTS

RABL6A was dramatically upregulated in human MPNSTs compared with precursor lesions, which correlated inversely with p27 levels. Silencing RABL6A caused MPNST cell death and G₁ arrest that coincided with p27 upregulation, CDK downregulation, and RB1 activation. The growth-suppressive effects of RABL6A loss, and its regulation of RB1, were largely rescued by p27 depletion. Importantly, reactivation of RB1 using a CDK4/6 inhibitor (palbociclib) killed MPNST cells in vitro in an RABL6A-dependent manner and suppressed MPNST growth in vivo. Low-dose combination of drugs targeting multiple RB1 kinases (CDK4/6, CDK2) had enhanced antitumorigenic activity associated with potential MPNST cell redifferentiation.

CONCLUSIONS

RABL6A is a new driver of MPNST pathogenesis that acts in part through p27-RB1 inactivation. Our results suggest RB1 targeted therapy with multiple pathway drugs may effectively treat MPNSTs.

Protein expression profiles and prognostic value of E2F family members in clear cell renal cell carcinoma

The derangement of the cell cycle facilitates uncontrolled cell proliferation and acquisition of genetic alterations favorable for malignancy. However, the protein expression profiles of E2 F family cell cycle regulators in clear cell renal cell carcinoma (ccRCC) have not yet been thoroughly investigated. In this study, we aimed to examine the protein expression profiles and prognostic value of E2 F1, E2 F3, and E2 F4 in ccRCC cases. The immunohistochemical expression of E2 F1, E2 F3, and E2 F4 was quantitatively scored in 180 ccRCC tumor tissues and 79 normal kidney tissues. The prognostic implications of these E2 F members were determined. We found that ccRCC tumor cells showed higher nuclear expression of E2 F1, E2 F3 and E2 F4 than normal kidney samples. High E2 F1 and E2 F3 expression in tumor cells was associated with poor prognostic factors of ccRCC, whereas high E2 F4 correlated with beneficial prognostic factors. High expression of E2 F1 and E2 F3 in tumor cells was correlated with a poor overall and recurrence-free survival, while high E2 F4 expression did not. In conclusion, E2 F1, E2 F3 and E2 F4 may function as oncogenes during tumorigenesis of ccRCC, although they contribute to the progression of ccRCC in different ways. Additional studies are required to clarify the conflicting role of E2 F4 in the tumor evolution of ccRCC.

Significance of BRCA2 and RB1 Co-loss in Aggressive Prostate Cancer Progression

PURPOSE

Previous sequencing studies revealed that alterations of genes associated with DNA damage response (DDR) are enriched in men with metastatic castration-resistant prostate cancer (mCRPC). BRCA2, a DDR and cancer susceptibility gene, is frequently deleted (homozygous and heterozygous) in men with aggressive prostate cancer. Here we show that patients with prostate cancer who have lost a copy of BRCA2 frequently lose a copy of tumor suppressor gene RB1; importantly, for the first time, we demonstrate that co-loss of both genes in early prostate cancer is sufficient to induce a distinct biology that is likely associated with worse prognosis.

EXPERIMENTAL DESIGN

We prospectively investigated underlying molecular mechanisms and genomic consequences of co-loss of BRCA2 and RB1 in prostate cancer. We used CRISPR-Cas9 and RNAi-based methods to eliminate these two genes in prostate cancer cell lines and subjected them to in vitro studies and transcriptomic analyses. We developed a 3-color FISH assay to detect genomic deletions of BRCA2 and RB1 in prostate cancer cells and patient-derived mCRPC organoids.

RESULTS

In human prostate cancer cell lines (LNCaP and LAPC4), loss of BRCA2 leads to the castration-resistant phenotype. Co-loss of BRCA2-RB1 in human prostate cancer cells induces an epithelial-to-mesenchymal transition, which is associated with invasiveness and a more aggressive disease phenotype. Importantly, PARP inhibitors attenuate cell growth in human mCRPC-derived organoids and human CRPC cells harboring single-copy loss of both genes.

CONCLUSIONS

Our findings suggest that early identification of this aggressive form of prostate cancer offers potential for improved outcomes with early introduction of PARP inhibitor-based therapy.See related commentary by Mandigo and Knudsen, p. 1784.

Copy number variation is highly correlated with differential gene expression: a pan-cancer study

BACKGROUND

Cancer is a heterogeneous disease with many genetic variations. Lines of evidence have shown copy number variations (CNVs) of certain genes are involved in development and progression of many cancers through the alterations of their gene expression levels on individual or several cancer types. However, it is not quite clear whether the correlation will be a general phenomenon across multiple cancer types.

METHODS

In this study we applied a bioinformatics approach integrating CNV and differential gene expression mathematically across 1025 cell lines and 9159 patient samples to detect their potential relationship.

RESULTS

Our results showed there is a close correlation between CNV and differential gene expression and the copy number displayed a positive linear influence on gene expression for the majority of genes, indicating that genetic variation generated a direct effect on gene transcriptional level. Another independent dataset is utilized to revalidate the relationship between copy number and expression level. Further analysis show genes with general positive linear influence on gene expression are clustered in certain disease-related pathways, which suggests the involvement of CNV in pathophysiology of diseases.

CONCLUSIONS

This study shows the close correlation between CNV and differential gene expression revealing the qualitative relationship between genetic variation and its downstream effect, especially for oncogenes and tumor suppressor genes. It is of a critical importance to elucidate the relationship between copy number variation and gene expression for prevention, diagnosis and treatment of cancer.

MED12, TERT and RARA in fibroepithelial tumours of the breast

Fibroepithelial tumours are biphasic neoplasms of the breast comprising the common benign fibroadenomas and the less common phyllodes tumours (PTs), which have recurrent potential. PTs are classified into benign, borderline or malignant, based on five histopathological criteria, with malignant PTs having the highest metastatic capability. Accurate diagnosis can be challenging due to the subjective assessment of histopathological parameters. Fibroadenomas bear morphological similarities to benign PTs, while borderline and malignant PTs can sometimes be difficult to distinguish from other spindle cell tumours of the breast. From clonality studies to whole-genome sequencing, much research has been conducted to elucidate the molecular pathogenesis of fibroepithelial tumours, which, in turn, have allowed leveraging the findings for diagnostic applications, including grading of PTs. The most noteworthy discovery was of recurrent MED12 mutations in both fibroadenomas and PTs. Subsequent studies also uncovered relatively frequent genetic mutations in TERT promoter and RARA. A customised panel of 16 most frequently mutated genes in fibroepithelial tissues has been compiled previously and has contributed to resolving a few diagnostic dilemmas. This review will introduce the 16 genes and focus on the top three that are most frequently mutated in fibroepithelial tumours: MED12, TERT, and RARA.

MMP14 in Sarcoma: A Regulator of Tumor Microenvironment Communication in Connective Tissues

Sarcomas are deadly malignant tumors of mesenchymal origin occurring at all ages. The expression and function of the membrane-type matrix metalloproteinase MMP14 is closely related to the mesenchymal cell phenotype, and it is highly expressed in most sarcomas. MMP14 regulates the activity of multiple extracellular and plasma membrane proteins, influencing cell–cell and cell–extracellular matrix (ECM) communication. This regulation mediates processes such as ECM degradation and remodeling, cell invasion, and cancer metastasis. Thus, a comprehensive understanding of the biology of MMP14 in sarcomas will shed light on the mechanisms controlling the key processes in these diseases. Here, we provide an overview of the function and regulation of MMP14 and we discuss their relationship with clinical and pre-clinical MMP14 data in both adult and childhood sarcomas.

CDK4/6 inhibitor protects chemerin-induced human granulosa-lutein cells from apoptosis by inhibiting the p53/p21 waf pathway

Dysregulation of the cell cycle is common in human tumorigenesis. Therefore, CDK4/6 inhibitors targeting the cell cycle have been developed, and their antiapoptotic effects have been highly correlated with potential clinical therapies. The aim of this study was to identify the regulatory effect of the CDK4/6 inhibitor palbociclib on chemerin-induced apoptosis of immortalized human granulosa-lutein (hGL) cells and to elucidate its fundamental mechanism of action. Palbociclib enhanced antioxidative enzyme generation and diminished ROS generation in hGL cells. Furthermore, we found that palbociclib suppressed chemerin-induced apoptotic protein expression, reversing the Bcl-2/Bax ratio and inhibiting the p53/p21 ^waf pathway. Eventually, palbociclib decreased the level of cleaved caspase-3 and -9, hindering the apoptosis of hGL cells. In general, the antiapoptotic efficacy of palbociclib could be attributed in part to the modulation of the mitochondrial apoptotic pathway in hGL cells.

Arginine methylation expands the regulatory mechanisms and extends the genomic landscape under E2F control

E2F is a family of master transcription regulators involved in mediating diverse cell fates. Here, we show that residue-specific arginine methylation (meR) by PRMT5 enables E2F1 to regulate many genes at the level of alternative RNA splicing, rather than through its classical transcription-based mechanism. The p100/TSN tudor domain protein reads the meR mark on chromatin-bound E2F1, allowing snRNA components of the splicing machinery to assemble with E2F1. A large set of RNAs including spliced variants associate with E2F1 by virtue of the methyl mark. By focusing on the deSUMOylase SENP7 gene, which we identified as an E2F target gene, we establish that alternative splicing is functionally important for E2F1 activity. Our results reveal an unexpected consequence of arginine methylation, where reader-writer interplay widens the mechanism of control by E2F1, from transcription factor to regulator of alternative RNA splicing, thereby extending the genomic landscape under E2F1 control.

The broken cycle: E2F dysfunction in cancer

The cyclin-dependent kinase (CDK)-RB-E2F axis forms the core transcriptional machinery driving cell cycle progression, dictating the timing and fidelity of genome replication and ensuring genetic material is accurately passed through each cell division cycle. The ultimate effectors of this axis are members of a family of eight distinct E2F genes encoding transcriptional activators and repressors. E2F transcriptional activity is tightly regulated throughout the cell cycle via transcriptional and translational regulation, post-translational modifications, protein degradation, binding to cofactors and subcellular localization. Alterations in one or more key components of this axis (CDKs, cyclins, CDK inhibitors and the RB family of proteins) occur in virtually all cancers and result in heightened oncogenic E2F activity, leading to uncontrolled proliferation. In this Review, we discuss the activities of E2F proteins with an emphasis on the newest atypical E2F family members, the specific and redundant functions of E2F proteins, how misexpression of E2F transcriptional targets promotes cancer and both current and developing therapeutic strategies being used to target this oncogenic pathway.

A Longitudinal Study of the Association between Mammographic Density and Gene Expression in Normal Breast Tissue

High mammographic density (MD) is associated with a 4-6 times increase in breast cancer risk. For post-menopausal women, MD often decreases over time, but little is known about the underlying biological mechanisms. MD reflects breast tissue composition, and may be associated with microenvironment subtypes previously identified in tumor-adjacent normal tissue. Currently, these subtypes have not been explored in normal breast tissue. We obtained biopsies from breasts of healthy women at two different time points several years apart and performed microarray gene expression analysis. At time point 1, 65 samples with both MD and gene expression were available. At time point 2, gene expression and MD data were available from 17 women, of which 11 also had gene expression data available from the first time point. We validated findings from our previous study; negative correlation between RBL1 and MD in post-menopausal women, indicating involvement of the TGFβ pathway. We also found that breast tissue samples from women with a large decrease in MD sustained higher expression of genes in the histone family H4. In addition, we explored the previously defined active and inactive microenvironment subtypes and demonstrated that normal breast samples of the active subtype had characteristics similar to the claudin-low breast cancer subtype. Breast biopsies from healthy women are challenging to obtain, but despite a limited sample size, we have identified possible mechanisms relevant for changes in breast biology and MD over time that may be of importance for breast cancer risk and tumor initiation.

NCKAP1 improves patient outcome and inhibits cell growth by enhancing Rb1/p53 activation in hepatocellular carcinoma

In our previous report, we identified miR-34c-3p as an independent factor contributing to the carcinogenesis of hepatocellular carcinoma (HCC) by targeting NCK Associated Protein 1 (NCKAP1). NCKAP1 has been known to promote the malignancy of cancer cells by disrupting the structural stability of WAS protein family member 1 (WASF1) and is correlated with poor prognosis of patients in several cancer types. Our results, however, show that NCKAP1 is correlated with a favorable outcome in HCC patients. The underlying mechanism of this contradictory phenomenon is unknown. The current study was designed to explore the mechanism of NCKAP1 in HCC. As a result, clinicopathological correlations and results from in vivo and in vitro models indicated that NCKAP1 was a tumor suppressor gene. Cell cycle analysis suggested that NCKAP1 inhibit cells from entering G2/M phase. Western blot analysis showed that WASF1 was barely expressed in HCC cell lines compared to that of breast cancer cell lines, which serve as positive controls. Furthermore, Rb1 and p53 expression was upregulated in cell lines overexpressing NCKAP1. Expression of several cell cycle regulating proteins also varied in the HCC cell lines. In conclusion, although previous studies have identified NCKAP1 as a cell invasion promoter by binding to WASF1, we found that NCKAP1 is a tumor suppress gene that modulates the cell cycle of HCC cell lines by targeting Rb1/p53 regulation.

CDK4/6 inhibitor protects against myocardial cells apoptosis by inhibiting RB phosphorylation in H9c2 cells

Cell cycle dysregulation is typical in human cancers, and CDK4/6 inhibitors targeting cell cycle have potential antiapoptosis effect. The aim of this work is to identify the regulatory effect of Palbociclib on apoptosis of H9c2 cells induced by high glucose (HG) and to elucidate the fundamental mechanisms. It was observed that Palbociclib decreased intracellular ROS production, augmented mitochondrial membrane potential and hindered apoptosis of H9c2 cells. Palbociclib increased the Bcl-2/Bax ratio, diminished the expressions of Bax and cleaved-caspase-3, and affected the RB phosphorylation and p53 expression. Altogether, the anti-apoptotic efficacy of Palbociclib could be attributed in part to the modulation of the mitochondria apoptotic pathway.

DNA replication licensing proteins: Saints and sinners in cancer

DNA replication is all-or-none process in the cell, meaning, once the DNA replication begins it proceeds to completion. Hence, to achieve maximum control of DNA replication, eukaryotic cells employ a multi-subunit initiator protein complex known as "pre-replication complex or DNA replication licensing complex (DNA replication LC). This complex involves multiple proteins which are origin-recognition complex family proteins, cell division cycle-6, chromatin licensing and DNA replication factor 1, and minichromosome maintenance family proteins. Higher-expression of DNA replication LC proteins appears to be an early event during development of cancer since it has been a common hallmark observed in a wide variety of cancers such as oesophageal, laryngeal, pulmonary, mammary, colorectal, renal, urothelial etc. However, the exact mechanisms leading to the abnormally high expression of DNA replication LC have not been clearly deciphered. Increased expression of DNA replication LC leads to licensing and/or firing of multiple origins thereby inducing replication stress and genomic instability. Therapeutic approaches where the reduction in the activity of DNA replication LC was achieved either by siRNA or shRNA techniques, have shown increased sensitivity of cancer cell lines towards the anti-cancer drugs such as cisplatin, 5-Fluorouracil, hydroxyurea etc. Thus, the expression level of DNA replication LC within the cell determines a cell's fate thereby creating a paradox where DNA replication LC acts as both "Saint" and "Sinner". With a potential to increase sensitivity to chemotherapy drugs, DNA replication LC proteins have prospective clinical importance in fighting cancer. Hence, in this review, we will shed light on importance of DNA replication LC with an aim to use DNA replication LC in diagnosis and prognosis of cancer in patients as well as possible therapeutic targets for cancer therapy.

CDKN2A as transcriptomic marker for muscle-invasive bladder cancer risk stratification and therapy decision-making

Deletions of the cell cycle control gene CDKN2A are described as progression markers of non-muscle invasive bladder cancer and to be associated with fibroblast growth factor 3 (FGFR3) mutations. The prognostic role of CDKN2A RNA expression in muscle invasive bladder cancer (MIBC) is under discussion. In 80 MIBC patients (m/f 60/20) who underwent radical cystectomy the expression of CDKN2A and FGFR3 was examined with qRT-PCR (test cohort). The MDA cohort (n = 57) and the TCGA cohort (n = 365) served for validation. The expression of drug target genes and TCGA molecular subtypes was correlated with CDKN2A expression. In the test cohort CDKN2Ahigh patients (n = 8; 10.0%) had a significantly shorter recurrence-free (p = 0.018) and disease-specific (p = 0.006) survival compared to the rest of the cohort. A similar stratification was seen in the validation cohorts (CDKN2Ahigh: n = 7, 12.3%, p = 0.001; n = 46, 12.6%, p = 0.011). In the TCGA cohort these patients had a comparably low expression of drug target genes. The expression of CDKN2A significantly differed among TGCA molecular subtypes. 71.7% of CDKN2Ahigh were TCGA basal squamous tumours but also show divergent molecular features compared to this group. In summary CDKN2A RNA expression-based risk stratification of MIBC allows the identification of a CDKN2Ahigh poor prognosis group with low expression of drug target genes.

PlncRNA-1 is overexpressed in retinoblastoma and regulates retinoblastoma cell proliferation and motility through modulating CBR3

PlncRNA-1 has been suggested to function as an oncogenic role in prostate cancer, colorectal cancer, hepatocellular carcinoma, esophageal squamous cell carcinoma, and gastric cancer. The expression pattern of PlncRNA-1 in retinoblastoma remained unknown. Therefore, the aim of this study was to explore the clinical significance of PlncRNA-1 in retinoblastoma patient and the biological function and molecular mechanism of PlncRNA-1 in regulating retinoblastoma cell proliferation, migration, and invasion. The results showed the level of PlncRNA-1 expression was obviously increased in retinoblastoma tissues and cell lines compared with compared with normal retina tissues and retina cell lines, respectively. Meanwhile, patients with advanced stage retinoblastoma had higher levels of PlncRNA-1 expression than patients with early stage retinoblastoma. There was an inverse correlation between PlncRNA-1 expression and CBR3 expression in retinoblastoma tissues, and PlncRNA-1 negatively regulated mRNA and protein expressions of CBR3. The in vitro experiments showed that down-regulation of PlncRNA-1 expression suppressed retinoblastoma cell proliferation, migration and invasion through up-regulating CBR3. In conclusion, PlncRNA-1 serves as an oncogenic lncRNA in regulating retinoblastoma cell proliferation, migration, and invasion through proliferation, migration, and invasion through up-regulating CBR3. © 2018 IUBMB Life, 70(10):969-975, 2018.

MECHANISMS OF ENDOCRINOLOGY: Cell cycle regulation in adrenocortical carcinoma

Adrenocortical carcinomas (ACCs) are rather rare endocrine tumors that often have a poor prognosis. The reduced survival rate associated with these tumors is due to their aggressive biological behavior, combined with the scarcity of effective treatment options that are currently available. The recent identification of the genomic alterations present in ACC have provided further molecular mechanisms to develop consistent strategies for the diagnosis, prevention of progression and treatment of advanced ACCs. Taken together, molecular and genomic advances could be leading the way to develop personalized medicine in ACCs similarly to similar developments in lung or breast cancers. In this review, we focused our attention to systematically compile and summarize the alterations in the cell cycle regulation that were described so far in ACC as they are known to play a crucial role in cell differentiation and growth. We have divided the analysis according to the major transition phases of the cell cycle, G1 to S and G2 to M. We have analyzed the most extensively studied checkpoints: the p53/Rb1 pathway, CDC2/cyclin B and topoisomerases (TOPs). We reached the conclusion that the most important alterations having a potential application in clinical practice are the ones related to p53/Rb1 and TOP 2. We also present a brief description of on-going clinical trials based on molecular alterations in ACC. The drugs have targeted the insulin-like growth factor receptor 1, TOP 2, polo-like kinase1, cyclin-dependent kinase inhibitors, p53 reactivation and CDC25.

Diagnostic molecular techniques in haematology: recent advances

Hematopoietic disorders are often driven by genetic mutations and epigenetic alterations. New advanced technologies including next-generation sequencing, ultra-deep PCR and whole-genome and exome sequencing were proved very efficient in detecting several mutations implicated in the pathogenesis of hematological diseases. Emerging evidence indicates that genomic data can be useful in all aspects of clinical practice including diagnosis, prognosis and prediction of response to specific treatments, as well as in the development of novel targeted treatments for patients with hematological disorders.

Nanos genes and their role in development and beyond

The hallmark of Nanos proteins is their typical (CCHC)2 zinc finger motif (zf-nanos). Animals have one to four nanos genes. For example, the fruit fly and demosponge have only one nanos gene, zebrafish and humans have three, and Fugu rubripes has four. Nanos genes are mainly known for their evolutionarily preserved role in germ cell survival and pluripotency. Nanos proteins have been reported to bind the C-terminal RNA-binding domain of Pumilio to form a post-transcriptional repressor complex. Several observations point to a link between the miRNA-mediated repression complex and the Nanos/Pumilio complex. Repression of the E2F3 oncogene product is, indeed, mediated by cooperation between the Nanos/Pumilio complex and miRNAs. Another important interaction partner of Nanos is the CCR4-NOT deadenylase complex. Besides the tissue-specific contribution of Nanos proteins to normal development, their ectopic expression has been observed in several cancer cell lines and various human cancers. An inverse correlation between the expression levels of human Nanos1 and Nanos3 and E-cadherin was observed in several cancer cell lines. Loss of E-cadherin, an important cell-cell adhesion protein, contributes to tumor invasion and metastasis. Overexpression of Nanos3 induces epithelial-mesenchymal transition in lung cancer cell lines partly by repressing E-cadherin. Other than some most interesting data from Nanos knockout mice, little is known about mammalian Nanos proteins, and further research is needed. In this review, we summarize the main roles of Nanos proteins and discuss the emerging concept of Nanos proteins as oncofetal antigens.

Small cell carcinoma of the urinary bladder: a clinicopathological and immunohistochemical analysis of 81 cases

Small cell carcinoma (SmCC) of the bladder is a rare disease. We retrospectively studied a large series of bladder SmCC from a single institution. The patients included 69 men and 12 women with a mean age of 68 years. Most bladder SmCCs were presented at advanced stage, with tumors invading the muscularis propria and beyond (n = 77). SmCC was pure in 27 cases and mixed with other histologic types in 54 cases, including urothelial carcinoma (UC) (n = 32), UC in situ (n = 26), glandular (n = 14), micropapillary (n = 4), sarcomatoid (n = 4), squamous (n = 3), and plasmacytoid (n = 1) features. Most SmCCs expressed neuroendocrine markers synaptophysin (41/56), chromogranin (26/55), and CD56 (39/41); however, they did not express UC luminal markers CK20 (0/17), GATA3 (1/30), and uroplakin II (1/22). Some SmCCs showed focal expression of CK5/6 (9/25), a marker for the basal molecular subtype. Furthermore, expression of the retinoblastoma 1 (RB1) gene protein was lost in most of the bladder SmCCs (2/23). The patients' survival was significantly associated with cancer stage but did not show a significant difference between mixed and pure SmCCs. Compared with conventional UC at similar stages, SmCC had a worse prognosis only when patients developed metastatic diseases. In conclusion, bladder SmCC is an aggressive disease that is frequently present at an advanced stage. A fraction of SmCCs show a basal molecular subtype, which may underlie its good response to chemotherapy. Inactivation of the RB1 gene may be implicated in the oncogenesis of bladder SmCC.

MiR-422a regulates cellular metabolism and malignancy by targeting pyruvate dehydrogenase kinase 2 in gastric cancer

Increasing evidence indicates that dysregulation of microRNAs (miRNAs) plays a crucial role in human malignancies. Here, we showed that microRNA-422a (miR-422a) expression was dramatically downregulated in gastric cancer (GC) samples and cell lines compared with normal controls, and that its expression level was inversely related to tumor size and depth of infiltration. Functional studies revealed that the overexpression of miR-422a in GC tumor cells suppressed cell proliferation and migration, and drove a metabolic shift from aerobic glycolysis to oxidative phosphorylation. Mechanistic analysis suggested that miR-422a repressed pyruvate dehydrogenase kinase 2 (PDK2) to restore activity of the pyruvate dehydrogenase (PDH), the gatekeeping enzyme that catalyzes the decarboxylation of pyruvate to produce acetyl-CoA. Importantly, we further demonstrated that the mir-422a–PDK2 axis also influenced another metabolic pathway, de novo lipogenesis in cancer cells, and that it subsequently affected reactive oxygen species (ROS) and RB phosphorylation levels, ultimately resulting in cell cycle arrest in G1 phase. Our findings show that the miR-422a–PDK2 axis is an important mediator in metabolic reprogramming and a promising therapeutic target for antitumor treatment.

Epigenetic mechanisms in odontogenic tumors: A literature review

OBJECTIVE

Epigenetic mechanisms, such as DNA methylation, regulate important biological processes as gene expression and it was suggested that these phenomena play important roles in the carcinogenesis and tumor biology. The aim of this review is to provide the current state of knowledge about epigenetic alterations, focusing mainly on DNA methylation, reported in odontogenic tumors.

DESIGN

Literatures were searched based in the combination of the following keywords: odontogenic tumors, epigenetics, DNA methylation, histone modifications, non-coding RNA, microRNA, DNA methyltransferases. Electronic databases (Medline/PubMed, Scopus and Web of Science) were screened.

RESULTS

The analysis of epigenetic alterations in different tumors has rapidly increased; however, limited information is available about epigenetic mechanisms involved in the formation of odontogenic tumors. DNA methylation is the most studied epigenetic modification in these tumors and the participation of non-coding RNA's in odontogenic tumors has been recently addressed. Differential expression of DNA methyltransferases, altered DNA methylation patterns and aberrant expression of non-coding RNA's were reported in odontogenic tumors.

CONCLUSIONS

Current studies suggest epigenetics as an emerging mechanism, possibly implicated in etiopathogenesis of odontogenic tumors. Deeper understanding of the epigenetic abnormalities in these tumors could show potential applications as biomarkers or therapeutic possibilities in the future.

Detection of Aberrant DNA Methylation Patterns in the RB1 Gene

The retinoblastoma protein (pRb) plays a central role in the regulation of cell cycle by interaction with members of the E2F transcription factor family. As a tumor suppressor protein, pRb is frequently dysregulated in several major cancers. In addition to mutations, inactivation of pRb is also caused by epigenetic mechanisms including alterations of DNA methylation. There are three CpG islands located within the RB1 gene that encodes pRb that are closely associated with the regulation of pRb expression. Aberrant DNA methylation at the RB1 gene has been reported in sporadic retinoblastoma as well as other cancers including glioblastoma, hepatocellular carcinoma, and breast cancer. Recent studies have revealed that the RB1 gene is imprinted. Therefore, quantitative analysis is required to detect aberrations in DNA methylation associated with imprint deregulation. Pyrosequencing^® is considered as the method of choice for quantitative and reproducible analysis of DNA methylation with single base resolution. In this chapter, we provide a detailed protocol for the quantitative analysis of RB1 gene methylation using bisulfite Pyrosequencing^®.

Human Polyomaviruses: The Battle of Large and Small Tumor Antigens

About 40 years ago, the large and small tumor antigens (LT-Ag and sT-Ag) of the polyomavirus (PyVs) simian vacuolating virus 40 have been identified and characterized. To date, it is well known that all the discovered human PyVs (HPyVs) encode these 2 multifunctional and tumorigenic proteins, expressed at viral replication early stage. The 2 T-Ags are able to transform cells both in vitro and in vivo and seem to play a distinct role in the pathogenesis of some tumors in humans. In addition, they are involved in viral DNA replication, transcription, and virion assembly. This short review focuses on the structural and functional features of the HPyVs’ LT-Ag and sT-Ag, with special attention to their transforming properties.

Differential impact of RB status on E2F1 reprogramming in human cancer

The tumor suppressor protein retinoblastoma (RB) is mechanistically linked to suppression of transcription factor E2F1-mediated cell cycle regulation. For multiple tumor types, loss of RB function is associated with poor clinical outcome. RB action is abrogated either by direct depletion or through inactivation of RB function; however, the basis for this selectivity is unknown. Here, analysis of tumor samples and cell-free DNA from patients with advanced prostate cancer showed that direct RB loss was the preferred pathway of disruption in human disease. While RB loss was associated with lethal disease, RB-deficient tumors had no proliferative advantage and exhibited downstream effects distinct from cell cycle control. Mechanistically, RB loss led to E2F1 cistrome expansion and different binding specificity, alterations distinct from those observed after functional RB inactivation. Additionally, identification of protumorigenic transcriptional networks specific to RB loss that were validated in clinical samples demonstrated the ability of RB loss to differentially reprogram E2F1 in human cancers. Together, these findings not only identify tumor-suppressive functions of RB that are distinct from cell cycle control, but also demonstrate that the molecular consequence of RB loss is distinct from RB inactivation. Thus, these studies provide insight into how RB loss promotes disease progression, and identify new nodes for therapeutic intervention.

Advances in sarcoma gene mutations and therapeutic targets

Sarcomas are rare and complex malignancies that have been associated with a poor prognostic outcome. Over the last few decades, traditional treatment with surgery and/or chemotherapy has not significantly improved outcomes for most types of sarcomas. In recent years, there have been significant advances in the understanding of specific gene mutations that are important in driving the pathogenesis and progression of sarcomas. Identification of these new gene mutations, using next-generation sequencing and advanced molecular techniques, has revealed a range of potential therapeutic targets. This, in turn, may lead to the development of novel agents targeted to different sarcoma subtypes. In this review, we highlight the advances made in identifying sarcoma gene mutations, including those of p53, RB, PI3K and IDH genes, as well as novel therapeutic strategies aimed at utilizing these mutant genes. In addition, we discuss a number of preclinical studies and ongoing early clinical trials in sarcoma targeting therapies, as well as gene editing technology, which may provide a better choice for sarcoma patient management.

A viral Sm-class RNA base-pairs with mRNAs and recruits microRNAs to inhibit apoptosis

Viruses express several classes of non-coding RNAs; the functions and mechanisms by which most of these act are unknown. Herpesvirus saimiri, a γ-herpesvirus that establishes latency in the T cells of New World primates and has the ability to cause aggressive leukaemias and lymphomas in non-natural hosts, expresses seven small nuclear uracil-rich non-coding RNAs (called HSURs) in latently infected cells. These HSURs associate with Sm proteins, and share biogenesis and structural features with cellular Sm-class small nuclear RNAs. One of these HSURs (HSUR2) base-pairs with two host cellular microRNAs (miR-142-3p and miR-16) but does not affect their abundance or activity, which suggests that its interactions with them perform alternative functions. Here we show that HSUR2 also base-pairs with mRNAs in infected cells. We combined in vivo psoralen-mediated RNA-RNA crosslinking and high-throughput sequencing to identify the mRNAs targeted by HSUR2, which include mRNAs that encode retinoblastoma and factors involved in p53 signalling and apoptosis. We show that HSUR2 represses the expression of target mRNAs and that base-pairing between HSUR2 and miR-142-3p and miR-16 is essential for this repression, suggesting that HSUR2 recruits these two cellular microRNAs to its target mRNAs. Furthermore, we show that HSUR2 uses this mechanism to inhibit apoptosis. Our results uncover a role for this viral Sm-class RNA as a microRNA adaptor in the regulation of gene expression that follows precursor mRNA processing.

SKP2 Activation by Thyroid Hormone Receptor β2 Bypasses Rb-Dependent Proliferation in Rb-Deficient Cells

Germline RB1 mutations strongly predispose humans to cone precursor-derived retinoblastomas and strongly predispose mice to pituitary tumors, yet shared cell type-specific circuitry that sensitizes these different cell types to the loss of RB1 has not been defined. Here we show that the cell type-restricted thyroid hormone receptor isoform TRβ2 sensitizes to RB1 loss in both settings by antagonizing the widely expressed and tumor-suppressive TRβ1. TRβ2 promoted expression of the E3 ubiquitin ligase SKP2, a critical factor for RB1-mutant tumors, by enabling EMI1/FBXO5-dependent inhibition of SKP2 degradation. In RB1 wild-type neuroblastoma cells, endogenous Rb or ectopic TRβ2 was required to sustain SKP2 expression as well as cell viability and proliferation. These results suggest that in certain contexts, Rb loss enables TRβ1-dependent suppression of SKP2 as a safeguard against RB1-deficient tumorigenesis. TRβ2 counteracts TRβ1, thus disrupting this safeguard and promoting development of RB1-deficient malignancies. Cancer Res; 77(24); 6838-50. ©2017 AACR.

MiR-661 promotes tumor invasion and metastasis by directly inhibiting RB1 in non small cell lung cancer

BACKGROUND

Aberrant microRNA expression has been implicated in metastasis of cancers. MiR-661 accelerates proliferation and invasion of breast cancer and ovarian cancer, while impedes that of glioma. Its role in non small cell lung cancer (NSCLC) and underlying mechanism are worthy elucidation.

METHODS

Expression of miR-661 was measured with real-time PCR in both NSCLC tissues and cell lines. The effects of miR-661 on migration, invasion and metastasis capacity of NSCLC were evaluated using wound healing, transwell assay and animal models. Dual reporter luciferase assay and complementary experiments were performed to validate RB1 as a direct target of miR-661 for participation in the progression of NSCLC.

RESULTS

MiR-661 was upregulated in NSCLC tissues as compared to paired adjacent tissues and associated with shorter overall survival. Furthermore, miR-661 promoted proliferation, migration and metastasis of NSCLC. Then, we identified RB1 as a direct target of miR-661 through which miR-661 affected EMT process and metastasis of NSCLC. RB1 interacted with E2F1 and both could mediate EMT process in NSCLC.

CONCLUSION

MiR-661 promotes metastasis of NSCLC through RB/E2F1 signaling and EMT events, thus may serves as a negative prognostic factor and possible target for treatment of NSCLC patient.

Plasmacytoid Urothelial Carcinoma of the Urinary Bladder: A Clinicopathologic and Immunohistochemical Analysis of 49 Cases

OBJECTIVES

Plasmacytoid urothelial carcinoma (PUC) of the bladder is a rare histologic variant. We retrospectively analyzed a large series of bladder PUC from a single institution.

METHODS

The patients consisted of 44 men and five women with a mean age of 62 years (range, 45-86 years).

RESULTS

PUC was pure in 23 cases and mixed with other histologic types in 26 cases. All PUCs diffusely invaded the bladder wall. Most PUCs lacked immunoreactivity for the retinoblastoma (RB) gene protein (12/32) and E-cadherin (8/30). Of the 44 patients with follow-up information, 25 died of PUC at a mean of 23 months, whereas 19 patients were alive at a mean of 22 months.

CONCLUSIONS

Our findings support that bladder PUC is a highly aggressive disease. The lack of E-cadherin expression in PUCs may underlie the distinct discohesive histologic appearance, and abnormal function of the RB gene may be implicated in the development of PUC.

Bidirectional transcription of Linc00441 and RB1 via H3K27 modification-dependent way promotes hepatocellular carcinoma

The retinoblastoma gene (RB1), a known tumor-suppressor gene (TSG), was decreased in multiple cancers including hepatocellular carcinoma (HCC). Here we focused on the bidirectional transcripted long noncoding RNA (Linc00441) with neighbor gene RB1 to investigate whether Linc00441 is involved in the suppression of RB1 in HCC. We found that aberrant upregulated intranuclear Linc00441 was reversely correlated with RB1 expression in human HCC samples. The gain- and loss-of-function investigation revealed that Linc00441 could promote the proliferation of HCC cells in vitro and in vivo with an apoptosis suppression and cell cycle rearrangement. Furthermore, RNA pull-down assay indicated the decreased level of RB1 induced by Linc00441 was associated with the incidental methylation by DNMT3A recruited by Linc00441. On the contrary, the transcription factor (TCF-4) enhanced H3K27 acetylation and direct transcription factor for Linc00441 was responsible for the upregulation of Linc00441 in HCC. In conclusion, the epigenetic interaction between Linc00441 and bidirectional transcripted neighbor RB1 may be a de novo theory cutting-point for the inactivation of RB1 in HCC and may serve as targeting site for tumor therapy in the future.

Simvastatin and Atorvastatin inhibit DNA replication licensing factor MCM7 and effectively suppress RB-deficient tumors growth

Loss or dysfunction of tumor suppressor retinoblastoma (RB) is a common feature in various tumors, and contributes to cancer cell stemness and drug resistance to cancer therapy. However, the strategy to suppress or eliminate Rb-deficient tumor cells remains unclear. In the present study, we accidentally found that reduction of DNA replication licensing factor MCM7 induced more apoptosis in RB-deficient tumor cells than in control tumor cells. Moreover, after a drug screening and further studies, we demonstrated that statin drug Simvastatin and Atorvastatin were able to inhibit MCM7 and RB expressions. Further study showed that Simvastatin and Atorvastatin induced more chromosome breaks and gaps of Rb-deficient tumor cells than control tumor cells. In vivo results showed that Simvastatin and Atorvastatin significantly suppressed Rb-deficient tumor growth than control in xenograft mouse models. The present work demonstrates that ‘old' lipid-lowering drugs statins are novel weapons against RB-deficient tumors due to their effects on suppressing MCM7 protein levels.

Dosage-dependent copy number gains in E2f1 and E2f3 drive hepatocellular carcinoma

Disruption of the retinoblastoma (RB) tumor suppressor pathway, either through genetic mutation of upstream regulatory components or mutation of RB1 itself, is believed to be a required event in cancer. However, genetic alterations in the RB-regulated E2F family of transcription factors are infrequent, casting doubt on a direct role for E2Fs in driving cancer. In this work, a mutation analysis of human cancer revealed subtle but impactful copy number gains in E2F1 and E2F3 in hepatocellular carcinoma (HCC). Using a series of loss- and gain-of-function alleles to dial E2F transcriptional output, we have shown that copy number gains in E2f1 or E2f3b resulted in dosage-dependent spontaneous HCC in mice without the involvement of additional organs. Conversely, germ-line loss of E2f1 or E2f3b, but not E2f3a, protected mice against HCC. Combinatorial mapping of chromatin occupancy and transcriptome profiling identified an E2F1- and E2F3B-driven transcriptional program that was associated with development and progression of HCC. These findings demonstrate a direct and cell-autonomous role for E2F activators in human cancer.

LNDriver: identifying driver genes by integrating mutation and expression data based on gene-gene interaction network

BACKGROUND

Cancer is a complex disease which is characterized by the accumulation of genetic alterations during the patient's lifetime. With the development of the next-generation sequencing technology, multiple omics data, such as cancer genomic, epigenomic and transcriptomic data etc., can be measured from each individual. Correspondingly, one of the key challenges is to pinpoint functional driver mutations or pathways, which contributes to tumorigenesis, from millions of functional neutral passenger mutations.

RESULTS

In this paper, in order to identify driver genes effectively, we applied a generalized additive model to mutation profiles to filter genes with long length and constructed a new gene-gene interaction network. Then we integrated the mutation data and expression data into the gene-gene interaction network. Lastly, greedy algorithm was used to prioritize candidate driver genes from the integrated data. We named the proposed method Length-Net-Driver (LNDriver).

CONCLUSIONS

Experiments on three TCGA datasets, i.e., head and neck squamous cell carcinoma, kidney renal clear cell carcinoma and thyroid carcinoma, demonstrated that the proposed method was effective. Also, it can identify not only frequently mutated drivers, but also rare candidate driver genes.

Patients with retinoblastoma and chromosome 13q deletions have increased chemotherapy-related toxicities

BACKGROUND

A total of 5-10% of patients with retinoblastoma (RB) harbor deletion of the long arm (q) chromosome 13 (13q-). The treatment-related toxicities in this population have not been described.

METHODS

Sixty-eight RB patients on a single institutional protocol (RET5) from 2005 to 2010 were reviewed. Genetic screening identified 11 patients (seven female) with 13q-. Patients with early (Reese-Ellsworth [R-E] group I-III) disease (6/23 with 13q-) received eight courses of vincristine/carboplatin (VC). Patients with advanced (R-E group IV-V) bilateral disease (2/27 with 13q-) received two courses of vincristine/topotecan (VT) followed by nine courses of alternating VT/VC. Patients undergoing upfront enucleation received histopathology-based chemotherapy: intermediate risk (2/8 with 13q-) or high risk (1/10 with 13q-). Dose reductions were mandated for >7 day delay in two consecutive courses following hematologic toxicity. Grades 3 and 4 hematologic, infectious, and gastrointestinal toxicities were compared between RET5 patients with and without 13q-.

RESULTS

Demographics were similar between groups. When present, prolonged neutropenia (median 7 days, range 0-14 days) delayed chemotherapy and resulted in more frequent dose reductions among 13q- patients (5/11) than non-13q- patients (4/57) (P < 0.01). GI toxicity was similar between groups (5/11 13q- vs. 13/57 non-13q-; P = 0.14), but halted chemotherapy in one 13q- patient. Infectious complications and disease outcomes were similar between groups. At follow-up, all patients are alive (median 6.1 years, range 7.6 months-9.5 years).

CONCLUSIONS

13q- RB patients had a higher incidence of neutropenia requiring chemotherapy dose reductions, but did not have increased treatment failure.

Role of CDKN2C Copy Number in Sporadic Medullary Thyroid Carcinoma

BACKGROUND

The cyclin-dependent-kinase inhibitors (CDKN)/retinoblastoma (RB1) pathway has been implicated as having a role in medullary thyroid carcinoma (MTC) tumorigenesis. CDKN2C loss has been associated with RET-mediated MTC in humans but with minimal phenotypic correlation provided. The objective of this study was to evaluate the association between tumor RET mutation status, CDKN2C loss, and aggressiveness of MTC in a cohort of patients with sporadic disease.

METHODS

Tumors from patients with sporadic MTC treated at a single institution were evaluated for somatic RET^M918T mutation and CDKN2C copy number loss. These variables were compared to patient demographics, pathology detail, clinical course, and disease-specific and overall survival.

RESULTS

Sixty-two MTC cases with an initial surgery date ranging from 1983 to 2009 met the inclusion criteria, of whom 36 (58%) were male. The median age at initial surgery was 53 years (range 22-81 years). The median tumor size was 30 mm (range 6-145 mm) with 29 (57%) possessing extrathyroidal extension. Nodal and/or distant metastasis at presentation was found in 47/60 (78%) and 12/61 (20%) patients, respectively. Median follow-up time was 10.5 years (range 1.1-27.8 years) for the censored observations. The presence of CDKN2C loss was associated with worse M stage and overall AJCC stage. Median overall survival of patients with versus without CDKN2C loss was 4.14 [confidence interval (CI) 1.93-NA] versus 18.27 [CI 17.24-NA] years (p < 0.0001). Median overall survival of patients with a combined somatic RET^M918T mutation and CDKN2C loss versus no somatic RET^M918T mutation and CDKN2C loss versus somatic RET^M918T mutation and CDKN2C 2N versus no somatic RET^M918T mutation and CDKN2C 2N was 2.38 [CI 1.67-NA] years versus 10.81 [CI 2.46-NA] versus 17.24 [CI 9.82-NA] versus not reached [CI 13.46-NA] years (p < 0.0001).

CONCLUSIONS

The detection of somatic CDKN2C loss is associated with the presence of distant metastasis at presentation as well decreased overall survival, a relationship enhanced by concomitant RET^M918T mutation. Further defining the genes involved in the progression of metastatic MTC will be an important step toward identifying pathways of disease progression and new therapeutic targets.

Switching off malignant mesothelioma: exploiting the hypoxic microenvironment

Malignant mesotheliomas are aggressive, asbestos-related cancers with poor patient prognosis, typically arising in the mesothelial surfaces of tissues in pleural and peritoneal cavity. The relative unspecific symptoms of mesotheliomas, misdiagnoses, and lack of precise targeted therapies call for a more critical assessment of this disease. In the present review, we categorize commonly identified genomic aberrations of mesotheliomas into their canonical pathways and discuss targeting these pathways in the context of tumor hypoxia, a hallmark of cancer known to render solid tumors more resistant to radiation and most chemo-therapy. We then explore the concept that the intrinsic hypoxic microenvironment of mesotheliomas can be Achilles' heel for targeted, multimodal therapeutic intervention.

miR-1297 promotes cell proliferation by inhibiting RB1 in liver cancer

Liver cancer is the one of the most common causes of cancer-associated mortality worldwide. MicroRNAs (miRNAs or miRs) are important in various types of cancer, including liver cancer. In the present study, with miRNA expression profile data obtained from the Gene Expression Omnibus database, three independent methods were used to investigate the miRNAs that are involved in liver carcinogenesis, including Fisher's exact test, t-test and Wilcoxon test. Five differentially expressed miRNAs were identified. Among them, miR-1297 drew specific attention. Target gene analysis and Ingenuity Pathway Analysis revealed its potential impact on cell death and cell cycle. Cell Counting Kit-8 proliferation assay indicated that the HepG2 cell proliferation was promoted by miR-1297, while miR-1297 inhibitor could significantly inhibit the proliferation of HepG2 cells. Luciferase assays confirmed that miR-1297 directly bound to the 3'-untranslated region of retinoblastoma (RB)1, and western blotting demonstrated that miR-1297 suppressed the expression of RB1 at the protein level. RB1 is involved in the regulation of the human cell cycle pathway. It is possible that miR-1297 contributes to the carcinogenesis of liver cancer via downregulation of the tumor-suppressor gene RB1. Our results suggest that miR-1297 may serve as a potential therapeutic target of liver cancer.

Chromothripsis Is a Recurrent Genomic Abnormality in High-Risk Myelodysplastic Syndromes

To explore novel genetic abnormalities occurring in myelodysplastic syndromes (MDS) through an integrative study combining array-based comparative genomic hybridization (aCGH) and next-generation sequencing (NGS) in a series of MDS and MDS/myeloproliferative neoplasms (MPN) patients. 301 patients diagnosed with MDS (n = 240) or MDS/MPN (n = 61) were studied at the time of diagnosis. A genome-wide analysis of DNA copy number abnormalities was performed. In addition, a mutational analysis of DNMT3A, TET2, RUNX1, TP53 and BCOR genes was performed by NGS in selected cases. 285 abnormalities were identified in 71 patients (23.6%). Three high-risk MDS cases (1.2%) displayed chromothripsis involving exclusively chromosome 13 and affecting some cancer genes: FLT3, BRCA2 and RB1. All three cases carried TP53 mutations as revealed by NGS. Moreover, in the whole series, the integrative analysis of aCGH and NGS enabled the identification of cryptic recurrent deletions in 2p23.3 (DNMT3A; n = 2.8%), 4q24 (TET2; n = 10%) 17p13 (TP53; n = 8.5%), 21q22 (RUNX1; n = 7%), and Xp11.4 (BCOR; n = 2.8%), while mutations in the non-deleted allele where found only in DNMT3A (n = 1), TET2 (n = 3), and TP53 (n = 4). These cryptic abnormalities were detected mainly in patients with normal (45%) or non-informative (15%) karyotype by conventional cytogenetics, except for those with TP53 deletion and mutation (15%), which had a complex karyotype. In addition to well-known copy number defects, the presence of chromothripsis involving chromosome 13 was a novel recurrent change in high-risk MDS patients. Array CGH analysis revealed the presence of cryptic abnormalities in genomic regions where MDS-related genes, such as TET2, DNMT3A, RUNX1 and BCOR, are located.

Immunohistochemistry of apoptosis-related proteins in retinoblastoma

Retinoblastoma is the most common intraocular malignant neoplasia during childhood and results from the partial or total inactivity of the retinoblastoma protein (pRb). In the absence of pRb, the E2F transcription factors increase the levels of cell cycle proteins as well as some pro-apoptotic proteins. We intended to study the immunohistochemistry profile of apoptotic-related proteins in retinoblastoma. We also evaluated the association between the expression of apoptotic protein and stage of tumor or survivor after a 5year follow up. Apoptosis-related proteins (Apaf-1, Bak, Bax, Bcl-2, Bcl-xL, Bim-long, MDM2, p53, pro-caspase-3, PUMA, Smac/DIABLO and cleaved caspase-3) were evaluated using immunohistochemistry on tissue microarrays which contained samples of retinoblastoma tumors taken from ninety-three patients without any treatment previous to surgery. The immunohistochemistry reactions were evaluated using an optical microscope as well as the ACIS III^® platform. The pro-apoptotic proteins (APAF-1, Bax, p53, PUMA, Smac/DIABLO) were more frequently expressed than the anti-apoptotic proteins (Bcl-2, Bcl-xL and MDM2). The protein Bcl-xL had a negative correlation with cleaved caspase-3, a marker of cell apoptosis. Bcl-xL may be implicated in an apoptosis block.

Osteosarcoma: prognosis plateau warrants retinoblastoma pathway targeted therapy

Osteosarcoma (OS) is the most common primary bone cancer in children and adolescents, affecting ~560 young patients in the United States annually. The term OS describes a diverse array of subtypes with varying prognoses, but the majority of tumors are high grade and aggressive. Perhaps because the true etiology of these aggressive tumors remains unknown, advances in OS treatment have reached a discouraging plateau, with only incremental improvements over the past 40 years. Thus, research surrounding the pathogenesis of OS is essential, as it promises to unveil novel therapeutic targets that can attack tumor cells with greater specificity and lower toxicity. Among the candidate molecular targets in OS, the retinoblastoma (RB) pathway demonstrates the highest frequency of inactivation and thus represents a particularly promising avenue for molecular targeted therapy. This review examines the present thinking and practices in OS treatment and specifically highlights the relevance of the RB pathway in osteosarcomagenesis. Through further investigation into RB pathway-related novel therapeutic targets, we believe that a near-term breakthrough in improved OS prognosis is possible.