Kinetic Characterization of ASXL1/2-Mediated Allosteric Regulation of the BAP1 Deubiquitinase.

BAP1 is an ubiquitin hydrolase whose deubiquitinase activity is mediated by polycomb group-like protein ASXL2. Cancer-related BAP1 mutations/deletions lead to loss-of-function by targeting the catalytic ubiquitin C-terminal hydrolase (UCH) or UCH37-like domain (ULD) domains of BAP1, and the latter disrupts binding to ASXL2, an obligate partner for BAP1 enzymatic activity. However, the biochemical and biophysical properties of domains involved in forming the enzymatically active complex are unknown. Here, we report the molecular dynamics, kinetics, and stoichiometry of these interactions. We demonstrate that interactions between BAP1 and ASXL2 are direct, specific, and stable to biochemical and biophysical manipulations as detected by isothermal titration calorimetry (ITC), GST association, and optical biosensor assays. Association of the ASXL2-AB box greatly stimulates BAP1 activity. A stable ternary complex is formed, comprised of the BAP1-UCH, BAP1-ULD, and ASXL2-AB domains. Stoichiometric analysis revealed that one molecule of the ULD domain directly interacts with one molecule of the AB box. Real-time kinetic analysis of the ULD/AB protein complex to the BAP1-UCH domain, based on surface plasmon resonance, indicated that formation of the ULD/AB complex with the UCH domain is a single-step event with fast association and slow dissociation rates. In vitro experiments validated in cells that the ASXL-AB box directly regulates BAP1 activity. IMPLICATIONS: Collectively, these data elucidate molecular interactions between specific protein domains regulating BAP1 deubiquitinase activity, thus establishing a foundation for small-molecule approaches to reactivate latent wild-type BAP1 catalytic activity in BAP1-mutant cancers.

LIMD2 Regulates Key Steps of Metastasis Cascade in Papillary Thyroid Cancer Cells via MAPK Crosstalk.

Although papillary thyroid carcinoma (PTC) has a good prognosis, 20-90% of patients show metastasis to regional lymph nodes and 10-15% of patients show metastasis to distant sites. Metastatic disease represents the main clinical challenge that impacts survival rate. We previously showed that LIMD2 was a novel metastasis-associated gene. In this study, to interrogate the role of LIMD2 in cancer invasion and metastasis, we used CRISPR-mediated knockout (KO) of LIMD2 in PTC cells (BCPAP and TPC1). Western blot and high-content screening (HCS) analysis confirmed functional KO of LIMD2. LIMD2 KO reduced in vitro invasion and migration. Ultrastructural analyses showed that cell polarity and mitochondria function and morphology were restored in LIMD2 KO cells. To unveil the signals supervising these phenotypic changes, we employed phospho-protein array. Several members of the MAPK superfamily showed robust reduction in phosphorylation. A Venn diagram displayed the overlap of kinases with reduced phosphorylation in both cell lines and showed that they were able to initiate or sustain the epithelial-mesenchymal transition (EMT) and DNA damage checkpoint. Flow cytometry and HCS validation analyses further corroborated the phospho-protein array data. Collectively, our findings show that LIMD2 enhances phosphorylation of kinases associated with EMT and invasion. Through cooperation with different kinases, it contributes to the increased genomic instability that ultimately promotes PTC progression.

Inactivation of Bap1 Cooperates with Losses of Nf2 and Cdkn2a to Drive the Development of Pleural Malignant Mesothelioma in Conditional Mouse Models.

Pleural malignant mesothelioma is a therapy-resistant cancer affecting the serosal lining of the thoracic cavity. Mutations/deletions of BAP1, CDKN2A, and NF2 are the most frequent genetic lesions in human malignant mesothelioma. We introduced various combinations of these deletions in the pleura of conditional knockout (CKO) mice, focusing on the contribution of Bap1 loss. While homozygous CKO of Bap1, Cdkn2a, or Nf2 alone gave rise to few or no malignant mesotheliomas, inactivation of Bap1 cooperated with loss of either Nf2 or Cdkn2a to drive development of malignant mesothelioma in approximately 20% of double-CKO mice, and a high incidence (22/26, 85%) of malignant mesotheliomas was observed in Bap1;Nf2;Cdkn2a (triple)-CKO mice. Malignant mesothelioma onset was rapid in triple-CKO mice, with a median survival of only 12 weeks, and malignant mesotheliomas from these mice were consistently high-grade and invasive. Adenoviral-Cre treatment of normal mesothelial cells from Bap1;Nf2;Cdkn2a CKO mice, but not from mice with knockout of one or any two of these genes, resulted in robust spheroid formation in vitro, suggesting that mesothelial cells from Bap1;Nf2;Cdkn2a mice have stem cell-like potential. RNA-seq analysis of malignant mesotheliomas from triple-CKO mice revealed enrichment of genes transcriptionally regulated by the polycomb repressive complex 2 (PRC2) and others previously implicated in known Bap1-related cellular processes. These data demonstrate that somatic inactivation of Bap1, Nf2, and Cdkn2a results in rapid, aggressive malignant mesotheliomas, and that deletion of Bap1 contributes to tumor development, in part, by loss of PRC2-mediated repression of tumorigenic target genes and by acquisition of stem cell potential, suggesting a potential avenue for therapeutic intervention. SIGNIFICANCE: Combinatorial deletions of Bap1, Nf2, and Cdkn2a result in aggressive mesotheliomas, with Bap1 loss contributing to tumorigenesis by circumventing PRC2-mediated repression of oncogenic target genes.

Novel immediate/sustained-release formulation of acetaminophen-ibuprofen combination (Paxerol®) for severe nocturia associated with overactive bladder: A multi-center, randomized, double blinded, placebo-controlled, 4-arm trial.

AIM: To determine short-term efficacy and safety of Paxerol®, novel immediate:sustained (50%:50%) release tablets containing 325 mg acetaminophen and 150 mg ibuprofen per tablet. METHODS: One of three dose levels, corresponding to the amounts in 1, 2, and 3 tablets, of Paxerol and placebo were administered for 14 consecutive days to patients with severe nocturia (defined in this study as an average nocturnal voids [NV] ≥2.5) associated with overactive bladder (OAB). Changes in NV, as well as Nocturia Quality of Life (NQOL), duration of first uninterrupted sleep (DFUS), and total hours of nightly sleep (THNS) associated with treatment were assessed. Short-term safety/tolerability was assessed throughout the study and for at least 30 days post-treatment. RESULTS: Paxerol at all three doses reduced NV to a greater degree than placebo (average NV -1.1, -1.4, -1.3 voids for low, mid, and high doses, respectively, vs -0.3 void for placebo). NQOL and THNS were similar between baseline and treatment values in all four groups. There were also no between-group differences. Paxerol at high dose tended to (although not statistical significantly) increase DFUS to a greater degree than placebo (1.2 vs 0.4 h, P = 0.057). There were no treatment related adverse events in any of the four groups. CONCLUSIONS: This study demonstrates short-term efficacy and short-term safety of Paxerol in patients with severe nocturia associated with OAB. The results warrant further investigation of the long-term efficacy and safety of Paxerol in larger patient populations.

Inactivation of Tp53 and Pten drives rapid development of pleural and peritoneal malignant mesotheliomas.

Malignant mesothelioma (MM) is a therapy-resistant cancer arising primarily from the lining of the pleural and peritoneal cavities. The most frequently altered genes in human MM are cyclin-dependent kinase inhibitor 2A (CDKN2A), which encodes components of the p53 (p14ARF) and RB (p16INK4A) pathways, BRCA1-associated protein 1 (BAP1), and neurofibromatosis 2 (NF2). Furthermore, the p53 gene (TP53) itself is mutated in ~15% of MMs. In many MMs, the PI3K-PTEN-AKT-mTOR signaling node is hyperactivated, which contributes to tumor cell survival and therapeutic resistance. Here, we demonstrate that the inactivation of both Tp53 and Pten in the mouse mesothelium is sufficient to rapidly drive aggressive MMs. PtenL/L ;Tp53L/L mice injected intraperitoneally or intrapleurally with adenovirus-expressing Cre recombinase developed high rates of peritoneal and pleural MMs (92% of mice with a median latency of 9.4 weeks and 56% of mice with a median latency of 19.3 weeks, respectively). MM cells from these mice showed consistent activation of Akt-mTor signaling, chromosome breakage or aneuploidy, and upregulation of Myc; occasional downregulation of Bap1 was also observed. Collectively, these findings suggest that when Pten and Tp53 are lost in combination in mesothelial cells, DNA damage is not adequately repaired and genomic instability is widespread, whereas the activation of Akt due to Pten loss protects genomically damaged cells from apoptosis, thereby increasing the likelihood of tumor formation. Additionally, the mining of an online dataset (The Cancer Genome Atlas) revealed codeletions of PTEN and TP53 and/or CDKN2A/p14ARF in ~25% of human MMs, indicating that cooperative losses of these genes contribute to the development of a significant proportion of these aggressive neoplasms and suggesting key target pathways for therapeutic intervention.

LIMD2 Is Overexpressed in BRAF V600E-Positive Papillary Thyroid Carcinomas and Matched Lymph Node Metastases.

We previously described that LIM domain containing 2 (LIMD2) overexpression was closely correlated with metastatic process in papillary thyroid carcinoma (PTC). We here evaluated the expression of LIMD2 in a series of non-metastatic and metastatic PTC and their matched lymph node metastases via immunohistochemistry. LIMD2 was expressed in 74 (81%) of primary PTC and 35 (95%) of lymph node metastases. Sub-analysis performed in 37 matched samples demonstrated that in four cases, LIMD2 is expressed in lymph node metastases, while it is not expressed in primary tumors. Moreover, in eight cases, the staining intensity of LIMD2 was stronger in the patient-matched lymph node metastases than in the primary tumors. Next, the expression of LIMD2 was correlated with clinical pathological parameters and BRAF V600E and RET/PTC mutational status. The expression of LIMD2 in primary tumors was correlated with the presence of BRAF V600E mutation (P = 0.0338). Western blot analysis in thyroid cell lines demonstrated that LIMD2 is expressed in two PTC cell lines, while it is not expressed in normal thyroid and follicular thyroid carcinoma cell lines. Importantly, its expression was higher in a PTC cell line that harbors BRAF V600E mutation than in a PTC cell line that harbors RET/PTC1. The available genomic profiling data generated by The Cancer Genome Atlas Research Network confirmed that LIMD2 expression is higher in BRAF-like PTC samples. Our data suggest that LIMD2 may play an important role in the metastatic process of PTC, predominantly in BRAF V600E-positive tumors.

Characterization of Coding/Noncoding Variants for SHROOM3 in Patients with CKD.

Background Interpreting genetic variants is one of the greatest challenges impeding analysis of rapidly increasing volumes of genomic data from patients. For example, SHROOM3 is an associated risk gene for CKD, yet causative mechanism(s) of SHROOM3 allele(s) are unknown.Methods We used our analytic pipeline that integrates genetic, computational, biochemical, CRISPR/Cas9 editing, molecular, and physiologic data to characterize coding and noncoding variants to study the human SHROOM3 risk locus for CKD.Results We identified a novel SHROOM3 transcriptional start site, which results in a shorter isoform lacking the PDZ domain and is regulated by a common noncoding sequence variant associated with CKD (rs17319721, allele frequency: 0.35). This variant disrupted allele binding to the transcription factor TCF7L2 in podocyte cell nuclear extracts and altered transcription levels of SHROOM3 in cultured cells, potentially through the loss of repressive looping between rs17319721 and the novel start site. Although common variant mechanisms are of high utility, sequencing is beginning to identify rare variants involved in disease; therefore, we used our biophysical tools to analyze an average of 112,849 individual human genome sequences for rare SHROOM3 missense variants, revealing 35 high-effect variants. The high-effect alleles include a coding variant (P1244L) previously associated with CKD (P=0.01, odds ratio=7.95; 95% CI, 1.53 to 41.46) that we find to be present in East Asian individuals at an allele frequency of 0.0027. We determined that P1244L attenuates the interaction of SHROOM3 with 14-3-3, suggesting alterations to the Hippo pathway, a known mediator of CKD.Conclusions These data demonstrate multiple new SHROOM3-dependent genetic/molecular mechanisms that likely affect CKD.

MSX1-Induced Neural Crest-Like Reprogramming Promotes Melanoma Progression.

Melanoma cells share many biological properties with neural crest stem cells. Here we show that the homeodomain transcription factor MSX1, which is significantly correlated with melanoma disease progression, reprograms melanocytes and melanoma cells toward a neural crest precursor-like state. MSX1-reprogrammed normal human melanocytes express the neural crest marker p75 and become multipotent. MSX1 induces a phenotypic switch in melanoma, which is characterized by an oncogenic transition from an E-cadherin-high nonmigratory state toward a ZEB1-high invasive state. ZEB1 up-regulation is responsible for the MSX1-induced migratory phenotype in melanoma cells. Depletion of MSX1 significantly inhibits melanoma metastasis in vivo. These results show that neural crest-like reprogramming achieved by a single factor is a critical process for melanoma progression.

Familial and Somatic BAP1 Mutations Inactivate ASXL1/2-Mediated Allosteric Regulation of BAP1 Deubiquitinase by Targeting Multiple Independent Domains.

Deleterious mutations of the ubiquitin carboxy-terminal hydrolase BAP1 found in cancers are predicted to encode inactive truncated proteins, suggesting that loss of enzyme function is a primary tumorigenic mechanism. However, many tumors exhibit missense mutations or in-frame deletions or insertions, often outside the functionally critical UCH domain in this tumor suppressor protein. Thus, precisely how these mutations inactivate BAP1 is unknown. Here, we show how these mutations affect BAP1 interactions with the Polycomb group-like protein, ASXL2, using combinations of computational modeling technology, molecular biology, and in vitro reconstitution biochemistry. We found that the BAP1-ASXL2 interaction is direct and high affinity, occurring through the ASXH domain of ASXL2, an obligate partner for BAP1 enzymatic activity. The ASXH domain was the minimal domain for binding the BAP1 ULD domain, and mutations on the surfaces of predicted helices of ASXH abolished BAP1 association and stimulation of BAP1 enzymatic activity. The BAP1-UCH, BAP1-ULD, and ASXH domains formed a cooperative stable ternary complex required for deubiquitination. We defined four classes of alterations in BAP1 outside the UCH domain, each failing to productively recruit ASXH to the wild-type BAP1 catalytic site via the ULD, resulting in loss of BAP1 ubiquitin hydrolase activity. Our results indicate that many BAP1 mutations act allosterically to inhibit ASXH binding, thereby leading to loss of enzyme activity. Small-molecule approaches to reactivate latent wild-type UCH activity of these mutants might be therapeutically viable.Significance: Combined computational and biochemical approaches demonstrate that the BAP1-ASXL2 interaction is direct and high affinity and that many BAP1 mutations act allosterically to inhibit BAP1-ASXL2 binding. Cancer Res; 78(5); 1200-13. ©2017 AACR.

ARID1A-mutated ovarian cancers depend on HDAC6 activity.

ARID1A, encoding a subunit of the SWI/SNF chromatin-remodelling complex, is the most frequently mutated epigenetic regulator across all human cancers. ARID1A and TP53 mutations are typically mutually exclusive. Therapeutic approaches that correlate with this genetic characteristic remain to be explored. Here, we show that HDAC6 activity is essential in ARID1A-mutated ovarian cancers. Inhibition of HDAC6 activity using a clinically applicable small-molecule inhibitor significantly improved the survival of mice bearing ARID1A-mutated tumours. This correlated with the suppression of growth and dissemination of ARID1A-mutated, but not wild-type, tumours. The dependence on HDAC6 activity in ARID1A-mutated cells correlated with a direct transcriptional repression of HDAC6 by ARID1A. HDAC6 inhibition selectively promoted apoptosis of ARID1A-mutated cells. HDAC6 directly deacetylates Lys120 of p53, a pro-apoptotic post-translational modification. Thus, ARID1A mutation inactivates the apoptosis-promoting function of p53 by upregulating HDAC6. Together, these results indicate that pharmacological inhibition of HDAC6 is a therapeutic strategy for ARID1A-mutated cancers.

Bap1 Is a Bona Fide Tumor Suppressor: Genetic Evidence from Mouse Models Carrying Heterozygous Germline Bap1 Mutations.

Individuals harboring inherited heterozygous germline mutations in BAP1 are predisposed to a range of benign and malignant tumor types, including malignant mesothelioma, melanoma, and kidney carcinoma. However, evidence to support a tumor-suppressive role for BAP1 in cancer remains contradictory. To test experimentally whether BAP1 behaves as a tumor suppressor, we monitored spontaneous tumor development in three different mouse models with germline heterozygous mutations in Bap1, including two models in which the knock-in mutations are identical to those reported in human BAP1 cancer syndrome families. We observed spontaneous malignant tumors in 54 of 93 Bap1-mutant mice (58%) versus 4 of 43 (9%) wild-type littermates. All three Bap1-mutant models exhibited a high incidence and similar spectrum of neoplasms, including ovarian sex cord stromal tumors, lung and mammary carcinomas, and spindle cell tumors. Notably, we also observed malignant mesotheliomas in two Bap1-mutant mice, but not in any wild-type animals. We further confirmed that the remaining wild-type Bap1 allele was lost in both spontaneous ovarian tumors and mesotheliomas, resulting in the loss of Bap1 expression. Additional studies revealed that asbestos exposure induced a highly significant increase in the incidence of aggressive mesotheliomas in the two mouse models carrying clinically relevant Bap1 mutations compared with asbestos-exposed wild-type littermates. Collectively, these findings provide genetic evidence that Bap1 is a bona fide tumor suppressor gene and offer key insights into the contribution of carcinogen exposure to enhanced cancer susceptibility. Cancer Res; 76(9); 2836-44. ©2016 AACR.

Germline BAP1 Mutational Landscape of Asbestos-Exposed Malignant Mesothelioma Patients with Family History of Cancer.

Heritable mutations in the BAP1 tumor suppressor gene predispose individuals to mesothelioma and other cancers. However, a large-scale assessment of germline BAP1 mutation incidence and associated clinical features in mesothelioma patients with a family history of cancer has not been reported. Therefore, we examined the germline BAP1 mutation status of 150 mesothelioma patients with a family history of cancer, 50 asbestos-exposed control individuals with a family history of cancers other than mesothelioma, and 153 asbestos-exposed individuals without familial cancer. No BAP1 alterations were found in control cohorts, but were identified in nine of 150 mesothelioma cases (6%) with a family history of cancer. Alterations among these cases were characterized by both missense and frameshift mutations, and enzymatic activity of BAP1 missense mutants was decreased compared with wild-type BAP1. Furthermore, BAP1 mutation carriers developed mesothelioma at an earlier age that was more often peritoneal than pleural (five of nine) and exhibited improved long-term survival compared to mesothelioma patients without BAP1 mutations. Moreover, many tumors harboring BAP1 germline mutations were associated with BAP1 syndrome, including mesothelioma and ocular/cutaneous melanomas, as well as renal, breast, lung, gastric, and basal cell carcinomas. Collectively, these findings suggest that mesothelioma patients presenting with a family history of cancer should be considered for BAP1 genetic testing to identify those individuals who might benefit from further screening and routine monitoring for the purpose of early detection and intervention.

An evolutionarily conserved DNA architecture determines target specificity of the TWIST family bHLH transcription factors.

Basic helix-loop-helix (bHLH) transcription factors recognize the canonical E-box (CANNTG) to regulate gene transcription; however, given the prevalence of E-boxes in a genome, it has been puzzling how individual bHLH proteins selectively recognize E-box sequences on their targets. TWIST is a bHLH transcription factor that promotes epithelial-mesenchymal transition (EMT) during development and tumor metastasis. High-resolution mapping of TWIST occupancy in human and Drosophila genomes reveals that TWIST, but not other bHLH proteins, recognizes a unique double E-box motif with two E-boxes spaced preferentially by 5 nucleotides. Using molecular modeling and binding kinetic analyses, we found that the strict spatial configuration in the double E-box motif aligns two TWIST-E47 dimers on the same face of DNA, thus providing a high-affinity site for a highly stable intramolecular tetramer. Biochemical analyses showed that the WR domain of TWIST dimerizes to mediate tetramer formation, which is functionally required for TWIST-induced EMT. These results uncover a novel mechanism for a bHLH transcription factor to recognize a unique spatial configuration of E-boxes to achieve target specificity. The WR-WR domain interaction uncovered here sets an example of target gene specificity of a bHLH protein being controlled allosterically by a domain outside of the bHLH region.

Structure and specificity of the bacterial cysteine methyltransferase effector NleE suggests a novel substrate in human DNA repair pathway.

Enteropathogenic E. coli (EPEC) and related enterobacteria rely on a type III secretion system (T3SS) effector NleE to block host NF-κB signaling. NleE is a first in class, novel S-adenosyl-L-methionine (SAM)-dependent methyltransferase that methylates a zinc-coordinating cysteine in the Npl4-like Zinc Finger (NZF) domains in TAB2/3 adaptors in the NF-κB pathway, but its mechanism of action and other human substrates are unknown. Here we solve crystal structure of NleE-SAM complex, which reveals a methyltransferase fold different from those of known ones. The SAM, cradled snugly at the bottom of a deep and narrow cavity, adopts a unique conformation ready for nucleophilic attack by the methyl acceptor. The substrate NZF domain can be well docked into the cavity, and molecular dynamic simulation indicates that Cys673 in TAB2-NZF is spatially and energetically favorable for attacking the SAM. We further identify a new NleE substrate, ZRANB3, that functions in PCNA binding and remodeling of stalled replication forks at the DNA damage sites. Specific inactivation of the NZF domain in ZRANB3 by NleE offers a unique opportunity to suggest that ZRANB3-NZF domain functions in DNA repair processes other than ZRANB3 recruitment to DNA damage sites. Our analyses suggest a novel and unexpected link between EPEC infection, virulence proteins and genome integrity.

Germline mutation of Bap1 accelerates development of asbestos-induced malignant mesothelioma.

Malignant mesotheliomas are highly aggressive tumors usually caused by exposure to asbestos. Germline-inactivating mutations of BAP1 predispose to mesothelioma and certain other cancers. However, why mesothelioma is the predominate malignancy in some BAP1 families and not others, and whether exposure to asbestos is required for development of mesothelioma in BAP1 mutation carriers are not known. To address these questions experimentally, we generated a Bap1(+/-) knockout mouse model to assess its susceptibility to mesothelioma upon chronic exposure to asbestos. Bap1(+/-) mice exhibited a significantly higher incidence of asbestos-induced mesothelioma than wild-type (WT) littermates (73% vs. 32%, respectively). Furthermore, mesotheliomas arose at an accelerated rate in Bap1(+/-) mice than in WT animals (median survival, 43 weeks vs. 55 weeks after initial exposure, respectively) and showed increased invasiveness and proliferation. No spontaneous mesotheliomas were seen in unexposed Bap1(+/-) mice followed for up to 87 weeks of age. Mesothelioma cells from Bap1(+/-) mice showed biallelic inactivation of Bap1, consistent with its proposed role as a recessive cancer susceptibility gene. Unlike in WT mice, mesotheliomas from Bap1(+/-) mice did not require homozygous loss of Cdkn2a. However, normal mesothelial cells and mesothelioma cells from Bap1(+/-) mice showed downregulation of Rb through a p16(Ink4a)-independent mechanism, suggesting that predisposition of Bap1(+/-) mice to mesothelioma may be facilitated, in part, by cooperation between Bap1 and Rb. Drawing parallels to human disease, these unbiased genetic findings indicate that BAP1 mutation carriers are predisposed to the tumorigenic effects of asbestos and suggest that high penetrance of mesothelioma requires such environmental exposure.

Snail recruits Ring1B to mediate transcriptional repression and cell migration in pancreatic cancer cells.

Transcriptional repressor Snail is a master regulator of epithelial-mesenchymal transition (EMT), yet the epigenetic mechanism governing Snail to induce EMT is not well understood. Here, we report that in pancreatic ductal adenocarcinoma (PDAC), elevated levels of the ubiquitin E3 ligase Ring1B and Snail, along with elevated monoubiquitination of H2A at K119 (H2AK119Ub1), are highly correlated with poor survival. Mechanistic investigations identified Ring1B as a Snail-interacting protein and showed that the carboxyl zinc fingers of Snail recruit Ring1B and its paralog Ring1A to repress its target promoters. Simultaneous depletion of Ring1A and Ring1B in pancreatic cancer cells decreased Snail binding to the target chromatin, abolished H2AK119Ub1 modification, and thereby compromised Snail-mediated transcriptional repression and cell migration. We found that Ring1B and the SNAG-associated chromatin modifier EZH2 formed distinct protein complexes with Snail and that EZH2 was required for Snail-Ring1A/B recruitment to the target promoter. Collectively, our results unravel an epigenetic mechanism underlying transcriptional repression by Snail, suggest Ring1A/B as a candidate therapeutic target, and identify H2AK119Ub1 as a potential biomarker for PDAC diagnosis and prognosis.

LIMD2 is a small LIM-only protein overexpressed in metastatic lesions that regulates cell motility and tumor progression by directly binding to and activating the integrin-linked kinase.

Proteins that communicate signals from the cytoskeleton to the nucleus are prime targets for effectors of metastasis as they often transduce signals regulating adhesion, motility, and invasiveness. LIM domain proteins shuttle between the cytoplasm and the nucleus, and bind to partners in both compartments, often coupling changes in gene expression to extracellular cues. In this work, we characterize LIMD2, a mechanistically undefined LIM-only protein originally found to be overexpressed in metastatic lesions but absent in the matched primary tumor. LIMD2 levels in fresh and archival tumors positively correlate with cell motility, metastatic potential, and grade, including bladder, melanoma, breast, and thyroid tumors. LIMD2 directly contributes to these cellular phenotypes as shown by overexpression, knockdown, and reconstitution experiments in cell culture models. The solution structure of LIMD2 that was determined using nuclear magnetic resonance revealed a classic LIM-domain structure that was highly related to LIM1 of PINCH1, a core component of the integrin-linked kinase-parvin-pinch complex. Structural and biochemical analyses revealed that LIMD2 bound directly to the kinase domain of integrin-linked kinase (ILK) near the active site and strongly activated ILK kinase activity. Cells that were null for ILK failed to respond to the induction of invasion by LIMD2. This strongly suggests that LIMD2 potentiates its biologic effects through direct interactions with ILK, a signal transduction pathway firmly linked to cell motility and invasion. In summary, LIMD2 is a new component of the signal transduction cascade that links integrin-mediated signaling to cell motility/metastatic behavior and may be a promising target for controlling tumor spread.

MAS promoter regulation: a role for Sry and tyrosine nitration of the KRAB domain of ZNF274 as a feedback mechanism.

The ACE2 (angiotensin-converting enzyme 2)/Ang-(1-7) [angiotensin-(1-7)]/MAS axis of the RAS (renin-angiotensin system) has emerged as a pathway of interest in treating both cardiovascular disorders and cancer. The MAS protein is known to bind to and be activated by Ang-(1-7); however, the mechanisms of this activation are just starting to be understood. Although there are strong biochemical data regarding the regulation and activation of the AT1R (angiotensin II type 1 receptor) and the AT2R (angiotensin II type 2 receptor), with models of how AngII (angiotensin II) binds each receptor, fewer studies have characterized MAS. In the present study, we characterize the MAS promoter and provide a potential feedback mechanism that could compensate for MAS degradation following activation by Ang-(1-7). Analysis of ENCODE data for the MAS promoter revealed potential epigenetic control by KRAB (Krüppel-associated box)/KAP-1 (KRAB-associated protein-1). A proximal promoter construct for the MAS gene was repressed by the SOX [SRY (sex-determining region on the Y chromosome) box] proteins SRY, SOX2, SOX3 and SOX14, of which SRY is known to interact with the KRAB domain. The KRAB-KAP-1 complex can be tyrosine-nitrated, causing the dissociation of the KAP-1 protein and thus a potential loss of epigenetic control. Activation of MAS can lead to an increase in nitric oxide, suggesting a feedback mechanism for MAS on its own promoter. The results of the present study provide a more complete view of MAS regulation and, for the first time, suggest biochemical outcomes for nitration of the KRAB domain.

The tumor suppressor TERE1 (UBIAD1) prenyltransferase regulates the elevated cholesterol phenotype in castration resistant prostate cancer by controlling a program of ligand dependent SXR target genes.

Castrate-Resistant Prostate Cancer (CRPC) is characterized by persistent androgen receptor-driven tumor growth in the apparent absence of systemic androgens. Current evidence suggests that CRPC cells can produce their own androgens from endogenous sterol precursors that act in an intracrine manner to stimulate tumor growth. The mechanisms by which CRPC cells become steroidogenic during tumor progression are not well defined. Herein we describe a novel link between the elevated cholesterol phenotype of CRPC and the TERE1 tumor suppressor protein, a prenyltransferase that synthesizes vitamin K-2, which is a potent endogenous ligand for the SXR nuclear hormone receptor. We show that 50% of primary and metastatic prostate cancer specimens exhibit a loss of TERE1 expression and we establish a correlation between TERE1 expression and cholesterol in the LnCaP-C81 steroidogenic cell model of the CRPC. LnCaP-C81 cells also lack TERE1 protein, and show elevated cholesterol synthetic rates, higher steady state levels of cholesterol, and increased expression of enzymes in the de novo cholesterol biosynthetic pathways than the non-steroidogenic prostate cancer cells. C81 cells also show decreased expression of the SXR nuclear hormone receptor and a panel of directly regulated SXR target genes that govern cholesterol efflux and steroid catabolism. Thus, a combination of increased synthesis, along with decreased efflux and catabolism likely underlies the CRPC phenotype: SXR might coordinately regulate this phenotype. Moreover, TERE1 controls synthesis of vitamin K-2, which is a potent endogenous ligand for SXR activation, strongly suggesting a link between TERE1 levels, K-2 synthesis and SXR target gene regulation. We demonstrate that following ectopic TERE1 expression or induction of endogenous TERE1, the elevated cholesterol levels in C81 cells are reduced. Moreover, reconstitution of TERE1 expression in C81 cells reactivates SXR and switches on a suite of SXR target genes that coordinately promote both cholesterol efflux and androgen catabolism. Thus, loss of TERE1 during tumor progression reduces K-2 levels resulting in reduced transcription of SXR target genes. We propose that TERE1 controls the CPRC phenotype by regulating the endogenous levels of Vitamin K-2 and hence the transcriptional control of a suite of steroidogenic genes via the SXR receptor. These data implicate the TERE1 protein as a previously unrecognized link affecting cholesterol and androgen accumulation that could govern acquisition of the CRPC phenotype.