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The promising expectations about personalized medicine have opened the path to routine large-scale sequencing and increased the importance of genetic counseling for hereditary cancers, among which hereditary breast and ovary cancers (HBOC) have a major impact. High-throughput sequencing, or Next-Generation Sequencing (NGS), has improved cancer patient management, ameliorating diagnosis and treatment decisions. In addition to its undeniable clinical utility, NGS is also unveiling a large number of variants that we are still not able to clearly define and classify, the variants of uncertain significance (VUS), which account for about 40% of total variants. At present, VUS use in the clinical context is challenging. Medical reports may omit this kind of data and, even when included, they limit the clinical utility of genetic information. This has prompted the scientific community to seek easily applicable tests to accurately classify VUS and increase the amount of usable information from NGS data. In this review, we will focus on NGS and classification systems for VUS investigation, with particular attention on HBOC-related genes and in vitro functional tests developed for ameliorating and accelerating variant classification in cancer. [ABSTRACT FROM AUTHOR]

Background: Mutations in the TP53 (Tumour Protein 53) gene can lead to expression of mutant p53 proteins that accumulate in cancer cells and can induce circulating p53 antibodies in cancer patients. Our aim was to evaluate the presence and prognostic role of these antibodies in lung cancer patients and to investigate whether they were related to p53 expression or TP53 mutations in tumour tissues. Methods: A total of 201 lung cancer patients were evaluated for p53 antibodies by ELISA (Enzyme-Linked Immunosorbent Assay) and control was obtained from 54 patients with non-malignant disorders; p53 expression was evaluated in 131 of the lung cancer patients by immunohistochemistry and TP53 mutations were then investigated in 53 tumours positively staining for p53 and in 12 tumours without p53 overexpression, whose DNA was available for direct sequencing. Results: Our results show that 20.4% of cancer patients have positive levels of p53 antibodies, while none of the controls resulted positive. High levels of p53 expression are detected in 57.3% of cases and a significant correlation between serum p53 antibodies and high levels of p53 expression in the corresponding tumours is observed. In non-small cell lung cancer, p53 antibodies are significantly associated with poorly differentiated tumours; furthermore, high levels of p53 expression significantly correlated with squamous cell carcinoma and tumours with highest grade. Survival time of non-small cell lung cancer patients low/negative for serum p53 antibodies was significantly longer compared to patients with positive levels (p = 0.049); in particular, patients with squamous cell carcinoma, but not adenocarcinoma, low/negative for these antibodies show a significant better survival compared to serum-positive patients (p = 0.044). Conclusions: In our study, detection of serum p53 antibodies in non-small cell lung cancer patients has been shown to be useful in identifying subsets of patients with poor prognosis. A significant correlation between the presence of serum p53 antibodies in lung cancer patients and p53 overexpression in the corresponding tumours was also observed. We did not find a significant correlation between levels of serum p53 antibodies and TP53 mutations in the corresponding tumours. [ABSTRACT FROM AUTHOR]

Background: Ataxia-telangiectasia (A-T) is a progressive multisystemic neurodegenerative disease. The phenotypic spectrum includes conditions (variant A-T) with mild, late-onset, and atypical clinical presentations characterized by the prevalence of dyskinetic rather than ataxic features. Cases: We describe the clinical presentations of 3 siblings with early-onset truncal ataxia without obvious neurological deterioration or biological markers of classic A-T phenotype. We performed functional and genetic evaluation of 3 siblings with very mild neurological phenotype. Genetic evaluation with a next-generation sequencing panel for genes causative of cerebellar ataxia detected 2 known ATM gene variants, missense c.9023G>A p.(Arg3008His), and leaky splicing c.1066-6T>G variants. Functional studies showed mildly reduced ATM expression and residual kinase activity in the probands compared with healthy controls. Conclusions: These results suggest the importance of investigating ATM variants even in the presence of clinical and biological atypical cases to ensure specific therapeutic regimens and oncological surveillance in these patients. [ABSTRACT FROM AUTHOR]

The p53 tumor suppressor gene is activated in response to DNA damage resulting in either growth arrest or apoptosis. We previously demonstrated the specific involvement of homeodomain interacting protein-kinase 2 (HIPK2), a nuclear serine/threonine kinase, in inducing p53-dependent apoptosis through selective p53 phosphorylation at serine 46 after severe genotoxic damage. Here we show that HIPK2 contributes to p53 regulation, independently from serine 46 phosphorylation upon nonapoptotic DNA damage such as that induced by cytostatic doses of cisplatin. We show that HIPK2 depletion by RNA interference inhibits p53 binding to the p21Waf1 promoter affecting its p53-induced transactivation thereby allowing cell proliferation. We found that nonapoptotic DNA damage induces p53 acetylation mediated by the HAT protein PCAF and this p53 post-translational modification is abolished by HIPK2 depletion. In this regard, we found that HIPK2 cooperates with PCAF to induce selectively p53 transcriptional activity toward the p21Waf1 promoter while depletion of either HIPK2 or PCAF abolished this function. These data show that HIPK2 regulates the p53 growth arrest function through its PCAF-mediated acetylation.Oncogene (2005) 24, 5431–5442. doi:10.1038/sj.onc.1208717; published online 9 May 2005 [ABSTRACT FROM AUTHOR]

Discusses the interference with the endogenous wt-p53 protein of nontransformed cells of two different murine histotypes. Effect on cell cycle withdrawal; Transcription activeness of wt-p53 during myogenesis; P53 as a regulator of cell differentiation.

Background: SMC1A is a subunit of the cohesin complex that participates in many DNA- and chromosome-related biological processes. Previous studies have established that SMC1A is involved in cancer development and in particular, is overexpressed in chromosomally unstable human colorectal cancer (CRC). This study aimed to investigate whether SMC1A could serve as a therapeutic target for CRC. Methods: At first, we studied the effects of either SMC1A overexpression or knockdown in vitro. Next, the outcome of SMC1A knocking down (alone or in combination with bevacizumab, a monoclonal antibody against vascular endothelial growth factor) was analyzed in vivo. Results: We found that SMC1A knockdown affects cell proliferation and reduces the ability to grow in anchorage-independent manner. Next, we demonstrated that the silencing of SMC1A and the combo treatment were effective in increasing overall survival in a xenograft mouse model. Functional analyses indicated that both treatments lead to atypical mitotic figures and gene expression dysregulation. Differentially expressed genes were implicated in several pathways including gene transcription regulation, cellular proliferation, and other transformation-associated processes. Conclusions: These results indicate that SMC1A silencing, in combination with bevacizumab, can represent a promising therapeutic strategy for human CRC. [ABSTRACT FROM AUTHOR]

Background: SMC1A is a subunit of the cohesin complex that participates in many DNA- and chromosome-related biological processes. Previous studies have established that SMC1A is involved in cancer development and in particular, is overexpressed in chromosomally unstable human colorectal cancer (CRC). This study aimed to investigate whether SMC1A could serve as a therapeutic target for CRC. Methods: At first, we studied the effects of either SMC1A overexpression or knockdown in vitro. Next, the outcome of SMC1A knocking down (alone or in combination with bevacizumab, a monoclonal antibody against vascular endothelial growth factor) was analyzed in vivo. Results: We found that SMC1A knockdown affects cell proliferation and reduces the ability to grow in anchorage-independent manner. Next, we demonstrated that the silencing of SMC1A and the combo treatment were effective in increasing overall survival in a xenograft mouse model. Functional analyses indicated that both treatments lead to atypical mitotic figures and gene expression dysregulation. Differentially expressed genes were implicated in several pathways including gene transcription regulation, cellular proliferation, and other transformation-associated processes. Conclusions: These results indicate that SMC1A silencing, in combination with bevacizumab, can represent a promising therapeutic strategy for human CRC. [ABSTRACT FROM AUTHOR]

Background and purpose: Microtubule defects are a common feature in several neurodegenerative disorders, including hereditary spastic paraplegia. The most frequent form of hereditary spastic paraplegia is caused by mutations in the SPG4/SPAST gene, encoding the microtubule severing enzyme spastin. To date, there is no effective therapy available but spastin‐enhancing therapeutic approaches are emerging; thus prognostic and predictive biomarkers are urgently required. Methods: An automated, simple, fast and non‐invasive cell imaging‐based method was developed to quantify microtubule cytoskeleton organization changes in lymphoblastoid cells and peripheral blood mononuclear cells. Results: It was observed that lymphoblastoid cells and peripheral blood mononuclear cells from individuals affected by SPG4‐hereditary spastic paraplegia show a polarized microtubule cytoskeleton organization. In a pilot study on freshly isolated peripheral blood mononuclear cells, our method discriminates SPG4‐hereditary spastic paraplegia from healthy donors and other hereditary spastic paraplegia subtypes. In addition, it is shown that our method can detect the effects of spastin protein level changes. Conclusions: These findings open the possibility of a rapid, non‐invasive, inexpensive test useful to recognize SPG4‐hereditary spastic paraplegia subtype and evaluate the effects of spastin‐enhancing drug in non‐neuronal cells. [ABSTRACT FROM AUTHOR]

Simple Summary: The increase of exposure to ionizing radiation (IR) from medical procedures has prompted research into improving methodologies for the detection of DNA double-strand breaks (DSBs). The measurement of γH2AX by immunofluorescence has become the gold standard for this analysis. However, for the correct use of γH2AX as a biomarker for the assessment of IR-induced DNA DSBs, several exogenous and endogenous conditions that can influence γH2AX levels must be taken into consideration. Here, we describe the conditions leading to H2AX phosphorylation, the most widely used methods for its detection, the principal applications, and the related problems of γH2AX scoring, with particular regard to clinical studies. People exposed to ionizing radiation (IR) both for diagnostic and therapeutic purposes is constantly increasing. Since the use of IR involves a risk of harmful effects, such as the DNA DSB induction, an accurate determination of this induced DNA damage and a correct evaluation of the risk–benefit ratio in the clinical field are of key relevance. γH2AX (the phosphorylated form of the histone variant H2AX) is a very early marker of DSBs that can be induced both in physiological conditions, such as in the absence of specific external agents, and by external factors such as smoking, heat, background environmental radiation, and drugs. All these internal and external conditions result in a basal level of γH2AX which must be considered for the correct assessment of the DSBs after IR exposure. In this review we analyze the most common conditions that induce H2AX phosphorylation, including specific exogenous stimuli, cellular states, basic environmental factors, and lifestyles. Moreover, we discuss the most widely used methods for γH2AX determination and describe the principal applications of γH2AX scoring, paying particular attention to clinical studies. This knowledge will help us optimize the use of available methods in order to discern the specific γH2AX following IR-induced DSBs from the basal level of γH2AX in the cells. [ABSTRACT FROM AUTHOR]

Background: Lamins, key nuclear lamina components, have been proposed as candidate risk biomarkers in different types of cancer but their accuracy is still debated. AKTIP is a telomeric protein with the property of being enriched at the nuclear lamina. AKTIP has similarity with the tumor susceptibility gene TSG101. AKTIP deficiency generates genome instability and, in p53−/− mice, the reduction of the mouse counterpart of AKTIP induces the exacerbation of lymphomas. Here, we asked whether the distribution of AKTIP is altered in cancer cells and whether this is associated with alterations of lamins. Methods: We performed super-resolution imaging, quantification of lamin expression and nuclear morphology on HeLa, MCF7, and A549 tumor cells, and on non-transformed fibroblasts from healthy donor and HGPS (LMNA c.1824C > T p.Gly608Gly) and EDMD2 (LMNA c.775 T > G) patients. As proof of principle model combining a defined lamin alteration with a tumor cell setting, we produced HeLa cells exogenously expressing the HGPS lamin mutant progerin that alters nuclear morphology. Results: In HeLa cells, AKTIP locates at less than 0.5 µm from the nuclear rim and co-localizes with lamin A/C. As compared to HeLa, there is a reduced co-localization of AKTIP with lamin A/C in both MCF7 and A549. Additionally, MCF7 display lower amounts of AKTIP at the rim. The analyses in non-transformed fibroblasts show that AKTIP mislocalizes in HGPS cells but not in EDMD2. The integrated analysis of lamin expression, nuclear morphology, and AKTIP topology shows that positioning of AKTIP is influenced not only by lamin expression, but also by nuclear morphology. This conclusion is validated by progerin-expressing HeLa cells in which nuclei are morphologically altered and AKTIP is mislocalized. Conclusions: Our data show that the combined alteration of lamin and nuclear morphology influences the localization of the tumor-associated factor AKTIP. The results also point to the fact that lamin alterations per se are not predictive of AKTIP mislocalization, in both non-transformed and tumor cells. In more general terms, this study supports the thesis that a combined analytical approach should be preferred to predict lamin-associated changes in tumor cells. This paves the way of next translational evaluation to validate the use of this combined analytical approach as risk biomarker. [ABSTRACT FROM AUTHOR]

Background: Despite the promise of dual BRAF/MEK inhibition as a therapy for BRAF-mutant (BRAF-mut) melanoma, heterogeneous responses have been observed in patients, thus predictors of benefit from therapy are needed. We have previously identified semaphorin 6A (SEMA6A) as a BRAF-mut-associated protein involved in actin cytoskeleton remodeling. The purpose of the present study is to dissect the role of SEMA6A in the biology of BRAF-mut melanoma, and to explore its predictive potential towards dual BRAF/MEK inhibition. Methods: SEMA6A expression was assessed by immunohistochemistry in melanoma cohort RECI1 (N = 112) and its prognostic potential was investigated in BRAF-mut melanoma patients from DFCI and TCGA datasets (N = 258). The molecular mechanisms regulated by SEMA6A to sustain tumor aggressiveness and targeted therapy resistance were investigated in vitro by using BRAF-mut and BRAF-wt melanoma cell lines, an inducible SEMA6A silencing cell model and a microenvironment-mimicking fibroblasts-coculturing model. Finally, SEMA6A prediction of benefit from dual BRAF/MEK inhibition was investigated in melanoma cohort RECI2 (N = 14). Results: Our results indicate higher protein expression of SEMA6A in BRAF-mut compared with BRAF-wt melanoma patients and show that SEMA6A is a prognostic indicator in BRAF-mut melanoma from TCGA and DFCI patients cohorts. In BRAF-mut melanoma cells, SEMA6A coordinates actin cytoskeleton remodeling by the RhoA-dependent activation of YAP and dual BRAF/MEK inhibition by dabrafenib+trametinib induces SEMA6A/RhoA/YAP axis. In microenvironment-mimicking co-culture condition, fibroblasts confer to melanoma cells a proliferative stimulus and protect them from targeted therapies, whereas SEMA6A depletion rescues the efficacy of dual BRAF/MEK inhibition. Finally, in BRAF-mut melanoma patients treated with dabrafenib+trametinib, high SEMA6A predicts shorter recurrence-free interval. Conclusions: Overall, our results indicate that SEMA6A contributes to microenvironment-coordinated evasion of melanoma cells from dual BRAF/MEK inhibition and it might be a good candidate predictor of short-term benefit from dual BRAF/MEK inhibition. [ABSTRACT FROM AUTHOR]

The Aurora-A kinase (AurkA) and its major regulator TPX2 (Targeting Protein for Xklp2) are key mitotic players frequently co-overexpressed in human cancers, and the link between deregulation of the AurkA/TPX2 complex and tumourigenesis is actively investigated. Chromosomal instability, one of the hallmarks of cancer related to the development of intra-tumour heterogeneity, metastasis and chemo-resistance, has been frequently associated with TPX2-overexpressing tumours. In this study we aimed to investigate the actual contribution to chromosomal instability of deregulating the AurkA/TPX2 complex, by overexpressing it in nontransformed hTERT RPE-1 cells. Our results show that overexpression of both AurkA and TPX2 results in increased AurkA activation and severe mitotic defects, compared to AurkA overexpression alone. We also show that AurkA/TPX2 co-overexpression yields increased aneuploidy in daughter cells and the generation of micronucleated cells. Interestingly, the p53/p21 axis response is impaired in AurkA/TPX2 overexpressing cells subjected to different stimuli; consistently, cells acquire increased ability to proliferate after independent induction of mitotic errors, i.e. following nocodazole treatment. Based on our observation that increased levels of the AurkA/TPX2 complex affect chromosome segregation fidelity and interfere with the activation of a pivotal surveillance mechanism in response to altered cell division, we propose that co-overexpression of AurkA and TPX2 per se represents a condition promoting the generation of a genetically unstable context in nontransformed human cells. [Display omitted] [ABSTRACT FROM AUTHOR]

Background: TP53 gene mutations can lead to the expression of a dysfunctional protein that in turn may enable genetically unstable cells to survive and change into malignant cells. Mutant p53 accumulates early in cells and can precociously induce circulating anti-p53 antibodies (p53Abs); in fact, p53 overexpression has been observed in pre-neoplastic lesions, such as bronchial dysplasia, and p53Abs have been found in patients with Chronic Obstructive Pulmonary Disease, before the diagnosis of lung and other tobacco-related tumors. Methods: A large prospective study was carried out, enrolling non-smokers, ex-smokers and smokers with or without the impairment of lung function, to analyze the incidence of serum p53Abs and the correlation with clinicopathologic features, in particular smoking habits and impairment of lung function, in order to investigate their possible role as early markers of the onset of lung cancer or other cancers. The p53Ab levels were evaluated by a specific ELISA in 675 subjects. Results: Data showed that significant levels of serum p53Abs were present in 35 subjects (5.2%); no difference was observed in the presence of p53Abs with regard to age and gender, while p53Abs correlated with the number of cigarettes smoked per day and packs-year. Furthermore, serum p53Abs were associated with the worst lung function impairment. The median p53Ab level in positive subjects was 3.5 units/ml (range 1.2 to 65.3 units/ml). Only fifteen positive subjects participated in the follow-up, again resulting positive for serum p53Abs, and no evidence of cancer was found in these patients. Conclusion: The presence of serum p53Abs was found to be associated with smoking level and lung function impairment, both risk factors of cancer development. However, in our study we have not observed the occurrence of lung cancer or other cancers in the follow-up of positive subjects, therefore we cannot directly correlate the presence of serum p53Abs with cancer risk. [ABSTRACT FROM AUTHOR]

Abstract: Homeodomain-interacting protein kinase 2 (HIPK2) is a multitalented protein that exploits its kinase activity to modulate key molecular pathways in cancer to restrain tumor growth and induce response to therapies. HIPK2 phosphorylates oncosuppressor p53 for apoptotic activation. In addition, also p53-independent apoptotic pathways are regulated by HIPK2 and can be exploited for anticancer purpose too. Therefore, HIPK2 activity is considered a central switch in targeting tumor cells toward apoptosis upon genotoxic damage and the preservation and/or restoration of HIPK2 function is crucial for an efficient tumor response to therapies. As a proof of principle, HIPK2 knockdown impairs p53 function, induces chemoresistance, angiogenesis, and tumor growth in vivo, on the contrary, HIPK2 overexpression activates apoptotic pathways, counteracts hypoxia, inhibits angiogenesis, and induces chemosensitivity both in p53-dependent and -independent ways. The role of HIPK2 in restraining tumor development was also confirmed by studies with HIPK2 knockout mice. Recent findings demonstrated that HIPK2 inhibitions do exist in tumors and depend by several mechanisms including HIPK2 cytoplasmic localization, protein degradation, and loss of heterozygosity (LOH), recapitulating the biological outcome obtained by RNA interference studies in tumor cells, such as p53 inactivation, resistance to therapies, apoptosis inhibition, and tumor progression. These findings may lead to new diagnostic and therapeutic approaches for treating cancer patients.This review will focus on the last updates about HIPK2 contribution in tumorigenesis and cancer treatment [ABSTRACT FROM AUTHOR]

32D cells expressing v-Ha-Ras fail to show a transformed phenotype. Since Ras requires an active IGF-1R for transformation of fibroblasts, we asked whether expression of IRS-1 or Shc (two of the major substrates of the IGF-1R) could co-operate with oncogenic Ras in transforming 32D cells. We find that IRS-1, but not Shc, in combination with v-Ha-Ras generates a fully transformed phenotype in 32D cells. 32D cells expressing both IRS-1 and v-Ha-Ras (32D/IRS1/Ras) survive and proliferate in the absence of IL-3, do not undergo granulocytic differentiation in the presence of G-CSF and form tumors in nu/nu and syngeneic mice. In contrast, 32D cells expressing singly IRS-1 or v-Ha-Ras exhibit only a block in differentiation capacity. Over-expression of Shc proteins, by itself, promotes differentiation of 32D cells. Concomitant expression of IRS-1 and v-Ha-Ras synergistically phosphorylates ERK-1 and ERK-2 whereas a MEK inhibitor rapidly induces death of 32D/IRS1/Ras transformed cells. Furthermore, transformed 32D/IRS1/Ras cells display high levels of PI3-K activation and undergo rapid apoptosis when exposed to PI3-K inhibitors. The data indicate that: (1) a fully transformed phenotype in 32D cells is generated when a block in differentiation (v-Ha-Ras) is coupled with another differentiation block (IRS-1); (2) PI3-K and MAPK activity are required for the survival of transformed cells; (3) the signals generated by IRS-1 and oncogenic Ras converge on ERK and PI3-K resulting in high levels of activation. Oncogene (2000) 19, 3245–3255 [ABSTRACT FROM AUTHOR]

Alterations of the tumor suppressor gene p53 are uncommon in differentiated thyroid neoplasia but are detected at high frequency in anaplastic thyroid carcinoma suggesting that impaired p53 function may contribute to the undifferentiated and highly aggressive phenotype of these tumors. Effects of wild type p53 (wt-p53) re-expression were investigated in a human anaplastic thyroid carcinoma cell line (ARO) expressing a mutated p53. ARO cells were stably transfected with the temperature-sensitive p53 Val135 gene (ts-p53) which exhibits wild type-like activity at 32°C. Exogenous wt-p53 function in ARO-tsp53 clones was assessed by evaluating its transcriptional activity on a CAT reporter vector containing p53 binding sites. At 32°C, a significant reduction in the proliferation rate (approx. percnt;50%) was observed, with accumulation of cells in the G0/G1 phase of the cell cycle. This effect was accompanied by induction of the expression of the growth inhibitor p21/Waf1 gene. At 32°C, ARO-tsp53 clones also showed a marked impairment of their tumorigenic potential. Furthermore, transfected clones re-acquired the ability to respond to thyrotropin (TSH) stimulation showing an increased expression of thyroid-specific genes (thyroglobulin, thyroperoxidase and TSH receptor). In conclusion, re-expression of wt-p53 activity in ARO cells, inhibits cell proliferation and restores responsiveness to physiological stimuli. [ABSTRACT FROM AUTHOR]

Patients affected by AIDS-related complex (ARC) show several immunological abnormalities which may lead to a disregulation of immunosurveillance against viral latent infections. In this paper evidence for Epstein-Barr virus (EBV) reactivation in seven out of eight affected by persistent generalized lymphadenopathy is given. These patients showed either elevated levels of circulating EBNA-positive transformed cells or depressed EBV-specific T cell cytotoxicity, as assessed by the regression assay, or both. A direct involvement of EBV in the pathogenesis of ARC is thus suggested. Natural killer cell activity was found decreased, correlating to the evidence of circulating EBV-infected cells and of impaired EBV-specific immune control. These data provide evidence that, when specific immune mechanisms lose control on ubiquitous latent viruses, the risk for reactivation becomes higher. In the case of EBV, direct evidence of this event is provided by the emergence in the peripheral blood of clones of infected cells with unlimited growth potential. [ABSTRACT FROM AUTHOR]

Cytokinesis is monitored by a molecular machinery that promotes the degradation of the intercellular bridge, a transient protein structure connecting the two daughter cells. Here, we found that CSA and CSB, primarily defined as DNA repair factors, are located at the midbody, a transient structure in the middle of the intercellular bridge, where they recruit CUL4 and MDM2 ubiquitin ligases and the proteasome. As a part of this molecular machinery, CSA and CSB contribute to the ubiquitination and the degradation of proteins such as PRC1, the Protein Regulator of Cytokinesis, to ensure the correct separation of the two daughter cells. Defects in CSA or CSB result in perturbation of the abscission leading to the formation of long intercellular bridges and multinucleated cells, which might explain part of the Cockayne syndrome phenotypes. Our results enlighten the role played by CSA and CSB as part of a ubiquitin/proteasome degradation process involved in transcription, DNA repair, and cell division. [ABSTRACT FROM AUTHOR]

Discusses a study which examined the relationship between arachidonate 5-lipoxygenase (5-LO) expression/function and molecular events regulated by the tumor suppressor gene P53 in response to genotoxic stress. Effect of genotoxic agents on 5-LO expression and activity; Assessment of the functional role of 5-LO in cancer cell response to genotoxic damage; Methods used in investigating the mechanisms of 5-LO actions on p53 functions.

The faithful inheritance of chromosomes is essential for the propagation of organisms. In eukaryotes, central to this process is the mitotic spindle. Recently, we have identified TRIM8 as a gene aberrantly expressed in gliomas whose expression reduces the clonogenic potential in the patients' glioma cells. TRIM8 encodes an E3 ubiquitin ligase involved in various pathological processes, including hypertrophy, antiviral defense, encephalopathy, and cancer development. To gain insights into the TRIM8 functions, we characterized the TRIM8 interactome in primary mouse embryonic neural stem cells using proteomics. We found that TRIM8 interacts with KIFC1, and KIF11/Eg5, two master regulators of mitotic spindle assembly and cytoskeleton reorganization. By exploring the TRIM8 role in the mitotic spindle machinery, we showed that TRIM8 localizes at the mitotic spindle during mitosis and plays a role in centrosome separation at the beginning of mitosis with a subsequent delay of the mitotic progression and impact on chromosomal stability. [ABSTRACT FROM AUTHOR]

Summary: Human AKTIP and mouse Ft1 are orthologous ubiquitin E2 variant proteins involved in telomere maintenance and DNA replication. AKTIP also interacts with A‐ and B‐type lamins. These features suggest that Ft1 may be implicated in aging regulatory pathways. Here, we show that cells derived from hypomorph Ft1 mutant (Ft1kof/kof) mice exhibit telomeric defects and that Ft1kof/kof animals develop progeroid traits, including impaired growth, skeletal and skin defects, abnormal heart tissue, and sterility. We also demonstrate a genetic interaction between Ft1 and p53. The analysis of mice carrying mutations in both Ft1 and p53 (Ft1kof/kof; p53ko/ko and Ft1kof/kof; p53+/ko) showed that reduction in p53 rescues the progeroid traits of Ft1 mutants, suggesting that they are at least in part caused by a p53‐dependent DNA damage response. Conversely, Ft1 reduction alters lymphomagenesis in p53 mutant mice. These results identify Ft1 as a new player in the aging process and open the way to the analysis of its interactions with other progeria genes using the mouse model. [ABSTRACT FROM AUTHOR]

Background: Granzyme B (GrB) is a serine protease, traditionally known as expressed by cytotoxic lymphocytes to induce target cell apoptosis. However, it is emerging that GrB, being also produced by a variety of normal and neoplastic cells and potentially acting on multiple targets, might represent a powerful regulator of a wide range of fundamental biological processes. We have previously shown that GrB is expressed in urothelial carcinoma tissues and its expression is associated to both pathological tumor spreading and EMT. We have also shown that docosahexaenoic acid (DHA), a dietary ?-3 polyunsaturated fatty acid with anti-tumor activity, while inhibiting urothelial and pancreatic carcinoma cell invasion also inhibited their GrB expression in vitro. In this study, we characterized a panel of colorectal carcinoma (CRC) cells, with different invasive capabilities, for GrB expression and for the contribution of GrB to their EMT and invasive phenotype. In addition, we investigated the effect of DHA on CRC cell-associated GrB expression, EMT and invasion. Methods: The expression levels of GrB and EMT-related markers were evaluated by Western blotting. GrB knockdown was performed by Stealth RNAi small interfering RNA silencing and ectopic GrB expression by transfection of human GrB vector. Cell invasion was determined by the BioCoat Matrigel invasion chamber test. Results: GrB was produced in 57.1 % CRC cell lines and 100 % CRC-derived Cancer Stem Cells. Although GrB was constitutive expressed in both invasive and noninvasive CRC cells, GrB depletion in invasive CRC cells downmodulated their invasion in vitro, suggesting a contribution of GrB to CRC invasiveness. GrB loss or gain of function downmodulated or upmodulated EMT, respectively, according to the analysis of cancer cell expression of three EMT biomarkers (Snail1, E-cadherin, N-cadherin). Moreover, TGF-β1-driven EMT was associated to the enhancement of GrB expression in CRC cell lines, and GrB depletion led to downmodulation of TGF-β1-driven EMT. In addition, DHA inhibited GrB expression, EMT and invasion in CRC cells in vitro. Conclusions: These findings present a novel role for GrB as upmodulator of EMT in CRC cells. Moreover, these results support the use of DHA, a dietary compound without toxic effects, as adjuvant in CRC therapy. [ABSTRACT FROM AUTHOR]

Purpose: This study investigates whether the abscopal effect induced by radiation-therapy (RT) is able to sterilize non-irradiated tumour cells through bystander signals. Material and methods: Wild-type (wt)-p53 or p53-null HCT116 human colon cancer cells were xenografted into both flanks of athymic female nude mice. When tumours reached a volume of 0.2 cm3, irradiation was performed, under strict dose monitoring, with a dedicated mobile accelerator designed for intra-Operative-RT (IORT). A dose of 10 or 20 Gy (IR groups), delivered by a 10 MeV electron beam, was delivered to a tumour established in one side flank, leaving the other non-irradiated (NIR groups). A subset of mice were sacrificed early on to carry out short-term molecular analyses. Results: All directly-irradiated tumours, showed a dose-dependent delayed and reduced regrowth, independent of the p53 status. Importantly, a significant effect on tumour-growth inhibition was also demonstrated in NIR wt-p53 tumours in the 20 Gy-irradiation group, with a moderate effect also evident after 10 Gy-irradiation. In contrast, no significant difference was observed in the NIR p53-null tumours, independent of the dose delivered. Molecular analyses indicate that p53-dependent signals might be responsible for the abscopal effect in our model system, via a pro-apoptotic pathway. Conclusions: We suggest that the interplay between delivered dose and p53 status might help to sterilize out-of-field tumour cells. [ABSTRACT FROM AUTHOR]

Background Mutations in the DNA damage response (DDR) factors, breast cancer 1 (BRCA1) and BRCA2, sensitize tumor cells to poly(ADP-ribose) polymerase (PARP) inhibitors. The ataxia telangiectasia mutated (ATM) kinase is a key DDR protein whose heterozygous germline mutation is a moderate-risk factor for developing breast cancer. In this study, we examined whether ATM inactivation in breast cancer cell lines confers sensitivity to PARP inhibitors. Methods Wild-type BRCA1/2 breast cancer cells (i.e., MCF-7 and ZR-75-1 lines) were genetically manipulated to downregulate ATM expression then assayed for cytostaticity/cytotoxicity upon treatment with PARP inhibitors, olaparib and iniparib. Results When ATM-depleted cells and their relative controls were treated with olaparib (a competitive PARP-1/2 inhibitor) and iniparib (a molecule originally described as a covalent PARP-1 inhibitor) a different response to the two compounds was observed. ATM-depletion sensitized both MCF-7 and ZR-75-1 cells to olaparib-treatment, as assessed by short and long survival assays and cell cycle profiles. In contrast, iniparib induced only a mild, ATMdependent cytostatic effect in MCF-7 cells whereas ZR-75-1 cells were sensitive to this drug, independently of ATM inactivation. These latest results might be explained by recent observations indicating that iniparib acts with mechanisms other than PARP inhibition. Conclusions These data indicate that ATM-depletion can sensitize breast cancer cells to PARP inhibition, suggesting a potential in the treatment of breast cancers low in ATM protein expression/activity, such as those arising in mutant ATM heterozygous carriers. [ABSTRACT FROM AUTHOR]

Background: TP53 gene mutations can lead to the expression of a dysfunctional protein that in turn may enable genetically unstable cells to survive and change into malignant cells. Mutant p53 accumulates early in cells and can precociously induce circulating anti-p53 antibodies (p53Abs); in fact, p53 overexpression has been observed in pre-neoplastic lesions, such as bronchial dysplasia, and p53Abs have been found in patients with chronic obstructive pulmonary disease, before the diagnosis of lung and other tobacco-related tumors.Methods: A large prospective study was carried out, enrolling non-smokers, ex-smokers and smokers with or without the impairment of lung function, to analyze the incidence of serum p53Abs and the correlation with clinicopathologic features, in particular smoking habits and impairment of lung function, in order to investigate their possible role as early markers of the onset of lung cancer or other cancers. The p53Ab levels were evaluated by a specific ELISA in 675 subjects.Results: Data showed that significant levels of serum p53Abs were present in 35 subjects (5.2%); no difference was observed in the presence of p53Abs with regard to age and gender, while p53Abs correlated with the number of cigarettes smoked per day and packs-year. Furthermore, serum p53Abs were associated with the worst lung function impairment. The median p53Ab level in positive subjects was 3.5 units/ml (range 1.2 to 65.3 units/ml). Only fifteen positive subjects participated in the follow-up, again resulting positive for serum p53Abs, and no evidence of cancer was found in these patients.Conclusion: The presence of serum p53Abs was found to be associated with smoking level and lung function impairment, both risk factors of cancer development. However, in our study we have not observed the occurrence of lung cancer or other cancers in the follow-up of positive subjects, therefore we cannot directly correlate the presence of serum p53Abs with cancer risk. [ABSTRACT FROM AUTHOR]

Abstract: HIPK2 (homeodomain-interacting protein kinase-2) binds to and phosphorylates, at Ser and Thr residues, a large number of targets involved in cell division and cell fate decision in response to different physiological or stress stimuli. Inactivation of HIPK2 has been observed in human and mouse cancers supporting its role as a tumor suppressor. Despite the biological relevance of this kinase, very little is known on how HIPK2 becomes catalytically active. Based on sequence homologies, HIPK2 has been taxonomically classified as a subfamily member of the dual-specificity tyrosine-regulated kinases (DYRKs) and the activation-loop Y354 of HIPK2 has been found phosphorylated in different cells; however, the relevance of this Y phosphorylation is presently unknown. Here, we show that HIPK2, which is extensively phosphorylated at S/T sites throughout its functional domains, becomes catalytically active by autophosphorylation at the activation-loop Y354. In particular, we found that, in analogy to DYRKs, HIPK2-Y354 phosphorylation is an autocatalytic event and its prevention, through Y354 substitution with non-phosphorylatable amino acids or by using the kinase inhibitor purvalanol A, induces a strong reduction of the HIPK2 S/T-kinase activity on different substrates. Interestingly, at variance from DYRKs, inhibition of HIPK2-Y354 phosphorylation induces a strong out-of-target Y-kinase activity in cis and a strong cytoplasmic relocalization of the kinase. Together, these results demonstrate that the catalytic activity, substrate specificity, and subcellular localization of HIPK2 are regulated by autophosphorylation of its activation-loop Y354. [Copyright &y& Elsevier]

Ataxia-telangiectasia (A-T) is an autosomal recessive neurodegenerative disorder characterized by radiosensitivity, genomic instability, and predisposition to cancer. A-T is caused by biallelic mutations in the ataxia-telangiectasia mutated (ATM) gene, but heterozygous carriers, though apparently healthy, are believed to be at increased risk for cancer and more sensitive to ionizing radiation than the general population. Despite progress in functional and sequencing-based assays, no straightforward, rapid, and inexpensive test is available for the identification of A-T homozygotes and heterozygotes, which is essential for diagnosis, genetic counseling, and carrier prediction. The oncosuppressor p53 prevents genomic instability and centrosomal amplification. During mitosis, p53 localizes at the centrosome in an ATM-dependent manner. We capitalized on the latter finding and established a simple, fast, minimally invasive, reliable, and inexpensive test to determine mutant ATM zygosity. The percentage of mitotic lymphoblasts or PBMCs bearing p53 centrosomal localization clearly discriminated among healthy donors (>75%), A-T heterozygotes (40%-56%), and A-T homozygotes (<30%). The test is specific for A-T, independent of the type of ATM mutations, and recognized tumor-associated ATM polymorphisms. In a preliminary study, our test confirmed that ATM is a breast cancer susceptibility gene. These data open the possibility of cost-effective, early diagnosis of A-T homozygotes and large-scale screenings for heterozygotes. [ABSTRACT FROM AUTHOR]

Ataxia-telangiectasia (A-T) is an autosomal recessive neurodegenerative disorder characterized by radiosensi-tivity, genomic instability, and predisposition to cancer. A-T is caused by biallelic mutations in the ataxia-te-langiectasia mutated (ATM) gene, but heterozygous carriers, though apparently healthy, are believed to be at increased risk for cancer and more sensitive to ionizing radiation than the general population. Despite prog-ress in functional and sequencing-based assays, no straightforward, rapid, and inexpensive test is available for the identification of A-T homozygotes and heterozygotes, which is essential for diagnosis, genetic counseling, and carrier prediction. The oncosuppressor p53 prevents genomic instability and centrosomal amplification. During mitosis, p53 localizes at the centrosome in an ATM-dependent manner. We capitalized on the latter finding and established a simple, fast, minimally invasive, reliable, and inexpensive test to determine mutant ATM zygosity. The percentage of mitotic lymphoblasts or PBMCs bearing p53 centrosomal localization clearly discriminated among healthy donors (>75%), A-T heterozygotes (40%-56%), and A-T homozygotes (<30%). The test is specific for A-T, independent of the type of ATM mutations, and recognized tumor-associated ATM polymorphisms. In a preliminary study, our test confirmed that ATM is a breast cancer susceptibility gene. These data open the possibility of cost-effective, early diagnosis of A-T homozygotes and large-scale screenings for heterozygotes. [ABSTRACT FROM AUTHOR]

Summary: Failure in cytokinesis, the final step in cell division, by generating tetra- and polyploidization promotes chromosomal instability, a hallmark of cancer. Here we show that HIPK2, a kinase involved in cell fate decisions in development and response to stress, controls cytokinesis and prevents tetraploidization through its effects on histone H2B. HIPK2 binds and phosphorylates histone H2B at S14 (H2B-S14P), and the two proteins colocalize at the midbody. HIPK2 depletion by targeted gene disruption or RNA interference results in loss of H2B-S14P at the midbody, prevention of cell cleavage, and tetra- and polyploidization. In HIPK2 null cells, restoration of wild-type HIPK2 activity or expression of a phosphomimetic H2B-S14D derivative abolishes cytokinesis defects and rescues cell proliferation, showing that H2B-S14P is required for a faithful cytokinesis. Overall, our data uncover mechanisms of a critical HIPK2 function in cytokinesis and in the prevention of tetraploidization. [Copyright &y& Elsevier]

Inflammation is a key pathological characteristic of dystrophic muscle lesion formation, limiting muscle regeneration and resulting in fibrotic and fatty tissue replacement of muscle, which exacerbates the wasting process in dystrophic muscles. Limiting immune response is thus one of the therapeutic options to improve healing, as well as to improve the efficacy of gene- or cell-mediated strategies to restore dystrophin expression. Protein kinase θ h (PKCθ) is a member of the PKCs family highly expressed in both immune cells and skeletal muscle; given its crucial role in adaptive, but also innate, immunity, it is being proposed as a valuable pharmacological target for immune disorders. In our study we asked whether targeting PKCh could represent a valuable approach to efficiently prevent inflammatory response and disease progression in a mouse model of muscular dystrophy. We generated the bi-genetic mouse model mdx/θ-/-, where PKCθ expression is lacking in mdx mice, the mouse model of Duchenne muscular dystrophy. We found that muscle wasting in mdx/θ-/- mice was greatly prevented, while muscle regeneration, maintenance and performance was significantly improved, as compared to mdx mice. This phenotype was associated to reduction in inflammatory infiltrate, pro-inflammatory gene expression and profibrotic markers activity, as compared to mdx mice. Moreover, BM transplantation experiments demonstrated that the phenotype observed was primarily dependent on lack of PKCθ expression in hematopoietic cells. These results demonstrate a hitherto unrecognized role of immune-cell intrinsic PKCθ activity in the development of DMD. Although the immune cell population(s) involved remain unidentified, our findings reveal that PKCθ can be proposed as a new pharmacological target to counteract the disease, as well as to improve the efficacy of gene- or cell- therapy approaches. [ABSTRACT FROM AUTHOR]

HIPK2 is a serine/threonine kinase that acts as a coregulator of an increasing number of factors involved in cell survival and proliferation during development and in response to different types of stress. Here we report on a novel target of HIPK2, the cyclin-dependent kinase inhibitor p27kip1. HIPK2 phosphorylates p27kip1 in vitro and in vivo at serine 10, an event that accounts for 80% of the total p27kip1 phosphorylation and plays a crucial role in the stability of the protein. Indeed, HIPK2 depletion by transient or stable RNA interference in tumor cells of different origin was consistently associated with strong reduction of p27kip1 phosphorylation at serine 10 and of p27kip1 stability. An initial evaluation of the functional relevance of this HIPK2-mediated regulation of p27kip1 revealed a contribution to cell motility, rather than to cell proliferation, but only in cells that do not express wild-type p53. [ABSTRACT FROM AUTHOR]

Background: Galectin-3 (Gal-3) is an anti-apoptotic molecule involved in thyroid cells transformation. It is specifically overexpressed in thyroid tumour cells and is currently used as a preoperative diagnostic marker of thyroid malignancy. Gal-3 expression is downregulated by wt-p53 at the transcriptional level. In well-differentiated thyroid carcinomas (WDTCs) there is an unexplained paradoxical concomitant expression of Gal-3 and wt-p53. HIPK2 is a co-regulator of different transcription factors, and modulates basic cellular processes mainly through the activation of wt-p53. Since we demonstrated that HIPK2 is involved in p53-mediated Gal-3 downregulation, we asked whether HIPK2 deficiency might be responsible for such paradoxical Gal-3 overexpression in WDTC. Methodology/Principal Findings: We analyzed HIPK2 protein and mRNA levels, as well as loss of heterozygosity (LOH) at the HIPK2 locus (7q32-34), in thyroid tissue samples. HIPK2 protein levels were high in all follicular hyperplasias (FHs) analyzed. Conversely, HIPK2 was undetectable in 91.7% of papillary thyroid carcinomas (PTCs) and in 60.0% of follicular thyroid carcinomas (FTCs). HIPK2 mRNA levels were upregulated in FH compared to normal thyroid tissue (NTT), while PTC showed mean HIPK2 mRNA levels lower than FH and, in 61.5% of cases, also lower than NTT. We found LOH at HIPK-2 gene locus in 37.5% of PTCs, 14.3% of FTCs and 18.2% of follicular adenomas. To causally link these data with Gal-3 upregulation, we performed in vitro experiments, using the PTC-derived K1 cells, in which HIPK2 expression was manipulated by RNA interference (RNAi) or plasmid-mediated overexpression. HIPK2 RNAi was associated with Gal-3 upregulation, while HIPK2 overexpression with Gal-3 downregulation. Conclusions/Significance: Our results indicate that HIPK2 expression and function are impaired in WDTCs, in particular in PTCs, and that this event explains Gal-3 overexpression typically observed in these types of tumours. Therefore, HIPK2 can be considered as a new tumour suppressor gene for thyroid cancers. [ABSTRACT FROM AUTHOR]

Serum and glucocorticoid regulated kinase 1 (Sgk1) is a serine–threonine kinase that is activated by serum, steroids, insulin, vasopressin, and interleukin 2 at the transcriptional and post-translational levels. Sgk1 is also important in transduction of growth factors and steroid-dependent survival signals and may have a role in the development of resistance to cancer chemotherapy. In the present paper, we demonstrate that Sgk1 activates MDM2-dependent p53 ubiquitylation. The results were obtained in RKO cells and other cell lines by Sgk1-specific RNA silencing and were corroborated in an original mouse model as well as in transiently and in stably transfected HeLa cells expressing wild-type or dominant negative Sgk1 mutant. Sgk1 contributes to cell survival, cell-cycle progression, and epithelial de-differentiation. We also show that the effects of Sgk1 on the clonogenic potential of different cancer cells depend on the expression of wild-type p53. Since transcription of Sgk1 is activated by p53, we propose a finely tuned feedback model where Sgk1 down-regulates the expression of p53 by enhancing its mono- and polyubiquitylation. [ABSTRACT FROM AUTHOR]

Background: In the cardiovascular system, laminar shear stress (SS) is one of the most important source of endothelial protecting signals. Physical and chemical agents, however, including ionising radiations and anticancer drugs, may injure endothelial cells determining an increase in oxidative stress and genotoxic damage. Whether the SS protective function remains intact in the presence of strong oxidants or DNA damage is currently unclear. Methods and Results: To investigate this aspect a series of experiments were performed in which HUVEC were exposed to sub-lethal doses of the radio-mimetic compound Bleomycin (Bleo; 10 μg/ml) which generated free radicals (ROS) without significantly compromising cell survival. Remarkably, the application of a SS of 12 dyne/cm2 did not protect endothelial cells but markedly accelerated apoptosis compared to controls kept in static culture and in the presence of Bleo. Experiments with the inducible nitric oxide synthase (iNOS) inhibitor GW274150 significantly reduced the SS-dependent apoptosis indicating that the production of NO was relevant for this effect. At molecular level, the ataxia-telangectasia-mutated (ATM) kinase, the homeodomain-interacting protein kinase-2 (HIPK2) and p53 were found activated along a pro-apoptotic signalling pathway while p21waf1,cip1,sdi1 was prevented from its protective action. RNA interference experiments revealed that HIPK2 and p53 were both important for this process, however, only the forced expression p21waf1,cip1,sdi1 fully restored the SS-dependent pro-survival function. Conclusions: This study provides the first evidence that, in the presence of genotoxic damage, laminar flow contributes to endothelial toxicity and death and identifies molecular targets potentially relevant in endothelial dysfunction and cardiovascular disease pathogenesis. [ABSTRACT FROM AUTHOR]

MDM4 is a key regulator of p53, whose biological activities depend on both transcriptional activity and transcription-independent mitochondrial functions. MDM4 binds to p53 and blocks its transcriptional activity; however, the main cytoplasmic localization of MDM4 might also imply a regulation of p53-mitochondrial function. Here, we show that MDM4 stably localizes at the mitochondria, in which it (i) binds BCL2, (ii) facilitates mitochondrial localization of p53 phosphorylated at Ser46 (p53Ser46P) and (iii) promotes binding between p53Ser46P and BCL2, release of cytochrome C and apoptosis. In agreement with these observations, MDM4 reduction by RNA interference increases resistance to DNA-damage-induced apoptosis in a p53-dependent manner and independently of transcription. Consistent with these findings, a significant downregulation of MDM4 expression associates with cisplatin resistance in human ovarian cancers, and MDM4 modulation affects cisplatin sensitivity of ovarian cancer cells. These data define a new localization and function of MDM4 that, by acting as a docking site for p53Ser46P to BCL2, facilitates the p53-mediated intrinsic-apoptotic pathway. Overall, our results point to MDM4 as a double-faced regulator of p53. [ABSTRACT FROM AUTHOR]

The homeodomain-interacting protein kinase 2 (HIPK2) protein is a member of a recently identified family of nuclear protein kinases that are well conserved in various organisms. HIPK2 can bind to several homeotic factors and to a series of proteins involved in the regulation of cell survival and proliferation in response to morphogenetic and genotoxic signals. Here we report Hipk2-targeted disruption in mouse; Hipk2−/− mice are viable and fertile but significantly smaller than their wild-type littermates. This feature is present at birth and retained throughout the mouse adulthood. Mouse embryo fibroblasts from Hipk2−/− mice show a reduced proliferation rate, compared to the wild-type counterparts, with accumulation in the G0/G1 phase of the cell cycle and altered levels of the cell cycle regulators cyclin D and CDK6. Restoration of wild-type HIPK2 expression in Hipk2−/− cells rescues the normal phenotype supporting a role for HIPK2 in the regulation of cell proliferation. [ABSTRACT FROM AUTHOR]

Abstract: Over the past decade several investigators have reported on the physical interaction of serine/threonine kinases of the homeodomain interacting-protein family (HIPKs) with increasing number of nuclear factors and on their localization in different nuclear sub-compartments. Although we are still far from a global understanding of the molecular consequences of HIPK subnuclear compartmentalization, the spatial description of particular interactions and posttranslational modifications promoted by these kinases on key cellular regulators might provide relevant insights. Here we will discuss the possible implications of the HIPK subnuclear localization in the regulation of gene transcription and in the cell response to stress. [Copyright &y& Elsevier]

Protein phosphorylation is a widely diffuse and versatile post-translational modification that controls many cellular processes, from signal transduction to gene transcription. The homeodomain-interacting protein kinases (HIPKs) belong to a new family of serine–threonine kinases first identified as corepressors for homeodomain transcription factors. Different screenings for the identification of new partners of transcription factors have indicated that HIPK2, the best characterized member of the HIPK family, is a multitalented coregulator of an increasing number of transcription factors and cofactors. The aim of this review is to describe the different mechanisms through which HIPK2 regulates gene transcription. [ABSTRACT FROM AUTHOR]

Summary: In response to DNA damage, p53 induces either cell-cycle arrest or apoptosis by differential transcription of several target genes and through transcription-independent apoptotic functions. p53 phosphorylation at Ser46 by HIPK2 is one determinant of the outcome because it takes place only upon severe, nonrepairable DNA damage that irreversibly drives cells to apoptosis. Here, we show that p53 represses its proapoptotic activator HIPK2 via MDM2-mediated degradation, whereas a degradation-resistant HIPK2 mutant has increased apoptotic activity. Upon cytostatic, nonsevere DNA damage, inhibition of HIPK2 degradation is sufficient to induce p53Ser46 phosphorylation and apoptosis, converting growth-arresting stimuli to apoptotic ones. These findings establish HIPK2 as an MDM2 target and support a model in which, upon nonsevere DNA damage, p53 represses its own phosphorylation at Ser46 due to HIPK2 degradation, supporting the notion that the cell-cycle-arresting functions of p53 include active inhibition of the apoptotic ones. [Copyright &y& Elsevier]

High-mobility group A1 (HMGA1) overexpression and gene rearrangement are frequent events in human cancer, but the molecular basis of HMGA1 oncogenic activity remains unclear. Here we describe a mechanism through which HMGA1 inhibits p53-mediated apoptosis by counteracting the p53 proapoptotic activator homeodomain-interacting protein kinase 2 (HIPK2). We found that HMGA1 overexpression promoted HIPK2 relocalization in the cytoplasm and inhibition of p53 apoptotic function, while HIPK2 overexpression reestablished HIPK2 nuclear localization and sensitivity to apoptosis. HIPK2 depletion by RNA interference suppressed the antiapoptotic effect of HMGA1, which indicates that HIPK2 is the target required for HMGA1 to repress the apoptotic activity of p53. Consistent with this process, a strong correlation among HMGA1 overexpression, HIPK2 cytoplasmic localization, and low spontaneous apoptosis index (comparable to that observed in mutant p53-carrying tumors) was observed in WT p53-expressing human breast carcinomas. Hence, cytoplasmic relocalization of HIPK2 induced by HMGA1 overexpression is a mechanism of inactivation of p53 apoptotic function that we believe to be novel. [ABSTRACT FROM AUTHOR]

Summary: Che-1 is a RNA polymerase II-binding protein involved in the transcription of E2F target genes and induction of cell proliferation. Here we show that Che-1 contributes to DNA damage response and that its depletion sensitizes cells to anticancer agents. The checkpoint kinases ATM/ATR and Chk2 interact with Che-1 and promote its phosphorylation and accumulation in response to DNA damage. These Che-1 modifications induce a specific recruitment of Che-1 on the TP53 and p21 promoters. Interestingly, it has a profound effect on the basal expression of p53, which is preserved following DNA damage. Notably, Che-1 contributes to the maintenance of the G2/M checkpoint induced by DNA damage. These findings identify a mechanism by which checkpoint kinases regulate responses to DNA damage. [Copyright &y& Elsevier]

Abstract: Tp53 is frequently mutated or inactivated in glioblastomas. Due to the impairment of p53 activity, glioblastomas show a high degree of radioresistance. In an attempt to convert the radioresistant phenotype to a more radiosensitive one, we evaluated the efficacy of the combination of Adp53 gene transfer and X-ray irradiation. The combination of Adp53, at low multiplicity in order to mimic the low in vivo efficiency of virus-mediated gene delivery, with X-ray irradiation resulted in a marked decrease of glioblastoms cell survival. Interestingly, Adp53 was able to induce low dose (<2Gy) hypersensitivity. The data suggest the possibility for the development of new therapeutic strategies. [Copyright &y& Elsevier]

The p53 oncosuppressor protein is subject to negative regulation by MDM2, which efficiently inhibits its activity through an autoregulatory loop. In response to stress, however, p53 undergoes post-translational modifications that allow the protein to escape MDM2 control, accumulate, and become active. Recent studies have shown that, following DNA damage, the HIPK2 serine/threonine kinase binds and phosphorylates p53, inducing p53 transcriptional activity and apoptotic function. Here, we investigated the role of HIPK2 in the activation of p53 in the presence of MDM2. We found that HIPK2 rescues p53 transcriptional activity overcoming MDM2 inhibition, and that restoration of this p53 function induces apoptosis. Recovery of p53-dependent apoptosis is achieved by preventing p53 nuclear export and ubiquitination mediated by MDM2 in vitro and in vivo following genotoxic stress. These results shed new light on the mechanisms by which the HIPK2/p53 pathway promotes apoptosis and suppression of tumorigenesis.Oncogene (2004) 23, 5185-5192. doi:10.1038/sj.onc.1207656 Published online 3 May 2004 [ABSTRACT FROM AUTHOR]

HIPK2 is a member of a novel family of nuclear serine–threonine kinases identified through their ability to interact with the Nkx-1.2 homeoprotein. The physiological role of these kinases is largely unknown, but we have recently reported on the involvement of HIPK2 in the induction of apoptosis of tumor cells after UV stress through p53 phosphorylation and transcriptional activation. Here, we demonstrate that the chemotherapeutic drug cisplatin increases HIPK2 protein expression and its kinase activity, and that HIPK2 is involved in cisplatin-dependent apoptosis. Indeed, induction of HIPK2 and of cell death by cisplatin are efficiently inhibited by the serine–threonine kinase inhibitor SB203580 or the transduction of HIPK2-specific RNA-interfering molecules. HIPK2 gene silencing efficiently reduces the p53-mediated transcriptional activation of apoptotic gene promoters as well as apoptotic cell death after treatment with cisplatin. These findings, along with the involvement of p53 phosphorylation at serine 46 (Ser46) in the transcriptional activation of apoptotic gene promoters, suggest a critical role for HIPK2 in triggering p53-dependent apoptosis in response to the antineoplastic drug cisplatin. [Copyright &y& Elsevier]

The p53 oncosuppressor is strictly maintained in an inactive form under normal conditions, while it is post-translationally activated by a variety of stresses, enacting different protective biological functions. Since one critical issue in cancer gene therapy is tumor specificity, we asked whether the tight p53 regulation applies also to exogenously transferred p53. In principle, this type of regulation could allow p53 gene transfer in both normal and tumor cells to produce detrimental effects only in the latter ones. Here, we report that primary bone marrow cells infected with a p53 recombinant retrovirus and transplanted into irradiated mice reconstitute the hematopoietic system, with no detectable alterations in any of its compartments. Furthermore, simultaneous infection of leukemia and bone marrow cells depleted the neoplastic contamination, allowing lifelong, disease-free survival of 65% of the transplanted animals. These results show that exogenous p53 is controlled as tightly as the endogenous one, and opens the way to p53 gene therapy, without requiring tumor targeting.Oncogene (2004) 23, 418-425. doi:10.1038/sj.onc.1207042 [ABSTRACT FROM AUTHOR]

Presents a study showing that the TP53INP1 gene localize with p53, PML-IV and HIPK2 into the PML-NB. Physical interaction of the gene with HIPK2 and p53; Role of TP53INP1, in association with HIPK2, regulate p53 transcriptional activity on p21, mdm2, pig3 and bax promoters; Impact of TP53INP1 overexpression on p53-mediated apoptosis.

DNA tumor virus oncoproteins bind and inactivate Rb by interfering with the Rb/HDAC1 interaction. Che-1 is a recently identified human Rb binding protein that inhibits the Rb growth suppressing function. Here we show that Che-1 contacts the Rb pocket region and competes with HDAC1 for Rb binding site, removing HDAC1 from the Rb/E2F complex in vitro and from the E2F target promoters in vivo. Che-1 overexpression activates DNA synthesis in quiescent NIH-3T3 cells through HDAC1 displacement. Consistently, Che-1-specific RNA interference affects E2F activity and cell proliferation in human fibroblasts but not in the pocket protein-defective 293 cells. These findings indicate the existence of a pathway of Rb regulation supporting Che-1 as the cellular counterpart of DNA tumor virus oncoproteins. [Copyright &y& Elsevier]

Phosphorylation of p53 at Ser 46 was shown to regulate p53 apoptotic activity. Here we demonstrate that homeodomain-interacting protein kinase-2 (HIPK2), a member of a novel family of nuclear serine/threonine kinases, binds to and activates p53 by directly phosphorylating it at Ser 46. HIPK2 localizes with p53 and PML-3 into the nuclear bodies and is activated after irradiation with ultraviolet. Antisense inhibition of HIPK2 expression reduces the ultraviolet-induced apoptosis. Furthermore, HIPK2 and p53 cooperate in the activation of p53-dependent transcription and apoptotic pathways. These data define a new functional interaction between p53 and HIPK2 that results in the targeted subcellular localization of p53 and initiation of apoptosis. [ABSTRACT FROM AUTHOR]

The onco-suppressor gene TP53 has potential use in the gene therapy of many human cancers including leukemias. The latter indication derived from numerous experimental reports of p53-mediated suppressing effects on human and murine leukemia cells in vitro. However, few in vivo experiments have been performed, and those that have used a subcutaneous injection of p53-transduced leukemia cells. Thus, we developed an orthotopic leukemia model in adult, syngenic mice to evaluate the feasibility of TP53-mediated therapeutic approaches. We found that among other cells, v-src-transformed 32D myeloid progenitors induce leukemia when injected intravenously in syngenic mice. The resulting malignancy resembles the clinical manifestations of human acute myeloid leukemia because it is characterized by a massive invasion of bone marrow compartments, splenomegaly, generalized lymphadenopathy, and a macroscopic or microscopic infiltration of the kidneys, liver, and lungs. When these 32Dv-src cells were infected with a TP53-recombinant retrovirus before intravenous injection, we found a decreased mortality and, in those animals that develop leukemia, a drastic reduction of the generalized organ infiltration, suggesting that exogenous TP53 expression might be used for ex vivo bone marrow purging from leukemia cells. [ABSTRACT FROM AUTHOR]