Chromosome 20 aberrations at the diploid-aneuploid transition in sporadic colorectal cancer.

DNA aneuploid sublines in sporadic colorectal cancers (CRCs) are quite frequent (about 85%) and likely the consequence of chromosomal instability and DNA copy number aberrations (CNAs). In order to gain insight into the mechanisms of the diploid-aneuploid transition in CRCs, we compared the CNA status in both diploid and aneuploid sublines. We used fresh/frozen material from 17 aneuploid CRCs, which was separated into 17 DNA diploid and 17 aneuploid sublines using enrichment of the epithelial component by multiparameter flow cytometry and sorting. CNA status of both sublines was obtained by array comparative genomic hybridization. The DNA diploid sublines from the aneuploid CRCs showed already CNAs, in particular, gains at 20 p and 20 q. The same aberrations were detected at increased frequencies in the corresponding DNA aneuploid sublines. Moreover, the very frequent gains/losses of chromosomes 4, 7, 8, 13, 15, and 18 in the DNA aneuploid sublines were absent or rare in the DNA diploid sublines from the same sporadic aneuploid CRCs. The comparison of the DNA diploid and aneuploid sublines from aneuploid CRCs suggests that 20 p and 20 q gains may play a role in the diploid-aneuploid transition. The 20 q chromosomal arm appears of particular interest since it harbors several genes implicated in chromosomal instability.

Field effect in oral precancer as assessed by DNA flow cytometry and array-CGH.

OBJECTIVE: 'Field cancerization' is an accepted model for oral carcinogenesis. So far, genetically altered fields have been just reported in the presence of carcinomas. This study assessed the distant mirror fields (MFs) of oral precancer by DNA high-resolution flow cytometry (hr DNA-FCM) and array-Comparative Genomic Hybridization (a-CGH). METHODS: Five leukoplakias without dysplasia (OLs), seven dysplastic leukoplakias (DOLs), and 12 corresponding visually normal and non-dysplastic MFs were analyzed. DNA aneuploidy (DNA Index, DI ≠ 1) was detected by hr DNA-FCM on DAPI stained nuclei suspensions. The epithelial DNA aneuploid subclones were FCM-sorted to obtain genomic DNA for a-CGH. RESULTS: Mirror fields, OLs, and DOLs showed increasing prevalence of DNA aneuploidy of, respectively, 8%, 20%, and 57%. The average number of chromosome aberrations (Ch-Abs) was 2.8 in MFs, 3 in OLs, and 10.6 in DOLs. MFs relative to OLs and DOLs had average numbers of Ch-Abs, respectively, of 1.8 and 3.6. Ch-Abs were also observed in DNA diploid sublines, and often the same aberrations were observed in both MFs and corresponding OLs/DOLs. CONCLUSION: DNA aneuploidy and Ch-Abs in MFs, the last ones being mainly gains, indicate an early onset of field effect in oral carcinogenesis.

Distinctive chromosomal instability patterns in oral verrucous and squamous cell carcinomas detected by high-resolution DNA flow cytometry.

BACKGROUND: Oral verrucous carcinomas (OVCs) are characterized by better prognosis than oral squamous cell carcinomas (OSCCs). Because chromosomal instability (CIN) in solid tumors is indicative of prognosis, this study investigated whether OVCs and OSCCs were characterized by differences in CIN biomarkers. METHODS: Fresh or frozen multiple tissue samples were submitted to high-resolution DNA flow cytometry (hr DNA-FCM). RESULTS: DNA aneuploid sublines were detected in 6 of 9 OVCs (66.7%) and in 20 of 25 OSCCs (80.0%). Multiple DNA aneuploid sublines were observed, respectively, in 2 of 6 (33.3%) DNA aneuploid OVCs and in 14 of 20 (70%) DNA aneuploid OSCCs (P = .163). OVCs were mainly characterized by DNA Index (DI) values in the near-diploid region (DI≠1 and DI < 1.4), whereas aneuploid OSCCs carried most frequently multiple aneuploid sublines with high DI values (DI ≥ 1.4). DNA near-diploid and high aneuploid sublines were, respectively, 87.5% and 12.5% for the OVCs versus 30% and 70% for the OSCCs (P = .004). CONCLUSIONS: Present data suggest that OVCs are characterized by a lower degree of CIN and tumor heterogeneity than OSCCs, such that they appear as "frozen" in an early stage of DNA near-diploid aneuploidy, as previously observed for oral preneoplastic lesions. These DI characteristics, which can easily be obtained by hr DNA-FCM, appear to reflect the well-known differences in aggressiveness and prognosis of OVCs and OSCCs.

Chromosomal aberrations and aneuploidy in oral potentially malignant lesions: distinctive features for tongue.

BACKGROUND: The mucosae of the oral cavity are different at the histological level but appear all equally exposed to common genotoxic agents. As a result of this exposure, changes in the mucosal epithelia may develop giving rise to Oral Potentially Malignant Lesions (OPMLs), which with time may in turn progress to Oral Squamous Cell Carcinomas (OSCCs). Therefore, much effort should be devoted to identify features able to predict the likeliness of progression associated with an OPML. Such features may be helpful in assisting the clinician to establish both appropriate therapies and follow-up schedules. Here, we report a pilot study that compared the occurrence of DNA aneuploidy and chromosomal copy number aberrations (CNAs) in the OPMLs from different oral anatomical subsites. METHODS: Samples from histologically diagnosed OPMLs were processed for high resolution DNA flow cytometry (hr DNA-FCM) in order to determine the relative DNA content expressed by the DNA index (DI). Additionally, array-Comparative Genomic Hybridization (a-CGH) analysis was performed on DNA obtained from diploid nuclei suspensions directly. When aneuploid nuclei were detected, these were physically separated from diploid nuclei on the base of their DI values by means of a DNA-FCM-Sorter in order to improve the a-CGH analysis. RESULTS: Tongue OPMLs were more frequently associated with DNA aneuploidy and CNAs than OPMLs arising from all the other mucosal subsites. CONCLUSIONS: We suggest that the follow-up and the management of the patients with tongue OPMLs should receive a distinctive special attention. Clearly, this hypothesis should be validated in a prospective clinical study.

Gene expression deregulation by KRAS G12D and G12V in a BRAF V600E context.

BACKGROUND: KRAS and BRAF mutations appear of relevance in the genesis and progression of several solid tumor types but the co-occurrence and interaction of these mutations have not yet been fully elucidated. Using a microsatellite stable (MSS) colorectal cancer (CRC) cell line (Colo741) having mutated BRAF and KRASWT, we also aimed to investigate the KRAS-BRAF interaction. Gene expression profiles for control KRASWT, KRAS G12V and KRAS G12D transfected cells were obtained after cell clone selection and RT-PCR screening. Extensive qPCR was performed to confirm microarray data. RESULTS: We found that the KRAS G12V state deregulated several genes associated to cell cycle, apoptosis and nitrogen metabolism. These findings indicated a reduced survival and proliferation with respect to the KRASWT state. The KRAS G12D state was, instead, characterized by several other distinct functional changes as for example those related to chromatin organization and cell-cell adhesion without affecting apoptosis related genes. CONCLUSION: These data predict that the G12D mutation may be more likely selected in a BRAF mutated context. At the same time, the presence of the KRAS G12V mutation in the cells escaping apoptosis and inducing angiogenesis via IL8 may confer a more aggressive phenotype. The present results get along with the observations that CRCs with G12V are associated with a worse prognosis with respect to the WT and G12D states and may help identifying novel CRC pathways and biomarkers of clinical relevance.

The C-terminal domain of the transcriptional corepressor CtBP is intrinsically unstructured.

C-terminal binding proteins (CtBPs) are moonlighting proteins involved in nuclear transcriptional corepression and in Golgi membrane tubule fission. Structural information on CtBPs is available for their substrate-binding domain, responsible for transcriptional repressor recognition/binding, and for the nucleotide-binding domain, involved in NAD(H)-binding and dimerization. On the contrary, little is known about the structure of CtBP C-terminal region ( approximately 90 residues), hosting sites for post-translational modifications. In the present communication we apply a combined approach based on bioinformatics, nuclear magnetic resonance, circular dichroism spectroscopy, and small-angle X-ray scattering, and we show that the CtBP C-terminal region is intrinsically unstructured in the full-length CtBP and in constructs lacking the substrate- and/or the nucleotide-binding domains. The flexible nature of this protein region, and its structural transitions, may be instrumental for CtBP recognition and binding to diverse molecular partners.

GABP complex regulates transcription of eIF6 (p27BBP), an essential trans-acting factor in ribosome biogenesis.

Eukaryotic initiation factor 6 (eIF6, alias p27BBP) is required for the biogenesis of 60S ribosomal subunits. eIF6 expression levels are tightly regulated in vivo, where they correlate with cellular growth. We analyzed how transcriptional regulation of eIF6 is achieved. We show that the human eIF6 promoter contains consensus sites for the GABP (GA-binding protein) transcription factor complex. Functional analysis of GABP consensus sequences by point mutations, EMSA (electrophoretic mobility shift assay) and a dominant negative mutant indicates that GABP is essential for eIF6 promoter activity. These data strengthen the hypothesis that GABP is a global regulator of ribosome synthesis.

Quinazolinedione SIRT6 inhibitors sensitize cancer cells to chemotherapeutics.

The NAD(+)-dependent sirtuin SIRT6 is highly expressed in human breast, prostate, and skin cancer where it mediates resistance to cytotoxic agents and prevents differentiation. Thus, SIRT6 is an attractive target for the development of new anticancer agents to be used alone or in combination with chemo- or radiotherapy. Here we report on the identification of novel quinazolinedione compounds with inhibitory activity on SIRT6. As predicted based on SIRT6's biological functions, the identified new SIRT6 inhibitors increase histone H3 lysine 9 acetylation, reduce TNF-α production and increase glucose uptake in cultured cells. In addition, these compounds exacerbate DNA damage and cell death in response to the PARP inhibitor olaparib in BRCA2-deficient Capan-1 cells and cooperate with gemcitabine to the killing of pancreatic cancer cells. In conclusion, new SIRT6 inhibitors with a quinazolinedione-based structure have been identified which are active in cells and could potentially find applications in cancer treatment.

Human sirtuins: an overview of an emerging drug target in age-related diseases and cancer.

Sir2-like proteins (Sirtuins) are a class of enzymes conserved throughout the kingdoms of life. In fact, from Archaea to Mammals, these (class III) NAD+-dependent deacetylases catalyse the removal of the acetyl moiety from a substrate protein. Sirtuins show a conserved central catalytic domain with two more variable amino- and carboxy-terminal flanking regions. Amino acid comparison of these central conserved catalytic core sequences allows us to divide Sirtuins into five different classes (I, II, III, IV and U). These proteins differ in their subcellular localization (i.e. in Eukaryotes they can be found in the nucleus, cytoplasm or mitochondria). In humans there are seven Sirtuins (SIRT1-7) that are implicated in various physiological processes including aging and age-related disorders such as neoplasms, cardiovascular, metabolic and neurodegenerative diseases, and inflammation. Nowadays, the estimated life expectancy is definitely longer than in the past thus, we may consider all aging-related problems as having a strong social impact. Consequently, Sirtuins are emerging, particularly from a pharmacological point of view, as new and valuable drug targets.

Oral cancer genesis and progression: DNA near-diploid aneuploidization and endoreduplication by high resolution flow cytometry.

Oral potentially malignant lesions (OPMLs) with dysplasia and aneuploidy are thought to have a high risk of progression into oral squamous cell carcinomas (OSCCs). Non-dysplastic "oral distant fields" (ODFs), characterized by clinically normal appearing mucosa sited at a distance from co-existing OPMLs, and non-dysplastic OPMLs may also represent an early pre-cancerous state. ODFs, OPMLs without and with dysplasia and OSCCs were investigated by high resolution DNA content flow cytometry (FCM). ODFs and OPMLs without dysplasia were DNA aneuploid respectively in 7/82 (8.5%) and 25/109 (23%) cases. "True normal oral mucosa" and human lymphocytes from healthy donors were DNA diploid in all cases and were used as sex specific DNA diploid controls. Dysplastic OPMLs and OSCCs were DNA aneuploid in 12/26 (46%) and 12/13 (92%) cases. The DNA aneuploid sublines were characterized by the DNA Index (DI not =1). Aneuploid sublines in ODFs and in non-dysplastic and dysplastic OPMLs were near-diploid (DI<1.4) respectively in all, 2/3 and 1/3 of the cases. DNA aneuploid OSCCs, instead, were characterized prevalently by multiple aneuploid sublines (67%), which were commonly (57%) high-aneuploid (DI> or =1.4). DNA near-diploid aneuploid sublines in ODFs and OPMLs appear as early events of the oral carcinogenesis in agreement with the concept of field effect. Near-diploid aneuploidization is likely to reflect mechanisms of loss of symmetry in the chromosome mitotic division. High DNA aneuploid and multiple sublines in OPMLs with dysplasia and OSCCs suggest, instead, mechanisms of "endoreduplication" of diploid and near-diploid aneuploid cells and chromosomal loss. High resolution DNA FCM seems to enable the separation of subsequent progression steps of the oral carcinogenesis.

Overexpression of p27BBP in head and neck carcinomas and their lymph node metastases.

BACKGROUND: p27(BBP) is a regulator of ribosome assembly and an essential nuclear and cytoplasmic component of eukaryotes. METHODS: We investigated the immunochemical distribution of p27(BBP) in head and neck carcinomas, in the associated normal mucosa, and in regional lymph nodes. RESULTS: p27(BBP) is detectable in mucosal cells but is overexpressed in carcinomas, highly concentrated in large polymorphous nucleoli, and even larger and more evident in lymph node metastatic foci. Western blotting confirms increased p27(BBP) in carcinomas versus normal mucosa and also in metastatic versus normal lymph nodes. The overexpression of p27(BBP) corresponds to mRNA upregulation in carcinomas. Unexpectedly, a 52-kDa band specifically reacting with antibodies to p27(BBP) was observed in several carcinomas. CONCLUSIONS: p27(BBP) alterations are common events in the transition to malignancy and are probably involved in squamous carcinoma progression. Immune reagents raised to p27(BBP) may provide additional diagnostic tools for surgical pathology of tumor boundaries and lymph nodes. The 52-kDa band may represent an abnormal form of p27(BBP) expressed by transformed airway epithelia.

Crystal structure of the glutaredoxin-like protein SH3BGRL3 at 1.6 Angstrom resolution.

We report the 1.6 Angstrom resolution crystal structure of SH3BGRL3, a member of a new mammalian protein family of unknown function. The observed "thioredoxin fold" of SH3BGRL3 matches the tertiary structure of glutaredoxins, even in the N-terminal region where the sequence similarity between the two protein families is negligible. In particular, SH3BGRL3 displays structural modifications at the N-terminal Cys-x-x-Cys loop, responsible for glutathione binding and catalysis in glutaredoxins. The loop hosts a six residue insertion, yielding an extra N-terminal-capped helical turn, first observed here for the thioredoxin fold. This, together with deletion of both Cys residues, results in a substantial reshaping of the neighboring cleft, where glutathione is hosted in glutaredoxins. While not active in redox reaction and glutathione binding, SH3BGRL3 may act as an endogenous modulator of glutaredoxin activities by competing, with its fully conserved thioredoxin fold, for binding to yet unknown target proteins.