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ABSTRACT: The INK4a-ARF locus plays a central role in the development of pancreatic tumors as evidenced by the fact that up to 98% of pancreatic tumor specimens harbored genetic alterations at the INK4a-ARF locus. Interestingly, in addition to the well-known P16(INK4A) (P16) and P14ARF tumor suppressors, the INK4a/ARF locus in pancreas encodes another protein, P12, whose structure, function, and contributions to pancreatic carcinogenesis remain to be elucidated. In the current study, we demonstrated that over-expression of p12 in human pancreatic cancer cells led to cell arrest at the G1 phase and such cell cycle arrest was related to down-regulation of a number of oncogenes, such as c-Jun, Fos, and SEI1. Furthermore, unlike P16, P12 did not retain any cyclin-dependent kinase 4 (CDK4)-inhibitory activity. Instead, P12 exhibited a transactivating activity not found in P16. We also examined the genetic status of p12 in a cohort of 40 pancreatic tumor specimens and found that p12 alteration was prevalent in pancreatic tumors with an incidence of 70% (28/40). These results support that P12 is a tumor suppressive protein distinct from P16, and its genetic inactivation is associated with pancreatic carcinogenesis.
Biochemical and Biophysical Research Communications 05/2013; · 2.48 Impact Factor
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ABSTRACT: Recent identification of an enhancer element, RD(INK4/ARF) (RD), in the prominent INK4/ARF locus provides a novel mechanism to simultaneously regulate the transcription of p15(INK4B) (p15), p14(ARF) , and p16(INK4A) (p16) tumor suppressor genes. While genetic inactivation of p15, p14(ARF) , and p16 in human tumors has been extensively studied, little is known about genetic alterations of RD and its impact on p15, p14(ARF) , and p16 in human cancer. The purpose of this study was to investigate the potential existence of genetic alterations of RD in human cancer cells. DNAs extracted from 17 different cancer cell lines and 31 primary pheochromocytoma tumors were analyzed for deletion and mutation of RD using real-time PCR and direct DNA sequencing. We found that RD was deleted in human cancer cell lines and pheochromocytoma tumors at frequencies of 41.2% (7/17) and 13.0% (4/31), respectively. While some of these RD deletion events occurred along with deletions of the entire INK4/ARF locus, other RD deletion events were independent of genetic alterations in p15, p14(ARF) , and p16. Furthermore, the status of RD was poorly associated with the expression of p15, p14(ARF) , and p16 in tested cancer cell lines and tumors. This study demonstrates for the first time that deletion of the RD enhancer is a prevalent event in human cancer cells. Its implication in carcinogenesis remains to be further explored. © 2012 Wiley Periodicals, Inc.
Molecular Carcinogenesis 10/2012; · 3.16 Impact Factor
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ABSTRACT: Atorvastatin and suberoylanilide hydroxamic acid (SAHA) were evaluated for chemoprevention of mouse lung tumors. In Experiment 1, lung tumors were induced by vinyl carbamate in strain A/J mice followed by 500 mg/kg SAHA, 60 or 180 mg/kg atorvastatin, and combinations containing SAHA and atorvastatin administered in their diet. SAHA and both combinations, but not atorvastatin, decreased the multiplicity of lung tumors, including large adenomas and adenocarcinomas with the combinations demonstrating the greatest efficacy. In Experiment 2, lung tumors were induced by 4-(methylnitrosoamino)-1-(3-pyridyl)-1-butanol in strain A/J mice followed by 180 mg/kg atorvastatin, 500 mg/kg SAHA, or both drugs administered in the diet. SAHA and the combination of both drugs, but not atorvastatin alone, decreased the multiplicity of lung tumors and large tumors, with the combination demonstrating greater efficacy. In Experiment 3, lung tumors were induced by 1,2-dimethylhydrazine in Swiss-Webster mice followed by 160 mg/kg atorvastatin, 400 mg/kg SAHA, or a combination of both drugs administered in the diet. SAHA and the combination, but not atorvastatin, decreased the multiplicity of lung tumors with the combination demonstrating greater efficacy. The multiplicity of colon tumors was decreased by SAHA, atorvastatin, and the combination, without any significant difference in their efficacy. mRNA expression analysis of lung tumor bearing mice suggested that the enhanced chemopreventive activity of the combination is related to atorvastatin modulation of DNA repair, SAHA modulation of angiogenesis, and both drugs modulating invasion and metastasis pathways. Atorvastatin demonstrated chemoprevention activity as indicated by the enhancement of the efficacy of SAHA to prevent mouse lung tumors.
International Journal of Cancer 12/2011; 131(6):1277-86. · 5.44 Impact Factor
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ABSTRACT: OLP is a relatively common immune-mediated mucosal condition with a predilection for middle-aged women. Although classified as a premalignant condition, this classification remains controversial. Using stringent diagnostic criteria, some authors have found that OLP patients are not at increased risk for oral SCC. Credible but limited genetic evidence also indicates that epithelial tissues from OLP patients diagnosed using stringent criteria differs from premalignant or malignant oral lesions but is similar to epithelium from benign oral lesions. To further investigate this genetic line of evidence, biopsy specimens diagnosed as fibroma, OLP, low-grade dysplasia, high-grade dysplasia, and SCC were retrieved from the archives of the Oral Pathology Consultants at the Ohio State University. Using laser capture microdissection, tissue of interest was captured from each case and DNA subsequently extracted. Fluorescently labeled PCR primers were used to amplify DNA at 3 tumor suppressor gene loci (3p14.2, 9p21, and 17p13) and evaluated for LOH or microsatellite instability (MSI). OLP was found to be significantly different from low-grade dysplasia, high-grade dysplasia, and SCC when LOH/MSI was found at more than 1 loci (P = .011, P = .032, P = .003), but not different from benign fibromas (P = .395). In agreement with previous studies, well-documented cases of OLP diagnosed using stringent criteria exhibit a genetic profile more similar to a benign or reactive process than a premalignant/malignant one. These findings do not support the classification of OLP as a premalignant condition.
Oral surgery, oral medicine, oral pathology, oral radiology, and endodontics 09/2011; 112(3):359-66. · 1.50 Impact Factor
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ABSTRACT: Little is known about the potential involvement of the oncoprotein gankyrin in human oral cancer progression. In this study, the levels of gankyrin mRNA and protein expression were assessed in human oral epithelial cell lines, at-risk normal oral tissues, premalignant oral lesions, and primary oral squamous cell carcinomas (OSCCs).
Biopsies included 6 oral epithelial cell lines, 32 OSCC specimens for qRT-PCR analysis, 27 OSCC specimens and 12 premalignant oral lesions for immunohistochemical analysis.
Gankyrin was overexpressed in all tested oral epithelial cell lines and the majority of OSCC specimens (32/32 (100%) and 21/27 (71%) at the mRNA and protein levels, respectively). Moreover, 6/12 of premalignant oral lesions overexpressed gankyrin protein.
Gankyrin overexpression is a prevalent event in human oral cancer and occurs during the early stages of oral carcinogenesis, thus being a viable therapeutic or chemopreventive target in oral cancer.
Anticancer research 09/2011; 31(9):2683-92. · 1.73 Impact Factor
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ABSTRACT: Cervical cancer is the second most common female cancer worldwide, and it remains a challenge to manage preinvasive and invasive lesions. Food-based cancer prevention entities, such as black raspberries and their derivatives, have demonstrated a marked ability to inhibit preclinical models of epithelial cancer cell growth and tumor formation. Here, we extend the role of black raspberry-mediated chemoprevention to that of cervical carcinogenesis.
Three human cervical cancer cell lines, HeLa (HPV16-/HPV18+, adenocarcinoma), SiHa (HPV16+/HPV18-, squamous cell carcinoma) and C-33A (HPV16-/HPV18-, squamous cell carcinoma), were treated with a lyophilized black raspberry ethanol extract (RO-ET) at 25, 50, 100 or 200μg/ml for 1, 3 and 5days, respectively. Cell proliferation was measured by WST1 (tetrazolium salt cleavage) assays. Flow cytometry (propidium iodide and Annexin V staining) and fluorescence microscopy analysis were used to measure apoptotic cell changes.
We found that non-toxic levels of RO-ET significantly inhibited the growth of human cervical cancer cells, in a dose-dependent and time-dependent manner to a maximum of 54%, 52% and 67%, respectively (p<0.05). Furthermore, cell growth inhibition was persistent following short-term withdrawal of RO-ET from the culture medium. Flow cytometry and fluorescence microscopy demonstrated RO-ET-induced apoptosis in all cell lines.
Black raspberries and their bioactive components represent promising candidates for future phytochemical-based mechanistic pathway-targeted cancer prevention strategies.
Gynecologic Oncology 08/2011; 123(2):401-6. · 3.89 Impact Factor
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ABSTRACT: It is estimated that oral cancers will present with more than 400,000 new cases worldwide, establishing this malignancy as
the sixth most common cancer globally. In association with the “field” effects of these epithelial neoplasias, oral cancers
are marked by high frequencies of local invasion and recurrence, and 5-year survival times of less than 60% depending upon
the stage of the initial lesion. Epidemiological studies support the hypothesis that a decreased oral cancer incidence is
associated with lifestyle changes, including diminished exposure to alcohol and tobacco and increased dietary incorporation
of fruits and vegetables. Food-based approaches to cancer prevention, including dietary exposure to black raspberries, emphasize
the potential for complex mixtures of bioactive food components to inhibit several processes and mechanistic states within
a multistep oral carcinogenesis archetype. Both pre-clinical and clinical models of black raspberry administration have demonstrated
a striking capacity of black raspberries and their derivatives to specifically modulate gene transcriptional profiles in a
manner that favors oral cancer prevention strategies.
KeywordsOral cancer-Clinical trial-Black raspberries-Chemoprevention-Dietary intervention-Biomarkers-Nutraceutical-Whole-food intervention-Cancer risk reduction-Phytochemical-Bioactive food components
12/2010: pages 259-280;
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ABSTRACT: It is estimated that there will be 35,720 cases and 7,600 deaths resulting from oral cancer in the United States this year.
Even more common worldwide, oral cancer is the 6th most prevalent cancer internationally, the majority of which are squamous
cell carcinomas that have been etiologically linked to carcinogens in tobacco. Current surgical and adjuvant therapies remain
only modestly effective and are often associated with significant physical and physiological side effects. Therefore, alternative
or complementary intervention strategies, such as oral cancer chemoprevention, should be developed and tested in appropriate
preclinical animal models of experimental oral carcinogenesis. The best characterized model of chemically-induced oral cancer,
the hamster cheek pouch, has been employed to evaluate the ability of dietary lyophilized black raspberries (LBR) to inhibit
oral tumors. Tumors induced by DMBA were significantly inhibited by the administration of dietary LBR. A discussion of berry
components and inhibition of oral cancers in hamsters, rats, and mice is included. These data show that administration of
berries or berry components effectively inhibit chemically-induced tumor formation in several comparative animal models of
experimental oral carcinogenesis.
KeywordsOral cancer-Black raspberries-Berries-DMBA-Chemoprevention-Nutraceutical-Animal model-Preclinical-Food-based-Cancer prevention-Dietary-Hamster cheek pouch
12/2010: pages 189-207;
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ABSTRACT: Ankyrin repeat (AR) proteins are one of the most abundant classes of repeat proteins and are involved in numerous physiological processes. These proteins are composed of various numbers of AR motifs stacked in a nearly linear fashion to adopt an elongated and nonglobular architecture. One salient feature prevalent in such a structural unit is the TPLH tetrapeptide or a close variant, T/SxxH, which initiates the helix-turn-helix conformation and presumably contributes to conformational stability through a hydrogen-bonding network. In the present study, we investigated the roles of T/SxxH motif in the stability, structure, and function of AR proteins by a systematic and rationalized mutagenic study on, followed by biochemical and biophysical characterization of, gankyrin, an oncogenic protein composed of seven ARs and six T/SxxH tetrapeptides, and P16, a tumor suppressor with four ARs but no TPLH tetrapeptide. Our results showed that this tetrapeptide is ineffectual on global structure and function, but contributes significantly to conformational stability when its stabilizing potentials are fully realized in the local conformation, including (1) the intra-AR hydrogen bonding involving the hydroxyl group; (2) the intra-AR and inter-AR hydrogen bonds involving the imidazole ring; and (3) the hydrophobic interaction associated with the Thr-methyl group. Considering that the capping and close-to-capping units tend to have more sequence diversity and more conformational variation, it could be also generally true that a T/SxxH motif close to the terminal repeats contributes little or even negatively to stability with respect to Ala substitution, but substantially stabilizes the global conformation when located in the middle of a long stretch of ARs.
Journal of Molecular Biology 05/2010; 399(1):168-81. · 4.00 Impact Factor
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ABSTRACT: In spite of its central roles in cell cycle progression, senescence, and aging, knowledge about the posttranslational regulation of P16 (also known as INK4A and MTS1) remains limited. While it has been reported that P16 could be phosphorylated at Ser7, Ser8, Ser140, and Ser152, the corresponding kinases have not been identified yet. Here we report that IKKbeta, a primary kinase for IkappaBalpha phosphorylation, is involved in P16 phosphorylation. Immunoprecipitation and kinase assays showed that IKKbeta specifically binds to P16 and phosphorylates P16 at Ser8 in WI38 cells. Biochemical characterization of phosphomimetic Ser-->Glu P16 mutants demonstrated that phosphorylation at Ser8 of P16 brings about a significant loss of its cyclin-dependent kinase (CDK) 4-inhibitory activity while P16 retains structurally and functionally intact upon phosphorylation at Ser7, Ser140, and Ser152. Our results reveal the novel role of IKKbeta in P16 phosphorylation and broaden our understanding of the regulation of P16.
Biochemical and Biophysical Research Communications 02/2010; 393(3):504-8. · 2.48 Impact Factor
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ABSTRACT: Ankyrin repeat (AR) proteins are one of the most abundant repeat protein classes in nature, and they are involved in numerous physiological processes through mediating protein/protein interactions. The repetitive and modular architecture of these AR proteins may lead to biochemical and biophysical properties distinct from those of globular proteins. It has been demonstrated that like most globular proteins, AR proteins exhibit a two-state, cooperative transition in chemical- and heat-induced unfolding. However, the biophysical characteristics underlying such cooperative unfolding remain to be further investigated. In the present study, we evaluated the conformational stability of a group of cyclin-dependent kinase (CDK) 4-interacting AR proteins, P16, P18, IkappaBalpha, gankyrin, and their truncated mutants under different conditions, including the presence of denaturants, temperature, and pH. Our results showed that the first four N-terminal ARs are required to form a potent and stable CDK4 modulator. Moreover, in spite of their similarities in skeleton structure, CDK4 binding, and cooperative unfolding, P16, P18, IkappaBalpha, and gankyrin exhibited considerably different biophysical properties with regard to the conformational stability, and these differences mainly resulted from the discrepancies in the primary sequence of the relatively conserved AR motifs. Our results also demonstrated that these sequence discrepancies are able to influence the function of AR proteins to a certain extent. Overall, our results provide important insights into understanding the biophysical properties of AR proteins.
Biochemistry 05/2009; 48(19):4050-62. · 3.42 Impact Factor
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ABSTRACT: Proliferative verrucous leukoplakia (PVL) represents a rare but highly aggressive form of oral leukoplakia with > 70% progressing to malignancy. Yet, PVL remains biologically and genetically poorly understood. This study evaluated the cell cycle regulatory genes, p16INK4a and p14ARF, for homozygous deletion, loss of heterozygosity, and mutation events in 20 PVL cases. Deletion of exon 1beta, 1alpha, or 2 was detected in 40%, 35%, and 0% of patients, respectively. Deletions of exons 1alpha and 1beta markedly exceed levels reported in non-PVL dysplasias and approximate or exceed levels reported in oral squamous cell carcinomas. Allelic imbalance was assessed for markers reported to be highly polymorphic in squamous cell carcinomas and in oral dysplasias. Loss of heterozygosity was detected in 35.3%, 26.3%, and 45.5% of PVLs for the markers IFNalpha, D9S1748, and D9S171, respectively. INK4a and ARF sequence alterations were detected in 20% and 10% of PVL lesions, accordingly. These data show, for the first time, that both p16INK4a and p14ARF aberrations are common in oral verrucous leukoplakia; however, the mode and incidence of inactivation events differ considerably from those reported in non-PVL oral premalignancy. Specifically, concomitant loss of p16INK4a and p14ARF occurred in 45% of PVL patients greatly exceeding loss reported in non-PVL dysplastic oral epithelium (15%). In addition, p14ARF exon 1beta deletions were highly elevated in PVLs compared with non-PVL dysplasias. These data illustrate that molecular alterations, even within a specific genetic region, are associated with distinct histologic types of oral premalignancy, which may affect disease progression, treatment strategies, and ultimately patient prognosis.
Cancer Epidemiology Biomarkers & Prevention 12/2008; 17(11):3179-87. · 4.12 Impact Factor
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ABSTRACT: The prevalence of p16(INK4A)/Cdkn2a genetic alterations in human oral cancers indicates that the p16 gene could be a potent and appropriate target for novel intervention. While chemically induced hamster cheek pouch (HCP) tumors are regarded as an appropriate surrogate model for human oral cancers because of their similarities to human oral cancers in both histology and genetics, little is known about the genetic events in the p16 gene in the HCP tumor model. The purpose of this study was to evaluate chemically induced HCP tumor specimens for potential inactivating p16 alterations. HCP tumors were induced with 7, 12-dimethylbenz(a)anthracene (DMBA), and DNA extracted from 34 such specimens were analyzed for homozygous/hemizygous deletions, aberrant methylation of 5' CpG islands, and point mutations using real-time multiplex PCR, methylation-specific PCR, and direct sequencing/cold single strand conformation polymorphism (SSCP), respectively. Homozygous deletions, hemizygous deletions, aberrant methylation of 5'-CpG islands, and point mutation were identified in 11, 4, 9, and 1 of 34 specimens, respectively. While the overall incidence of p16 alterations was 70.6% (24 of 34 specimens), the majority of inactivating events (67.6%) stemmed from deletion or methylation, which is consistent with the observations found in human oral SCCs. Our results show the resemblance between chemically induced HCP tumors and their human counterparts in p16 genetic alterations, and strongly support the use of DMBA-induced HCP tumor model in evaluating novel p16-targeted therapy and prevention of human oral SCCs.
Molecular Carcinogenesis 03/2008; 47(10):733-8. · 3.16 Impact Factor
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ABSTRACT: TGFBR1*6A is a common hypomorphic variant of the type I transforming growth factor (TGF)-beta receptor (TGFBR1), which transduces TGF-beta growth inhibitory signals less effectively than TGFBR1. Recent studies suggest that TGFBR1*6A confers a selective growth advantage to both normal appearing and cancerous epithelial cells in the presence of TGF-beta. We have previously shown that TGFBR1*6A is somatically acquired in head and neck and colon cancer (10). Using microdissected tissues, we show that TGFBR1*6A is somatically acquired by stromal and epithelial cells adjacent to colorectal and head and neck tumors. Somatic acquisition of the TGFBR1*6A allele is not accompanied by acquisition of other tumor-specific mutations. Furthermore, lymphocytes located within the stroma or the normal appearing epithelium do not have evidence of TGFBR1*6A acquisition. The highest TGFBR1*6A/TGFBR1 allelic ratio is observed at the tumor's edge, and traces of TGFBR1*6A are detected as far as 2 cm away from the tumor, which is suggestive of centrifugal spread of cells that harbor TGFBR1*6A. Assessment of CDH1 and CDH2 expression does not indicate epithelial-mesenchymal transformation. The results suggest that TGFBR1*6A somatic acquisition is a critical event in the early stages of cancer development that is associated with field cancerization. They also represent the first human report of somatically acquired altered stromal TGF-beta signaling during oncogenesis and the first report of a concordant mutation in the stromal and epithelial compartments in colon cancer.
Human Molecular Genetics 01/2008; 16(24):3128-35. · 7.64 Impact Factor
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ABSTRACT: Clinical data show a strong correlation between tobacco and alcohol use and the development of oral squamous cell carcinoma (SCC). While this association implies that the oral mucosa actively metabolizes carcinogens, there is little information which depicts the carcinogen metabolizing enzymes within the oral cavity. Glutathione S-transferases (GSTs) primary function is to detoxify carcinogens by increasing their water solubility, GSTs represent key carcinogen metabolizing enzymes. Notably, individuals with a null phenotype for certain GST isoforms are at an increased risk to develop cancer. This study investigated the function and distribution of GSTs in human oral tissues. Our results from this pilot study showed a trend towards higher GST activities in SCC tissues relative to normal mucosa. Also, relative to normal tissues, the SCC and epithelial dysplasia samples showed a more intense and uniform GST intracellular distribution. GST activities are increased in many high grade cancers. Similarly, our data suggest that GST upregulation occurs in at least a subset of precancerous and malignant oral lesions.
Clinical Medicine: Oncology 01/2008; 2:159-68.
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ABSTRACT: A number of hereditary syndromes have been found to be associated with pheochromocytoma development, but there is a paucity of data regarding secondary molecular events, such as downregulation of the p16INK4A/Cdkn2a gene (hereafter p16), contributing to pheochromocytoma tumorigenesis. Using tissue microarray and immunohistochemistry, we evaluated the expression of p16 in 31 pheochromocytoma tumor specimens. Our results showed that the p16 gene was expressed at low level or even not expressed in all but one specimens [30/31 (96.8%)], indicative of the prevalence of p16 downregulation in pheochromocytomas. In contrast, high expression of pl6 was observed in the majority of control "normal" specimens [5/7 (71.6%)]. To further investigate the molecular mechanisms underlying pl6 downregulation in pheochromocytomas, we used quantitative real-time PCR, methylation-specific PCR, and direct DNA sequencing to analyze these specimens for potential genetic alterations of the p16 gene. Deletions and aberrant CpG methylation of pl6 were identified in 9 (29.0%) and 11 (35.5%) specimens, respectively, while one specimen harbored a point mutation, Ala --> Pro at residue 20 of P16, and this mutation led to an eightfold decrease in the CDK4-inhibitory activity of P16. The overall frequency of pl6 genetic alterations is 67.7%. Taken together, our results demonstrate that reduced expression of pl6 is a common event in human pheochromocytomas, and the primary cause for such downregulation is inactivating genetic abnormalities in the p16 gene.
Gene Expression 01/2008; 14(4):207-16. · 1.31 Impact Factor
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ABSTRACT: Protein-protein interactions usually involve a large number of residues; thus it is difficult to elucidate functional and structural roles of specific residues located in the interface. This problem is particularly challenging for ankyrin repeat proteins (ARs), which consist of linear arrays of small repeating units and play critical roles in almost every life process via protein-protein interactions, because the residues involved are discontinuously dispersed in both the ARs and their partners. Our previous studies showed that while both specific CDK4 inhibitor p16INK4A (P16) and gankyrin bind to cyclin-dependent kinase 4 (CDK4) in similar fashion, only P16 inhibits the kinase activity of CDK4. While this could explain why P16 is a tumor suppressor and gankyrin is oncogenic, the structural basis of these contrasting properties was unknown. Here we show that a double mutant of gankyrin, L62H/I79D, inhibits the kinase activity of CDK4, similar to P16, and such CDK4-inhibtory activity is associated with the I79D but not L62H mutation. In addition, mutations at I79 and L62 bring about a moderate decrease in the stability of gankyrin. Further structural and biophysical analyses suggest that the substitution of Ile79 with Asp leads to local conformational changes in loops I-III of gankyrin. Taken together, our results allow the dissection of the "protein-protein binding" and "CDK4 inhibition" functions of P16, show that the difference between tumor suppressing and oncogenic functions of P16 and gankyrin, respectively, mainly resides in a single residue, and provide structural insight to the contrasting biological functions of the two AR proteins.
Journal of Molecular Biology 12/2007; 373(4):990-1005. · 4.00 Impact Factor
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Boris Pasche,
Thomas J Knobloch,
Yansong Bian,
Junjian Liu,
Sharbani Phukan,
Diana Rosman,
Virginia Kaklamani,
Lisa Baddi,
Farida S Siddiqui,
Wendy Frankel, [......],
Chiang-Ching Huang,
Trinidad Caldes,
Antonio Di Cristofano,
Heather Hampel,
IngMarie Nilsson,
Gunnar von Heijne,
Riccardo Fodde,
V V V S Murty,
Albert de la Chapelle, Christopher M Weghorst
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ABSTRACT: TGFBR1*6A is a common polymorphism of the type I transforming growth factor beta receptor (TGFBR1). Epidemiological studies suggest that TGFBR1*6A may act as a tumor susceptibility allele. How TGFBR1*6A contributes to cancer development is largely unknown.
To determine whether TGFBR1*6A is somatically acquired by primary tumors and metastases during cancer development and whether the 3-amino acid deletion that differentiates TGFBR1*6A from TGFBR1 is part of the mature receptor or part of the signal sequence and to investigate TGFBR1*6A signaling in cancer cells.
Tumor and germline tissues from 531 patients with a diagnosis of head and neck, colorectal, or breast cancer recruited from 3 centers in the United States and from 1 center in Spain from June 1, 1994, through June 30, 2004. In vitro translation assays, MCF-7 breast cancer cells stably transfected with TGFBR1*6A, TGFBR1, or the vector alone, DLD-1 colorectal cancer cells that endogenously carry TGFBR1*6A, and SW48 colorectal cancer cells that do not carry TGFBR1*6A.
TGFBR1*6A somatic acquisition in cancer. Determination of the amino terminus of the mature TGFBR1*6A and TGFBR1 receptors. Determination of TGF-beta-dependent cell proliferation.
TGFBR1*6A was somatically acquired in 13 of 44 (29.5%) colorectal cancer metastases, in 4 of 157 (2.5%) of colorectal tumors, in 4 of 226 (1.8%) head and neck primary tumors, and in none of the 104 patients with breast cancer. TGFBR1*6A somatic acquisition is not associated with loss of heterozygosity, microsatellite instability, or a mutator phenotype. The signal sequences of TGFBR1 and TGFBR1*6A are cleaved at the same site resulting in identical mature receptors. TGFBR1*6A may switch TGF-beta growth inhibitory signals into growth stimulatory signals in MCF-7 breast cancer cells and in DLD-1 colorectal cancer cells.
TGFBR1*6A is somatically acquired in 29.5% of liver metastases from colorectal cancer and may bestow cancer cells with a growth advantage in the presence of TGF-beta. The functional consequences of this conversion appear to be mediated by the TGFBR1*6A signal sequence rather than by the mature receptor. The results highlight a new facet of TGF-beta signaling in cancer and suggest that TGFBR1*6A may represent a potential therapeutic target in cancer.
JAMA The Journal of the American Medical Association 11/2005; 294(13):1634-46. · 30.03 Impact Factor
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ABSTRACT: Recent studies showed that p34(SEI-1), also known as TRIP-Br1 or SEI-1, plays a dual role in the regulation of cell-cycle progression. It exhibits the transactivation activity and regulates a number of genes required for G1/S transition, while it also binds and activates cyclin-dependent kinase 4 (CDK4) independent of the inhibitory activity of p16. The goals of this paper are to further dissect the two roles and to compare the functions between SEI-1 and p16. (i) Yeast one-hybrid-based random mutagenesis was first used to identify a number of SEI-1 residues important for LexA-mediated transactivation, including residues L51, K52, L53, H54, L57, and L69 located within the heptad repeat (residues 30-88), a domain required for LexA-mediated transactivation, and two residues M219 and L228 at the C-terminal segment that contributes to transactivation through modulating the heptad repeat. (ii) The functional significance of these residues was further confirmed by site-directed mutagenesis. It was also shown that the heptad repeat-involving transactivation is distinct from the well-known acidic region-involving transactivation. (iii) Yeast two-hybrid-based binding analysis was made possible with the transactivation-negative SEI-1 mutants, and the results showed that some of such mutants retain full ability to bind and activate CDK4. (iv) Site-specific mutants of CDK4 were used to show that there are notable differences among SEI-1, p16, and cyclin D2 in binding to CDK4. (v) The expression levels of SEI-1 and p16 were compared in 32 tumor specimens of human squamous cell carcinomas of the head and neck. The results indicate that SEI-1 was consistently overexpressed, while p16 was consistently underexpressed. These results provide important information on the molecular mechanism of the functions of SEI-1 and on the comparison between SEI-1 and p16 at both molecular and cellular levels.
Biochemistry 11/2005; 44(40):13246-56. · 3.42 Impact Factor
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ABSTRACT: Recent studies showed that p34SEI-1, also known as TRIP-Br1 or SEI-1, plays a dual role in the regulation of cell-cycle progression. It exhibits the transactivation activity and regulates a number of genes required for G1/S transition, while it also binds and activates cyclin-dependent kinase 4 (CDK4) independent of the inhibitory activity of p16. The goals of this paper are to further dissect the two roles and to compare the functions between SEI-1 and p16. (i) Yeast one-hybrid-based random mutagenesis was first used to identify a number of SEI-1 residues important for LexA-mediated transactivation, including residues L51, K52, L53, H54, L57, and L69 located within the heptad repeat (residues 30-88), a domain required for LexA-mediated transactivation, and two residues M219 and L228 at the C-terminal segment that contributes to transactivation through modulating the heptad repeat. (ii) The functional significance of these residues was further confirmed by site-directed mutagenesis. It was also shown that the heptad repeat-involving transactivation is distinct from the well-known acidic region-involving transactivation. (iii) Yeast two-hybrid-based binding analysis was made possible with the transactivation-negative SEI-1 mutants, and the results showed that some of such mutants retain full ability to bind and activate CDK4. (iv) Site-specific mutants of CDK4 were used to show that there are notable differences among SEI-1, p16, and cyclin D2 in binding to CDK4. (v) The expression levels of SEI-1 and p16 were compared in 32 tumor specimens of human squamous cell carcinomas of the head and neck. The results indicate that SEI-1 was consistently overexpressed, while p16 was consistently underexpressed. These results provide important information on the molecular mechanism of the functions of SEI-1 and on the comparison between SEI-1 and p16 at both molecular and cellular levels.
Biochemistry - BIOCHEMISTRY-USA. 01/2005; 44(40):13246-13256.
