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1.
Vaccines (Basel) ; 11(7)2023 Jul 05.
Article in English | MEDLINE | ID: mdl-37515019

ABSTRACT

Genital warts (GWs) caused by the human papilloma virus (HPV) are a significant health problem due to high prevalence and rate of recurrence. Bivalent vaccine has been used since the start of the national vaccination program in 2013, making it feasible to study the GW burden in Finland. There is no national and up-to-date information available on the prevalence and the burden of GWs in the various healthcare sectors in Finland. The present study investigated the prevalence, healthcare resource use, and direct medical costs of the treatment of GWs in Finland in 2018 using data in national healthcare registers. GW cases were identified based on diagnoses in public healthcare and GW-related prescription medications. Cost analysis included public healthcare contacts, procedures in private care, and medications. The study showed that approximately 12,000 GWs cases were treated in Finland in 2018. Since less than half of GW diagnoses were recorded in public healthcare registers, determining the exact costs was challenging. The estimated direct treatment costs in 2018 were 2.6 M€, which is higher than the previous estimation in Finland, yet still likely an underestimation of the true burden. These results provide information for the management of the GW burden in Finland.

2.
Vaccine ; 40(29): 3942-3947, 2022 06 23.
Article in English | MEDLINE | ID: mdl-35641360

ABSTRACT

BACKGROUND: Rotavirus (RV) vaccination was included in the Finnish National immunization Program (NIP) in 2009. RotaTeq (RV5) has been used exclusively with a national average vaccination coverage rate (VCR) of > 90%. While previous studies have demonstrated that inpatient rotavirus gastroenteritis (RVGE) admissions declined by as much as 96% in Finnish children ≤ 5 years old following RV vaccination introduction, no study has evaluated long-term protection after vaccination in Finland. In this study, we analyze incidence of hospital outpatient visits and inpatient admissions of gastroenteritis in children up to 7 years of age. METHODS: We first describe the incidence of RVGE, viral gastroenteritis (VGE), and acute gastroenteritis (AGE) for all Finnish children born during 2008-2011. Children were stratified by the year of birth into not-eligible, partially eligible and rotavirus vaccine-eligible (born in 2008, 2009, 2010 and 2011, respectively). Hospital inpatient and outpatient data was collected from the National Care Register for all children from birth until December 31st, 2018. We also studied RVGE incidence during 2014-2017 for children<3 years of age in municipalities with VCRs of 90% and above and municipalities with VCRs below 90%. RESULTS: RVGE incidence decreased significantly soon after implementation of RV vaccination in the NIP. In vaccine-eligible cohorts, no clear peak incidence in the youngest age groups could be observed, and no RVGE cases were observed beyond 6 years after vaccination, in contrast to vaccine ineligible and partially eligible cohorts. Despite an overall high VCR in Finland, regions with high VCR had lower incidence of RVGE than regions with lower VCR. CONCLUSION: Incidence of RVGE has remained low in all age groups during the 10 years following introduction of RV vaccine in the Finnish NIP. Differences in RVGE incidence were observed in regions with high as compared with lower VCR, highlighting the importance of maintaining high vaccination coverage.


Subject(s)
Gastroenteritis , Rotavirus Infections , Rotavirus Vaccines , Rotavirus , Adolescent , Child , Child, Preschool , Finland/epidemiology , Gastroenteritis/epidemiology , Gastroenteritis/prevention & control , Hospitalization , Humans , Immunization Programs , Infant , Rotavirus Infections/epidemiology , Rotavirus Infections/prevention & control , Rotavirus Vaccines/therapeutic use , Vaccination
3.
Cancers (Basel) ; 12(7)2020 Jul 09.
Article in English | MEDLINE | ID: mdl-32660107

ABSTRACT

Some 10-50% of Lynch-suspected cases with abnormal immunohistochemical (IHC) staining remain without any identifiable germline mutation of DNA mismatch repair (MMR) genes. MMR proteins form heterodimeric complexes, giving rise to distinct IHC patterns when mutant. Potential reasons for not finding a germline mutation include involvement of an MMR gene not predicted by the IHC pattern, epigenetic mechanism of predisposition, primary mutation in another DNA repair or replication-associated gene, and double somatic MMR gene mutations. We addressed these possibilities by germline and tumor studies in 60 Lynch-suspected cases ascertained through diagnostics (n = 55) or research (n = 5). All cases had abnormal MMR protein staining in tumors but no point mutation or large rearrangement of the suspected MMR genes in the germline. In diagnostic practice, MSH2/MSH6 (MutS Homolog 2/MutS Homolog 6) deficiency prompts MSH2 mutation screening; in our study, 3/11 index individuals (27%) with this IHC pattern revealed pathogenic germline mutations in MSH6. Individuals with isolated absence of MSH6 are routinely screened for MSH6 mutations alone; we found a predisposing mutation in MSH2 in 1/7 such cases (14%). Somatic deletion of the MSH2-MSH6 region, joint loss of MSH6 and MSH3 (MutS Homolog 3) proteins, and hindered MSH2/MSH6 dimerization offered explanations to misleading IHC patterns. Constitutional epimutation hypothesis was pursued in the MSH2 and/or MSH6-deficient cases plus 38 cases with MLH1 (MutL Homolog 1)-deficient tumors; a primary MLH1 epimutation was identified in one case with an MLH1-deficient tumor. We conclude that both MSH2 and MSH6 should be screened in MSH2/6- and MSH6-deficient cases. In MLH1-deficient cases, constitutional epimutations of MLH1 warrant consideration.

4.
J Surg Oncol ; 113(2): 209-12, 2016 Feb.
Article in English | MEDLINE | ID: mdl-26663236

ABSTRACT

BACKGROUND: The prevalence of desmoid tumors among patients with familial adenomatous polyposis (FAP) is at least 10%, and the prevalence of FAP among desmoid patients varies between 7.5-16%. METHODS: Data included 106 desmoid patients identified from the database of the Department of Pathology, Helsinki University Hospital, years 2000-2012. We evaluated the risk of FAP among patients by using endoscopy and we identified individuals with attenuated FAP by APC gene mutation test. We compared sporadic desmoid patients' and FAP patients' clinical characteristics. RESULTS: Ten of 106 patients already had FAP diagnosis before the desmoid. Eleven patients had had FAP screening already earlier due to desmoid and three of them were found to have FAP. Total of 52 patients participated into prospective screening of FAP. No new cases of FAP were found. The risk of FAP among desmoid tumor patients was 4.8%. In the FAP desmoid group, there were more males and patients were younger than in the sporadic group. Intra-abdominal desmoids were more common in the FAP group. CONCLUSIONS: Patients with desmoid carry an elevated risk of FAP and therefore screening is indicated. Asymptomatic patients with desmoid situated in extra truncal region may not need to be screened.


Subject(s)
Adenomatous Polyposis Coli/diagnosis , Adenomatous Polyposis Coli/epidemiology , Endoscopy, Gastrointestinal , Fibromatosis, Aggressive/complications , Genes, APC , Mutation , Adenomatous Polyposis Coli/genetics , Adolescent , Adult , Aged , Aged, 80 and over , Databases, Factual , Female , Finland/epidemiology , Humans , Male , Middle Aged , Prospective Studies , Risk Assessment , Risk Factors
5.
Genes Chromosomes Cancer ; 53(10): 857-64, 2014 Oct.
Article in English | MEDLINE | ID: mdl-24946964

ABSTRACT

n familial adenomatous polyposis (FAP), 20% of classical and 70% of attenuated/atypical (AFAP) cases remain mutation-negative after routine testing; yet, allelic expression imbalance may suggest an APC alteration. Our aim was to determine the proportion of families attributable to genetic or epigenetic changes in the APC promoter region. We studied 51 unrelated families/cases (26 with classical FAP and 25 with AFAP) with no point mutations in the exons and exon/intron borders and no rearrangements by multiplex ligation-dependent probe amplification (MLPA, P043-B1). Promoter-specific events of APC were addressed by targeted resequencing, MLPA (P043-C1), methylation-specific MLPA, and Sanger sequencing of promoter regions. A novel 132-kb deletion encompassing the APC promoter 1B and upstream sequence occurred in a classical FAP family with allele-specific APC expression. No promoter-specific point mutations or hypermethylation were present in any family. In conclusion, promoter-specific alterations are a rare cause for mutation-negative FAP (1/51, 2%). The frequency and clinical correlations of promoter 1B deletions are poorly defined. This investigation provides frequencies of 1/26 (4%) for classical FAP, 0/25 (0%) for AFAP, and 1/7 (14%) for families with allele-specific expression of APC. Clinically, promoter 1B deletions may associate with classical FAP without extracolonic manifestations.


Subject(s)
Adenomatous Polyposis Coli Protein/genetics , Adenomatous Polyposis Coli/genetics , Point Mutation , Promoter Regions, Genetic , Adolescent , Adult , Aged , Alleles , Base Sequence , Cohort Studies , DNA Methylation , Epigenesis, Genetic , Humans , Loss of Heterozygosity , Middle Aged , Pedigree , Sequence Deletion , Young Adult
6.
Cancer Res ; 74(1): 224-34, 2014 Jan 01.
Article in English | MEDLINE | ID: mdl-24158095

ABSTRACT

The genome-wide accumulation of DNA replication errors known as microsatellite instability (MSI) is the hallmark lesion of DNA mismatch repair (MMR)-deficient cancers. Although testing for MSI is widely used to guide clinical management, the contribution of MSI at distinct genic loci to the phenotype remains largely unexplored. Here, we report that a mononucleotide (T/U)16 tract located in the 3' untranslated region (3'-UTR) of the Ewing sarcoma breakpoint region 1 (EWSR1) gene is a novel MSI target locus that shows perfect sensitivity and specificity in detecting mismatch repair-deficient cancers in two independent populations. We further found a striking relocalization of the EWSR1 protein from nucleus to cytoplasm in MMR-deficient cancers and that the nonprotein-coding MSI target locus itself has a modulatory effect on EWSR1 gene expression through alternative 3' end processing of the EWSR1 gene. Our results point to a MSI target gene-specific effect in MMR-deficient cancers.


Subject(s)
3' Untranslated Regions , Calmodulin-Binding Proteins/biosynthesis , Colorectal Neoplasms/genetics , DNA Mismatch Repair , DNA Repair-Deficiency Disorders , RNA-Binding Proteins/biosynthesis , Calmodulin-Binding Proteins/genetics , Colorectal Neoplasms, Hereditary Nonpolyposis/genetics , HCT116 Cells , HT29 Cells , HeLa Cells , Humans , Microsatellite Instability , RNA, Messenger/biosynthesis , RNA, Messenger/genetics , RNA-Binding Protein EWS , RNA-Binding Proteins/genetics , Transfection
7.
Virchows Arch ; 463(5): 613-21, 2013 Nov.
Article in English | MEDLINE | ID: mdl-23963522

ABSTRACT

The aim of the study was to detect mutations of BRAF oncogene in colorectal cancer and to use this information to identify Lynch syndrome patients. Consecutive cases of primary colorectal cancer (n = 137) were analyzed for MLH1 protein expression using immunohistochemistry (IHC). BRAF V600E mutation was detected by IHC using a specific monoclonal antibody (VE1) and by qPCR. All MLH1 protein-negative cases were subjected to microsatellite instability analysis and MLH1 promoter methylation assay. MLH1 protein expression deficiency and high microsatellite instability (MSI-H) were detected in 18 of the 137 (13.1%) consecutive colorectal cancer specimens. Detection of the BRAF V600E mutation by IHC was 100% sensitive and specific as compared to qPCR, and this mutation was frequently present in the MSI-H group (77.8%; 14/18) and less frequently in the microsatellite-stable group (7.6%; 9/118). All BRAF V600E mutated cases of the MSI-H group presented with a MLH1 promoter methylation (14/14) as detected by methylation-specific multiplex ligation-dependent probe amplification. When BRAF was wild type in the MSI-H group, only one MLH1 promoter methylation was detected (1/4), and of the remaining three cases without MLH1 methylation, two were identified to harbor an MLH1 mutation consistent with Lynch syndrome. Finally, 11 previously confirmed Lynch syndrome cases were analyzed for BRAF V600E mutation, and all of them were wild type. In conclusion, detection of BRAF V600E in colorectal cancer specimens by IHC is sensitive and specific and may help to identify Lynch syndrome patients.


Subject(s)
Colorectal Neoplasms, Hereditary Nonpolyposis/genetics , Colorectal Neoplasms/genetics , Genetic Predisposition to Disease/genetics , Mutation/genetics , Proto-Oncogene Proteins B-raf/genetics , Adult , Aged , Aged, 80 and over , Colorectal Neoplasms/diagnosis , Colorectal Neoplasms/metabolism , Colorectal Neoplasms, Hereditary Nonpolyposis/diagnosis , Colorectal Neoplasms, Hereditary Nonpolyposis/metabolism , Female , Genetic Testing/methods , Humans , Immunohistochemistry/methods , Male , Microsatellite Instability , Middle Aged , Polymerase Chain Reaction/methods , Young Adult
8.
Breast Cancer Res ; 14(3): R90, 2012 Jun 12.
Article in English | MEDLINE | ID: mdl-22691310

ABSTRACT

INTRODUCTION: Breast carcinoma is the most common cancer in women, but its incidence is not increased in Lynch syndrome (LS) and studies on DNA mismatch repair deficiency (MMR) in LS-associated breast cancers have arrived at conflicting results. This study aimed to settle the question as to whether breast carcinoma belongs to the LS tumor spectrum. METHODS: MMR status and epigenetic profiles were determined for all available breast carcinomas identified among 200 LS families from a nation-wide registry (23 tumors from mutation carriers and 18 from non-carriers). Sporadic breast carcinomas (n = 49) and other cancers (n = 105) from MMR gene mutation carriers were studied for comparison. RESULTS: The proportion of breast carcinomas that were MMR-deficient based on absent MMR protein, presence of microsatellite instability, or both was significantly (P = 0.00016) higher among breast carcinomas from mutation carriers (13/20, 65%) compared to non-carriers (0/14, 0%). While the average age at breast carcinoma diagnosis was similar in carriers (56 years) and non-carriers (54 years), it was lower for MMR-deficient versus proficient tumors in mutation carriers (53 years versus 61 years, P = 0.027). Among mutation carriers, absent MMR protein was less frequent in breast carcinoma (65%) than in any of seven other tumor types studied (75% to 100%). Tumor suppressor promoter methylation patterns were organ-specific and similar between breast carcinomas from mutation carriers and non-carriers. CONCLUSIONS: Breast carcinoma from MMR gene mutation carriers resembles common breast carcinoma in many respects (for example, general clinicopathological and epigenetic profiles). MMR status makes a distinction: over half are MMR-deficient typical of LS spectrum tumors, while the remaining subset which is MMR-proficient may develop differently. The results are important for appropriate surveillance in mutation carriers and may be relevant for LS diagnosis in selected cases.


Subject(s)
Breast Neoplasms/genetics , Colorectal Neoplasms, Hereditary Nonpolyposis/genetics , DNA Mismatch Repair/genetics , Adaptor Proteins, Signal Transducing/genetics , Adenosine Triphosphatases/genetics , Breast Neoplasms/complications , Colorectal Neoplasms, Hereditary Nonpolyposis/complications , DNA Repair Enzymes/genetics , DNA-Binding Proteins/genetics , Female , Gene Deletion , Humans , Microsatellite Instability , Mismatch Repair Endonuclease PMS2 , MutL Protein Homolog 1 , MutS Homolog 2 Protein/genetics , Mutation , Nuclear Proteins/genetics
9.
Fam Cancer ; 11(3): 395-401, 2012 Sep.
Article in English | MEDLINE | ID: mdl-22476430

ABSTRACT

Increased risk for urological tumors has been observed in mutation carriers with Lynch syndrome (LS). In this study, we evaluated the clinical features of uroepithelial (bladder and ureter) and kidney cancers in 974 Finnish mutation carriers. Altogether 30 patients had a total of 34 urological tumors: 12 ureter, 12 bladder, and 10 kidney cancers. Urological tumor was the only tumor in 9 (30 %) patients, and metachronous other tumor occurred in 21 (70 %). The occurrence of uroepithelial cancers was significantly higher in MSH2 mutation carriers (6 %; 95 % CI, 2.7-11.0) than in MLH1 carriers (2 %; 95 % CI, 1.1-3.2) and MSH6 mutation carriers (0 %) (p = 0.014). The mean ages of patients at the time of diagnosis were: bladder cancer, 57 years; ureter cancer, 58 years; and kidney cancer, 64 years. Overall 5-year survival rates were 70 % (95 % CI, 0.32-0.89) in bladder cancer, 81 % (95 % CI, 0.45-0.95) in ureter cancer, and 75 % (95 % CI, 0.31-0.93) in kidney cancer. Cancer-specific 5-year survival rates were 70 % (95 % CI, 0.32-0.89) in bladder cancer, 91 % (95 % CI, 0.51-0.98) in ureter cancer, and 100 % in kidney cancer. In conclusion, early age of onset was observed in patients with uroepithelial tumors, but not in patients with kidney cancer. The frequency of uroepithelial tumors was significantly higher in MSH2 mutation carriers than in MLH1 carriers. Further studies with larger numbers of patients, however, are needed to evaluate the potential benefit of surveillance of urological tumors in LS.


Subject(s)
Adaptor Proteins, Signal Transducing/genetics , Colorectal Neoplasms, Hereditary Nonpolyposis/genetics , DNA-Binding Proteins/genetics , Kidney Neoplasms/etiology , MutS Homolog 2 Protein/genetics , Nuclear Proteins/genetics , Ureteral Neoplasms/etiology , Urinary Bladder Neoplasms/etiology , Adult , Age of Onset , Aged , Colorectal Neoplasms, Hereditary Nonpolyposis/complications , Female , Finland , Follow-Up Studies , Heterozygote , Humans , Kidney Neoplasms/genetics , Kidney Neoplasms/mortality , Male , Middle Aged , MutL Protein Homolog 1 , Mutation , Ureteral Neoplasms/genetics , Ureteral Neoplasms/mortality , Urinary Bladder Neoplasms/genetics , Urinary Bladder Neoplasms/mortality
10.
Clin Cancer Res ; 15(18): 5772-83, 2009 Sep 15.
Article in English | MEDLINE | ID: mdl-19723644

ABSTRACT

PURPOSE: Endometrial carcinoma (EC) is common in the population and the most frequent extracolonic malignancy in hereditary nonpolyposis colorectal carcinoma (HNPCC)/Lynch syndrome. We characterized precursor lesions of endometrioid EC to identify markers of malignant transformation and tumor progression. EXPERIMENTAL DESIGN: Serial specimens of normal endometrium, simple hyperplasia, complex hyperplasia without atypia, complex hyperplasia with atypia, and endometrial carcinoma obtained during a 10-year surveillance of DNA mismatch repair (MMR) gene mutation carriers (together 110 samples) were molecularly profiled and compared with a sporadic reference series of endometrial specimens taken for nonmalignant reasons (62 samples). RESULTS: Among MMR gene mutation carriers, decreased MMR protein expression was present in 7% in normal endometrium, 40% in simple hyperplasia, 100% in complex hyperplasia without atypia, 92% in complex hyperplasia with atypia, and 100% in endometrial carcinoma. Microsatellite instability frequencies were lower (6%, 17%, 67%, 38%, and 64%, respectively). Among 24 tumor suppressor genes, the number of methylated loci increased from normal endometrium to simple hyperplasia to complex hyperplasia (complex hyperplasia without atypia/complex hyperplasia with atypia) in both Lynch syndrome and reference series. The most frequently methylated genes were CDH13, RASSF1A, and GSTP1. In MMR gene mutation carriers, MMR and methylation defects appeared up to 12 years before endometrial carcinoma. CONCLUSIONS: Molecular changes in endometrial tissue are detectable several years before endometrial carcinoma in genetically predisposed individuals. Abnormal MMR and methylation classify normal endometrium and simple hyperplasia into one category and complex hyperplasia without atypia, complex hyperplasia with atypia, and endometrial carcinoma into another, suggesting that, contrary to a traditional view, complex hyperplasia without atypia and complex hyperplasia with atypia are equally important as precursor lesions of endometrial carcinoma.


Subject(s)
Endometrial Neoplasms/genetics , Endometrial Neoplasms/pathology , Oligonucleotide Array Sequence Analysis , Adult , Aged , Biomarkers, Tumor/analysis , Biomarkers, Tumor/genetics , DNA Mismatch Repair/genetics , Disease Progression , Endometrial Neoplasms/metabolism , Female , Humans , Hyperplasia , Methylation , Middle Aged
11.
Int J Cancer ; 124(10): 2333-40, 2009 May 15.
Article in English | MEDLINE | ID: mdl-19173287

ABSTRACT

In one-third of families fulfilling the Amsterdam criteria for hereditary nonpolyposis colorectal cancer/Lynch syndrome, and a majority of those not fulfilling these criteria point mutations in DNA mismatch repair (MMR) genes are not found. The role of large genomic rearrangements and germline epimutations in MLH1, MSH2 and MSH6 was evaluated in 2 such cohorts. All 45 index patients were mutation-negative by genomic sequencing and testing for a prevalent population-specific founder mutation, and selectively lacked MMR protein expression in tumor tissue. Eleven patients ("research cohort") represented 11 mutation-negative families among 81 verified or putative Lynch syndrome families from the nation-wide Hereditary Colorectal Cancer Registry of Finland. Thirty-four patients from 33 families ("clinic-based cohort") represented suspected Lynch syndrome patients tested for MMR gene mutations in a diagnostic laboratory during 2004-2007. Multiplex ligation-dependent probe amplification (MLPA) and methylation-specific (MS)-MLPA were used to detect rearrangements and epimutations, respectively. Large genomic deletions occurred in 12/45 patients (27%), being present in 3/25 (12%), 9/16 (56%) and 0/4 (0%) among index patients lacking MLH1, MSH2 or MSH6 expression, respectively. Germline epimutations of MLH1, one of which coexisted with a genomic deletion, occurred in 2 patients (4%) and were accompanied by monoallelic expression in mRNA. Large genomic deletions (mainly MSH2) and germline epimutations (MLH1) together explain a significant fraction of point mutation-negative families suspected of Lynch syndrome and are associated with characteristic clinical and family features. Our findings have important implications in the diagnosis and management of such families.


Subject(s)
Colorectal Neoplasms, Hereditary Nonpolyposis/genetics , Gene Rearrangement , Germ-Line Mutation , Adult , Aged , Base Sequence , Cohort Studies , DNA Methylation , DNA Primers , DNA Repair/genetics , Humans , Immunohistochemistry , Middle Aged
12.
Int J Cancer ; 121(4): 915-20, 2007 Aug 15.
Article in English | MEDLINE | ID: mdl-17471559

ABSTRACT

While the phosphatidylinositol 3-kinase (PI3K)/AKT signaling pathway is known to be activated in multiple sporadic cancers, the role of this pathway in familial tumors is mostly unknown. We searched for alterations in the catalytic domain of PI3K (PIK3CA), PTEN and KRAS, all of which may contribute to PI3K/AKT pathway activation, in a total of 160-familial colorectal (CRC) and endometrial carcinomas (EC), stratified by the presence vs. absence of germline mutations in DNA mismatch repair (MMR) genes. PIK3CA alterations (consisting of point mutations or low-level amplification, which were mutually exclusive with 1 exception) occurred in 10/70 (14%) of CRCs and 19/90 (21%) of ECs. Within ECs, amplification was significantly associated with the subgroup lacking germline mutations in MMR genes (familial site-specific endometrial cancer) (p = 0.015). Decreased or lost PTEN expression was characteristic of endometrial tumourigenesis (51/81, 63%, in EC compared with 24/62, 39%, in CRC, p = 0.004) and KRAS mutations of colorectal tumourigenesis (19/70, 27% in CRC vs. 9/89, 10%, in EC, p = 0.006) regardless of the MMR gene mutation status. PIK3CA alterations frequently coexisted with PTEN or KRAS changes. Combined with published studies on sporadic tumors, our data broaden the understanding of the role for PI3K pathway genes in human tumorigenesis.


Subject(s)
Colorectal Neoplasms/genetics , Endometrial Neoplasms/genetics , Gene Amplification , Mutation , Phosphatidylinositol 3-Kinases/genetics , Aged , Class I Phosphatidylinositol 3-Kinases , Female , Humans , Membrane Proteins/genetics , Middle Aged , PTEN Phosphohydrolase/genetics , Polymorphism, Single-Stranded Conformational , Proto-Oncogene Proteins/genetics , Proto-Oncogene Proteins p21(ras) , Reverse Transcriptase Polymerase Chain Reaction , ras Proteins/genetics
13.
Blood ; 109(8): 3513-20, 2007 Apr 15.
Article in English | MEDLINE | ID: mdl-17170130

ABSTRACT

Crystallographic and electron microscopy studies revealed genuflexed (bent) integrins in both unliganded (inactive) and physiologic ligandbound (active) states, suggesting that local conformational changes are sufficient for activation. Herein we have explored the role of local changes in the contact region between the membrane-proximal beta-tail domain (betaTD) and the ligand-binding betaA domain of the bent conformation in regulating interaction of integrin CD11b/CD18 (alphaMbeta2) with its physiologic ligand iC3b. We replaced the betaTD CD loop residues D658GMD of the CD18 (beta2) subunit with the equivalent D672SSG of the beta3 subunit, with AGAA or with NGTD, expressed the respective heterodimeric receptors either transiently in epithelial HEK293T cells or stably in leukocytes (K562), and measured their ability to bind iC3b and to conformation-sensitive mAbs. In the presence of the physiologic divalent cations Ca(2+) plus Mg(2+) (at 1 mM each), the modified integrins showed increased (in HEK293) or constitutive (in K562) binding to iC3b compared with wild-type receptors. K562 expressing the betaTD-modified integrins bound in Ca(2+)Mg(2+) to the betaA-directed high-affinity reporter mAb 24 but not to mAb KIM127, a reporter of the genu-straightened state. These data identify a role for the membrane proximal betaTD as an allosteric modulator of integrin activation.


Subject(s)
CD11b Antigen/chemistry , CD18 Antigens/chemistry , Complement C3b/chemistry , Models, Molecular , Amino Acid Substitution , Animals , CD11b Antigen/genetics , CD11b Antigen/metabolism , CD18 Antigens/genetics , CD18 Antigens/metabolism , Calcium/chemistry , Calcium/metabolism , Complement C3b/genetics , Complement C3b/metabolism , Humans , K562 Cells , Ligands , Magnesium/chemistry , Magnesium/metabolism , Mutagenesis, Site-Directed , Protein Binding , Protein Structure, Quaternary , Protein Structure, Secondary , Protein Structure, Tertiary , Structure-Activity Relationship
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