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PubMedDate not supplied

Most kappa immunoglobulin mRNA in human lymphocytes is homologous to a small family of germ-line V genes.

The mammalian immune system produces 10(6)-10(8) different antibody-combining sites. It has been established that three factors contribute to the diversity of immunoglobulin variable regions: multiple gene segments in the germ line, somatic recombination of these segments and somatic mutation. However, the relative importance of these components in generating the antibody repertoire is unknown. One way to assess the importance of the germ-line component relative to the somatic components would be to determine the number of germ-line V genes expressed. Here, I report that a family of about 25 human germ-line V genes encodes over 50% of kappa mRNA in spleen or peripheral blood lymphocytes. This observation agrees with gene-counting experiments which indicated that the total number of V kappa genes in the human genome is quite small, about 50 or less. Such a small number of germ-line V kappa sequences implies that somatic mutation is the major source of human kappa-chain diversity.

Antibody Diversity↗
PubMed1990

Cloning and sequence analysis of the VH and VL regions of an anti-myelin/DNA antibody from a patient with peripheral neuropathy and chronic lymphocytic leukemia.

We have cloned and determined the nucleotide sequence of the Ig VH and VL region genes of an IgM kappa mAb that binds to denatured DNA and myelin from a patient (POP) with chronic lymphocytic leukemia and peripheral neuropathy. Sequence analysis indicates that the V region of the kappa L chain gene (PopVK) has 99% homology to a V kappa IIIa germ-line gene and the V region of the mu H chain gene (PopVH) has 96% homology to the VH26 germ-line gene that is a member of the VH3 gene family. It is likely the V kappa and VH genes arose from these respective germ-line genes via somatic mutation or from closely related genes. V kappa III genes have frequently been used by other IgMk mAb especially those with rheumatoid factor activity, and the VH26 gene with no somatic mutation has been used by several anti-DNA antibodies, suggesting the possibility of preferential association of these or related germ-line genes with autoantibodies. The minor differences between the sequences of POP's VH and V kappa genes and sequences used by other autoantibodies, may be responsible for this antibody's crossreactivity with myelin and, as a result, the autoimmune neuropathy.

Amino Acid Sequence↗
PubMed1994

Variable regions of Ig heavy chain genes encoding antithyrotropin receptor antibodies of patients with Graves' disease.

We have established EBV-transformed human B cell clones producing monoclonal antithyrotropin receptor antibodies from two patients with Graves' disease. We then isolated and characterized Ig H chain genes of 5 B cell clones with the thyrotropin-binding inhibitor Ig (TBII) activity and 4 B cell clones with the thyroid-stimulating antibody (TSAb) activity. We found that VH gene families used in the 5 TBII clones were all VH-III, although those of the four TSAb clones were diverse, including VH-II, -III, -IV, all -V. Most of VH segments used in TBII and TSAb are commonly used in other autoantibodies and fetal liver repertoire. The frequency of somatic mutations in TBII was higher than that in TSAb. Inasmuch as the same germline VH segment (V3-23) was used for both TBII and TSAb, the frequency and position of somatic mutations may be important for generation of TBII and TSAb.

Amino Acid Sequence↗
PubMed2006

BH3 domain mutation of proapoptotic genes Bad, Bmf and Bcl-G is rare in transitional cell carcinomas of the urinary bladder.

AIMS: Mounting evidence indicates that deregulation of apoptosis contributes to the development of human cancers. Bcl-2 family proteins regulate the intrinsic apoptosis pathway. The aim of this study was to explore the possibility that mutation of BH3 domain of proapoptotic Bcl-2 genes Bad, Bmf and Bcl-G might be involved in the development of urinary bladder cancer. METHODS: We analysed the BH3 domains of Bad, Bmf and Bcl-G genes for the detection of somatic mutations in 43 transitional cell carcinomas (TCCs) of the urinary bladder by a single strand conformation polymorphism assay in this study. RESULTS: There was no somatic mutation of BH3 domains of Bad, Bmf and Bcl-G genes in the TCC samples. CONCLUSION: The data presented here indicate that BH3 domain mutation of these genes is rare in TCCs and may not contribute to the pathogenesis of TCCs.

Adaptor Proteins, Signal Transducing↗
PubMed1973

A general theory of carcinogenesis.

A GENERAL HYPOTHESIS OF CARCINOGENESIS IS PROPOSED CONSISTING OF THE FOLLOWING FEATURES: (1) It is suggested that all cells possess multiple structural genes (Tr) capable of coding for transforming factors which can release the cell from its normal constraints on growth. (2) In adult cells they are suppressed by diploid pairs of regulatory genes and some of the transforming genes are tissue specific. (3) The Tr loci are temporarily activated at some stage of embryogenesis and possibly during some stage of the cell cycle in adult cells. (4) Spontaneous tumors, or tumors induced by chemicals or radiation, arise as the result of a double mutation of any set of regulatory genes releasing the suppression of the corresponding Tr genes and leading to transformation of the cell. (5) Autosomal dominant hereditary tumors, such as retinoblastoma, are the result of germ-line inheritance of one inactive regulatory gene. Subsequent somatic mutation of the other regulatory gene leads to tumor formation. (6) The Philadelphia chromosome produces inactivation of one regulatory gene by position effect. A somatic mutation of the other leads to chronic myelogenous leukemia. (7) Oncogenic viruses evolved by the extraction of host Tr genes with their conversion to viral transforming genes. As a result, in addition to the above mechanisms, tumors may also be produced by the reintroduction of these genes into susceptible host cells.

Animals↗
PubMed1998

Ataxia-telangiectasia and T-cell leukemias: no evidence for somatic ATM mutation in sporadic T-ALL or for hypermethylation of the ATM-NPAT/E14 bidirectional promoter in T-PLL.

The ATM gene deficient in ataxia-telangiectasia, a recessive multisystem disease associated with a high risk of lymphomas and leukemias, was found previously to be inactivated in a rare sporadic malignancy, T-cell prolymphocytic leukemia (T-PLL), which is often associated with cytogenetic aberrations of chromosome 14. The ATM gene was shown to sustain frequent loss-of-function mutations in T-PLL tumor cells, consistent with functioning as a tumor suppressor gene in this leukemia. To investigate the possibility of nonmutational or nonrecombinational mechanisms of T-PLL development, we have used bisulfite genomic sequencing to analyze DNA methylation in the putative bidirectional promoter region of the closely linked ATM and NPAT/E14 genes within the CpG island at 11q22-q23. We show that this region is completely demethylated in lymphocytes expressing ATM; however, no extensive hypermethylation was found in 9 T-PLL tumor DNA samples without evidence of ATM/p53 mutations. Because acute T-cell lymphoblastic leukemias (T-ALL) were also observed in ataxia-telangiectasia patients and T-ALL tumor cells contain chromosome 14 abnormalities, 19 presentation samples of T-ALL patients were analyzed for ATM mutations. Although T-ALL patients exhibited rare nucleotide substitutions not previously found in ATM, all were identified in the germ-line, indicating constitutional polymorphisms, potentially confined to ethnic subpopulations. The absence of somatic nucleotide changes in ATM in T-ALL as compared with T-PLL suggests a distinct pattern of genetic events in the development of the two leukemias.

Ataxia Telangiectasia↗
PubMed2001

Antisense inhibition of BRCA1 expression and molecular analysis of hereditary tumors indicate that functional inactivation of the p53 DNA damage response pathway is required for BRCA-associated tumorigenesis.

OBJECTIVE: The purpose of this investigation was to test the hypothesis that mutation of TP53 is a requirement for BRCA-associated cancer development. METHODS: A cell line experimentally deficient in BRCA1 protein was constructed using a regulatable antisense expression vector expressing 4000 bp from the BRCA1 cDNA. Changes in BRCA1, p53, and p21 protein levels were assayed by immunoblotting. Ovarian tumors with germline mutations in BRCA1 or BRCA2 were screened for mutations in TP53 by single-strand conformation polymorphism analysis. RESULTS: Antisense inhibition of BRCA1 protein caused p53 and p21 protein levels to rise, indicating that partial loss of BRCA1 function activates the p53 DNA damage response pathway. Somatic mutation of TP53 was observed in 7 of 14 BRCA-associated ovarian tumors. CONCLUSIONS: Our findings provide novel evidence that loss of BRCA1 function in human cells activates the p53 DNA damage response pathway and that loss of this pathway, by somatic mutation of TP53, is a likely requirement for BRCA-associated tumor development.

BRCA1 Protein↗
PubMed2001

Nucleotide sequence analysis of a human monoclonal antibody TONO-1 with cytotoxic potential for T-leukemia/lymphoma cells.

A human monoclonal antibody (HuMab) TONO-1 (IgM, lambda) recognizes cell surface antigens associated primarily with human T-leukemia/lymphoma cells. In this study, we investigated the reactivity against T-leukemia/lymphoma cells in detail, cytotoxic potential and primary nucleotide and deduced amino acid sequences of the rearranged heavy and light chains of the HuMab TONO-1. Expression of the molecules (TONO-1 Ags) detected by a HuMab TONO-1 was significantly heterogeneous even in the same T-leukemia/lymphoma cell lines HPB-MLT and MOLT-4F. The flow cytometric curves showed an unusual broad-based spread of fluorescence intensity. HuMab TONO-1 was shown to have the ability to kill the T-leukernia/lymphoma cells efficiently in the presence of rabbit complements. However, HuMab TONO-1 did not demonstrate significant antibody-dependent cellular cytotoxic activity. Furthermore, HuMab TONO-1 heavy and light chain variable regions were cloned, sequenced and analyzed. HuMab TONO-1 uses a V(H) gene member of the V(H)IV gene family V(H)71-4, and is productively rearranged with the germ line D(H) gene D(XP')1, and the germ line J(H)5 gene with multiple somatic mutations. HuMab TONO-1 Vlambda belongs to the lambda light chain variable subgroup I family and is derived from the Vlambdalc germ line gene Humlv1042, and germ line gene Jlambda1 without somatic mutations. The results reveal that the production of HuMab TONO-1, with cytotoxic potential for human T-leukemia/lymphoma cells, is achieved by rearrangement of the V(H)71-4/Humlv1042 germ line variable region gene combination, that is associated with the autoimmune repertoire.

Amino Acid Sequence↗
PubMed1987

Contributions of immunoglobulin heavy and light chains to antibody specificity for lysozyme and two haptens.

Chain recombination experiments with a set of structurally and/or functionally related antibodies were performed to assess the role of the heavy (H) and light (L) chains in determining antigen specificity. The results demonstrated that specificity for hen egg white lysozyme vs two haptens (dinitrophenyl or galactan) is H chain determined and for one set of proteins could be attributed specifically to the H3 region. In contrast to hapten vs lysozyme specificity, when reassociated molecules derived from structurally unrelated antibodies that bound nonoverlapping epitopes on lysozyme were tested, localization of binding to a particular epitope on lysozyme could be predominated by either H or L chains. Furthermore, in some cases, unique specificities distinct from those of either parental antibody were formed. Replacement of the native L chain with an isotypically homologous L chain was more likely to restore high affinity protein binding than was replacement of a less related L chain. When isotypically homologous L chains were compared in association with the same H chain, fine specificity profiles were sensitive to substitutions in as few as two residues that could be attributed to somatic mutation. These results demonstrate that both affinity and specificity derive from very subtle interactions between H and L chains and provide examples of how VH assembly, VL-VH pairing, and somatic mutation could contribute to development and maturation of the specificity repertoire.

Animals↗
PubMed1997

[V gene repertoire and pathogenic autoantibodies].

The studies for autoantibody-associated V genes have failed to find any V gene which might be specific for pathogenic autoantibodies in humans; Namely, both normal subjects and patients have immunoglobulin V genes which can encode autoantibodies. Also single V gene can encode antibodies for both foreign antigens and autoantigens. However, some germline V genes such as V3-7 and VH4-21 are preferentially used for autoantibodies and may be regarded as prototype V genes for autoantibodies. Although somatic mutation in V genes is characteristic in IgG autoantibodies, 0-81 idiotype-positive IgM antibodies, which may be precursor B cells for pathogenic anti-DNA antibody also included many somatic mutations in VH genes, indicating an intrinsic abnormality in B cell development in SLE. Some studies also indicated an abnormal V gene repertoire in autoimmune states. These results may be attributed to dysregulation of autoantibody-associated B cell development.

Animals↗
PubMed2022

Chemical acylation of an acquired serine suppresses oncogenic signaling of K-Ras(G12S).

Drugs that directly impede the function of driver oncogenes offer exceptional efficacy and a therapeutic window. The recently approved mutant selective small-molecule cysteine-reactive covalent inhibitor of the G12C mutant of K-Ras, sotorasib, provides a case in point. KRAS is the most frequently mutated proto-oncogene in human cancer, yet despite success targeting the G12C allele, targeted therapy for other hotspot mutants of KRAS has not been described. Here we report the discovery of small molecules that covalently target a G12S somatic mutation in K-Ras and suppress its oncogenic signaling. We show that these molecules are active in cells expressing K-Ras(G12S) but spare the wild-type protein. Our results provide a path to targeting a second somatic mutation in the oncogene KRAS by overcoming the weak nucleophilicity of an acquired serine residue. The chemistry we describe may serve as a basis for the selective targeting of other unactivated serines.

Humans↗
PubMed2005

Lack of mutations in the TSHr and Gsalpha genes in TSHr antibody negative Graves' disease.

The aim of this study was to investigate whether TSHr antibody negative Graves' disease is associated with somatic mutations in the TSHr or Gsalpha genes and whether histopathologically defined thyroid lesions, i.e., hyperfunctioning adenoma, non-functioning follicular adenomas, or nodules in toxic and non-toxic multinodular goiters are associated with such mutations. No mutations but three germ-line polymorphisms were found in patients with TSHr antibody negative Graves' disease. The three polymorphisms are expected to have no or only minor effects on the signaling properties, and is not associated with altered antigenecity imposed by such mutations. Two heterozygous somatic TSHr mutations were found in two hyperfunctioning adenomas and in two toxic multinodular goiters. The lack of TSHr and Gsalpha mutations in TSHr antibody negative Graves' disease patients indicates that such mutations are neither primary nor secondary events in this disease. The results also confirm that somatic gain-of-function TSHr mutations are present in hyperfunctioning follicular adenomas and goiters, but not in non-functioning thyroid lesions.

Adenoma↗
PubMed1999

Analysis of heavy and light chain pairings indicates that receptor editing shapes the human antibody repertoire.

In the bone marrow, diversity in the primary antibody repertoire is created by the combinatorial rearrangement of different gene segments and by the association of different heavy and light chains. During the secondary response in the germinal centres, antibodies are diversified by somatic mutation and possibly by further rearrangements, or "receptor editing". Here, we have analysed the pairings of heavy and light chain variable domains (VH and VL) in 365 human IgG+ B cells from peripheral blood, and established that these pairings are largely random. The repertoire is dominated by a limited number of pairings of segments and folds. Among these pairings we identified two identical mutated heavy chains in combination with two different mutated light chains (one kappa and one lambda). This shows that receptor editing occurs in the human periphery and that the same antibody lineage can be subjected to both receptor editing and somatic hypermutation. This suggests that receptor editing may be used together with somatic mutation for the affinity maturation of antibodies. We also propose that receptor editing has shaped variable gene segment use and the evolution of V gene families.

Amino Acid Sequence↗
PubMed2026

Genomic, transcriptomic, and molecular predictors of response to neoadjuvant therapy in locally advanced rectal cancer: a narrative review.

Total neoadjuvant therapy (TNT) has emerged as a key treatment paradigm for locally advanced rectal cancer, reducing distant metastasis rates and facilitating organ preservation in selected patients. However, treatment response remains heterogeneous, highlighting the need for biomarkers that can guide treatment selection and optimise outcomes. This narrative review synthesises the current evidence regarding tumour-intrinsic genomic biomarkers associated with response to neoadjuvant therapy, encompassing somatic mutations, germline polymorphisms, gene expression profiles, mismatch repair (MMR) status, protein expression, epigenetic markers, and circulating tumour-derived biomarkers across conventional chemoradiotherapy (CRT) and TNT paradigms. Across the reviewed literature, individual somatic mutations, including KRAS, TP53, and BRAF, demonstrated limited reproducibility as predictive biomarkers, although KRAS mutations were recurrently associated with lower pathological complete response (pCR) rates in CRT-era cohorts. Germline polymorphisms in DNA repair (XRCC1) and folate metabolism (MTHFR) genes showed inconsistent associations with treatment response. In contrast, transcriptomic biomarkers demonstrated greater biological coherence, with proliferative, epithelial-mesenchymal transition, and metabolic signatures frequently associated with treatment resistance, while multi-gene classifiers generally outperformed single-gene markers. Among currently available tumour-intrinsic biomarkers, MMR deficiency was the most consistently reported biomarker associated with reduced response to fluoropyrimidine-based regimens, including TNT, although TNT-specific evidence remains comparatively limited. Dynamic circulating tumour DNA (ctDNA) monitoring, particularly ctDNA clearance during or after therapy, was consistently associated with pathological response and long-term oncologic outcomes across reviewed studies, whereas baseline ctDNA levels showed limited predictive value. Overall, the reviewed literature suggests that biomarker research in rectal cancer has evolved from single-gene analyses towards pathway-level and dynamic biomarkers. The integration of transcriptomic signatures, MMR status, and dynamic ctDNA monitoring may represent a promising strategy for personalising neoadjuvant therapy, improving patient selection for organ-preserving approaches, and enhancing oncologic outcomes in locally advanced rectal cancer. Nevertheless, the evidence base remains heterogeneous, and further prospective validation, assay standardisation, and evaluation within contemporary TNT cohorts are required before these biomarkers can be routinely incorporated into clinical decision-making.

Humans↗
PubMed1997

Analysis of V(H) genes rearranged by individual B cells in dermal infiltrates of patients with mycosis fungoides.

In patients with cutaneous T cell lymphomas such as mycosis fungoides B cells can frequently be detected in the lymphocytic dermal infiltrate. To analyse their immunoglobulin heavy chain gene repertoire, single B cells were obtained from tissue sections of two typical patients with mycosis fungoides using hydraulic micromanipulation followed by specific amplification of the respective gene segments by single-cell polymerase chain reaction (PCR) technique. A total of 21 V(H)DJ(H) genes was sequenced. From each individual B cell a single productive V(H)DJ(H) rearrangement was obtained. There was no clonal relationship detected between any of these rearrangements suggesting polyclonality of the infiltrating B cells. The representation of V(H) families was in accordance with the germ-line complexity. A remarkably high number of V(H) genes (5/13 in patient 1; 3/8 in patient 2) was completely or nearly germ-line-identical. Five of seven V(H)4 family genes were nearly unmutated. On the other hand, most of the V(H)3 gene family members were somatically mutated in an antigen-driven manner. The proportion of germ-line-identical V(H) genes, the usage of individual V(H), D, J(H) gene elements, and the pattern of somatic mutations found in the B cells infiltrating skin lesions of patients with mycosis fungoides resembles the peripheral blood repertoire, suggesting a bystander role of these cells.

Amino Acid Sequence↗
PubMed1999

Analysis of the MEN1 gene in sporadic pituitary adenomas from Japanese patients.

An autosomal-dominant syndrome known as multiple endocrine neoplasia type 1 (MEN1) is characterized by tumors in parathyroid glands, pancreatic endocrine tissues and the anterior pituitary gland. The predisposing gene was identified at 11q13 when germline mutations in the MEN1 gene were detected in affected pedigrees. To investigate a possible role of this gene in tumorigenesis of non-familial pituitary adenomas, we examined 24 sporadic tumors from Japanese patients for loss of heterozygosity (LOH) at the 11q13 region and for somatic mutations in the entire coding region and exon-intron boundaries of MEN1. Although three common sequence variants were detected, none of the tumors exhibited either LOH or somatic mutations of this gene. Our results indicate that inherited and sporadic forms of pituitary adenomas are different in terms of the genetic events that contribute to their development, and that other loci associated with pituitary neoplasia must still be sought.

Adenoma↗
PubMed1996

MMTV-induced mutations in mouse mammary tumors: their potential relevance to human breast cancer.

In mouse mammary tumor virus (MMTV) infected mice, three identifiable stages of mammary tumorigenesis can be biologically defined: preneoplastic hyperplastic nodules, malignant tumor, and distant metastatic lesions (primarily in the lung). MMTV is a biological carcinogen which induces somatic mutations as consequence of its integration into the host cellular genome. Each stage of mammary tumorigenesis appears to result from the clonal outgrowth of cells containing additional integrated proviral MMTV genomes. This phenomenon has provided the basis for an approach to identify genes which, when affected, may contribute to progression through the different stages of mammary tumorigenesis. Eight different genes (Wnt1, Wnt3, Wnt10b, Fgf3, Fgf4, Fgf8, Int3, and Int6) have been shown to be genetically altered in multiple mammary tumors as a consequence of MMTV integration. Although the significance of the human homologs of these genes as targets for somatic mutation during human breast carcinogenesis is only now being explored, it is clear that this work has led to a new appreciation of the complexity of the genetic circuitry that is involved in the control of normal mammary gland growth and development. It seems likely that some of the mutations induced by MMTV, and the signaling pathways in which these target genes take part, will be relevant to the progression from preneoplastic lesions to distant metastasis in human breast cancer.

Animals↗
PubMed2006

Hereditary hyper-ACE-emia due to the Pro1199Leu mutation of somatic ACE as a potential pitfall in diagnosis: a first family outside Europe.

Elevated plasma levels of angiotensin converting enzyme (ACE) are associated with granulomatous diseases. However, several families of autosomal dominant hyper-ACE-emia without disease association have already been reported. Recently, the ACE mutation c.3705C>T (Pro1199Leu) was identified as the genetic correlate in European cases of asymptomatic autosomal dominant hyper-ACE-emia. Here, we describe a first family outside Europe with asymptomatic autosomal-dominant hyper-ACE-emia due to the ACE Pro1199Leu mutation. Benign autosomal-dominant hyper-ACE-emia should be considered for differential diagnosis of elevated ACE levels worldwide.

Cytosine↗