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PubMed2002

Increased sensitivity of p53-deficient cells to anticancer agents due to loss of Pms2.

A large fraction of human tumours carries mutations in the p53 gene. p53 plays a central role in controlling cell cycle checkpoint regulation, DNA repair, transcription, and apoptosis upon genotoxic stress. Lack of p53 function impairs these cellular processes, and this may be the basis of resistance to chemotherapeutic regimens. By virtue of the involvement of DNA mismatch repair in modulating cytotoxic pathways in response to DNA damaging agents, we investigated the effects of loss of Pms2 on the sensitivity to a panel of widely used anticancer agents in E1A/Ha-Ras-transformed p53-null mouse fibroblasts either proficient or deficient in Pms2. We report that lack of the Pms2 gene is associated with an increased sensitivity, ranging from 2-6-fold, to some types of anticancer agents including the topoisomerase II poisons doxorubicin, etoposide and mitoxantrone, the platinum compounds cisplatin and oxaliplatin, the taxanes docetaxel and paclitaxel, and the antimetabolite gemcitabine. In contrast, no change in sensitivity was found after treatment with 5-fluorouracil. Cell cycle analysis revealed that both, Pms2-deficient and -proficient cells, retain the ability to arrest at the G2/M upon cisplatin treatment. The data indicate that the concomitant loss of Pms2 function chemosensitises p53-deficient cells to some types of anticancer agents, that Pms2 positively modulates cell survival by mechanisms independent of p53, and that increased cytotoxicity is paralleled by increased apoptosis. Tumour-targeted functional inhibition of Pms2 may be a valuable strategy for increasing the efficacy of anticancer agents in the treatment of p53-mutant cancers.

Adenosine Triphosphatases↗
PubMed2006

Reduced Pms2 expression in non-neoplastic flat mucosa from patients with colon cancer correlates with reduced apoptosis competence.

Pms2 protein is a component of the DNA mismatch repair complex responsible both for post-replication correction of DNA nucleotide mispairs and for early steps in apoptosis. Germline mutations in DNA mismatch repair genes give rise to hereditary non-polyposis colon cancer, which accounts for about 4% of colon cancers. However, little is known about the expression of mismatch repair proteins in relation to sporadic colon cancer, which accounts for the great majority of colon cancers. Multiple samples were taken from the non-neoplastic flat mucosa of colon resections from patients with no colonic neoplasia, a tubulovillous adenoma, or an adenocarcinoma. Expression of Pms2 was assessed using semiquantitative immunohistochemistry. Apoptosis was assessed in polychrome-stained epoxy sections using morphologic criteria. Samples from patients without colonic neoplasia had moderate to strong staining for Pms2 in cell nuclei at the base of crypts, while samples from 2 of the 3 colons with a tubulovillous adenoma, and from 6 of the 10 colons with adenocarcinomas, showed reduced Pms2 expression. Samples from patients with an adenocarcinoma that had reduced Pms2 expression also exhibited reduced apoptosis capability in nearby tissue samples, evidenced when this paired tissue was stressed ex vivo with bile acid. Reduced Pms2 expression in the colonic mucosa may be an early step in progression to colon cancer. This reduction may cause decreased mismatch repair, increased genetic instability, and/or reduced apoptotic capability. Immunohistochemical determination of reduced Pms2 expression, upon further testing, may prove to be a promising early biomarker of risk of progression to malignancy.

Adenosine Triphosphatases↗
PubMed2000

Mutagenesis in PMS2- and MSH2-deficient mice indicates differential protection from transversions and frameshifts.

DNA mismatch repair (MMR) deficiency leads to an increased mutation frequency and a predisposition to neoplasia. 'Knockout' mice deficient in the MMR proteins Msh2 and Pms2 crossed with mutation detection reporter (supF, lacI and cII) transgenic mice have been used to facilitate a comparison of the changes in mutation frequency and spectra. We find that the mutation frequency was consistently higher in Msh2-deficient mice than Pms2-deficient mice. The lacI target gene, which is highly sensitive to point mutations, demonstrated that both Msh2- and Pms2-deficient mice accumulate transition mutations as the predominant mutation. However, when compared with Msh2(-/-) mice, lacI and cII mutants from Pms2-deficient mice revealed an increased proportion of +/-1 bp frameshift mutations and a corresponding decrease in transversion mutations. The supF target gene, which is sensitive to frameshift mutations, and the cII target gene revealed a strong tendency for -1 bp deletions over +1 bp insertions in Msh2(-/-) compared with Pms2(-/-) mice. These data indicate that Msh2 and Pms2 deficiency have subtle but differing effects on mutation avoidance which may contribute to the differences in tumor spectra observed in the two 'knockout' mouse models. These variances in mutation accumulation may also play a role, in part, in the differences seen in prevalence of MSH2 and PMS2 germline mutations in hereditary non-polyposis colorectal cancer patients.

Adenosine Triphosphatases↗
PubMed2002

Polymorphisms and HNPCC: PMS2-MLH1 protein interactions diminished by single nucleotide polymorphisms.

Hereditary nonpolyposis colorectal cancer (HNPCC) is one of the most common autosomal dominant inherited diseases. Mutations in the human mismatch repair (MMR) proteins MLH1, MSH2, MSH6, PMS1, and PMS2 have been found to co-segregate with HNPCC. The MLH1 and MSH2 proteins have been demonstrated to interact with PMS1, PMS2, and MSH6 proteins. A previous study reported that missense mutations in specific regions of MLH1 can lead to defects in protein-protein interactions with PMS2. Here we report that three missense alterations previously identified as single nucleotide polymorphisms (SNPs) in PMS2 (P511K, T597S, and M622I) cause defective protein-protein interactions with MLH1, even though the alterations are not in the previously reported interaction domain. These results suggest that an additional domain in PMS2 affects MLH1-PMS2 interaction. This study also demonstrates that SNPs can result in gene alterations that indeed have a functional effect on protein phenotype. Thus, these three SNPs may ultimately represent variants with an increased risk factor for tumorgenesis in HNPCC. This study is one of the first to use a functional assay to appraise the role of SNPs and suggests that traditional definitions of polymorphisms and mutations are in need of reconsideration.

Adaptor Proteins, Signal Transducing↗
PubMed1995

Analysis of the 5' region of PMS2 reveals heterogeneous transcripts and a novel overlapping gene.

The PMS2 gene encodes a protein that is involved in DNA mismatch repair and is mutated in a subset of patients with hereditary nonpolyposis colon cancer (HNPCC). The previously published PMS2 cDNA sequence lacks an upstream in-frame stop codon preceding the presumptive initiating methionine. To evaluate the 5' terminus of the PMS2 coding region further, we isolated additional cDNA clones, RT-PCR products, and the corresponding 5' genomic segment of the PMS2 locus. The PMS2 gene transcripts were found to have heterogeneous but colinear 5' termini, one of which contained an in-frame termination codon preceding the initiating methionine. In addition, a novel gene encoding a 34.5-kDa polypeptide was found to initiate transcriptionally within PMS2 from the opposite strand.

Adenosine Triphosphatases↗
PubMed1999

Mutational analysis of the PMS2 gene in sporadic endometrial cancers with microsatellite instability.

OBJECTIVE: Approximately 20% of endometrial tumors have a defect in DNA mismatch repair and exhibit microsatellite instability (MSI). We assessed the role of the PMS2 DNA mismatch repair gene in MSI-positive sporadic endometrial tumors. METHODS: We examined 40 sporadic endometrial tumor specimens with MSI. All 15 exons of the PMS2 gene were investigated for sequence alterations by single-strand conformational variant analysis. RESULTS: Twelve polymorphisms were identified, 8 of which were in the coding sequence. Four specimens revealed mutations in intronic sequences that are not predicted to affect the PMS2 mRNA. No mutations were detected within the coding region of the PMS2 gene. CONCLUSION: We conclude that structural mutations in the PMS2 gene are not responsible for defective DNA mismatch repair in sporadic endometrial cancers with MSI. The identification of single nucleotide polymorphisms in the PMS2 locus may aid in the mapping and characterization of genetic diseases.

Adenosine Triphosphatases↗
PubMed2003

Apoptosis and mutation in the murine small intestine: loss of Mlh1- and Pms2-dependent apoptosis leads to increased mutation in vivo.

The mismatch repair (MMR) protein Msh2 has been shown to function in the apoptotic response to alkylating agents in vivo. Here, we extend these studies to the MutL homologues (MLH) Mlh1 and Pms2 by analysing the apoptotic response within the small intestine of gene targeted strains. We demonstrate significant differences between Msh2, Mlh1 and Pms2 mutations in influencing apoptotic signalling following 50mg/kg N-methyl-nitrosourea (NMNU), with no obvious reliance upon either Mlh1 or Pms2. However, following exposure to 100mg/kg temozolomide or lower levels of NMNU (10mg/kg) both Mlh1- and Pms2-dependent apoptosis was observed, indicating that the apoptotic response at these levels of DNA damage is dependent on the MutL homologues. Given our ability to observe a MutLalpha dependence of the apoptotic response, we tested whether perturbations of this response directly translate into increases in mutation frequency in vivo. We show that treatment with temozolomide or 10mg/kg NMNU significantly increases mutation in both the Mlh1 and Pms2 mutant mice. At higher levels of NMNU, where the apoptotic response is independent of Mlh1 and Pms2, no gene dependent increase in mutation frequency was observed. These results argue that the MutSalpha and MutLalpha are not equally important in their ability to signal apoptosis. However, when MMR does mediate apoptosis, perturbation of this response leads to long-term persistence of mutant cells in vivo.

Adaptor Proteins, Signal Transducing↗
PubMed2005

Familial mutations in PMS2 can cause autosomal dominant hereditary nonpolyposis colorectal cancer.

BACKGROUND & AIMS: Hereditary nonpolyposis colorectal cancer (HNPCC) is an autosomal dominant disorder caused by familial mutations in some of the genes responsible for DNA mismatch repair. Mutations in the MLH1, MSH2, and MSH6 genes have been documented in this disorder, but there have been limited and conflicting data about the role of another mismatch repair gene, PMS2. It has recently been suggested that mutations in the PMS2 gene do not cause an autosomal dominant disorder. In addition, mutations in each of these 4 mismatch repair genes have been shown to cause an autosomal recessive cancer syndrome in children that is distinct from hereditary nonpolyposis colorectal cancer. We reviewed a cohort of patients for evidence of an autosomal dominant disorder caused by a mutation in the PMS2 gene. METHODS: A cohort of tumor samples from patients with features suggestive of HNPCC was tested for microsatellite instability, the molecular hallmark of HNPCC, and exclusive loss of expression of the PMS2 gene in tumor tissue. RESULTS: A kindred was identified with autosomal dominant HNPCC due to a familial loss-of-function mutation in the PMS2 gene. This is the first description of such a kindred. CONCLUSION: Mutations in the PMS2 gene can, like mutations in other mismatch repair genes, cause both autosomal dominant HNPCC in adults and an autosomal recessive cancer syndrome in children.

Adenocarcinoma↗
PubMed2002

Contribution of human mlh1 and pms2 ATPase activities to DNA mismatch repair.

MutLalpha, a heterodimer composed of Mlh1 and Pms2, is the major MutL activity in mammalian DNA mismatch repair. Highly conserved motifs in the N termini of both subunits predict that the protein is an ATPase. To study the significance of these motifs to mismatch repair, we have expressed in insect cells wild type human MutLalpha and forms altered in conserved glutamic acid residues, predicted to catalyze ATP hydrolysis of Mlh1, Pms2, or both. Using an in vitro assay, we showed that MutLalpha proteins altered in either glutamic acid residue were each partially defective in mismatch repair, whereas the double mutant showed no detectable mismatch repair. Neither strand specificity nor directionality of repair was affected in the single mutant proteins. Limited proteolysis studies of MutLalpha demonstrated that both Mlh1 and Pms2 N-terminal domains undergo ATP-induced conformational changes, but the extent of the conformational change for Mlh1 was more apparent than for Pms2. Furthermore, Mlh1 was protected at lower ATP concentrations than Pms2, suggesting Mlh1 binds ATP with higher affinity. These findings imply that ATP hydrolysis is required for MutLalpha activity in mismatch repair and that this activity is associated with differential conformational changes in Mlh1 and Pms2.

Adaptor Proteins, Signal Transducing↗
PubMed2004

Pms2 is a genetic enhancer of trinucleotide CAG.CTG repeat somatic mosaicism: implications for the mechanism of triplet repeat expansion.

The expansion of CAG.CTG repeat sequences is the cause of several inherited human disorders. Longer alleles are associated with an earlier age of onset and more severe symptoms, and are highly unstable in the germline and soma with a marked tendency towards repeat length gains. Germinal expansions underlie anticipation; whereas age-dependent, tissue-specific, expansion-biased somatic instability probably contributes toward the progressive nature and tissue-specificity of the symptoms. The mechanism(s) of repeat instability is not known, but recent data have implicated mismatch-repair (MMR) gene mutS homologues in driving expansion. To gain further insight into the expansion mechanism, we have determined the levels of somatic mosaicism of a transgenic expanded CAG.CTG repeat in mice deficient for the Pms2 MMR gene. Pms2 is a MutL homologue that plays a critical role in the downstream processing of DNA mismatches. The rate of somatic expansion was reduced by approximately 50% in Pms2-null mice. A higher frequency of rare, but very large, deletions was also detected in these animals. No significant differences were observed between Pms2(+/+) and Pms2(+/-) mice, indicating that a single functional Pms2 allele is sufficient to generate normal levels of somatic mosaicism. These findings reveal that as well as MMR enzymes that directly bind mismatched DNA, proteins that are subsequently recruited to the complex also play a central role in the accumulation of repeat length changes. These data suggest that somatic expansion results not by replication slippage, single stranded annealing or simple MutS-mediated stabilization of secondary structures, but by inappropriate DNA MMR.

Adenosine Triphosphatases↗
PubMed2006

PMS2 mutations in childhood cancer.

Until recently, the PMS2 DNA mismatch repair gene has only rarely been implicated as a cancer susceptibility locus. New studies have shown, however, that earlier analyses of this gene have had technical limitations and also that the genetic behavior of mutant PMS2 alleles is unusual, in that, unlike MLH1 or MSH2 mutations, PMS2 mutations show low heterozygote penetrance. As a result, a dominantly inherited cancer predisposition has not been a feature reported in families with PMS2 mutations. Such families have instead been ascertained through childhood-onset cancers in homozygotes or through apparently sporadic colorectal cancer in heterozygotes. We present further information on the phenotype associated with homozygous PMS2 deficiency in 13 patients from six families of Pakistani origin living in the United Kingdom. This syndrome is characterized by café-au-lait skin pigmentation and a characteristic tumor spectrum, including leukemias, lymphomas, cerebral malignancies (such as supratentorial primitive neuroectodermal tumors, astrocytomas, and glioblastomas), and colorectal neoplasia with an onset in early adult life. We present evidence for a founder effect in five families, all of which carried the same R802-->X mutation (i.e., arginine-802 to stop) in PMS2. This cancer syndrome can be mistaken for neurofibromatosis type 1, with important management implications including the risk of the disorder occurring in siblings and the likelihood of tumor development in affected individuals.

Adenosine Triphosphatases↗
PubMed2026

A PMS2-deficient pediatric high-grade glioma with PI3K-pathway mutations and adjacent developmental venous anomaly suggestive of CMMRD.

PURPOSE: Constitutional mismatch repair deficiency (CMMRD) is a rare hereditary cancer predisposition syndrome that frequently manifests with pediatric high-grade gliomas. However, recognition remains challenging, particularly in the absence of a clear family history. We report a pediatric high-grade glioma with PMS2 deficiency and complex molecular alterations to highlight key diagnostic clues and the importance of routine mismatch repair assessment. METHODS: Clinical, radiological, histopathological, immunohistochemical, and molecular findings of an 8-year-old girl presenting with a high-grade glioma were retrospectively evaluated. Immunohistochemistry included glial and mismatch repair markers. Targeted next-generation sequencing was performed to assess tumor mutational burden and pathogenic variants. RESULTS: Neuroimaging revealed a right frontoparietal mass associated with an adjacent developmental venous anomaly. Histopathology demonstrated a diffuse pediatric-type high-grade glioma with pseudopapillary architecture and marked mitotic activity. Immunohistochemistry showed diffuse p53 overexpression in tumor cells and complete loss of PMS2 expression in both tumor and non-neoplastic cells, supporting constitutional mismatch repair deficiency. Molecular analysis revealed an ultra-hypermutated profile with a tumor mutational burden of 117.4 mutations/Mb, a pathogenic PMS2 frameshift variant, and co-occurring alterations in TP53, PIK3CA, PIK3R1, and PTEN. The presence of PI3K-pathway mutations alongside a venous anomaly suggested a potential biological association. CONCLUSION: This case illustrates the characteristic clinicopathological and molecular features of CMMRD-associated pediatric high-grade glioma and underscores the critical role of routine mismatch repair immunohistochemistry. Integrated histological and genomic evaluation is essential for accurate diagnosis, appropriate genetic counseling, and potential therapeutic implications. Key Points • This case represents a pediatric high-grade glioma arising in the setting of PMS2-related constitutional mismatch repair deficiency (CMMRD). • The tumor exhibited an ultra-hypermutated profile with co-occurring TP53, PIK3CA, PIK3R1, and PTEN mutations. • Loss of PMS2 expression in both tumor and non-neoplastic cells was critical in establishing the diagnosis of CMMRD. • The presence of a developmental venous anomaly may relate to underlying PIK3R1 pathway alterations. • Routine mismatch repair immunohistochemistry is essential in pediatric high-grade gliomas, even in the absence of a family history.

Humans↗
PubMed2007

Elevated levels of the mismatch repair protein PMS2 are associated with prostate cancer.

BACKGROUND: Defects in mismatch repair (MMR) proteins have been identified in various types of cancer. However, an association with prostate cancer has been controversial. Defective MMR results in genome instability with detrimental consequences that significantly contribute to tumorigenesis. This study determined alterations in key MMR protein levels in prostate cancer with the goal to identify prognostic markers. METHODS: Prostatectomy samples were immunohistochemically stained and the relative presence or absence of key proteins MSH2, MLH1, and PMS2 determined. Cancer tissue of distinct grades was compared with the normal surrounding tissue. Microsatellite instability (MSI) in altered tissues was determined according to NCI guidelines. RESULTS: In contrast to reports that associate a lack of individual MMR proteins with tumorigenesis, a significant increase in PMS2 levels was identified in PIN lesions and prostate cancer tissue. This elevation in PMS2 was independent of changes in levels in its heterodimeric partner, MLH1. Prostate tumors with elevated levels of PMS2 were genetically unstable, which was corrected by MLH1 co-elevation. CONCLUSIONS: This is the first documentation of detrimental consequences associated with the increase in a MMR protein in human cancer. This study recognizes PMS2 elevation as a prognostic marker in pre-neoplastic and prostate cancer lesions. This result has significant implications for future diagnostic and treatment measures.

Adaptor Proteins, Signal Transducing↗
PubMed1995

Male mice defective in the DNA mismatch repair gene PMS2 exhibit abnormal chromosome synapsis in meiosis.

Using gene targeting in embryonic stem cells, we have derived mice with a null mutation in a DNA mismatch repair gene homolog, PMS2. We observed microsatellite instability in the male germline, in tail, and in tumor DNA of PMS2-deficient animals. We therefore conclude that PMS2 is involved in DNA mismatch repair in a variety of tissues. PMS2-deficient animals appear prone to sarcomas and lymphomas. PMS2-deficient males are infertile, producing only abnormal spermatozoa. Analysis of axial element and synaptonemal complex formation during prophase of meiosis I indicates abnormalities in chromosome synapsis. These observations suggest links among mismatch repair, genetic recombination, and chromosome synapsis in meiosis.

Adenosine Triphosphatases↗
PubMed2026

Analysis of structure and conservation for supporting functional evaluation of PMS2 missense variants.

Germline defects in mismatch repair (MMR) genes are known to significantly increase the risk of developing certain types of cancers, notably colorectal and endometrial cancers. These conditions are characterized under Lynch syndrome. Accurate diagnosis of this predisposition, along with meaningful predictive testing for family members, necessitates the identification of pathogenic variants. However, classifying small coding genetic variants identified in cancer patients is very challenging, specifically in the case of PMS2 variants, since PMS2 pathogenic variants display a lower penetrance and less severe phenotype and therefore a lower tumor burden in affected families. We have assembled clinical data on four PMS2 missense variants of uncertain significance (VUS) identified in 23 patients (p.(Asp286Gly), p.(Asn335Ser), p.(Ile679Thr) and p.(Arg799Trp)). For these variants, functional testing was performed (RNA splicing, protein stability and catalytic activity). Since many protein ortholog sequences and accurate predictive models from AlphaFold2 are available, we also included a systematic analysis of residue conservation and structural role (ConStruct assessment). Overall, our findings indicate that p.(Asp286Gly) and p.(Arg799Trp) behave similarly to wild-type PMS2 and are thus probably neutral. In contrast, p.(Asn335Ser) and p.(Ile679Thr) conferred defects in protein expression or MMR activity. These could be explained by the relevant roles of these amino acids in MLH1-PMS2-N-terminal dimerization (p.Asn335) and C-terminal dimerization (p.Ile679). Our data thus suggest that p.(Asp286Gly) and p.(Arg799Trp) are benign, while the tumor risk in the other two variants remains to be established. Taken together, we suggest roadmaps for the individualized evaluation of difficult uncertain variants by comprising information from all available sources.

Humans↗
PubMed2001

Elevated mutant frequencies and increased C : G-->T : A transitions in Mlh1-/- versus Pms2-/- murine small intestinal epithelial cells.

Mutations in DNA mismatch repair (MMR) genes are associated with increased genomic instability and susceptibility to cancer. Mice rendered deficient in either Mlh1 or Pms2 as a result of gene targeting are prone to tumorigenesis, particularly, lymphomas. In addition, although Mlh1-/- mice also develop small intestinal adenomas and adenocarcinomas, Pms2-/- animals remain free of such tumors. To establish whether this phenotypic dichotomy might be associated with a quantitative and/or qualitative difference in genomic instability in these mice, we determined small intestinal epithelial cell DNA mutant frequency and mutation spectrum using a transgenic lambda-phage lacI reporter system. Mutant frequencies obtained from both Mlh1-/- and Pms2-/- mice revealed elevations of 18- and 13-fold, respectively, as compared to their wild-type littermates. Interestingly, we found that C : G-->T : A transitions were significantly elevated in Mlh1-/- mice, accounting in large measure for the 1.5-fold lacI mutant frequency increase seen in these animals. We hypothesize that the increased level of C : G-->T : A mutations may explain, in part, why Mlh1-/- mice, but not Pms2-/- mice, develop small intestinal tumors. Furthermore, the difference in the lacI mutational spectrum of Mlh1-/- and Pms2-/- mice suggests that other MutL-like heterodimers may play important roles in the repair of G : T mispairs arising within murine small intestinal epithelial cells.

Adaptor Proteins, Signal Transducing↗
PubMed2003

Interaction of mismatch repair protein PMS2 and the p53-related transcription factor p73 in apoptosis response to cisplatin.

Mismatch repair (MMR) proteins contribute to genome integrity by correcting replication errors. In higher eukaryotes, MMR proteins also regulate the cellular response to DNA lesions such as oxidized, alkylated, or crosslinked bases. Previous studies have linked MMR proteins to the activation of apoptosis through p53-dependent and p53-independent mechanisms. MMR-deficient cells exhibit variable defects in the induction of p53 and its related p73, which are activators of apoptosis. However, the specific role of each MMR protein in the regulation of apoptosis has not been determined. Here, we describe an interaction between PMS2, an MMR protein, and p73. This interaction causes the stabilization of p73 and the redistribution of PMS2 to the nuclear compartment. Exposure to cisplatin enhances the association between PMS2 and p73. Moreover, stimulation of the p73 proapoptotic function by cisplatin requires PMS2. These results suggest that PMS2 contributes to genome integrity not only through DNA repair but also by enhancing DNA damage-induced apoptosis.

Adenosine Triphosphatases↗
PubMed1997

Elevated levels of mutation in multiple tissues of mice deficient in the DNA mismatch repair gene Pms2.

The Pms2 gene has been implicated in hereditary colon cancer and is one of several mammalian homologs of the Escherichia coli mutL DNA mismatch repair gene. To determine the effect of Pms2 inactivation on genomic integrity in vivo, hybrid transgenic mice were constructed that carry targeted disruptions at the Pms2 loci along with a chromosomally integrated mutation reporter gene. In the absence of any mutagenic treatment, mice nullizygous for Pms2 showed a 100-fold elevation in mutation frequency in all tissues examined compared with both wild-type and heterozygous litter mates. The mutation pattern in the nullizygotes was notable for frequent 1-bp deletions and insertions within mononucleotide repeat sequences, consistent with an essential role for PMS2 in the repair of replication slippage errors. Further, the results demonstrate that high rates of mutagenesis in multiple tissues are compatible with normal development and life and are not necessarily associated with accelerated aging. Also, the finding of genetic instability in all tissues tested contrasts with the limited tissue distribution of cancers in the animals, raising important questions regarding the role of mutagenesis in carcinogenesis.

Adenosine Triphosphatases↗