GENETIC INSTABILITY IN CERVICAL CARCINOMA

Objective: The role of human papillomavirus (HPV) in the development of cervical carcinoma has been clearly established but other factors could be involved in cervical tumorigenesis such as loss of heterozygosity (LOH) and microsatellite instability (MI). The aim of the present study was to investigate the genetic instability in cervical carcinoma tissues and provide evidence for discovering new tumor suppressor genes and screening diagnostic molecular marker of cervical carcinoma. Methods: Fifty primary cervical carcinoma samples from high-incidence area were analyzed by PCR for HPV16 infection, LOH and microsatellite instability. Results: HPV16 was detected in 88% of the cases. Sixty-six percent of total cases showed LOH with no more than 3 different loci per case. The highest frequency of the allelic loss was found in D18S474 (18q21, 40.5%). MI was detected in 4 cases (8%) only. Conclusion: Different percentages of LOH on specific chromosomal regions were found and MI was very infrequent in cervical carcinoma. The putative suppressor gene(s) could be located on specific chromosome regions such as 18q, and genetic instability could be involved in cervical tumorigenesis.

Micronucleus analysis in patients with colorectal adenocarcinoma and colorectal polyps

AIM:To determine,by counting micronucleus (MN) frequencies,whether chromosomal or DNA damage have an effect on the pathogenesis of early colorectal adenocarcinoma (CRC). METHODS:We analyzed MN frequencies in 21 patients with CRC,24 patients with colon polyps [10 neoplastic polyps (NP) and 14 non-neoplastic polyps (NNP)] and 20 normal controls. RESULTS:MN frequency was significantly increased in CRC patients and in NP patients compared with controls (3.72 ± 1.34,3.58 ± 1.21 vs 1.97 ± 0.81,P < 0.001). However,there was no difference in the MN frequency between CRC patients and NP patients (P > 0.05). Similarly,there was no difference in the MN frequency between NNP patients (2.06 ± 0.85) and controls (P > 0.05). CONCLUSION:Our results suggest increased chromosome/DNA instabilities may be associated with the pathogenesis of early CRC.

Alternative splicing of DNA damage response genes and gastrointestinal cancers

Alternative splicing,which is a common phenomenon in mammalian genomes,is a fundamental process of gene regulation and contributes to great protein diversity.Alternative splicing events not only occur in the normal gene regulation process but are also closely related to certain diseases including cancer.In this review,we briefly demonstrate the concept of alternative splicing and DNA damage and describe the association of alternative splicing and cancer pathogenesis,focusing on the potential relationship of alternative splicing,DNA damage,and gastrointestinal cancers.We will also discuss whether alternative splicing leads to genetic instability,which is considered to be a driving force for tumorigenesis.Better understanding of the role and mechanism of alternative splicing in tumorigenesis may provide new directions for future cancer studies.

Conditional Mutations in Drosophila

The aim of this study was to obtain unusual mutations called conditional. The mutations manifest in some, not all representatives of a species. Collections of these mutations in chromosomes X, 2, and 3 of Drosophila melanogaster were established. Sex of fly or chromosomal rearrangement was the conditions providing ＂manifestation-non manifestation＂ of these mutations. The mutations differ from the usual by a set of properties. The salient differences in addition to conditional manifestation include： manifestation dependence on the spatial arrangement of chromosomal material in the genome, parental effects （maternal or paternal） of the mutant, capacity for transferring the genome from stable to unstable state. It is suggested that conditional mutations are mutant variants of Drosophila regulatory genes contained by the large Genomic Regulatory Network of Drosophila. Thus, the genes of this category can be detected by using special breeding procedures, mutations of these genes have unusual manifestation.

CAS9 is a genome mutator by directly disrupting DNA-PK dependent DNA repair pathway

With its high efficiency for site-specific genome editing and easy manipulation,the clustered regularly interspaced short palindromic repeats(CRISPR)/CRISPR associated protein 9(CAS9)system has become the most widely used gene editing technology in biomedical research.In addition,significant progress has been made for the clinical development of CRISPR/CAS9 based gene therapies of human diseases,several of which are entering clinical trials.Here we report that CAS9 protein can function as a genome mutator independent of any exogenous guide RNA(gRNA)in human cells,promoting genomic DNA double-stranded break(DSB)damage and genomic instability.CAS9 interacts with the KU86 subunit of the DNA-dependent protein kinase(DNA-PK)complex and disrupts the interaction between KU86 and its kinase subunit,leading to defective DNA-PK-dependent repair of DNA DSB damage via non-homologous end-joining(NHEJ)pathway.XCAS9 is a CAS9 variant with potentially higher fidelity and broader compatibility,and dCAS9 is a CAS9 variant without nuclease activity.We show that XCAS9 and dCAS9 also interact with KU86 and disrupt DNA DSB repair.Considering the critical roles of DNA-PK in maintaining genomic stability and the pleiotropic impact of DNA DSB damage responses on cellular proliferation and survival,our findings caution the interpretation of data involving CRISPR/CAS9-based gene editing and raise serious safety concerns of CRISPR/CAS9 system in clinical application.

Mathematical modeling of female breast cancer in Japan

Cancer incidence rates are significantly diferent all over the world.Breast cancer is affected by many factors,the most important being genetics and lifestyle.The aim of this paper is to study the mutation mechanisms of breast cancer for Japanese women by fitting the incidence data of three high-quality population areas in Japan from 1985 to 2010.To achieve this goal,we have set up multi-stage models within the mathematical model of Moolgavkar,Venzon,and Knudson.Such models take both mutation rates and clonal expansion rates as parameters in each compartment into consideration.Based on our simulation outcomes,two to twelve driver mutations are sufficient in the pathway to female breast cancer in Japan.On the other hand,a previous study demonstrated that breast cancer in American women requires two to fourteen gene mutations to get a cancerous cell.Moreover,the 3-stage mat hematical model is the optimal model as it fits clinical data very nicely for all affected cases of females in Japan and the US.The genetic instability has a promincnt effect on the tumorigenesis of Japanese females caused by the first four driver mutations.The calculated results for Japanese women are compared with previous works for American women.