Mutation Analysis of RB1 Gene in Peripheral Blood of Retinoblastoma Patients / 대한해부학회지

Retinoblastoma, a child tumor of the eye, is caused by two mutational events at the retinoblastoma gene (RB1). Retinoblastoma occurs in both hereditary and nonhereditary forms, and this distinction has important implications for patients and their families. In most patients with isolated unilateral retinoblastoma, tumor development is initiated by somatic inactivation of both alleles of the RB1 gene. Some of patients with hereditary retinoblastoma initially present with unilateral disease, and up to 10% to 12% of these patients only express unilateral disease. Germline mutation in RB1 gene confer hereditary predisposition to retinoblastoma. This study was designed to identify germline mutations in RB1 gene in Korean retinoblastoma patients. Samples of peripheral blood were obtained from 5 patients with isolated unilateral tumors. To detect genetic alteration in RB1 gene, exon 8, 10, 11, 14~20, 22 and 23 were investigated by PCR -SSCP. Bandshifts on SSCP were found in three out of 5 patients at exon 8. There were same point mutations from CGA (arginine) to TGA (stop codon) at codon 251 in exon 8 of RB1 gene. This point mutation has not been found in Korean patient with retinoblastma. But it is common mutation on the Western reports and Korea 's annual incidence of this tumor is similar in proportion to that of the West. Therefore, if a lot of patients are investigated to elucidate RB1 mutation this point mutation will be found. Identification of the germline mutation in RB1 gene would help to improve the presymptomatic diagnosis and clinical management to retinoblastoma patients.

Alteration of Karyotype and Cell Cycle Induced by UVB Irradiation In Human Keratinocytes / 대한해부학회지

To investigate the change of cell cycle by genotoxic stress and rebound proliferation in human keratinocytes, the proportions of cell cycle phases were estimated with challenge of UVB irradiation (200 J/m2). With UVB irradiation cell cycle was estimated by Cell Fit program in Flowcytometer, and main change of the cell cycle was S-phase pro-longation. In karyotyping, near diploid number of chromosomes changed to hypoteraploid number. Cell cycle phase was estimated in two groups of cells, near diploid and hypoteraploid. In near dipoid cells, S-phase prolongation was specific phenomenon, while specific G0-G1 phase prolongation was shown in hypoteraploid cells which made transformed foci in culture. The new structural anomalies were del (5q21), 8p+, and t (5 : 8)(q21 : pter). Among them, del (5q21) was found in all transformed hypotetraploid cells. These data suggest that progress of cell cycle could be [G1-S-(G2-G1)-S] by UVB irradiation and deletion of 5q21 has a key role for anchorage independent growth, which is deletion of tumor suppressor gene APC locus. That is one of important mechanisms in keratinocyte transformation by UVB irradiation. With the changes of chromosome number and cell cycle, sizes of nuclei got to bigger by two times and growth rate was delayed.

Telomerase Activity of Endometrium Related to the Effects of the Sex Steroid Hormone and Endometrial Cancer / 대한부인종양콜포스코피학회잡지

During the reproductive period, human endometrium undergoes a pattern of cyclic change. Human endometrium undergoes a complex pattern of proliferation, secretory activity, and menstruation over an approximately 28 days period. Proliferative activity is highest during late proliferative phase under influence of estrogen, and minimal activity in the late secretory and menstrual phase. To study a possible change of telomerase activity during menstrual cycle, telomerase activities in normal and hormone treated endometrium were tested using telomerase repeat amplification protocol(TRAP) assay. Telomerase activities were detected in 9 of 10 proliferative endometrium(90%), and maximal activity was shown in late proliferative phase. Only 3 of 10 secretory endometrium(30%) revealed weak activity. However telomerase activity was not detected in menstrual phase endometrium(N 2) and senile endometrium(N=3). Four of tamoxifen treated endometrium(N 4) and 1 of provera treated endometrium(N 3) Levels of telomerase activity of treated endometrium(N 4) and late proliferative endometrium(N 6) were as high as them of detected in endometrial cancer and hyperplasia. Above findings reveal that telomerase activity of endometrium is changed according to menstrual cycle, And the level of telomerase activity is related to proliferative activity of endometrium that is dependent on the status of female sex steroid hormone and tamoxifen treatment.

Telomere Length and Telomerase Activation in Carcinoma of the Cervix related to Human papilloma Virus(HPV) Infection / 대한부인종양콜포스코피학회잡지

E6 and E7 proteins produced by oncogenic HPV bind to the protein products of cellular tumor suppressor genes p53 and Rb, respectively. This mechanism has been suggested to contribute to the oncogenesis of HPV-infected carcinoma. The cells which are blocked the function of p53 and pub protein continue to divide by bypassing Ml stage known as antiproliferative mechanism but telomeres, the genetic elements at the ends of chromosomes, continue to shorten until the telomeres are so short that further replication is prevented(M2 stage). But telomeres can be maintained if telomerase is derepressed, giving rise to a immortal cell. The present study has been investigated the presence of HPV, telomere length and telomerase activation in cervical carcinomas. HPV DNA were detected by polymerase chain reaction in 17 of 19 precancerous lesions and cervical carcinoma specimens; HPV16 was detected in 12 cases, HPV18 in one case, HPV33 in two cases, and HPV58 in two cases. Overall, the prevalence of HPV was 89.5%. To study the difference of telomere length in cervical carcinomas and each normal counterpart, DNAs were digested with Hinf III and Rsa I to liberate the terminal restriction fragments(TRF). TRFs were resolved on agarose gels and detected by hybridization to the telomeric probe. This result indicated that there were no significant difference of TRF length in samples tested except two cases. TRF length of one carcinoma specimen was found to be significantly increased as compared with normal counterpart, but the other was found to be significantly decreased. Telomerase activity was detected in 4 of dysplasia specimens(5 cases), all of carcinoma in situ(CIS), and 6 of 8 invasive carcinoma. Overall, telomerase activity was detected in 84%. The degree of telomerase activity was high in 2 of dysplasia, 3 of CIS, and 3 of invasive carcinoma. And then there was no apparent association between HPV types and levels of telomerase activity. However, telomerase activity was depressed in invasive carcinoma as compared to dysplasia and CIS. These results suggest that HPV may be a possible causative agent in cervical carcinoma. In addition, telomerase activation may be necessary for the immortalization of cells and the progression of malignancy in cervical carcinoma.