Biomedical subjects

Keng-Ling Wallin

Publications and source records attributed to Keng-Ling Wallin.

5 recordsLinked to original sources

PubMed2003

Multiple-primer DNA sequencing method.

A multiple-primer DNA sequencing approach suitable for genotyping, detection and identification of microorganisms and viruses has been developed. In this new method two or more sequencing primers, combined in a pool, are added to a DNA sample of interest. The oligonucleotide that hybridizes to the DNA sample will function as a primer during the subsequent DNA sequencing procedure. This strategy is suited for selective detection and genotyping of relevant microorganisms and samples harboring different DNA targets such as multiple variant/infected samples as well as unspecific amplification products. This method is used here in a model system for detection and typing of high-risk oncogenic human papilloma viruses (HPVs) in samples containing multiple infections/variants or unspecific amplification products. Type-specific sequencing primers were designed for four of the most oncogenic (high-risk) HPV types (HPV-16, HPV-18, HPV-33, and HPV-45). The primers were combined and added to a sample containing a mixture of one high-risk (16, 18, 33, or 45) and one or two low-risk types. The DNA samples were sequenced by the Pyrosequencing technology and the Sanger dideoxy sequencing method. Correct genotyping was achieved in all tested combinations. This multiple-sequencing primer approach also improved the sequence data quality for samples containing unspecific amplification products. The new strategy is highly suitable for diagnostic typing of relevant species/genotypes of microorganisms.

DNA Primers↗

PubMed2002

Genetic alterations in cervical carcinomas: frequent low-level amplifications of oncogenes are associated with human papillomavirus infection.

The development of cervical carcinoma is closely associated with HPV infection. However, other genetic alterations also play an important role. In this study, we analyzed copy number alterations of several oncogene loci in a panel of 84 cervical tumors. Sixty-five (77%) tumors were HPV DNA-positive, and most were infected with type 16 or type 18 or both. The oncogenes studied include PIK3CA at 3q26.3, TERT at 5p15.33, C-MYC at 8q24, CCND1 at 11q13.3, ERBB2 at 17q21.2 and locus region 20q13.2. Amplification of 1 or more genes was detected in 55 (65%) cases using interphase FISH. PIK3CA was amplified in 43% of tumors, followed by TERT (33%), 20q13.2 (30%), ERBB2 (29%), C-MYC (25%) and CCND1 (12%). Most tumors showed low-level amplification with 3-7 copies of these genes, and complex changes involving 3 or more genes occur more frequently in tumors at advanced stages. Increased protein expression of c-erbB2 and c-myc was observed in tumors with the corresponding gene amplification. Oncogene alterations were found more often in HPV-infected cases, particularly for C-MYC and TERT. These findings indicate that HPV-associated cervical carcinomas bear frequent alterations of these genes, which may have critical biologic impact on the development and progression of carcinoma of the uterine cervix.

Base Sequence↗

PubMed2002

A population-based prospective study of Chlamydia trachomatis infection and cervical carcinoma.

Persistent human papillomavirus (HPV) infection is an established cause of cervical cancer, but the role of other sexually transmitted agents, most notably Chlamydia trachomatis, has not been well defined. The women participating in the population-based cervical cancer screening program in Västerbotten county of Northern Sweden were followed up for up to 26 years to identify 118 women who developed cervical cancer after having had a normal Pap smear (on average 5.6 years later; range 0.5 months-26 years). As controls, we selected another 118 women who were matched by birth cohort, time-point of sampling of the baseline normal smear and who had a normal smear at the time when the corresponding case was diagnosed with cancer. The Pap smears and cervical cancer biopsies were analyzed by PCR for C. trachomatis DNA and for HPV DNA. At baseline, C. trachomatis DNA was present in 8% of cases but not among any one of the controls. The relative risk for cervical cancer associated with past C. trachomatis infection, adjusted for concomitant HPV DNA positivity, was 17.1 (95% CI 2.6-infinity). The presence of C. trachomatis and of HPV were not interrelated. Whereas C. trachomatis was primarily found in specimens taken many years before cancer diagnosis, HPV DNA was associated with a short lag time before cancer diagnosis. Whereas most women who were HPV DNA-positive in the prediagnostic smear were also positive for the same virus in the cervical cancer biopsy, none of the women were positive for C. trachomatis in both the prediagnostic smear and in the subsequent cervical cancer. In conclusion, a prior cervical C. trachomatis infection was associated with an increased risk for development of invasive cervical cancer.

Adult↗

PubMed2002

Risk of invasive cervical cancer associated with polymorphic HLA DR/DQ haplotypes.

The genes encoding human leukocyte antigens (HLA) have shown to be associated with cervical neoplasia. To obtain reliable data on HLA associations with cervical tumors, the study should be performed within a strictly defined cohort. To investigate the population attributable risk of cervical cancer associated with the HLA class II haplotypes DR15 and DQ6 (DQA1*0102 and DQB1*0602), we performed a nested case-control study of 85 women who developed invasive cervical cancer and 120 healthy women from a population-based cohort of Swedish women. The relative risks of cervical cancer among DR15 and DQ6-positive women were 3.73 [confidence interval (CI): 1.8-7.4] and 4.33 (CI: 2.1-8.5), corresponding to population attributable proportions of 27.9% and 30.8%, respectively. A susceptibility locus in the HLA class II region is involved in a substantial fraction of the etiology of cervical cancer.

Adult↗

PubMed2002

Amplification of the telomerase reverse transcriptase (hTERT) gene in cervical carcinomas.

The expression of telomerase reverse transcriptase (hTERT), the catalytic component of the telomerase complex, is required for activation of telomerase during immortalization and transformation of human cells. However, the biochemical and genetic mechanisms governing hTERT expression remain to be elucidated. In the present study, we examined hTERT amplification as a potential genetic event contributing to telomerase activation in cervical carcinomas. An amplification of the hTERT gene was found in 1/4 cervical cancer cell lines and 21/88 primary tumor samples derived from the patients with cervical carcinomas. An increase in the hTERT copy number was significantly correlated with higher levels of hTERT protein expression. Moreover, the hTERT alterations with the enhanced hTERT expression were exclusively observed in those tumors with high-risk human papillomavirus infection. Taken together, the hTERT gene amplification, directly or indirectly targeted by human papillomavirus, may be one of the driving forces responsible for upregulation of hTERT expression and activation of telomerase in cervical cancers.

Carcinoma↗