[Molecular basis of cervical carcinogenesis by high-risk human papillomaviruses]

Cervical cancer in Ethiopia: a review of the literature

BACKGROUND

Cervical cancer is one of the most common malignancies affecting women worldwide with large geographic variations in prevalence and mortality rates. It is one of the leading causes of cancer-related deaths in Ethiopia, where vaccination and screening are less implemented. However, there is a scarcity of literature in the field. Therefore, the objective of this review was to describe current developments in cervical cancer in the Ethiopian context. The main topics presented were the burden of cervical cancer, knowledge of women about the disease, the genotype distribution of Human papillomavirus (HPV), vaccination, and screening practices in Ethiopia.

METHODS

Published literature in the English language on the above topics until May 2021 were retrieved from PubMed/Medline, SCOPUS, Google Scholar, and the Google database using relevant searching terms. Combinations of the following terms were considered to retrieve literature; < Cervical cancer, uterine cervical neoplasms, papillomavirus infections, papillomavirus vaccines, knowledge about cervical cancer, genotype distribution of HPV and Ethiopia > . The main findings were described thematically.

RESULTS

Cervical cancer is the second most common and the second most deadly cancer in Ethiopia, The incidence and prevalence of the disease is increasing from time to time because of the growth and aging of the population, as well as an increasing prevalence of well-established risk factors. Knowledge and awareness about cervical cancer is quite poor among Ethiopian women. According to a recent report (2021), the prevalence of previous screening practices among Ethiopian women was at 14%. Although HPV 16 is constantly reported as the common genotype identified from different grade cervical lesions in Ethiopia, studies reported different HPV genotype distributions across the country. According to a recent finding, the most common HPV types identified from cervical lesions in the country were HPV-16, HPV-52, HPV-35, HPV-18, and HPV-56. Ethiopia started vaccinating school girls using Gardasil-4™ in 2018 although the coverage is insignificant. Recently emerging reports are in favor of gender-neutral vaccination strategies with moderate coverage that was found superior and would rapidly eradicate high-risk HPVs than vaccinating only girls.

CONCLUSIONS

Cervical cancer continues to be a major public health problem affecting thousands of women in Ethiopia. As the disease is purely preventable, classic cervical cancer prevention strategies that include HPV vaccination using a broad genotype coverage, screening using a high precision test, and treating cervical precancerous lesions in the earliest possible time could prevent most cervical cancer cases in Ethiopia. The provision of a focused health education supported by educational materials would increase the knowledge of women about cervical cancer in general and the uptake of cervical cancer prevention and screening services in particular.

MicroRNA in cervical cancer: OncomiRs and tumor suppressor miRs in diagnosis and treatment

Cervical cancer is a female-specific disease with a high incidence and mortality. MicroRNAs (miRNAs) are implicated in posttranscriptional regulation of gene expression and in the pathogenic mechanisms of cancer, suggesting their importance in diagnosis and treatment. miRNAs may have roles in the pathogenesis of cervical cancer based on the increases or decreases in several specific miRNAs found in patients with this disease. The miRNAs implicated in cervical cancer are miR-21, miR-126, and miR-143, and clinical application of these miRNAs for diagnosis and treatment is under investigation. Methods for diagnosis of cervical cancer include analysis of changes in the levels of specific miRNAs in serum and determination of aberrant hypermethylation of miRNAs. Supplementation of miR-143 or inhibition of miR-21 activity in vivo may be therapeutic strategy for cervical cancer. Previous approaches to development of siRNA as a drug have provided information for establishment of therapy based on these approaches, and an anti-miR-21 inhibitor has been developed. miRNAs also have effects on drug resistance and may be useful in combination therapy with other drugs.

[Regulation of human papillomavirus (HPV) genome replication in the viral life cycle and its association with the viral persistence and cancer development]

High-risk human papillomavirus (HR-HPV) infections account for more than 5% of all cancers (11% in women) such as cervical cancer worldwide. HPVs infect to basal cells of the stratified squamous epithelium and establish persistent infection within the basal compartment. HR-HPV infections can persist more than a decade, leading to development of cancers. The life cycle of HPVs is tightly associated with the differentiation processes of the stratified squamous epithelium; the replication of the viral genome and the expression of the viral genes are strictly regulated depending on differentiation of the host keratinocytes. The viral genome is transiently amplified immediately following infection and then maintained at constant copy numbers in the basal cells. In terminally differentiating keratinocytes, the viral genome is drastically amplified. However, molecular mechanisms underlying switching these three stages of viral genome replication in the viral life cycle are poorly understood. Recently, it has become evident that DNA damage response pathways are involved in the regulation of HPV genome replication. In this review, we would like to introduce recent findings describing the associations of DNA damage response with HPV genome replication.

Construction and identification of a yeast two-hybrid bait vector and its effect on the growth of yeast cells and the self-activating function of reporter genes for screening of HPV18 E6-interacting protein

By using a yeast two-hybrid system, a yeast two-hybrid bait vector was constructed and identified for screening of the HPV18 E6-interacting proteins, and its effects on the growth of yeast cells and the activation of reporter genes were investigated. Total mRNA extracted from Hela cells was reversely transcribed into cDNA. Fragment of HPV18 E6 cDNA was amplified using RT-PCR and directly ligated to the pGBKT7 vector. The recombinant plasmid was confirmed by restriction endonuclease analysis and DNA sequencing. The recombinant pGBKT7-HPV18 E6 plasmid and empty pGBKT7 vector were transformed into the yeast cell AH109, respectively. After they were cultured respectively in YPDA liquid medium and nutrition-deficient culture medium, their toxicity and transcriptional activation were tested by both the phenotype assay and the color assay. The bait plasmid HPV18 E6 was successfully obtained. After being cultured in YPDA liquid medium for 16h, the A (600 nm) values of two yeast fluids were 0.98+/-0.03 and 0.99+/-0.02, respectively. The recombinant pGBKT7-HPV18 E6 plasmid and empty pGBKT7 vector could grow to white colonies on SD/-Trp/X-alpha-gal plates, while no colony could survive on SD/-His/-Trp/X-alpha-gal, SD/-Ade/-Trp/X-alpha-gal plates, indicating that the bait plasmid pGBKT7-HPV18 E6 was constructed successfully and expressed correctly, and could not activate the transcription of reporter gene alone. The yeast two-hybrid GAL4 system 3 can be utilized to find HPV18 E6 interacting proteins.