Folate Deficiency Facilitates Genomic Integration of Human Papillomavirus Type 16 DNA In Vivo in a Novel Mouse Model for Rapid Oncogenic Transformation of Human Keratinocytes

• Published in: The Journal of nutrition 2018-03, Vol.148 (3), p.389-400
• Main Authors: Xiao, Suhong, Tang, Ying-Sheng, Kusumanchi, Praveen, Stabler, Sally P, Zhang, Ying, Antony, Aśok C
• Format: Article
• Language: English
• Subjects: Animal models; Animals; Cancer; Carcinogenesis; Carcinogenesis - genetics; Carcinogens; Cells; Deoxyribonucleic acid; Diet; Disease Models, Animal; DNA; Epidemiology; Female; folate/vitamin B-12 nutrition; Folic acid; Folic Acid - administration & dosage; Folic Acid Deficiency - complications; Gene expression; Genetic transformation; Genome; Genomes; genomic integration; Genomics; Human papillomavirus; Human papillomavirus 16 - genetics; human papillomavirus type 16; Humans; immunodeficiency; Implantation; Integration; Keratinocytes; Keratinocytes - virology; Mice, Nude; mouse model; Neoplasms - etiology; Neoplasms - genetics; Neoplasms - virology; Nutrient deficiency; Nutrition; Nutritional Status; Oncogene Proteins, Viral - metabolism; oncogenes; organotypic rafts; Papillomavirus E7 Proteins - metabolism; Papillomavirus Infections - etiology; Papillomavirus Infections - virology; Proteins; Rafts; Repressor Proteins - metabolism; Surgery; Surgical implants; Three dimensional models; Tumors; Uterine Cervical Neoplasms; Virus Integration; Vitamin B
• ISSN: 0022-3166; 1541-6100
• DOI: 10.1093/jn/nxx060

Epidemiologic and in vitro studies suggest independent linkages between poor folate and/or vitamin B-12 nutrition, genomic human papillomavirus (HPV) type 16 viral integration, and cancer. However, there is no direct evidence in vivo to support the causative role of poor folate nutrition in HPV16 integration into the cellular genome. We tested the hypothesis that folate deficiency enables the integration of HPV16 into the genome of HPV16-harboring keratinocytes, and could thereby influence earlier transformation of these cells to cancer in an animal model. HPV16-harboring human keratinocytes [(HPV16)BC-1-Ep/SL] were differentiated into 3-dimensional HPV16-organotypic rafts under either folate-replete or folate-deficient conditions in vitro. These were then subcutaneously implanted in severely immunocompromised female Beige Nude XID (Hsd: NIHS-LystbgFoxn1nuBtkxid) mice (4–6 wk old, 16–18 g) fed either a folate-replete diet (1200 nmol folate/kg diet) or a progressively folate-deficient diet (600 or 400 nmol folate/kg diet) for 2 mo prior to raft-implantation surgery, and indefinitely thereafter. The tumors that subsequently developed were characterized for onset, pattern of growth, morphology, HPV16 oncogene expression, and HPV16-genomic integration. All HPV16-organotypic rafts developed in either folate-replete or physiologic low-folate media in vitro and subsequently implanted in folate-replete mice eventually transformed into aggressive malignancies within weeks. When compared to HPV16-high folate-organotypic raft-derived tumors from mice fed either a 1200 or 600 nmol folate/kg diet, those raft-derived cancers that developed in mice fed a 400 nmol folate/kg diet expressed significantly more HPV16 E6 (1.8-fold more) and E7 (2.8-fold more) oncogenic proteins (P = 0.001), and revealed significantly more HPV16-integration sites in genomic DNA (2-fold more), either directly into, or in the vicinity of, cellular genes (P