Proliferative proteome induced by HPV 16E6 and NFX1-123 partnership in longitudinal keratinocyte cultures

Abstract

Human papillomaviruses (HPVs) cause cervical, anogenital, and oropharyngeal cancers. Despite the availability of preventive HPV vaccines, their poor uptake leaves individuals at risk for these cancers, many of which remain common globally and others that are increasing domestically. The HPV 16 E6 (16E6) protein plays a significant role in inducing and maintaining cellular transformation of its infected host cell; however, 16E6 itself has no enzymatic activity and executes its functions through partnerships with host proteins. Previously, we demonstrated that 16E6 binds to the host protein NFX1-123, and NFX1-123 expression is increased in HPV 16-positive cervical cancer cell lines and primary cancers compared to normal tissues. In this study, we quantify growth patterns of 16E6-expressing keratinocytes with endogenous or overexpressed NFX1-123 (16E6/vec and 16E6/FN123, respectively) levels and interrogate proteome expression changes early and late in longitudinal growth cultures. Early-passage 16E6/vec and 16E6/FN123 cells showed similar growth rates; however, late-passage 16E6/FN123 cells had accelerated growth, greater population doublings, increased telomerase activity, and a dysplastic phenotype when compared to 16E6/vec cells. Matching this, mass spectrometry revealed only 22 differentially expressed proteins at early passage; meanwhile, late-passaged cells had 827 differentially expressed proteins among 16E6/FN123 and 16E6/vec cells. In that, DNA maintenance and repair, proteins, namely, MCM2 and MCM4, were highly expressed in the 16E6/FN123 compared to 16E6/vec cells. These findings indicate that the 16E6 and NFX1-123 partnership, especially with sustained higher levels of NFX1-123, alters the longitudinal cellular environment in a manner that may initiate a preneoplastic phenotype. Importance: The high-risk HPV 16E6 protein plays a significant role in inducing and maintaining cellular transformation of its infected host cell; however, 16E6 has no enzymatic activity and carries out most of its functions through partnerships with host endogenous proteins, one being NFX1-123. That NFX1-123 expression is increased in HPV 16-positive cervical cancer and primary cancers compared to normal tissues, and NFX1-123 binds directly to 16E6. This study leverages proteomics to reinforce the synergistic actions of HPV16E6 and NFX1-123 and identifies cellular pathways impacted by this protein partnership over time. These findings encourage further investigation of NFX1-123 as a potential therapeutic target of HPV 16-positive tissues.