A Drosophila model of HPV16-induced cancer reveals conserved disease mechanism.

High-risk human papillomaviruses (HR-HPVs) cause almost all cervical cancers and a significant number of vaginal, vulvar, penile, anal, and oropharyngeal cancers. HPV16 and 18 are the most prevalent types among HR-HPVs and together cause more than 70% of all cervical cancers. Low vaccination rate and lack of molecularly-targeted therapeutics for primary therapy have led to a slow reduction in cervical cancer incidence and high mortality rate. Hence, creating new models of HPV-induced cancer that can facilitate understanding of the disease mechanism and identification of key cellular targets of HPV oncogenes are important for development of new interventions. Here in this study, we used the tissue-specific expression technique, Gal4-UAS, to establish the first Drosophila model of HPV16-induced cancer. Using this technique, we expressed HPV16 oncogenes E5, E6, E7 and the human E3 ligase (hUBE3A) specifically in the epithelia of Drosophila eye, which allows simple phenotype scoring without affecting the viability of the organism. We found that, as in human cells, hUBE3A is essential for cellular abnormalities caused by HPV16 oncogenes in flies. Several proteins targeted for degradation by HPV16 oncoproteins in human cells were also reduced in the Drosophila epithelial cells. Cell polarity and adhesion were compromised, resulting in impaired epithelial integrity. Cells did not differentiate to the specific cell types of ommatidia, but instead were transformed into neuron-like cells. These cells extended axon-like structures to connect to each other and exhibited malignant behavior, migrating away to distant sites. Our findings suggest that given the high conservation of genes and signaling pathways between humans and flies, the Drosophila model of HPV16- induced cancer could serve as an excellent model for understanding the disease mechanism and discovery of novel molecularly-targeted therapeutics.

Financial conflicts of interest during meetings of the cardiovascular and renal drugs advisory committee.

CONTEXT: The Cardiovascular and Renal Drugs Advisory Committee (CRDAC) of the Food and Drug Administration (FDA) reviews safety and efficacy data for cardiovascular and renal drugs, ultimately making recommendations to the Commissioner of Food and Drugs for approval. The Open Public Hearing segment of these meetings allows for patients, advocates, healthcare professionals, clinical trialists, and members of the public to provide testimony, which often results in expressing their preference for, or against, drug approval. Prior to providing testimony, the public speakers are highly encouraged to disclose any financial conflicts of interest (FCOIs) with the sponsor or other groups. Given the potential influence of these speakers on drug approval recommendations, we investigated the industry associations disclosed by public speakers in the Open Public Hearing section of the CRDAC meetings. Previous studies, such as one done by Lurie et al. indicated that positive testimony is tied to a higher likelihood of drug approval, and because drug companies provide financial compensation for speakers to provide testimony in general, we wanted to determine the likelihood with which speakers who have an FCOI provided a positive testimony vs. those without any FCOI. OBJECTIVES: The purpose is to evaluate whether public speakers with an FCOI are more likely to provide positive testimony regarding the drug in question during the CRDAC of the FDA between February 2009 and December 2019 through the use of publicly available transcripts. METHODS: Independent researchers investigated public transcripts and minutes of the CRDAC meetings with public speakers (n=20). We identified all speakers, along with characteristics such as an FCOI, and classified statements utilizing a pilot-tested Google form. The data collected were analyzed utilizing Stata. The speaker's testimony was then compared with their FCOI. An ordered logistic regression was performed utilizing the speaker's testimony regarding the drug as the dependent variable. RESULTS: Of the 88 speakers represented in our sample, 35 (35/88, 39.8%) disclosed an FCOI, most commonly regarding travel cost. Among speakers with an FCOI, 30 (30/35, 85.7%) spoke positively. Speakers with an FCOI were 4.96 times more likely to provide positive testimony (OR=4.96, 95% CI 1.67-14.78). Speakers with the disease were also more likely to provide positive testimony (OR=13.05, 95% CI 2.84-59.93). CONCLUSIONS: Public speakers often play a role during meetings, and they may also have an FCOI, most commonly related to travel expenses. Our study shows that speakers with an FCOI are more likely to provide positive testimony. Stipulations, such as requiring disclosure of FCOI and randomizing the selection process of speakers, can help ensure the integrity of the drug approval process.

Drosophila as a genetic model for studying pathogenic human viruses.

Viruses are infectious particles whose viability is dependent on the cells of living organisms, such as bacteria, plants, and animals. It is of great interest to discover how viruses function inside host cells in order to develop therapies to treat virally infected organisms. The fruit fly Drosophila melanogaster is an excellent model system for studying the molecular mechanisms of replication, amplification, and cellular consequences of human viruses. In this review, we describe the advantages of using Drosophila as a model system to study human viruses, and highlight how Drosophila has been used to provide unique insight into the gene function of several pathogenic viruses. We also propose possible directions for future research in this area.

Sqd interacts with the Drosophila retinoblastoma tumor suppressor Rbf.

The retinoblastoma tumor suppressor (RB) serves as a scaffold to coordinate binding of numerous proteins, including E2F and histone deacetylases, through its C-terminal domain. The amino-terminal half of RB has few known binding partners and its function is not well understood. We used the amino-terminal domain of the Drosophila retinoblastoma tumor suppressor Rbf (RbfN) to identify novel binding partners by immunoprecipitation coupled with mass spectrometry. Our experiment revealed that the RNA-binding protein Squid (Sqd) is a putative interacting partner of RbfN. Western blot confirmed that Sqd interacts with the amino-terminal domain of Rbf. We observed that Sqd colocalizes with RbfN in Drosophila salivary gland cells. We also show that double RNAi knockdown of Rbf and Sqd in the eye results in an extensive loss of eye bristles, suggesting that Rbf and Sqd function in a common pathway. We conclude from our studies that Rbf physically and genetically interacts with Sqd. We propose that the retinoblastoma tumor suppressor may play a novel role in RNA processing through interaction with RNA-binding proteins.

The RB/E2F pathway and regulation of RNA processing.

The retinoblastoma tumor suppressor protein (RB) is inactivated in a majority of cancers. RB restricts cell proliferation by inhibiting the E2F family of transcription factors. The current model for RB/E2F function describes its role in regulating transcription at gene promoters. Whether the RB or E2F proteins might play a role in gene expression beyond transcription initiation is not well known. This review describes evidence that points to a novel role for the RB/E2F network in the regulation of RNA processing, and we propose a model as a framework for future research. The elucidation of a novel role of RB in RNA processing will have a profound impact on our understanding of the role of this tumor suppressor family in cell and developmental biology.

The N-terminal domain of the Drosophila retinoblastoma protein Rbf1 interacts with ORC and associates with chromatin in an E2F independent manner.

BACKGROUND: The retinoblastoma (Rb) tumor suppressor protein can function as a DNA replication inhibitor as well as a transcription factor. Regulation of DNA replication may occur through interaction of Rb with the origin recognition complex (ORC). PRINCIPAL FINDINGS: We characterized the interaction of Drosophila Rb, Rbf1, with ORC. Using expression of proteins in Drosophila S2 cells, we found that an N-terminal Rbf1 fragment (amino acids 1-345) is sufficient for Rbf1 association with ORC but does not bind to dE2F1. We also found that the C-terminal half of Rbf1 (amino acids 345-845) interacts with ORC. We observed that the amino-terminal domain of Rbf1 localizes to chromatin in vivo and associates with chromosomal regions implicated in replication initiation, including colocalization with Orc2 and acetylated histone H4. CONCLUSIONS/SIGNIFICANCE: Our results suggest that Rbf1 can associate with ORC and chromatin through domains independent of the E2F binding site. We infer that Rbf1 may play a role in regulating replication directly through its association with ORC and/or chromatin factors other than E2F. Our data suggest an important role for retinoblastoma family proteins in cell proliferation and tumor suppression through interaction with the replication initiation machinery.