Houston, Texas, USA : Preclinical experiments by University of Alabama at Birmingham researchers suggest the cancer drugs vorinostat, belinostat and panobinostat might be repurposed to treat infections caused by human papillomaviruses, or HPVs.
HPV infections caused an estimated 266,000 deaths from cervical cancer worldwide in 2012, according to the World Health Organization. Routine screening by Pap smears or HPV DNA tests has reduced death rates in developed countries compared to less developed regions of the globe. Still, an estimated 12,200 United States women are diagnosed with cervical cancer each year.
Highly efficacious vaccines against HPV infection exist — including the recently approved Gardasil 9, which immunizes against nine genotypes of HPV known to cause cervical, vulvar, vaginal and anal cancers, and genital warts. But the vaccine needs to be given before a person becomes sexually active, since it has no therapeutic efficacy against existing HPV infections.
“Safe, effective and inexpensive therapeutic agents are urgently needed,” said N. Sanjib Banerjee, Ph.D., assistant professor of Biochemistry and Molecular Genetics at UAB and lead author of the vorinostat study.
Epithelium of anogenital sites — the cervix, penis and anus — or epithelium of the mouth and throat are sites of HPV infection. But HPVs cannot be propagated in conventional cell culture, hampering the investigation into their pathogenic effects. The laboratory of Louise Chow, Ph.D., and Thomas Broker, Ph.D., in the UAB Department Biochemistry and Molecular Genetics has investigated HPV-host interactions for decades. They discovered that the productive program of HPV depends on differentiation of the epithelium into a full-thickness, squamous epithelium. Furthermore, HPV reactivates host DNA replication in these differentiated cells, such that the replication proteins and substrates become available to support viral DNA amplification.
The Chow and Broker lab re-produced a fully differentiated human squamous epithelium by culturing primary human keratinocytes at an air-media interphase for two to three weeks, a growth they call raft culture. In 2009, their lab developed a breakthrough model for a raft culture of HPV-18-infected primary human keratinocytes, allowing a robust amplification of HPV-18 DNA and production of infective viral progeny. This productive raft culture is an ideal model for preclinical investigation of potential anti-HPV agents.
Banerjee and colleagues hypothesized that inhibitors of histone deacetylases, or HDACs, would inhibit HPV DNA amplification because of their known mechanism of disrupting chromosomal DNA replication. Chromosomal replication requires HDAC alterations of histone proteins, the proteins that act like spools that wind DNA to help package and condense chromosomes and the viral genome. Vorinostat inhibits many HDACs, so it might interrupt not only chromosomal replication but also viral DNA replication.
Using the HPV-18 model raft cultures, the researchers found that vorinostat effectively inhibited HPV-18 DNA amplification and virus production. Importantly, vorinostat also induced the programmed cell death called apoptosis in a fraction of the differentiated cells. Cell death could be attributable to DNA breakage when chromosomal DNA replication was interrupted. Similar results were obtained with two additional HDAC inhibitors, belinostat and panobinostat. In contrast, the differentiated cells of uninfected raft cultures, which do not replicate their DNA, were thus largely spared in the presence of the inhibitors.
The UAB team also examined how vorinostat affected levels and functions of viral oncoproteins, and they described the mechanisms that led to programmed cell death in HPV-18-infected cultures. “On the basis of these detailed studies,” Banerjee said, “we suggest that HDAC inhibitors are promising compounds for treating benign HPV infections, abrogating progeny production and hence interrupting infectious transmission.”
The UAB team also reported that vorinostat caused extensive cell death in raft cultures of dysplastic and cancer cell lines harboring HPV-16. HPV-16 and HPV-18 are the most prevalent, high-risk HPVs responsible for causing anogenital and oropharyngeal cancers. “But further investigation would be required to verify that these agents could also be useful in treating HPV associated dysplasias and cancers,” Banerjee said.
Authors of the paper, “Vorinostat, a pan-HDAC inhibitor, abrogates productive HPV-18 DNA amplification,” published in Proceedings of the National Academy of Sciences, are Banerjee, Chow, Broker and Dianne W. Moore, UAB Department of Biochemistry and Molecular Genetics.
Support came from National Institutes of Health grant CA83679, UAB Comprehensive Cancer Center/HIV-Associated Malignancy Pilot Grant 316851, UAB Comprehensive Cancer Center Pilot Grant 5P30CA013148-43 and UAB Bridge Funding.
At UAB, Chow holds the Anderson Family Chair in Medical Education, Research and Patient Care in the School of Medicine.
Citation: N. Sanjib Banerjee et al, Vorinostat, a pan-HDAC inhibitor, abrogates productive HPV-18 DNA amplification, Proceedings of the National Academy of Sciences. DOI: 10.1073/pnas.1801156115
Related study found Vorinostat renders dormant HIV infection vulnerable to clearance
Vorinostat renders dormant HIV infection vulnerable to clearance
The ability for HIV to hide in the body in a dormant state makes curing the 40 million people living with the virus a challenge. Researchers at the University of North Carolina at Chapel Hill have shown the drug Vorinostat reverses this latency, causing resting CD4 T-cells to express HIV. The investigators have developed an assay that detects antigen production and includes immune effectors capable of clearing the virus. These results were published in EBioMedicine.
Vorinostat produces a window of vulnerability in the HIV reservoir by triggering viral antigen production. The team developed the latency clearance assay (LCA) to measure the amount of antigen activity Vorinostat produces. The assay also includes immune effectors capable of clearing the cells expressing the viral antigen.
“Measuring a latency reversing agent’s ability to induce relevant HIV production is technically challenging,” said Julia Sung, M.D., the study’s lead author and an assistant professor of medicine in the UNC Division of Infectious Diseases. “Using a latency clearance assay, we have detected the ability of Vorinostat, a latency reversing agent under clinical investigation, to induce recognizable levels of HIV protein on the cell surface allowing for subsequent clearance of infected cells.”
The optimal combination of latency-reversing agents and clearance strategies will be needed to cure HIV. The team says their assay can be used to evaluate these combinations in future studies.
Citation: Julia A. Sung et al. Vorinostat Renders the Replication-Competent Latent Reservoir of Human Immunodeficiency Virus (HIV) Vulnerable to Clearance by CD8 T Cells, EBioMedicine. DOI: 10.1016/j.ebiom.2017.07.019
A separate study found that Vorinostat advances the ability to expose latent HIV
Vorinostat advances the ability to expose latent HIV
Exposing hidden HIV reservoirs so that they can be cleared is a strategy being tested in efforts to develop therapies to cure the nearly 40 million people worldwide living with HIV. Researchers at the University of North Carolina at Chapel Hill have shown that interval dosing of the drug Vorinostat reverses HIV latency and is well-tolerated in people living with HIV. However, while Vorinostat makes latent HIV easier to detect, it does not clear or deplete infection, meaning additional advances will be needed to achieve a cure. These results were published in the Journal of Clinical Investigation on July 17.
The team studied Vorinostat in 16 patients living with HIV whose viral load was controlled through standard antiviral therapy. Doses of Vorinostat were administered at 48 or 72-hour intervals. The team found that HIV could be more easily detected within latently infected CD4+ T cells when Vorinostat was administered once every three days, even though control of viral load in the blood was maintained.
“We showed that a single dose of Vorinostat could expose the hidden virus several years ago, but it has taken two studies over the last five years to define the proper interval dosing strategy to use Vorinostat safely and effectively,” said Nancie Archin Ph.D., lead author of this study and an assistant professor in the Division of Infectious Diseases at UNC. “Now we can attempt to chip away the viral reservoir.”
Over a month of treatment with Vorinostat few side effects and no serious toxicities were seen, but depletion of latent infection was not found. The team believes pairing a latency reversing agent, like Vorinostat, with an antiviral immune therapy, such as a vaccine or an antibody capable of recognizing and clearing the latent cells, will be needed to achieve a cure.
“We have now been able to begin two small, intensive studies pairing Vorinostat with an anti-HIV vaccine produced by Argos Therapeutics, or with an infusion of antiviral immune cells prepared by Cath Bollard’s laboratory at Children’s National Medical Center, in an attempt to test combined approaches to clearing HIV infection,” said David Margolis, M.D., director of the UNC HIV Cure Center at the UNC Institute for Global Health & Infectious Diseases. “We do not expect immediate success, but hope to make progress towards the goal of developing treatments that someday might clear HIV infection.”