The logic behind targeting E5 and E6 rests on their central position in HPV-mediated malignant transformation. According to the review, these oncoproteins collectively promote cell proliferation, immune evasion, resistance to apoptosis, and genomic instability, the four pillars on which a virus-infected cell can progress toward cancer. E5 contributes to tumor progression by modulating growth factor signaling and promoting cell survival, effectively creating a cellular environment in which abnormal proliferation is favored. E6, by contrast, plays the more notorious role: it drives malignant transformation primarily by tagging the tumor suppressor p53 for degradation, thereby removing one of the cell’s most important safeguards against uncontrolled division and DNA damage.

The significance of p53 degradation cannot be overstated. In normal cells, p53 acts as a guardian of the genome, halting the cell cycle when DNA damage is detected and triggering programmed cell death when the damage is irreparable. When HPV16 E6 orchestrates the destruction of p53, infected cells lose this critical checkpoint and accumulate mutations with impunity. Because this mechanism is virus-encoded rather than a mutation in the host genome itself, it presents an attractive therapeutic window: a treatment that silences E6 could, in principle, allow p53 function to be restored in tumor cells while leaving normal cells untouched. This selectivity is precisely what makes HPV oncogenes such compelling drug targets compared with conventional cytotoxic approaches.

E5, though less studied than E6, is far from a bystander in the carcinogenic process. The review emphasizes that E5’s modulation of growth factor signaling and its promotion of cell survival help sustain tumor growth and progression. By interfering with normal growth regulatory pathways, E5 helps create conditions in which cells proliferate even in the absence of appropriate external signals. It also contributes to the ability of infected cells to evade immune surveillance, a hallmark of cancer that allows premalignant lesions to persist and progress undetected. A therapeutic strategy that addresses both E5 and E6 simultaneously could therefore attack the disease from multiple angles at once, undermining both the survival signaling and the tumor suppressor evasion that sustain the malignancy.

The technological core of the review concerns two families of gene-silencing tools. The first is built on small interfering RNAs, or siRNAs, short double-stranded RNA molecules that exploit a natural cellular pathway to degrade messenger RNA in a sequence-specific manner. When designed to match sequences within the E5 or E6 transcripts, siRNAs can direct the cellular RNA interference machinery to destroy the viral messages before they are translated into protein, effectively silencing the oncogenes at the post-transcriptional level. The second family comprises CRISPR/Cas-based genome-editing systems, which go a step further by introducing targeted disruptions into the viral DNA itself, potentially knocking out the oncogene sequences permanently rather than merely dampening their expression.

According to the review, both approaches have demonstrated significant potential in preclinical studies. Suppressing E5 and E6 expression has been shown to restore tumor suppressor functions, induce apoptosis in cancer cells, and enhance the sensitivity of those cells to conventional therapies such as chemotherapy and radiotherapy. This last point carries particular clinical weight. Cervical cancer treatment currently relies on surgery, radiation, and cytotoxic drugs, modalities that are effective but blunt and often accompanied by substantial toxicity. If gene-silencing can sensitize tumor cells to existing treatments, lower doses might achieve the same effect, reducing side effects while improving outcomes. The restoration of p53-mediated apoptosis following E6 silencing offers a mechanistically coherent explanation for these observations: cells that regain the ability to die on cue are inherently more vulnerable to DNA-damaging therapies.

The appeal of targeting viral oncogenes rather than host genes also extends to specificity. Because E5 and E6 exist only in HPV-infected cells, therapies directed against their transcripts or coding sequences should, in theory, spare uninfected tissue entirely. This stands in sharp contrast to most anticancer agents, which discriminate between tumor and normal cells only imperfectly. The review frames this viral specificity as a foundational advantage of the gene-silencing paradigm in HPV-driven cancers, one that aligns with the broader movement toward precision oncology in which molecular definitions of disease replace anatomical ones.

Yet the path from laboratory promise to clinical reality is far from straightforward, and the authors devote considerable attention to the challenges that remain. Delivering siRNAs or CRISPR components efficiently and selectively to cervical tumor cells is a formidable obstacle; RNA molecules are rapidly degraded in the bloodstream and do not cross cell membranes unaided, while gene-editing systems require delivery vectors whose safety and tropism must be carefully controlled. Off-target effects, in which silencing or editing tools act on unintended sequences, represent another safety concern that must be rigorously addressed. The review also highlights the inherent limitations of current preclinical models, which may not fully recapitulate the complexity of human cervical carcinogenesis, and notes that therapeutic limitations and unresolved questions still separate these experimental approaches from approved treatments.

Despite these hurdles, the therapeutic perspectives outlined in the review are notably optimistic. The authors position targeted molecular approaches against HPV oncogenes as a frontier for both the prevention and treatment of cervical cancer, complementing rather than replacing existing interventions. Prophylactic HPV vaccines have transformed prevention efforts worldwide, but they do not treat established infections or existing lesions, and a large population of women worldwide carries persistent infections that vaccines cannot address. Therapeutic gene silencing fills precisely this gap, offering a potential intervention for individuals whose disease is already established. The combination of vaccination for prevention and oncogene-directed silencing for treatment could, in principle, cover the entire spectrum of HPV-associated disease.

The review, which was supported by the Infectious and Tropical Diseases Research Center at Tabriz University of Medical Sciences, ultimately serves as both a status report and a roadmap. It consolidates the mechanistic case that E5 and E6 are pivotal to HPV16-driven carcinogenesis, catalogs the preclinical evidence that siRNA and CRISPR/Cas systems can suppress their expression with meaningful biological consequences, and candidly maps the delivery, safety, and translational challenges that stand between the laboratory and the clinic. As gene-silencing technologies mature and delivery platforms improve, the prospect of a therapy that disarms the very genes the virus uses to cause cancer moves from theoretical appeal toward practical possibility, offering hope for a future in which cervical cancer is not only preventable by vaccine but also treatable at its viral roots.

Subject of Research: Gene-silencing strategies targeting HPV16 E5 and E6 oncoproteins for cervical cancer therapy

Article Title: Targeting HPV16 E5 and E6 through gene-silencing approaches: mechanisms, preclinical evidence, and therapeutic perspectives

Article References: Ravanlo, Z. Z., Gholami, S., Rahimi, S. B., Shamekh, A., Adli, A. H., & Baghi, H. B. (2026). Targeting HPV16 E5 and E6 through gene-silencing approaches: mechanisms, preclinical evidence, and therapeutic perspectives. Virology Journal. https://doi.org/10.1186/s12985-026-03321-z

Image Credits: AI Generated

DOI: 10.1186/s12985-026-03321-z

Keywords: HPV16, E5 oncoprotein, E6 oncoprotein, gene silencing, siRNA, CRISPR/Cas9, cervical cancer, p53, oncogenes, virology, RNA interference, gene therapy