Commensal papillomavirus immunity preserves the homeostasis of highly mutated normal skin

Current and Emerging Insights into the Causes, Immunopathogenesis, and Treatment of Cutaneous Squamous Cell Carcinoma

The increasing incidence of cutaneous squamous cell carcinoma (cSCC), together with the ominous risks of metastasis and recurrence, underscores the importance of identifying novel therapies and validated biomarkers to augment patient management, particularly in the context of well-established and advanced disease. Following a brief overview of the well-recognized epidemiology, clinical features, and diagnosis of cSCC, the current review is focused on risk factors, most prominently excessive exposure to ultraviolet radiation (UVR) as a cause of persistent, pro-tumorigenic mutagenesis, and immune suppression. The next phase of the review encompasses an evaluation of the search for key driver mutations in the pathogenesis of cSCC, including the role of these and other mutations in the formation of immunologically reactive neoepitopes. With respect to additional mechanisms of tumorigenesis, immune evasion is prioritized, specifically the involvement of cell-free and infiltrating cellular mediators of immune suppression. Prominent amongst the former are the cytokine, transforming growth factor-β1 (TGF-β1), the prostanoid, prostaglandin E2, and the emerging immune suppressive nucleoside adenosine. In the case of the latter, tumor-infiltrating and circulating regulatory T cells have been implicated as being key players. The final sections of the review are focused on an update of the immunotherapy of established and advanced disease, as well as on the search for novel, reliable lesional and systemic biomarkers with the potential to guide patient management.

Inciting commensal human papillomavirus immunity to combat cancer

The incidence of squamous cell carcinoma (SCC) is rising, especially in immunosuppressed individuals, highlighting the need for new prevention strategies. Commensal human papillomaviruses (cHPVs) are associated with cutaneous SCC (cSCC) in immunosuppressed patients. Because of the intricate interactions between T cell immunity and cHPVs in virus-colonized tissues, we propose that enhancing T cell immunity against cHPVs through vaccination could suppress SCC.

The Role of HPV in the Development of Cutaneous Squamous Cell Carcinoma-Friend or Foe?

The incidence of cutaneous squamous cell carcinoma (cSCC) is increasing, with UV radiation being the main cause. Other risk factors are age, sex, skin type and immunosuppression. Human papillomaviruses (HPVs) are associated with benign and malignant skin tumours. In contrast to anogenital and oropharyngeal carcinomas, which are caused by alpha papillomaviruses, the HPV types associated with cSCC belong to the beta-HPV genus. These viruses infect the skin epithelium and are widespread in skin samples from healthy people. It is assumed that HPV amplifies the DNA damage caused by UV radiation and disrupts the repair mechanisms of the cells, without remaining permanently detectable in the tumour tissue, the so-called hit-and-run theory. The HPV status of tumours appears to have a positive influence on prognosis and response to therapy due to increased immune infiltration, in particular by tissue-resident memory T cells and activation of immune effector cells. This favours responses to immunotherapies such as PD-1/PD-L1 inhibitors, whereas immunosuppression may promote a pro-carcinogenic effect. In conclusion, the role of beta HPV in the development of cSCC appears to be closely associated with the immune status of the host. Depending on the immune status, beta HPV can play either a protective or a tumour-promoting role, and in view of the increasing incidence of skin cancer worldwide, enhancing the immune response against virus-infected keratinocytes, e.g., through HPV vaccination, could represent a promising approach for the prevention and therapy of squamous cell carcinomas.

Human Papillomavirus Vaccination and Actinic Keratosis Burden: The VAXAK Randomized Clinical Trial

Importance

The substantial morbidity and socioeconomic costs associated with actinic keratosis (AK) management represent major public health concerns. Anecdotal evidence suggests that human papillomavirus (HPV) vaccination may offer therapeutic and preventive effects against AK and keratinocyte carcinomas (KCs).

Objective

To investigate the effect of HPV vaccination on burden of disease in immunocompetent patients with high numbers of AK.

Design, Setting, and Participants

The VAXAK trial was a parallel-design, double-blind, randomized sham-controlled clinical trial with 12 months' follow-up. This single-center trial was conducted at the Department of Dermatology, Bispebjerg University Hospital in Copenhagen, Denmark, between May 2021 and June 2024. Eligible participants were immunocompetent adults with 15 or more clinical AK lesions in a 50 cm2 to 100 cm2 test area on the head, trunk, or extremities.

Interventions

Participants were randomized 1:1 to blinded, 9-valent alphapapillomavirus vaccine or sham vaccine (isotonic sodium chloride solution), each administered intramuscularly at 0, 2, and 6 months. Thick AKs (Olsen grade II-III) received cryotherapy at months 6 and 9; test areas were otherwise untreated during the study.

Main Outcomes and Measures

The preselected primary outcome was the percentage reduction in baseline AKs assessed 2, 6, 9, and 12 months after first vaccination. Secondary outcomes included total AK number, thick lesions, new AKs, and rate of incident KCs over 12 months.

Results

Participants were selected by consecutive sampling of 163 screened patients following exclusion of 93 individuals due to ineligibility or patients opting out. Among 70 enrolled participants (median [IQR] age, 75.50 [69.00-79.00] years; 47 [67%] male), 69 completed the study. Median (IQR) AK reductions were higher in the HPV-vaccinated vs sham group, shown consistently over the study period (month 2: 35% [25%-44%] vs 25% [18%-33%]; P = .03; month 6: 47% [33%-53%] vs 29% [16%-44%]; P = .01; month 9: 58% [37%-63%] vs 42% [33%-56%]; P = .09; month 12: 58% [47%-69%] vs 47% [32%-65%]; P = .05). Total AK numbers were correspondingly lower in the HPV-vaccinated group (median [IQR] at month 6: 14.00 [11.00-16.00] vs 17.00 [12.00-23.00]; P = .01; month 12: 10.00 [6.00-24.00] vs 16.00 [8.50-21.00]; P = .02). Coincidingly, fewer thick AKs were observed in the HPV-vaccinated group (median [IQR] at month 6: 5.00 [3.00-7.00] vs 6.50 [3.75-10.00]; P = .02; month 12: 3.00 [2.00-5.00] vs 5.00 [2.50-8.50]; P = .049). In contrast, no significant differences in rates of new AKs (1-2 AK[s] per month) or KC numbers overall or per participant were identified during the 12-month trial.

Conclusions and Relevance

In this randomized clinical trial, standard alphapapillomavirus vaccination was found to reduce AK burden in immunocompetent individuals with multiple lesions. HPV-targeted vaccines may be useful for management of AK, a chronic, relapsing disease and the most common precancer in fair-skinned populations.

Trial Registration

ClinicalTrials.gov Identifier: NCT05202860.