Ingenol mebutate‐mediated reduction of p53‐positive keratinocytes in skin cancerization field directly correlates with clinical response in patients with multiple actinic keratoses

Abstract

Background

UV radiation represents the main risk factor for Non Melanoma Skin Cancers (NMSC). Chronic UV exposure induces "p53 patches", i.e. clonal outgrowths of keratinocytes with high nuclear expression of mutated p53, which might progress to actinic keratosis (AK) and ultimately squamous cell carcinomas (SCC).

Aims

Analysis of Ingenol mebutate gel (150 and 500 mcg/g) effects in the reduction of "p53 patches" inside skin cancerization field (CF) in patients with multiple AKs of face/scalp or trunk/extremities, in order to investigate if the expected reduction of p53⁺ keratinocytes might have a direct role in the long‐term AK reduction in treated areas.

Results

We enrolled n=10 patients, treated with Ingenol mebutate and evaluated at 2 and 6 months after treatment. We observed clinical responses in the majority of patients (n=7), with AK reduction or complete clearance (n=6 and n=1, respectively). Notably, two patients did not respond to the treatment and in one patient, after initial partial response, new lesion were recorded. In untreated skin CF samples (n=3), we observed numerous p53⁺ keratinocytes, similar to those observed in invasive SCC samples (53.56±8.79 and 74.34±22.05, respectively; p=0.2). After treatment, we observed a variable p53⁺ keratinocytes reduction in CF samples at 2 months (24.67±31.19; p=0.19). Importantly, the amount of p53⁺ keratinocytes strongly and directly correlated with AK number (R² =0.81).

Conclusion

Untreated skin CF expresses high level of p53⁺ keratinocytes as invasive SCC. Ingenol mebutate is able to reduce p53⁺ keratinocytes with variable efficacy, this reduction degree directly correlating with clinical efficacy.

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