Topical AC-11 Abates While Applied Actinic Keratoses and Early Squamous Cell Cancers in Hairless Mice Exposed to Ultraviolet A (UVA) Radiation

AC-11 is an aqueous extract of the botanical, Uncaria tomentosa, which has a variety of effects that enhance DNA repair and down regulate inflammation. AC-11 is essentially free of oxindole alkaloids (< 0.05%, w/w) but contains more than 8% Carboxy Alkyl Esters (CAEs) as their active ingredients. Three groups of 10 outbred SK-1 hairless or SK-II hairless strains of mice each were treated with AC-11 at 0.5%, 1.5%, and 3.0% in a non-irritating, dye-free, perfume-free, and fragrance-free vanishing cream vehicle. Ten mice used vehicle only and 10 were untreated. Each concentration of AC-11 and was applied daily to the backs of the mice prior to exposure to a 1,600-watt solar simulator used in this work (Solar Light Co. Philadelphia, PA) emitting (mainly Ultraviolet A (UVA) and B (UVB) radiation) duration of the experimental period with UVB wavelengths was filtered out with a 1.0 cm Schott WG 345 filter. AC-11 with peak absorption at 200nm does act as a sun block. We tested for and focused on clinical appearance of mice and histological appearance of tumors in mice rather than metrics of radiation generated inflammation. Tumor progression scores were assigned as follows: 4+ = extensive tumor development; 3+ = early malignancies (raised palpable plaques) (early squamous cell cancers) 2+ = firm scaling, palpable keratosis (actinic keratoses); 1+ = light scaling with erythema. Following a total cumulative dose of 738 J/cm2 , 85.7% all of the irradiated control animals, which did not receive AC–11 had precancerous actinic keratosis (AK)-type lesions (2+) (64.3% versus 42.9%) or early squamous cell carcinoma (SCC) (3+) (21.4% vs. 4.8%), in comparison with 47.7 % of AC-11-treated animals. There were no significant differences between the AC–11 groups. Three months after cessation of exposure to UVA radiation, the lesions in all but three of the 14 animals which were treated with AC-11 that were still evaluable irradiated with UVA radiation progressed to papillomas and frank squamous cell carcinomas (+4 responses). AC-11 retarded, but did not stop, carcinogenesis progression. It is possible that if AC-11 was continuously applied tumors would not have in mice treated with AC-11 for a limited period. While we do not know how AC-11 exerts its DNA repair and antiinflammatory effects, AC-11 is therapeutic for the treatment at the time of development of actinic keratoses and squamous cell carcinomas in mice and by extension humans. Without the constant presence of AC-11 these protective effects do not occur.