Topical Protease Inhibitor Decreases Anal Carcinogenesis in a Transgenic Mouse Model of HPV Anal Disease

Anal cancer is a major health problem. This study seeks to determine if the topical protease inhibitor Saquinavir (SQV), is effective at the prevention of anal cancer in transgenic mice with established anal dysplasia. K14E6/E7 mice were entered into the study when the majority spontaneously developed high-grade anal dysplasia. To ensure carcinoma development, a subset of the mice was treated with a topical carcinogen: 7,12-Dimethylbenz[a]anthracene (DMBA). Treatment groups included: no treatment, DMBA only, and topical SQV with/without DMBA. After 20 weeks of treatment, anal tissue was harvested and evaluated histologically. SQV was quantified in the blood and anal tissue, and tissue samples underwent analysis for E6, E7, p53, and pRb. There was minimal systemic absorption of SQV in the sera despite high tissue concentrations. There were no differences in tumor-free survival between SQV-treated and respective control groups but there was a lower grade of histological disease in the mice treated with SQV compared to those untreated. Changes in E6 and E7 levels with SQV treatment suggest that SQV may function independently of E6 and E7. Topical SQV decreased histological disease progression in HPV transgenic mice with or without DMBA treatment without local side effects or significant systemic absorption.

Anal Cancer Prevention Through the Topical Use of Single or Dual PI3K/mTOR Inhibitors

INTRODUCTION

Anal dysplasia and anal cancer are major health problems. This study seeks to determine if inhibition of mTOR and/or PI3K pathways is effective at anal cancer prevention in mice with/without established precancerous lesions of the anus (anal dysplasia).

METHODS

K14E6/E7 mice were entered into the study at 5 wk, 15 wk, or 25 wk of age. Mice were treated with a topical carcinogen, 7,12-Dimethylbenz[a]anthracene (DMBA), which ensures carcinoma development within 20 wk. Treatment groups included: no treatment, DMBA only, topical Pictilisib (PI3K inhibitor) with/without DMBA, topical Sapanisertib (mTOR inhibitor) with/without DMBA, and topical Samotolisib (dual PI3K/mTOR inhibitor) with/without DMBA. Mice underwent weekly observations for anal tumor development (tumor-free survival). After 20 wk of treatment, anal tissue was harvested and evaluated histologically for squamous cell carcinoma (SqCC).

RESULTS

All topical treatments in conjunction with DMBA increased tumor-free survival in mice that started treatment at 15 wk of age when compared to DMBA-only treatment, except for Pictilisib + DMBA in males. Topical Sapanisertib increased tumor-free survival in mice regardless of starting treatment age. When examining tissue for microscopic evidence of SqCC, only topical Samotolisib in males decreased SqCC in the 15 wk starting mice.

CONCLUSIONS

Sapanisertib, the mTOR inhibitor, had the greatest effect, in terms of increasing tumor-free survival, regardless of starting time point or sex. Unlike the other treatments, Samotolisib, the dual PI3K/mTOR inhibitor, decreased microscopic evidence of SqCC when starting treatment at 15 wk of age but only in male mice.

The use of a topical protease inhibitor, Saquinavir, to alleviate mouse papillomavirus-mediated anal disease

Select protease inhibitors (PI) have been found to be effective in decreasing human papillomavirus oncoprotein expression. This study evaluated whether the topical PI, Saquinavir (SQV), promotes viral clearance in an infectious mouse model with Mus musculus papillomavirus 1 (MmuPV1). NOD scid gamma (NSG) mice were anally infected with ∼4 × 10⁸ viral genome equivalents of MmuPV1 and 120 days post-infection (when majority have high-grade anal dysplasia), began topical treatments: control (mock), 7,12-dimethylbenz(a)anthracene (DMBA) only, once weekly to promote carcinogenesis, 1% SQV only, daily (Monday - Friday), and SQV + DMBA. Viral MmuPV1 load was analyzed from anal lavages pre and post-treatment. Anal tissue was harvested, processed, and evaluated for drug absorption, grade of anal disease, and anal viral RNA. Results suggest that topical SQV promotes decreased viral shedding in female mice treated with SQV.

Systemic Delivery of a Dual PI3K/mTOR Inhibitor More Effective than Topical Delivery in Preventing Anal Carcinogenesis in an HPV Transgenic Mouse Model

Introduction

Anal dysplasia is a growing health concern that over time can result in squamous cell carcinoma (SqCC) of the anus. In this study, we compare a topical versus systemic (oral) administration of LY3023414, a dual PI3K/mTOR inhibitor, to prevent anal carcinogenesis in a Human Papillomavirus (HPV) mouse model of anal cancer.

Materials and Methods

K14E6/E7 transgenic mice were used to model HPV-induced anal carcinogenesis. Mice with varying starting anal histologies (normal histology, low-grade, and high-grade anal dysplasia) were treated topically at the anus or systemically via oral gavage with LY3023414 with or without topical carcinogen for 20 weeks. Mice were monitored for overt anal tumor development and anal tissue was assessed for histology and markers of PI3K and mTOR activity (pAKT and pS6, respectively).

Results

LY3023414 treatment, regardless of the mode of delivery, significantly decreased overt tumor development in mice starting with normal histology and low-grade anal dysplasia. Systemic LY3023414 treatment was more effective in delaying tumor onset than topical treatment. Mice treated with systemic LY3023414 had significantly reduced rates of anal SqCC when starting with normal and low-grade anal dysplasia compared to topical treatment. Topical treatment was only effective in reducing SqCC in the setting of low-grade dysplasia. LY3023414 inhibition of pAKT and pS6 expression varied with starting histology. Neither treatment mode was effective in the setting of high-grade anal dysplasia.

Conclusion

Systemic LY3023414 treatment was more effective than topical application in delaying the progression of normal anal histology and low-grade dysplasia to anal cancer in HPV-associated mice.