Why Is Wnt/β-Catenin Not Yet Targeted in Routine Cancer Care?

Despite significant progress in cancer prevention, screening, and treatment, the still limited number of therapeutic options is an obstacle towards increasing the cancer cure rate. In recent years, many efforts were put forth to develop therapeutics that selectively target different components of the oncogenic Wnt/β-catenin signaling pathway. These include small molecule inhibitors, antibodies, and more recently, gene-based approaches. Although some of them showed promising outcomes in clinical trials, the Wnt/β-catenin pathway is still not targeted in routine clinical practice for cancer management. As for most anticancer treatments, a critical limitation to the use of Wnt/β-catenin inhibitors is their therapeutic index, i.e., the difficulty of combining effective anticancer activity with acceptable toxicity. Protecting healthy tissues from the effects of Wnt/β-catenin inhibitors is a major issue due to the vital role of the Wnt/β-catenin signaling pathway in adult tissue homeostasis and regeneration. In this review, we provide an up-to-date summary of clinical trials on Wnt/β-catenin pathway inhibitors, examine their anti-tumor activity and associated adverse events, and explore strategies under development to improve the benefit/risk profile of this therapeutic approach.

Immunothrombotic Mechanisms Induced by Ingenol Mebutate Lead to Rapid Necrosis and Clearance of Anogenital Warts

Ingenol mebutate (IM) is highly effective in the treatment of human papillomavirus (HPV)-induced anogenital warts (AGW) leading to fast ablation within hours. However, the exact mode of action is still largely unknown. We performed dermoscopy, in vivo confocal microscopy (CLM), histology, immunohistochemistry, and immunofluorescence to gain insights in mechanisms of IM treatment in AGW. In addition, we used in vitro assays (ELISA, HPV-transfection models) to further investigate in vivo findings. IM treatment leads to a strong recruitment of neutrophils with thrombosis of small skin vessels within 8 h, in a sense of immunothrombosis. In vivo and in vitro analyses showed that IM supports a prothrombotic environment by endothelial cell activation and von Willebrand factor (VWF) secretion, in addition to induction of neutrophil extracellular traps (NETosis). IM superinduces CXCL8/IL-8 expression in HPV-E6/E7 transfected HaCaT cells when compared to non-infected keratinocytes. Rapid ablation of warts after IM treatment can be well explained by the observed immunothrombosis. This new mechanism has so far only been observed in HPV-induced lesions and is completely different from the mechanisms we see in the treatment of transformed keratinocytes in actinic keratosis. Our initial findings indicate an HPV-specific effect, which could be also of interest for the treatment of other HPV-induced lesions. Larger studies are now needed to further investigate the potential of IM in different HPV tumors.

Ingenol Mebutate Gel 0.05% in the Treatment of Anogenital Warts: A Prospective Controlled Trial Comparing It With Topical Podophyllin Solution 25

BACKGROUND

Anogenital warts (AGWs) are a common therapeutic challenge. All therapies are associated with burning, pain, and frustrating high rate of recurrence. The search for a new alternative continues. Recently, a diterpene ester extracted from the Euphorbia peplus plant (ingenol mebutate [IM]) has been shown to possess activity against AGWs.

OBJECTIVE

This study aimed to compare and evaluate the therapeutic efficacy and safety of topical 0.05% ingenol gel with another herbal extract medication (topical 25% podophyllin solution) in treatment of AGWs.

METHODS

This was a comparative single blinded nonrandomized, 2-arm trial of ingenol 0.05% gel versus podophyllin solution 25% administered up to 6 times to patients with AGWs. To evaluate the therapeutic efficacy, the complete clearance rate and recurrence rate were assessed 1 and 12 weeks after last treatment, respectively. Safety was assessed by occurrence and severity of pain and local skin reaction (LSR).

RESULTS

Of 31 and 36 patients in the IM group and podophyllin group who completed the study, initial complete resolution was observed in 20 (64.5%) and 14 (38.9%) patients, respectively (P = 0.03). The initial clearance was faster in the IM group (2.00 ± 0.91 weeks) compared with the podophyllin group (4.21 ± 1.05 weeks, P = 0.00). After 3 months, recurrence was seen in 13 (65.0%) of 20 patients in the IM group and 6 (42.8%) of 14 in the podophyllin group (P = 0.20). The number of patients with complete resolution after 3 months was not different between the 2 groups (7/31 in the IM group and 8/36 in the podophyllin group, P = 0.97). The mean ± SD severity scores for LSR and pain in the IM group were 6.65 ± 1.76 and 6.13 ± 2.57, respectively, which was significantly higher than their scores (3.39 ± 1.57 and 2.58 ± 1.38) in the podophyllin group (P = 0.00).

CONCLUSION

Ingenol mebutate 0.05% gel is effective as podophyllin 25% solution in treating AGWs, with further benefit of being much more rapid. However, high recurrence rate, sever pain, and LSR limit its use.

Ingenol mebutate for the management of cryotherapy-resistant anogenital warts

Ingenol mebutate (IM), as an active compound, is derived from the sap of the Euphorbia peplus, which is an FDA-approved plant for the treatment of actinic keratosis. Some reports have demonstrated that the IM gel 0.05% is safe and effective in the treatment of external anogenital warts (AGWs) but the efficacy of the drug on the recalcitrant AGWs is not clear. This article assesses the efficacy and safety of the IM gel 0.05% for cryotherapy -resistant AGWs. Totally, 15 cryotherapy-resistant patients with AGWs (including 8 men and 7 women) and a mean age of 34 years old (age range of 23-50 years old) were enrolled in this study. IM gel 0.05% was applied carefully on the AGWs every two weeks for a maximum of three cycles. The complete clearance rate and recurrence rate were assessed 1 week and 3 months after the last treatment, respectively. Safety was assessed by the occurrence of local skin reaction and the severity of pain was evaluated using the 10-point Visual Analogue Scale. Initially, the AGWs were cleared completely in 10 (66%) patients while 4 (40%) and all of (100%) the patients experienced a recurrence in the 3- and 12-months follow-ups, respectively. All the 15 patients experienced some degrees of pain and local adverse reactions. The mean score of the reported pain was equal to 5.87 ± 2.39. The use of IM gel 0.05% in the treatment of the difficult-to-treat cases of AGWs is associated with a high recurrence rate despite the initial rapid and effective clearance of the lesions. Also, the high level of local adverse reactions and severe pain are other prohibitive factors in the treatment of recalcitrant AGWs with the IM.

Successful treatment of condylomata acuminata at the urethral meatus with high-dose ingenol mebutate gel: Report of two cases

Condylomata acuminata (CA), or anogenital warts, is the most common sexually transmitted infection. Treatments for CA generally have suboptimal recurrence rates, which results in a need for repeated treatments and adds to the already negative impact on the patients’ quality of life. CA can present at the urethral meatus, which is a particularly challenging anatomic location from a therapeutic perspective. We report two cases of CA at the urethral meatus successfully treated with topical application of high-dose ingenol mebutate gel.

Penile warts: an update on their evaluation and management

Background

Penile warts are the most common sexually transmitted disease in males. Clinicians should be familiar with the proper evaluation and management of this common condition.

Objective

To provide an update on the current understanding, evaluation, and management of penile warts.

Methods

A PubMed search was completed in Clinical Queries using the key terms 'penile warts' and 'genital warts'. The search strategy included meta-analyses, randomized controlled trials, clinical trials, observational studies, and reviews.

Results

Penile warts are caused by human papillomavirus (HPV), notably HPV-6 and HPV-11. Penile warts typically present as asymptomatic papules or plaques. Lesions may be filiform, exophytic, papillomatous, verrucous, hyperkeratotic, cerebriform, fungating, or cauliflower-like. Approximately one-third of penile warts regress without treatment and the average duration prior to resolution is approximately 9 months. Active treatment is preferable to watchful observation to speed up clearance of the lesions and to assuage fears of transmission and autoinoculation. Patient-administered therapies include podofilox (0.5%) solution or gel, imiquimod 3.75 or 5% cream, and sinecatechins (polypheron E) 15% ointment. Clinician-administered therapies include podophyllin, cryotherapy, bichloroacetic or trichloroacetic acid, oral cimetidine, surgical excision, electrocautery, and carbon dioxide laser therapy. Patients who do not respond to first-line treatments may respond to other therapies or a combination of treatment modalities. Second-line therapies include topical/intralesional/intravenous cidofovir, topical 5-fluorouracil, and topical ingenol mebutate.

Conclusion

No single treatment has been shown to be consistently superior to other treatment modalities. The choice of the treatment method should depend on the physician's comfort level with the various treatment options, the patient's preference and tolerability of treatment, and the number and severity of lesions. The comparative efficacy, ease of administration, adverse effects, cost, and availability of the treatment modality should also be taken into consideration.

Ingenol mebutate induces a tumor cell-directed inflammatory response and antimicrobial peptides thereby promoting rapid tumor destruction and wound healing

BACKGROUND

Ingenol mebutat (IM)-gel is effective for the topical treatment of epithelial tumors, including actinic keratoses (AKs) or anogenital warts (AGW). AK patients treated with IM develop intensified inflammatory reactions on sights of prior clinical visible or palpable AKs as compared to the surrounding actinically damaged skin, suggesting the induction of a tumor cell-directed inflammation. AGW patients treated with IM develop even stronger inflammatory reactions with large erosions, suggesting a directed inflammatory response against HPV-infected keratinocytes. Of note, even widespread erosions heal very fast without any superinfections. Here, we set out to elucidate underlying molecular and cellular mechanisms of these clinical observations.

METHODS

The effects of IM (10-9-10-5 M) on the expression and translation of a comprehensive set of chemokines (CXCL1, CXCL8, CXCL9, CXCL10, CXCL11, CXCL14, CCL2, CCL5, CCL20, CCL27) and antimicrobial peptides (AMP) (HBD1, HBD2, HBD3, LL37, RNase7) were analyzed in primary human epithelial keratinocytes (HEK) and a set of epithelial cancer cell lines by RT-qPCR and ELISA in vitro. To study the possible effects of different concentrations of IM on migratory, respectively wound healing responses, an in vitro scratch assay was conducted on HEK.

RESULTS

Ingenol mebutat significantly and dose-dependently induced the expression of proinflammatory chemokines (CXCL8, CCL2) and AMP (RNase7, HBD3) in HEK and epithelial cancer cell lines. A significantly stronger induction of CXCL8 and CCL2 was observed in our tested tumor cells as compared to HEK. We did not observe any significant effect of IM on HEK migration, respectively wound healing responses in vitro for any tested concentration (10-9, 10-8, 10-6 M) except 10-7 M, which induced a significant inhibition.

CONCLUSIONS

Our data suggest that tumor cells are more susceptible to IM as compared to differentiated HEK. This is evident by a stronger IM-mediated induction of proinflammatory chemokines in tumor cells, which may result in a tumor cell-directed inflammatory response and rapid tumor destruction. In addition, IM induces AMP in keratinocytes and seems not to severely interfere with keratinocyte migration, which contributes to a fast and uncomplicated wound healing. Surprising is a selective inhibition of keratinocyte migration by IM at the concentration of 10-7 M pointing to very dose depending biological effects, induced by IM.

An exploratory, prospective, open-label trial of ingenol mebutate gel 0.05% for the treatment of external anogenital warts

BACKGROUND

Anogenital warts (AGW) can cause physical discomfort and decreased quality of life. Recent case reports suggest that ingenol mebutate gel might be an effective treatment of AGW.

OBJECTIVE

To explore primarily the safety, and secondarily the efficacy of ingenol mebutate gel 0.05% in patients with AGW.

METHODS

This was an exploratory, open-label, 1-arm trial of ingenol mebutate gel 0.05% administered up to three times to patients with AGW. Safety was assessed by occurrence and severity of local skin reactions (LSRs) and treatment-related adverse events (AEs). Efficacy was assessed by complete clearance and reduction in AGW count 14 days after last treatment, and recurrence 12 weeks after clearance.

RESULTS

Of 41 patients enrolled, 40 received treatment and 26 completed the trial. Patients had a median AGW count of 11.0 and AGW duration of 3.0 years at baseline. All patients experienced transient LSRs following treatment with a maximum composite LSR score of 7.5 (on a scale from 0 to 18). A total of 93% of patients reported treatment-related AEs, most frequently pain (85%) and procedural complications (35%) due to smearing of the gel. 78% of patients took mild analgesics for the pain, typically for 1-2 days following treatment. The majority of AEs were of moderate-to-severe intensity. Seventeen of 39 patients (43.6%) had complete clearance 14 days after last treatment, and AGW count was reduced by 90.9%. There was a tendency towards lower clearance rate in patients with longer duration of AGW. Eight of 14 patients (57.1%) had AGW recurrence 12 weeks after clearance.

CONCLUSION

Ingenol mebutate gel was associated with a high number of AEs and withdrawals due to painful local and adjacent skin reactions. Furthermore, it showed promising efficacy in reducing AGW despite a difficult-to-treat population. Optimization of the formulation is warranted to improve the safety profile of the treatment.

[Genital warts in HIV-infected individuals]

Anogenital warts (condylomata acuminata) are much more frequent in human immunodeficiency (HIV)-positive patients compared to HIV-negative individuals. Anogenital warts of HIV-infected patients differ from those of HIV-negative individuals with respect to their spread, occurrence on more unusual anatomical sites, human papillomavirus (HPV)-type spectrum, tendency to recur, and risk of malignant transformation. Between 18 and 56% of anogenital warts of HIV-positive patients harbor high-grade dysplasia. Therefore, anogenital warts of HIV-infected patients should be preferentially treated with ablative methods and should be evaluated histopathologically. Gender-neutral prophylactic HPV vaccination of HPV-naive boys and girls could also lead to a significant reduction of anogenital warts in this patient group in the future.

Resistance of Nonmelanoma Skin Cancer to Nonsurgical Treatments. Part I: Topical Treatments

A wide range of treatments is now available for nonmelanoma skin cancer (NMSC), including 5-fluorouracil, ingenol mebutate, imiquimod, diclofenac, photodynamic therapy, methotrexate, cetuximab, vismodegib, and radiotherapy. All are associated with high clinical and histologic response rates. However, some tumors do not respond due to resistance, which may be primary or acquired. Study of the resistance processes is a broad area of research that aims to increase our understanding of the nature of each tumor and the biologic features that make it resistant, as well as to facilitate the design of new therapies directed against these tumors. In this article we review resistance to the authorized topical treatments for NMSC.

Ingenane Diterpenoids

Despite a more recent isolation and chemical characterization when compared to phorbol, along with its chemical instability, limited distribution in Nature, and scarce availability, ingenol is the only Euphorbia diterpenoid that has undergone successful pharmaceutical development, with ingenol 3-angelate (ingenol mebutate, Picato(®)) entering the pharmaceutical market in 2012 for the treatment of actinic keratosis. The phytochemical, chemical, and biological literature on members of the ingenane class of diterpenoids is reviewed from their first isolation in 1968 through 2015, highlighting unresolved issues both common to phorboids (biogenesis, relationship between molecular targets, and in vivo activity) and specific to ingenol derivatives (two-dimensional representation, in-out stereoisomerism, versatility of binding mode to PKC, and inconsistencies in the structural elucidation of some classes of derivatives). The biogenesis of ingenol is discussed in the light of the Jakupovic proposal of a dissection between the formation of the macrocyclic Euphorbia diterpenoids and the phorboids, and the clinical development of ingenol mebutate is chronicled in the light of its "reverse-pharmacology" focus.