Ultraviolet Radiation Inhibits Mammary Carcinogenesis in an ER-Negative Murine Model by a Mechanism Independent of Vitamin D3.

Three decades ago, the Garlands postulated that vitamin D3 produced in the skin by ultraviolet radiation (UVR)-induced conversion of 7-dehydrocholesterol to pre-D3 has anticancer effects, thus triggering more than 9,500 publications on D3 and cancer. Here, we report that UVR treatment of transgenic mice of the well-established C3(1)/SV40 Tag mammary cancer model significantly inhibits both autochthonous carcinogenesis and allograft tumor growth, but in contrast neither dietary nor topical D3 influences mammary carcinogenesis in this specific mouse model. Furthermore, UVR's inhibitory effects occur irrespective of whether or not the treatment increases circulating D3 in the mice. The inhibitory effect of UVR on autochthonous tumors occurs at or before the stage of ductal carcinoma in situ. Our studies indicate clearly that UVR can exert D3-independent anticancer effects in C3(1)/SV40 Tag mice. Therefore, supplemental D3 may not mimic all possible beneficial effects of UVR, and uncovering non-D3-mediated mechanisms of UVR tumor inhibition may lead to novel strategies for cancer prevention. Cancer Prev Res; 11(7); 383-92. ©2018 AACR.

Noncanonical hedgehog pathway activation through SRF-MKL1 promotes drug resistance in basal cell carcinomas.

Hedgehog pathway-dependent cancers can escape Smoothened (SMO) inhibition through mutations in genes encoding canonical hedgehog pathway components; however, around 50% of drug-resistant basal cell carcinomas (BCCs) lack additional variants of these genes. Here we use multidimensional genomics analysis of human and mouse drug-resistant BCCs to identify a noncanonical hedgehog activation pathway driven by the transcription factor serum response factor (SRF). Active SRF along with its coactivator megakaryoblastic leukemia 1 (MKL1) binds DNA near hedgehog target genes and forms a previously unknown protein complex with the hedgehog transcription factor glioma-associated oncogene family zinc finger-1 (GLI1), causing amplification of GLI1 transcriptional activity. We show that cytoskeletal activation through Rho and the formin family member Diaphanous (mDia) is required for SRF-MKL-driven GLI1 activation and for tumor cell viability. Remarkably, nuclear MKL1 staining served as a biomarker in tumors from mice and human subjects to predict tumor responsiveness to MKL inhibitors, highlighting the therapeutic potential of targeting this pathway. Thus, our study illuminates, for the first time, cytoskeletal-activation-driven transcription as a personalized therapeutic target for combatting drug-resistant malignancies.

Genomic Stability in Syndromic Basal Cell Carcinoma.

Basal cell cancers (BCCs) are characterized by upregulation of Hedgehog pathway through loss of PTCH1 or activation of SMO, and SMO inhibitors, such as vismodegib, are effective therapies for advanced BCCs. Although most BCCs are sporadic, rare individuals with basal cell nevus syndrome (BCNS) harbor germline defects in PTCH1 and develop up to hundreds of tumors that are histopathologically indistinguishable from sporadic BCCs. Interestingly, BCNS-BCCs are more responsive to SMO inhibitors than sporadic BCCs, with minimal development of resistance. Given differences in clinical course and therapy response, we sought to characterize BCCs in the setting of BCNS. We found that BCNS individuals with low tumor burden demonstrated significantly fewer UV signature somatic mutations and lower overall somatic mutational load compared to BCNS individuals with high burden, supporting a role of UV exposure in driving BCC development in BCNS individuals. However, compared with sporadic BCCs, BCNS-BCCs have a significantly lower mutational load, lower proportion of UV mutagenesis, increased genomic stability, and harbor fewer functionally resistant SMO mutations at baseline, explaining why BCNS-BCCs lack intrinsic resistance to SMO inhibitors. BCNS-BCCs appear to have reduced mutator phenotype compared with sporadic BCCs, which may contribute to their relatively more indolent clinical course and responsiveness to therapy.

Combined inhibition of atypical PKC and histone deacetylase 1 is cooperative in basal cell carcinoma treatment.

Advanced basal cell carcinomas (BCCs) circumvent Smoothened (SMO) inhibition by activating GLI transcription factors to sustain the high levels of Hedgehog (HH) signaling required for their survival. Unfortunately, there is a lack of efficacious therapies. We performed a gene expression-based drug repositioning screen in silico and identified the FDA-approved histone deacetylase (HDAC) inhibitor, vorinostat, as a top therapeutic candidate. We show that vorinostat only inhibits proliferation of BCC cells in vitro and BCC allografts in vivo at high dose, limiting its usefulness as a monotherapy. We leveraged this in silico approach to identify drug combinations that increase the therapeutic window of vorinostat and identified atypical PKC Ɩ/ʎ (aPKC) as a HDAC costimulator of HH signaling. We found that aPKC promotes GLI1-HDAC1 association in vitro, linking two positive feedback loops. Combination targeting of HDAC1 and aPKC robustly inhibited GLI1, lowering drug doses needed in vitro, in vivo, and ex vivo in patient-derived BCC explants. We identified a bioavailable and selective small-molecule aPKC inhibitor, bringing the pharmacological blockade of aPKC and HDAC1 into the realm of clinical possibility. Our findings provide a compelling rationale and candidate drugs for combined targeting of HDAC1 and aPKC in HH-dependent cancers.

Vitamin D3 Produced by Skin Exposure to UVR Inhibits Murine Basal Cell Carcinoma Carcinogenesis.

The effect of UVR on human basal cell carcinoma (BCC) epidemiology is complex-the incidence rises until approximately 30,000 hours of lifetime sunlight exposure and then plateaus. We hypothesize that UVR has opposing effects on BCC carcinogenesis-stimulatory via mutagenesis and inhibitory via production of hedgehog-inhibiting vitamin D3 (D3). We find that UVR exposure of ionizing radiation-treated Ptch1+/- mice accelerates BCC carcinogenesis in male mice, in which UVR does not produce D3. By contrast, in female mice, in which UVR does produce D3, UVR fails to accelerate BCC carcinogenesis, thus mirroring the plateauing in humans. However, if D3 production is attenuated in female mice by deletion of keratinocyte lathosterol 5-desaturase, then UVR accelerates ionizing radiation-induced BCC carcinogenesis. Congruently, chronic topical application of D3 inhibits ionizing radiation-induced BCC tumorigenesis. These findings confirm that UVR-induced production of D3 in keratinocytes significantly restrains murine BCC tumorigenesis and demonstrate the counterintuitive conclusion that UVR has anti-BCC carcinogenic effects that can explain, at least in part, the complex relationship between exposure to UVR and BCC incidence.

Attenuation of UVR-induced vitamin D3 synthesis in a mouse model deleted for keratinocyte lathosterol 5-desaturase.

The lower risk of some internal cancers at lower latitudes has been linked to greater sun exposure and consequent higher levels of ultraviolet radiation (UVR)-produced vitamin D3 (D3). To separate the experimental effects of sunlight and of all forms of D3, a mouse in which UVR does not produce D3 would be useful. To this end we have generated mice carrying a modified allele of sterol C5-desaturase (Sc5d), the gene encoding the enzyme that converts lathosterol to 7-dehydrocholesterol (7-DHC), such that Sc5d expression can be inactivated using the Cre/lox site-specific recombination system. By crossing to mice with tissue-specific expression of Cre or CreER2 (Cre/estrogen receptor), we generated two lines of transgenic mice. One line has constitutive keratinocyte-specific inactivation of Sc5d (Sc5dk14KO). The other line (Sc5dk14KOi) has tamoxifen-inducible keratinocyte-specific inactivation of Sc5d. Mice deleted for keratinocyte Sc5d lose the ability to increase circulating D3 following UVR exposure of the skin. Thus, unlike in control mice, acute UVR exposure did not affect circulating D3 level in inducible Sc5dk14KOi mice. Keratinocyte-specific inactivation of Sc5d was proven by sterol measurement in hair - in control animals lathosterol and cholesta-7,24-dien-3ß-ol, the target molecules of SC5D in the sterol biosynthetic pathways, together constituted a mean of 10% of total sterols; in the conditional knockout mice these sterols constituted a mean of 56% of total sterols. The constitutive knockout mice had an even greater increase, with lathosterol and cholesta-7,24-dien-3ß-ol accounting for 80% of total sterols. In conclusion, the dominant presence of the 7-DHC precursors in hair of conditional animals and the lack of increased circulating D3 following exposure to UVR reflect attenuated production of the D3 photochemical precursor 7-DHC and, consequently, of D3 itself. These animals provide a useful new tool for investigating the role of D3 in UVR-induced physiological effects and, more broadly, for investigations of the cholesterol synthetic pathway in the skin and other targeted tissues.

Risk Factors for Basal Cell Carcinoma Among Patients With Basal Cell Nevus Syndrome: Development of a Basal Cell Nevus Syndrome Patient Registry.

IMPORTANCE: Patients with basal cell nevus syndrome (BCNS) have a greater risk of developing numerous basal cell carcinomas (BCCs). Risk factors influencing the wide variation in tumor burden are poorly understood. OBJECTIVE: To describe the burden of BCCs in patients with BCNS in the United States and identify potential risk factors for BCCs. DESIGN, SETTING, AND PARTICIPANTS: Prospective clinical registry with data collected from September 2014 to March 2016. Participants were recruited from a mailing list of patients with BCNS at Children's Hospital Oakland Research Institute and Basal Cell Carcinoma Nevus Syndrome Life Support Network. Patients of all ages with a diagnosis of BCNS were eligible for enrollment. Participants completed a clinical questionnaire on their disease characteristics and risk factors. MAIN OUTCOMES AND MEASURES: Number of BCCs in the past 2 years and over lifetime (disease burden), risk factors for BCCs. RESULTS: A consecutive sample of the first 141 participants was included (34% [100 of 297] response rate from paper survey, 23% [41 of 179] from online survey; 85 [60%] female; mean age at start of study, 53 [range, 8-83] years; 131 [93%] white). In the previous 2 years, participants reported a mean of 25 BCCs (median, 11; range, 0-250). Over their lifetime, participants reported a mean of 257 BCCs (median, 160; range, 0-2200). Univariate analysis identified age (odds ratio [OR], 1.05; 95% CI, 1.03-1.07; P < .001), number of sunburns (OR, 1.05; 95% CI, 1.00-1.10; P = .047), and history of radiation exposure (OR, 2.26; 95% CI, 1.02-5.03; P = .046) as potential risk factors for lifetime BCC severity. On multivariate analysis, only age (OR, 1.04; 95% CI, 1.02-1.07; P < .001) and number of sunburns (OR, 1.06; 95% CI, 1.00-1.11; P = .04) were statistically significant. In our adjusted models, BCC burden increased by 4% per year of age and by 6% per number of sunburns. CONCLUSIONS AND RELEVANCE: Patients with BCNS have a high burden of BCCs. Age and number of sunburns were significantly associated with the severity of lifetime BCC. Further interventions to prevent and treat BCCs in patients with BCNS are needed.

Inhibition of the hedgehog pathway in patients with basal-cell nevus syndrome: final results from the multicentre, randomised, double-blind, placebo-controlled, phase 2 trial.

BACKGROUND: Aberrant hedgehog signalling underlies the development of basal-cell carcinomas. We previously reported the interim analysis of a multicentre, randomised, double-blind, placebo-controlled, phase 2 trial in patients with the basal-cell nevus (Gorlin) syndrome indicating that the smoothened inhibitor vismodegib reduces basal-cell carcinoma tumour burden and prevents new basal-cell carcinoma growth in patients with basal-cell nevus syndrome. We report the final results of this 36 month trial. METHODS: In our multicentre, randomised, double-blind, placebo-controlled, phase 2 trial we enrolled patients aged 35-75 years with basal-cell nevus syndrome with at least ten surgically eligible basal-cell carcinomas at the Children's Hospital Oakland, Columbia University outpatient dermatology clinic (NY, USA) and a private practice outpatient dermatology office in Newport Beach (CA, USA). Patients were assigned to vismodegib or placebo (2:1) according to a randomisation sequence generated by computer code. The primary endpoint of the trial of 41 patients was to compare the effect of oral vismodegib (150 mg/day) versus placebo on the incidence of new surgically eligible basal-cell carcinomas after 3 months of treatment. In the subsequent, open-label phase (n=37) patients continued vismodegib at two sites for as long as month 36 (n=25) and at the third site were monitored up to month 36 (n=12). Additional endpoints for this phase were: whether continuous versus interrupted dosing differentially affected tumour burden; time to reach various levels of reduction in tumour burden; reduction in tumour size in patients who took less than 50% of the expected number of vismodegib tablets; reduction in the number of surgical excisions required per year before, during, and after treatment; and the effect of vismodegib on hedgehog target gene expression. We monitored patients at visits every 3 months for up to 36 months. The primary endpoint was analysed on a modified intention-to-treat basis. This trial is registered with ClinicalTrials.gov, number NCT00957229. FINDINGS: Between Sept 22, 2009, and Jan 24, 2011, 41 patients were monitored for a median of 36 months (IQR 36-36). Patients treated with vismodegib (n=26) had a mean reduced rate of new surgically eligible basal-cell carcinomas compared with patients randomly assigned to placebo (n=15; two [SD 0·12] new surgically eligible basal-cell carcinomas per patient per year vs 34 [1·32] new surgically eligible basal-cell carcinomas per patient per year, p<0·0001). In the 11 patients initially assigned to placebo, mean cross over to vismodegib reduced the development of new surgically eligible basal-cell carcinomas compared with placebo (0·4 [SD 0·2] new surgically eligible basal-cell carcinomas per patient per year vs 30·0 [7·8] new surgically eligible basal-cell carcinomas per patient per year, p<0·0001). Only three (17%) of 18 patients tolerated vismodegib continuously for the full 36 months. Fewer new surgically eligible basal-cell carcinomas developed in patients receiving vismodegib continuously than in those who interrupted dosing (mean 0·6 [0·72] new surgically eligible basal-cell carcinomas per patient per year vs 1·7 [1·8] new surgically eligible basal-cell carcinomas per patient per year, p<0·0001). Treatment-related grade 3-4 adverse events included weight loss of 20% or more (n=6) and muscle cramps (n=2). Two patients died during the course of the trial, one each from laryngeal and metastatic prostate cancer, deemed probably unrelated to drug. INTERPRETATION: Vismodegib reduces basal-cell carcinoma tumour burden in patients with basal-cell nevus syndrome. Adverse events associated with vismodegib frequently led to interruption of treatment, which is followed by basal-cell carcinoma recurrence. FUNDING: Genentech investigator-initiated trial funding, Clinical and Translational Science Award from the National Institutes of Health, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Cancer Institute, Damon Runyon Cancer Research Foundation Clinical Investigator Award, Swim across America Foundation, and Michael J Rainen Family Foundation.

Posaconazole, a Second-Generation Triazole Antifungal Drug, Inhibits the Hedgehog Signaling Pathway and Progression of Basal Cell Carcinoma.

Deregulation of Hedgehog (Hh) pathway signaling has been associated with the pathogenesis of various malignancies, including basal cell carcinomas (BCC). Inhibitors of the Hh pathway currently available or under clinical investigation all bind and antagonize Smoothened (SMO), inducing a marked but transient clinical response. Tumor regrowth and therapy failure were attributed to mutations in the binding site of these small-molecule SMO antagonists. The antifungal itraconazole was demonstrated to be a potent SMO antagonist with a distinct mechanism of action from that of current SMO inhibitors. However, itraconazole represents a suboptimal therapeutic option due to its numerous drug-drug interactions. Here, we show that posaconazole, a second-generation triazole antifungal with minimal drug-drug interactions and a favorable side-effect profile, is also a potent inhibitor of the Hh pathway that functions at the level of SMO. We demonstrate that posaconazole inhibits the Hh pathway by a mechanism distinct from that of cyclopamine and other cyclopamine-competitive SMO antagonists but, similar to itraconazole, has robust activity against drug-resistant SMO mutants and inhibits the growth of Hh-dependent BCC in vivo Our results suggest that posaconazole, alone or in combination with other Hh pathway antagonists, may be readily tested in clinical studies for the treatment of Hh-dependent cancers. Mol Cancer Ther; 15(5); 866-76. ©2016 AACR.

The use of vismodegib to shrink keratocystic odontogenic tumors in patients with basal cell nevus syndrome.

IMPORTANCE: Keratocystic odontogenic tumors (KCOTs) of the jaw affect more than 65% of patients with basal cell nevus syndrome (BCNS). Surgery frequently causes facial disfigurement and is not always curative. Most BCNS-related and some sporadic KCOTs have malignant activation of the Hedgehog signaling pathway. OBSERVATIONS: We examined the effect of vismodegib (an oral Hedgehog pathway inhibitor) on KCOT size in patients with BCNS enrolled in a clinical trial testing vismodegib for basal cell carcinoma prevention (NCT00957229), using pretreatment and posttreatment magnetic resonance imaging. Four men and 2 women had pretreatment KCOTs (mean longest diameter, 2.0 cm; range, 0.7-3.3 cm), occurring primarily in the mandible. Patients were treated with vismodegib, 150 mg/d, for a mean (SD) of 18.0 (4.8) months (range, 11-24 months). Four patients experienced a size reduction and 2 had no change. Vismodegib reduced the mean longest diameter of KCOTs in all patients by 1.0 cm (95% CI, 0.03-1.94; P = .02) or 50% from baseline. We observed no enlargement of existing KCOTs or new KCOT development. CONCLUSIONS AND RELEVANCE: Vismodegib shrinks some KCOTs in patients with BCNS and may offer an alternative to surgical therapy. These effects were maintained for at least 9 months after drug cessation in 1 patient. Further studies assessing long-term efficacy and optimal maintenance regimens should be performed.

Tazarotene: randomized, double-blind, vehicle-controlled, and open-label concurrent trials for basal cell carcinoma prevention and therapy in patients with basal cell nevus syndrome.

Sporadic human basal cell carcinomas (BCC) are generally well managed with current surgical modalities. However, in the subset of high-risk patients predisposed to developing large numbers of BCCs, there is an unmet need for effective, low-morbidity chemoprevention. This population includes fair-skinned patients with extensive sun exposure and those with genodermatoses such as the basal cell nevus (Gorlin) syndrome (BCNS). Tazarotene (Tazorac, Allergan) is a topical retinoid with relative specificity for RAR-ß and RAR-γ receptors. We previously demonstrated tazarotene's robust anti-BCC efficacy in Ptch1(+/-) mice, a murine equivalent of BCNS, and others have found it to have some efficacy against sporadic human BCCs. We report here results of a randomized, double-blind, vehicle-controlled study in patients with BCNS evaluating the efficacy of topically applied tazarotene for BCC chemoprevention (N = 34 subjects), along with an open-label trial evaluating tazarotene's efficacy for chemotherapy of BCC lesions (N = 36 subjects) for a maximum follow-up period of 3 years. We found that only 6% of patients had a chemopreventive response and that only 6% of treated BCC target lesions were clinically cured. Our studies provide no evidence for either chemopreventive or chemotherapeutic effect of tazarotene against BCCs in patients with BCNS.

PI3K-AKT signaling is a downstream effector of retinoid prevention of murine basal cell carcinogenesis.

Basal cell carcinoma (BCC) is the most common human cancer. We have demonstrated previously that topical application of the retinoid prodrug tazarotene profoundly inhibits murine BCC carcinogenesis via retinoic acid receptor γ-mediated regulation of tumor cell transcription. Because topical retinoids can cause adverse cutaneous effects and because tumors can develop resistance to retinoids, we have investigated mechanisms downstream of tazarotene's antitumor effect in this model. Specifically we have used (i) global expression profiling to identify and (ii) functional cell-based assays to validate the phosphoinositide 3-kinase (PI3K)/AKT/mTOR pathway as a downstream target pathway of tazarotene's action. Crucially, we have demonstrated that pharmacologic inhibition of this downstream pathway profoundly reduces murine BCC cell proliferation and tumorigenesis both in vitro and in vivo. These data identify PI3K/AKT/mTOR signaling as a highly attractive target for BCC chemoprevention and indicate more generally that this pathway may be, in some contexts, an important mediator of retinoid anticancer effects.

First-in-human trial of nanoelectroablation therapy for basal cell carcinoma: proof of method.

This nanoelectroablation therapy effectively treats subdermal murine allograft tumors, autochthonous basal cell carcinoma (BCC) tumors in Ptch1+/-K14-Cre-ER p53 fl/fl mice, and UV-induced melanomas in C57/BL6 HGF/SF mice. Here, we described the first human trial of this modality. We treated 10 BCCs on three subjects with 100-1000 electric pulses 100 ns in duration, 30 kV/cm in amplitude, applied at 2 pulses per second. Seven of the 10 treated lesions were completely free of basaloid cells when biopsied and two partially regressed. Two of the 7 exhibited seborrheic keratosis in the absence of basaloid cells. One of the 10 treated lesions recurred by week 10 and histologically had the appearance of a squamous cell carcinoma. No scars were visible at the healed sites of any of the successfully ablated lesions. One hundred pulses were sufficient for complete ablation of BCCs with a single, 1-min nanoelectroablation treatment.

Skin cancer: Basal cell carcinoma--pay your money, take your choice.

Superficial basal cell carcinomas are a common challenge in clinical dermatology because they are frequent and surgical approaches tend to scar. A large randomized trial comparing three nonsurgical approaches has shown that all had similar clinical outcomes - so, you pay your money and take your choice.

Itraconazole and arsenic trioxide inhibit Hedgehog pathway activation and tumor growth associated with acquired resistance to smoothened antagonists.

Recognition of the multiple roles of Hedgehog signaling in cancer has prompted intensive efforts to develop targeted pathway inhibitors. Leading inhibitors in clinical development act by binding to a common site within Smoothened, a critical pathway component. Acquired Smoothened mutations, including SMO(D477G), confer resistance to these inhibitors. Here, we report that itraconazole and arsenic trioxide, two agents in clinical use that inhibit Hedgehog signaling by mechanisms distinct from that of current Smoothened antagonists, retain inhibitory activity in vitro in the context of all reported resistance-conferring Smoothened mutants and GLI2 overexpression. Itraconazole and arsenic trioxide, alone or in combination, inhibit the growth of medulloblastoma and basal cell carcinoma in vivo, and prolong survival of mice with intracranial drug-resistant SMO(D477G) medulloblastoma.