Dermatology Research Unit

San Francisco, CA, United States

Dermatology Research Unit

San Francisco, CA, United States
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Brochez L.,Ghent University | Brochez L.,Dermatology Research Unit | Brochez L.,A+ Network | Brochez L.,Cancer Research Institute Ghent CRIG | And 5 more authors.
European Journal of Cancer | Year: 2017

Indoleamine 2,3-dioxygenase (IDO, also referred to as IDO1) has been demonstrated to be a normal endogenous mechanism of acquired peripheral immune tolerance in vivo. In the field of oncology, IDO expression and/or activity has been observed in several cancer types and has usually been associated with negative prognostic factors and worse outcome measures. This manuscript reviews current available data on the role of IDO in cancer and the current results obtained with IDO inhibition, both in animal models and in phase 1 and 2 clinical trials in humans. Preliminary results with IDO inhibitors, usually combined with other anti-cancer drugs, seem encouraging. Further studies are needed to clarify the conditions in which IDO inhibitors can be of value as an anti-cancer strategy. In addition, further research should address whether the expression of IDO in tissue or blood can be a marker to select patients who can benefit most from IDO inhibition. © 2017


Zheng C.L.,Oregon Health And Science University | Wang N.J.,Oregon Health And Science University | Chung J.,Samsung | Moslehi H.,University of California at San Francisco | And 27 more authors.
Cell Reports | Year: 2014

Somatic mutations in cancer are more frequent in heterochromatic and late-replicating regions of the genome. We report that regional disparities in mutation density are virtually abolished within transcriptionally silent genomic regions of cutaneous squamous cell carcinomas (cSCCs) arising in an XPC-/- background. XPC-/- cells lack global genome nucleotide excision repair (GG-NER), thus establishing differential access of DNA repair machinery within chromatin-rich regions of the genome as the primarycause for the regional disparity. Strikingly, we find that increasing levels of transcription reduce mutation prevalence on both strands of gene bodies embedded within H3K9me3-dense regions, and only to those levels observed in H3K9me3-sparse regions, also in an XPC-dependent manner. Therefore, transcription appears to reduce mutation prevalence specifically by relieving the constraints imposed by chromatin structure on DNA repair. We model this relationship among transcription, chromatin state, and DNA repair, revealing a new, personalized determinant of cancer risk. © 2014 The Authors.


Krishnan R.,University of California at San Francisco | Krishnan R.,Dermatology Research Unit | Oh D.H.,University of California at San Francisco | Oh D.H.,Dermatology Research Unit
Journal of Nucleic Acids | Year: 2010

Triplex-forming oligonucleotides (TFOs) with both DNA and 2′-O-methyl RNA backbones can direct psoralen photoadducts to specific DNA sequences. However, the functional consequences of these differing structures on psoralen photoreactivity are unknown. We designed TFO sequences with DNA and 2′-O-methyl RNA backbones conjugated to psoralen by 2-carbon linkers and examined their ability to bind and target damage to model DNA duplexes corresponding to sequences within the human HPRT gene. While TFO binding affinity was not dramatically affected by the type of backbone, psoralen photoreactivity was completely abrogated by the 2′-O-methyl RNA backbone. Photoreactivity was restored when the psoralen was conjugated to the RNA TFO via a 6-carbon linker. In contrast to the B-form DNA of triplexes formed by DNA TFOs, the CD spectra of triplexes formed with 2′-O-methyl RNA TFOs exhibited features of A-form DNA. These results indicate that 2′-O-methyl RNA TFOs induce a partial B-to-A transition in their target DNA sequences which may impair the photoreactivity of a conjugated psoralen and suggest that optimal design of TFOs to target DNA damage may require a balance between binding ability and drug reactivity. © 2010 Rajagopal Krishnan and Dennis H. Oh.


Schulman J.M.,University of California at San Francisco | Oh D.H.,University of California at San Francisco | Oh D.H.,Dermatology Research Unit | Sanborn J.Z.,NantOmics LLC | And 3 more authors.
JAMA Dermatology | Year: 2016

IMPORTANCE: Multiple hereditary infundibulocystic basal cell carcinoma syndrome (MHIBCC) is a rare genodermatosis in which numerous indolent, well-differentiated basal cell carcinomas develop primarily on the face and genitals, without other features characteristic of basal cell nevus syndrome. The cause is unknown. The purpose of the study was to identify a genetic basis for the syndrome and a mechanism bywhich the associated tumors develop. OBSERVATIONS: Whole-exome sequencing of 5 tumors and a normal buccal mucosal sample from a patient with MHIBCC was performed. A conserved splice-site mutation in 1 copy of the suppressor of fused gene (SUFU) was identified in all tumor and normal tissue samples. Additional distinct deletions of the trans SUFU allele were identified in all tumor samples, none of which were present in the normal sample. CONCLUSIONS AND RELEVANCE: A germline SUFU mutation was present in a patient with MHIBCC, and additional acquired SUFU mutations underlie the development of infundibulocystic basal cell carcinomas. The downstream location of the SUFU gene within the sonic hedgehog pathway may explain why its loss is associated with relatively well-differentiated tumors and suggests that MHIBCC will not respond to therapeutic strategies, such as smoothened inhibitors, that target upstream components of this pathway. © Copyright 2016 American Medical Association. All rights reserved.


Dong T.K.,Dermatology Research Unit | Dong T.K.,University of California at San Francisco | Ona K.,Dermatology Research Unit | Scandurra A.E.,Dermatology Research Unit | And 4 more authors.
Photochemistry and Photobiology | Year: 2016

Squamous cell carcinomas (SCCs) are associated with ultraviolet radiation and multiple genetic changes, but the mechanisms leading to genetic instability are unclear. SCC cell lines were compared to normal keratinocytes for sensitivity to ultraviolet radiation, DNA repair kinetics and DNA repair protein expression. Relative to normal keratinocytes, four SCC cell lines were all variably sensitive to ultraviolet radiation and, except for the SCC25 cell line, were deficient in global repair of cyclobutane pyrimidine dimers, although not 6-4 photoproducts. Impaired DNA repair of cyclobutane pyrimidine dimers was associated with reduced mRNA expression from XPC but not DDB2 genes which each encode key DNA damage recognition proteins. However, levels of XPC or DDB2 proteins or both were variably reduced in repair-deficient SCC cell lines. p53 levels did not correlate with DNA repair activity or with XPC and DDB2 levels, but p63 levels were deficient in cell lines with reduced global repair. Repair-proficient SCC25 cells depleted of p63 lost XPC expression, early global DNA repair activity and UV resistance. These results demonstrate that some SCC cell lines are deficient in global nucleotide excision repair and support a role for p63 as a regulator of nucleotide excision repair in SCCs. © 2016 The American Society of Photobiology


Ona K.,University of California at San Francisco | Ona K.,Dermatology Research Unit | Oh D.H.,University of California at San Francisco | Oh D.H.,Dermatology Research Unit
British Journal of Dermatology | Year: 2015

Background The antifungal agent, voriconazole, is associated with phototoxicity and photocarcinogenicity. Prior work has indicated that voriconazole and its hepatic N-oxide metabolite do not sensitize keratinocytes to ultraviolet B (UVB). Clinical observations have suggested that ultraviolet A (UVA) may be involved. Objectives To determine the photochemistry and photobiology of voriconazole and its major hepatic metabolite, voriconazole N-oxide. Materials and methods Voriconazole and voriconazole N-oxide were spectrophotometrically monitored following various doses of UVB. Cultured human keratinocytes were treated with parental drugs or with their UVB photoproducts, and survival following UVA irradiation was measured by thiazolyl blue metabolism. Reactive oxygen species (ROS) and 8-oxoguanine were monitored by fluorescence microscopy. Results Voriconazole and voriconazole N-oxide have varying UVB absorption but do not acutely sensitize cultured human keratinocytes following UVB exposure. However, sustained UVB exposures produced notable dose- and solvent-dependent changes in the absorption spectra of voriconazole N-oxide, which in aqueous solution acquires a prominent UVA absorption band, suggesting formation of a discrete photoproduct. Neither the parental drugs nor their photoproducts sensitized cells to UVB although all but voriconazole N-oxide were moderately toxic to cells in the dark. Notably, both voriconazole N-oxide and its UVB photoproduct, but not voriconazole or its photoproduct, additionally sensitized cells to UVA by greater than three-fold relative to controls in association with UVA-induced ROS and 8-oxoguanine levels. Conclusions Voriconazole N-oxide and its UVB-photoproduct act as UVA-sensitizers that generate ROS and that produce oxidative DNA damage. These results suggest a mechanism for the phototoxicity and photocarcinogenicity observed with voriconazole treatment. What's already known about this topic? Voriconazole is associated with photosensitivity and aggressive skin cancers. Voriconazole does not confer sensitivity to ultraviolet (UV) B but UVA sensitivity has been reported in patients. What does this study add? The hepatically generated N-oxide derivative of voriconazole and its UVB photoproduct sensitize keratinocytes to UVA but not to UVB. In keratinocytes treated with voriconazole N-oxide or its UVB photoproduct, UVA induces reactive oxygen species and oxidative DNA damage, suggesting a mechanism for the phototoxicity and photocarcinogenesis associated with voriconazole in skin. © Published 2015. This article is a U.S. Government work and is in the public domain in the U.S.A.


Demetriou S.K.,University of California at San Francisco | Demetriou S.K.,Dermatology Research Unit | Ona-Vu K.,University of California at San Francisco | Ona-Vu K.,Dermatology Research Unit | And 9 more authors.
International Journal of Cancer | Year: 2012

The pathways by which Merkel cell polyomavirus (MCV) infection contributes to the formation of Merkel cell carcinomas are important for understanding the pathogenesis of these cancers. We hypothesized that MCV T antigen suppresses normal responses to ultraviolet radiation (UVR)-induced DNA damage. An MCV-infected cell line (MKL-1) exhibited UVR hypersensitivity, impaired repair of DNA lesions and cell cycle arrest after UVR, as well as reduced levels of the DNA damage recognition protein, XPC. When ectopically expressed in uninfected UISO cells, mutant but not wild-type T antigen resulted in loss of repair of UVR-induced cyclobutane pyrimidine dimers and reductions in XPC, p53 and p21 levels, whereas both wild-type and mutant T antigen inhibited cell cycle arrest after UVR. Similarly, only mutant T antigen in normal fibroblasts inhibited DNA repair and XPC expression, while both mutant and wild-type T antigens produced cell cycle dysregulation. Wild-type T antigen expression produced large T, 57 kT and small T antigens while mutant T antigen was only detectable as a truncated large T antigen protein. Expression of wild-type large T antigen but not small T antigen inhibited the G1 checkpoint in UISO cells, but neither wild-type large T nor small T antigens affected DNA repair, suggesting that large T antigen generates cell cycle defects, and when mutated may also impair DNA repair. These results indicate that T antigen expression by MCV can inhibit key responses to UVR-induced DNA damage and suggest that progressive MCV-mediated abrogation of genomic stability may be involved in Merkel cell carcinogenesis. © 2011 UICC.


De Feraudy S.,University of California at San Francisco | Ridd K.,University of California at San Francisco | Richards L.M.,University of California at San Francisco | Kwok P.-Y.,University of California at San Francisco | And 5 more authors.
American Journal of Pathology | Year: 2010

XPC, the main damage-recognition protein responsible for nucleotide excision repair of UVB damage to DNA, is lost or mutated in xeroderma pigmentosum group C (XP-C), a rare inherited disease characterized by high incidence and early onset of non-melanoma and melanoma skin cancers. The high incidence of skin cancers in XP-C patients suggests that loss of expression of XPC protein might also provide a selective advantage for initiation and progression of similar cancers in non XP-C patients in the general population. To test whether XPC is selectively lost in squamous cell carcinomas from non XP-C patients, we examined XPC expression by immunohistochemistry on a tissue microarray with 244 tissue cores, including in situ and invasive squamous-cell carcinomas (SCCs), keratoacanthoma (KA), and normal skin samples from both immunocompetent and immuno-suppressed patients. We found that XPC expression was lost in 49% of invasive squamous cell carcinomas from immunocompetent patients and 59% from immuno-suppressed patients. Loss of expression was correlated with deletions of chromosomal 3p and mutations in the XPC gene. The XPC gene is consequently inactivated or lost in almost half of squamous cell carcinomas from non XP-C patients. Loss or mutation of XPC may be an early event during skin carcinogenesis that provides a selective advantage for initiation and progression of squamous cell carcinomas in non XP-C patients. Copyright © American Society for Investigative Pathology.


PubMed | Dermatology Research Unit
Type: Journal Article | Journal: Photochemistry and photobiology | Year: 2016

Squamous cell carcinomas (SCCs) are associated with ultraviolet radiation and multiple genetic changes, but the mechanisms leading to genetic instability are unclear. SCC cell lines were compared to normal keratinocytes for sensitivity to ultraviolet radiation, DNA repair kinetics and DNA repair protein expression. Relative to normal keratinocytes, four SCC cell lines were all variably sensitive to ultraviolet radiation and, except for the SCC25 cell line, were deficient in global repair of cyclobutane pyrimidine dimers, although not 6-4 photoproducts. Impaired DNA repair of cyclobutane pyrimidine dimers was associated with reduced mRNA expression from XPC but not DDB2 genes which each encode key DNA damage recognition proteins. However, levels of XPC or DDB2 proteins or both were variably reduced in repair-deficient SCC cell lines. p53 levels did not correlate with DNA repair activity or with XPC and DDB2 levels, but p63 levels were deficient in cell lines with reduced global repair. Repair-proficient SCC25 cells depleted of p63 lost XPC expression, early global DNA repair activity and UV resistance. These results demonstrate that some SCC cell lines are deficient in global nucleotide excision repair and support a role for p63 as a regulator of nucleotide excision repair in SCCs.

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