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We performed a small interfering RNA screen to identify targets for cutaneous squamous cell carcinoma (cSCC) therapy in the ubiquitin/ubiquitin-like system. We provide evidence for selective anti-cSCC activity of knockdown of the E3 ubiquitin ligase MARCH4, the ATPase p97/VCP, the deubiquitinating enzyme USP8, the cullin-RING ligase (CRL) 4 substrate receptor CDT2/DTL, and components of the anaphase-promoting complex/cyclosome (APC/C). Specifically attenuating CRL4CDT2 by CDT2 knockdown can be more potent in killing cSCC cells than targeting CRLs or CRL4s in general by RBX1 or DDB1 depletion. Suppression of the APC/C or forced APC/C activation by targeting its repressor EMI1 are both potential therapeutic approaches. We observed that cSCC cells can be selectively killed by small-molecule inhibitors of USP8 (DUBs-IN-3/compound 22c) and the NEDD8 E1 activating enzyme/CRLs (MLN4924/pevonedistat). A substantial proportion of cSCC cell lines are very highly MLN4924-sensitive. Pathways that respond to defects in proteostasis are involved in the anti-cSCC activity of p97 suppression. Targeting USP8 can reduce the expression of growth factor receptors that participate in cSCC development. EMI1 and CDT2 depletion can selectively cause DNA re-replication and DNA damage in cSCC cells.

NF-κB signaling plays a crucial role in regulating proliferation and differentiation in the epidermis. Alterations in the NF-κB pathway can lead to skin pathologies with a significant burden to human health such as psoriasis and cutaneous squamous cell carcinoma (cSCC). Caspase recruitment domain (CARD)-containing scaffold proteins are key regulators of NF-κB signaling by providing a link between membrane receptors and NF-κB transcriptional subunits. Mutations in the CARD family member, CARD14, have been identified in patients with the inflammatory skin diseases psoriasis and pityriasis rubra pilaris. Here, we describe that the gene coding for another CARD scaffold protein, CARD11, is mutated in more than 38% of 111 cSCCs, and show that novel variants outside of the coiled-coil domain lead to constitutively activated NF-κB signaling. CARD11 protein expression was detectable in normal skin and increased in all cSCCs tested. CARD11 mRNA levels were comparable with CARD14 in normal skin and CARD11 mRNA was increased in cSCC. In addition, we identified CARD11 mutations in peritumoral and sun-exposed skin, suggesting that CARD11-mediated alterations in NF-κB signaling may be an early event in the development of cSCC.

We show that suppression of the spliceosome has potential for the treatment of cutaneous squamous cell carcinoma (cSCC). The small-molecule inhibitors of the spliceosome at the most advanced stage of development target the splicing factor SF3B1/SF3b155. The majority of cSCC cell lines are more sensitive than normal skin cells to death induced by the SF3B1 inhibitor pladienolide B. Knockdown of SF3B1 and a range of other splicing factors with diverse roles in the spliceosome can also selectively kill cSCC cells. We demonstrate that endogenous c-MYC participates in conferring sensitivity to spliceosome inhibition. c-MYC expression is elevated in cSCC lines and its knockdown reduces alterations in mRNA splicing and attenuates cell death caused by interference with the spliceosome. In addition, this study provides further support for a key role of the p53 pathway in the response to spliceosome disruption. SF3B1 inhibition causes wild-type p53 upregulation associated with altered mRNA splicing and reduced protein expression of both principal p53 negative regulators MDMX/MDM4 and MDM2. We observed that wild-type p53 can promote pladienolide B-induced death in tumour cells. However, p53 is commonly inactivated by mutation in cSCCs and p53 participates in killing normal skin cells at high concentrations of pladienolide B. This may limit the therapeutic window of SF3B1 inhibitors for cSCC. We provide evidence that, while suppression of SF3B1 has promise for treating cSCCs with mutant p53, inhibitors which target the spliceosome through SF3B1-independent mechanisms could have greater cSCC selectivity as a consequence of reduced p53 upregulation in normal cells.

Proteasome inhibitors have distinct properties and the biochemical consequences of suppressing ubiquitin E1 enzymes and the proteasome differ. We compared the effects of the proteasome inhibitors bortezomib, ixazomib and carfilzomib and the ubiquitin E1 enzyme inhibitor MLN7243/TAK-243 on cell viability and cell death in normal keratinocytes and cutaneous squamous cell carcinoma (cSCC) cell lines. The effects of both a pulse of treatment and more extended incubation were investigated. This is relevant to directly-delivered therapy (topical treatment/intratumoral injection) where the time of exposure can be controlled and a short exposure may better reflect systemically-delivered inhibitor pharmacokinetics. These agents can selectively kill cSCC cells but there are variations in the pattern of cSCC cell line sensitivity/resistance. Variations in the responses to proteasome inhibitors are associated with differences in the specificity of the inhibitors for the three proteolytic activities of the proteasome. There is greater selectivity for killing cSCC cells compared to normal keratinocytes with a pulse of proteasome inhibitor treatment than with a more extended exposure. We provide evidence that c-MYC-dependent NOXA upregulation confers susceptibility to a short incubation with proteasome inhibitors by priming cSCC cells for rapid BAK-dependent death. We observed that bortezomib-resistant cSCC cells can be sensitive to MLN7243-induced death. Low expression of the ubiquitin E1 UBA1/UBE1 participates in conferring susceptibility to MLN7243 by increasing sensitivity to MLN7243-mediated attenuation of ubiquitination. This study supports further investigation of the potential of proteasome and ubiquitin E1 inhibition for cSCC therapy. Direct delivery of inhibitors could facilitate adequate exposure of skin cancers.

A 22-year-old woman presented with recurrent non-ulcerating skin nodules overlying the great saphenous vein on the anteromedial lower legs. Histology showed a granulomatous phlebitis, and polymerase chain reaction performed on lesional skin detected DNA specific for Mycobacterium tuberculosis. The lesions resolved with anti-tuberculous therapy. This case may be a further example of nodular granulomatous phlebitis, a phlebitic tuberculid.

Transcriptional silencing of tissue factor pathway inhibitor 2 (TFPI2) occurs in several human tumors including melanoma. We investigated methylated TFPI2 as a biomarker of metastatic melanoma using qRT–PCR to assess TFPI2 expression and pyrosequencing to analyze CpG island methylation in malignant melanoma cell lines, in benign nevi, in 112 primary and metastatic melanomas, and in serum from 6 healthy individuals and 35 patients: 20 patients with primary and 15 patients with metastatic melanoma. The TFPI2 CpG island is unmethylated in nevi but methylation is associated with metastatic melanoma. Circulating methylated TFPI2 DNA is undetectable in sera from healthy individuals and detectable in sera from patients with primary and metastatic melanomas, but the presence of methylated TFPI2 DNA in serum is strongly associated with metastatic disease (P

Solid tumors are typically considered to arise from the accumulation of mutations within either stem or differentiated cells and to evolve over several years. However, melanoma patients treated with inhibitors of oncogenic BRAF frequently present with keratoacanthomas and/or cutaneous squamous cell carcinoma (cSCC) within weeks of treatment, possibly driven by paradoxical RAS/RAF MAPK pathway activation. Here, we identify frequent HRAS, TGFβR1 and TGFβR2 mutations in skin lesions from vemurafenib treated patients. Analysis of 98 human sporadic cSCC tumor samples and 21 cSCC cell lines revealed mutation of TGFβ receptors in 42% of samples and activating RAS mutations in 9% of samples. Functional analysis indicates that TGFβ receptor mutations frequently result in loss of canonical signaling. Analysis of normal human skin revealed localised TGFβ signaling in hair follicle bulge stem cells. In murine skin autocrine TGFβ signaling was highly localised to Lgr5+ve stem cells. We modelled hyperactivation of the MAPK pathway (through knockin of BRafV600E or KRASG12D) and the consequences of TGFβ signalling ablation (through the deletion of Tgfβr1) in Lgr5+ve cells. Whist BRaf or KRAS activation alone did not lead to cancer, homozygous deletion of Tgfβr1 enabled rapid cSCC development. Taken together, our results indicate that Lgr5+ve stem cells can act as the cell of origin for cSCC and that hyperactivation of the RAS-RAF-MAPK pathway, coupled with loss of TGFβ signalling, are driving events of skin tumorigenesis. Citation Format: Patrizia Cammareri, Aidan M. Rose, David F. Vincent, Silvana Libertini, Rachel A. Ridgway, Dimitris Athineos, Philip Coates, Angela McHugh, Celine Pourreyron, Jonas Larsson, Lindsay C. Spender, Gopal Sapkota, Karin Purdie, Charlotte Proby, Catherine A. Harwood, Irene M. Leigh, Hans Clevers, Nicholas Barker, Stefan Karlsson, Catrin Pritchard, Richard Marais, Andrew P. South, Owen J. Sansom, Gareth J. Inman. Frequent loss of function mutations in TGFβR1 and TGFβR2 identify hair follicle bulge stem cells as the cell of origin for cutaneous squamous cell carcinoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1506. doi:10.1158/1538-7445.AM2015-1506

The development of new technology within biological sciences has resulted in a number of real-time PCR instruments that have become essential tools within molecular biology. This equipment has facilitated high throughput analysis of samples and optimal information gathering of completed PCR reactions for example estimating the copy number of a gene of interest that is inserted into particular genomes. Real-time PCR instruments frequently come with optional filter sets, e.g. the ALEXA filter set which has parameters in common with excitation and emission wavelengths of sodium methyl umbelliferone (NaMU) widely used in beta-glucuronidase reporter gene assays. Using these filter sets it has been possible to quantify and measure gus A activity of Ulmus procera SR4 in real-time removing the necessity for aliquots of reactions to be stopped by pipetting into carbonate buffer for each time point. The introduction of real-time GUS analysis leads to faster, more accurate and reproducible assays with reduced potential for pipetting errors, requires fewer manipulations and encourages high throughput analysis of inter-individual gene expression variation.

e11553 Background: Ecto-5-prime-nucleotidase (NT5E; CD73) catalyzes the conversion of purine 5-prime mononucleotides to nucleosides, the preferred substrate being AMP. Deficiency of NT5 occurs in a variety of immunodeficiency diseases and some studies have associated over-expression of NT5E with clinically aggressive neoplastic disease. Here we describe transcriptional down-regulation of the NT5E gene in breast cancer and show that this is associated with aberrant methylation in the CpG island located in its 5’ regulatory sequences. Methods: Methylation in the NT5E CpG island was analysed by methylation specific PCR (MSP) and quantitative pyrosequencing in a panel of 10 breast carcinoma cell lines and two independent clinical series of breast carcinomas, comprising 80 and 140 cases respectively and 17 brain metastatic breast cancer lesions. The breast carcinomas were predominantly invasive ductal carcinomas, untreated at the time of surgery and randomly selected from our clinical practice. Expression was ...