Targeting c20orf20 for cutaneous squamous cell carcinoma therapy


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Stephen Watt1,Celine Pourreyron1,John Foerster1,Karin Purdie2,Clare Cole1,John McGrath1,Charlotte Proby1,Irene Leigh1,Andrew South1
1University of Dundee, Dundee, United Kingdom,2University of London, London, United Kingdom

Background

Cutaneous squamous cell carcinoma (cSCC) is the most common human tumour with malignant potential and responsible for greater than 1 in 4 skin cancer deaths in the UK. High risk groups such as immunosupressed patients and those with the genetic condition recessive dystrophic epidermolysis bullosa are burdened with increased cSCC incidence, metastasis and mortality. To this end a specific therapy for cSCC remains an unmet clinical need.

Method

We used integrative mRNA expression profiling followed by high-throughput RNAi screening to reveal genes essential for cSCC cell growth and survival, with cell viability assessed by the MTS assay. An ELISA kit detecting cleaved nucleosomes was used to assay apoptosis and in vivo studies using cSCC xenografts were performed by directly injecting siRNA into the tumour.

Results

By integrating in vitro and in vivo expression profiling comparing SCC with normal skin followed by subtraction of similarly regulated genes in the benign hyperproliferative disease, psoriasis, we have derived a candidate cSCC “driver” gene signature of 22 upregulated and 8 downregulated genes. RNAi-mediated knockdown of the 22 upregulated genes revealed two genes, PLK1 and c20orf20, as potential targets. c20orf20 depletion resulted in a 65% decrease in cSCC viability and a 2.5-fold increase in apoptosis with no effect on normal primary keratinocytes. RNAi treatment of cSCC xenografts resulted in marked reduction in tumour volume after 11 treatments (Control: 409mm3 ±107.5, n=2, vs siRNA: 198mm3 ±51.9, n=3).

Conclusion

We have identified a potentially novel cancer target, c20orf20, which is overexpressed in cSCC keratinocytes and essential for cSCC cell survival as shown by reduced cell viability, increased apoptosis and reduced tumour volume following siRNA-mediated knockdown. We aim to elucidate the mechanism behind c20orf20-dependent cell survival to help design future compound screens, and believe c20orf20 could offer hope as a therapeutic target in cSCC, and potentially, other cancers.