OBJECTIVE To investigate protein kinase CK2 (CK2) expression in squamous cell carcinoma (SCC) of cats and to examine effects of CK2 downregulation on in vitro apoptosis and viability in SCC. SAMPLE Biopsy specimens of oral mucosa and testis and blood samples from clinically normal cats, biopsy specimens of oral SCC from cats, and feline SCC (SCCF1) and mammary gland carcinoma (K12) cell lines. PROCEDURES Immunohistochemical labeling for CK2α was performed on biopsy specimens. Sequences of the CK2α subunit gene and CK2α′ subunit gene in feline blood and feline cancer cell lines were determined by use of PCR and reverse-transcription PCR assays followed by direct Sanger sequencing. Specific small interfering RNAs (siRNAs) were developed for feline CK2α and CK2α′. The SCCF1 cells were treated with siRNA and assessed 72 hours later for CK2α and CK2α′ expression and markers of apoptosis (via western blot analysis) and for viability (via 3-[4,5-dimethylthiazol-2-yl]-5-[3-carboxymethoxyphenyl]-2-[4-sulfophenyl]-2H-tetrazolium assays). RESULTS CK2α was expressed in all feline oral mucosa samples and 7 of 8 oral SCC samples. Expression of CK2α and CK2α′ was successfully downregulated in SCCF1 cells by use of siRNAs, which resulted in decreased viability and induction of apoptosis. CONCLUSIONS AND CLINICAL RELEVANCE In this study, CK2 appeared to be a promising therapeutic target for SCCs of cats. A possible treatment strategy for SCCs of cats would be RNA interference that targets CK2.
Bibliographical noteFunding Information:
Supported by the National Center for Advancing Translational Sciences of the National Institutes of Health (award No. UL1TR000114); the University of Minnesota Clinical and Trans- lational Sciences (award No. 1UL1 RR033183-01); merit review research funds from the Department of Veterans Affairs (grant No. 1IO1B001731 awarded to Dr. Ahmed); the National Cancer Institute, National Institutes of Health, Department of Health and Human Services (grant No. CA150182 awarded to Dr. Ahmed and grant No. CA158730 awarded to Dr. Kren); the National Institute of Diabetes and Digestive and Kidney Disease (grant No. DK067436-05 awarded to Dr. Kren); the Comprehensive Cancer Center Support Grant to the Masonic Cancer Center, University of Minnesota (No. P30 CA077598); and the Animal Cancer Care and Research Program of the University of Minnesota, which funded a fellowship that partially supported Dr. Cannon and also provided additional funding for this study. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. Presented in part as an abstract at the American College of Veterinary Internal Medicine Forum, Seattle, June 2013. The authors thank Omar Cespedes-Gomez for assistance with the experiments, Paula Overn for assistance with immunohistochemical analysis, and Robert Schmitt for assistance with sample collection.
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