Vorinostat synergises with capecitabine through upregulation of thymidine phosphorylase.
BACKGROUND
Potentiation of anticancer activity of capecitabine is required to improve its therapeutic index. In colorectal cancer (CRC) cells, we evaluated whether the histone deacetylase-inhibitor vorinostat may induce synergistic antitumour effects in combination with capecitabine by modulating the expression of thymidine phosphorylase (TP), a key enzyme in the conversion of capecitabine to 5-florouracil (5-FU), and thymidylate synthase (TS), the target of 5-FU.


METHODS
Expression of TP and TS was measured by real-time PCR, western blotting and immunohistochemistry. Knockdown of TP was performed by specific small interfering RNA. Antitumour activity of vorinostat was assessed in vitro in combination with the capecitabine active metabolite deoxy-5-fluorouridine (5'-DFUR) according to the Chou and Talay method and by evaluating apoptosis as well as in xenografts-bearing nude mice in combination with capecitabine.


RESULTS
Vorinostat induced both in vitro and in vivo upregulation of TP as well as downregulation of TS in cancer cells, but not in ex vivo treated peripheral blood lymphocytes. Combined treatment with vorinostat and 5'-DFUR resulted in a synergistic antiproliferative effect and increased apoptotic cell death in vitro. This latter effect was impaired in cells where TP was knocked. In vivo, vorinostat plus capecitabine potently inhibited tumour growth, increased apoptosis and prolonged survival compared with control or single-agent treatments.


CONCLUSIONS
Overall, this study suggests that the combination of vorinostat and capecitabine is an innovative antitumour strategy and warrants further clinical evaluation for the treatment of CRC.
Experimental Pharmacology Unit, Department of Research, Istituto Nazionale Tumori, National Cancer Institute Fondazione G, Via M Semmola, Pascale, Napoli 80131, Italy.
E
E
Di Gennaro
G
G
Piro
M I
MI
Chianese
R
R
Franco
A
A
Di Cintio
T
T
Moccia
A
A
Luciano
I
I
de Ruggiero
F
F
Bruzzese
A
A
Avallone
C
C
Arra
A
A
Budillon
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D000069287:Capecitabine; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D003841:Deoxycytidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D004357:Drug Synergism; D005260:Female; D005467:Floxuridine / Q000494:pharmacology; D005472:Fluorouracil / Q000031:analogs & derivatives* / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D056572:Histone Deacetylase Inhibitors / Q000494:pharmacology*; D006877:Hydroxamic Acids / Q000494:pharmacology*; D051379:Mice; D008807:Mice, Inbred BALB C; D013939:Thymidine Phosphorylase / Q000235:genetics*; D013940:Thymidylate Synthase / Q000235:genetics; D015854:Up-Regulation; D000077337:Vorinostat; D023041:Xenograft Model Antitumor Assays
D000970:Antineoplastic Agents; D056572:Histone Deacetylase Inhibitors; D006877:Hydroxamic Acids; D005467:Floxuridine; D003841:Deoxycytidine; D000077337:Vorinostat; D000069287:Capecitabine; D013940:Thymidylate Synthase; D013939:Thymidine Phosphorylase; D005472:Fluorouracil; C025034:doxifluridine