Targeted inhibition of inducible nitric oxide synthase inhibits growth of human melanoma in vivo and synergizes with chemotherapy.
OBJECTIVE
Aberrant expression of inflammatory molecules, such as inducible nitric oxide (NO) synthase (iNOS), has been linked to cancer, suggesting that their inhibition is a rational therapeutic approach. Whereas iNOS expression in melanoma and other cancers is associated with poor clinical prognosis, in vitro and in vivo studies suggest that iNOS and NO can have both protumor and antitumor effects. We tested the hypothesis that targeted iNOS inhibition would interfere with human melanoma growth and survival in vivo in a preclinical model.


METHODS
We used an immunodeficient non-obese diabetic/severe combined immunodeficient xenograft model to test the susceptibility of two different human melanoma lines to the orally-given iNOS-selective small molecule antagonist N(6)-(1-iminoethyl)-l-lysine-dihydrochloride (L-nil) with and without cytotoxic cisplatin chemotherapy.


RESULTS
L-nil significantly inhibited melanoma growth and extended the survival of tumor-bearing mice. L-nil treatment decreased the density of CD31+ microvessels and increased the number of apoptotic cells in tumor xenografts. Proteomic analysis of melanoma xenografts with reverse-phase protein array identified alterations in the expression of multiple cell signaling and survival genes after L-nil treatment. The canonical antiapoptotic protein Bcl-2 was downregulated in vivo and in vitro after L-nil treatment, which was associated with increased susceptibility to cisplatin-mediated tumor death. Consistent with this observation, combination therapy with L-nil plus cisplatin in vivo was more effective than either drug alone, without increased toxicity.


CONCLUSIONS
These data support the hypothesis that iNOS and iNOS-derived NO support tumor growth in vivo and provide convincing preclinical validation of targeted iNOS inhibition as therapy for solid tumors.
Sikora
Andrew G
AG
Department of Melanoma Medical Oncology, University of Texas M.D. Anderson Cancer Center, Houston, TX 77030, USA. andrew.sikora@mssm.edu
Gelbard
Alexander
A
Davies
Michael A
MA
Sano
Daisuke
D
Ekmekcioglu
Suhendan
S
Kwon
John
J
Hailemichael
Yared
Y
Jayaraman
Padmini
P
Myers
Jeffrey N
JN
Grimm
Elizabeth A
EA
Overwijk
Willem W
WW
D000818:Animals; D000970:Antineoplastic Agents / Q000627:therapeutic use; D017209:Apoptosis; D015153:Blotting, Western; D002478:Cells, Cultured; D002945:Cisplatin / Q000627:therapeutic use*; D004357:Drug Synergism; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005260:Female; D006801:Humans; D007124:Immunoenzyme Techniques; D008239:Lysine / Q000031:analogs & derivatives* / Q000494:pharmacology; D008545:Melanoma / Q000201:enzymology* / Q000473:pathology*; D051379:Mice; D008810:Mice, Inbred C57BL; D016688:Mice, Inbred NOD; D016513:Mice, SCID; D052247:Nitric Oxide Synthase Type II / Q000037:antagonists & inhibitors* / Q000378:metabolism; D023041:Xenograft Model Antitumor Assays
D000970:Antineoplastic Agents; D004791:Enzyme Inhibitors; C090663:N(6)-(1-iminoethyl)lysine; D052247:Nitric Oxide Synthase Type II; D008239:Lysine; D002945:Cisplatin