Defects in cell growth regulation by C18:0-ceramide and longevity assurance gene 1 in human head and neck squamous cell carcinomas.
In this study, endogenous long chain ceramides were measured in 32 human head and neck squamous cell carcinoma (HNSCC) and 10 nonsquamous head and neck carcinoma tumor tissues, as compared with adjacent noncancerous tissues, by liquid chromatography/mass spectroscopy. Interestingly, only one specific ceramide, C(18:0)-ceramide, was selectively down-regulated in the majority of HNSCC tumor tissues. On the other hand, in nonsquamous tumor tissues, this selectivity for C18-ceramide was not detected. These data suggested the hypotheses that decreased levels of C18-ceramide might impart a growth advantage to HNSCC cells and that increased generation of C18-ceramide may be involved in the inhibition of growth. These roles were examined by reconstitution of C18-ceramide at physiologically relevant concentrations in UM-SCC-22A cells (squamous cell carcinoma of hypopharynx) via overexpression of mammalian upstream regulator of growth and differentiation factor 1 (mUOG1), a mouse homologue of longevity assurance gene 1 (mLAG1), which has been shown to specifically induce the generation of C18-ceramide. Liquid chromatography/mass spectroscopy analysis showed that overexpression of the mLAG1/mUOG1 resulted in increased levels of only C(18:0)-ceramide by approximately 2-fold, i.e. concentrations similar to those of normal head and neck tissues. Importantly, increased generation of C18-ceramide by mLAG1/mUOG1 inhibited cell growth (approximately 70-80%), which mechanistically involved the modulation of telomerase activity and induction of apoptotic cell death by mitochondrial dysfunction. In conclusion, this study demonstrates, for the first time, a biological role for LAG1 and C18-ceramide in the regulation of growth of HNSCC.
Department of Biochemistry, Ralph H. Johnson Veterans Affairs Medical Center, Medical University of South Carolina, Charleston, South Carolina 29425, USA.
Serap
S
Koybasi
Can E
CE
Senkal
Kamala
K
Sundararaj
Stefka
S
Spassieva
Jacek
J
Bielawski
Walid
W
Osta
Terry A
TA
Day
James C
JC
Jiang
S Michal
SM
Jazwinski
Yusuf A
YA
Hannun
Lina M
LM
Obeid
Besim
B
Ogretmen
D000818:Animals; D017209:Apoptosis; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy*; D002455:Cell Division; D045744:Cell Line, Tumor; D002518:Ceramides / Q000737:chemistry* / Q000378:metabolism; D002853:Chromatography, Liquid; D004396:Coloring Agents / Q000494:pharmacology; D018076:DNA, Complementary / Q000378:metabolism; D006258:Head and Neck Neoplasms / Q000188:drug therapy*; D006801:Humans; D013058:Mass Spectrometry; D008564:Membrane Potentials; D008565:Membrane Proteins / Q000096:biosynthesis*; D051379:Mice; D008928:Mitochondria / Q000378:metabolism; D011506:Proteins / Q000378:metabolism / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D029701:Saccharomyces cerevisiae Proteins / Q000096:biosynthesis*; D051049:Sphingosine N-Acyltransferase; D019098:Telomerase / Q000378:metabolism; D013778:Tetrazolium Salts / Q000494:pharmacology; D013844:Thiazoles / Q000494:pharmacology; D014343:Trypan Blue / Q000494:pharmacology
D002518:Ceramides; D004396:Coloring Agents; D018076:DNA, Complementary; C087436:LAG1 protein, S cerevisiae; D008565:Membrane Proteins; C466778:N-stearoylsphinganine; D011506:Proteins; D012333:RNA, Messenger; D029701:Saccharomyces cerevisiae Proteins; D013778:Tetrazolium Salts; D013844:Thiazoles; C493790:CERS1 protein, human; D051049:Sphingosine N-Acyltransferase; D019098:Telomerase; C022616:thiazolyl blue; D014343:Trypan Blue