AZGP1 autoantibody predicts survival and histone deacetylase inhibitors increase expression in lung adenocarcinoma.
BACKGROUND
The importance of alpha-2-glycoprotein 1, zinc (AZGP1) in lung adenocarcinoma (AD) remains largely unknown. Analysis of serum autoantibodies to tumor antigens combined with gene expression profiling of primary tumors may provide insight into the mechanisms underlying lung carcinogenesis and identify new AD biomarkers.


METHODS
T7 phage cDNA libraries were used to identify AZGP1 autoantibodies in the serum of 473 patients (192 ADs, 192 matched controls, and 89 additional ADs for confirmation of findings). AZGP1 mRNA expression was examined in 86 ADs and 10 control lung tissue samples using oligonucleotide microarrays. AZGP1 protein expression was studied in 230 tissue samples (222 ADs; 8 controls) with immunohistochemistry. Kaplan-Meier analyses were used to correlate circulating autoantibody and tissue mRNA production with survival. AD cell lines A549 and SKLU1 were treated with 5-aza-2;-deoxycytidine (5-AZA) and trichostatin A (TSA) to examine the role of promoter methylation and histone deacetylation in the expression of AZGP1. Real-time polymerase chain reaction was used to quantify the effects of treatment.


RESULTS
In patients with AD, AZGP1 autoantibodies were observed in 40% of serum samples. Autoantibody production correlated with improved overall 5-year survival (p = 0.002) and improved survival in those with stage I to II disease (p = 0.008). A verification analysis was performed for the survival benefit and found similar results with p values of 0.02 and 0.036, respectively. Although abundant mRNA expression was found in a subset of tumors, mRNA expression did not correlate with prognosis. In normal lung, AZGP1 mRNA and protein expression were low or absent, whereas in AD they were highly expressed in 31.3% and 42.8% of samples, respectively. To determine whether AZGP1 expression in this subset of tumors might be affected by epigenetic mechanisms, low AZGP1-expressing A549 and SKLU1 AD cell lines were treated with TSA and 5-AZA. A 713-fold and 169-fold increase in mRNA expression were noted on treatment with TSA, respectively. Treatment with 5-AZA had minimal effect on AZGP1 mRNA expression.


CONCLUSIONS
The presence of AZGP1 serum autoantibody may be used as a prognostic marker in patients with AD. Furthermore, up-regulation of AZGP1 mRNA in AD may be affected by chromatin remodeling by means of histone acetylation.
Albertus
Daniel L
DL
Department of Surgery, University of Michigan Medical School, Ann Arbor, Michigan, USA.
Seder
Christopher W
CW
Chen
Guoan
G
Wang
Xiaoju
X
Hartojo
Wibisono
W
Lin
Lin
L
Silvers
Amy
A
Thomas
Daffyd G
DG
Giordano
Thomas J
TJ
Chang
Andrew C
AC
Orringer
Mark B
MB
Bigbee
William L
WL
Chinnaiyan
Arul M
AM
Beer
David G
DG
D000107:Acetylation; D000230:Adenocarcinoma / Q000188:drug therapy / Q000235:genetics / Q000401:mortality*; D054392:Adipokines; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001323:Autoantibodies / Q000097:blood*; D001374:Azacitidine / Q000627:therapeutic use; D014408:Biomarkers, Tumor; D002352:Carrier Proteins / Q000235:genetics / Q000276:immunology*; D016022:Case-Control Studies; D004791:Enzyme Inhibitors / Q000627:therapeutic use*; D005260:Female; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D006023:Glycoproteins / Q000235:genetics / Q000276:immunology*; D051548:Histone Acetyltransferases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D056572:Histone Deacetylase Inhibitors; D006655:Histone Deacetylases / Q000235:genetics / Q000378:metabolism; D006801:Humans; D006877:Hydroxamic Acids / Q000627:therapeutic use; D007124:Immunoenzyme Techniques; D008175:Lung Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000401:mortality*; D008297:Male; D008875:Middle Aged; D020411:Oligonucleotide Array Sequence Analysis; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015996:Survival Rate; D014407:Tumor Cells, Cultured; D000090203:Zn-Alpha-2-Glycoprotein
D054392:Adipokines; D001323:Autoantibodies; D001374:Azacitidine; D014408:Biomarkers, Tumor; D002352:Carrier Proteins; D004791:Enzyme Inhibitors; D006023:Glycoproteins; D051548:Histone Acetyltransferases; D056572:Histone Deacetylase Inhibitors; D006655:Histone Deacetylases; D006877:Hydroxamic Acids; D012333:RNA, Messenger; C488891:AZGP1 protein, human; D000090203:Zn-Alpha-2-Glycoprotein; C012589:trichostatin A; C110880:histone acetyltransferase type B complex