Genomic organization, incidence, and localization of the SPAN-x family of cancer-testis antigens in melanoma tumors and cell lines.
OBJECTIVE
Members of the SPAN-X (sperm protein associated with the nucleus mapped to the X chromosome) family of cancer-testis antigens are promising targets for tumor immunotherapy because they are normally expressed exclusively during spermiogenesis on the adluminal side of the blood-testis barrier, an immune privileged compartment.


RESULTS
This study analyzed the human SPANX genomic organization, as well as SPAN-X mRNA and protein expression in somatic and cancer cells. The SPANX family consists of five genes, one of which is duplicated, all located in a gene cluster at Xq27.1. From the centromere, the arrangement of the five SPANX genes mapped on one contiguous sequence is SPANXB, -C, -A1, -A2, and -D. Reverse transcription-PCR analyses demonstrated expression of SPAN-X mRNA in melanoma and ovarian cell lines, and virtual Northern analysis established SPANX gene expression in numerous cancer cell lines. Immunoblot analysis using polyclonal antisera raised against recombinant SPAN-X confirmed the translation of SPAN-X proteins in melanoma and ovarian tumor cell lines. The immunoreactive proteins migrated between M(r) 15,000 and M(r) 20,000 similar to those observed in spermatozoa. Immunoperoxidase labeling of melanoma cells and tissue sections demonstrated SPAN-X protein localization in the nucleus, cytoplasm, or both. Ultrastructurally, in melanoma cells with nuclear SPAN-X, the protein was associated with the nuclear envelope, a localization similar to that observed in human spermatids and spermatozoa. Significantly, the incidence of SPAN-X-positive immunostaining was greatest in the more aggressive skin tumors, particularly in distant, nonlymphatic metastatic melanomas.


CONCLUSIONS
The data herein suggest that the SPAN-X protein may be a useful target in cancer immunotherapy.
Westbrook
V Anne
VA
Department of Cell Biology, Center for Research in Contraceptive and Reproductive Health, University of Virginia, Charlottesville, Virginia, USA.
Schoppee
Pamela D
PD
Diekman
Alan B
AB
Klotz
Kenneth L
KL
Allietta
Margaretta
M
Hogan
Kevin T
KT
Slingluff
Craig L
CL
Patterson
James W
JW
Frierson
Henry F
HF
Irvin
William P
WP
Flickinger
Charles J
CJ
Coppola
Michael A
MA
Herr
John C
JC
D000595:Amino Acid Sequence; D000951:Antigens, Neoplasm / Q000235:genetics* / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008545:Melanoma / Q000235:genetics* / Q000473:pathology; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism; D010051:Ovarian Neoplasms / Q000235:genetics / Q000473:pathology; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D013087:Spermatids / Q000378:metabolism / Q000473:pathology; D014407:Tumor Cells, Cultured
D000951:Antigens, Neoplasm; D009687:Nuclear Proteins; D012333:RNA, Messenger; C414403:SPANXA1 protein, human; C521014:SPANXA2 protein, human; C521016:SPANXD protein, human