Characterization of human mesothelin transcripts in ovarian and pancreatic cancer.
BACKGROUND
Mesothelin is an attractive target for cancer immunotherapy due to its restricted expression in normal tissues and high level expression in several tumor types including ovarian and pancreatic adenocarcinomas. Three mesothelin transcript variants have been reported, but their relative expression in normal tissues and tumors has been poorly characterized. The goal of the present study was to clarify which mesothelin transcript variants are commonly expressed in human tumors.


METHODS
Human genomic and EST nucleotide sequences in the public databases were used to evaluate sequences reported for the three mesothelin transcript variants in silico. Subsequently, RNA samples from normal ovary, ovarian and pancreatic carcinoma cell lines, and primary ovarian tumors were analyzed by reverse transcription-polymerase chain reaction (RT-PCR) and nucleotide sequencing to directly identify expressed transcripts.


RESULTS
In silico comparisons of genomic DNA sequences with available EST sequences supported expression of mesothelin transcript variants 1 and 3, but there were no sequence matches for transcript variant 2. Newly-derived nucleotide sequences of RT-PCR products from tissues and cell lines corresponded to mesothelin transcript variant 1. Mesothelin transcript variant 2 was not detected. Transcript variant 3 was observed as a small percentage of total mesothelin amplification products from all studied cell lines and tissues. Fractionation of nuclear and cytoplasmic RNA indicated that variant 3 was present primarily in the nuclear fraction. Thus, mesothelin transcript variant 3 may represent incompletely processed hnRNA.


CONCLUSIONS
Mesothelin transcript variant 1 represents the predominant mature mRNA species expressed by both normal and tumor cells. This conclusion should be important for future development of cancer immunotherapies, diagnostic tests, and gene microarray studies targeting mesothelin.
Muminova
Zhanat E
ZE
Division of Hematology and Oncology, Department of Medicine, and the Comprehensive Cancer Center, University of Alabama at Birmingham, Birmingham, AL 35294-3300, USA. zhana@uab.edu
Strong
Theresa V
TV
Shaw
Denise R
DR
D000951:Antigens, Neoplasm / Q000032:analysis*; D014408:Biomarkers, Tumor / Q000032:analysis; D018269:Carcinoma, Endometrioid / Q000737:chemistry; D045744:Cell Line, Tumor; D018283:Cystadenocarcinoma, Papillary / Q000737:chemistry; D005260:Female; D058851:GPI-Linked Proteins; D006801:Humans; D008297:Male; D008562:Membrane Glycoproteins / Q000032:analysis*; D000090204:Mesothelin; D010051:Ovarian Neoplasms / Q000737:chemistry*; D010179:Pancreas / Q000737:chemistry*; D010190:Pancreatic Neoplasms / Q000737:chemistry*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA
D000951:Antigens, Neoplasm; D014408:Biomarkers, Tumor; D058851:GPI-Linked Proteins; D008562:Membrane Glycoproteins; D000090204:Mesothelin