Novel insights into the expression of CGB1 & 2 genes by epithelial cancer cell lines secreting ectopic free hCGβ.
BACKGROUND
Ectopic secretion of human chorionic gonadotrophin free beta (hCGβ) by epithelial cancer is associated with aggressive tumors which more readily metastasize, possibly by acting as an autocrine anti-apoptotic agent. hCGβ is encoded by six homologous CGB genes, with poorly-understood variable transcriptionally active expression profiles; CGB1 and CGB2 have always been considered pseudogenes. However, transcripts from CGB1 and -2 can be detected in placental, testicular and pituitary tissues. The expression and function of these genes in cancer is less well-known.


METHODS
Expression profiles of CGB genes in epithelial cancer cells by quantitative polymerase chain reaction (qPCR) were explored, along with the consequence of specific siRNA silencing of CGB1 and 2. Immunohistochemical and immunoassay techniques were used to detect the translation and secretion of hCGβ in these cells.


RESULTS
CGB1 and -2 gene transcripts were only detected in cells which secreted hCGβ. siRNA-mediated silencing of CGB1 and -2 transcripts significantly reduced secreted protein in concordance with a reduction in cell survival to a greater degree than that of other CGB genes.


CONCLUSIONS
CGB genes 1 and 2, previously considered as pseudogenes, are notably expressed by epithelial cancer cell lines. The transcription of these genes, but not other CGB genes, correlates with a functionally expressed protein and propensity for cancer growth.
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Beata B
BB
Burczynska
Latifa
L
Kobrouly
Stephen A
SA
Butler
Mahmoud
M
Naase
Ray K
RK
Iles
D045744:Cell Line, Tumor; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000096:biosynthesis* / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D009375:Neoplasms, Glandular and Epithelial / Q000235:genetics* / Q000378:metabolism*; D020033:Protein Isoforms / Q000235:genetics; D034741:RNA, Small Interfering; D060888:Real-Time Polymerase Chain Reaction; D059467:Transcriptome
D018997:Chorionic Gonadotropin, beta Subunit, Human; D020033:Protein Isoforms; D034741:RNA, Small Interfering
CGB; CGB spliced variants; CGB type I and type II; CGB1/2 pseudogenes; carcinoma; epithelial cancer; hCG; hCGβ secretion; siRNA silencing