Transformation of human urothelial cells (UROtsa) by as and cd induces the expression of keratin 6a.
BACKGROUND
Cadmium and arsenite can directly and malignantly transform the UROtsa cell line. The tumor heterotransplants produced from these transformed cells have histologic features consistent with human bladder cancer. Previous microarray analysis of total RNA from the parental and transformed cells suggested that keratin 6a was overexpressed as a result of cell transformation.


OBJECTIVE
Our goals were to verify overexpression of keratin 6a in Cd(2+)- and As(3+)-transformed UROtsa cells, the corresponding tumor heterotransplants, and human bladder cancer biopsy specimens and to assess what factors may be involved in keratin 6a overexpression.


METHODS
Expression was assessed with real-time polymerase chain reaction, Western blot analysis, and immunohistochemistry. We used the effect of addition and deletion of potential growth factors in the cell culture growth medium to assess possible pathways used in keratin 6a overexpression.


RESULTS
Cd(2+)- and As(3+)-transformed cells grown in serum-containing growth medium, as well as the derived tumor heterotransplants, overexpressed keratin 6a mRNA and protein compared with UROtsa cells grown in serum-containing growth medium. Immunostaining of keratin 6a in tumor heterotransplants showed focal staining of the tumor cells that was localized to the cytoplasm. Focal immunostaining of keratin 6a was also found in some but not all archival patient specimens of high-grade bladder cancer, confirming translation of the results to human bladder cancer. Studies on growth factor deletion and addition indicated that the level of keratin 6a expression was regulated by the presence of both insulin and epidermal growth factor (EGF). In contrast, growth factors had no effect on the elevated levels of keratin 6a expression found in transformed UROtsa cells.


CONCLUSIONS
Our present studies suggest that keratin 6a expression may be a biomarker for malignant urothelial cells that possess an activated EGF and or insulin growth factor pathway.
Somji
Seema
S
Department of Pathology, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, North Dakota 58202, USA.
Bathula
Chandra S
CS
Zhou
Xu Dong
XD
Sens
Mary Ann
MA
Sens
Donald A
DA
Garrett
Scott H
SH
D000818:Animals; D018053:Arsenites / Q000633:toxicity*; D014408:Biomarkers, Tumor / Q000096:biosynthesis; D015153:Blotting, Western; D002104:Cadmium / Q000633:toxicity*; D002460:Cell Line; D002471:Cell Transformation, Neoplastic / Q000139:chemically induced / Q000378:metabolism* / Q000473:pathology; D003470:Culture Media; D004815:Epidermal Growth Factor / Q000494:pharmacology; D006801:Humans; D007150:Immunohistochemistry; D007328:Insulin / Q000494:pharmacology; D053553:Keratin-6 / Q000096:biosynthesis*; D051379:Mice; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000096:biosynthesis; D014183:Transplantation, Heterologous; D001749:Urinary Bladder Neoplasms / Q000378:metabolism* / Q000473:pathology; D019459:Urothelium / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology
D018053:Arsenites; D014408:Biomarkers, Tumor; D003470:Culture Media; D007328:Insulin; D053553:Keratin-6; D012333:RNA, Messenger; D002104:Cadmium; D004815:Epidermal Growth Factor; C015001:arsenite