title: Carcinogens induce loss of the primary cilium in human renal proximal tubular epithelial cells independently of effects on the cell cycle.
abstract: The primary cilium is an immotile sensory and signaling organelle found on the majority of mammalian cell types. Of the multitude of roles that the primary cilium performs, perhaps some of the most important include maintenance of differentiation, quiescence, and cellular polarity. Given that the progression of cancer requires disruption of all of these processes, we have investigated the effects of several carcinogens on the primary cilium of the RPTEC/TERT1 human proximal tubular epithelial cell line. Using both scanning electron microscopy and immunofluorescent labeling of the ciliary markers acetylated tubulin and Arl13b, we confirmed that RPTEC/TERT1 cells express primary cilium upon reaching confluence. Treatment with the carcinogens ochratoxin A (OTA) and potassium bromate (KBrO(3)) caused a significant reduction in the number of ciliated cells, while exposure to nifedipine, a noncarcinogenic renal toxin, had no effect on primary cilium expression. Flow cytometric analysis of the effects of all three compounds on the cell cycle revealed that only KBrO(3) resulted in an increase in the proportion of cells entering the cell cycle. Microarray analysis revealed dysregulation of multiple pathways affecting ciliogenesis and ciliary maintenance following OTA and KBrO(3) exposure, which were unaffected by nifedipine exposure. The primary cilium represents a unique physical checkpoint with relevance to carcinogenesis. We have shown that the renal carcinogens OTA and KBrO(3) cause significant deciliation in a model of the proximal tubule. With KBrO(3), this was followed by reentry into the cell cycle; however, deciliation was not found to be associated with reentry into the cell cycle following OTA exposure. Transcriptomic analysis identified dysregulation of Wnt signaling and ciliary trafficking in response to OTA and KBrO(3) exposure.
authors.affiliation: Renal Disease Research Group, School of Biomolecular and Biomedical Science, UCD Conway Institute, University College Dublin, Dublin 4, Ireland.
authors.forename: Robert
authors.initials: R
authors.lastname: Radford
authors.forename: Craig
authors.initials: C
authors.lastname: Slattery
authors.forename: Paul
authors.initials: P
authors.lastname: Jennings
authors.forename: Oliver
authors.initials: O
authors.lastname: Blacque
authors.forename: Oliver
authors.initials: O
authors.lastname: Blaque
authors.forename: Walter
authors.initials: W
authors.lastname: Pfaller
authors.forename: Hans
authors.initials: H
authors.lastname: Gmuender
authors.forename: Joost
authors.initials: J
authors.lastname: Van Delft
authors.forename: Michael P
authors.initials: MP
authors.lastname: Ryan
authors.forename: Tara
authors.initials: T
authors.lastname: McMorrow
mesh_terms: D020727:ADP-Ribosylation Factors / Q000032:analysis; D001959:Bromates / Q000633:toxicity*; D002273:Carcinogens / Q000633:toxicity*; D002453:Cell Cycle / Q000187:drug effects*; D002460:Cell Line; D002923:Cilia / Q000187:drug effects / Q000648:ultrastructure; D004847:Epithelial Cells / Q000187:drug effects / Q000648:ultrastructure; D005455:Fluorescent Antibody Technique; D006801:Humans; D007687:Kidney Tubules, Proximal / Q000187:drug effects* / Q000648:ultrastructure; D009543:Nifedipine / Q000633:toxicity; D009793:Ochratoxins / Q000633:toxicity*; D059467:Transcriptome / Q000187:drug effects; D014404:Tubulin / Q000032:analysis / Q000378:metabolism; D060449:Wnt Signaling Pathway / Q000187:drug effects
chemical_list: D001959:Bromates; D002273:Carcinogens; D009793:Ochratoxins; D014404:Tubulin; C019536:potassium bromate; C025589:ochratoxin A; D020727:ADP-Ribosylation Factors; C530391:ARL13B protein, human; D009543:Nifedipine