Epidermal growth factor potentiates in vitro metastatic behaviour of human prostate cancer PC-3M cells: involvement of voltage-gated sodium channel.
BACKGROUND
Although a high level of functional voltage-gated sodium channel (VGSC) expression has been found in strongly metastatic human and rat prostate cancer (PCa) cells, the mechanism(s) responsible for the upregulation is unknown. The concentration of epidermal growth factor (EGF), a modulator of ion channels, in the body is highest in prostatic fluid. Thus, EGF could be involved in the VGSC upregulation in PCa. The effects of EGF on VGSC expression in the highly metastatic human PCa PC-3M cell line, which was shown previously to express both functional VGSCs and EGF receptors, were investigated. A quantitative approach, from gene level to cell behaviour, was used. mRNA levels were determined by real-time PCR. Protein expression was studied by Western blots and immunocytochemistry and digital image analysis. Functional assays involved measurements of transverse migration, endocytic membrane activity and Matrigel invasion.


RESULTS
Exogenous EGF enhanced the cells' in vitro metastatic behaviours (migration, endocytosis and invasion). Endogenous EGF had a similar involvement. EGF increased VGSC Nav1.7 (predominant isoform in PCa) mRNA and protein expressions. Co-application of the highly specific VGSC blocker tetrodotoxin (TTX) suppressed the effect of EGF on all three metastatic cell behaviours studied.


CONCLUSIONS
1) EGF has a major involvement in the upregulation of functional VGSC expression in human PCa PC-3M cells. (2) VGSC activity has a significant intermediary role in potentiating effect of EGF in human PCa.
Uysal-Onganer
Pinar
P
Neuroscience Solutions to Cancer Research Group, Division of Cell and Molecular Biology, Sir Alexander Fleming Building, Imperial College London, South Kensington Campus, London SW7 2AZ, UK. p.onganer@imperial.ac.uk
Djamgoz
Mustafa Ba
MB
D045744:Cell Line, Tumor; D002465:Cell Movement; D004705:Endocytosis; D004815:Epidermal Growth Factor / Q000378:metabolism; D066246:ErbB Receptors / Q000378:metabolism; D006801:Humans; D008297:Male; D018613:Microscopy, Confocal; D062556:NAV1.7 Voltage-Gated Sodium Channel; D009361:Neoplasm Invasiveness; D009362:Neoplasm Metastasis; D011471:Prostatic Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology*; D012333:RNA, Messenger / Q000378:metabolism; D015222:Sodium Channels / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology; D013779:Tetrodotoxin / Q000494:pharmacology
D062556:NAV1.7 Voltage-Gated Sodium Channel; D012333:RNA, Messenger; C486866:SCN9A protein, human; D015222:Sodium Channels; D013779:Tetrodotoxin; D004815:Epidermal Growth Factor; D066246:ErbB Receptors